From bb18ca3880d333834c89f535032cdf12bc362fdf 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 ed3a88d..a778f44 100644
--- a/servconf.c
+++ b/servconf.c
@@ -171,6 +171,7 @@ initialize_server_options(ServerOptions *options)
 	options->ip_qos_bulk = -1;
 	options->version_addendum = NULL;
 	options->fingerprint_hash = -1;
+	options->debian_banner = -1;
 }
 
 /* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -347,6 +348,8 @@ fill_default_server_options(ServerOptions *options)
 		options->fwd_opts.streamlocal_bind_unlink = 0;
 	if (options->fingerprint_hash == -1)
 		options->fingerprint_hash = SSH_FP_HASH_DEFAULT;
+	if (options->debian_banner == -1)
+		options->debian_banner = 1;
 
 	if (kex_assemble_names(KEX_SERVER_ENCRYPT, &options->ciphers) != 0 ||
 	    kex_assemble_names(KEX_SERVER_MAC, &options->macs) != 0 ||
@@ -430,6 +433,7 @@ typedef enum {
 	sAuthenticationMethods, sHostKeyAgent, sPermitUserRC,
 	sStreamLocalBindMask, sStreamLocalBindUnlink,
 	sAllowStreamLocalForwarding, sFingerprintHash,
+	sDebianBanner,
 	sDeprecated, sUnsupported
 } ServerOpCodes;
 
@@ -577,6 +581,7 @@ static struct {
 	{ "streamlocalbindunlink", sStreamLocalBindUnlink, SSHCFG_ALL },
 	{ "allowstreamlocalforwarding", sAllowStreamLocalForwarding, SSHCFG_ALL },
 	{ "fingerprinthash", sFingerprintHash, SSHCFG_GLOBAL },
+	{ "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
 	{ NULL, sBadOption, 0 }
 };
 
@@ -1867,6 +1872,10 @@ process_server_config_line(ServerOptions *options, char *line,
 			options->fingerprint_hash = value;
 		break;
 
+	case sDebianBanner:
+		intptr = &options->debian_banner;
+		goto parse_int;
+
 	case sDeprecated:
 		logit("%s line %d: Deprecated option %s",
 		    filename, linenum, arg);
diff --git a/servconf.h b/servconf.h
index 778ba17..161fa37 100644
--- a/servconf.h
+++ b/servconf.h
@@ -197,6 +197,8 @@ 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 e3ac37b..d9f5199 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 154e87e..641e1fa 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -533,6 +533,11 @@ 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.