From d2f423521ec76406944ad83098ec33afe20c692b Mon Sep 17 00:00:00 2001 From: Kim Altintop Date: Mon, 9 Jan 2023 13:18:33 +0100 Subject: This is it Squashed commit of all the exploration history. Development starts here. Signed-off-by: Kim Altintop --- src/ssh/agent.rs | 279 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 279 insertions(+) create mode 100644 src/ssh/agent.rs (limited to 'src/ssh/agent.rs') diff --git a/src/ssh/agent.rs b/src/ssh/agent.rs new file mode 100644 index 0000000..c29ad62 --- /dev/null +++ b/src/ssh/agent.rs @@ -0,0 +1,279 @@ +// Copyright © 2022 Kim Altintop +// SPDX-License-Identifier: GPL-2.0-only WITH openvpn-openssl-exception + +use std::{ + env, + io::{ + self, + ErrorKind::*, + }, +}; + +use anyhow::Context; +use ssh_encoding::{ + CheckedSum, + Decode, + Encode, + Reader, + Writer, +}; +use ssh_key::{ + public::KeyData, + Algorithm, + HashAlg, + PublicKey, + Signature, +}; + +#[cfg(unix)] +pub use std::os::unix::net::UnixStream; +#[cfg(windows)] +pub use uds_windows::UnixStram; + +const SSH_AUTH_SOCK: &str = "SSH_AUTH_SOCK"; + +const MAX_AGENT_REPLY_LEN: usize = 256 * 1024; + +const SSH_AGENTC_REQUEST_IDENTITIES: u8 = 11; +const SSH_AGENTC_SIGN_REQUEST: u8 = 13; +const SSH_AGENT_FAILURE: u8 = 5; +const SSH_AGENT_IDENTITIES_ANSWER: u8 = 12; +const SSH_AGENT_RSA_SHA2_256: u32 = 2; +const SSH_AGENT_RSA_SHA2_512: u32 = 4; +const SSH_AGENT_SIGN_RESPONSE: u8 = 14; + +pub struct Client { + conn: T, +} + +impl Client { + pub fn from_env() -> io::Result { + let path = env::var_os(SSH_AUTH_SOCK).ok_or_else(|| { + io::Error::new( + io::ErrorKind::AddrNotAvailable, + "SSH_AUTH_SOCK environment variable not set", + ) + })?; + UnixStream::connect(path).map(Self::from) + } +} + +impl From for Client { + fn from(conn: UnixStream) -> Self { + Self { conn } + } +} + +impl<'a> From<&'a UnixStream> for Client<&'a UnixStream> { + fn from(conn: &'a UnixStream) -> Self { + Self { conn } + } +} + +impl Client +where + T: io::Read + io::Write, +{ + pub fn sign(&mut self, key: &PublicKey, msg: impl AsRef<[u8]>) -> io::Result { + request( + &mut self.conn, + SignRequest { + key, + msg: msg.as_ref(), + }, + ) + .map(|SignResponse { sig }| sig) + } + + pub fn list_keys(&mut self) -> io::Result> { + request(&mut self.conn, RequestIdentities).map(|IdentitiesAnswer { keys }| keys) + } +} + +trait Request: Encode { + type Response: Response; +} + +trait Response: Decode { + const SUCCESS: u8; +} + +fn request(mut io: I, req: T) -> io::Result +where + I: io::Read + io::Write, + T: Request, +{ + send(&mut io, req)?; + let resp = recv(&mut io)?; + let mut reader = resp.as_slice(); + match u8::decode(&mut reader).map_err(|_| unknown_response())? { + x if x == T::Response::SUCCESS => T::Response::decode(&mut reader).map_err(decode), + SSH_AGENT_FAILURE => Err(agent_error()), + _ => Err(unknown_response()), + } +} + +fn send(mut io: W, req: T) -> io::Result<()> +where + W: io::Write, + T: Encode, +{ + let len = req.encoded_len_prefixed().map_err(encode)?; + let mut buf = Vec::with_capacity(len); + req.encode_prefixed(&mut buf).map_err(encode)?; + + io.write_all(&buf)?; + io.flush()?; + + Ok(()) +} + +fn recv(mut io: R) -> io::Result> { + let want = { + let mut buf = [0; 4]; + io.read_exact(&mut buf)?; + u32::from_be_bytes(buf) as usize + }; + + if want < 1 { + return Err(incomplete_response()); + } + if want > MAX_AGENT_REPLY_LEN { + return Err(reponse_too_large()); + } + + let mut buf = vec![0; want]; + io.read_exact(&mut buf)?; + + Ok(buf) +} + +struct SignRequest<'a> { + key: &'a PublicKey, + msg: &'a [u8], +} + +impl Request for SignRequest<'_> { + type Response = SignResponse; +} + +impl Encode for SignRequest<'_> { + type Error = crate::Error; + + fn encoded_len(&self) -> Result { + Ok([ + self.key.key_data().encoded_len_prefixed()?, + self.msg.encoded_len()?, + SSH_AGENTC_SIGN_REQUEST.encoded_len()?, + 4, // flags + ] + .checked_sum()?) + } + + fn encode(&self, writer: &mut impl Writer) -> Result<(), Self::Error> { + SSH_AGENTC_SIGN_REQUEST.encode(writer)?; + self.key.key_data().encode_prefixed(writer)?; + self.msg.encode(writer)?; + let flags = match self.key.algorithm() { + Algorithm::Rsa { hash } => match hash { + Some(HashAlg::Sha256) => SSH_AGENT_RSA_SHA2_256, + _ => SSH_AGENT_RSA_SHA2_512, // sane default + }, + _ => 0, + }; + flags.encode(writer)?; + Ok(()) + } +} + +struct SignResponse { + sig: Signature, +} + +impl Response for SignResponse { + const SUCCESS: u8 = SSH_AGENT_SIGN_RESPONSE; +} + +impl Decode for SignResponse { + type Error = crate::Error; + + fn decode(reader: &mut impl Reader) -> Result { + let sig = reader.read_prefixed(Signature::decode)?; + Ok(Self { sig }) + } +} + +struct RequestIdentities; + +impl Request for RequestIdentities { + type Response = IdentitiesAnswer; +} + +impl Encode for RequestIdentities { + type Error = crate::Error; + + fn encoded_len(&self) -> Result { + Ok(SSH_AGENTC_REQUEST_IDENTITIES.encoded_len()?) + } + + fn encode(&self, writer: &mut impl Writer) -> Result<(), Self::Error> { + Ok(SSH_AGENTC_REQUEST_IDENTITIES.encode(writer)?) + } +} + +struct IdentitiesAnswer { + keys: Vec, +} + +impl Response for IdentitiesAnswer { + const SUCCESS: u8 = SSH_AGENT_IDENTITIES_ANSWER; +} + +impl Decode for IdentitiesAnswer { + type Error = crate::Error; + + fn decode(reader: &mut impl Reader) -> Result { + let nkeys = usize::decode(reader).context("nkeys")?; + let mut keys = Vec::with_capacity(nkeys); + + for _ in 0..nkeys { + let key_data = reader.read_prefixed(KeyData::decode).context("key data")?; + let comment = String::decode(reader).context("comment")?; + keys.push(PublicKey::new(key_data, comment)); + } + + Ok(Self { keys }) + } +} + +fn e(kind: io::ErrorKind, msg: &str) -> io::Error { + io::Error::new(kind, msg) +} + +fn ee(kind: io::ErrorKind, e: crate::Error) -> io::Error { + io::Error::new(kind, e) +} + +fn incomplete_response() -> io::Error { + e(UnexpectedEof, "incomplete response") +} + +fn reponse_too_large() -> io::Error { + e(Unsupported, "response payload too large") +} + +fn encode(e: crate::Error) -> io::Error { + ee(InvalidData, e.context("failed to encode request")) +} + +fn decode(e: crate::Error) -> io::Error { + ee(InvalidData, e.context("failed to decode response")) +} + +fn agent_error() -> io::Error { + e(Other, "error response from agent") +} + +fn unknown_response() -> io::Error { + e(Unsupported, "unknown response") +} -- cgit v1.2.3