openssh-session-bind.patch

diff --git a/authfd.c b/authfd.c
index 9791b9e6b..21977658a 100644
--- a/authfd.c
+++ b/authfd.c
@@ -768,3 +768,41 @@ ssh_agent_bind_hostkey(int sock, const struct sshkey *key,
 	sshbuf_free(msg);
 	return r;
 }
+
+/*
+ * Sends host information to the agent via a custom extension.
+ * Includes the hostname, host key, session ID, and the server's KEX
+ * signature so the agent can verify the connection is authentic and
+ * display the target hostname when prompting for approval.
+ */
+int
+ssh_agent_bind_hostinfo(int sock, const char *hostname,
+    const struct sshkey *key, const struct sshbuf *session_id,
+    const struct sshbuf *signature, int forwarding)
+{
+	struct sshbuf *msg;
+	int r;
+
+	if (hostname == NULL || key == NULL ||
+	    session_id == NULL || signature == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((msg = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 ||
+	    (r = sshbuf_put_cstring(msg, "session-bind@pl.loee")) != 0 ||
+	    (r = sshbuf_put_cstring(msg, hostname)) != 0 ||
+	    (r = sshkey_puts(key, msg)) != 0 ||
+	    (r = sshbuf_put_stringb(msg, session_id)) != 0 ||
+	    (r = sshbuf_put_stringb(msg, signature)) != 0 ||
+	    (r = sshbuf_put_u8(msg, forwarding ? 1 : 0)) != 0)
+		goto out;
+	if ((r = ssh_request_reply_decode(sock, msg)) != 0) {
+		/* Agent may not support this extension; not fatal */
+		r = 0;
+		goto out;
+	}
+	r = 0;
+ out:
+	sshbuf_free(msg);
+	return r;
+}
diff --git a/authfd.h b/authfd.h
index da4830a96..ca06a1896 100644
--- a/authfd.h
+++ b/authfd.h
@@ -67,6 +67,10 @@ int	ssh_agent_bind_hostkey(int sock, const struct sshkey *key,
     const struct sshbuf *session_id, const struct sshbuf *signature,
     int forwarding);
 
+int	ssh_agent_bind_hostinfo(int sock, const char *hostname,
+    const struct sshkey *key, const struct sshbuf *session_id,
+    const struct sshbuf *signature, int forwarding);
+
 /* Messages for the authentication agent connection. */
 #define SSH_AGENTC_REQUEST_RSA_IDENTITIES	1
 #define SSH_AGENT_RSA_IDENTITIES_ANSWER		2
diff --git a/sshconnect.c b/sshconnect.c
index 4384277a6..3e400a37e 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1620,6 +1620,26 @@ ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
 	    ssh->kex->name != NULL && options.warn_weak_crypto &&
 	    !kex_is_pq_from_name(ssh->kex->name))
 		warn_nonpq_kex();
+
+	/* Send host info to agent before authentication */
+	if (ssh->kex != NULL && ssh->kex->initial_hostkey != NULL &&
+	    ssh->kex->session_id != NULL && ssh->kex->initial_sig != NULL) {
+		int agent_fd;
+
+		if (ssh_get_authentication_socket(&agent_fd) == 0) {
+			r = ssh_agent_bind_hostinfo(agent_fd, host,
+			    ssh->kex->initial_hostkey,
+			    ssh->kex->session_id,
+			    ssh->kex->initial_sig, 0);
+			if (r == 0)
+				debug("bound agent to host %s", host);
+			else
+				debug2("failed to bind agent to host: %s",
+				    ssh_err(r));
+			ssh_close_authentication_socket(agent_fd);
+		}
+	}
+
 	ssh_userauth2(ssh, local_user, server_user, host, sensitive);
 	free(local_user);
 	free(host);