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From 30df3f03ff91b648414b35bdc697ce9127a9fe90 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: 2023-12-18
Patch-Name: debian-banner.patch
---
kex.c | 5 +++--
kex.h | 2 +-
servconf.c | 10 ++++++++++
servconf.h | 2 ++
sshconnect.c | 2 +-
sshd.c | 2 +-
sshd_config.5 | 5 +++++
7 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/kex.c b/kex.c
index 4e988e39b..30f2ce2b3 100644
--- a/kex.c
+++ b/kex.c
@@ -1545,7 +1545,7 @@ send_error(struct ssh *ssh, char *msg)
*/
int
kex_exchange_identification(struct ssh *ssh, int timeout_ms,
- const char *version_addendum)
+ int debian_banner, const char *version_addendum)
{
int remote_major, remote_minor, mismatch, oerrno = 0;
size_t len, n;
@@ -1563,7 +1563,8 @@ kex_exchange_identification(struct ssh *ssh, int timeout_ms,
if (version_addendum != NULL && *version_addendum == '\0')
version_addendum = NULL;
if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%s%s%s\r\n",
- PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_RELEASE,
+ PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
+ debian_banner ? SSH_RELEASE : SSH_RELEASE_MINIMUM,
version_addendum == NULL ? "" : " ",
version_addendum == NULL ? "" : version_addendum)) != 0) {
oerrno = errno;
diff --git a/kex.h b/kex.h
index 32da837f8..41888c0d8 100644
--- a/kex.h
+++ b/kex.h
@@ -208,7 +208,7 @@ void kex_proposal_populate_entries(struct ssh *, char *prop[PROPOSAL_MAX],
void kex_proposal_free_entries(char *prop[PROPOSAL_MAX]);
int kex_gss_names_valid(const char *);
-int kex_exchange_identification(struct ssh *, int, const char *);
+int kex_exchange_identification(struct ssh *, int, int, const char *);
struct kex *kex_new(void);
int kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
diff --git a/servconf.c b/servconf.c
index 193d73cca..12aa1f4ad 100644
--- a/servconf.c
+++ b/servconf.c
@@ -201,6 +201,7 @@ initialize_server_options(ServerOptions *options)
options->channel_timeouts = NULL;
options->num_channel_timeouts = 0;
options->unused_connection_timeout = -1;
+ options->debian_banner = -1;
}
/* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -459,6 +460,8 @@ fill_default_server_options(ServerOptions *options)
options->required_rsa_size = SSH_RSA_MINIMUM_MODULUS_SIZE;
if (options->unused_connection_timeout == -1)
options->unused_connection_timeout = 0;
+ if (options->debian_banner == -1)
+ options->debian_banner = 1;
assemble_algorithms(options);
@@ -544,6 +547,7 @@ typedef enum {
sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider,
sRequiredRSASize, sChannelTimeout, sUnusedConnectionTimeout,
+ sDebianBanner,
sDeprecated, sIgnore, sUnsupported
} ServerOpCodes;
@@ -717,6 +721,7 @@ static struct {
{ "requiredrsasize", sRequiredRSASize, SSHCFG_ALL },
{ "channeltimeout", sChannelTimeout, SSHCFG_ALL },
{ "unusedconnectiontimeout", sUnusedConnectionTimeout, SSHCFG_ALL },
+ { "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
{ NULL, sBadOption, 0 }
};
@@ -2637,6 +2642,10 @@ process_server_config_line_depth(ServerOptions *options, char *line,
}
goto parse_time;
+ case sDebianBanner:
+ intptr = &options->debian_banner;
+ goto parse_flag;
+
case sDeprecated:
case sIgnore:
case sUnsupported:
@@ -3185,6 +3194,7 @@ dump_config(ServerOptions *o)
dump_cfg_fmtint(sStreamLocalBindUnlink, o->fwd_opts.streamlocal_bind_unlink);
dump_cfg_fmtint(sFingerprintHash, o->fingerprint_hash);
dump_cfg_fmtint(sExposeAuthInfo, o->expose_userauth_info);
+ dump_cfg_fmtint(sDebianBanner, o->debian_banner);
/* string arguments */
dump_cfg_string(sPidFile, o->pid_file);
diff --git a/servconf.h b/servconf.h
index 2ce4ae0ad..e0c0af903 100644
--- a/servconf.h
+++ b/servconf.h
@@ -236,6 +236,8 @@ typedef struct {
u_int num_channel_timeouts;
int unused_connection_timeout;
+
+ int debian_banner;
} ServerOptions;
/* Information about the incoming connection as used by Match */
diff --git a/sshconnect.c b/sshconnect.c
index 23f79ed2b..da20ecd88 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1581,7 +1581,7 @@ ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
lowercase(host);
/* Exchange protocol version identification strings with the server. */
- if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0)
+ if ((r = kex_exchange_identification(ssh, timeout_ms, 1, NULL)) != 0)
sshpkt_fatal(ssh, r, "banner exchange");
/* Put the connection into non-blocking mode. */
diff --git a/sshd.c b/sshd.c
index 9c9f38e5b..8fab51ebb 100644
--- a/sshd.c
+++ b/sshd.c
@@ -2249,7 +2249,7 @@ main(int ac, char **av)
if (!debug_flag)
alarm(options.login_grace_time);
- if ((r = kex_exchange_identification(ssh, -1,
+ if ((r = kex_exchange_identification(ssh, -1, options.debian_banner,
options.version_addendum)) != 0)
sshpkt_fatal(ssh, r, "banner exchange");
diff --git a/sshd_config.5 b/sshd_config.5
index e06ef8abd..1a8febfa6 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -629,6 +629,11 @@ 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.
|
