-V, for fallback to openssh in SSH2 compatibility mode

2 files changed, 50 insertions, 28 deletions

diff --git a/usr.bin/ssh/sshd.8 b/usr.bin/ssh/sshd.8
index 309c50c7eda..c2162c0581c 100644
--- a/usr.bin/ssh/sshd.8
+++ b/usr.bin/ssh/sshd.8
@@ -9,7 +9,7 @@
 .\"
 .\" Created: Sat Apr 22 21:55:14 1995 ylo
 .\"
-.\" $Id: sshd.8,v 1.25 1999/11/19 09:46:49 markus Exp $
+.\" $Id: sshd.8,v 1.26 1999/11/22 20:02:45 markus Exp $
 .\"
 .Dd September 25, 1999
 .Dt SSHD 8
@@ -26,6 +26,7 @@
 .Op Fl h Ar host_key_file
 .Op Fl k Ar key_gen_time
 .Op Fl p Ar port
+.Op Fl V Ar client_protocol_id
 .Sh DESCRIPTION 
 .Nm
 (Secure Shell Daemon) is the daemon program for 
@@ -165,6 +166,13 @@ Quiet mode.  Nothing is sent to the system log.  Normally the beginning,
 authentication, and termination of each connection is logged.
 .It Fl Q
 Do not print an error message if RSA support is missing.
+.It Fl V Ar client_protocol_id
+SSH2 compatibility mode.
+When this options is specified
+.Nm
+assumes the client has sent the given version string
+and skips the
+Protocol Version Identification Exchange.
 .El
 .Sh CONFIGURATION FILE
 .Nm
diff --git a/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c
index d06372a19c6..afa9667058d 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 1.60 1999/11/20 20:07:23 deraadt Exp $");
+RCSID("$Id: sshd.c,v 1.61 1999/11/22 20:02:45 markus Exp $");
 
 #include "xmalloc.h"
 #include "rsa.h"
@@ -74,6 +74,10 @@ char **saved_argv;
    the SIGHUP signal handler. */
 int listen_sock;
 
+/* the client's version string, passed by sshd2 in compat mode.
+   if != NULL, sshd will skip the version-number exchange */
+char *client_version_string = NULL;
+
 /* Flags set in auth-rsa from authorized_keys flags.  These are set in
   auth-rsa.c. */
 int no_port_forwarding_flag = 0;
@@ -254,7 +258,7 @@ main(int ac, char **av)
   initialize_server_options(&options);
 
   /* Parse command-line arguments. */
-  while ((opt = getopt(ac, av, "f:p:b:k:h:g:diqQ")) != EOF)
+  while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ")) != EOF)
     {
       switch (opt)
 	{
@@ -289,6 +293,11 @@ main(int ac, char **av)
 	case 'h':
 	  options.host_key_file = optarg;
 	  break;
+	case 'V':
+	  client_version_string = optarg;
+	  /* only makes sense with inetd_flag, i.e. no listen() */
+	  inetd_flag = 1;
+	  break;
 	case '?':
 	default:
 	  fprintf(stderr, "sshd version %s\n", SSH_VERSION);
@@ -631,31 +640,36 @@ main(int ac, char **av)
   if (!debug_flag)
     alarm(options.login_grace_time);
 
-  /* Send our protocol version identification. */
-  snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", 
-	  PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
-  if (write(sock_out, buf, strlen(buf)) != strlen(buf))
-    fatal("Could not write ident string.");
-
-  /* Read other side\'s version identification. */
-  for (i = 0; i < sizeof(buf) - 1; i++)
-    {
-      if (read(sock_in, &buf[i], 1) != 1)
-	fatal("Did not receive ident string.");
-      if (buf[i] == '\r')
-	{
-	  buf[i] = '\n';
-	  buf[i + 1] = 0;
-	  break;
-	}
-      if (buf[i] == '\n')
-	{
-	  /* buf[i] == '\n' */
-	  buf[i + 1] = 0;
-	  break;
-	}
-    }
-  buf[sizeof(buf) - 1] = 0;
+  if (client_version_string != NULL) {
+     /* we are exec'ed by sshd2, so skip exchange of protocol version */
+     strlcpy(buf, client_version_string, sizeof(buf));
+  } else {
+    /* Send our protocol version identification. */
+    snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", 
+      	  PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
+    if (write(sock_out, buf, strlen(buf)) != strlen(buf))
+      fatal("Could not write ident string.");
+ 
+    /* Read other side\'s version identification. */
+    for (i = 0; i < sizeof(buf) - 1; i++)
+      {
+        if (read(sock_in, &buf[i], 1) != 1)
+      	fatal("Did not receive ident string.");
+        if (buf[i] == '\r')
+      	{
+      	  buf[i] = '\n';
+      	  buf[i + 1] = 0;
+      	  break;
+      	}
+        if (buf[i] == '\n')
+      	{
+      	  /* buf[i] == '\n' */
+      	  buf[i + 1] = 0;
+      	  break;
+      	}
+      }
+    buf[sizeof(buf) - 1] = 0;
+  }
   
   /* Check that the versions match.  In future this might accept several
      versions and set appropriate flags to handle them. */