agent: Add ssh_set_agent_socket

Allow callers to specify their own socket
for an ssh agent.

Signed-off-by: Peter Volpe <pvolpe@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

include/libssh/libssh.h

@@ -588,6 +588,7 @@ LIBSSH_API int ssh_select(ssh_channel *channels, ssh_channel *outchannels, socke
     fd_set *readfds, struct timeval *timeout);
 LIBSSH_API int ssh_service_request(ssh_session session, const char *service);
 LIBSSH_API int ssh_set_agent_channel(ssh_session session, ssh_channel channel);
+LIBSSH_API int ssh_set_agent_socket(ssh_session session, socket_t fd);
 LIBSSH_API void ssh_set_blocking(ssh_session session, int blocking);
 LIBSSH_API void ssh_set_counters(ssh_session session, ssh_counter scounter,
                                  ssh_counter rcounter);

src/agent.c

@@ -185,15 +185,32 @@ int ssh_set_agent_channel(ssh_session session, ssh_channel channel){
   return SSH_OK;
 }
 
+/** @brief sets the SSH agent socket.
+ * The SSH agent will be used to authenticate this client using
+ * the given socket to communicate with the ssh-agent. The caller
+ * is responsible for connecting to the socket prior to calling
+ * this function.
+ * @returns SSH_OK in case of success
+ *          SSH_ERROR in case of an error
+ */
+int ssh_set_agent_socket(ssh_session session, socket_t fd){
+  if (!session)
+    return SSH_ERROR;
+  if (!session->agent){
+    ssh_set_error(session, SSH_REQUEST_DENIED, "Session has no active agent");
+    return SSH_ERROR;
+  }
+
+  ssh_socket_set_fd(session->agent->sock, fd);
+  return SSH_OK;
+}
 
 void agent_close(struct ssh_agent_struct *agent) {
   if (agent == NULL) {
     return;
   }
 
-  if (getenv("SSH_AUTH_SOCK")) {
-    ssh_socket_close(agent->sock);
-  }
+  ssh_socket_close(agent->sock);
 }
 
 void agent_free(ssh_agent agent) {