Add ssh-agent native auth

src/bin/dosh-client.rs

@@ -19,6 +19,7 @@ use dosh::protocol::{
     Resize, ResumeRequest, SERVER_TO_CLIENT, TicketAttachBody, TicketAttachEnvelope,
     TicketAttachOkEnvelope,
 };
+use dosh::ssh_agent;
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::fs;
@@ -899,8 +900,13 @@ async fn try_native_auth(
         &hello,
         &server_hello.hello,
     )?;
-    let identity = load_first_native_identity(config, cli_identity, &ssh_config)?;
-    let auth = sign_user_auth(&identity, &hello, &server_hello.hello, Vec::new())?;
+    let auth = sign_native_user_auth(
+        config,
+        cli_identity,
+        &ssh_config,
+        &hello,
+        &server_hello.hello,
+    )?;
     let mut pending_id = [0u8; 16];
     pending_id.copy_from_slice(&server_hello.hello.auth_challenge[..16]);
     let auth_body = protocol::to_body(&NativeUserAuthBody { auth })?;
@@ -953,6 +959,33 @@ async fn try_native_auth(
     Ok((frame, cred))
 }
 
+fn sign_native_user_auth(
+    config: &dosh::config::ClientConfig,
+    cli_identity: Option<&Path>,
+    ssh_config: &SshConfig,
+    hello: &dosh::native::NativeClientHello,
+    server_hello: &dosh::native::NativeServerHello,
+) -> Result<dosh::native::NativeUserAuth> {
+    let mut errors = Vec::new();
+    if config.use_ssh_agent {
+        match ssh_agent::sign_user_auth_with_agent(hello, server_hello, Vec::new()) {
+            Ok(auth) => return Ok(auth),
+            Err(err) => errors.push(format!("ssh-agent: {err:#}")),
+        }
+    }
+
+    match load_first_native_identity(config, cli_identity, ssh_config) {
+        Ok(identity) => sign_user_auth(&identity, hello, server_hello, Vec::new()),
+        Err(err) => {
+            errors.push(format!("identity files: {err:#}"));
+            Err(anyhow!(
+                "native auth found no usable key: {}",
+                errors.join("; ")
+            ))
+        }
+    }
+}
+
 fn load_first_native_identity(
     config: &dosh::config::ClientConfig,
     cli_identity: Option<&Path>,