[openssh-commits] [openssh] 05/08: upstream: Add a sshd_config "RefuseConnection" option
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commit 8d21713b669b8516ca6d43424a356fccc37212bb
Author: djm at openbsd.org <djm at openbsd.org>
AuthorDate: Sun Sep 15 01:09:40 2024 +0000
upstream: Add a sshd_config "RefuseConnection" option
If set, this will terminate the connection at the first authentication
request (this is the earliest we can evaluate sshd_config Match blocks)
ok markus@
OpenBSD-Commit-ID: 43cc2533984074c44d0d2f92eb93f661e7a0b09c
---
monitor.c | 12 +++++++++++-
servconf.c | 15 +++++++++++++--
servconf.h | 4 +++-
srclimit.h | 1 +
sshd_config.5 | 12 ++++++++++--
5 files changed, 38 insertions(+), 6 deletions(-)
diff --git a/monitor.c b/monitor.c
index 4e68c4f8..5966b4f9 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.243 2024/09/15 00:41:18 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.244 2024/09/15 01:09:40 djm Exp $ */
/*
* Copyright 2002 Niels Provos <provos at citi.umich.edu>
* Copyright 2002 Markus Friedl <markus at openbsd.org>
@@ -96,6 +96,7 @@
#include "match.h"
#include "ssherr.h"
#include "sk-api.h"
+#include "srclimit.h"
#ifdef GSSAPI
static Gssctxt *gsscontext = NULL;
@@ -797,6 +798,15 @@ mm_answer_pwnamallow(struct ssh *ssh, int sock, struct sshbuf *m)
ssh_packet_set_log_preamble(ssh, "%suser %s",
authctxt->valid ? "authenticating" : "invalid ", authctxt->user);
+ if (options.refuse_connection) {
+ logit("administratively prohibited connection for "
+ "%s%s from %.128s port %d",
+ authctxt->valid ? "" : "invalid user ",
+ authctxt->user, ssh_remote_ipaddr(ssh),
+ ssh_remote_port(ssh));
+ cleanup_exit(EXIT_CONFIG_REFUSED);
+ }
+
/* Send active options to unpriv */
mm_encode_server_options(m);
diff --git a/servconf.c b/servconf.c
index 7f1cb0df..e3f05aa7 100644
--- a/servconf.c
+++ b/servconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.c,v 1.414 2024/09/15 00:58:01 djm Exp $ */
+/* $OpenBSD: servconf.c,v 1.415 2024/09/15 01:09:40 djm Exp $ */
/*
* Copyright (c) 1995 Tatu Ylonen <ylo at cs.hut.fi>, Espoo, Finland
* All rights reserved
@@ -213,6 +213,7 @@ initialize_server_options(ServerOptions *options)
options->num_channel_timeouts = 0;
options->unused_connection_timeout = -1;
options->sshd_session_path = NULL;
+ options->refuse_connection = -1;
}
/* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -489,6 +490,8 @@ fill_default_server_options(ServerOptions *options)
options->unused_connection_timeout = 0;
if (options->sshd_session_path == NULL)
options->sshd_session_path = xstrdup(_PATH_SSHD_SESSION);
+ if (options->refuse_connection == -1)
+ options->refuse_connection = 0;
assemble_algorithms(options);
@@ -571,7 +574,7 @@ typedef enum {
sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider,
sRequiredRSASize, sChannelTimeout, sUnusedConnectionTimeout,
- sSshdSessionPath,
+ sSshdSessionPath, sRefuseConnection,
sDeprecated, sIgnore, sUnsupported
} ServerOpCodes;
@@ -739,6 +742,7 @@ static struct {
{ "channeltimeout", sChannelTimeout, SSHCFG_ALL },
{ "unusedconnectiontimeout", sUnusedConnectionTimeout, SSHCFG_ALL },
{ "sshdsessionpath", sSshdSessionPath, SSHCFG_GLOBAL },
+ { "refuseconnection", sRefuseConnection, SSHCFG_ALL },
{ NULL, sBadOption, 0 }
};
@@ -2655,6 +2659,11 @@ process_server_config_line_depth(ServerOptions *options, char *line,
charptr = &options->sshd_session_path;
goto parse_filename;
+ case sRefuseConnection:
+ intptr = &options->refuse_connection;
+ multistate_ptr = multistate_flag;
+ goto parse_multistate;
+
case sDeprecated:
case sIgnore:
case sUnsupported:
@@ -2870,6 +2879,7 @@ copy_set_server_options(ServerOptions *dst, ServerOptions *src, int preauth)
M_CP_INTOPT(log_level);
M_CP_INTOPT(required_rsa_size);
M_CP_INTOPT(unused_connection_timeout);
+ M_CP_INTOPT(refuse_connection);
/*
* The bind_mask is a mode_t that may be unsigned, so we can't use
@@ -3200,6 +3210,7 @@ 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(sRefuseConnection, o->refuse_connection);
/* string arguments */
dump_cfg_string(sPidFile, o->pid_file);
diff --git a/servconf.h b/servconf.h
index 22b158d1..f6d56704 100644
--- a/servconf.h
+++ b/servconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.h,v 1.165 2024/06/12 22:36:00 djm Exp $ */
+/* $OpenBSD: servconf.h,v 1.166 2024/09/15 01:09:40 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo at cs.hut.fi>
@@ -248,6 +248,8 @@ typedef struct {
int unused_connection_timeout;
char *sshd_session_path;
+
+ int refuse_connection;
} ServerOptions;
/* Information about the incoming connection as used by Match */
diff --git a/srclimit.h b/srclimit.h
index 74a6f2b8..13164515 100644
--- a/srclimit.h
+++ b/srclimit.h
@@ -32,6 +32,7 @@ void srclimit_done(int);
#define EXIT_LOGIN_GRACE 3 /* login grace period exceeded */
#define EXIT_CHILD_CRASH 4 /* preauth child crashed */
#define EXIT_AUTH_ATTEMPTED 5 /* at least one auth attempt made */
+#define EXIT_CONFIG_REFUSED 6 /* sshd_config RefuseConnection */
void srclimit_penalise(struct xaddr *, int);
int srclimit_penalty_check_allow(int, const char **);
diff --git a/sshd_config.5 b/sshd_config.5
index 87f0945c..56ed2bf1 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -33,8 +33,8 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.\" $OpenBSD: sshd_config.5,v 1.370 2024/09/09 14:41:21 naddy Exp $
-.Dd $Mdocdate: September 9 2024 $
+.\" $OpenBSD: sshd_config.5,v 1.371 2024/09/15 01:09:40 djm Exp $
+.Dd $Mdocdate: September 15 2024 $
.Dt SSHD_CONFIG 5
.Os
.Sh NAME
@@ -1325,6 +1325,7 @@ Available keywords are
.Cm PubkeyAuthentication ,
.Cm PubkeyAuthOptions ,
.Cm RekeyLimit ,
+.Cm RefuseConnection ,
.Cm RevokedKeys ,
.Cm RDomain ,
.Cm SetEnv ,
@@ -1761,6 +1762,13 @@ options have any effect for other, non-FIDO, public key types.
Specifies whether public key authentication is allowed.
The default is
.Cm yes .
+.It Cm RefuseConnection
+Indicates that
+.Xr sshd 8
+should unconditionally terminate the connection.
+This option is only really useful in a
+.Cm Match
+block.
.It Cm RekeyLimit
Specifies the maximum amount of data that may be transmitted or received
before the session key is renegotiated, optionally followed by a maximum
--
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