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, 33 insertions, 1 deletions

diff --git a/ssh.c b/ssh.c
index 13299f7d1..12760af29 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.509 2019/11/18 16:10:05 naddy Exp $ */
+/* $OpenBSD: ssh.c,v 1.510 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
@@ -168,6 +168,12 @@ char *config = NULL;
  */
 char *host;
 
+/*
+ * A config can specify a path to forward, overriding SSH_AUTH_SOCK. If this is
+ * not NULL, forward the socket at this path instead.
+ */
+char *forward_agent_sock_path = NULL;
+
 /* Various strings used to to percent_expand() arguments */
 static char thishost[NI_MAXHOST], shorthost[NI_MAXHOST], portstr[NI_MAXSERV];
 static char uidstr[32], *host_arg, *conn_hash_hex;
@@ -1498,6 +1504,32 @@ main(int ac, char **av)
                 }
         }
 
+        if (options.forward_agent && (options.forward_agent_sock_path != NULL)) {
+                p = tilde_expand_filename(options.forward_agent_sock_path, getuid());
+                cp = percent_expand(p,
+                    "d", pw->pw_dir,
+                    "h", host,
+                    "i", uidstr,
+                    "l", thishost,
+                    "r", options.user,
+                    "u", pw->pw_name,
+                    (char *)NULL);
+                free(p);
+
+                if (cp[0] == '$') {
+                        if (!valid_env_name(cp + 1)) {
+                                fatal("Invalid ForwardAgent environment variable name %s", cp);
+                        }
+                        if ((p = getenv(cp + 1)) != NULL)
+                                forward_agent_sock_path = p;
+                        else
+                                options.forward_agent = 0;
+                        free(cp);
+                } else {
+                        forward_agent_sock_path = cp;
+                }
+        }
+
         /* Expand ~ in known host file names. */
         tilde_expand_paths(options.system_hostfiles,
             options.num_system_hostfiles);