From 9fcad888f4dbf0ecc0c7e87b6ef0f8d88d7ac3ec 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: 2013-09-14

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 90de888..37fd2de 100644
--- a/servconf.c
+++ b/servconf.c
@@ -156,6 +156,7 @@ initialize_server_options(ServerOptions *options)
 	options->ip_qos_interactive = -1;
 	options->ip_qos_bulk = -1;
 	options->version_addendum = NULL;
+	options->debian_banner = -1;
 }
 
 void
@@ -309,6 +310,8 @@ fill_default_server_options(ServerOptions *options)
 		options->ip_qos_bulk = IPTOS_THROUGHPUT;
 	if (options->version_addendum == NULL)
 		options->version_addendum = xstrdup("");
+	if (options->debian_banner == -1)
+		options->debian_banner = 1;
 	/* Turn privilege separation on by default */
 	if (use_privsep == -1)
 		use_privsep = PRIVSEP_NOSANDBOX;
@@ -359,6 +362,7 @@ typedef enum {
 	sKexAlgorithms, sIPQoS, sVersionAddendum,
 	sAuthorizedKeysCommand, sAuthorizedKeysCommandUser,
 	sAuthenticationMethods, sHostKeyAgent,
+	sDebianBanner,
 	sDeprecated, sUnsupported
 } ServerOpCodes;
 
@@ -496,6 +500,7 @@ static struct {
 	{ "authorizedkeyscommanduser", sAuthorizedKeysCommandUser, SSHCFG_ALL },
 	{ "versionaddendum", sVersionAddendum, SSHCFG_GLOBAL },
 	{ "authenticationmethods", sAuthenticationMethods, SSHCFG_ALL },
+	{ "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
 	{ NULL, sBadOption, 0 }
 };
 
@@ -1654,6 +1659,10 @@ process_server_config_line(ServerOptions *options, char *line,
 		}
 		return 0;
 
+	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 c922eb5..dcd1c2a 100644
--- a/servconf.h
+++ b/servconf.h
@@ -186,6 +186,8 @@ 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 af9b8f1..665c0b9 100644
--- a/sshd.c
+++ b/sshd.c
@@ -440,7 +440,8 @@ 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 2164d58..8f078f6 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -413,6 +413,11 @@ 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.