"ed25519",

 "radicle-ssh",

 "radicle-ssh",

name = "radicle-ssh"

version = "0.10.0"

dependencies = [

 "thiserror 2.0.18",

 "winpipe",

 "zeroize",

]

[[package]]

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`.

        Ok(c) => term::format::positive(format!(

            "running ({})",

            c.path()

                .map(|p| p.display().to_string())

                .unwrap_or(String::from("?"))

        )),

ssh = ["radicle-ssh", "ssh-key"]

radicle-ssh = { workspace = true, optional = true }

use std::io;

use radicle_ssh::encoding;

use radicle_ssh::encoding::Encodable;

use radicle_ssh::encoding::Encoding;

use radicle_ssh::encoding::Reader;

use crate::PublicKey;

#[derive(Debug, Error)]

#[non_exhaustive]

pub enum SignatureError {

    #[error(transparent)]

    Invalid(#[from] crypto::Error),

    #[error(transparent)]

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

    #[error("unknown algorithm '{0}'")]

    UnknownAlgorithm(String),

}

impl Encodable for crypto::Signature {

    type Error = SignatureError;

    fn read(r: &mut encoding::Cursor) -> Result<Self, Self::Error> {

        let buf = r.read_string()?;

        let mut inner_strs = buf.reader(0);

        let sig_type = inner_strs.read_string()?;

        if sig_type != b"ssh-ed25519" {

            return Err(SignatureError::UnknownAlgorithm(

                String::from_utf8_lossy(sig_type).to_string(),

            ));

        }

        let sig = crypto::Signature::try_from(inner_strs.read_string()?)?;

        Ok(sig)

    }

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

        let mut inner_strs = Vec::new();

        inner_strs.extend_ssh_string(b"ssh-ed25519");

        inner_strs.extend_ssh_string(self.as_ref());

        buf.extend_ssh_string(&inner_strs);

    }

}

#[derive(Debug, Error)]

#[non_exhaustive]

pub enum PublicKeyError {

    #[error(transparent)]

    Invalid(#[from] crypto::Error),

    #[error(transparent)]

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

    #[error("unknown algorithm '{0}'")]

    UnknownAlgorithm(String),

}

impl Encodable for PublicKey {

    type Error = PublicKeyError;

    fn read(r: &mut encoding::Cursor) -> Result<Self, Self::Error> {

        match r.read_string()? {

            b"ssh-ed25519" => {

                let s = r.read_string()?;

                let p = PublicKey::try_from(s)?;

                Ok(p)

            }

            v => Err(PublicKeyError::UnknownAlgorithm(

                String::from_utf8_lossy(v).to_string(),

            )),

        }

    }

    fn write<E: Encoding>(&self, w: &mut E) {

        let mut str_w: Vec<u8> = Vec::<u8>::new();

        str_w.extend_ssh_string(b"ssh-ed25519");

        str_w.extend_ssh_string(&self[..]);

        w.extend_ssh_string(&str_w)

    }

}

#[derive(Debug, Error)]

#[non_exhaustive]

pub enum SecretKeyError {

    #[error(transparent)]

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

    #[error(transparent)]

    Crypto(#[from] crypto::Error),

    #[error(transparent)]

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

    #[error("unknown algorithm '{0}'")]

    UnknownAlgorithm(String),

    #[error("public key does not match secret key")]

    Mismatch,

}

impl Encodable for crypto::SecretKey {

    type Error = SecretKeyError;

    fn read(r: &mut encoding::Cursor) -> Result<Self, Self::Error> {

        match r.read_string()? {

            b"ssh-ed25519" => {

                let public = r.read_string()?;

                let pair = r.read_string()?;

                let _comment = r.read_string()?;

                let key = crypto::SecretKey::try_from(pair)?;

                if public != key.public_key().as_ref() {

                    return Err(SecretKeyError::Mismatch);

                }

                Ok(key)

            }

            s => Err(SecretKeyError::UnknownAlgorithm(

                String::from_utf8_lossy(s).to_string(),

            )),

        }

    }

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

        let public = self.0.public_key();

        buf.extend_ssh_string(b"ssh-ed25519");

        buf.extend_ssh_string(public.as_ref());

        buf.extend_ssh_string(self.0.as_ref());

        buf.extend_ssh_string(b"radicle");

    }

}

#[cfg(test)]

mod test {

    use std::sync::{Arc, Mutex};

    use qcheck_macros::quickcheck;

    use crate as crypto;

    use crate::{PublicKey, SecretKey};

    use radicle_ssh::agent::client::{AgentClient, ClientStream, Error};

    use radicle_ssh::encoding::*;

    #[derive(Clone, Default)]

    struct DummyStream {

        incoming: Arc<Mutex<Vec<u8>>>,

    }

    impl ClientStream for DummyStream {

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

            *self.incoming.lock().unwrap() = buf.to_vec();

            Ok(Buffer::default())

        }

    }

    #[quickcheck]

    fn prop_encode_decode_sk(input: [u8; 64]) {

        let mut buf = Buffer::default();

        let sk = crypto::SecretKey::from(input);

        sk.write(&mut buf);

        let mut cursor = buf.reader(0);

        let output = SecretKey::read(&mut cursor).unwrap();

        assert_eq!(sk, output);

    }

    #[test]

    fn test_agent_encoding_remove() {

        use std::str::FromStr;

        let pk = PublicKey::from_str("z6MktWkM9vcfysWFq1c2aaLjJ6j4PYYg93TLPswR4qtuoAeT").unwrap();

        let expected = [

            0, 0, 0, 56, // Message length

            18, // Message type (remove identity)

            0, 0, 0, 51, // Key blob length

            0, 0, 0, 11, // Key type length

            115, 115, 104, 45, 101, 100, 50, 53, 53, 49, 57, // Key type

            0, 0, 0, 32, // Key length

            208, 232, 92, 138, 225, 114, 116, 99, 156, 177, 148, 93, 65, 93, 198, 25, 46, 203, 79,

            37, 145, 51, 176, 174, 61, 136, 160, 107, 4, 95, 175, 144, // Key

        ];

        let stream = DummyStream::default();

        let mut agent = AgentClient::new(None, stream.clone());

        agent.remove_identity(&pk).unwrap();

        assert_eq!(

            stream.incoming.lock().unwrap().as_slice(),

            expected.as_slice()

        );

    }

    #[test]

    fn test_agent_encoding_sign() {

        use std::str::FromStr;

        let pk = PublicKey::from_str("z6MktWkM9vcfysWFq1c2aaLjJ6j4PYYg93TLPswR4qtuoAeT").unwrap();

        let expected = [

            0, 0, 0, 73, // Message length

            13, // Message type (sign request)

            0, 0, 0, 51, // Key blob length

            0, 0, 0, 11, // Key type length

            115, 115, 104, 45, 101, 100, 50, 53, 53, 49, 57, // Key type

            0, 0, 0, 32, // Public key

            208, 232, 92, 138, 225, 114, 116, 99, 156, 177, 148, 93, 65, 93, 198, 25, 46, 203, 79,

            37, 145, 51, 176, 174, 61, 136, 160, 107, 4, 95, 175, 144, // Key

            0, 0, 0, 9, // Length of data to sign

            1, 2, 3, 4, 5, 6, 7, 8, 9, // Data to sign

            0, 0, 0, 0, // Signature flags

        ];

        let stream = DummyStream::default();

        let mut agent = AgentClient::new(None, stream.clone());

        let data: Vec<u8> = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];

        agent.sign(&pk, &data).ok();

        assert_eq!(

            stream.incoming.lock().unwrap().as_slice(),

            expected.as_slice()

        );

    }

}

pub use radicle_ssh as ssh;

pub use ssh::agent::client::{AgentClient, Error};

    client: AgentClient,

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

        Ok(Self {

            client: AgentClient::connect_env()?,

        })

    pub fn register(&mut self, key: &SecretKey) -> Result<(), ssh::Error> {

        self.client.add_identity(key, &[])

    pub fn unregister(&mut self, key: &PublicKey) -> Result<(), ssh::Error> {

        self.client.remove_identity(key)

    pub fn unregister_all(&mut self) -> Result<(), ssh::Error> {

    pub fn sign(&mut self, key: &PublicKey, data: &[u8]) -> Result<[u8; 64], ssh::Error> {

        self.client.sign(key, data)

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

        self.client.path()

    pub fn request_identities(&mut self) -> Result<Vec<PublicKey>, ssh::agent::client::Error> {

        self.client.request_identities()

    pub fn is_ready(&self) -> Result<bool, Error> {

use crate::{KeyPair, PublicKey, SecretKey, Seed, Signature, ssh::ExtendedSignature};

[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 }

                                 Apache License

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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::Constraint;

use crate::agent::msg;

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)