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djm pushed a commit to branch master
in repository openssh.

commit 4e44a79a07d4b88b6a4e5e8c1bed5f58c841b1b8
Author: djm@openbsd.org <djm@openbsd.org>
Date: Thu Sep 24 06:15:11 2015 +0000

upstream commit

add ssh_config CertificateFile option to explicitly list
a certificate; patch from Meghana Bhat on bz#2436; ok markus@

Upstream-ID: 58648ec53c510b41c1f46d8fe293aadc87229ab8
---
readconf.c | 47 +++++++++++++++++++++++++++++++++++++++++-
readconf.h | 8 +++++++-
ssh.1 | 8 ++++++--
ssh.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------
ssh.h | 8 +++++++-
ssh_config.5 | 54 +++++++++++++++++++++++++++++++++++++++++++++----
sshconnect2.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++---------
7 files changed, 226 insertions(+), 25 deletions(-)

diff --git a/readconf.c b/readconf.c
index 354e292..09888b1 100644
--- a/readconf.c
+++ b/readconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.c,v 1.240 2015/08/21 23:53:08 djm Exp $ */
+/* $OpenBSD: readconf.c,v 1.241 2015/09/24 06:15:11 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -135,6 +135,7 @@ typedef enum {
oPasswordAuthentication, oRSAAuthentication,
oChallengeResponseAuthentication, oXAuthLocation,
oIdentityFile, oHostName, oPort, oCipher, oRemoteForward, oLocalForward,
+ oCertificateFile,
oUser, oEscapeChar, oRhostsRSAAuthentication, oProxyCommand,
oGlobalKnownHostsFile, oUserKnownHostsFile, oConnectionAttempts,
oBatchMode, oCheckHostIP, oStrictHostKeyChecking, oCompression,
@@ -202,6 +203,7 @@ static struct {
{ "identityfile", oIdentityFile },
{ "identityfile2", oIdentityFile }, /* obsolete */
{ "identitiesonly", oIdentitiesOnly },
+ { "certificatefile", oCertificateFile },
{ "hostname", oHostName },
{ "hostkeyalias", oHostKeyAlias },
{ "proxycommand", oProxyCommand },
@@ -366,6 +368,30 @@ clear_forwardings(Options *options)
}

void
+add_certificate_file(Options *options, const char *path, int userprovided)
+{
+ int i;
+
+ if (options->num_certificate_files >= SSH_MAX_CERTIFICATE_FILES)
+ fatal("Too many certificate files specified (max %d)",
+ SSH_MAX_CERTIFICATE_FILES);
+
+ /* Avoid registering duplicates */
+ for (i = 0; i < options->num_certificate_files; i++) {
+ if (options->certificate_file_userprovided[i] == userprovided &&
+ strcmp(options->certificate_files[i], path) == 0) {
+ debug2("%s: ignoring duplicate key %s", __func__, path);
+ return;
+ }
+ }
+
+ options->certificate_file_userprovided[options->num_certificate_files] =
+ userprovided;
+ options->certificate_files[options->num_certificate_files++] =
+ xstrdup(path);
+}
+
+void
add_identity_file(Options *options, const char *dir, const char *filename,
int userprovided)
{
@@ -981,6 +1007,24 @@ parse_time:
}
break;

+ case oCertificateFile:
+ arg = strdelim(&s);
+ if (!arg || *arg == '\0')
+ fatal("%.200s line %d: Missing argument.",
+ filename, linenum);
+ if (*activep) {
+ intptr = &options->num_certificate_files;
+ if (*intptr >= SSH_MAX_CERTIFICATE_FILES) {
+ fatal("%.200s line %d: Too many certificate "
+ "files specified (max %d).",
+ filename, linenum,
+ SSH_MAX_CERTIFICATE_FILES);
+ }
+ add_certificate_file(options, arg,
+ flags & SSHCONF_USERCONF);
+ }
+ break;
+
case oXAuthLocation:
charptr=&options->xauth_location;
goto parse_string;
@@ -1625,6 +1669,7 @@ initialize_options(Options * options)
options->hostkeyalgorithms = NULL;
options->protocol = SSH_PROTO_UNKNOWN;
options->num_identity_files = 0;
+ options->num_certificate_files = 0;
options->hostname = NULL;
options->host_key_alias = NULL;
options->proxy_command = NULL;
diff --git a/readconf.h b/readconf.h
index bb2d552..6d6927f 100644
--- a/readconf.h
+++ b/readconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.h,v 1.110 2015/07/10 06:21:53 markus Exp $ */
+/* $OpenBSD: readconf.h,v 1.111 2015/09/24 06:15:11 djm Exp $ */

/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -95,6 +95,11 @@ typedef struct {
int identity_file_userprovided[SSH_MAX_IDENTITY_FILES];
struct sshkey *identity_keys[SSH_MAX_IDENTITY_FILES];

+ int num_certificate_files; /* Number of extra certificates for ssh. */
+ char *certificate_files[SSH_MAX_CERTIFICATE_FILES];
+ int certificate_file_userprovided[SSH_MAX_CERTIFICATE_FILES];
+ struct sshkey *certificates[SSH_MAX_CERTIFICATE_FILES];
+
/* Local TCP/IP forward requests. */
int num_local_forwards;
struct Forward *local_forwards;
@@ -194,5 +199,6 @@ void dump_client_config(Options *o, const char *host);
void add_local_forward(Options *, const struct Forward *);
void add_remote_forward(Options *, const struct Forward *);
void add_identity_file(Options *, const char *, const char *, int);
+void add_certificate_file(Options *, const char *, int);

#endif /* READCONF_H */
diff --git a/ssh.1 b/ssh.1
index 495b787..b08fa79 100644
--- a/ssh.1
+++ b/ssh.1
@@ -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: ssh.1,v 1.362 2015/09/11 03:42:32 djm Exp $
-.Dd $Mdocdate: September 11 2015 $
+.\" $OpenBSD: ssh.1,v 1.363 2015/09/24 06:15:11 djm Exp $
+.Dd $Mdocdate: September 24 2015 $
.Dt SSH 1
.Os
.Sh NAME
@@ -304,6 +304,9 @@ It is possible to have multiple
.Fl i
options (and multiple identities specified in
configuration files).
+If no certificates have been explicitly specified by
+.Cm CertificateFile
+directive,
.Nm
will also try to load certificate information from the filename obtained
by appending
@@ -468,6 +471,7 @@ For full details of the options listed below, and their possible values, see
.It CanonicalizeHostname
.It CanonicalizeMaxDots
.It CanonicalizePermittedCNAMEs
+.It CertificateFile
.It ChallengeResponseAuthentication
.It CheckHostIP
.It Cipher
diff --git a/ssh.c b/ssh.c
index 91911d3..a6e4de3 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.425 2015/09/11 06:55:46 jmc Exp $ */
+/* $OpenBSD: ssh.c,v 1.426 2015/09/24 06:15:11 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1354,6 +1354,10 @@ main(int ac, char **av)
options.identity_keys[i] = NULL;
}
}
+ for (i = 0; i < options.num_certificate_files; i++) {
+ free(options.certificate_files[i]);
+ options.certificate_files[i] = NULL;
+ }

exit_status = compat20 ? ssh_session2() : ssh_session();
packet_close();
@@ -1940,25 +1944,30 @@ ssh_session2(void)
options.escape_char : SSH_ESCAPECHAR_NONE, id);
}

+/* Loads all IdentityFile and CertificateFile keys */
static void
load_public_identity_files(void)
{
char *filename, *cp, thishost[NI_MAXHOST];
char *pwdir = NULL, *pwname = NULL;
- int i = 0;
Key *public;
struct passwd *pw;
- u_int n_ids;
+ int i;
+ u_int n_ids, n_certs;
char *identity_files[SSH_MAX_IDENTITY_FILES];
Key *identity_keys[SSH_MAX_IDENTITY_FILES];
+ char *certificate_files[SSH_MAX_CERTIFICATE_FILES];
+ struct sshkey *certificates[SSH_MAX_CERTIFICATE_FILES];
#ifdef ENABLE_PKCS11
Key **keys;
int nkeys;
#endif /* PKCS11 */

- n_ids = 0;
+ n_ids = n_certs = 0;
memset(identity_files, 0, sizeof(identity_files));
memset(identity_keys, 0, sizeof(identity_keys));
+ memset(certificate_files, 0, sizeof(certificate_files));
+ memset(certificates, 0, sizeof(certificates));

#ifdef ENABLE_PKCS11
if (options.pkcs11_provider != NULL &&
@@ -1990,6 +1999,7 @@ load_public_identity_files(void)
if (n_ids >= SSH_MAX_IDENTITY_FILES ||
strcasecmp(options.identity_files[i], "none") == 0) {
free(options.identity_files[i]);
+ options.identity_files[i] = NULL;
continue;
}
cp = tilde_expand_filename(options.identity_files[i],
@@ -2008,7 +2018,12 @@ load_public_identity_files(void)
if (++n_ids >= SSH_MAX_IDENTITY_FILES)
continue;

- /* Try to add the certificate variant too */
+ /*
+ * If no certificates have been explicitly listed then try
+ * to add the default certificate variant too.
+ */
+ if (options.num_certificate_files != 0)
+ continue;
xasprintf(&cp, "%s-cert", filename);
public = key_load_public(cp, NULL);
debug("identity file %s type %d", cp,
@@ -2025,14 +2040,50 @@ load_public_identity_files(void)
continue;
}
identity_keys[n_ids] = public;
- /* point to the original path, most likely the private key */
- identity_files[n_ids] = xstrdup(filename);
+ identity_files[n_ids] = cp;
n_ids++;
}
+
+ if (options.num_certificate_files > SSH_MAX_CERTIFICATE_FILES)
+ fatal("%s: too many certificates", __func__);
+ for (i = 0; i < options.num_certificate_files; i++) {
+ cp = tilde_expand_filename(options.certificate_files[i],
+ original_real_uid);
+ filename = percent_expand(cp, "d", pwdir,
+ "u", pwname, "l", thishost, "h", host,
+ "r", options.user, (char *)NULL);
+ free(cp);
+
+ public = key_load_public(filename, NULL);
+ debug("certificate file %s type %d", filename,
+ public ? public->type : -1);
+ free(options.certificate_files[i]);
+ options.certificate_files[i] = NULL;
+ if (public == NULL) {
+ free(filename);
+ continue;
+ }
+ if (!key_is_cert(public)) {
+ debug("%s: key %s type %s is not a certificate",
+ __func__, filename, key_type(public));
+ key_free(public);
+ free(filename);
+ continue;
+ }
+ certificate_files[n_certs] = filename;
+ certificates[n_certs] = public;
+ ++n_certs;
+ }
+
options.num_identity_files = n_ids;
memcpy(options.identity_files, identity_files, sizeof(identity_files));
memcpy(options.identity_keys, identity_keys, sizeof(identity_keys));

+ options.num_certificate_files = n_certs;
+ memcpy(options.certificate_files,
+ certificate_files, sizeof(certificate_files));
+ memcpy(options.certificates, certificates, sizeof(certificates));
+
explicit_bzero(pwname, strlen(pwname));
free(pwname);
explicit_bzero(pwdir, strlen(pwdir));
diff --git a/ssh.h b/ssh.h
index 39c7e18..80eaeb3 100644
--- a/ssh.h
+++ b/ssh.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.h,v 1.81 2015/08/04 05:23:06 djm Exp $ */
+/* $OpenBSD: ssh.h,v 1.82 2015/09/24 06:15:11 djm Exp $ */

/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -19,6 +19,12 @@
#define SSH_DEFAULT_PORT 22

/*
+ * Maximum number of certificate files that can be specified
+ * in configuration files or on the command line.
+ */
+#define SSH_MAX_CERTIFICATE_FILES 100
+
+/*
* Maximum number of RSA authentication identity files that can be specified
* in configuration files or on the command line.
*/
diff --git a/ssh_config.5 b/ssh_config.5
index 54c42ab..39cf932 100644
--- a/ssh_config.5
+++ b/ssh_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: ssh_config.5,v 1.220 2015/09/22 08:33:23 sobrado Exp $
-.Dd $Mdocdate: September 22 2015 $
+.\" $OpenBSD: ssh_config.5,v 1.221 2015/09/24 06:15:11 djm Exp $
+.Dd $Mdocdate: September 24 2015 $
.Dt SSH_CONFIG 5
.Os
.Sh NAME
@@ -325,6 +325,41 @@ to be canonicalized to names in the
or
.Dq *.c.example.com
domains.
+.It Cm CertificateFile
+Specifies a file from which the user's certificate is read.
+A corresponding private key must be provided separately in order
+to use this certificate either
+from an
+.Cm IdentityFile
+directive or
+.Fl i
+flag to
+.Xr ssh 1 ,
+via
+.Xr ssh-agent 1 ,
+or via a
+.Cm PKCS11Provider .
+.Pp
+The file name may use the tilde
+syntax to refer to a user's home directory or one of the following
+escape characters:
+.Ql %d
+(local user's home directory),
+.Ql %u
+(local user name),
+.Ql %l
+(local host name),
+.Ql %h
+(remote host name) or
+.Ql %r
+(remote user name).
+.Pp
+It is possible to have multiple certificate files specified in
+configuration files; these certificates will be tried in sequence.
+Multiple
+.Cm CertificateFile
+directives will add to the list of certificates used for
+authentication.
.It Cm ChallengeResponseAuthentication
Specifies whether to use challenge-response authentication.
The argument to this keyword must be
@@ -869,9 +904,13 @@ specifications).
.It Cm IdentitiesOnly
Specifies that
.Xr ssh 1
-should only use the authentication identity files configured in the
+should only use the authentication identity and certificate files explicitly
+configured in the
.Nm
-files,
+files
+or passed on the
+.Xr ssh 1
+command-line,
even if
.Xr ssh-agent 1
or a
@@ -901,6 +940,8 @@ Additionally, any identities represented by the authentication agent
will be used for authentication unless
.Cm IdentitiesOnly
is set.
+If no certificates have been explicitly specified by
+.Cm CertificateFile ,
.Xr ssh 1
will try to load certificate information from the filename obtained by
appending
@@ -934,6 +975,11 @@ differs from that of other configuration directives).
may be used in conjunction with
.Cm IdentitiesOnly
to select which identities in an agent are offered during authentication.
+.Cm IdentityFile
+may also be used in conjunction with
+.Cm CertificateFile
+in order to provide any certificate also needed for authentication with
+the identity.
.It Cm IgnoreUnknown
Specifies a pattern-list of unknown options to be ignored if they are
encountered in configuration parsing.
diff --git a/sshconnect2.c b/sshconnect2.c
index 7751031..e821883 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.226 2015/07/30 00:01:34 djm Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.227 2015/09/24 06:15:11 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2008 Damien Miller. All rights reserved.
@@ -1001,18 +1001,17 @@ static int
sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
{
Buffer b;
+ Identity *private_id;
u_char *blob, *signature;
- u_int bloblen;
size_t slen;
- u_int skip = 0;
- int ret = -1;
- int have_sig = 1;
+ u_int bloblen, skip = 0;
+ int matched, ret = -1, have_sig = 1;
char *fp;

if ((fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL)
return 0;
- debug3("sign_and_send_pubkey: %s %s", key_type(id->key), fp);
+ debug3("%s: %s %s", __func__, key_type(id->key), fp);
free(fp);

if (key_to_blob(id->key, &blob, &bloblen) == 0) {
@@ -1044,6 +1043,36 @@ sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
}
buffer_put_string(&b, blob, bloblen);

+ /*
+ * If the key is an certificate, try to find a matching private key
+ * and use it to complete the signature.
+ * If no such private key exists, return failure and continue with
+ * other methods of authentication.
+ */
+ if (key_is_cert(id->key)) {
+ matched = 0;
+ TAILQ_FOREACH(private_id, &authctxt->keys, next) {
+ if (sshkey_equal_public(id->key, private_id->key) &&
+ id->key->type != private_id->key->type) {
+ id = private_id;
+ matched = 1;
+ break;
+ }
+ }
+ if (matched) {
+ debug2("%s: using private key \"%s\"%s for "
+ "certificate", __func__, id->filename,
+ id->agent_fd != -1 ? " from agent" : "");
+ } else {
+ /* XXX maybe verbose/error? */
+ debug("%s: no private key for certificate "
+ "\"%s\"", __func__, id->filename);
+ free(blob);
+ buffer_free(&b);
+ return 0;
+ }
+ }
+
/* generate signature */
ret = identity_sign(id, &signature, &slen,
buffer_ptr(&b), buffer_len(&b), datafellows);
@@ -1180,9 +1209,11 @@ load_identity_file(char *filename, int userprovided)

/*
* try keys in the following order:
- * 1. agent keys that are found in the config file
- * 2. other agent keys
- * 3. keys that are only listed in the config file
+ * 1. certificates listed in the config file
+ * 2. other input certificates
+ * 3. agent keys that are found in the config file
+ * 4. other agent keys
+ * 5. keys that are only listed in the config file
*/
static void
pubkey_prepare(Authctxt *authctxt)
@@ -1236,6 +1267,18 @@ pubkey_prepare(Authctxt *authctxt)
free(id);
}
}
+ /* list of certificates specified by user */
+ for (i = 0; i < options.num_certificate_files; i++) {
+ key = options.certificates[i];
+ if (!key_is_cert(key) || key->cert == NULL ||
+ key->cert->type != SSH2_CERT_TYPE_USER)
+ continue;
+ id = xcalloc(1, sizeof(*id));
+ id->key = key;
+ id->filename = xstrdup(options.certificate_files[i]);
+ id->userprovided = options.certificate_file_userprovided[i];
+ TAILQ_INSERT_TAIL(preferred, id, next);
+ }
/* list of keys supported by the agent */
if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
if (r != SSH_ERR_AGENT_NOT_PRESENT)

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