diff -up fetchmail-6.3.9/socket.c_orig fetchmail-6.3.9/socket.c
--- fetchmail-6.3.9/socket.c_orig 2009-08-06 11:34:12.000000000 +0200
+++ fetchmail-6.3.9/socket.c 2009-08-06 11:47:25.000000000 +0200
@@ -632,6 +632,13 @@ static int SSL_verify_callback( int ok_r
report(stderr, GT_("Bad certificate: Subject CommonName too long!\n"));
return (0);
}
+ if ((size_t)i > strlen(buf)) {
+ /* Name contains embedded NUL characters, so we complain. This is likely
+ * a certificate spoofing attack. */
+ report(stderr, GT_("Bad certificate: Subject CommonName contains NUL, aborting!\n"));
+ return 0;
+ }
+
if (_ssl_server_cname != NULL) {
char *p1 = buf;
char *p2 = _ssl_server_cname;
@@ -643,12 +650,19 @@ static int SSL_verify_callback( int ok_r
* first find a match among alternative names */
gens = X509_get_ext_d2i(x509_cert, NID_subject_alt_name, NULL, NULL);
if (gens) {
- int i, r;
- for (i = 0, r = sk_GENERAL_NAME_num(gens); i < r; ++i) {
- const GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i);
- if (gn->type == GEN_DNS) {
- char *p1 = (char *)gn->d.ia5->data;
- char *p2 = _ssl_server_cname;
+ int j, r;
+ for (j = 0, r = sk_GENERAL_NAME_num(gens); j < r; ++j) {
+ const GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, j);
+ if (gn->type == GEN_DNS) {
+ char *p1 = (char *)gn->d.ia5->data;
+ char *p2 = _ssl_server_cname;
+ /* Name contains embedded NUL characters, so we complain. This
+ * is likely a certificate spoofing attack. */
+ if ((size_t)gn->d.ia5->length != strlen(p1)) {
+ report(stderr, GT_("Bad certificate: Subject Alternative Name contains NUL, aborting!\n"));
+ sk_GENERAL_NAME_free(gens);
+ return 0;
+ }
if (outlevel >= O_VERBOSE)
report(stderr, "Subject Alternative Name: %s\n", p1);
if (*p1 == '*') {