commit c4824c8f3828f1993d27cbc13a053eade991b875
Author: Oswald Buddenhagen <[email protected]>
Date: Sun Feb 3 16:05:55 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/drv_imap.c | 75 +++++++++++++++++++++++++++++++++++++++++++----
1 files changed, 68 insertions(+), 7 deletions(-)
diff --git a/src/drv_imap.c b/src/drv_imap.c
index 2a84f3d..afe6df0 100644
--- a/src/drv_imap.c
+++ b/src/drv_imap.c
@@ -48,6 +48,7 @@
# include <openssl/ssl.h>
# include <openssl/err.h>
# include <openssl/hmac.h>
+# include <openssl/x509v3.h>
#endif
typedef struct imap_server_conf {
@@ -187,9 +188,65 @@ static const char *Flags[] = {
#if HAVE_LIBSSL
+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 ))) {
+ fprintf( stderr, "Error, cannot get certificate subject\n" );
+ return -1;
+ }
+ if ((len = X509_NAME_get_text_by_NID( subj, NID_commonName, cname,
sizeof(cname) )) < 0) {
+ fprintf( stderr, "Error, cannot get certificate common name\n"
);
+ return -1;
+ }
+ if (strlen( cname ) == (size_t)len && host_matches( hostname, cname ))
+ return 0;
+
+ fprintf( stderr, "Error, certificate owner does not match hostname
%s\n", hostname );
+ return -1;
+}
+
/* this gets called when a certificate is to be verified */
static int
-verify_cert( SSL *ssl )
+verify_cert( SSL *ssl, const char *hostname )
{
X509 *cert;
int err;
@@ -204,12 +261,16 @@ verify_cert( SSL *ssl )
}
err = SSL_get_verify_result( ssl );
- if (err == X509_V_OK)
- return 0;
-
- fprintf( stderr, "Error, can't verify certificate: %s (%d)\n",
- X509_verify_cert_error_string(err), err );
+ if (err != X509_V_OK) {
+ fprintf( stderr, "Error, can't verify certificate: %s (%d)\n",
+ X509_verify_cert_error_string(err), err );
+ goto intcheck;
+ }
+ if (hostname && verify_hostname( cert, hostname ) < 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) );
@@ -1103,7 +1164,7 @@ start_tls( imap_store_t *ctx )
}
/* verify the server certificate */
- if (verify_cert( imap->buf.sock.ssl ))
+ if (verify_cert( imap->buf.sock.ssl, ((imap_store_conf_t
*)ctx->gen.conf)->server->host ))
return 1;
imap->buf.sock.use_ssl = 1;
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