Implement DebianBanner server configuration flag that can be set to "no"

to allow sshd to run without the Debian-specific extra version in the
initial protocol handshake (closes: #562048).

6 files changed, 27 insertions, 3 deletions

diff --git a/debian/changelog b/debian/changelog
index 4207281e8..2793110f0 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,5 +1,6 @@
 openssh (1:5.2p1-2) UNRELEASED; urgency=low
 
+  [ Colin Watson ]
   * Backport from upstream:
     - After sshd receives a SIGHUP, ignore subsequent HUPs while sshd
       re-execs itself.  Prevents two HUPs in quick succession from resulting
@@ -11,6 +12,11 @@ openssh (1:5.2p1-2) UNRELEASED; urgency=low
     release of Debian dropped support for Linux 2.4, let alone 2.0, so this
     very likely has no remaining users depending on it.
 
+  [ Kees Cook ]
+  * Implement DebianBanner server configuration flag that can be set to "no"
+    to allow sshd to run without the Debian-specific extra version in the
+    initial protocol handshake (closes: #562048).
+
  -- Colin Watson <cjwatson@debian.org>  Sun, 10 Jan 2010 22:06:28 +0000
 
 openssh (1:5.2p1-1) unstable; urgency=low
diff --git a/servconf.c b/servconf.c
index c1f2bc2af..dd5161ecd 100644
--- a/servconf.c
+++ b/servconf.c
@@ -132,6 +132,7 @@ initialize_server_options(ServerOptions *options)
         options->adm_forced_command = NULL;
         options->chroot_directory = NULL;
         options->zero_knowledge_password_authentication = -1;
+        options->debian_banner = -1;
 }
 
 void
@@ -273,6 +274,8 @@ fill_default_server_options(ServerOptions *options)
                 options->permit_tun = SSH_TUNMODE_NO;
         if (options->zero_knowledge_password_authentication == -1)
                 options->zero_knowledge_password_authentication = 0;
+        if (options->debian_banner == -1)
+                options->debian_banner = 1;
 
         /* Turn privilege separation on by default */
         if (use_privsep == -1)
@@ -320,6 +323,7 @@ typedef enum {
         sMatch, sPermitOpen, sForceCommand, sChrootDirectory,
         sUsePrivilegeSeparation, sAllowAgentForwarding,
         sZeroKnowledgePasswordAuthentication,
+        sDebianBanner,
         sDeprecated, sUnsupported
 } ServerOpCodes;
 
@@ -449,6 +453,7 @@ static struct {
         { "permitopen", sPermitOpen, SSHCFG_ALL },
         { "forcecommand", sForceCommand, SSHCFG_ALL },
         { "chrootdirectory", sChrootDirectory, SSHCFG_ALL },
+        { "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
         { NULL, sBadOption, 0 }
 };
 
@@ -1335,6 +1340,10 @@ process_server_config_line(ServerOptions *options, char *line,
                         *charptr = xstrdup(arg);
                 break;
 
+        case sDebianBanner:
+                intptr = &options->debian_banner;
+                goto parse_int;
+
         case sDeprecated:
                 logit("%s line %d: Deprecated option %s",
                     filename, linenum, arg);
diff --git a/servconf.h b/servconf.h
index 3852b1bae..0cd78bc22 100644
--- a/servconf.h
+++ b/servconf.h
@@ -154,6 +154,8 @@ typedef struct {
 
         int     num_permitted_opens;
 
+        int     debian_banner;
+
         char   *chroot_directory;
 }       ServerOptions;
 
diff --git a/sshd.c b/sshd.c
index b83ecd9e5..bd671160d 100644
--- a/sshd.c
+++ b/sshd.c
@@ -425,7 +425,8 @@ sshd_exchange_identification(int sock_in, int sock_out)
                 minor = PROTOCOL_MINOR_1;
         }
         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor,
-            SSH_RELEASE, newline);
+            options.debian_banner ? SSH_RELEASE : SSH_RELEASE_MINIMUM,
+            newline);
         server_version_string = xstrdup(buf);
 
         /* Send our protocol version identification. */
diff --git a/sshd_config.5 b/sshd_config.5
index d30ad2ed1..0d2e0c3da 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -314,6 +314,11 @@ or
 .Dq no .
 The default is
 .Dq delayed .
+.It Cm DebianBanner
+Specifies whether the distribution-specified extra version suffix is
+included during initial protocol handshake.
+The default is
+.Dq yes .
 .It Cm DenyGroups
 This keyword can be followed by a list of group name patterns, separated
 by spaces.
diff --git a/version.h b/version.h
index 79af60194..2c7764677 100644
--- a/version.h
+++ b/version.h
@@ -3,8 +3,9 @@
 #define SSH_VERSION     "OpenSSH_5.2"
 
 #define SSH_PORTABLE    "p1"
+#define SSH_RELEASE_MINIMUM     SSH_VERSION SSH_PORTABLE
 #ifdef SSH_EXTRAVERSION
-#define SSH_RELEASE     SSH_VERSION SSH_PORTABLE " " SSH_EXTRAVERSION
+#define SSH_RELEASE     SSH_RELEASE_MINIMUM " " SSH_EXTRAVERSION
 #else
-#define SSH_RELEASE     SSH_VERSION SSH_PORTABLE
+#define SSH_RELEASE     SSH_RELEASE_MINIMUM
 #endif