From 0a938d856d024bfff79fac63e65df382ffa444a4 Mon Sep 17 00:00:00 2001 From: Kees Cook 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: 2019-06-05 Patch-Name: debian-banner.patch --- kex.c | 5 +++-- kex.h | 2 +- servconf.c | 9 +++++++++ servconf.h | 2 ++ sshconnect.c | 2 +- sshd.c | 3 ++- sshd_config.5 | 5 +++++ 7 files changed, 23 insertions(+), 5 deletions(-) diff --git a/kex.c b/kex.c index be354206d..bbb7a2340 100644 --- a/kex.c +++ b/kex.c @@ -1168,7 +1168,7 @@ 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; size_t len, i, n; @@ -1186,7 +1186,8 @@ 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-%.100s%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) { error("%s: sshbuf_putf: %s", __func__, ssh_err(r)); diff --git a/kex.h b/kex.h index 2d5f1d4ed..39f67bbc1 100644 --- a/kex.h +++ b/kex.h @@ -195,7 +195,7 @@ char *kex_names_cat(const char *, const char *); int kex_assemble_names(char **, const char *, const char *); 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 c01e0690e..8d2bced52 100644 --- a/servconf.c +++ b/servconf.c @@ -184,6 +184,7 @@ initialize_server_options(ServerOptions *options) options->fingerprint_hash = -1; options->disable_forwarding = -1; options->expose_userauth_info = -1; + options->debian_banner = -1; } /* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */ @@ -437,6 +438,8 @@ fill_default_server_options(ServerOptions *options) options->disable_forwarding = 0; if (options->expose_userauth_info == -1) options->expose_userauth_info = 0; + if (options->debian_banner == -1) + options->debian_banner = 1; assemble_algorithms(options); @@ -523,6 +526,7 @@ typedef enum { sStreamLocalBindMask, sStreamLocalBindUnlink, sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding, sExposeAuthInfo, sRDomain, + sDebianBanner, sDeprecated, sIgnore, sUnsupported } ServerOpCodes; @@ -682,6 +686,7 @@ static struct { { "exposeauthinfo", sExposeAuthInfo, SSHCFG_ALL }, { "rdomain", sRDomain, SSHCFG_ALL }, { "casignaturealgorithms", sCASignatureAlgorithms, SSHCFG_ALL }, + { "debianbanner", sDebianBanner, SSHCFG_GLOBAL }, { NULL, sBadOption, 0 } }; @@ -2211,6 +2216,10 @@ process_server_config_line(ServerOptions *options, char *line, *charptr = xstrdup(arg); break; + case sDebianBanner: + intptr = &options->debian_banner; + goto parse_flag; + case sDeprecated: case sIgnore: case sUnsupported: diff --git a/servconf.h b/servconf.h index a476d5220..986093ffa 100644 --- a/servconf.h +++ b/servconf.h @@ -214,6 +214,8 @@ typedef struct { int fingerprint_hash; int expose_userauth_info; u_int64_t timing_secret; + + int debian_banner; } ServerOptions; /* Information about the incoming connection as used by Match */ diff --git a/sshconnect.c b/sshconnect.c index 0b6f6af4b..1183ffe0e 100644 --- a/sshconnect.c +++ b/sshconnect.c @@ -1287,7 +1287,7 @@ ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost, lowercase(host); /* Exchange protocol version identification strings with the server. */ - if (kex_exchange_identification(ssh, timeout_ms, NULL) != 0) + if (kex_exchange_identification(ssh, timeout_ms, 1, NULL) != 0) cleanup_exit(255); /* error already logged */ /* Put the connection into non-blocking mode. */ diff --git a/sshd.c b/sshd.c index e3e96426e..1e7ece588 100644 --- a/sshd.c +++ b/sshd.c @@ -2160,7 +2160,8 @@ main(int ac, char **av) if (!debug_flag) alarm(options.login_grace_time); - if (kex_exchange_identification(ssh, -1, options.version_addendum) != 0) + if (kex_exchange_identification(ssh, -1, options.debian_banner, + options.version_addendum) != 0) cleanup_exit(255); /* error already logged */ ssh_packet_set_nonblocking(ssh); diff --git a/sshd_config.5 b/sshd_config.5 index 2ef671d1b..addea54a0 100644 --- a/sshd_config.5 +++ b/sshd_config.5 @@ -543,6 +543,11 @@ 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.