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upstream: add a RequiredRSASize for checking RSA key length in
ssh(1). User authentication keys that fall beneath this limit will be ignored. If a host presents a host key beneath this limit then the connection will be terminated (unfortunately there are no fallbacks in the protocol for host authentication). feedback deraadt, Dmitry Belyavskiy; ok markus@ OpenBSD-Commit-ID: 430e339b2a79fa9ecc63f2837b06fdd88a7da13a
This commit is contained in:
djm@openbsd.org
Damien Miller
parent
07d8771bac
commit
54b333d12e
13
readconf.c
13
readconf.c
@ -1,4 +1,4 @@
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/* $OpenBSD: readconf.c,v 1.368 2022/06/03 04:30:47 djm Exp $ */
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/* $OpenBSD: readconf.c,v 1.369 2022/09/17 10:33:18 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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@ -174,7 +174,7 @@ typedef enum {
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oStreamLocalBindMask, oStreamLocalBindUnlink, oRevokedHostKeys,
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oFingerprintHash, oUpdateHostkeys, oHostbasedAcceptedAlgorithms,
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oPubkeyAcceptedAlgorithms, oCASignatureAlgorithms, oProxyJump,
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oSecurityKeyProvider, oKnownHostsCommand,
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oSecurityKeyProvider, oKnownHostsCommand, oRequiredRSASize,
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oIgnore, oIgnoredUnknownOption, oDeprecated, oUnsupported
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} OpCodes;
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@ -320,6 +320,7 @@ static struct {
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{ "proxyjump", oProxyJump },
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{ "securitykeyprovider", oSecurityKeyProvider },
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{ "knownhostscommand", oKnownHostsCommand },
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{ "requiredrsasize", oRequiredRSASize },
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{ NULL, oBadOption }
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};
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@ -2176,6 +2177,10 @@ parse_pubkey_algos:
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*charptr = xstrdup(arg);
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break;
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case oRequiredRSASize:
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intptr = &options->required_rsa_size;
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goto parse_int;
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case oDeprecated:
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debug("%s line %d: Deprecated option \"%s\"",
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filename, linenum, keyword);
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@ -2423,6 +2428,7 @@ initialize_options(Options * options)
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options->hostbased_accepted_algos = NULL;
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options->pubkey_accepted_algos = NULL;
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options->known_hosts_command = NULL;
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options->required_rsa_size = -1;
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}
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/*
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@ -2619,6 +2625,8 @@ fill_default_options(Options * options)
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if (options->sk_provider == NULL)
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options->sk_provider = xstrdup("$SSH_SK_PROVIDER");
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#endif
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if (options->required_rsa_size == -1)
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options->required_rsa_size = SSH_RSA_MINIMUM_MODULUS_SIZE;
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/* Expand KEX name lists */
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all_cipher = cipher_alg_list(',', 0);
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@ -3308,6 +3316,7 @@ dump_client_config(Options *o, const char *host)
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dump_cfg_int(oNumberOfPasswordPrompts, o->number_of_password_prompts);
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dump_cfg_int(oServerAliveCountMax, o->server_alive_count_max);
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dump_cfg_int(oServerAliveInterval, o->server_alive_interval);
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dump_cfg_int(oRequiredRSASize, o->required_rsa_size);
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/* String options */
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dump_cfg_string(oBindAddress, o->bind_address);
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@ -1,4 +1,4 @@
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/* $OpenBSD: readconf.h,v 1.147 2022/06/03 04:30:47 djm Exp $ */
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/* $OpenBSD: readconf.h,v 1.148 2022/09/17 10:33:18 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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@ -176,6 +176,8 @@ typedef struct {
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char *known_hosts_command;
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int required_rsa_size; /* minimum size of RSA keys */
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char *ignored_unknown; /* Pattern list of unknown tokens to ignore */
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} Options;
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5
ssh.1
5
ssh.1
@ -33,8 +33,8 @@
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $OpenBSD: ssh.1,v 1.431 2022/05/28 05:57:56 jmc Exp $
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.Dd $Mdocdate: May 28 2022 $
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.\" $OpenBSD: ssh.1,v 1.432 2022/09/17 10:33:18 djm Exp $
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.Dd $Mdocdate: September 17 2022 $
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.Dt SSH 1
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.Os
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.Sh NAME
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@ -571,6 +571,7 @@ For full details of the options listed below, and their possible values, see
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.It RemoteCommand
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.It RemoteForward
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.It RequestTTY
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.It RequiredRSASize
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.It SendEnv
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.It ServerAliveInterval
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.It ServerAliveCountMax
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27
ssh.c
27
ssh.c
@ -1,4 +1,4 @@
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/* $OpenBSD: ssh.c,v 1.575 2022/07/01 00:36:30 djm Exp $ */
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/* $OpenBSD: ssh.c,v 1.576 2022/09/17 10:33:18 djm Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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@ -516,14 +516,22 @@ resolve_canonicalize(char **hostp, int port)
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}
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/*
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* Check the result of hostkey loading, ignoring some errors and
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* fatal()ing for others.
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* Check the result of hostkey loading, ignoring some errors and either
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* discarding the key or fatal()ing for others.
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*/
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static void
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check_load(int r, const char *path, const char *message)
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check_load(int r, struct sshkey **k, const char *path, const char *message)
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{
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switch (r) {
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case 0:
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/* Check RSA keys size and discard if undersized */
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if (k != NULL && *k != NULL &&
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(r = sshkey_check_rsa_length(*k,
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options.required_rsa_size)) != 0) {
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error_r(r, "load %s \"%s\"", message, path);
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free(*k);
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*k = NULL;
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}
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break;
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case SSH_ERR_INTERNAL_ERROR:
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case SSH_ERR_ALLOC_FAIL:
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@ -1578,7 +1586,7 @@ main(int ac, char **av)
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if ((o) >= sensitive_data.nkeys) \
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fatal_f("pubkey out of array bounds"); \
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check_load(sshkey_load_public(p, &(sensitive_data.keys[o]), NULL), \
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p, "pubkey"); \
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&(sensitive_data.keys[o]), p, "pubkey"); \
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if (sensitive_data.keys[o] != NULL) \
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debug2("hostbased key %d: %s key from \"%s\"", o, \
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sshkey_ssh_name(sensitive_data.keys[o]), p); \
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@ -1586,7 +1594,8 @@ main(int ac, char **av)
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#define L_CERT(p,o) do { \
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if ((o) >= sensitive_data.nkeys) \
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fatal_f("cert out of array bounds"); \
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check_load(sshkey_load_cert(p, &(sensitive_data.keys[o])), p, "cert"); \
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check_load(sshkey_load_cert(p, &(sensitive_data.keys[o])), \
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&(sensitive_data.keys[o]), p, "cert"); \
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if (sensitive_data.keys[o] != NULL) \
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debug2("hostbased key %d: %s cert from \"%s\"", o, \
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sshkey_ssh_name(sensitive_data.keys[o]), p); \
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@ -2265,7 +2274,7 @@ load_public_identity_files(const struct ssh_conn_info *cinfo)
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filename = default_client_percent_dollar_expand(cp, cinfo);
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free(cp);
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check_load(sshkey_load_public(filename, &public, NULL),
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filename, "pubkey");
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&public, filename, "pubkey");
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debug("identity file %s type %d", filename,
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public ? public->type : -1);
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free(options.identity_files[i]);
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@ -2284,7 +2293,7 @@ load_public_identity_files(const struct ssh_conn_info *cinfo)
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continue;
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xasprintf(&cp, "%s-cert", filename);
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check_load(sshkey_load_public(cp, &public, NULL),
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filename, "pubkey");
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&public, filename, "pubkey");
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debug("identity file %s type %d", cp,
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public ? public->type : -1);
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if (public == NULL) {
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@ -2315,7 +2324,7 @@ load_public_identity_files(const struct ssh_conn_info *cinfo)
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free(cp);
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check_load(sshkey_load_public(filename, &public, NULL),
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filename, "certificate");
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&public, filename, "certificate");
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debug("certificate file %s type %d", filename,
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public ? public->type : -1);
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free(options.certificate_files[i]);
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15
ssh_config.5
15
ssh_config.5
@ -33,8 +33,8 @@
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $OpenBSD: ssh_config.5,v 1.373 2022/06/24 04:27:14 djm Exp $
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.Dd $Mdocdate: June 24 2022 $
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.\" $OpenBSD: ssh_config.5,v 1.374 2022/09/17 10:33:18 djm Exp $
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.Dd $Mdocdate: September 17 2022 $
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.Dt SSH_CONFIG 5
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.Os
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.Sh NAME
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@ -1634,6 +1634,17 @@ and
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.Fl T
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flags for
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.Xr ssh 1 .
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.It Cm RequiredRSASize
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Specifies the minimum RSA key size (in bits) that
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.Xr ssh 1
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will accept.
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User authentication keys smaller than this limit will be ignored.
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Servers that present host keys smaller than this limit will cause the
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connection to be terminated.
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The default is
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.Cm 1024
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bits.
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Note that this limit may only be raised from the default.
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.It Cm RevokedHostKeys
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Specifies revoked host public keys.
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Keys listed in this file will be refused for host authentication.
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@ -1,4 +1,4 @@
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/* $OpenBSD: sshconnect2.c,v 1.360 2022/08/19 06:07:47 djm Exp $ */
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/* $OpenBSD: sshconnect2.c,v 1.361 2022/09/17 10:33:18 djm Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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* Copyright (c) 2008 Damien Miller. All rights reserved.
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@ -96,6 +96,11 @@ static const struct ssh_conn_info *xxx_conn_info;
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static int
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verify_host_key_callback(struct sshkey *hostkey, struct ssh *ssh)
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{
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int r;
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if ((r = sshkey_check_rsa_length(hostkey,
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options.required_rsa_size)) != 0)
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fatal_r(r, "Bad server host key");
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if (verify_host_key(xxx_host, xxx_hostaddr, hostkey,
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xxx_conn_info) == -1)
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fatal("Host key verification failed.");
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@ -1606,6 +1611,13 @@ load_identity_file(Identity *id)
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private = NULL;
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quit = 1;
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}
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if (!quit && (r = sshkey_check_rsa_length(private,
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options.required_rsa_size)) != 0) {
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debug_fr(r, "Skipping key %s", id->filename);
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sshkey_free(private);
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private = NULL;
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quit = 1;
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}
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if (!quit && private != NULL && id->agent_fd == -1 &&
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!(id->key && id->isprivate))
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maybe_add_key_to_agent(id->filename, private, comment,
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@ -1752,6 +1764,12 @@ pubkey_prepare(struct ssh *ssh, Authctxt *authctxt)
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/* list of keys supported by the agent */
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if ((r = get_agent_identities(ssh, &agent_fd, &idlist)) == 0) {
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for (j = 0; j < idlist->nkeys; j++) {
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if ((r = sshkey_check_rsa_length(idlist->keys[j],
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options.required_rsa_size)) != 0) {
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debug_fr(r, "ignoring %s agent key",
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sshkey_ssh_name(idlist->keys[j]));
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continue;
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}
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found = 0;
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TAILQ_FOREACH(id, &files, next) {
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/*
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