Add ability to drop overly large packets

[onak.git] / sigcheck.c

diff --git a/sigcheck.c b/sigcheck.c
index 900d3514fab414bd30ee85580b58a5c7108c9067..7732229abf75579516ea56cae281f7526bede028 100644 (file)
--- a/sigcheck.c
+++ b/sigcheck.c
@@ -13,13 +13,13 @@
  * more details.
  *
  * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 51
- * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
 #include <stdint.h>
 
 #include "config.h"
+#include "decodekey.h"
 #include "keyid.h"
 #include "keystructs.h"
 #include "log.h"
@@ -69,6 +69,7 @@ int check_packet_sighash(struct openpgp_publickey *key,
        size_t hashlen[8];
        int chunks, i;
        uint64_t keyid;
+       onak_status_t res;
 
        keyheader[0] = 0x99;
        keyheader[1] = key->publickey->length >> 8;
@@ -108,6 +109,38 @@ int check_packet_sighash(struct openpgp_publickey *key,
        case 4:
                hashtype = sig->data[3];
 
+               /* Check to see if this is an X509 based signature */
+               if (sig->data[2] == 0 || sig->data[2] == 100) {
+                       size_t len;
+
+                       keyid = 0;
+                       res = parse_subpackets(&sig->data[4],
+                                               sig->length - 4, &len,
+                                               &keyid, NULL);
+                       if (res != ONAK_E_OK) {
+                               /* If it parses badly, reject it */
+                               return 0;
+                       }
+                       if (keyid == 0 &&
+                                       /* No unhashed data */
+                                       sig->data[4 + len] == 0 &&
+                                       sig->data[5 + len] == 0 &&
+                                       /* Dummy 0 checksum */
+                                       sig->data[6 + len] == 0 &&
+                                       sig->data[7 + len] == 0 &&
+                                       /* Dummy MPI of 1 */
+                                       sig->data[8 + len] == 0 &&
+                                       sig->data[9 + len] == 1 &&
+                                       sig->data[10 + len] == 1) {
+                               get_keyid(key, &keyid);
+                               logthing(LOGTHING_DEBUG,
+                                       "Skipping X509 signature on 0x%016"
+                                       PRIX64,
+                                       keyid);
+                               return -1;
+                       }
+               }
+
                if (packet != NULL) {
                        if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
                                packetheader[0] = 0x99;
@@ -136,6 +169,10 @@ int check_packet_sighash(struct openpgp_publickey *key,
                hashdata[chunks] = sig->data;
                hashlen[chunks] = siglen = (sig->data[4] << 8) +
                        sig->data[5] + 6;;
+               if (siglen > sig->length) {
+                       /* Signature data exceed packet length, bogus */
+                       return 0;
+               }
                chunks++;
 
                v4trailer[0] = 4;