Verify PGP key packet sizes and number of MPIs match expectations

- A key packet must be larger than the "intro" structure to have
  room for the trailing MPIs, ie in order to be valid. This also
  ensures we can safely access the pubkey algorithm data.
- Verify the number of trailing MPI's and their total size matches
  the expectations and packet size exactly before bothering with
  digest calculations.
- Also use sizeof(keyid) instead of "magic eight" and memcpy()
  instead of memmove(), the argument keyid and memory returned
  from rpmDigestFinal() cannot overlap.

diff --git a/rpmio/rpmpgp.c b/rpmio/rpmpgp.c
index 4e72b31..bbc2cdc 100644 (file)
--- a/rpmio/rpmpgp.c
+++ b/rpmio/rpmpgp.c
@@ -986,42 +986,47 @@ static int getFingerprint(const uint8_t *h, size_t hlen, pgpKeyID_t keyid)
 {
     int rc = -1; /* assume failure */
     const uint8_t *se;
+    const uint8_t *pend = h + hlen;
 
     /* We only permit V4 keys, V3 keys are long long since deprecated */
     switch (h[0]) {
     case 4:
       {        pgpPktKeyV4 v = (pgpPktKeyV4) (h);
-       DIGEST_CTX ctx;
-       uint8_t * d = NULL;
-       uint8_t in[3];
-       size_t dlen;
-       int i;
-
-       se = (uint8_t *)(v + 1);
-       switch (v->pubkey_algo) {
-       case PGPPUBKEYALGO_RSA:
-           for (i = 0; i < 2; i++)
-               se += pgpMpiLen(se);
-           break;
-       case PGPPUBKEYALGO_DSA:
-           for (i = 0; i < 4; i++)
-               se += pgpMpiLen(se);
-           break;
+       int mpis = -1;
+
+       /* Packet must be larger than v to have room for the required MPIs */
+       if (hlen > sizeof(*v)) {
+           switch (v->pubkey_algo) {
+           case PGPPUBKEYALGO_RSA:
+               mpis = 2;
+               break;
+           case PGPPUBKEYALGO_DSA:
+               mpis = 4;
+               break;
+           }
        }
 
-       ctx = rpmDigestInit(PGPHASHALGO_SHA1, RPMDIGEST_NONE);
-       i = se - h;
-       in[0] = 0x99;
-       in[1] = i >> 8;
-       in[2] = i;
-       (void) rpmDigestUpdate(ctx, in, 3);
-       (void) rpmDigestUpdate(ctx, h, i);
-       (void) rpmDigestFinal(ctx, (void **)&d, &dlen, 0);
-
-       if (d) {
-           memmove(keyid, (d + (dlen-8)), 8);
-           free(d);
-           rc = 0;
+       se = (uint8_t *)(v + 1);
+       while (se < pend && mpis-- > 0)
+           se += pgpMpiLen(se);
+
+       /* Does the size and number of MPI's match our expectations? */
+       if (se == pend && mpis == 0) {
+           DIGEST_CTX ctx = rpmDigestInit(PGPHASHALGO_SHA1, RPMDIGEST_NONE);
+           uint8_t * d = NULL;
+           size_t dlen;
+           int i = se - h;
+           uint8_t in[3] = { 0x99, (i >> 8), i };
+
+           (void) rpmDigestUpdate(ctx, in, 3);
+           (void) rpmDigestUpdate(ctx, h, i);
+           (void) rpmDigestFinal(ctx, (void **)&d, &dlen, 0);
+
+           if (d) {
+               memcpy(keyid, (d + (dlen-sizeof(keyid))), sizeof(keyid));
+               free(d);
+               rc = 0;
+           }
        }
 
       }        break;