commit fc599998f4714e1ed5c5efb1d02ac7672fa657b0
Author: Oswald Buddenhagen <[email protected]>
Date: Sun Feb 3 17:34:15 2013 +0100
fix CVE-2013-0289: add SSL subject verification
we did not check a valid certificate's subject at all so far.
this is no problem if the certificate file contains only exactly the
wanted host's certificate - before revision 04fdf7d1 (dec 2000, < v0.4),
this was even enforced (more or less - if the peer cert had been
signed directly by a root cert, it would be accepted as well).
however, when the file contains root certificates (like the system-wide
certificate file typically does), any host with a valid certificate
could pretend to be the wanted host.
src/socket.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++---
1 files changed, 69 insertions(+), 5 deletions(-)
diff --git a/src/socket.c b/src/socket.c
index 22be813..880e6c5 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -28,6 +28,7 @@
# include <openssl/ssl.h>
# include <openssl/err.h>
# include <openssl/hmac.h>
+# include <openssl/x509v3.h>
#endif
#include "isync.h"
@@ -118,6 +119,62 @@ compare_certificates( X509 *cert, X509 *peercert,
return 0;
}
+static int
+host_matches( const char *host, const char *pattern )
+{
+ if (pattern[0] == '*' && pattern[1] == '.') {
+ pattern += 2;
+ if (!(host = strchr( host, '.' )))
+ return 0;
+ host++;
+ }
+
+ return *host && *pattern && !strcasecmp( host, pattern );
+}
+
+static int
+verify_hostname( X509 *cert, const char *hostname )
+{
+ int i, len, found;
+ X509_NAME *subj;
+ STACK_OF(GENERAL_NAME) *subj_alt_names;
+ char cname[1000];
+
+ /* try the DNS subjectAltNames */
+ found = 0;
+ if ((subj_alt_names = X509_get_ext_d2i( cert, NID_subject_alt_name,
NULL, NULL ))) {
+ int num_subj_alt_names = sk_GENERAL_NAME_num( subj_alt_names );
+ for (i = 0; i < num_subj_alt_names; i++) {
+ GENERAL_NAME *subj_alt_name = sk_GENERAL_NAME_value(
subj_alt_names, i );
+ if (subj_alt_name->type == GEN_DNS &&
+ strlen( (const char *)subj_alt_name->d.ia5->data )
== (size_t)subj_alt_name->d.ia5->length &&
+ host_matches( hostname, (const char
*)(subj_alt_name->d.ia5->data) ))
+ {
+ found = 1;
+ break;
+ }
+ }
+ sk_GENERAL_NAME_pop_free( subj_alt_names, GENERAL_NAME_free );
+ }
+ if (found)
+ return 0;
+
+ /* try the common name */
+ if (!(subj = X509_get_subject_name( cert ))) {
+ error( "Error, cannot get certificate subject\n" );
+ return -1;
+ }
+ if ((len = X509_NAME_get_text_by_NID( subj, NID_commonName, cname,
sizeof(cname) )) < 0) {
+ error( "Error, cannot get certificate common name\n" );
+ return -1;
+ }
+ if (strlen( cname ) == (size_t)len && host_matches( hostname, cname ))
+ return 0;
+
+ error( "Error, certificate owner does not match hostname %s\n",
hostname );
+ return -1;
+}
+
#if OPENSSL_VERSION_NUMBER >= 0x00904000L
#define READ_X509_KEY(fp, key) PEM_read_X509( fp, key, 0, 0 )
#else
@@ -146,6 +203,8 @@ verify_cert( const server_conf_t *conf, conn_t *sock )
}
while (conf->cert_file) { /* while() instead of if() so break works */
+ /* Note: this code intentionally does no hostname verification.
*/
+
if (X509_cmp_current_time( X509_get_notBefore( cert )) >= 0) {
error( "Server certificate is not yet valid\n" );
break;
@@ -164,7 +223,7 @@ verify_cert( const server_conf_t *conf, conn_t *sock )
}
err = -1;
for (lcert = 0; READ_X509_KEY( fp, &lcert ); )
- if (!(err = compare_certificates( lcert, cert, md, n )))
+ if (!(err = compare_certificates( lcert, cert, md, n
))) /* TODO: check X509v3 [Extended] Key Usage? */
break;
X509_free( lcert );
fclose( fp );
@@ -193,11 +252,16 @@ verify_cert( const server_conf_t *conf, conn_t *sock )
X509_STORE_CTX_init( &xsc, mconf->cert_store, cert, 0 );
err = X509_verify_cert( &xsc ) > 0 ? 0 : X509_STORE_CTX_get_error( &xsc
);
X509_STORE_CTX_cleanup( &xsc );
- if (!err)
- return 0;
- error( "Error, cannot verify certificate: %s (%d)\n",
- X509_verify_cert_error_string( err ), err );
+ if (err) {
+ error( "Error, cannot verify certificate: %s (%d)\n",
+ X509_verify_cert_error_string( err ), err );
+ goto intcheck;
+ }
+ if (conf->host && verify_hostname( cert, conf->host ) < 0)
+ goto intcheck;
+ return 0;
+ intcheck:
X509_NAME_oneline( X509_get_subject_name( cert ), buf, sizeof(buf) );
info( "\nSubject: %s\n", buf );
X509_NAME_oneline( X509_get_issuer_name( cert ), buf, sizeof(buf) );
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