From 114c8a8fb488cbe39507edb75c51198a4b9e8b24 Mon Sep 17 00:00:00 2001
From: Kees Cook <kees@debian.org>
Date: Sun, 9 Feb 2014 16:10:06 +0000
Subject: Add DebianBanner server configuration option

Setting this to "no" causes sshd to omit the Debian revision from its
initial protocol handshake, for those scared by package-versioning.patch.

Bug-Debian: http://bugs.debian.org/562048
Forwarded: not-needed
Last-Update: 2014-10-07

Patch-Name: debian-banner.patch
---
 servconf.c    | 9 +++++++++
 servconf.h    | 2 ++
 sshd.c        | 3 ++-
 sshd_config.5 | 5 +++++
 4 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/servconf.c b/servconf.c
index a252487..6c7741a 100644
--- a/servconf.c
+++ b/servconf.c
@@ -160,6 +160,7 @@ initialize_server_options(ServerOptions *options)
 	options->ip_qos_interactive = -1;
 	options->ip_qos_bulk = -1;
 	options->version_addendum = NULL;
+	options->debian_banner = -1;
 }
 
 void
@@ -321,6 +322,8 @@ fill_default_server_options(ServerOptions *options)
 		options->fwd_opts.streamlocal_bind_mask = 0177;
 	if (options->fwd_opts.streamlocal_bind_unlink == -1)
 		options->fwd_opts.streamlocal_bind_unlink = 0;
+	if (options->debian_banner == -1)
+		options->debian_banner = 1;
 	/* Turn privilege separation on by default */
 	if (use_privsep == -1)
 		use_privsep = PRIVSEP_NOSANDBOX;
@@ -373,6 +376,7 @@ typedef enum {
 	sAuthenticationMethods, sHostKeyAgent, sPermitUserRC,
 	sStreamLocalBindMask, sStreamLocalBindUnlink,
 	sAllowStreamLocalForwarding,
+	sDebianBanner,
 	sDeprecated, sUnsupported
 } ServerOpCodes;
 
@@ -514,6 +518,7 @@ static struct {
 	{ "streamlocalbindmask", sStreamLocalBindMask, SSHCFG_ALL },
 	{ "streamlocalbindunlink", sStreamLocalBindUnlink, SSHCFG_ALL },
 	{ "allowstreamlocalforwarding", sAllowStreamLocalForwarding, SSHCFG_ALL },
+	{ "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
 	{ NULL, sBadOption, 0 }
 };
 
@@ -1697,6 +1702,10 @@ process_server_config_line(ServerOptions *options, char *line,
 		intptr = &options->fwd_opts.streamlocal_bind_unlink;
 		goto parse_flag;
 
+	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 f8265a8..fa48804 100644
--- a/servconf.h
+++ b/servconf.h
@@ -188,6 +188,8 @@ typedef struct {
 
 	u_int	num_auth_methods;
 	char   *auth_methods[MAX_AUTH_METHODS];
+
+	int	debian_banner;
 }       ServerOptions;
 
 /* Information about the incoming connection as used by Match */
diff --git a/sshd.c b/sshd.c
index 1710e71..87331c1 100644
--- a/sshd.c
+++ b/sshd.c
@@ -443,7 +443,8 @@ sshd_exchange_identification(int sock_in, int sock_out)
 	}
 
 	xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s%s",
-	    major, minor, SSH_RELEASE,
+	    major, minor,
+	    options.debian_banner ? SSH_RELEASE : SSH_RELEASE_MINIMUM,
 	    *options.version_addendum == '\0' ? "" : " ",
 	    options.version_addendum, newline);
 
diff --git a/sshd_config.5 b/sshd_config.5
index 2843048..58997d3 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -447,6 +447,11 @@ 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.