╭ serve_ssh_protocol.zig ───────────────────────────────────────╮ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ 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🬐 🬠 🬞🬂🬏 🬟 🬑 🬟 🬑 ╭4b8a0b11..╮ 4b8a0b11.. see-em: 🬋🬋🬋 🬋🬋🬋 🬋 🬋 │files │ commits refs discuss issues new login 🬐 🬠 🬐 🬠 🬑 🬟 🬰 ╰──────────╯ (578) user
╭────╮ ╭ clone ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╮ │http│ ssh │ │ ╰────╯ ╰ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╯
.. embed/ event/ test/ ui/ command.zig diff3.zig event.zig find.zig fork.zig lib.zig main.zig main_wasm.zig patch.zig progress.zig push.zig search.zig search_commit.zig search_thread.zig serve.zig serve_common.zig serve_http.zig serve_ssh.zig ╭─────────────────────────────────╮ │serve_ssh_protocol.zig │ ╰─────────────────────────────────╯ test.zig testnet.zig try.zig ui.zig web.zig
1 //! In-process SSH server: full server side of SSH-2 for haxy's use case. 2 //! 3 //! handles, per connection: version exchange, KEXINIT, curve25519 key 4 //! exchange, NEWKEYS, key derivation, chacha20-poly1305 packet codec, 5 //! strict kex (Terrapin mitigation), client-initiated rekeying, 6 //! ssh-userauth service request, publickey authentication (ed25519 and 7 //! rsa-sha2; captures the SHA256 fingerprint of the verified key), channel-layer 8 //! requests (pty-req, env, window-change, shell, exec), CHANNEL_DATA 9 //! flow with sender/receiver windows, and clean teardown 10 //! (exit-status / EOF / CLOSE). 11 //! 12 //! public surface for haxy code: 13 //! handleConnection — call from the listener with a session handler. 14 //! SessionCtx — handed to the handler; carries the channel + ciphers, 15 //! the verified key's fingerprint, and an event / 16 //! writeBytes / exit API. 17 //! SessionReader / SessionWriter — std.Io adapters so consumers (xit's 18 //! pack code, StreamTerminal, etc.) can use ordinary 19 //! Reader/Writer interfaces. 20 //! Request — what the client asked for: shell+pty or exec command. 21 //! HostKey — generated or loaded once at startup. 22 //! 23 //! hardcoded choices to keep the implementation small: 24 //! KEX: curve25519-sha256 (RFC 8731) 25 //! host key: ssh-ed25519 (RFC 8709) 26 //! cipher: chacha20-poly1305@openssh.com (RFC 4253 + openssh extension) 27 //! MAC: none (implicit in AEAD) 28 //! compress: none 29 //! user auth: publickey + ssh-ed25519, rsa-sha2-512, rsa-sha2-256 30 31 const std = @import("std"); 32 const builtin = @import("builtin"); 33 const Ed25519 = std.crypto.sign.Ed25519; 34 const X25519 = std.crypto.dh.X25519; 35 const Sha256 = std.crypto.hash.sha2.Sha256; 36 const Sha512 = std.crypto.hash.sha2.Sha512; 37 const rsa = std.crypto.Certificate.rsa; 38 const ChaCha20 = std.crypto.stream.chacha.ChaCha20With64BitNonce; 39 const Poly1305 = std.crypto.onetimeauth.Poly1305; 40 41 pub const server_version = "SSH-2.0-haxy_0.0"; 42 pub const host_key_file_name = "ssh_host_ed25519_key"; 43 const max_host_key_file_len = 4096; 44 45 const max_packet_len: u32 = 35000; // RFC 4253 §6.1 — minimum implementations must support 46 pub const packet_buffer_size = 4 + max_packet_len + Poly1305.mac_length; 47 const max_name_list_len: u32 = 4096; 48 const max_auth_attempts: u32 = 20; 49 const max_banner_lines: u32 = 32; 50 // terminal grids can have several live copies during layout and rendering 51 const max_pty_width: u32 = 512; 52 const max_pty_height: u32 = 128; 53 54 // SSH message type bytes (RFC 4250 §4.1) 55 pub const SSH_MSG_DISCONNECT: u8 = 1; 56 pub const SSH_MSG_IGNORE: u8 = 2; 57 pub const SSH_MSG_UNIMPLEMENTED: u8 = 3; 58 pub const SSH_MSG_DEBUG: u8 = 4; 59 pub const SSH_MSG_SERVICE_REQUEST: u8 = 5; 60 pub const SSH_MSG_SERVICE_ACCEPT: u8 = 6; 61 pub const SSH_MSG_EXT_INFO: u8 = 7; 62 pub const SSH_MSG_KEXINIT: u8 = 20; 63 pub const SSH_MSG_NEWKEYS: u8 = 21; 64 pub const SSH_MSG_KEX_ECDH_INIT: u8 = 30; 65 pub const SSH_MSG_KEX_ECDH_REPLY: u8 = 31; 66 pub const SSH_MSG_USERAUTH_REQUEST: u8 = 50; 67 pub const SSH_MSG_USERAUTH_FAILURE: u8 = 51; 68 pub const SSH_MSG_USERAUTH_SUCCESS: u8 = 52; 69 pub const SSH_MSG_USERAUTH_PK_OK: u8 = 60; // method-specific name for publickey 70 pub const SSH_MSG_GLOBAL_REQUEST: u8 = 80; 71 pub const SSH_MSG_REQUEST_SUCCESS: u8 = 81; 72 pub const SSH_MSG_REQUEST_FAILURE: u8 = 82; 73 pub const SSH_MSG_CHANNEL_OPEN: u8 = 90; 74 pub const SSH_MSG_CHANNEL_OPEN_CONFIRMATION: u8 = 91; 75 pub const SSH_MSG_CHANNEL_OPEN_FAILURE: u8 = 92; 76 pub const SSH_MSG_CHANNEL_WINDOW_ADJUST: u8 = 93; 77 pub const SSH_MSG_CHANNEL_DATA: u8 = 94; 78 pub const SSH_MSG_CHANNEL_EXTENDED_DATA: u8 = 95; 79 pub const SSH_MSG_CHANNEL_EOF: u8 = 96; 80 pub const SSH_MSG_CHANNEL_CLOSE: u8 = 97; 81 pub const SSH_MSG_CHANNEL_REQUEST: u8 = 98; 82 pub const SSH_MSG_CHANNEL_SUCCESS: u8 = 99; 83 pub const SSH_MSG_CHANNEL_FAILURE: u8 = 100; 84 85 pub const SSH_DISCONNECT_PROTOCOL_ERROR: u32 = 2; 86 pub const SSH_DISCONNECT_MAC_ERROR: u32 = 5; 87 pub const SSH_DISCONNECT_BY_APPLICATION: u32 = 11; 88 89 // SSH_OPEN_* reason codes for CHANNEL_OPEN_FAILURE 90 pub const SSH_OPEN_RESOURCE_SHORTAGE: u32 = 4; 91 pub const SSH_OPEN_UNKNOWN_CHANNEL_TYPE: u32 = 3; 92 93 // data type code for CHANNEL_EXTENDED_DATA (stderr) 94 pub const SSH_EXTENDED_DATA_STDERR: u32 = 1; 95 96 // initial flow-control window we advertise. typical openssh setting; large 97 // enough that small interactive sessions never need a WINDOW_ADJUST. 98 const initial_recv_window: u32 = 1 << 20; 99 const max_packet_size: u32 = 32768; 100 // ceiling on unread CHANNEL_DATA held for the consumer. window credit is only 101 // ever restored up to what's left of this, so the peer can't send more than 102 // the buffer will take. 103 const max_incoming_buffered: u32 = initial_recv_window; 104 105 /// shared with the host's watchdog. `activity` is bumped for non-ignored 106 /// session packets and for packets we send, `waiting` is set while we're 107 /// blocked on the peer, `session_started` releases the hard pre-session 108 /// deadline, and `closing` starts the bounded close drain. `exempt` is set 109 /// once an interactive session starts, since users idle in a TUI legitimately. 110 pub const IdleState = struct { 111 activity: std.atomic.Value(u64) = .init(0), 112 waiting: std.atomic.Value(bool) = .init(false), 113 session_started: std.atomic.Value(bool) = .init(false), 114 exempt: std.atomic.Value(bool) = .init(false), 115 closing: std.atomic.Value(bool) = .init(false), 116 }; 117 118 // --------------------------------------------------------------------------- 119 // host key 120 // --------------------------------------------------------------------------- 121 122 pub const HostKey = struct { 123 keypair: Ed25519.KeyPair, 124 125 pub fn loadOrGenerate(io: std.Io, allocator: std.mem.Allocator, data_dir_path: []const u8) !HostKey { 126 const path = try std.fs.path.join(allocator, &.{ data_dir_path, host_key_file_name }); 127 defer allocator.free(path); 128 129 const cwd = std.Io.Dir.cwd(); 130 var text_buf: [max_host_key_file_len]u8 = undefined; 131 defer std.crypto.secureZero(u8, &text_buf); 132 if (cwd.readFile(io, path, &text_buf)) |text| { 133 return parseOpenssh(text); 134 } else |err| switch (err) { 135 error.FileNotFound => {}, 136 else => return err, 137 } 138 139 const host_key: HostKey = .{ .keypair = Ed25519.KeyPair.generate(io) }; 140 const text = try host_key.formatOpenssh(allocator); 141 defer allocator.free(text); 142 defer std.crypto.secureZero(u8, text); 143 // owner-only from the start — never a window where the key is readable 144 const permissions: std.Io.File.Permissions = if (builtin.os.tag == .windows) .default_file else @enumFromInt(0o600); 145 // linked into place only once complete, and never over an existing key 146 var atomic_file = try cwd.createFileAtomic(io, path, .{ .permissions = permissions }); 147 defer atomic_file.deinit(io); 148 try atomic_file.file.writeStreamingAll(io, text); 149 try atomic_file.link(io); 150 return host_key; 151 } 152 153 const openssh_magic = "openssh-key-v1\x00"; 154 const openssh_begin = "-----BEGIN OPENSSH PRIVATE KEY-----"; 155 const openssh_end = "-----END OPENSSH PRIVATE KEY-----"; 156 157 /// the unencrypted openssh-key-v1 file that `ssh-keygen` writes and reads 158 fn formatOpenssh(self: HostKey, allocator: std.mem.Allocator) ![]u8 { 159 var public_blob: std.ArrayList(u8) = .empty; 160 defer public_blob.deinit(allocator); 161 try self.appendPublicBlob(&public_blob, allocator); 162 163 // two equal check ints show a reader that the section decrypted 164 // properly, a formality without a cipher 165 var private: std.ArrayList(u8) = .empty; 166 defer private.deinit(allocator); 167 defer std.crypto.secureZero(u8, private.items); 168 // every buffer that holds the secret is reserved up front, so a 169 // reallocation can't leave a copy behind, and wiped before it's freed 170 const private_capacity = 256; 171 try private.ensureTotalCapacityPrecise(allocator, private_capacity); 172 try writeU32(&private, allocator, 0); 173 try writeU32(&private, allocator, 0); 174 try writeStringField(&private, allocator, "ssh-ed25519"); 175 try writeStringField(&private, allocator, &self.keypair.public_key.bytes); 176 try writeStringField(&private, allocator, &self.keypair.secret_key.bytes); 177 try writeStringField(&private, allocator, "haxy"); // comment 178 // padded with 1, 2, 3 and so on to the cipher's block size, 8 for none 179 var pad: u8 = 1; 180 while (private.items.len % 8 != 0) : (pad += 1) try private.append(allocator, pad); 181 std.debug.assert(private.items.len <= private_capacity); 182 183 var blob: std.ArrayList(u8) = .empty; 184 defer blob.deinit(allocator); 185 defer std.crypto.secureZero(u8, blob.items); 186 const blob_capacity = 128 + public_blob.items.len + private.items.len; 187 try blob.ensureTotalCapacityPrecise(allocator, blob_capacity); 188 try blob.appendSlice(allocator, openssh_magic); 189 try writeStringField(&blob, allocator, "none"); // cipher 190 try writeStringField(&blob, allocator, "none"); // kdf 191 try writeStringField(&blob, allocator, ""); // kdf options 192 try writeU32(&blob, allocator, 1); // number of keys 193 try writeStringField(&blob, allocator, public_blob.items); 194 try writeStringField(&blob, allocator, private.items); 195 std.debug.assert(blob.items.len <= blob_capacity); 196 197 const encoder = std.base64.standard.Encoder; 198 const encoded = try allocator.alloc(u8, encoder.calcSize(blob.items.len)); 199 defer allocator.free(encoded); 200 defer std.crypto.secureZero(u8, encoded); 201 _ = encoder.encode(encoded, blob.items); 202 203 // sized exactly, so toOwnedSlice hands over the allocation as it is 204 const line_len = 70; 205 const line_count = std.math.divCeil(usize, encoded.len, line_len) catch unreachable; 206 var text: std.ArrayList(u8) = .empty; 207 errdefer text.deinit(allocator); 208 errdefer std.crypto.secureZero(u8, text.items); 209 try text.ensureTotalCapacityPrecise(allocator, openssh_begin.len + 1 + encoded.len + line_count + openssh_end.len + 1); 210 try text.appendSlice(allocator, openssh_begin ++ "\n"); 211 var lines = std.mem.window(u8, encoded, line_len, line_len); 212 while (lines.next()) |line| { 213 try text.appendSlice(allocator, line); 214 try text.append(allocator, '\n'); 215 } 216 try text.appendSlice(allocator, openssh_end ++ "\n"); 217 return try text.toOwnedSlice(allocator); 218 } 219 220 fn parseOpenssh(text: []const u8) !HostKey { 221 const trimmed = std.mem.trim(u8, text, " \t\r\n"); 222 if (!std.mem.startsWith(u8, trimmed, openssh_begin) or !std.mem.endsWith(u8, trimmed, openssh_end)) return error.InvalidHostKey; 223 const encoded = trimmed[openssh_begin.len .. trimmed.len - openssh_end.len]; 224 225 var blob_buf: [max_host_key_file_len]u8 = undefined; 226 defer std.crypto.secureZero(u8, &blob_buf); 227 const decoder = std.base64.standard.decoderWithIgnore(" \t\r\n"); 228 const blob_len = decoder.decode(&blob_buf, encoded) catch return error.InvalidHostKey; 229 return parseOpensshBlob(blob_buf[0..blob_len]) catch |err| switch (err) { 230 error.EncryptedHostKey, error.UnsupportedHostKeyType => |e| e, 231 else => error.InvalidHostKey, 232 }; 233 } 234 235 fn parseOpensshBlob(blob: []const u8) !HostKey { 236 var r = std.Io.Reader.fixed(blob); 237 if (!std.mem.eql(u8, try r.take(openssh_magic.len), openssh_magic)) return error.InvalidHostKey; 238 const cipher_name = try takeString(&r, 64); 239 const kdf_name = try takeString(&r, 64); 240 _ = try takeString(&r, 1024); // kdf options 241 if (!std.mem.eql(u8, cipher_name, "none") or !std.mem.eql(u8, kdf_name, "none")) return error.EncryptedHostKey; 242 if (try r.takeInt(u32, .big) != 1) return error.InvalidHostKey; 243 var outer = std.Io.Reader.fixed(try takeString(&r, 1024)); 244 const private_section = try takeString(&r, 2048); 245 if (r.bufferedLen() != 0) return error.InvalidHostKey; 246 247 var private = std.Io.Reader.fixed(private_section); 248 if (try private.takeInt(u32, .big) != try private.takeInt(u32, .big)) return error.InvalidHostKey; 249 if (!std.mem.eql(u8, try takeString(&private, 64), "ssh-ed25519")) return error.UnsupportedHostKeyType; 250 const public = try takeString(&private, 64); 251 const secret = try takeString(&private, 128); 252 if (secret.len != Ed25519.SecretKey.encoded_length) return error.InvalidHostKey; 253 _ = try takeString(&private, 1024); // comment 254 255 // padded with 1, 2, 3 and so on to the cipher's block size, 8 for none 256 if (private_section.len % 8 != 0) return error.InvalidHostKey; 257 for (private.buffered(), 1..) |byte, i| { 258 if (byte != i) return error.InvalidHostKey; 259 } 260 261 // the outer public key must be the same key 262 if (!std.mem.eql(u8, try takeString(&outer, 64), "ssh-ed25519") or 263 !std.mem.eql(u8, try takeString(&outer, 64), public) or 264 outer.bufferedLen() != 0) return error.InvalidHostKey; 265 266 // the secret is seed || public. rebuild it from the seed so a file 267 // whose halves disagree is rejected in every build mode. 268 const keypair = try Ed25519.KeyPair.generateDeterministic(secret[0..Ed25519.KeyPair.seed_length].*); 269 if (!std.mem.eql(u8, secret, &keypair.secret_key.bytes) or 270 !std.mem.eql(u8, public, &keypair.public_key.bytes)) return error.InvalidHostKey; 271 return .{ .keypair = keypair }; 272 } 273 274 /// what `ssh` shows a user on first connect 275 pub fn fingerprint(self: HostKey, allocator: std.mem.Allocator) ![fingerprint_len]u8 { 276 var blob: std.ArrayList(u8) = .empty; 277 defer blob.deinit(allocator); 278 try self.appendPublicBlob(&blob, allocator); 279 return formatFingerprint(blob.items); 280 } 281 282 /// SSH wire-format ed25519 public key blob (used as K_S in the hash and 283 /// returned in KEX_ECDH_REPLY): string "ssh-ed25519" || string pubkey. 284 pub fn appendPublicBlob(self: HostKey, buf: *std.ArrayList(u8), allocator: std.mem.Allocator) !void { 285 try writeStringField(buf, allocator, "ssh-ed25519"); 286 try writeStringField(buf, allocator, &self.keypair.public_key.bytes); 287 } 288 289 /// SSH wire-format signature blob: string "ssh-ed25519" || string sig. 290 fn appendSignatureBlob(self: HostKey, buf: *std.ArrayList(u8), allocator: std.mem.Allocator, message: []const u8) !void { 291 const sig = try self.keypair.sign(message, null); 292 const sig_bytes = sig.toBytes(); 293 try writeStringField(buf, allocator, "ssh-ed25519"); 294 try writeStringField(buf, allocator, &sig_bytes); 295 } 296 }; 297 298 // --------------------------------------------------------------------------- 299 // public session API 300 // --------------------------------------------------------------------------- 301 302 /// what the client wants to do on this channel. 303 pub const Request = union(enum) { 304 shell: ?PtySize, // pty info if a pty-req arrived before the shell 305 exec: Exec, 306 307 pub const Exec = struct { 308 command: []const u8, 309 /// the GIT_PROTOCOL env value, if one arrived before the exec 310 git_protocol: ?[]const u8, 311 }; 312 }; 313 314 /// next thing that arrived from the client. 315 pub const Event = union(enum) { 316 data: []u8, // CHANNEL_DATA payload — caller owns and must free via sess.conn.allocator 317 resize: PtySize, // window-change request 318 eof, // peer sent CHANNEL_EOF: no more input, but we may still write 319 close, // peer sent CHANNEL_CLOSE, or the transport hit EOF 320 }; 321 322 /// per-connection transport state: the byte stream, both ciphers, and what a 323 /// rekey needs. built once after the initial KEX and threaded through the 324 /// auth and channel layers. 325 pub const Conn = struct { 326 io: std.Io, 327 allocator: std.mem.Allocator, 328 reader: *std.Io.Reader, 329 writer: *std.Io.Writer, 330 cs_cipher: Cipher, 331 sc_cipher: Cipher, 332 rekey: RekeyState, 333 idle: *IdleState, 334 // set only while the TUI waits to resolve a lone escape key 335 read_timeout: std.Io.Timeout = .none, 336 // teardown ran to the peer's EOF, so nothing more can be said 337 drained: bool = false, 338 339 fn writePacket(self: *Conn, parts: []const []const u8) !void { 340 self.idle.waiting.store(true, .release); 341 defer self.idle.waiting.store(false, .release); 342 try self.sc_cipher.writePacket(self.io, self.writer, parts); 343 // a peer that keeps reading is alive 344 _ = self.idle.activity.fetchAdd(1, .acq_rel); 345 } 346 347 fn readPacket(self: *Conn) ![]u8 { 348 self.idle.waiting.store(true, .release); 349 defer self.idle.waiting.store(false, .release); 350 if (self.read_timeout != .none and !try self.cs_cipher.hasBufferedPacket(self.reader)) { 351 // peek keeps partial packets in the reader if the timer wins. 352 // join both tasks before consuming bytes or changing cipher state. 353 const Result = union(enum) { ready: anyerror!void, timeout: std.Io.Cancelable!void }; 354 var results: [2]Result = undefined; 355 var select = std.Io.Select(Result).init(self.io, &results); 356 defer select.cancelDiscard(); 357 try select.concurrent(.ready, Cipher.peekPacket, .{ &self.cs_cipher, self.reader }); 358 try select.concurrent(.timeout, std.Io.Timeout.sleep, .{ self.read_timeout, self.io }); 359 switch (try select.await()) { 360 .ready => |result| try result, 361 .timeout => |result| { 362 try result; 363 return error.Timeout; 364 }, 365 } 366 } 367 return self.cs_cipher.readPacket(self.allocator, self.reader); 368 } 369 }; 370 371 // how long a peer probe waits for a packet that may already be on its way 372 const probe_timeout: std.Io.Timeout = .{ .duration = .{ .raw = .fromMilliseconds(1), .clock = .awake } }; 373 374 /// session bridge handed to the consumer's handleSession callback. exposes a 375 /// pumped event API plus a byte-write API; the byte stream goes out as 376 /// CHANNEL_DATA packets respecting the channel's flow-control window. 377 pub const SessionCtx = struct { 378 conn: *Conn, 379 channel: *Channel, 380 /// SHA256 fingerprint of the pubkey this session authenticated with, 381 /// formatted as "SHA256:<base64-no-padding>" — same value the openssh 382 /// client logs as `Offering public key: ED25519 SHA256:…`. consumers 383 /// can use it as a stable per-key identity. 384 fingerprint: [fingerprint_len]u8, 385 closed: bool = false, 386 // what a SessionReader or SessionWriter actually hit. kept apart so a 387 // cleanup write can't replace the cause of a failed read. 388 read_err: ?anyerror = null, 389 write_err: ?anyerror = null, 390 391 // shared state for the packet pump. incoming CHANNEL_DATA bytes 392 // accumulate in incoming_buffer (already-consumed prefix tracked by 393 // incoming_start) until drained via SessionReader or nextEvent. 394 incoming_buffer: std.ArrayList(u8) = .empty, 395 incoming_start: usize = 0, 396 // peer sent CHANNEL_EOF — no more input arrives, but the channel stays 397 // open and we may keep writing (RFC 4254 §5.3) 398 incoming_eof: bool = false, 399 // peer sent CHANNEL_CLOSE, or the transport died — the channel is gone 400 remote_closed: bool = false, 401 // .eof is handed to the caller once; later pumps wait for the close 402 eof_reported: bool = false, 403 // resize seen by the background pump, returned by the next nextEvent call 404 pending_resize: ?PtySize = null, 405 406 pub fn deinit(self: *SessionCtx) void { 407 self.incoming_buffer.deinit(self.conn.allocator); 408 } 409 410 /// whether the client is gone. a push spends its transaction writing 411 /// rather than reading, so a peer that hung up has to be pumped for. one 412 /// pending packet is processed, which is where a close is seen. 413 pub fn peerGone(self: *SessionCtx) bool { 414 if (self.closed or self.remote_closed) return true; 415 self.conn.read_timeout = probe_timeout.toDeadline(self.conn.io); 416 defer self.conn.read_timeout = .none; 417 self.processOneBackgroundPacket() catch |err| return err != error.Timeout; 418 return self.remote_closed; 419 } 420 421 /// the std.Io adapters can only report ReadFailed or WriteFailed. recover 422 /// what the session hit. 423 pub fn underlyingError(self: *const SessionCtx, err: anyerror) anyerror { 424 return switch (err) { 425 error.ReadFailed => self.read_err orelse err, 426 error.WriteFailed => self.write_err orelse err, 427 else => err, 428 }; 429 } 430 431 fn failRead(self: *SessionCtx, err: anyerror) error{ReadFailed} { 432 self.read_err = err; 433 return error.ReadFailed; 434 } 435 436 fn failWrite(self: *SessionCtx, err: anyerror) error{WriteFailed} { 437 self.write_err = err; 438 return error.WriteFailed; 439 } 440 441 fn incomingBytes(self: *const SessionCtx) []const u8 { 442 return self.incoming_buffer.items[self.incoming_start..]; 443 } 444 445 // mark n incoming bytes as consumed; the buffer is recycled once empty 446 fn consumeIncoming(self: *SessionCtx, n: usize) void { 447 self.incoming_start += n; 448 if (self.incoming_start == self.incoming_buffer.items.len) { 449 self.incoming_buffer.clearRetainingCapacity(); 450 self.incoming_start = 0; 451 } 452 } 453 454 // append to the incoming buffer, first compacting away the consumed 455 // prefix so the buffer only ever holds unread bytes. bounded by the 456 // receive window, which is never credited past max_incoming_buffered. 457 fn appendIncoming(self: *SessionCtx, payload: []const u8) !void { 458 if (self.incoming_start > 0) { 459 const remaining = self.incoming_buffer.items.len - self.incoming_start; 460 std.mem.copyForwards(u8, self.incoming_buffer.items[0..remaining], self.incoming_buffer.items[self.incoming_start..]); 461 self.incoming_buffer.shrinkRetainingCapacity(remaining); 462 self.incoming_start = 0; 463 } 464 try self.incoming_buffer.appendSlice(self.conn.allocator, payload); 465 } 466 467 /// interactive sessions idle legitimately; tell the host's idle 468 /// watchdog to stand down for the rest of this connection. 469 pub fn exemptFromIdleTimeout(self: *SessionCtx) void { 470 self.conn.idle.exempt.store(true, .release); 471 } 472 473 /// pump SSH packets until something interesting (data / resize / close) 474 /// arrives. background traffic (window adjusts, env requests, etc.) is 475 /// handled silently. drains the same incoming state as SessionReader, 476 /// so a session should consume through one or the other, not both. 477 pub fn nextEvent(self: *SessionCtx) !Event { 478 while (true) { 479 if (self.pending_resize) |sz| { 480 self.pending_resize = null; 481 return .{ .resize = sz }; 482 } 483 if (self.incomingBytes().len > 0) { 484 // hand the buffered bytes to the caller (caller owns) 485 const payload = try self.conn.allocator.dupe(u8, self.incomingBytes()); 486 errdefer self.conn.allocator.free(payload); 487 self.consumeIncoming(payload.len); 488 try self.maybeRefillRecvWindowForBufferedInput(); 489 return .{ .data = payload }; 490 } 491 if (self.remote_closed) return .close; 492 if (self.incoming_eof and !self.eof_reported) { 493 self.eof_reported = true; 494 return .eof; 495 } 496 try self.processOneBackgroundPacket(); 497 } 498 } 499 500 /// ship bytes to the client's stdout as one or more CHANNEL_DATA packets, 501 /// respecting the peer's max-packet size. if the remote window is 502 /// exhausted, pump incoming SSH packets until a WINDOW_ADJUST arrives 503 /// (background packets are processed for their side effects — incoming 504 /// CHANNEL_DATA goes into incoming_buffer for a future SessionReader). 505 pub fn writeBytes(self: *SessionCtx, bytes: []const u8) !void { 506 const conn = self.conn; 507 508 // byte SSH_MSG_CHANNEL_DATA, uint32 recipient_channel, uint32 data length 509 var header: [9]u8 = undefined; 510 header[0] = SSH_MSG_CHANNEL_DATA; 511 std.mem.writeInt(u32, header[1..5], self.channel.remote_id, .big); 512 513 var rest = bytes; 514 while (rest.len > 0) { 515 if (self.closed or self.remote_closed) return error.RemoteClosed; 516 while (self.channel.remote_window == 0) { 517 if (self.remote_closed) return error.RemoteClosed; 518 try self.processOneBackgroundPacket(); 519 } 520 // also clamp to our own max so the chunk fits writePacket's buffer 521 const cap = @min(rest.len, self.channel.max_packet, self.channel.remote_window, max_packet_size); 522 const chunk_len: u32 = @intCast(cap); 523 524 std.mem.writeInt(u32, header[5..9], chunk_len, .big); 525 try conn.writePacket(&.{ &header, rest[0..chunk_len] }); 526 527 self.channel.remote_window -= chunk_len; 528 rest = rest[chunk_len..]; 529 } 530 } 531 532 /// the session's packet pump: process exactly one SSH packet for side 533 /// effects only. CHANNEL_DATA payloads accumulate in incoming_buffer; 534 /// CHANNEL_EOF/CLOSE flips incoming_eof; WINDOW_ADJUST updates the 535 /// channel state; window-change is stashed in pending_resize; other 536 /// channel/global requests get a polite failure. driven by nextEvent, 537 /// SessionReader, and writeBytes (waiting for send-window). 538 fn processOneBackgroundPacket(self: *SessionCtx) !void { 539 const conn = self.conn; 540 const packet = readSessionPacket(conn) catch |err| switch (err) { 541 error.EndOfStream => { 542 self.incoming_eof = true; 543 self.remote_closed = true; 544 return; 545 }, 546 else => return err, 547 }; 548 defer conn.allocator.free(packet); 549 550 switch (packet[0]) { 551 SSH_MSG_CHANNEL_DATA => { 552 const payload = try parseChannelData(packet, false, self.channel.local_id); 553 const data_len: u32 = @intCast(payload.len); 554 if (data_len > self.channel.local_window) return error.WindowExceeded; 555 self.channel.local_window -= data_len; 556 try self.appendIncoming(payload); 557 try self.maybeRefillRecvWindowForBufferedInput(); 558 }, 559 SSH_MSG_CHANNEL_EXTENDED_DATA => { 560 // discarded, but the window is still credited against what the 561 // incoming buffer can take, since CHANNEL_DATA may be sitting 562 // in it unread 563 try discardChannelData(self.channel, packet, true); 564 try self.maybeRefillRecvWindowForBufferedInput(); 565 }, 566 SSH_MSG_CHANNEL_WINDOW_ADJUST => try handleWindowAdjust(self.channel, packet), 567 SSH_MSG_CHANNEL_REQUEST => { 568 var r = std.Io.Reader.fixed(packet[1..]); 569 const recipient_channel = try r.takeInt(u32, .big); 570 if (recipient_channel != self.channel.local_id) return error.UnknownChannel; 571 const req_type = try takeString(&r, 64); 572 const want_reply = (try r.takeByte()) != 0; 573 if (std.mem.eql(u8, req_type, "window-change")) { 574 const sz = try takePtySize(&r); 575 if (self.channel.pty != null) self.channel.pty = sz; 576 self.pending_resize = sz; 577 try replyChannelRequest(conn, self.channel, want_reply, true); 578 } else { 579 // other mid-session channel requests aren't honored — fail them 580 try replyChannelRequest(conn, self.channel, want_reply, false); 581 } 582 }, 583 SSH_MSG_CHANNEL_EOF => { 584 try parseChannelId(packet, self.channel.local_id); 585 self.incoming_eof = true; 586 }, 587 SSH_MSG_CHANNEL_CLOSE => { 588 try parseChannelId(packet, self.channel.local_id); 589 self.incoming_eof = true; 590 self.remote_closed = true; 591 try sendChannelMessage(conn, self.channel, SSH_MSG_CHANNEL_CLOSE); 592 }, 593 SSH_MSG_GLOBAL_REQUEST => try handleGlobalRequest(conn, packet), 594 // RFC 4252 §5.1: silently ignored once authenticated 595 SSH_MSG_USERAUTH_REQUEST => {}, 596 else => try sendUnimplemented(conn), 597 } 598 } 599 600 fn maybeRefillRecvWindowForBufferedInput(self: *SessionCtx) !void { 601 if (self.remote_closed or self.closed) return; 602 // credit only what the incoming buffer can still take 603 const buffered: u32 = @intCast(self.incomingBytes().len); 604 try maybeRefillRecvWindow(self.conn, self.channel, max_incoming_buffered - buffered); 605 } 606 607 /// signal the consumer's exit status and tear the channel down. 608 pub fn exit(self: *SessionCtx, status: u32) !void { 609 if (self.closed) return; 610 self.closed = true; 611 const conn = self.conn; 612 conn.idle.closing.store(true, .release); 613 614 // a peer CLOSE is acknowledged by the packet pump. don't send data, 615 // exit-status, or EOF after that acknowledgement. 616 if (!self.remote_closed) { 617 // exit-status request (informational; client uses it as the 618 // command's exit code) 619 { 620 var req: std.ArrayList(u8) = .empty; 621 defer req.deinit(conn.allocator); 622 try req.append(conn.allocator, SSH_MSG_CHANNEL_REQUEST); 623 try writeU32(&req, conn.allocator, self.channel.remote_id); 624 try writeStringField(&req, conn.allocator, "exit-status"); 625 try req.append(conn.allocator, 0); // want_reply MUST be false 626 try writeU32(&req, conn.allocator, status); 627 try conn.writePacket(&.{req.items}); 628 } 629 630 // EOF then CLOSE 631 try sendChannelMessage(conn, self.channel, SSH_MSG_CHANNEL_EOF); 632 try sendChannelMessage(conn, self.channel, SSH_MSG_CHANNEL_CLOSE); 633 } 634 drainConnection(conn); 635 } 636 }; 637 638 fn drainConnection(conn: *Conn) void { 639 conn.idle.closing.store(true, .release); 640 // read and discard until the peer closes (TCP FIN) before letting the 641 // caller close the socket. a git client, after our CHANNEL_CLOSE, still 642 // sends its own CHANNEL_CLOSE and SSH_MSG_DISCONNECT before closing; if 643 // we close with those unread, Linux sends RST instead of FIN, which the 644 // client reports as "Connection reset by peer" and treats as a failed 645 // push even though the ref updated. draining to EOF leaves nothing 646 // unread, so we send a clean FIN. the bytes don't matter, and the host's 647 // watchdog bounds how long a peer can keep this going. 648 _ = conn.reader.discardRemaining() catch {}; 649 conn.drained = true; 650 } 651 652 /// std.Io.Writer adapter that ships bytes to a SessionCtx as CHANNEL_DATA. 653 /// useful for plugging the session into anything that wants a *std.Io.Writer 654 /// (e.g. xitui.StreamTerminal). 655 pub const SessionWriter = struct { 656 interface: std.Io.Writer, 657 sess: *SessionCtx, 658 659 pub fn init(sess: *SessionCtx, buffer: []u8) SessionWriter { 660 return .{ 661 .interface = .{ 662 .vtable = &.{ .drain = drain }, 663 .buffer = buffer, 664 }, 665 .sess = sess, 666 }; 667 } 668 669 fn drain(w: *std.Io.Writer, data: []const []const u8, splat: usize) std.Io.Writer.Error!usize { 670 const self: *SessionWriter = @fieldParentPtr("interface", w); 671 672 // first ship anything already accumulated in the Writer's buffer 673 const buffered = w.buffered(); 674 self.sess.writeBytes(buffered) catch |err| return self.sess.failWrite(err); 675 676 // then ship the bytes passed in directly. data[0..len-1] are written 677 // once each; data[len-1] is written `splat` times (this is how the 678 // Writer interface represents fan-out / repeated patterns). 679 var extra: usize = 0; 680 for (data[0 .. data.len - 1]) |chunk| { 681 self.sess.writeBytes(chunk) catch |err| return self.sess.failWrite(err); 682 extra += chunk.len; 683 } 684 const pattern = data[data.len - 1]; 685 for (0..splat) |_| { 686 self.sess.writeBytes(pattern) catch |err| return self.sess.failWrite(err); 687 extra += pattern.len; 688 } 689 690 // consume tells the Writer how many bytes (buffered + data) were 691 // processed and clears w.end. it returns the count attributed to 692 // data, which is what `write` propagates back to the caller. 693 return w.consume(buffered.len + extra); 694 } 695 }; 696 697 /// std.Io.Reader adapter that drains incoming CHANNEL_DATA from a SessionCtx. 698 /// when the consumer reads beyond what's buffered, runs the SSH packet loop 699 /// (via processOneBackgroundPacket) until more bytes arrive or the peer 700 /// closes the channel. 701 pub const SessionReader = struct { 702 interface: std.Io.Reader, 703 sess: *SessionCtx, 704 705 pub fn init(sess: *SessionCtx, buffer: []u8) SessionReader { 706 return .{ 707 .interface = .{ 708 .vtable = &.{ .stream = stream }, 709 .buffer = buffer, 710 .seek = 0, 711 .end = 0, 712 }, 713 .sess = sess, 714 }; 715 } 716 717 fn stream(r: *std.Io.Reader, w: *std.Io.Writer, limit: std.Io.Limit) std.Io.Reader.StreamError!usize { 718 const self: *SessionReader = @fieldParentPtr("interface", r); 719 720 // wait for data to arrive (or EOF) 721 while (self.sess.incomingBytes().len == 0) { 722 if (self.sess.incoming_eof) return error.EndOfStream; 723 self.sess.processOneBackgroundPacket() catch |err| return self.sess.failRead(err); 724 } 725 726 // drain as much buffered input as the limit allows, in one go 727 const chunk = limit.sliceConst(self.sess.incomingBytes()); 728 const written = try w.write(chunk); 729 730 self.sess.consumeIncoming(written); 731 self.sess.maybeRefillRecvWindowForBufferedInput() catch |err| return self.sess.failRead(err); 732 733 return written; 734 } 735 }; 736 737 // --------------------------------------------------------------------------- 738 // public entry point 739 // --------------------------------------------------------------------------- 740 741 /// `handler` must be a pointer to a struct with a method: 742 /// pub fn handleSession(self, sess: *SessionCtx, request: Request) anyerror!void 743 /// invoked once the channel is open and a shell/exec request has arrived. 744 /// 745 /// `reader` and `writer` are the bidirectional byte stream. `idle` is kept 746 /// current for the host's watchdog. 747 pub fn handleConnection( 748 io: std.Io, 749 allocator: std.mem.Allocator, 750 reader: *std.Io.Reader, 751 writer: *std.Io.Writer, 752 host_key: *const HostKey, 753 idle: *IdleState, 754 handler: anytype, 755 ) !void { 756 const client_version = try exchangeVersions(allocator, reader, writer); 757 defer allocator.free(client_version); 758 759 var conn = try runKex(io, allocator, reader, writer, host_key, client_version, idle); 760 defer std.crypto.secureZero(u8, std.mem.asBytes(&conn.cs_cipher)); 761 defer std.crypto.secureZero(u8, std.mem.asBytes(&conn.sc_cipher)); 762 763 errdefer |err| disconnectOnError(&conn, err); 764 765 const fingerprint = try runAuth(&conn); 766 try runChannelLayer(&conn, &fingerprint, handler); 767 } 768 769 /// tell the peer why we're hanging up (RFC 4253 §11.1), best effort. protocol 770 /// errors are named for whoever is debugging the client. 771 fn disconnectOnError(conn: *Conn, err: anyerror) void { 772 if (conn.drained) return; 773 const reason: u32, const description: []const u8 = switch (err) { 774 // the peer hung up first, or the transport is broken 775 error.EndOfStream, error.ReadFailed, error.WriteFailed => return, 776 error.MacVerificationFailed => .{ SSH_DISCONNECT_MAC_ERROR, @errorName(err) }, 777 error.OutOfMemory, error.Canceled => .{ SSH_DISCONNECT_BY_APPLICATION, "server error" }, 778 else => .{ SSH_DISCONNECT_PROTOCOL_ERROR, @errorName(err) }, 779 }; 780 781 disconnect(conn, reason, description) catch {}; 782 } 783 784 fn disconnect(conn: *Conn, reason: u32, description: []const u8) !void { 785 var buf: std.ArrayList(u8) = .empty; 786 defer buf.deinit(conn.allocator); 787 try buf.append(conn.allocator, SSH_MSG_DISCONNECT); 788 try writeU32(&buf, conn.allocator, reason); 789 try writeStringField(&buf, conn.allocator, description); 790 try writeStringField(&buf, conn.allocator, ""); // language tag 791 try conn.writePacket(&.{buf.items}); 792 } 793 794 // --------------------------------------------------------------------------- 795 // version exchange (RFC 4253 §4.2) 796 // --------------------------------------------------------------------------- 797 798 fn exchangeVersions( 799 allocator: std.mem.Allocator, 800 reader: *std.Io.Reader, 801 writer: *std.Io.Writer, 802 ) ![]u8 { 803 try writer.writeAll(server_version ++ "\r\n"); 804 try writer.flush(); 805 806 // the spec allows the client to send comment lines before its banner; 807 // skip anything that isn't an "SSH-2.0-…" / "SSH-1.99-…" line, up to a cap 808 // so a garbage-spewing peer can't hold the connection open forever. 809 var lines: u32 = 0; 810 while (lines < max_banner_lines) : (lines += 1) { 811 const line = (try reader.takeDelimiter('\n')) orelse return error.UnexpectedEof; 812 const trimmed = if (line.len > 0 and line[line.len - 1] == '\r') line[0 .. line.len - 1] else line; 813 if (std.mem.startsWith(u8, trimmed, "SSH-2.0-") or std.mem.startsWith(u8, trimmed, "SSH-1.99-")) { 814 return try allocator.dupe(u8, trimmed); 815 } 816 } 817 return error.TooManyBannerLines; 818 } 819 820 // --------------------------------------------------------------------------- 821 // binary packet codec, unencrypted form (RFC 4253 §6) 822 // --------------------------------------------------------------------------- 823 824 pub fn writePlainPacket(io: std.Io, writer: *std.Io.Writer, payload: []const u8) !void { 825 const block: usize = 8; 826 const initial_pad = block - ((5 + payload.len) % block); 827 const padding_len: u8 = @intCast(if (initial_pad < 4) initial_pad + block else initial_pad); 828 const packet_len: u32 = @intCast(1 + payload.len + padding_len); 829 830 try writer.writeInt(u32, packet_len, .big); 831 try writer.writeByte(padding_len); 832 try writer.writeAll(payload); 833 834 var padding: [255]u8 = undefined; 835 io.random(padding[0..padding_len]); 836 try writer.writeAll(padding[0..padding_len]); 837 try writer.flush(); 838 } 839 840 pub fn readPlainPacket(allocator: std.mem.Allocator, reader: *std.Io.Reader) ![]u8 { 841 const packet_len = try reader.takeInt(u32, .big); 842 if (packet_len < 8 or packet_len > max_packet_len) return error.InvalidPacketLength; 843 const padding_len = try reader.takeByte(); 844 if (padding_len < 4 or @as(u32, padding_len) + 1 > packet_len) return error.InvalidPadding; 845 const payload_len = packet_len - 1 - @as(u32, padding_len); 846 // a payload starts with its message type 847 if (payload_len == 0) return error.EmptyPacket; 848 849 const payload = try reader.readAlloc(allocator, payload_len); 850 errdefer allocator.free(payload); 851 try reader.discardAll(padding_len); 852 return payload; 853 } 854 855 // IGNORE/DEBUG/UNIMPLEMENTED may arrive at any time (RFC 4253 §11); skip 856 // them wherever a specific message is expected 857 fn isIgnorableMsg(msg_type: u8) bool { 858 return msg_type == SSH_MSG_IGNORE or msg_type == SSH_MSG_UNIMPLEMENTED or msg_type == SSH_MSG_DEBUG; 859 } 860 861 /// packets handled during the plaintext phase — each direction's cipher picks 862 /// up its sequence number where that direction left off. 863 pub const PlainSeqs = struct { read: u64 = 0, written: u64 = 0 }; 864 865 // transport for KEX packets: the initial exchange runs in plaintext, a rekey 866 // runs under the current session ciphers. 867 pub const KexTransport = union(enum) { 868 plain: *PlainSeqs, 869 encrypted: struct { cs: *Cipher, sc: *Cipher }, 870 871 // read one packet, skipping ignorable messages — unless strict kex is in 872 // force, which bans them mid-handshake 873 pub fn readPacket(self: KexTransport, allocator: std.mem.Allocator, reader: *std.Io.Reader, strict: bool) ![]u8 { 874 while (true) { 875 const packet = switch (self) { 876 .plain => |seqs| packet: { 877 const packet = try readPlainPacket(allocator, reader); 878 seqs.read += 1; 879 break :packet packet; 880 }, 881 .encrypted => |ciphers| try ciphers.cs.readPacket(allocator, reader), 882 }; 883 if (isIgnorableMsg(packet[0])) { 884 allocator.free(packet); 885 if (strict) return error.StrictKexViolation; 886 continue; 887 } 888 return packet; 889 } 890 } 891 892 fn writePacket(self: KexTransport, io: std.Io, writer: *std.Io.Writer, payload: []const u8) !void { 893 switch (self) { 894 .plain => |seqs| { 895 try writePlainPacket(io, writer, payload); 896 seqs.written += 1; 897 }, 898 .encrypted => |ciphers| try ciphers.sc.writePacket(io, writer, &.{payload}), 899 } 900 } 901 }; 902 903 // read one encrypted packet for the auth and channel layers, transparently 904 // skipping ignorable messages and servicing client-initiated rekeys. 905 pub fn readSessionPacket(conn: *Conn) ![]u8 { 906 while (true) { 907 const packet = try conn.readPacket(); 908 if (isIgnorableMsg(packet[0])) { 909 conn.allocator.free(packet); 910 continue; 911 } 912 // the peer is hanging up (RFC 4253 §11.1). same end of the packet 913 // stream as a transport close, so callers handle both the same way. 914 if (packet[0] == SSH_MSG_DISCONNECT) { 915 conn.allocator.free(packet); 916 return error.EndOfStream; 917 } 918 if (packet[0] == SSH_MSG_KEXINIT) { 919 defer conn.allocator.free(packet); 920 _ = conn.idle.activity.fetchAdd(1, .acq_rel); 921 try runRekey(conn, packet); 922 continue; 923 } 924 _ = conn.idle.activity.fetchAdd(1, .acq_rel); 925 return packet; 926 } 927 } 928 929 /// RFC 4253 §11.4 — an unrecognized message must be answered with 930 /// SSH_MSG_UNIMPLEMENTED carrying the offending packet's sequence number. 931 fn sendUnimplemented(conn: *Conn) !void { 932 var packet: [5]u8 = undefined; 933 packet[0] = SSH_MSG_UNIMPLEMENTED; 934 // the read already advanced past the packet we're rejecting 935 std.mem.writeInt(u32, packet[1..5], @truncate(conn.cs_cipher.seq - 1), .big); 936 try conn.writePacket(&.{&packet}); 937 } 938 939 // --------------------------------------------------------------------------- 940 // SSH field encoders / decoders (RFC 4251 §5) 941 // --------------------------------------------------------------------------- 942 943 pub fn writeStringField(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, bytes: []const u8) !void { 944 var len_bytes: [4]u8 = undefined; 945 std.mem.writeInt(u32, &len_bytes, @intCast(bytes.len), .big); 946 try buf.appendSlice(allocator, &len_bytes); 947 try buf.appendSlice(allocator, bytes); 948 } 949 950 pub fn writeNameList(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, names: []const []const u8) !void { 951 var total: usize = 0; 952 for (names, 0..) |name, i| { 953 if (i > 0) total += 1; // comma separator 954 total += name.len; 955 } 956 var len_bytes: [4]u8 = undefined; 957 std.mem.writeInt(u32, &len_bytes, @intCast(total), .big); 958 try buf.appendSlice(allocator, &len_bytes); 959 for (names, 0..) |name, i| { 960 if (i > 0) try buf.append(allocator, ','); 961 try buf.appendSlice(allocator, name); 962 } 963 } 964 965 /// SSH "mpint" — big-endian two's complement multi-precision integer. for 966 /// our use (X25519 shared secret) the value is always non-negative, so we 967 /// strip leading zero bytes, then prepend a single 0x00 if the high bit of 968 /// the most-significant byte is set (to keep it parsed as positive). 969 pub fn writeMpint(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, bytes: []const u8) !void { 970 var start: usize = 0; 971 while (start < bytes.len and bytes[start] == 0) start += 1; 972 const trimmed = bytes[start..]; 973 if (trimmed.len == 0) { 974 try buf.appendSlice(allocator, &[_]u8{ 0, 0, 0, 0 }); 975 return; 976 } 977 const prepend = (trimmed[0] & 0x80) != 0; 978 const out_len: u32 = @intCast(trimmed.len + @as(usize, @intFromBool(prepend))); 979 var len_bytes: [4]u8 = undefined; 980 std.mem.writeInt(u32, &len_bytes, out_len, .big); 981 try buf.appendSlice(allocator, &len_bytes); 982 if (prepend) try buf.append(allocator, 0); 983 try buf.appendSlice(allocator, trimmed); 984 } 985 986 /// a string field's bytes, borrowed from the packet behind a fixed reader 987 pub fn takeString(reader: *std.Io.Reader, max_len: u32) ![]const u8 { 988 const len = try reader.takeInt(u32, .big); 989 if (len > max_len) return error.FieldTooLarge; 990 return reader.take(len); 991 } 992 993 // the first name in the peer's preference list that we also support (RFC 994 // 4253 §7.1) 995 fn firstCommonName(peer_names: []const u8, our_names: []const []const u8) ?[]const u8 { 996 var iter = std.mem.splitScalar(u8, peer_names, ','); 997 while (iter.next()) |name| { 998 for (our_names) |ours| { 999 if (std.mem.eql(u8, name, ours)) return ours; 1000 } 1001 } 1002 return null; 1003 } 1004 1005 // --------------------------------------------------------------------------- 1006 // KEXINIT (RFC 4253 §7.1) 1007 // --------------------------------------------------------------------------- 1008 1009 pub const our_kex_algos = [_][]const u8{ "mlkem768x25519-sha256", "curve25519-sha256", "curve25519-sha256@libssh.org" }; 1010 1011 // strict kex markers (Terrapin / CVE-2023-48795 mitigation). pseudo-algorithms 1012 // carried in the initial KEXINIT's kex list: we advertise the -s form, the 1013 // client advertises the -c form. they are never selected as an actual kex 1014 // algorithm because the matcher only picks from our_kex_algos. 1015 pub const kex_strict_server = "kex-strict-s-v00@openssh.com"; 1016 pub const kex_strict_client = "kex-strict-c-v00@openssh.com"; 1017 // the client asks for EXT_INFO after the initial NEWKEYS (RFC 8308) 1018 pub const ext_info_client = "ext-info-c"; 1019 1020 const MLKem768 = std.crypto.kem.ml_kem.MLKem768; 1021 const hybrid_client_blob_len = MLKem768.PublicKey.encoded_length + X25519.public_length; // 1216 1022 const hybrid_server_blob_len = MLKem768.ciphertext_length + X25519.public_length; // 1120 1023 pub const our_host_key_algos = [_][]const u8{"ssh-ed25519"}; 1024 pub const our_userauth_algos = [_][]const u8{ "ssh-ed25519", "rsa-sha2-512", "rsa-sha2-256" }; 1025 pub const our_ciphers = [_][]const u8{"chacha20-poly1305@openssh.com"}; 1026 const our_macs = [_][]const u8{}; // none — implicit in the AEAD cipher 1027 const our_compression = [_][]const u8{"none"}; 1028 1029 /// build a KEXINIT payload with the given algorithm name-lists 1030 pub fn buildKexInit( 1031 io: std.Io, 1032 allocator: std.mem.Allocator, 1033 kex_algos: []const []const u8, 1034 host_key_algos: []const []const u8, 1035 ciphers: []const []const u8, 1036 ) ![]u8 { 1037 var buf: std.ArrayList(u8) = .empty; 1038 errdefer buf.deinit(allocator); 1039 1040 try buf.append(allocator, SSH_MSG_KEXINIT); 1041 1042 var cookie: [16]u8 = undefined; 1043 io.random(&cookie); 1044 try buf.appendSlice(allocator, &cookie); 1045 1046 try writeNameList(&buf, allocator, kex_algos); 1047 try writeNameList(&buf, allocator, host_key_algos); 1048 try writeNameList(&buf, allocator, ciphers); // c->s 1049 try writeNameList(&buf, allocator, ciphers); // s->c 1050 try writeNameList(&buf, allocator, &our_macs); 1051 try writeNameList(&buf, allocator, &our_macs); 1052 try writeNameList(&buf, allocator, &our_compression); 1053 try writeNameList(&buf, allocator, &our_compression); 1054 try writeNameList(&buf, allocator, &.{}); // langs c->s 1055 try writeNameList(&buf, allocator, &.{}); // langs s->c 1056 try buf.append(allocator, 0); // first_kex_packet_follows = false 1057 try buf.appendSlice(allocator, &[_]u8{ 0, 0, 0, 0 }); // reserved 1058 1059 return try buf.toOwnedSlice(allocator); 1060 } 1061 1062 fn buildServerKexInit(io: std.Io, allocator: std.mem.Allocator) ![]u8 { 1063 return buildKexInit(io, allocator, &(our_kex_algos ++ [_][]const u8{kex_strict_server}), &our_host_key_algos, &our_ciphers); 1064 } 1065 1066 // the name-lists borrow from the KEXINIT payload 1067 const ParsedKexInit = struct { 1068 kex_algos: []const u8, 1069 host_key_algos: []const u8, 1070 cs_cipher: []const u8, 1071 sc_cipher: []const u8, 1072 first_kex_packet_follows: bool, 1073 }; 1074 1075 fn parseClientKexInit(payload: []const u8) !ParsedKexInit { 1076 if (payload.len < 1 + 16) return error.KexInitTruncated; 1077 if (payload[0] != SSH_MSG_KEXINIT) return error.UnexpectedMessage; 1078 1079 var reader = std.Io.Reader.fixed(payload[1 + 16 ..]); // skip type + cookie 1080 1081 const kex_algos = try takeString(&reader, max_name_list_len); 1082 const host_key_algos = try takeString(&reader, max_name_list_len); 1083 const cs_cipher = try takeString(&reader, max_name_list_len); 1084 const sc_cipher = try takeString(&reader, max_name_list_len); 1085 1086 // skip c->s mac, s->c mac, c->s compress, s->c compress, lang c->s, lang s->c 1087 for (0..6) |_| _ = try takeString(&reader, max_name_list_len); 1088 const first_kex_packet_follows = (try reader.takeByte()) != 0; 1089 _ = try reader.takeInt(u32, .big); // reserved 1090 1091 return .{ 1092 .kex_algos = kex_algos, 1093 .host_key_algos = host_key_algos, 1094 .cs_cipher = cs_cipher, 1095 .sc_cipher = sc_cipher, 1096 .first_kex_packet_follows = first_kex_packet_follows, 1097 }; 1098 } 1099 1100 // --------------------------------------------------------------------------- 1101 // KEX orchestration: KEXINIT → ECDH → NEWKEYS → key derivation 1102 // --------------------------------------------------------------------------- 1103 1104 fn runKex( 1105 io: std.Io, 1106 allocator: std.mem.Allocator, 1107 reader: *std.Io.Reader, 1108 writer: *std.Io.Writer, 1109 host_key: *const HostKey, 1110 client_version: []const u8, 1111 idle: *IdleState, 1112 ) !Conn { 1113 var seqs: PlainSeqs = .{}; 1114 const transport = KexTransport{ .plain = &seqs }; 1115 1116 // exchange KEXINITs 1117 const server_kex_init = try buildServerKexInit(io, allocator); 1118 defer allocator.free(server_kex_init); 1119 try transport.writePacket(io, writer, server_kex_init); 1120 1121 const client_kex_init = try transport.readPacket(allocator, reader, false); 1122 defer allocator.free(client_kex_init); 1123 1124 const parsed = try parseClientKexInit(client_kex_init); 1125 1126 // strict kex: when the client advertises it, its KEXINIT must be the 1127 // first packet, ignorable messages are banned until NEWKEYS, and both 1128 // seqnos reset to 0 after every NEWKEYS. 1129 const strict = firstCommonName(parsed.kex_algos, &.{kex_strict_client}) != null; 1130 if (strict and seqs.read != 1) return error.StrictKexViolation; 1131 const ext_info = firstCommonName(parsed.kex_algos, &.{ext_info_client}) != null; 1132 1133 var keys: SessionKeys = undefined; 1134 defer std.crypto.secureZero(u8, std.mem.asBytes(&keys)); 1135 const session_id = try exchangeKeys( 1136 io, 1137 allocator, 1138 reader, 1139 writer, 1140 transport, 1141 strict, 1142 host_key, 1143 client_version, 1144 client_kex_init, 1145 server_kex_init, 1146 &parsed, 1147 null, 1148 &keys, 1149 ); 1150 1151 // post-KEX everything is encrypted with chacha20-poly1305@openssh.com. 1152 // each cipher continues its own direction's count; the read side 1153 // includes any skipped IGNORE/DEBUG packets. 1154 var conn: Conn = .{ 1155 .io = io, 1156 .allocator = allocator, 1157 .reader = reader, 1158 .writer = writer, 1159 .cs_cipher = .init(&keys.cs_enc, if (strict) 0 else seqs.read), 1160 .sc_cipher = .init(&keys.sc_enc, if (strict) 0 else seqs.written), 1161 .rekey = .{ 1162 .host_key = host_key, 1163 .client_version = client_version, 1164 .session_id = session_id, 1165 .strict = strict, 1166 }, 1167 .idle = idle, 1168 }; 1169 if (ext_info) try sendExtInfo(&conn); 1170 return conn; 1171 } 1172 1173 // advertise server-sig-algs so clients will offer rsa-sha2 keys (RFC 8308 §3.1) 1174 fn sendExtInfo(conn: *Conn) !void { 1175 var buf: std.ArrayList(u8) = .empty; 1176 defer buf.deinit(conn.allocator); 1177 try buf.append(conn.allocator, SSH_MSG_EXT_INFO); 1178 try writeU32(&buf, conn.allocator, 1); // one extension 1179 try writeStringField(&buf, conn.allocator, "server-sig-algs"); 1180 try writeNameList(&buf, conn.allocator, &our_userauth_algos); 1181 try conn.writePacket(&.{buf.items}); 1182 } 1183 1184 /// everything needed to service a client-initiated rekey mid-session. 1185 const RekeyState = struct { 1186 host_key: *const HostKey, 1187 client_version: []const u8, 1188 session_id: [Sha256.digest_length]u8, 1189 strict: bool, 1190 }; 1191 1192 // service a rekey whose triggering KEXINIT payload has just been read: run 1193 // the whole exchange under the current keys, then swap the new keys into 1194 // both ciphers in place. 1195 fn runRekey(conn: *Conn, client_kex_init: []const u8) !void { 1196 const parsed = try parseClientKexInit(client_kex_init); 1197 1198 // the exchange reads and writes through the ciphers directly 1199 conn.idle.waiting.store(true, .release); 1200 defer conn.idle.waiting.store(false, .release); 1201 1202 const server_kex_init = try buildServerKexInit(conn.io, conn.allocator); 1203 defer conn.allocator.free(server_kex_init); 1204 try conn.sc_cipher.writePacket(conn.io, conn.writer, &.{server_kex_init}); 1205 1206 var keys: SessionKeys = undefined; 1207 defer std.crypto.secureZero(u8, std.mem.asBytes(&keys)); 1208 _ = try exchangeKeys( 1209 conn.io, 1210 conn.allocator, 1211 conn.reader, 1212 conn.writer, 1213 .{ .encrypted = .{ .cs = &conn.cs_cipher, .sc = &conn.sc_cipher } }, 1214 false, // strict kex message rules apply to the initial exchange only 1215 conn.rekey.host_key, 1216 conn.rekey.client_version, 1217 client_kex_init, 1218 server_kex_init, 1219 &parsed, 1220 &conn.rekey.session_id, 1221 &keys, 1222 ); 1223 1224 // seqnos continue across a rekey unless strict kex was negotiated, 1225 // which resets them after every NEWKEYS 1226 conn.cs_cipher = .init(&keys.cs_enc, if (conn.rekey.strict) 0 else conn.cs_cipher.seq); 1227 conn.sc_cipher = .init(&keys.sc_enc, if (conn.rekey.strict) 0 else conn.sc_cipher.seq); 1228 } 1229 1230 // the KEX core shared by the initial exchange and rekeys: pick algorithms, 1231 // run the (hybrid) ECDH round trip, exchange NEWKEYS, derive keys. both 1232 // KEXINIT payloads have already been exchanged by the caller, which also owns 1233 // `parsed`; the client's raw payload comes along too because the exchange hash 1234 // covers it verbatim. session_id is null on the initial exchange (where it 1235 // becomes the exchange hash) and the original session id on a rekey. fills 1236 // `keys` and returns the exchange hash. 1237 fn exchangeKeys( 1238 io: std.Io, 1239 allocator: std.mem.Allocator, 1240 reader: *std.Io.Reader, 1241 writer: *std.Io.Writer, 1242 transport: KexTransport, 1243 strict: bool, 1244 host_key: *const HostKey, 1245 client_version: []const u8, 1246 client_kex_init: []const u8, 1247 server_kex_init: []const u8, 1248 parsed: *const ParsedKexInit, 1249 session_id: ?*const [Sha256.digest_length]u8, 1250 keys: *SessionKeys, 1251 ) ![Sha256.digest_length]u8 { 1252 const kex_algo = firstCommonName(parsed.kex_algos, &our_kex_algos) orelse return error.NoCommonKexAlgorithm; 1253 if (firstCommonName(parsed.host_key_algos, &our_host_key_algos) == null) return error.NoCommonHostKeyAlgorithm; 1254 if (firstCommonName(parsed.cs_cipher, &our_ciphers) == null) return error.NoCommonCipher; 1255 if (firstCommonName(parsed.sc_cipher, &our_ciphers) == null) return error.NoCommonCipher; 1256 const hybrid = std.mem.eql(u8, kex_algo, "mlkem768x25519-sha256"); 1257 1258 // a client may follow its KEXINIT with a kex packet for its guess. the 1259 // guess is right only when both sides' first kex and host key algorithms 1260 // match (RFC 4253 §7.1) — not when the client's first choice merely 1261 // happens to be kex_algo, so this compares against our list. a client 1262 // whose guess was wrong re-sends an init for the negotiated method. 1263 if (parsed.first_kex_packet_follows) { 1264 var kex_iter = std.mem.splitScalar(u8, parsed.kex_algos, ','); 1265 var host_key_iter = std.mem.splitScalar(u8, parsed.host_key_algos, ','); 1266 const guessed_right = std.mem.eql(u8, kex_iter.first(), our_kex_algos[0]) and 1267 std.mem.eql(u8, host_key_iter.first(), our_host_key_algos[0]); 1268 if (!guessed_right) { 1269 const wrong_guess = try transport.readPacket(allocator, reader, strict); 1270 allocator.free(wrong_guess); 1271 } 1272 } 1273 1274 // receive KEX_ECDH_INIT (mlkem768x25519 reuses message code 30 — same 1275 // wire shape, only the string size differs). 1276 const ecdh_init = try transport.readPacket(allocator, reader, strict); 1277 defer allocator.free(ecdh_init); 1278 if (ecdh_init[0] != SSH_MSG_KEX_ECDH_INIT) return error.UnexpectedMessage; 1279 1280 var ecdh_init_reader = std.Io.Reader.fixed(ecdh_init[1..]); 1281 const expected_client_len: u32 = if (hybrid) hybrid_client_blob_len else X25519.public_length; 1282 const client_blob = try takeString(&ecdh_init_reader, expected_client_len); 1283 if (client_blob.len != expected_client_len) return error.InvalidEphemeralKey; 1284 1285 // derive server reply blob (S_REPLY) + shared secret K. 1286 // ECDH: server_blob = X25519 server pub (32B); K = X25519(s, c_pub). 1287 // hybrid: server_blob = MLKEM ciphertext (1088B) || X25519 server pub (32B); 1288 // K = SHA-256(K_MLKEM || K_X25519). 1289 var server_blob_buf: [hybrid_server_blob_len]u8 = undefined; 1290 var k: [Sha256.digest_length]u8 = undefined; 1291 defer std.crypto.secureZero(u8, &k); 1292 const server_blob: []const u8 = blk: { 1293 const x25519_offset: usize = if (hybrid) MLKem768.PublicKey.encoded_length else 0; 1294 var x25519_client_pub: [X25519.public_length]u8 = undefined; 1295 @memcpy(&x25519_client_pub, client_blob[x25519_offset..]); 1296 var server_kp = X25519.KeyPair.generate(io); 1297 defer std.crypto.secureZero(u8, &server_kp.secret_key); 1298 var x25519_shared = try X25519.scalarmult(server_kp.secret_key, x25519_client_pub); 1299 defer std.crypto.secureZero(u8, &x25519_shared); 1300 1301 if (!hybrid) { 1302 server_blob_buf[0..X25519.public_length].* = server_kp.public_key; 1303 k = x25519_shared; 1304 break :blk server_blob_buf[0..X25519.public_length]; 1305 } 1306 1307 var pq_pub_bytes: [MLKem768.PublicKey.encoded_length]u8 = undefined; 1308 @memcpy(&pq_pub_bytes, client_blob[0..MLKem768.PublicKey.encoded_length]); 1309 const pq_pub = try MLKem768.PublicKey.fromBytes(&pq_pub_bytes); 1310 var encap = pq_pub.encaps(io); 1311 defer std.crypto.secureZero(u8, &encap.shared_secret); 1312 1313 server_blob_buf[0..MLKem768.ciphertext_length].* = encap.ciphertext; 1314 server_blob_buf[MLKem768.ciphertext_length..].* = server_kp.public_key; 1315 1316 var h = Sha256.init(.{}); 1317 defer std.crypto.secureZero(u8, std.mem.asBytes(&h)); 1318 h.update(&encap.shared_secret); 1319 h.update(&x25519_shared); 1320 h.final(&k); 1321 break :blk &server_blob_buf; 1322 }; 1323 1324 // build host key blob (K_S) 1325 var host_key_blob: std.ArrayList(u8) = .empty; 1326 defer host_key_blob.deinit(allocator); 1327 try host_key.appendPublicBlob(&host_key_blob, allocator); 1328 1329 // build exchange hash input and compute H 1330 const exchange_hash = try computeExchangeHash( 1331 allocator, 1332 client_version, 1333 server_version, 1334 client_kex_init, 1335 server_kex_init, 1336 host_key_blob.items, 1337 client_blob, 1338 server_blob, 1339 &k, 1340 hybrid, 1341 ); 1342 1343 // sign H with the host key, format as ssh signature blob 1344 var signature_blob: std.ArrayList(u8) = .empty; 1345 defer signature_blob.deinit(allocator); 1346 try host_key.appendSignatureBlob(&signature_blob, allocator, &exchange_hash); 1347 1348 // build & send KEX_ECDH_REPLY (msg code 31 reused as KEX_HYBRID_REPLY) 1349 var reply: std.ArrayList(u8) = .empty; 1350 defer reply.deinit(allocator); 1351 try reply.append(allocator, SSH_MSG_KEX_ECDH_REPLY); 1352 try writeStringField(&reply, allocator, host_key_blob.items); 1353 try writeStringField(&reply, allocator, server_blob); 1354 try writeStringField(&reply, allocator, signature_blob.items); 1355 try transport.writePacket(io, writer, reply.items); 1356 1357 // NEWKEYS — both sides switch to the new keys after this is sent and 1358 // the peer's NEWKEYS is received. 1359 try transport.writePacket(io, writer, &[_]u8{SSH_MSG_NEWKEYS}); 1360 1361 const peer_newkeys = try transport.readPacket(allocator, reader, strict); 1362 defer allocator.free(peer_newkeys); 1363 if (peer_newkeys[0] != SSH_MSG_NEWKEYS) return error.UnexpectedMessage; 1364 1365 // derive session keys per RFC 4253 §7.2. only the encrypt keys are 1366 // needed for chacha20-poly1305 (no separate MAC/IV). 1367 try deriveSessionKeys(allocator, &k, &exchange_hash, if (session_id) |sid| sid else &exchange_hash, keys, hybrid); 1368 return exchange_hash; 1369 } 1370 1371 // --------------------------------------------------------------------------- 1372 // exchange hash (RFC 4253 §8, RFC 5656 §4) 1373 // --------------------------------------------------------------------------- 1374 1375 pub fn computeExchangeHash( 1376 allocator: std.mem.Allocator, 1377 client_version: []const u8, 1378 server_version_str: []const u8, 1379 client_kex_init: []const u8, 1380 server_kex_init: []const u8, 1381 host_key_blob: []const u8, 1382 client_ephemeral: []const u8, 1383 server_ephemeral: []const u8, 1384 shared_secret: []const u8, 1385 /// curve25519-sha256 encodes K as mpint; mlkem768x25519-sha256 encodes it 1386 /// as a plain SSH string (length-prefixed bytes). 1387 k_is_string: bool, 1388 ) ![Sha256.digest_length]u8 { 1389 var buf: std.ArrayList(u8) = .empty; 1390 defer buf.deinit(allocator); 1391 defer std.crypto.secureZero(u8, buf.items); 1392 // reserved up front so a reallocation can't leave K behind 1393 try buf.ensureTotalCapacityPrecise(allocator, 8 * 4 + 1 + client_version.len + server_version_str.len + 1394 client_kex_init.len + server_kex_init.len + host_key_blob.len + client_ephemeral.len + 1395 server_ephemeral.len + shared_secret.len); 1396 1397 try writeStringField(&buf, allocator, client_version); 1398 try writeStringField(&buf, allocator, server_version_str); 1399 try writeStringField(&buf, allocator, client_kex_init); 1400 try writeStringField(&buf, allocator, server_kex_init); 1401 try writeStringField(&buf, allocator, host_key_blob); 1402 try writeStringField(&buf, allocator, client_ephemeral); 1403 try writeStringField(&buf, allocator, server_ephemeral); 1404 if (k_is_string) { 1405 try writeStringField(&buf, allocator, shared_secret); 1406 } else { 1407 try writeMpint(&buf, allocator, shared_secret); 1408 } 1409 1410 var hasher = Sha256.init(.{}); 1411 defer std.crypto.secureZero(u8, std.mem.asBytes(&hasher)); 1412 hasher.update(buf.items); 1413 return hasher.finalResult(); 1414 } 1415 1416 // --------------------------------------------------------------------------- 1417 // key derivation (RFC 4253 §7.2) 1418 // --------------------------------------------------------------------------- 1419 1420 // chacha20-poly1305@openssh.com wants 64 bytes per direction (32-byte main key 1421 // + 32-byte header key); SHA256 produces 32, so each encrypt key is two hash 1422 // blocks chained per RFC 4253. 1423 pub const SessionKeys = struct { 1424 cs_enc: [64]u8, 1425 sc_enc: [64]u8, 1426 }; 1427 1428 pub fn deriveSessionKeys( 1429 allocator: std.mem.Allocator, 1430 shared_secret: []const u8, 1431 exchange_hash: []const u8, 1432 session_id: []const u8, 1433 out: *SessionKeys, 1434 /// see computeExchangeHash — must match the KEX algorithm's K encoding. 1435 k_is_string: bool, 1436 ) !void { 1437 // pre-build the K || H prefix once; reused for every derivation 1438 var prefix: std.ArrayList(u8) = .empty; 1439 defer prefix.deinit(allocator); 1440 defer std.crypto.secureZero(u8, prefix.items); 1441 // reserved up front so a reallocation can't leave K behind 1442 try prefix.ensureTotalCapacityPrecise(allocator, 4 + 1 + shared_secret.len + exchange_hash.len); 1443 if (k_is_string) { 1444 try writeStringField(&prefix, allocator, shared_secret); 1445 } else { 1446 try writeMpint(&prefix, allocator, shared_secret); 1447 } 1448 try prefix.appendSlice(allocator, exchange_hash); 1449 1450 deriveKey(prefix.items, 'C', session_id, &out.cs_enc); 1451 deriveKey(prefix.items, 'D', session_id, &out.sc_enc); 1452 } 1453 1454 fn deriveKey( 1455 prefix: []const u8, // K || H, already encoded 1456 letter: u8, 1457 session_id: []const u8, 1458 out: *[2 * Sha256.digest_length]u8, 1459 ) void { 1460 // a finished context still holds its digest and last input block 1461 // K_1 = HASH(K || H || letter || session_id) 1462 var first = Sha256.init(.{}); 1463 defer std.crypto.secureZero(u8, std.mem.asBytes(&first)); 1464 first.update(prefix); 1465 first.update(&.{letter}); 1466 first.update(session_id); 1467 first.final(out[0..Sha256.digest_length]); 1468 1469 // K_2 = HASH(K || H || K_1) 1470 var second = Sha256.init(.{}); 1471 defer std.crypto.secureZero(u8, std.mem.asBytes(&second)); 1472 second.update(prefix); 1473 second.update(out[0..Sha256.digest_length]); 1474 second.final(out[Sha256.digest_length..]); 1475 } 1476 1477 // --------------------------------------------------------------------------- 1478 // chacha20-poly1305@openssh.com packet codec 1479 // --------------------------------------------------------------------------- 1480 // 1481 // per openssh's PROTOCOL.chacha20poly1305: 1482 // K_2 = first 32 bytes of key material — encrypts the packet body 1483 // K_1 = next 32 bytes — encrypts the 4-byte length field 1484 // nonce = 64-bit big-endian sequence number 1485 // body = chacha20(K_2, nonce, counter=1) XOR plaintext_body 1486 // length = chacha20(K_1, nonce, counter=0) XOR length_uint32_be 1487 // mac = poly1305(poly_key, encrypted_length || encrypted_body) 1488 // where poly_key = chacha20(K_2, nonce, counter=0)[0..32] 1489 // 1490 // padding is computed on the body alone (padding_length byte + payload + 1491 // padding) — the 4-byte length field is excluded from alignment. body must 1492 // be a multiple of 8 bytes; minimum padding 4 bytes. 1493 1494 pub const Cipher = struct { 1495 main_key: [32]u8, // K_2 1496 header_key: [32]u8, // K_1 1497 // wider than the 32-bit wire seqno, so a peer that never rekeys fails the 1498 // mac at 2^32 packets instead of wrapping into nonce reuse 1499 seq: u64, 1500 1501 pub fn init(key_material: *const [64]u8, initial_seq: u64) Cipher { 1502 return .{ 1503 .main_key = key_material[0..32].*, 1504 .header_key = key_material[32..64].*, 1505 .seq = initial_seq, 1506 }; 1507 } 1508 1509 fn makeNonce(seq: u64) [8]u8 { 1510 var nonce: [8]u8 = undefined; 1511 std.mem.writeInt(u64, &nonce, seq, .big); 1512 return nonce; 1513 } 1514 1515 fn bodyLength(self: *const Cipher, enc_length: *const [4]u8) !u32 { 1516 var plain: [4]u8 = undefined; 1517 ChaCha20.xor(&plain, enc_length, 0, self.header_key, makeNonce(self.seq)); 1518 const len = std.mem.readInt(u32, &plain, .big); 1519 if (len < 8 or len > max_packet_len or len % 8 != 0) return error.InvalidPacketLength; 1520 return len; 1521 } 1522 1523 fn peekPacket(self: *const Cipher, reader: *std.Io.Reader) !void { 1524 const len = 4 + (try self.bodyLength(try reader.peekArray(4))) + Poly1305.mac_length; 1525 if (len > reader.buffer.len) return error.ReadBufferTooSmall; 1526 _ = try reader.peek(len); 1527 } 1528 1529 fn hasBufferedPacket(self: *const Cipher, reader: *std.Io.Reader) !bool { 1530 const bytes = reader.buffered(); 1531 if (bytes.len < 4) return false; 1532 return bytes.len >= 4 + (try self.bodyLength(bytes[0..4])) + Poly1305.mac_length; 1533 } 1534 1535 /// the payload is the concatenation of `parts` 1536 pub fn writePacket( 1537 self: *Cipher, 1538 io: std.Io, 1539 writer: *std.Io.Writer, 1540 parts: []const []const u8, 1541 ) !void { 1542 var payload_len: usize = 0; 1543 for (parts) |part| payload_len += part.len; 1544 1545 const block: usize = 8; 1546 const initial_pad = block - ((1 + payload_len) % block); 1547 const padding_len: u8 = @intCast(if (initial_pad < 4) initial_pad + block else initial_pad); 1548 const body_len = 1 + payload_len + padding_len; 1549 if (body_len > max_packet_len) return error.PacketTooLarge; 1550 1551 const nonce = makeNonce(self.seq); 1552 1553 // encrypted length || body || mac, contiguous so the packet goes out 1554 // in one write. stack-allocated to avoid a heap alloc on every packet. 1555 var packet_buf: [packet_buffer_size]u8 = undefined; 1556 const packet = packet_buf[0 .. 4 + body_len + Poly1305.mac_length]; 1557 const enc_length = packet[0..4]; 1558 const body = packet[4..][0..body_len]; 1559 1560 // plaintext body = padding_length || payload || random padding 1561 body[0] = padding_len; 1562 var end: usize = 1; 1563 for (parts) |part| { 1564 @memcpy(body[end..][0..part.len], part); 1565 end += part.len; 1566 } 1567 io.random(body[end..]); 1568 1569 // encrypt body in place with counter=1 1570 ChaCha20.xor(body, body, 1, self.main_key, nonce); 1571 1572 // encrypt length field with header key, counter=0 1573 std.mem.writeInt(u32, enc_length, @intCast(body_len), .big); 1574 ChaCha20.xor(enc_length, enc_length, 0, self.header_key, nonce); 1575 1576 // poly1305 key = first 32 bytes of chacha20(K_2, nonce, counter=0) 1577 var poly_key: [Poly1305.key_length]u8 = undefined; 1578 ChaCha20.stream(&poly_key, 0, self.main_key, nonce); 1579 1580 // mac over encrypted_length || encrypted_body 1581 var poly = Poly1305.init(&poly_key); 1582 poly.update(packet[0 .. 4 + body_len]); 1583 poly.final(packet[4 + body_len ..][0..Poly1305.mac_length]); 1584 1585 try writer.writeAll(packet); 1586 try writer.flush(); 1587 1588 self.seq += 1; 1589 } 1590 1591 pub fn readPacket( 1592 self: *Cipher, 1593 allocator: std.mem.Allocator, 1594 reader: *std.Io.Reader, 1595 ) ![]u8 { 1596 const nonce = makeNonce(self.seq); 1597 1598 var enc_length: [4]u8 = undefined; 1599 try reader.readSliceAll(&enc_length); 1600 1601 const body_len = try self.bodyLength(&enc_length); 1602 1603 // the body allocation becomes the returned payload, so a packet only 1604 // ever costs one allocation 1605 const body = try allocator.alloc(u8, body_len); 1606 errdefer allocator.free(body); 1607 try reader.readSliceAll(body); 1608 1609 var tag_recv: [Poly1305.mac_length]u8 = undefined; 1610 try reader.readSliceAll(&tag_recv); 1611 1612 var poly_key: [Poly1305.key_length]u8 = undefined; 1613 ChaCha20.stream(&poly_key, 0, self.main_key, nonce); 1614 1615 var poly = Poly1305.init(&poly_key); 1616 poly.update(&enc_length); 1617 poly.update(body); 1618 var tag_computed: [Poly1305.mac_length]u8 = undefined; 1619 poly.final(&tag_computed); 1620 if (!std.crypto.timing_safe.eql([Poly1305.mac_length]u8, tag_recv, tag_computed)) { 1621 return error.MacVerificationFailed; 1622 } 1623 1624 // decrypt the body in place 1625 ChaCha20.xor(body, body, 1, self.main_key, nonce); 1626 1627 const padding_len = body[0]; 1628 if (padding_len < 4 or 1 + @as(u32, padding_len) > body_len) return error.InvalidPadding; 1629 const payload_len = body_len - 1 - @as(u32, padding_len); 1630 // a payload starts with its message type 1631 if (payload_len == 0) return error.EmptyPacket; 1632 1633 // shift the payload over the padding_length byte, then release the 1634 // trailing padding (caller owns the result) 1635 std.mem.copyForwards(u8, body[0..payload_len], body[1 .. 1 + payload_len]); 1636 const payload = try allocator.realloc(body, payload_len); 1637 1638 self.seq += 1; 1639 return payload; 1640 } 1641 }; 1642 1643 // --------------------------------------------------------------------------- 1644 // post-KEX: service request + user authentication (RFC 4252) 1645 // --------------------------------------------------------------------------- 1646 1647 /// "SHA256:" (7 bytes) + base64-no-padding of a 32-byte SHA256 digest 1648 /// (43 bytes) = 50 bytes. matches what openssh's client logs as 1649 /// `Offering public key: … SHA256:…`. 1650 pub const fingerprint_len = 50; 1651 1652 /// hash the SSH wire-format pubkey blob (`string algo` + `string raw_key`) 1653 /// the same way openssh does for `ssh-keygen -lf` / authorized-key logs. 1654 pub fn formatFingerprint(pubkey_blob: []const u8) [fingerprint_len]u8 { 1655 var digest: [Sha256.digest_length]u8 = undefined; 1656 Sha256.hash(pubkey_blob, &digest, .{}); 1657 1658 var out: [fingerprint_len]u8 = undefined; 1659 @memcpy(out[0..7], "SHA256:"); 1660 const encoded = std.base64.standard_no_pad.Encoder.encode(out[7..], &digest); 1661 std.debug.assert(encoded.len == fingerprint_len - 7); 1662 return out; 1663 } 1664 1665 fn runAuth(conn: *Conn) ![fingerprint_len]u8 { 1666 const allocator = conn.allocator; 1667 1668 // step 1: service request for ssh-userauth → service accept 1669 { 1670 const req = try readSessionPacket(conn); 1671 defer allocator.free(req); 1672 if (req[0] != SSH_MSG_SERVICE_REQUEST) return error.UnexpectedMessage; 1673 1674 var req_reader = std.Io.Reader.fixed(req[1..]); 1675 const service = try takeString(&req_reader, 64); 1676 if (!std.mem.eql(u8, service, "ssh-userauth")) return error.UnsupportedService; 1677 1678 var accept: std.ArrayList(u8) = .empty; 1679 defer accept.deinit(allocator); 1680 try accept.append(allocator, SSH_MSG_SERVICE_ACCEPT); 1681 try writeStringField(&accept, allocator, "ssh-userauth"); 1682 try conn.writePacket(&.{accept.items}); 1683 } 1684 1685 // step 2: USERAUTH loop until SUCCESS. accept any supported key whose 1686 // signature verifies against the offered pubkey. 1687 var auth_attempts: u32 = 0; 1688 while (true) { 1689 const req = try readSessionPacket(conn); 1690 defer allocator.free(req); 1691 if (req[0] != SSH_MSG_USERAUTH_REQUEST) return error.UnexpectedMessage; 1692 1693 // every request counts, probes included, so a client can't loop here 1694 // forever 1695 if (auth_attempts >= max_auth_attempts) return error.TooManyAuthAttempts; 1696 auth_attempts += 1; 1697 1698 var req_reader = std.Io.Reader.fixed(req[1..]); 1699 const user_name = try takeString(&req_reader, 256); 1700 const service_name = try takeString(&req_reader, 64); 1701 const method = try takeString(&req_reader, 64); 1702 1703 // RFC 4252 §5: the server must verify the requested service 1704 if (!std.mem.eql(u8, service_name, "ssh-connection")) { 1705 try sendUserauthFailure(conn); 1706 continue; 1707 } 1708 1709 if (!std.mem.eql(u8, method, "publickey")) { 1710 try sendUserauthFailure(conn); 1711 continue; 1712 } 1713 1714 const has_signature = (try req_reader.takeByte()) != 0; 1715 const algo = try takeString(&req_reader, 64); 1716 const pubkey_blob = try takeString(&req_reader, 4096); 1717 1718 if (firstCommonName(algo, &our_userauth_algos) == null) { 1719 try sendUserauthFailure(conn); 1720 continue; 1721 } 1722 1723 if (!has_signature) { 1724 // probe — tell the client this key is acceptable so it'll send 1725 // the signed version next. 1726 var pk_ok: std.ArrayList(u8) = .empty; 1727 defer pk_ok.deinit(allocator); 1728 try pk_ok.append(allocator, SSH_MSG_USERAUTH_PK_OK); 1729 try writeStringField(&pk_ok, allocator, algo); 1730 try writeStringField(&pk_ok, allocator, pubkey_blob); 1731 try conn.writePacket(&.{pk_ok.items}); 1732 continue; 1733 } 1734 1735 // has signature — verify it 1736 const signature_blob = try takeString(&req_reader, 1024); 1737 1738 const ok = verifyUserauthSignature( 1739 allocator, 1740 &conn.rekey.session_id, 1741 user_name, 1742 service_name, 1743 algo, 1744 pubkey_blob, 1745 signature_blob, 1746 ) catch |err| switch (err) { 1747 error.OutOfMemory => return err, 1748 // a malformed key or signature blob 1749 else => false, 1750 }; 1751 1752 if (!ok) { 1753 try sendUserauthFailure(conn); 1754 continue; 1755 } 1756 1757 try conn.writePacket(&.{&[_]u8{SSH_MSG_USERAUTH_SUCCESS}}); 1758 return formatFingerprint(pubkey_blob); 1759 } 1760 } 1761 1762 fn sendUserauthFailure(conn: *Conn) !void { 1763 var buf: std.ArrayList(u8) = .empty; 1764 defer buf.deinit(conn.allocator); 1765 try buf.append(conn.allocator, SSH_MSG_USERAUTH_FAILURE); 1766 try writeNameList(&buf, conn.allocator, &.{"publickey"}); // allowed methods 1767 try buf.append(conn.allocator, 0); // partial_success = false 1768 try conn.writePacket(&.{buf.items}); 1769 } 1770 1771 /// append the canonical publickey-signed-data bytes (RFC 4252 §7) to `buf`. 1772 /// used by the server to recompute the signed input for verification 1773 pub fn appendPublickeySignedData( 1774 buf: *std.ArrayList(u8), 1775 allocator: std.mem.Allocator, 1776 session_id: []const u8, 1777 user_name: []const u8, 1778 service_name: []const u8, 1779 algo: []const u8, 1780 pubkey_blob: []const u8, 1781 ) !void { 1782 try writeStringField(buf, allocator, session_id); 1783 try buf.append(allocator, SSH_MSG_USERAUTH_REQUEST); 1784 try writeStringField(buf, allocator, user_name); 1785 try writeStringField(buf, allocator, service_name); 1786 try writeStringField(buf, allocator, "publickey"); 1787 try buf.append(allocator, 1); 1788 try writeStringField(buf, allocator, algo); 1789 try writeStringField(buf, allocator, pubkey_blob); 1790 } 1791 1792 // build the bytes a publickey signature is computed over (RFC 4252 §7) and 1793 // verify the supplied signature against them. 1794 fn verifyUserauthSignature( 1795 allocator: std.mem.Allocator, 1796 session_id: *const [Sha256.digest_length]u8, 1797 user_name: []const u8, 1798 service_name: []const u8, 1799 algo: []const u8, 1800 pubkey_blob: []const u8, 1801 signature_blob: []const u8, 1802 ) !bool { 1803 var signed: std.ArrayList(u8) = .empty; 1804 defer signed.deinit(allocator); 1805 try appendPublickeySignedData(&signed, allocator, session_id, user_name, service_name, algo, pubkey_blob); 1806 1807 if (std.mem.eql(u8, algo, "ssh-ed25519")) return verifyEd25519(pubkey_blob, signature_blob, signed.items); 1808 if (std.mem.eql(u8, algo, "rsa-sha2-512")) return verifyRsa(Sha512, algo, pubkey_blob, signature_blob, signed.items); 1809 if (std.mem.eql(u8, algo, "rsa-sha2-256")) return verifyRsa(Sha256, algo, pubkey_blob, signature_blob, signed.items); 1810 return false; 1811 } 1812 1813 fn verifyEd25519(pubkey_blob: []const u8, signature_blob: []const u8, signed: []const u8) !bool { 1814 // parse pubkey_blob: string "ssh-ed25519" || string raw_pubkey 1815 var pubkey_reader = std.Io.Reader.fixed(pubkey_blob); 1816 const pk_algo = try takeString(&pubkey_reader, 64); 1817 if (!std.mem.eql(u8, pk_algo, "ssh-ed25519")) return false; 1818 const raw_pubkey = try takeString(&pubkey_reader, 64); 1819 if (raw_pubkey.len != Ed25519.PublicKey.encoded_length) return false; 1820 1821 // parse signature_blob: string "ssh-ed25519" || string raw_signature 1822 var sig_reader = std.Io.Reader.fixed(signature_blob); 1823 const sig_algo = try takeString(&sig_reader, 64); 1824 if (!std.mem.eql(u8, sig_algo, "ssh-ed25519")) return false; 1825 const raw_sig = try takeString(&sig_reader, Ed25519.Signature.encoded_length); 1826 if (raw_sig.len != Ed25519.Signature.encoded_length) return false; 1827 1828 var pubkey_bytes: [Ed25519.PublicKey.encoded_length]u8 = undefined; 1829 @memcpy(&pubkey_bytes, raw_pubkey); 1830 var sig_bytes: [Ed25519.Signature.encoded_length]u8 = undefined; 1831 @memcpy(&sig_bytes, raw_sig); 1832 1833 const pk = Ed25519.PublicKey.fromBytes(pubkey_bytes) catch return false; 1834 const sig = Ed25519.Signature.fromBytes(sig_bytes); 1835 sig.verify(signed, pk) catch return false; 1836 return true; 1837 } 1838 1839 fn verifyRsa(comptime Hash: type, algo: []const u8, pubkey_blob: []const u8, signature_blob: []const u8, signed: []const u8) !bool { 1840 // parse pubkey_blob: string "ssh-rsa" || mpint e || mpint n 1841 var pubkey_reader = std.Io.Reader.fixed(pubkey_blob); 1842 if (!std.mem.eql(u8, try takeString(&pubkey_reader, 64), "ssh-rsa")) return false; 1843 const e = std.mem.trimStart(u8, try takeString(&pubkey_reader, 1024), &.{0}); 1844 const n = std.mem.trimStart(u8, try takeString(&pubkey_reader, 1024), &.{0}); 1845 1846 // parse signature_blob: string algo || string sig 1847 var sig_reader = std.Io.Reader.fixed(signature_blob); 1848 if (!std.mem.eql(u8, try takeString(&sig_reader, 64), algo)) return false; 1849 const sig = try takeString(&sig_reader, 1024); 1850 if (sig.len != n.len) return false; 1851 1852 const pk = rsa.PublicKey.fromBytes(e, n) catch return false; 1853 switch (n.len) { 1854 inline 256, 384, 512 => |len| { 1855 rsa.PKCS1v1_5Signature.verify(len, sig[0..len].*, signed, pk, Hash) catch return false; 1856 return true; 1857 }, 1858 else => return false, 1859 } 1860 } 1861 1862 // --------------------------------------------------------------------------- 1863 // connection layer (RFC 4254): channels, requests, data, flow control 1864 // --------------------------------------------------------------------------- 1865 1866 const Channel = struct { 1867 local_id: u32, 1868 remote_id: u32, 1869 local_window: u32, // bytes peer may still send us before we adjust 1870 remote_window: u32, // bytes we may still send to peer before they adjust 1871 max_packet: u32, // max CHANNEL_DATA payload the peer accepts in one packet 1872 pty: ?PtySize = null, 1873 // value of GIT_PROTOCOL, the one env variable we keep 1874 git_protocol_buf: [64]u8 = undefined, 1875 git_protocol_len: ?usize = null, 1876 }; 1877 1878 pub const PtySize = struct { width_cells: u16, height_cells: u16 }; 1879 1880 // take the uint32 width/height cell counts of a pty-req or window-change, 1881 // bounded before either initial rendering or a resize can allocate grids. 1882 // keep zero dimensions intact (unspecified at startup, minimized on resize). 1883 fn takePtySize(r: *std.Io.Reader) !PtySize { 1884 const width = @min(try r.takeInt(u32, .big), max_pty_width); 1885 const height = @min(try r.takeInt(u32, .big), max_pty_height); 1886 return .{ 1887 .width_cells = @intCast(width), 1888 .height_cells = @intCast(height), 1889 }; 1890 } 1891 1892 fn runChannelLayer( 1893 conn: *Conn, 1894 fingerprint: *const [fingerprint_len]u8, 1895 handler: anytype, 1896 ) !void { 1897 const allocator = conn.allocator; 1898 var channel: ?Channel = null; 1899 1900 while (true) { 1901 const packet = try readSessionPacket(conn); 1902 defer allocator.free(packet); 1903 const msg_type = packet[0]; 1904 1905 switch (msg_type) { 1906 SSH_MSG_GLOBAL_REQUEST => try handleGlobalRequest(conn, packet), 1907 1908 SSH_MSG_CHANNEL_OPEN => { 1909 channel = try handleChannelOpen(conn, packet, channel != null) orelse continue; 1910 }, 1911 1912 SSH_MSG_CHANNEL_REQUEST => { 1913 const ch = if (channel) |*c| c else continue; 1914 const start_request = try handleChannelRequest(conn, ch, packet); 1915 // the request borrows from the packet, which outlives the session 1916 if (start_request) |request| { 1917 // any key authenticates, so the deadline holds until here 1918 conn.idle.session_started.store(true, .release); 1919 var sess = SessionCtx{ 1920 .conn = conn, 1921 .channel = ch, 1922 .fingerprint = fingerprint.*, 1923 }; 1924 defer sess.deinit(); 1925 handler.handleSession(&sess, request) catch |session_err| { 1926 // try to send a non-zero exit status before closing 1927 sess.exit(1) catch {}; 1928 return sess.underlyingError(session_err); 1929 }; 1930 if (!sess.closed) try sess.exit(0); 1931 return; 1932 } 1933 }, 1934 1935 SSH_MSG_CHANNEL_WINDOW_ADJUST => { 1936 const ch = if (channel) |*c| c else continue; 1937 try handleWindowAdjust(ch, packet); 1938 }, 1939 1940 SSH_MSG_CHANNEL_DATA, SSH_MSG_CHANNEL_EXTENDED_DATA => { 1941 const ch = if (channel) |*c| c else continue; 1942 // before shell/exec the client shouldn't be sending data, but 1943 // some clients are chatty; discard and refill window. nothing 1944 // is buffered yet, so the whole window is available to credit. 1945 try discardChannelData(ch, packet, msg_type == SSH_MSG_CHANNEL_EXTENDED_DATA); 1946 try maybeRefillRecvWindow(conn, ch, initial_recv_window); 1947 }, 1948 1949 SSH_MSG_CHANNEL_EOF => { 1950 if (channel) |*c| try parseChannelId(packet, c.local_id); 1951 }, 1952 1953 SSH_MSG_CHANNEL_CLOSE => { 1954 if (channel) |*c| { 1955 try parseChannelId(packet, c.local_id); 1956 try sendChannelMessage(conn, c, SSH_MSG_CHANNEL_CLOSE); 1957 drainConnection(conn); 1958 } 1959 return; 1960 }, 1961 1962 // RFC 4252 §5.1: silently ignored once authenticated 1963 SSH_MSG_USERAUTH_REQUEST => {}, 1964 else => try sendUnimplemented(conn), 1965 } 1966 } 1967 } 1968 1969 fn handleGlobalRequest(conn: *Conn, packet: []const u8) !void { 1970 // byte SSH_MSG_GLOBAL_REQUEST 1971 // string request_name 1972 // boolean want_reply 1973 // …request-specific data we ignore 1974 var r = std.Io.Reader.fixed(packet[1..]); 1975 _ = try takeString(&r, 256); 1976 const want_reply = (try r.takeByte()) != 0; 1977 if (want_reply) { 1978 try conn.writePacket(&.{&[_]u8{SSH_MSG_REQUEST_FAILURE}}); 1979 } 1980 } 1981 1982 /// parse a CHANNEL_OPEN. on a session channel, send CHANNEL_OPEN_CONFIRMATION 1983 /// and return the new Channel. on other types, send CHANNEL_OPEN_FAILURE and 1984 /// return null. 1985 fn handleChannelOpen(conn: *Conn, packet: []const u8, has_channel: bool) !?Channel { 1986 // byte SSH_MSG_CHANNEL_OPEN 1987 // string channel_type 1988 // uint32 sender_channel (peer's id) 1989 // uint32 initial_window 1990 // uint32 max_packet 1991 var r = std.Io.Reader.fixed(packet[1..]); 1992 const ch_type = try takeString(&r, 64); 1993 const remote_id = try r.takeInt(u32, .big); 1994 const initial_window = try r.takeInt(u32, .big); 1995 const max_packet = try r.takeInt(u32, .big); 1996 1997 if (has_channel) { 1998 try sendChannelOpenFailure(conn, remote_id, SSH_OPEN_RESOURCE_SHORTAGE, "only one channel per connection"); 1999 return null; 2000 } 2001 2002 if (!std.mem.eql(u8, ch_type, "session")) { 2003 try sendChannelOpenFailure(conn, remote_id, SSH_OPEN_UNKNOWN_CHANNEL_TYPE, "only session channels are supported"); 2004 return null; 2005 } 2006 2007 // a zero max_packet would leave writeBytes looping without progress 2008 if (max_packet == 0) { 2009 try sendChannelOpenFailure(conn, remote_id, SSH_OPEN_RESOURCE_SHORTAGE, "max packet size must be non-zero"); 2010 return null; 2011 } 2012 2013 const local_id: u32 = 0; // single-channel connection — id is always 0 from our side 2014 var reply: [17]u8 = undefined; 2015 reply[0] = SSH_MSG_CHANNEL_OPEN_CONFIRMATION; 2016 std.mem.writeInt(u32, reply[1..5], remote_id, .big); 2017 std.mem.writeInt(u32, reply[5..9], local_id, .big); 2018 std.mem.writeInt(u32, reply[9..13], initial_recv_window, .big); 2019 std.mem.writeInt(u32, reply[13..17], max_packet_size, .big); 2020 try conn.writePacket(&.{&reply}); 2021 2022 return .{ 2023 .local_id = local_id, 2024 .remote_id = remote_id, 2025 .local_window = initial_recv_window, 2026 .remote_window = initial_window, 2027 .max_packet = max_packet, 2028 }; 2029 } 2030 2031 fn sendChannelOpenFailure(conn: *Conn, remote_id: u32, reason: u32, description: []const u8) !void { 2032 const allocator = conn.allocator; 2033 2034 var reply: std.ArrayList(u8) = .empty; 2035 defer reply.deinit(allocator); 2036 try reply.append(allocator, SSH_MSG_CHANNEL_OPEN_FAILURE); 2037 try writeU32(&reply, allocator, remote_id); 2038 try writeU32(&reply, allocator, reason); 2039 try writeStringField(&reply, allocator, description); 2040 try writeStringField(&reply, allocator, ""); // language tag 2041 try conn.writePacket(&.{reply.items}); 2042 } 2043 2044 /// returns the session request if this one triggered it, else null. an exec 2045 /// command borrows from `packet`. 2046 fn handleChannelRequest(conn: *Conn, ch: *Channel, packet: []const u8) !?Request { 2047 // byte SSH_MSG_CHANNEL_REQUEST 2048 // uint32 recipient_channel (== our local_id) 2049 // string request_type 2050 // boolean want_reply 2051 // …request-specific data 2052 var r = std.Io.Reader.fixed(packet[1..]); 2053 const recipient_channel = try r.takeInt(u32, .big); 2054 if (recipient_channel != ch.local_id) return error.UnknownChannel; 2055 const req_type = try takeString(&r, 64); 2056 const want_reply = (try r.takeByte()) != 0; 2057 2058 if (std.mem.eql(u8, req_type, "pty-req")) { 2059 // string TERM, uint32 width chars, uint32 height rows, uint32 width px, 2060 // uint32 height px, string modes 2061 _ = try takeString(&r, 64); 2062 ch.pty = try takePtySize(&r); 2063 try replyChannelRequest(conn, ch, want_reply, true); 2064 return null; 2065 } 2066 2067 if (std.mem.eql(u8, req_type, "env")) { 2068 // string name, string value. the rest are ignored silently. 2069 const name = try takeString(&r, max_packet_len); 2070 const value = try takeString(&r, max_packet_len); 2071 if (std.mem.eql(u8, name, "GIT_PROTOCOL") and value.len <= ch.git_protocol_buf.len) { 2072 @memcpy(ch.git_protocol_buf[0..value.len], value); 2073 ch.git_protocol_len = value.len; 2074 } 2075 try replyChannelRequest(conn, ch, want_reply, true); 2076 return null; 2077 } 2078 2079 if (std.mem.eql(u8, req_type, "window-change")) { 2080 // uint32 width cells, uint32 height rows, uint32 width px, uint32 height px 2081 const sz = try takePtySize(&r); 2082 if (ch.pty != null) ch.pty = sz; 2083 // spec: window-change MUST NOT request a reply, but accept either 2084 try replyChannelRequest(conn, ch, want_reply, true); 2085 return null; 2086 } 2087 2088 if (std.mem.eql(u8, req_type, "shell")) { 2089 try replyChannelRequest(conn, ch, want_reply, true); 2090 return .{ .shell = ch.pty }; 2091 } 2092 2093 if (std.mem.eql(u8, req_type, "exec")) { 2094 // capture the command string for the handler to inspect 2095 const cmd = try takeString(&r, 4096); 2096 try replyChannelRequest(conn, ch, want_reply, true); 2097 return .{ .exec = .{ 2098 .command = cmd, 2099 .git_protocol = if (ch.git_protocol_len) |len| ch.git_protocol_buf[0..len] else null, 2100 } }; 2101 } 2102 2103 // unknown request kind — fail it 2104 try replyChannelRequest(conn, ch, want_reply, false); 2105 return null; 2106 } 2107 2108 fn replyChannelRequest(conn: *Conn, ch: *Channel, want_reply: bool, success: bool) !void { 2109 if (!want_reply) return; 2110 try sendChannelMessage(conn, ch, if (success) SSH_MSG_CHANNEL_SUCCESS else SSH_MSG_CHANNEL_FAILURE); 2111 } 2112 2113 fn sendChannelMessage(conn: *Conn, ch: *Channel, msg_type: u8) !void { 2114 var packet: [5]u8 = undefined; 2115 packet[0] = msg_type; 2116 std.mem.writeInt(u32, packet[1..5], ch.remote_id, .big); 2117 try conn.writePacket(&.{&packet}); 2118 } 2119 2120 fn handleWindowAdjust(ch: *Channel, packet: []const u8) !void { 2121 // byte SSH_MSG_CHANNEL_WINDOW_ADJUST 2122 // uint32 recipient_channel 2123 // uint32 bytes_to_add 2124 var r = std.Io.Reader.fixed(packet[1..]); 2125 const recipient_channel = try r.takeInt(u32, .big); 2126 if (recipient_channel != ch.local_id) return error.UnknownChannel; 2127 const add = try r.takeInt(u32, .big); 2128 ch.remote_window +|= add; 2129 } 2130 2131 // charge a payload's bytes against the receive window without keeping them. 2132 // the caller credits the window back, choosing the budget that suits it. 2133 fn discardChannelData(ch: *Channel, packet: []const u8, extended: bool) !void { 2134 // byte SSH_MSG_CHANNEL_DATA/EXTENDED_DATA 2135 // uint32 recipient_channel 2136 // [if extended: uint32 type_code] 2137 // string data 2138 const payload = try parseChannelData(packet, extended, ch.local_id); 2139 const data_len: u32 = @intCast(payload.len); 2140 2141 if (data_len > ch.local_window) return error.WindowExceeded; 2142 ch.local_window -= data_len; 2143 } 2144 2145 pub fn parseChannelData(packet: []const u8, extended: bool, expected_channel: u32) ![]const u8 { 2146 if (packet.len < 1) return error.EmptyPacket; 2147 var r = std.Io.Reader.fixed(packet[1..]); 2148 const recipient_channel = try r.takeInt(u32, .big); 2149 if (recipient_channel != expected_channel) return error.UnknownChannel; 2150 if (extended) { 2151 const data_type = try r.takeInt(u32, .big); 2152 if (data_type != SSH_EXTENDED_DATA_STDERR) return error.UnsupportedExtendedData; 2153 } 2154 const data_len = try r.takeInt(u32, .big); 2155 // catches both data_len > remaining (would otherwise be a bounds-check 2156 // panic on the slice) and trailing junk after the declared payload. 2157 if (data_len != r.buffered().len) return error.InvalidChannelData; 2158 return r.buffered(); 2159 } 2160 2161 fn parseChannelId(packet: []const u8, expected_channel: u32) !void { 2162 var r = std.Io.Reader.fixed(packet[1..]); 2163 const recipient_channel = try r.takeInt(u32, .big); 2164 if (recipient_channel != expected_channel) return error.UnknownChannel; 2165 if (r.buffered().len != 0) return error.InvalidChannelMessage; 2166 } 2167 2168 /// send a CHANNEL_WINDOW_ADJUST if our receive window has dipped below half 2169 /// of `budget`, the credit we're willing to have outstanding. used both for 2170 /// the pre-session discard path and by SessionCtx after it consumes a 2171 /// CHANNEL_DATA payload. 2172 fn maybeRefillRecvWindow(conn: *Conn, ch: *Channel, budget: u32) !void { 2173 if (ch.local_window >= budget / 2) return; 2174 const add = budget - ch.local_window; 2175 ch.local_window += add; 2176 var packet: [9]u8 = undefined; 2177 packet[0] = SSH_MSG_CHANNEL_WINDOW_ADJUST; 2178 std.mem.writeInt(u32, packet[1..5], ch.remote_id, .big); 2179 std.mem.writeInt(u32, packet[5..9], add, .big); 2180 try conn.writePacket(&.{&packet}); 2181 } 2182 2183 pub fn writeU32(buf: *std.ArrayList(u8), allocator: std.mem.Allocator, value: u32) !void { 2184 var bytes: [4]u8 = undefined; 2185 std.mem.writeInt(u32, &bytes, value, .big); 2186 try buf.appendSlice(allocator, &bytes); 2187 } 2188 2189 test "pty dimensions have bounded axes, preserving normal and zero sizes" { 2190 for ([_]struct { width: u32, height: u32, expected: PtySize }{ 2191 .{ .width = 80, .height = 24, .expected = .{ .width_cells = 80, .height_cells = 24 } }, 2192 .{ .width = 0, .height = 0, .expected = .{ .width_cells = 0, .height_cells = 0 } }, 2193 .{ .width = 0xffffffff, .height = 0xffffffff, .expected = .{ .width_cells = 512, .height_cells = 128 } }, 2194 }) |case| { 2195 var bytes: [8]u8 = undefined; 2196 std.mem.writeInt(u32, bytes[0..4], case.width, .big); 2197 std.mem.writeInt(u32, bytes[4..8], case.height, .big); 2198 var reader = std.Io.Reader.fixed(&bytes); 2199 try std.testing.expectEqual(case.expected, try takePtySize(&reader)); 2200 } 2201 } 2202 2203 test "channel close before shell or exec is acknowledged" { 2204 const io = std.testing.io; 2205 const allocator = std.testing.allocator; 2206 const key = [_]u8{0x5a} ** 64; 2207 var encoded: [256]u8 = undefined; 2208 var encoded_writer = std.Io.Writer.fixed(&encoded); 2209 var sender = Cipher.init(&key, 0); 2210 var open: std.ArrayList(u8) = .empty; 2211 defer open.deinit(allocator); 2212 try open.append(allocator, SSH_MSG_CHANNEL_OPEN); 2213 try writeStringField(&open, allocator, "session"); 2214 try writeU32(&open, allocator, 7); 2215 try writeU32(&open, allocator, 32768); 2216 try writeU32(&open, allocator, 32768); 2217 try sender.writePacket(io, &encoded_writer, &.{open.items}); 2218 try sender.writePacket(io, &encoded_writer, &.{&.{ SSH_MSG_CHANNEL_CLOSE, 0, 0, 0, 0 }}); 2219 var reader = std.Io.Reader.fixed(encoded_writer.buffered()); 2220 var output: [256]u8 = undefined; 2221 var writer = std.Io.Writer.fixed(&output); 2222 var idle = IdleState{}; 2223 var conn = Conn{ 2224 .io = io, 2225 .allocator = allocator, 2226 .reader = &reader, 2227 .writer = &writer, 2228 .cs_cipher = Cipher.init(&key, 0), 2229 .sc_cipher = Cipher.init(&key, 0), 2230 .rekey = undefined, 2231 .idle = &idle, 2232 }; 2233 const Handler = struct { 2234 pub fn handleSession(_: *@This(), _: *SessionCtx, _: Request) !void { 2235 return error.UnexpectedSession; 2236 } 2237 }; 2238 var handler = Handler{}; 2239 try runChannelLayer(&conn, &([_]u8{0} ** fingerprint_len), &handler); 2240 var output_reader = std.Io.Reader.fixed(writer.buffered()); 2241 var receiver = Cipher.init(&key, 0); 2242 const confirmation = try receiver.readPacket(allocator, &output_reader); 2243 defer allocator.free(confirmation); 2244 try std.testing.expectEqual(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, confirmation[0]); 2245 const close = try receiver.readPacket(allocator, &output_reader); 2246 defer allocator.free(close); 2247 try std.testing.expectEqualSlices(u8, &.{ SSH_MSG_CHANNEL_CLOSE, 0, 0, 0, 7 }, close); 2248 try std.testing.expectEqual(0, output_reader.buffered().len); 2249 } 2250