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, 25 insertions, 11 deletions

diff --git a/authfd.c b/authfd.c
index ab6305944..05fd45401 100644
--- a/authfd.c
+++ b/authfd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: authfd.c,v 1.120 2019/11/13 04:47:52 deraadt Exp $ */
+/* $OpenBSD: authfd.c,v 1.121 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
@@ -82,21 +82,16 @@ decode_reply(u_char type)
                 return SSH_ERR_INVALID_FORMAT;
 }
 
-/* Returns the number of the authentication fd, or -1 if there is none. */
+/*
+ * Opens an authentication socket at the provided path and stores the file
+ * descriptor in fdp. Returns 0 on success and an error on failure.
+ */
 int
-ssh_get_authentication_socket(int *fdp)
+ssh_get_authentication_socket_path(const char *authsocket, int *fdp)
 {
-        const char *authsocket;
         int sock, oerrno;
         struct sockaddr_un sunaddr;
 
-        if (fdp != NULL)
-                *fdp = -1;
-
-        authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
-        if (authsocket == NULL || *authsocket == '\0')
-                return SSH_ERR_AGENT_NOT_PRESENT;
-
         memset(&sunaddr, 0, sizeof(sunaddr));
         sunaddr.sun_family = AF_UNIX;
         strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
@@ -119,6 +114,25 @@ ssh_get_authentication_socket(int *fdp)
         return 0;
 }
 
+/*
+ * Opens the default authentication socket and stores the file descriptor in
+ * fdp. Returns 0 on success and an error on failure.
+ */
+int
+ssh_get_authentication_socket(int *fdp)
+{
+        const char *authsocket;
+
+        if (fdp != NULL)
+                *fdp = -1;
+
+        authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
+        if (authsocket == NULL || *authsocket == '\0')
+                return SSH_ERR_AGENT_NOT_PRESENT;
+
+        return ssh_get_authentication_socket_path(authsocket, fdp);
+}
+
 /* Communicate with agent: send request and read reply */
 static int
 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply)