diff --git a/libssh-rs/src/lib.rs b/libssh-rs/src/lib.rs index 4352ea5..dd4cef7 100644 --- a/libssh-rs/src/lib.rs +++ b/libssh-rs/src/lib.rs @@ -75,6 +75,7 @@ pub(crate) struct SessionHolder { sess: sys::ssh_session, callbacks: sys::ssh_callbacks_struct, auth_callback: Option) -> SshResult>>, + pending_agent_forward_channels: Vec, } unsafe impl Send for SessionHolder {} @@ -87,6 +88,7 @@ impl std::ops::Deref for SessionHolder { impl Drop for SessionHolder { fn drop(&mut self) { + self.clear_pending_agent_forward_channels(); unsafe { sys::ssh_free(self.sess); } @@ -157,6 +159,15 @@ impl SessionHolder { } } } + + fn clear_pending_agent_forward_channels(&mut self) { + for chan in self.pending_agent_forward_channels.drain(..) { + unsafe { + // We have no callbacks on these channels, no need to cleanup. + sys::ssh_channel_free(chan); + } + } + } } /// A Session represents the state needed to make a connection to @@ -201,6 +212,7 @@ impl Session { sess, callbacks, auth_callback: None, + pending_agent_forward_channels: Vec::new(), })); { @@ -274,6 +286,21 @@ impl Session { } } + unsafe extern "C" fn channel_open_request_auth_agent_callback( + session: sys::ssh_session, + userdata: *mut ::std::os::raw::c_void, + ) -> sys::ssh_channel { + let sess: &mut SessionHolder = &mut *(userdata as *mut SessionHolder); + let chan = sys::ssh_channel_new(session); + if chan.is_null() { + eprintln!("ssh_channel_new failed: {:?}", sess.last_error()); + return std::ptr::null_mut(); + } + // We are guarenteed to be holding a session lock here. + sess.pending_agent_forward_channels.push(chan); + chan + } + /// Sets a callback that is used by libssh when it needs to prompt /// for the passphrase during public key authentication. /// This is NOT used for password or keyboard interactive authentication. @@ -326,6 +353,30 @@ impl Session { sess.callbacks.auth_function = Some(Self::bridge_auth_callback); } + /// Enable or disable creating channels when the remote side requests a new channel for SSH + /// agent forwarding. + /// You are supposed to periodically check whether there's pending channels (already bound to + /// remote side's agent client) by using the `accept_agent_forward` function. + pub fn enable_accept_agent_forward(&self, enable: bool) { + let mut sess = self.lock_session(); + sess.callbacks.channel_open_request_auth_agent_function = if enable { + Some(Self::channel_open_request_auth_agent_callback) + } else { + sess.clear_pending_agent_forward_channels(); + // libssh denies auth agent channel requests with no callback set. + None + } + } + + // Accept an auth agent forward channel. + // Returns a `Channel` bound to the remote side SSH agent client, or `None` if no pending + // request from the server. + pub fn accept_agent_forward(&self) -> Option { + let mut sess = self.lock_session(); + let chan = sess.pending_agent_forward_channels.pop()?; + Some(Channel::new(&self.sess, chan)) + } + /// Create a new channel. /// Channels are used to handle I/O for commands and forwarded streams. pub fn new_channel(&self) -> SshResult {