upstream: Allow forwarding a different agent socket to the path

specified by $SSH_AUTH_SOCK, by extending the existing ForwardAgent option to
accepting an explicit path or the name of an environment variable in addition
to yes/no.

Patch by Eric Chiang, manpage by me; ok markus@

OpenBSD-Commit-ID: 98f2ed80bf34ea54d8b2ddd19ac14ebbf40e9265

1 files changed, 13 insertions, 2 deletions

diff --git a/clientloop.c b/clientloop.c
index 880abfda2..8f0332df4 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.329 2019/11/25 00:51:37 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.330 2019/12/21 02:19:13 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -135,6 +135,12 @@ extern int muxserver_sock; /* XXX use mux_client_cleanup() instead */
 extern char *host;
 
 /*
+ * If this field is not NULL, the ForwardAgent socket is this path and different
+ * instead of SSH_AUTH_SOCK.
+ */
+extern char *forward_agent_sock_path;
+
+/*
  * Flag to indicate that we have received a window change signal which has
  * not yet been processed.  This will cause a message indicating the new
  * window size to be sent to the server a little later.  This is volatile
@@ -1618,7 +1624,12 @@ client_request_agent(struct ssh *ssh, const char *request_type, int rchan)
                     "malicious server.");
                 return NULL;
         }
-        if ((r = ssh_get_authentication_socket(&sock)) != 0) {
+        if (forward_agent_sock_path == NULL) {
+                r = ssh_get_authentication_socket(&sock);
+        } else {
+                r = ssh_get_authentication_socket_path(forward_agent_sock_path, &sock);
+        }
+        if (r != 0) {
                 if (r != SSH_ERR_AGENT_NOT_PRESENT)
                         debug("%s: ssh_get_authentication_socket: %s",
                             __func__, ssh_err(r));