Merge pull request #788 from libtom/pr/pbes-fix-stack-over-read

PBES - fix stack over-read with malformed PBES2 parameters

Author: karel-m

src/misc/pbes/pbes.c

@@ -44,6 +44,8 @@ int pbes_decrypt(const pbes_arg  *arg, unsigned char *dec_data, unsigned long *d
    if (arg->iv != NULL) {
       iv = arg->iv->data;
    } else {
+      /* PBES1 derives key and IV in one go, the IV follows the key in k; blocklen is 0 for PBES2, which has no IV to derive from */
+      if (arg->type.blocklen != (unsigned long)cipher_descriptor[cid].block_length) return CRYPT_INVALID_PACKET;
       iv = k + klen;
       klen += arg->type.blocklen;
    }

src/misc/pbes/pbes2.c

@@ -197,6 +197,9 @@ int pbes2_extract(const ltc_asn1_list *s, pbes_arg *res)
       } else {
          return CRYPT_INVALID_PACKET;
       }
+   } else {
+      /* PBES2 always carries the IV in the parameters, there is nothing to derive it from */
+      return CRYPT_INVALID_PACKET;
    }
 
    return CRYPT_OK;

tests/pem/pkcs/invalid/pbes2-no-iv.pk8

@@ -0,0 +1,12 @@
+-----BEGIN ENCRYPTED PRIVATE KEY-----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+-----END ENCRYPTED PRIVATE KEY-----