Allow retrieving peer SSH Protocol Version String

russh/src/client/mod.rs

@@ -697,6 +697,7 @@ where
             strict_kex: false,
             alive_timeouts: 0,
             received_data: false,
+            remote_sshid: sshid.into(),
         },
         session_receiver,
         session_sender,

russh/src/client/session.rs

@@ -268,7 +268,7 @@ impl Session {
     /// Requests a TCP/IP forwarding from the server
     ///
     /// If `reply_channel` is not None, sets want_reply and returns the server's response via the channel,
-    /// Some<u32> for a success message with port, or None for failure
+    /// [`Some<u32>`] for a success message with port, or [`None`] for failure
     pub fn tcpip_forward(
         &mut self,
         reply_channel: Option<oneshot::Sender<Option<u32>>>,
@@ -395,4 +395,17 @@ impl Session {
             0
         }
     }
+
+    /// Returns the SSH ID (Protocol Version + Software Version) the server sent when connecting
+    ///
+    /// This should contain only ASCII characters for implementations conforming to RFC4253, Section 4.2:
+    ///
+    /// > Both the 'protoversion' and 'softwareversion' strings MUST consist of
+    /// > printable US-ASCII characters, with the exception of whitespace
+    /// > characters and the minus sign (-).
+    ///
+    /// So it usually is fine to convert it to a `String` using `String::from_utf8_lossy`
+    pub fn remote_sshid(&self) -> &[u8] {
+        &self.common.remote_sshid
+    }
 }

russh/src/server/mod.rs

@@ -16,7 +16,7 @@
 //! # Writing servers
 //!
 //! There are two ways of accepting connections:
-//! * implement the [Server](server::Server) trait and let [run](server::run) handle everything
+//! * implement the [Server](server::Server) trait and let [run_on_socket](server::Server::run_on_socket)/[run_on_address](server::Server::run_on_address) handle everything
 //! * accept connections yourself and pass them to [run_stream](server::run_stream)
 //!
 //! In both cases, you'll first need to implement the [Handler](server::Handler) trait -
@@ -731,6 +731,7 @@ async fn read_ssh_id<R: AsyncRead + Unpin>(
         strict_kex: false,
         alive_timeouts: 0,
         received_data: false,
+        remote_sshid: sshid.into(),
     })
 }
 

russh/src/server/session.rs

@@ -1028,6 +1028,19 @@ impl Session {
         }
     }
 
+    /// Returns the SSH ID (Protocol Version + Software Version) the client sent when connecting
+    ///
+    /// This should contain only ASCII characters for implementations conforming to RFC4253, Section 4.2:
+    ///
+    /// > Both the 'protoversion' and 'softwareversion' strings MUST consist of
+    /// > printable US-ASCII characters, with the exception of whitespace
+    /// > characters and the minus sign (-).
+    ///
+    /// So it usually is fine to convert it to a [`String`] using [`String::from_utf8_lossy`]
+    pub fn remote_sshid(&self) -> &[u8] {
+        &self.common.remote_sshid
+    }
+
     pub(crate) fn maybe_send_ext_info(&mut self) {
         if let Some(ref mut enc) = self.common.encrypted {
             // If client sent a ext-info-c message in the kex list, it supports RFC 8308 extension negotiation.

russh/src/session.rs

@@ -54,6 +54,7 @@ pub(crate) struct Encrypted {
 
 pub(crate) struct CommonSession<Config> {
     pub auth_user: String,
+    pub remote_sshid: Vec<u8>,
     pub config: Config,
     pub encrypted: Option<Encrypted>,
     pub auth_method: Option<auth::Method>,