Skip signature hash verification for X509 signatures

X509 signatures don't have a valid hash checksum and can't be easily
verified without full X509 support. Skip them in check_packet_sighash
entirely.

diff --git a/decodekey.h b/decodekey.h
index 11e2448374882bdf8d1754b5c6f345299a34eadd..8cd5480027fa39ba21ab2aa6bf9ce79e65391c21 100644 (file)
--- a/decodekey.h
+++ b/decodekey.h
@@ -76,4 +76,17 @@ char **keyuids(struct openpgp_publickey *key, char **primary);
  */
 uint64_t *keysubkeys(struct openpgp_publickey *key);
 
+/**
+ *     parse_subpackets - Parse the subpackets of a Type 4 signature.
+ *     @data: The subpacket data.
+ *     @keyid: A pointer to where we should return the keyid.
+ *     @creationtime: A pointer to where we should return the creation time.
+ *
+ *     This function parses the subkey data of a Type 4 signature and fills
+ *     in the supplied variables. It also returns the length of the data
+ *     processed. If the value of any piece of data is not desired a NULL
+ *     can be passed instead of a pointer to a storage area for that value.
+ */
+int parse_subpackets(unsigned char *data, uint64_t *keyid, time_t *creation);
+
 #endif

diff --git a/sigcheck.c b/sigcheck.c
index 900d3514fab414bd30ee85580b58a5c7108c9067..3ee8d3959e0e2db27e1c8c264d4b631cdec22896 100644 (file)
--- a/sigcheck.c
+++ b/sigcheck.c
@@ -20,6 +20,7 @@
 #include <stdint.h>
 
 #include "config.h"
+#include "decodekey.h"
 #include "keyid.h"
 #include "keystructs.h"
 #include "log.h"
@@ -108,6 +109,32 @@ 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;
+                       len = parse_subpackets(&sig->data[4], &keyid, NULL);
+                       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;