radicle-ssh = { version = "0.10", path = "crates/radicle-ssh", default-features = false }

* `radicle-ssh`: OpenSSH functionality, including a library used to interface with `ssh-agent`.

[package]

name = "radicle-ssh"

description = "Radicle SSH library"

homepage.workspace = true

repository.workspace = true

license = "Apache-2.0"

version = "0.10.0"

authors = [

  "Fintan Halpenny <fintan.halpenny@gmail.com>",

  "Pierre-Étienne Meunier <pe@pijul.org>",

  "cloudhead <cloudhead@radicle.xyz>"

]

edition.workspace = true

rust-version.workspace = true

[dependencies]

thiserror = { workspace = true, default-features = true }

zeroize = { workspace = true }

[target.'cfg(windows)'.dependencies]

winpipe = { workspace = true }

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/// Write clients for SSH agents.

pub mod client;

mod msg;

/// Constraints on how keys can be used.

#[derive(Debug, PartialEq, Eq)]

pub enum Constraint {

    /// The key shall disappear from the agent's memory after that many seconds.

    KeyLifetime { seconds: u32 },

    /// Signatures need to be confirmed by the agent (for instance using a dialog).

    Confirm,

    /// Custom constraints

    Extensions { name: Vec<u8>, details: Vec<u8> },

}

use std::fmt;

use std::io::{Read, Write};

use std::path::{Path, PathBuf};

#[cfg(unix)]

pub use std::os::unix::net::UnixStream as Stream;

#[cfg(windows)]

pub use winpipe::WinStream as Stream;

use thiserror::Error;

use zeroize::Zeroize as _;

use crate::agent::msg;

use crate::agent::Constraint;

use crate::encoding::{self, Encodable};

use crate::encoding::{Buffer, Encoding, Reader};

/// An ed25519 Signature.

pub type Signature = [u8; 64];

#[derive(Debug, Error)]

pub enum Error {

    /// Agent protocol error.

    #[error("SSH agent replied with unexpected data, violating the SSH agent protocol.")]

    AgentProtocolError,

    #[error(

        "SSH agent replied with failure (protocol message number 5), which could not be handled."

    )]

    AgentFailure,

    #[error("Unable to connect to SSH agent because '{path}' was not found: {source}")]

    BadAuthSock {

        path: String,

        source: std::io::Error,

    },

    #[error("Encoding error while communicating with SSH agent: {0}")]

    Encoding(#[from] encoding::Error),

    #[error("Unable to read environment variable '{var}': {source}")]

    EnvVar {

        var: String,

        source: std::env::VarError,

    },

    #[error("Unable to connect SSH agent using the path '{path}': {source}")]

    Connect {

        path: String,

        #[source]

        source: std::io::Error,

    },

    #[error("I/O error while communicating with SSH agent: {0}")]

    Io(#[from] std::io::Error),

}

impl Error {

    pub fn is_not_running(&self) -> bool {

        match self {

            Self::EnvVar { .. } | Self::BadAuthSock { .. } => true,

            #[cfg(windows)]

            Self::Connect { source, .. }

                if source.kind() == std::io::ErrorKind::ConnectionRefused =>

            {

                // On Windows, a named pipe might be used, and if no

                // agent is running, we might get a "connection refused"

                // error, even though the `SSH_AUTH_SOCK` environment

                // variable is set and the named pipe exists.

                true

            }

            _ => false,

        }

    }

}

/// SSH agent client.

pub struct AgentClient<S = Stream> {

    /// The path that was originally used to connect to the agent.

    path: Option<PathBuf>,

    /// The underlying stream to the SSH agent.

    stream: S,

}

impl<S> AgentClient<S> {

    pub fn path(&self) -> Option<&Path> {

        self.path.as_deref()

    }

}

impl AgentClient<Stream> {

    /// Connect to an SSH agent at the provided path.

    pub fn connect<P>(path: P) -> Result<Self, Error>

    where

        P: AsRef<Path>,

    {

        let path = path.as_ref().to_owned();

        let stream = match Stream::connect(&path) {

            Err(err) if err.kind() == std::io::ErrorKind::NotFound => {

                return Err(Error::BadAuthSock {

                    path: path.display().to_string(),

                    source: err,

                })

            }

            Err(err) => {

                return Err(Error::Connect {

                    path: path.display().to_string(),

                    source: err,

                })

            }

            Ok(stream) => stream,

        };

        Ok(Self {

            path: Some(path),

            stream,

        })

    }

    pub fn connect_env() -> Result<Self, Error> {

        const SSH_AUTH_SOCK: &str = "SSH_AUTH_SOCK";

        let var = std::env::var(SSH_AUTH_SOCK);

        #[cfg(windows)]

        let var = var.or({

            // Windows uses a named pipe for the SSH agent, which

            // we fall back to in case reading the environment

            // variable fails.

            Ok(r"\\.\pipe\openssh-ssh-agent".to_string())

        });

        Self::connect(var.map_err(|err| Error::EnvVar {

            var: SSH_AUTH_SOCK.to_string(),

            source: err,

        })?)

    }

}

impl<Stream: ClientStream> AgentClient<Stream> {

    pub fn new(path: Option<PathBuf>, stream: Stream) -> Self {

        Self { path, stream }

    }

    /// Send a key to the agent, with a (possibly empty) slice of constraints

    /// to apply when using the key to sign.

    pub fn add_identity<K>(&mut self, key: &K, constraints: &[Constraint]) -> Result<(), Error>

    where

        K: Encodable,

        K::Error: std::error::Error + Send + Sync + 'static,

    {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        if constraints.is_empty() {

            buf.push(msg::ADD_IDENTITY)

        } else {

            buf.push(msg::ADD_ID_CONSTRAINED)

        }

        key.write(&mut buf);

        if !constraints.is_empty() {

            for cons in constraints {

                match *cons {

                    Constraint::KeyLifetime { seconds } => {

                        buf.push(msg::CONSTRAIN_LIFETIME);

                        buf.extend_u32(seconds);

                    }

                    Constraint::Confirm => buf.push(msg::CONSTRAIN_CONFIRM),

                    Constraint::Extensions {

                        ref name,

                        ref details,

                    } => {

                        buf.push(msg::CONSTRAIN_EXTENSION);

                        buf.extend_ssh_string(name);

                        buf.extend_ssh_string(details);

                    }

                }

            }

        }

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Add a smart card to the agent, with a (possibly empty) set of

    /// constraints to apply when signing.

    pub fn add_smartcard_key(

        &mut self,

        id: &str,

        pin: &[u8],

        constraints: &[Constraint],

    ) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        if constraints.is_empty() {

            buf.push(msg::ADD_SMARTCARD_KEY)

        } else {

            buf.push(msg::ADD_SMARTCARD_KEY_CONSTRAINED)

        }

        buf.extend_ssh_string(id.as_bytes());

        buf.extend_ssh_string(pin);

        if !constraints.is_empty() {

            buf.extend_usize(constraints.len());

            for cons in constraints {

                match *cons {

                    Constraint::KeyLifetime { seconds } => {

                        buf.push(msg::CONSTRAIN_LIFETIME);

                        buf.extend_u32(seconds);

                    }

                    Constraint::Confirm => buf.push(msg::CONSTRAIN_CONFIRM),

                    Constraint::Extensions {

                        ref name,

                        ref details,

                    } => {

                        buf.push(msg::CONSTRAIN_EXTENSION);

                        buf.extend_ssh_string(name);

                        buf.extend_ssh_string(details);

                    }

                }

            }

        }

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Lock the agent, making it refuse to sign until unlocked.

    pub fn lock(&mut self, passphrase: &[u8]) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::LOCK);

        buf.extend_ssh_string(passphrase);

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Unlock the agent, allowing it to sign again.

    pub fn unlock(&mut self, passphrase: &[u8]) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::UNLOCK);

        buf.extend_ssh_string(passphrase);

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Ask the agent for a list of the currently registered secret

    /// keys.

    pub fn request_identities<K>(&mut self) -> Result<Vec<K>, Error>

    where

        K: Encodable,

        K::Error: std::error::Error + Send + Sync + 'static,

    {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::REQUEST_IDENTITIES);

        buf.write_len();

        let mut keys = Vec::new();

        let resp = self.stream.request(&buf)?;

        if resp[0] == msg::IDENTITIES_ANSWER {

            let mut r = resp.reader(1);

            let n = r.read_u32()?;

            for _ in 0..n {

                let key = r.read_string()?;

                let _ = r.read_string()?;

                let mut r = key.reader(0);

                if let Ok(pk) = K::read(&mut r) {

                    keys.push(pk);

                }

            }

        }

        Ok(keys)

    }

    /// Ask the agent to sign the supplied piece of data.

    pub fn sign<K>(&mut self, public: &K, data: &[u8]) -> Result<Signature, Error>

    where

        K: Encodable + fmt::Debug,

    {

        let req = self.prepare_sign_request(public, data);

        let resp = self.stream.request(&req)?;

        if !resp.is_empty() && resp[0] == msg::SIGN_RESPONSE {

            self.read_signature(&resp)

        } else if !resp.is_empty() && resp[0] == msg::FAILURE {

            Err(Error::AgentFailure)

        } else {

            Err(Error::AgentProtocolError)

        }

    }

    fn prepare_sign_request<K>(&self, public: &K, data: &[u8]) -> Buffer

    where

        K: Encodable + fmt::Debug,

    {

        // byte                    SSH_AGENTC_SIGN_REQUEST

        // string                  key blob

        // string                  data

        // uint32                  flags

        let mut pk = Buffer::default();

        public.write(&mut pk);

        let total = 1 + pk.len() + 4 + data.len() + 4;

        let mut buf = Buffer::default();

        buf.extend_usize(total);

        buf.push(msg::SIGN_REQUEST);

        buf.extend_from_slice(&pk);

        buf.extend_ssh_string(data);

        // Signature flags should be zero for ed25519.

        buf.extend_u32(0);

        buf

    }

    fn read_signature(&self, sig: &[u8]) -> Result<Signature, Error> {

        let mut r = sig.reader(1);

        let mut resp = r.read_string()?.reader(0);

        let _t = resp.read_string()?;

        let sig = resp.read_string()?;

        let mut out = [0; 64];

        out.copy_from_slice(sig);

        Ok(out)

    }

    /// Ask the agent to remove a key from its memory.

    pub fn remove_identity<K>(&mut self, public: &K) -> Result<(), Error>

    where

        K: Encodable,

    {

        let mut pk: Buffer = Vec::new().into();

        public.write(&mut pk);

        let total = 1 + pk.len();

        let mut buf = Buffer::default();

        buf.extend_usize(total);

        buf.push(msg::REMOVE_IDENTITY);

        buf.extend_from_slice(&pk);

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Ask the agent to remove a smartcard from its memory.

    pub fn remove_smartcard_key(&mut self, id: &str, pin: &[u8]) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::REMOVE_SMARTCARD_KEY);

        buf.extend_ssh_string(id.as_bytes());

        buf.extend_ssh_string(pin);

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Ask the agent to forget all known keys.

    pub fn remove_all_identities(&mut self) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::REMOVE_ALL_IDENTITIES);

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Send a custom message to the agent.

    pub fn extension(&mut self, typ: &[u8], ext: &[u8]) -> Result<(), Error> {

        let mut buf = Buffer::default();

        buf.resize(4, 0);

        buf.push(msg::EXTENSION);

        buf.extend_ssh_string(typ);

        buf.extend_ssh_string(ext);

        buf.write_len();

        self.stream.request(&buf)?;

        Ok(())

    }

    /// Ask the agent about supported extensions.

    pub fn query_extension(&mut self, typ: &[u8], mut ext: Buffer) -> Result<bool, Error> {

        let mut req = Buffer::default();

        req.resize(4, 0);

        req.push(msg::EXTENSION);

        req.extend_ssh_string(typ);

        req.write_len();

        let resp = self.stream.request(&req)?;

        let mut r = resp.reader(1);

        ext.extend(r.read_string()?);

        Ok(!resp.is_empty() && resp[0] == msg::SUCCESS)

    }

}

pub trait ClientStream: Sized + Send + Sync {

    fn request(&mut self, msg: &[u8]) -> Result<Buffer, Error>;

}

impl<S: Read + Write + Sized + Send + Sync> ClientStream for S {

    fn request(&mut self, msg: &[u8]) -> Result<Buffer, Error> {

        let mut resp = Buffer::default();

        // Write the message

        self.write_all(msg)?;

        self.flush()?;

        // Read the length

        resp.resize(4, 0);

        self.read_exact(&mut resp)?;

        // Read the rest of the buffer

        let len = u32::from_be_bytes(resp.as_slice().try_into().unwrap()) as usize;

        resp.zeroize();

        resp.resize(len, 0);

        self.read_exact(&mut resp)?;

        Ok(resp)

    }

}

pub const FAILURE: u8 = 5;

pub const SUCCESS: u8 = 6;

pub const IDENTITIES_ANSWER: u8 = 12;

pub const SIGN_RESPONSE: u8 = 14;

#[allow(dead_code)]

pub const EXTENSION_FAILURE: u8 = 28;

pub const REQUEST_IDENTITIES: u8 = 11;

pub const SIGN_REQUEST: u8 = 13;

pub const ADD_IDENTITY: u8 = 17;

pub const REMOVE_IDENTITY: u8 = 18;

pub const REMOVE_ALL_IDENTITIES: u8 = 19;

pub const ADD_ID_CONSTRAINED: u8 = 25;

pub const ADD_SMARTCARD_KEY: u8 = 20;

pub const REMOVE_SMARTCARD_KEY: u8 = 21;

pub const LOCK: u8 = 22;

pub const UNLOCK: u8 = 23;

pub const ADD_SMARTCARD_KEY_CONSTRAINED: u8 = 26;

pub const EXTENSION: u8 = 27;

pub const CONSTRAIN_LIFETIME: u8 = 1;

pub const CONSTRAIN_CONFIRM: u8 = 2;

pub const CONSTRAIN_EXTENSION: u8 = 3;

// Copyright 2016 Pierre-Étienne Meunier

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

//

use std::ops::DerefMut as _;

use thiserror::Error;

use zeroize::Zeroizing;

/// General purpose writable byte buffer we use everywhere.

pub type Buffer = Zeroizing<Vec<u8>>;

#[derive(Debug, Error)]

pub enum Error {

    /// Index out of bounds

    #[error("Index out of bounds")]

    IndexOutOfBounds,

}

pub trait Encodable: Sized {

    type Error: std::error::Error + Send + Sync + 'static;

    /// Read from the SSH format.

    fn read(reader: &mut Cursor) -> Result<Self, Self::Error>;

    /// Write to the SSH format.

    fn write<E: Encoding>(&self, buf: &mut E);

}

/// Encode in the SSH format.

pub trait Encoding {

    /// Push an SSH-encoded string to `self`.

    fn extend_ssh_string(&mut self, s: &[u8]);

    /// Push an SSH-encoded blank string of length `s` to `self`.

    fn extend_ssh_string_blank(&mut self, s: usize) -> &mut [u8];

    /// Push an SSH-encoded multiple-precision integer.

    fn extend_ssh_mpint(&mut self, s: &[u8]);

    /// Push an SSH-encoded list.

    fn extend_list<'a, I: Iterator<Item = &'a [u8]>>(&mut self, list: I);

    /// Push an SSH-encoded unsigned 32-bit integer.

    fn extend_u32(&mut self, u: u32);

    /// Push an SSH-encoded empty list.

    fn write_empty_list(&mut self);

    /// Write the buffer length at the beginning of the buffer.

    fn write_len(&mut self);

    /// Push a [`usize`] as an SSH-encoded unsigned 32-bit integer.

    /// May panic if the argument is greater than [`u32::MAX`].

    /// This is a convenience method, to spare callers casting or converting

    /// [`usize`] to [`u32`]. If callers end up in a situation where they

    /// need to push a 32-bit unsigned integer, but the value they would

    /// like to push does not fit 32 bits, then the implementation will not

    /// comply with the SSH format anyway.

    fn extend_usize(&mut self, u: usize) {

        self.extend_u32(u.try_into().unwrap())

    }

}

/// Encoding length of the given mpint.

pub fn mpint_len(s: &[u8]) -> usize {

    let mut i = 0;

    while i < s.len() && s[i] == 0 {

        i += 1

    }

    (if s[i] & 0x80 != 0 { 5 } else { 4 }) + s.len() - i

}

impl Encoding for Vec<u8> {

    fn extend_ssh_string(&mut self, s: &[u8]) {

        self.extend_usize(s.len());

        self.extend(s);

    }

    fn extend_ssh_string_blank(&mut self, len: usize) -> &mut [u8] {

        self.extend_usize(len);

        let current = self.len();

        self.resize(current + len, 0u8);

        &mut self[current..]

    }

    fn extend_ssh_mpint(&mut self, s: &[u8]) {

        // Skip initial 0s.

        let mut i = 0;

        while i < s.len() && s[i] == 0 {

            i += 1

        }

        // If the first non-zero is >= 128, write its length (u32, BE), followed by 0.

        if s[i] & 0x80 != 0 {

            self.extend_usize(s.len() - i + 1);

            self.push(0)

        } else {

            self.extend_usize(s.len() - i);

        }

        self.extend(&s[i..]);

    }

    fn extend_u32(&mut self, s: u32) {

        self.extend(s.to_be_bytes());

    }

    fn extend_list<'a, I: Iterator<Item = &'a [u8]>>(&mut self, list: I) {

        let len0 = self.len();

        let mut first = true;

        for i in list {

            if !first {

                self.push(b',')

            } else {

                first = false;

            }

            self.extend(i)

        }

        let len = (self.len() - len0 - 4) as u32;

        self.splice(len0..len0, len.to_be_bytes());

    }

    fn write_empty_list(&mut self) {

        self.extend([0, 0, 0, 0]);

    }

    fn write_len(&mut self) {

        let len = self.len() - 4;

        self[..4].copy_from_slice((len as u32).to_be_bytes().as_slice());

    }

}

impl Encoding for Buffer {

    fn extend_ssh_string(&mut self, s: &[u8]) {

        self.deref_mut().extend_ssh_string(s)

    }

    fn extend_ssh_string_blank(&mut self, len: usize) -> &mut [u8] {

        self.deref_mut().extend_ssh_string_blank(len)

    }

    fn extend_ssh_mpint(&mut self, s: &[u8]) {

        self.deref_mut().extend_ssh_mpint(s)

    }

    fn extend_list<'a, I: Iterator<Item = &'a [u8]>>(&mut self, list: I) {

        self.deref_mut().extend_list(list)

    }

    fn write_empty_list(&mut self) {

        self.deref_mut().write_empty_list()

    }

    fn extend_u32(&mut self, s: u32) {

        self.deref_mut().extend_u32(s);

    }

    fn write_len(&mut self) {

        self.deref_mut().write_len()

    }

}

/// A cursor-like trait to read SSH-encoded things.

pub trait Reader {

    /// Create an SSH reader for `self`.

    fn reader(&self, starting_at: usize) -> Cursor<'_>;

}

impl Reader for Buffer {

    fn reader(&self, starting_at: usize) -> Cursor<'_> {

        Cursor {

            s: self,

            position: starting_at,

        }

    }

}

impl Reader for [u8] {

    fn reader(&self, starting_at: usize) -> Cursor<'_> {

        Cursor {

            s: self,

            position: starting_at,

        }

    }

}

/// A cursor-like type to read SSH-encoded values.

#[derive(Debug)]

pub struct Cursor<'a> {

    s: &'a [u8],

    #[doc(hidden)]

    pub position: usize,

}

impl<'a> Cursor<'a> {

    /// Read one string from this reader.

    pub fn read_string(&mut self) -> Result<&'a [u8], Error> {

        let len = self.read_u32()? as usize;

        if self.position + len <= self.s.len() {

            let result = &self.s[self.position..(self.position + len)];

            self.position += len;

            Ok(result)

        } else {

            Err(Error::IndexOutOfBounds)

        }

    }

    /// Read a `u32` from this reader.

    pub fn read_u32(&mut self) -> Result<u32, Error> {

        if self.position + 4 <= self.s.len() {

            let u =

                u32::from_be_bytes(self.s[self.position..self.position + 4].try_into().unwrap());

            self.position += 4;

            Ok(u)

        } else {

            Err(Error::IndexOutOfBounds)

        }

    }

    /// Read one byte from this reader.

    pub fn read_byte(&mut self) -> Result<u8, Error> {

        if self.position < self.s.len() {

            let u = self.s[self.position];

            self.position += 1;

            Ok(u)

        } else {

            Err(Error::IndexOutOfBounds)

        }

    }

    pub fn read_bytes<const S: usize>(&mut self) -> Result<[u8; S], Error> {

        let mut buf = [0; S];

        for b in buf.iter_mut() {

            *b = self.read_byte()?;

        }

        Ok(buf)

    }

    /// Read one byte from this reader.

    pub fn read_mpint(&mut self) -> Result<&'a [u8], Error> {

        let len = self.read_u32()? as usize;

        if self.position + len <= self.s.len() {

            let result = &self.s[self.position..(self.position + len)];

            self.position += len;

            Ok(result)

        } else {

            Err(Error::IndexOutOfBounds)

        }

    }

}

pub mod agent;

pub mod encoding;

pub use agent::client::Error;

radicle-ssh = { workspace = true }