fix old connect() race security-bug for ssh-agent and agent-forwarding

by removing the connect() junk, with the following restrictions:
1) change the version to "OpenSSH-1.1":
   agent-forwarding will work only between OpenSSH-1.1 client and
   OpenSSH-1.1 server
2) renamed the environment variable of OpenSSH-1.1 to
   "SSH_AUTH_SOCKET", since useing OpenSSH-1.0 ssh-add against the new
   ssh-agent does not work

11 files changed, 80 insertions, 267 deletions

diff --git a/usr.bin/ssh/authfd.c b/usr.bin/ssh/authfd.c
index 6fc51c347b6..b70a824a2c1 100644
--- a/usr.bin/ssh/authfd.c
+++ b/usr.bin/ssh/authfd.c
@@ -14,7 +14,7 @@ Functions for connecting the local authentication agent.
 */
 
 #include "includes.h"
-RCSID("$Id: authfd.c,v 1.7 1999/10/05 22:18:52 markus Exp $");
+RCSID("$Id: authfd.c,v 1.8 1999/10/14 18:17:41 markus Exp $");
 
 #include "ssh.h"
 #include "rsa.h"
@@ -29,7 +29,7 @@ RCSID("$Id: authfd.c,v 1.7 1999/10/05 22:18:52 markus Exp $");
 /* Returns the number of the authentication fd, or -1 if there is none. */
 
 int
-ssh_get_authentication_fd()
+ssh_get_authentication_socket()
 {
   const char *authsocket;
   int sock;
@@ -57,7 +57,7 @@ ssh_get_authentication_fd()
 
 /* Closes the agent socket if it should be closed (depends on how it was
    obtained).  The argument must have been returned by 
-   ssh_get_authentication_fd(). */
+   ssh_get_authentication_socket(). */
 
 void ssh_close_authentication_socket(int sock)
 {
@@ -65,95 +65,6 @@ void ssh_close_authentication_socket(int sock)
     close(sock);
 }
 
-/* Dummy alarm used to prevent waiting for connection from the
-   authentication agent indefinitely. */
-
-static void dummy_alarm_handler(int sig)
-{
-  /* Do nothing; a cought signal will just cause accept to return. */
-}
-
-/* Opens a socket to the authentication server.  Returns the number of
-   that socket, or -1 if no connection could be made. */
-
-int ssh_get_authentication_connection_fd()
-{
-  int authfd;
-  int listen_sock, sock, port, addrlen;
-  int old_timeout;
-  void (*old_handler)();
-  struct sockaddr_in sin;
-  char msg[3];
-
-  /* Get the the socket number from the environment.  This is the socket
-     used to obtain the real authentication socket. */
-  authfd = ssh_get_authentication_fd();
-  if (authfd == -1)
-    return -1;
-
-  /* Create a local socket for listening. */
-  listen_sock = socket(AF_INET, SOCK_STREAM, 0);
-  if (listen_sock == -1)
-    {
-      ssh_close_authentication_socket(authfd);
-      return -1;
-    }
-
-  /* Bind the socket to random unprivileged port. */
-  memset(&sin, 0, sizeof(sin));
-  sin.sin_family = AF_INET;
-  do
-    {
-      port = 32768 + (rand() % 30000);
-      sin.sin_port = htons(port);
-    }
-  while (bind(listen_sock, (struct sockaddr *)&sin, sizeof(sin)) < 0 &&
-	 errno == EADDRINUSE);
-  
-  /* Start listening for connections on the socket. */
-  if (listen(listen_sock, 1) < 0)
-    {
-      error("listen: %.100s", strerror(errno));
-      close(listen_sock);
-      ssh_close_authentication_socket(authfd);
-      return -1;
-    }
-
-  /* Send a message to the authentication fd requesting the agent or its
-     local representative to connect to the given socket.  Note that
-     we use send() to get the packet sent atomically (there can be several
-     clients trying to use the same authentication fd simultaneously). */
-  msg[0] = (char)SSH_AUTHFD_CONNECT;
-  PUT_16BIT(msg + 1, port);
-  if (send(authfd, msg, 3, 0) < 0)
-    {
-      shutdown(listen_sock, SHUT_RDWR);
-      close(listen_sock);
-      ssh_close_authentication_socket(authfd);
-      return -1;
-    }
-
-  /* Setup a timeout so we won't wait for the connection indefinitely. */
-  old_timeout = alarm(120);
-  old_handler = signal(SIGALRM, dummy_alarm_handler);
-  
-  /* Wait for the connection from the agent or its representative. */
-  addrlen = sizeof(sin);
-  sock = accept(listen_sock, (struct sockaddr *)&sin, &addrlen);
-
-  /* Remove the alarm (restore its old values). */
-  alarm(old_timeout);
-  signal(SIGALRM, old_handler);
-
-  /* Close the socket we used for listening.  It is no longer needed.
-     (The authentication fd and the new connection still remain open.) */
-  shutdown(listen_sock, SHUT_RDWR);
-  close(listen_sock);
-  ssh_close_authentication_socket(authfd);
-
-  return sock;
-}  
-
 /* Opens and connects a private socket for communication with the
    authentication agent.  Returns the file descriptor (which must be
    shut down and closed by the caller when no longer needed).
@@ -165,8 +76,7 @@ AuthenticationConnection *ssh_get_authentication_connection()
   AuthenticationConnection *auth;
   int sock;
   
-  /* Get a connection to the authentication agent. */
-  sock = ssh_get_authentication_connection_fd();
+  sock = ssh_get_authentication_socket();
 
   /* Fail if we couldn't obtain a connection.  This happens if we exited
      due to a timeout. */
@@ -191,6 +101,8 @@ void ssh_close_authentication_connection(AuthenticationConnection *ac)
   buffer_free(&ac->packet);
   buffer_free(&ac->identities);
   close(ac->fd);
+  /* Free the connection data structure. */
+  xfree(ac);
 }
 
 /* Returns the first authentication identity held by the agent.
@@ -651,19 +563,3 @@ int ssh_remove_all_identities(AuthenticationConnection *auth)
   /*NOTREACHED*/
   return 0;
 }  
-
-/* Closes the connection to the authentication agent. */
-
-void ssh_close_authentication(AuthenticationConnection *auth)
-{
-  /* Close the connection. */
-  shutdown(auth->fd, SHUT_RDWR);
-  close(auth->fd);
-
-  /* Free the buffers. */
-  buffer_free(&auth->packet);
-  buffer_free(&auth->identities);
-
-  /* Free the connection data structure. */
-  xfree(auth);
-}
diff --git a/usr.bin/ssh/authfd.h b/usr.bin/ssh/authfd.h
index f889830b820..5f362e02a74 100644
--- a/usr.bin/ssh/authfd.h
+++ b/usr.bin/ssh/authfd.h
@@ -13,16 +13,13 @@ Functions to interface with the SSH_AUTHENTICATION_FD socket.
 
 */
 
-/* RCSID("$Id: authfd.h,v 1.2 1999/09/28 04:45:35 provos Exp $"); */
+/* RCSID("$Id: authfd.h,v 1.3 1999/10/14 18:17:42 markus Exp $"); */
 
 #ifndef AUTHFD_H
 #define AUTHFD_H
 
 #include "buffer.h"
 
-/* Message types for SSH_AUTHENTICATION_FD socket. */
-#define SSH_AUTHFD_CONNECT	0xf0
-
 /* Messages for the authentication agent connection. */
 #define SSH_AGENTC_REQUEST_RSA_IDENTITIES	1
 #define SSH_AGENT_RSA_IDENTITIES_ANSWER		2
@@ -43,17 +40,13 @@ typedef struct
 } AuthenticationConnection;
 
 /* Returns the number of the authentication fd, or -1 if there is none. */
-int ssh_get_authentication_fd();
+int ssh_get_authentication_socket();
 
 /* This should be called for any descriptor returned by 
-   ssh_get_authentication_fd().  Depending on the way the descriptor was
+   ssh_get_authentication_socket().  Depending on the way the descriptor was
    obtained, this may close the descriptor. */
 void ssh_close_authentication_socket(int authfd);
 
-/* Opens a socket to the authentication server.  Returns the number of
-   that socket, or -1 if no connection could be made. */
-int ssh_get_authentication_connection_fd();
-
 /* Opens and connects a private socket for communication with the
    authentication agent.  Returns NULL if an error occurred and the 
    connection could not be opened.  The connection should be closed by
diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c
index 7b70f115df9..a0eb88f6c91 100644
--- a/usr.bin/ssh/channels.c
+++ b/usr.bin/ssh/channels.c
@@ -16,7 +16,7 @@ arbitrary tcp/ip connections, and the authentication agent connection.
 */
 
 #include "includes.h"
-RCSID("$Id: channels.c,v 1.12 1999/10/05 22:18:52 markus Exp $");
+RCSID("$Id: channels.c,v 1.13 1999/10/14 18:17:42 markus Exp $");
 
 #include "ssh.h"
 #include "packet.h"
@@ -36,9 +36,9 @@ RCSID("$Id: channels.c,v 1.12 1999/10/05 22:18:52 markus Exp $");
 #define SSH_CHANNEL_OPENING		3 /* waiting for confirmation */
 #define SSH_CHANNEL_OPEN		4 /* normal open two-way channel */
 #define SSH_CHANNEL_CLOSED		5 /* waiting for close confirmation */
-#define SSH_CHANNEL_AUTH_FD		6 /* authentication fd */
+/*	SSH_CHANNEL_AUTH_FD		6    authentication fd */
 #define SSH_CHANNEL_AUTH_SOCKET		7 /* authentication socket */
-#define SSH_CHANNEL_AUTH_SOCKET_FD	8 /* connection to auth socket */
+/*	SSH_CHANNEL_AUTH_SOCKET_FD	8    connection to auth socket */
 #define SSH_CHANNEL_X11_OPEN		9 /* reading first X11 packet */
 #define SSH_CHANNEL_INPUT_DRAINING	10 /* sending remaining data to conn */
 #define SSH_CHANNEL_OUTPUT_DRAINING	11 /* sending remaining data to app */
@@ -222,8 +222,6 @@ void channel_prepare_select(fd_set *readset, fd_set *writeset)
 	case SSH_CHANNEL_X11_LISTENER:
 	case SSH_CHANNEL_PORT_LISTENER:
 	case SSH_CHANNEL_AUTH_SOCKET:
-	case SSH_CHANNEL_AUTH_SOCKET_FD:
-	case SSH_CHANNEL_AUTH_FD:
 	  FD_SET(ch->sock, readset);
 	  break;
 
@@ -350,7 +348,7 @@ void channel_prepare_select(fd_set *readset, fd_set *writeset)
 void channel_after_select(fd_set *readset, fd_set *writeset)
 {
   struct sockaddr addr;
-  int addrlen, newsock, i, newch, len, port;
+  int addrlen, newsock, i, newch, len;
   Channel *ch;
   char buf[16384], *remote_hostname;
   
@@ -417,40 +415,25 @@ void channel_after_select(fd_set *readset, fd_set *writeset)
 	    }
 	  break;
 
-	case SSH_CHANNEL_AUTH_FD:
-	  /* This is the authentication agent file descriptor.  It is used to
-	     obtain the real connection to the agent. */
-	case SSH_CHANNEL_AUTH_SOCKET_FD:
-	  /* This is the temporary connection obtained by connecting the
-	     authentication agent socket. */
-	  if (FD_ISSET(ch->sock, readset))
-	    {
-	      len = recv(ch->sock, buf, sizeof(buf), 0);
-	      if (len <= 0)
-		{
-		  channel_free(i);
-		  break;
-		}
-	      if (len != 3 || (unsigned char)buf[0] != SSH_AUTHFD_CONNECT)
-		break; /* Ignore any messages of wrong length or type. */
-	      port = 256 * (unsigned char)buf[1] + (unsigned char)buf[2];
-	      packet_start(SSH_SMSG_AGENT_OPEN);
-	      packet_put_int(port);
-	      packet_send();
-	    }
-	  break;
-
 	case SSH_CHANNEL_AUTH_SOCKET:
 	  /* This is the authentication agent socket listening for connections
 	     from clients. */
 	  if (FD_ISSET(ch->sock, readset))
 	    {
+	      int nchan;
 	      len = sizeof(addr);
 	      newsock = accept(ch->sock, &addr, &len);
 	      if (newsock < 0)
-		error("Accept from authentication socket failed");
-	      (void)channel_allocate(SSH_CHANNEL_AUTH_SOCKET_FD, newsock,
+		{
+		  error("accept from auth socket: %.100s", strerror(errno));
+		  break;
+		}
+
+	      nchan = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 				     xstrdup("accepted auth socket"));
+	      packet_start(SSH_SMSG_AGENT_OPEN);
+	      packet_put_int(nchan);
+	      packet_send();
 	    }
 	  break;
 
@@ -592,8 +575,6 @@ int channel_not_very_much_buffered_data()
 	case SSH_CHANNEL_X11_LISTENER:
 	case SSH_CHANNEL_PORT_LISTENER:
 	case SSH_CHANNEL_AUTH_SOCKET:
-	case SSH_CHANNEL_AUTH_SOCKET_FD:
-	case SSH_CHANNEL_AUTH_FD:
 	  continue;
 	case SSH_CHANNEL_OPEN:
 	  if (buffer_len(&ch->input) > 32768)
@@ -762,9 +743,7 @@ int channel_still_open()
       case SSH_CHANNEL_X11_LISTENER:
       case SSH_CHANNEL_PORT_LISTENER:
       case SSH_CHANNEL_CLOSED:
-      case SSH_CHANNEL_AUTH_FD:
       case SSH_CHANNEL_AUTH_SOCKET:
-      case SSH_CHANNEL_AUTH_SOCKET_FD:
 	continue;
       case SSH_CHANNEL_OPENING:
       case SSH_CHANNEL_OPEN:
@@ -799,9 +778,7 @@ char *channel_open_message()
       case SSH_CHANNEL_X11_LISTENER:
       case SSH_CHANNEL_PORT_LISTENER:
       case SSH_CHANNEL_CLOSED:
-      case SSH_CHANNEL_AUTH_FD:
       case SSH_CHANNEL_AUTH_SOCKET:
-      case SSH_CHANNEL_AUTH_SOCKET_FD:
 	continue;
       case SSH_CHANNEL_OPENING:
       case SSH_CHANNEL_OPEN:
@@ -1437,22 +1414,26 @@ void auth_input_request_forwarding(struct passwd *pw)
 
 void auth_input_open_request()
 {
-  int port, sock, newch;
+  int remch, sock, newch;
   char *dummyname;
 
-  /* Read the port number from the message. */
-  port = packet_get_int();
+  /* Read the remote channel number from the message. */
+  remch = packet_get_int();
   
   /* Get a connection to the local authentication agent (this may again get
      forwarded). */
-  sock = ssh_get_authentication_connection_fd();
+  sock = ssh_get_authentication_socket();
 
-  /* If we could not connect the agent, just return.  This will cause the
-     client to timeout and fail.  This should never happen unless the agent
+  /* If we could not connect the agent, send an error message back to
+     the server. This should never happen unless the agent
      dies, because authentication forwarding is only enabled if we have an
      agent. */
-  if (sock < 0)
+  if (sock < 0){
+    packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
+    packet_put_int(remch);
+    packet_send();
     return;
+  }
 
   debug("Forwarding authentication connection.");
 
@@ -1461,15 +1442,12 @@ void auth_input_open_request()
      yet be freed at that point. */
   dummyname = xstrdup("authentication agent connection");
   
-  /* Allocate a channel for the new connection. */
-  newch = channel_allocate(SSH_CHANNEL_OPENING, sock, dummyname);
-
-  /* Fake a forwarding request. */
-  packet_start(SSH_MSG_PORT_OPEN);
+  newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
+  channels[newch].remote_id = remch;
+  
+  /* Send a confirmation to the remote host. */
+  packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
+  packet_put_int(remch);
   packet_put_int(newch);
-  packet_put_string("localhost", strlen("localhost"));
-  packet_put_int(port);
-  if (have_hostname_in_open)
-    packet_put_string(dummyname, strlen(dummyname));
   packet_send();
 }
diff --git a/usr.bin/ssh/ssh-agent.1 b/usr.bin/ssh/ssh-agent.1
index a9ae86224ac..c69517d8492 100644
--- a/usr.bin/ssh/ssh-agent.1
+++ b/usr.bin/ssh/ssh-agent.1
@@ -9,7 +9,7 @@
 .\"
 .\" Created: Sat Apr 23 20:10:43 1995 ylo
 .\"
-.\" $Id: ssh-agent.1,v 1.3 1999/10/02 13:10:26 deraadt Exp $
+.\" $Id: ssh-agent.1,v 1.4 1999/10/14 18:17:42 markus Exp $
 .\"
 .Dd September 25, 1999
 .Dt SSH-AGENT 1
@@ -58,27 +58,15 @@ However, the connection to the agent is forwarded over SSH
 remote logins, and the user can thus use the privileges given by the
 identities anywhere in the network in a secure way.
 .Pp
-A connection to the agent is inherited by child programs. 
-There are two alternative
-methods for inheriting the agent.  The preferred method is to have an
-open file descriptor which is inherited, and have an environment
-variable
-.Pq Ev SSH_AUTHENTICATION_FD
-contain the number of this
-descriptor.  This restricts access to the authentication agent to only
-those programs that are siblings of the agent, and it is fairly
-difficult even for root to get unauthorized access to the agent.
-.Pp
-On some machines, an alternative method is used.  A unix-domain
-socket is created
-.Pq Pa /tmp/ssh_agent.* ,
+A connection to the agent is inherited by child programs:
+A unix-domain socket is created
+.Pq Pa /tmp/ssh-XXXX/agent.<pid> ,
 and the name of this socket is stored in the
-.Ev SSH_AUTHENTICATION_SOCKET
+.Ev SSH_AUTH_SOCKET
 environment
 variable.  The socket is made accessible only to the current user.
 This method is easily abused by root or another instance of the same
-user.  The socket is only used if ssh is unable to find a file
-descriptor that would not be closed by shells.
+user.
 .Pp
 The agent exits automatically when the command given on the command
 line terminates.
@@ -94,7 +82,7 @@ is not used by
 but is normally added to the agent using
 .Xr ssh-add 1
 at login time.
-.It Pa /tmp/ssh_agent.<pid>
+.It Pa /tmp/ssh-XXXX/agent.<pid> ,
 Unix-domain sockets used to contain the connection to the
 authentication agent.  These sockets should only be readable by the
 owner.  The sockets should get automatically removed when the agent
diff --git a/usr.bin/ssh/ssh-agent.c b/usr.bin/ssh/ssh-agent.c
index 24ad6179513..9d2ad675e53 100644
--- a/usr.bin/ssh/ssh-agent.c
+++ b/usr.bin/ssh/ssh-agent.c
@@ -14,7 +14,7 @@ The authentication agent program.
 */
 
 #include "includes.h"
-RCSID("$Id: ssh-agent.c,v 1.11 1999/10/07 22:46:32 markus Exp $");
+RCSID("$Id: ssh-agent.c,v 1.12 1999/10/14 18:17:42 markus Exp $");
 
 #include "ssh.h"
 #include "rsa.h"
@@ -31,8 +31,7 @@ RCSID("$Id: ssh-agent.c,v 1.11 1999/10/07 22:46:32 markus Exp $");
 typedef struct
 {
   int fd;
-  enum { AUTH_UNUSED, AUTH_FD, AUTH_SOCKET, AUTH_SOCKET_FD, 
-    AUTH_CONNECTION } type;
+  enum { AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION } type;
   Buffer input;
   Buffer output;
 } SocketEntry;
@@ -324,6 +323,7 @@ process_message(SocketEntry *e)
     return;
   buffer_consume(&e->input, 4);
   type = buffer_get_char(&e->input);
+
   switch (type)
     {
     case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
@@ -391,10 +391,8 @@ prepare_select(fd_set *readset, fd_set *writeset)
   for (i = 0; i < sockets_alloc; i++)
     switch (sockets[i].type)
       {
-      case AUTH_FD:
-      case AUTH_CONNECTION:
       case AUTH_SOCKET:
-      case AUTH_SOCKET_FD:
+      case AUTH_CONNECTION:
 	FD_SET(sockets[i].fd, readset);
 	if (buffer_len(&sockets[i].output) > 0)
 	  FD_SET(sockets[i].fd, writeset);
@@ -410,9 +408,8 @@ prepare_select(fd_set *readset, fd_set *writeset)
 void after_select(fd_set *readset, fd_set *writeset)
 {
   unsigned int i;
-  int len, sock, port;
+  int len, sock;
   char buf[1024];
-  struct sockaddr_in sin;
   struct sockaddr_un sunaddr;
 
   for (i = 0; i < sockets_alloc; i++)
@@ -420,39 +417,6 @@ void after_select(fd_set *readset, fd_set *writeset)
       {
       case AUTH_UNUSED:
 	break;
-      case AUTH_FD:
-	if (FD_ISSET(sockets[i].fd, readset))
-	  {
-	    len = recv(sockets[i].fd, buf, sizeof(buf), 0);
-	    if (len <= 0)
-	      { /* All instances of the other side have been closed. */
-		log("Authentication agent exiting.");
-		exit(0);
-	      }
-	  process_auth_fd_input:
-	    if (len != 3 || (unsigned char)buf[0] != SSH_AUTHFD_CONNECT)
-	      break; /* Incorrect message; ignore it. */
-	    /* It is a connection request message. */
-	    port = (unsigned char)buf[1] * 256 + (unsigned char)buf[2];
-	    memset(&sin, 0, sizeof(sin));
-	    sin.sin_family = AF_INET;
-	    sin.sin_addr.s_addr = htonl(0x7f000001); /* localhost */
-	    sin.sin_port = htons(port);
-	    sock = socket(AF_INET, SOCK_STREAM, 0);
-	    if (sock < 0)
-	      {
-		perror("socket");
-		break;
-	      }
-	    if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
-	      {
-		perror("connecting to port requested in authfd message");
-		close(sock);
-		break;
-	      }
-	    new_socket(AUTH_CONNECTION, sock);
-	  }
-	break;
       case AUTH_SOCKET:
 	if (FD_ISSET(sockets[i].fd, readset))
 	  {
@@ -463,21 +427,7 @@ void after_select(fd_set *readset, fd_set *writeset)
 		perror("accept from AUTH_SOCKET");
 		break;
 	      }
-	    new_socket(AUTH_SOCKET_FD, sock);
-	  }
-	break;
-      case AUTH_SOCKET_FD:
-	if (FD_ISSET(sockets[i].fd, readset))
-	  {
-	    len = recv(sockets[i].fd, buf, sizeof(buf), 0);
-	    if (len <= 0)
-	      { /* The other side has closed the socket. */
-		shutdown(sockets[i].fd, SHUT_RDWR);
-		close(sockets[i].fd);
-		sockets[i].type = AUTH_UNUSED;
-		break;
-	      }
-	    goto process_auth_fd_input;
+	    new_socket(AUTH_CONNECTION, sock);
 	  }
 	break;
       case AUTH_CONNECTION:
@@ -568,7 +518,7 @@ main(int ac, char **av)
      the authentication agent. */
   if (fork() != 0)
     { /* Parent - execute the given command. */
-      setenv("SSH_AUTHENTICATION_SOCKET", socket_name, 1);
+      setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1);
       execvp(av[1], av + 1);
       perror(av[1]);
       exit(1);
diff --git a/usr.bin/ssh/ssh.1 b/usr.bin/ssh/ssh.1
index 35df1040a50..ab7da01c501 100644
--- a/usr.bin/ssh/ssh.1
+++ b/usr.bin/ssh/ssh.1
@@ -9,7 +9,7 @@
 .\"
 .\" Created: Sat Apr 22 21:55:14 1995 ylo
 .\"
-.\" $Id: ssh.1,v 1.16 1999/10/12 21:04:22 markus Exp $
+.\" $Id: ssh.1,v 1.17 1999/10/14 18:17:42 markus Exp $
 .\"
 .Dd September 25, 1999
 .Dt SSH 1
@@ -745,16 +745,9 @@ Set to the default
 .Ev PATH ,
 as specified when compiling
 .Nm ssh .
-.It Ev SSH_AUTHENTICATION_FD
-This is set to an integer value if you are using the authentication
-agent and a connection to it has been forwarded.  The value indicates
-a file descriptor number used for communicating with the agent.  On
-some systems, 
-.Ev SSH_AUTHENTICATION_SOCKET
-may be used instead to
-indicate the path of a unix-domain socket used to communicate with the
-agent (this method is less secure, and is only used on systems that
-don't support the first method).
+.It Ev SSH_AUTH_SOCKET
+indicates the path of a unix-domain socket used to communicate with the
+agent.
 .It Ev SSH_CLIENT
 Identifies the client end of the connection.  The variable contains
 three space-separated values: client ip-address, client port number,
diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c
index 9fce3199b8b..163eb8787cf 100644
--- a/usr.bin/ssh/ssh.c
+++ b/usr.bin/ssh/ssh.c
@@ -18,7 +18,7 @@ Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada.
 */
 
 #include "includes.h"
-RCSID("$Id: ssh.c,v 1.23 1999/10/12 21:04:22 markus Exp $");
+RCSID("$Id: ssh.c,v 1.24 1999/10/14 18:17:42 markus Exp $");
 
 #include "xmalloc.h"
 #include "ssh.h"
@@ -736,7 +736,7 @@ main(int ac, char **av)
   packet_set_interactive(interactive, options.keepalives);
 
   /* Clear agent forwarding if we don\'t have an agent. */
-  authfd = ssh_get_authentication_fd();
+  authfd = ssh_get_authentication_socket();
   if (authfd < 0)
     options.forward_agent = 0;
   else
diff --git a/usr.bin/ssh/ssh.h b/usr.bin/ssh/ssh.h
index e638acfef6b..d7a568fa555 100644
--- a/usr.bin/ssh/ssh.h
+++ b/usr.bin/ssh/ssh.h
@@ -13,7 +13,7 @@ Generic header file for ssh.
 
 */
 
-/* RCSID("$Id: ssh.h,v 1.10 1999/10/11 20:00:36 markus Exp $"); */
+/* RCSID("$Id: ssh.h,v 1.11 1999/10/14 18:17:42 markus Exp $"); */
 
 #ifndef SSH_H
 #define SSH_H
@@ -118,7 +118,7 @@ only by root, whereas ssh_config should be world-readable. */
 
 /* Name of the environment variable containing the pathname of the
    authentication socket. */
-#define SSH_AUTHSOCKET_ENV_NAME	"SSH_AUTHENTICATION_SOCKET"
+#define SSH_AUTHSOCKET_ENV_NAME	"SSH_AUTH_SOCKET"
 
 /* Force host key length and server key length to differ by at least this
    many bits.  This is to make double encryption with rsaref work. */
diff --git a/usr.bin/ssh/sshconnect.c b/usr.bin/ssh/sshconnect.c
index c7167568a0d..29b16b31d63 100644
--- a/usr.bin/ssh/sshconnect.c
+++ b/usr.bin/ssh/sshconnect.c
@@ -15,7 +15,7 @@ login (authentication) dialog.
 */
 
 #include "includes.h"
-RCSID("$Id: sshconnect.c,v 1.16 1999/10/06 20:07:42 dugsong Exp $");
+RCSID("$Id: sshconnect.c,v 1.17 1999/10/14 18:17:42 markus Exp $");
 
 #include <ssl/bn.h>
 #include "xmalloc.h"
@@ -886,6 +886,7 @@ void ssh_exchange_identification()
   int remote_major, remote_minor, i;
   int connection_in = packet_get_connection_in();
   int connection_out = packet_get_connection_out();
+  extern Options options;
 
   /* Read other side\'s version identification. */
   for (i = 0; i < sizeof(buf) - 1; i++)
@@ -913,6 +914,13 @@ void ssh_exchange_identification()
     fatal("Bad remote protocol version identification: '%.100s'", buf);
   debug("Remote protocol version %d.%d, remote software version %.100s",
 	remote_major, remote_minor, remote_version);
+
+  if (options.forward_agent && strcmp(remote_version, SSH_VERSION) != 0)
+    {
+      log("Agent forwarding disabled, remote version is not '%s'.",
+	    SSH_VERSION);
+      options.forward_agent = 0;
+    }
 #if 0
   /* Removed for now, to permit compatibility with latter versions.  The server
      will reject our version and disconnect if it doesn't support it. */
diff --git a/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c
index 74744bce259..604fd9c0098 100644
--- a/usr.bin/ssh/sshd.c
+++ b/usr.bin/ssh/sshd.c
@@ -18,7 +18,7 @@ agent connections.
 */
 
 #include "includes.h"
-RCSID("$Id: sshd.c,v 1.30 1999/10/12 18:11:55 markus Exp $");
+RCSID("$Id: sshd.c,v 1.31 1999/10/14 18:17:42 markus Exp $");
 
 #include "xmalloc.h"
 #include "rsa.h"
@@ -713,6 +713,13 @@ main(int ac, char **av)
   if (remote_major == 1 && remote_minor == 0)
     packet_disconnect("Your ssh version is too old and is no longer supported.  Please install a newer version.");
 
+  if (strcmp(remote_version, SSH_VERSION) != 0)
+    {
+      debug("Agent forwarding disabled, remote version is not '%s'.",
+	    SSH_VERSION);
+      no_agent_forwarding_flag = 1;
+    }
+
   /* Check whether logins are permitted from this host. */
   if (options.num_allow_hosts > 0)
     {
diff --git a/usr.bin/ssh/version.h b/usr.bin/ssh/version.h
index beca9efff36..2d83dc3983d 100644
--- a/usr.bin/ssh/version.h
+++ b/usr.bin/ssh/version.h
@@ -1 +1 @@
-#define SSH_VERSION	"OpenSSH-1.0"
+#define SSH_VERSION	"OpenSSH-1.1"