[openssh-commits] [openssh] 05/05: upstream: Add RequiredRSASize for sshd(8); RSA keys that fall
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commit 1875042c52a3b950ae5963c9ca3774a4cc7f0380
Author: djm at openbsd.org <djm at openbsd.org>
Date: Sat Sep 17 10:34:29 2022 +0000
upstream: Add RequiredRSASize for sshd(8); RSA keys that fall
beneath this limit will be ignored for user and host-based authentication.
Feedback deraadt@ ok markus@
OpenBSD-Commit-ID: 187931dfc19d51873df5930a04f2d972adf1f7f1
---
auth2-hostbased.c | 7 ++++++-
auth2-pubkey.c | 7 ++++++-
servconf.c | 13 ++++++++++++-
servconf.h | 3 ++-
sshd.c | 9 ++++++++-
sshd_config.5 | 14 ++++++++++++--
6 files changed, 46 insertions(+), 7 deletions(-)
diff --git a/auth2-hostbased.c b/auth2-hostbased.c
index 36b9d2f5..6b517db4 100644
--- a/auth2-hostbased.c
+++ b/auth2-hostbased.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-hostbased.c,v 1.49 2022/01/06 22:01:14 djm Exp $ */
+/* $OpenBSD: auth2-hostbased.c,v 1.50 2022/09/17 10:34:29 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
@@ -119,6 +119,11 @@ userauth_hostbased(struct ssh *ssh, const char *method)
"(null)" : key->cert->signature_type);
goto done;
}
+ if ((r = sshkey_check_rsa_length(key,
+ options.required_rsa_size)) != 0) {
+ logit_r(r, "refusing %s key", sshkey_type(key));
+ goto done;
+ }
if (!authctxt->valid || authctxt->user == NULL) {
debug2_f("disabled because of invalid user");
diff --git a/auth2-pubkey.c b/auth2-pubkey.c
index 962fd342..5d59febc 100644
--- a/auth2-pubkey.c
+++ b/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.116 2022/06/15 16:08:25 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.117 2022/09/17 10:34:29 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@@ -175,6 +175,11 @@ userauth_pubkey(struct ssh *ssh, const char *method)
"(null)" : key->cert->signature_type);
goto done;
}
+ if ((r = sshkey_check_rsa_length(key,
+ options.required_rsa_size)) != 0) {
+ logit_r(r, "refusing %s key", sshkey_type(key));
+ goto done;
+ }
key_s = format_key(key);
if (sshkey_is_cert(key))
ca_s = format_key(key->cert->signature_key);
diff --git a/servconf.c b/servconf.c
index 29df0463..423772b1 100644
--- a/servconf.c
+++ b/servconf.c
@@ -1,5 +1,5 @@
-/* $OpenBSD: servconf.c,v 1.385 2022/06/03 04:30:47 djm Exp $ */
+/* $OpenBSD: servconf.c,v 1.386 2022/09/17 10:34:29 djm Exp $ */
/*
* Copyright (c) 1995 Tatu Ylonen <ylo at cs.hut.fi>, Espoo, Finland
* All rights reserved
@@ -195,6 +195,7 @@ initialize_server_options(ServerOptions *options)
options->fingerprint_hash = -1;
options->disable_forwarding = -1;
options->expose_userauth_info = -1;
+ options->required_rsa_size = -1;
}
/* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -441,6 +442,8 @@ fill_default_server_options(ServerOptions *options)
options->expose_userauth_info = 0;
if (options->sk_provider == NULL)
options->sk_provider = xstrdup("internal");
+ if (options->required_rsa_size == -1)
+ options->required_rsa_size = SSH_RSA_MINIMUM_MODULUS_SIZE;
assemble_algorithms(options);
@@ -517,6 +520,7 @@ typedef enum {
sStreamLocalBindMask, sStreamLocalBindUnlink,
sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider,
+ sRequiredRSASize,
sDeprecated, sIgnore, sUnsupported
} ServerOpCodes;
@@ -676,6 +680,7 @@ static struct {
{ "rdomain", sRDomain, SSHCFG_ALL },
{ "casignaturealgorithms", sCASignatureAlgorithms, SSHCFG_ALL },
{ "securitykeyprovider", sSecurityKeyProvider, SSHCFG_GLOBAL },
+ { "requiredrsasize", sRequiredRSASize, SSHCFG_ALL },
{ NULL, sBadOption, 0 }
};
@@ -2438,6 +2443,10 @@ process_server_config_line_depth(ServerOptions *options, char *line,
*charptr = xstrdup(arg);
break;
+ case sRequiredRSASize:
+ intptr = &options->required_rsa_size;
+ goto parse_int;
+
case sDeprecated:
case sIgnore:
case sUnsupported:
@@ -2610,6 +2619,7 @@ copy_set_server_options(ServerOptions *dst, ServerOptions *src, int preauth)
M_CP_INTOPT(rekey_limit);
M_CP_INTOPT(rekey_interval);
M_CP_INTOPT(log_level);
+ M_CP_INTOPT(required_rsa_size);
/*
* The bind_mask is a mode_t that may be unsigned, so we can't use
@@ -2874,6 +2884,7 @@ dump_config(ServerOptions *o)
dump_cfg_int(sMaxSessions, o->max_sessions);
dump_cfg_int(sClientAliveInterval, o->client_alive_interval);
dump_cfg_int(sClientAliveCountMax, o->client_alive_count_max);
+ dump_cfg_int(sRequiredRSASize, o->required_rsa_size);
dump_cfg_oct(sStreamLocalBindMask, o->fwd_opts.streamlocal_bind_mask);
/* formatted integer arguments */
diff --git a/servconf.h b/servconf.h
index 8a04463e..9346155c 100644
--- a/servconf.h
+++ b/servconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.h,v 1.156 2022/03/18 04:04:11 djm Exp $ */
+/* $OpenBSD: servconf.h,v 1.157 2022/09/17 10:34:29 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo at cs.hut.fi>
@@ -229,6 +229,7 @@ typedef struct {
int expose_userauth_info;
u_int64_t timing_secret;
char *sk_provider;
+ int required_rsa_size; /* minimum size of RSA keys */
} ServerOptions;
/* Information about the incoming connection as used by Match */
diff --git a/sshd.c b/sshd.c
index 17eee9d8..395ef493 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.590 2022/07/01 05:08:23 dtucker Exp $ */
+/* $OpenBSD: sshd.c,v 1.591 2022/09/17 10:34:29 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo at cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo at cs.hut.fi>, Espoo, Finland
@@ -1870,6 +1870,13 @@ main(int ac, char **av)
fatal_r(r, "Could not demote key: \"%s\"",
options.host_key_files[i]);
}
+ if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey,
+ options.required_rsa_size)) != 0) {
+ error_fr(r, "Host key %s", options.host_key_files[i]);
+ sshkey_free(pubkey);
+ sshkey_free(key);
+ continue;
+ }
sensitive_data.host_keys[i] = key;
sensitive_data.host_pubkeys[i] = pubkey;
diff --git a/sshd_config.5 b/sshd_config.5
index 867a747d..f5a06637 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 1.342 2022/06/24 04:27:14 djm Exp $
-.Dd $Mdocdate: June 24 2022 $
+.\" $OpenBSD: sshd_config.5,v 1.343 2022/09/17 10:34:29 djm Exp $
+.Dd $Mdocdate: September 17 2022 $
.Dt SSHD_CONFIG 5
.Os
.Sh NAME
@@ -1596,6 +1596,16 @@ is
.Cm default none ,
which means that rekeying is performed after the cipher's default amount
of data has been sent or received and no time based rekeying is done.
+.It Cm RequiredRSASize
+Specifies the minimum RSA key size (in bits) that
+.Xr sshd 8
+will accept.
+User and host-based authentication keys smaller than this limit will be
+refused.
+The default is
+.Cm 1024
+bits.
+Note that this limit may only be raised from the default.
.It Cm RevokedKeys
Specifies revoked public keys file, or
.Cm none
--
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