From 2a1aeb898e4214f98acc210c992d33334e6710dd 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: 2015-11-29

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 49d3bdc8..1cee3d6c 100644
--- a/servconf.c
+++ b/servconf.c
@@ -166,6 +166,7 @@ initialize_server_options(ServerOptions *options)
 	options->version_addendum = NULL;
 	options->fingerprint_hash = -1;
 	options->disable_forwarding = -1;
+	options->debian_banner = -1;
 }
 
 /* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -339,6 +340,8 @@ fill_default_server_options(ServerOptions *options)
 		options->fingerprint_hash = SSH_FP_HASH_DEFAULT;
 	if (options->disable_forwarding == -1)
 		options->disable_forwarding = 0;
+	if (options->debian_banner == -1)
+		options->debian_banner = 1;
 
 	assemble_algorithms(options);
 
@@ -425,6 +428,7 @@ typedef enum {
 	sAuthenticationMethods, sHostKeyAgent, sPermitUserRC,
 	sStreamLocalBindMask, sStreamLocalBindUnlink,
 	sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
+	sDebianBanner,
 	sDeprecated, sIgnore, sUnsupported
 } ServerOpCodes;
 
@@ -577,6 +581,7 @@ static struct {
 	{ "allowstreamlocalforwarding", sAllowStreamLocalForwarding, SSHCFG_ALL },
 	{ "fingerprinthash", sFingerprintHash, SSHCFG_GLOBAL },
 	{ "disableforwarding", sDisableForwarding, SSHCFG_ALL },
+	{ "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
 	{ NULL, sBadOption, 0 }
 };
 
@@ -1860,6 +1865,10 @@ process_server_config_line(ServerOptions *options, char *line,
 			options->fingerprint_hash = value;
 		break;
 
+	case sDebianBanner:
+		intptr = &options->debian_banner;
+		goto parse_int;
+
 	case sDeprecated:
 	case sIgnore:
 	case sUnsupported:
diff --git a/servconf.h b/servconf.h
index 90dfa4c2..913a21b3 100644
--- a/servconf.h
+++ b/servconf.h
@@ -191,6 +191,8 @@ typedef struct {
 	char   *auth_methods[MAX_AUTH_METHODS];
 
 	int	fingerprint_hash;
+
+	int	debian_banner;
 }       ServerOptions;
 
 /* Information about the incoming connection as used by Match */
diff --git a/sshd.c b/sshd.c
index 49f3a2e5..eebf1984 100644
--- a/sshd.c
+++ b/sshd.c
@@ -378,7 +378,8 @@ sshd_exchange_identification(struct ssh *ssh, int sock_in, int sock_out)
 	char remote_version[256];	/* Must be at least as big as buf. */
 
 	xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s%s",
-	    PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_RELEASE,
+	    PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
+	    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 283ba889..4ea0a9c3 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -526,6 +526,11 @@ or
 .Cm no .
 The default is
 .Cm yes .
+.It Cm DebianBanner
+Specifies whether the distribution-specified extra version suffix is
+included during initial protocol handshake.
+The default is
+.Cm yes .
 .It Cm DenyGroups
 This keyword can be followed by a list of group name patterns, separated
 by spaces.