From 7d20d00ea24ec0c3fffacc80ab271d0699d198c6 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: 2020-02-21 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 f638942d3..2abfbb95a 100644 --- a/kex.c +++ b/kex.c @@ -1226,7 +1226,7 @@ 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; @@ -1244,7 +1244,8 @@ 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 fe7141414..938dca03b 100644 --- a/kex.h +++ b/kex.h @@ -194,7 +194,7 @@ 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 bf3cd84a4..7bbc25c2e 100644 --- a/servconf.c +++ b/servconf.c @@ -194,6 +194,7 @@ 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. */ @@ -468,6 +469,8 @@ fill_default_server_options(ServerOptions *options) options->expose_userauth_info = 0; if (options->sk_provider == NULL) options->sk_provider = xstrdup("internal"); + if (options->debian_banner == -1) + options->debian_banner = 1; assemble_algorithms(options); @@ -556,6 +559,7 @@ typedef enum { sStreamLocalBindMask, sStreamLocalBindUnlink, sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding, sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider, + sDebianBanner, sDeprecated, sIgnore, sUnsupported } ServerOpCodes; @@ -719,6 +723,7 @@ static struct { { "rdomain", sRDomain, SSHCFG_ALL }, { "casignaturealgorithms", sCASignatureAlgorithms, SSHCFG_ALL }, { "securitykeyprovider", sSecurityKeyProvider, SSHCFG_GLOBAL }, + { "debianbanner", sDebianBanner, SSHCFG_GLOBAL }, { NULL, sBadOption, 0 } }; @@ -2382,6 +2387,10 @@ process_server_config_line_depth(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 3f47ea25e..3fa05fcac 100644 --- a/servconf.h +++ b/servconf.h @@ -221,6 +221,8 @@ typedef struct { int expose_userauth_info; u_int64_t timing_secret; char *sk_provider; + + int debian_banner; } ServerOptions; /* Information about the incoming connection as used by Match */ diff --git a/sshconnect.c b/sshconnect.c index b796d3c8a..9f2412e0d 100644 --- a/sshconnect.c +++ b/sshconnect.c @@ -1292,7 +1292,7 @@ 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 65916fc6d..da876a900 100644 --- a/sshd.c +++ b/sshd.c @@ -2187,7 +2187,8 @@ 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 ebd09f891..c926f584c 100644 --- a/sshd_config.5 +++ b/sshd_config.5 @@ -542,6 +542,11 @@ 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.