diff options
| -rw-r--r-- | fuzz-common.c | 2 | ||||
| -rw-r--r-- | fuzzer-verify.c | 24 |
2 files changed, 24 insertions, 2 deletions
diff --git a/fuzz-common.c b/fuzz-common.c index b596821..8403a7b 100644 --- a/fuzz-common.c +++ b/fuzz-common.c @@ -22,6 +22,8 @@ void fuzz_common_setup(void) { fuzz.input = m_malloc(sizeof(buffer)); _dropbear_log = fuzz_dropbear_log; crypto_init(); + /* let any messages get flushed */ + setlinebuf(stdout); } int fuzz_set_input(const uint8_t *Data, size_t Size) { diff --git a/fuzzer-verify.c b/fuzzer-verify.c index ed4a9f7..0aa58df 100644 --- a/fuzzer-verify.c +++ b/fuzzer-verify.c @@ -29,8 +29,28 @@ int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { sign_key *key = new_sign_key(); enum signkey_type type = DROPBEAR_SIGNKEY_ANY; if (buf_get_pub_key(fuzz.input, key, &type) == DROPBEAR_SUCCESS) { - /* Don't expect random fuzz input to verify */ - assert(buf_verify(fuzz.input, key, verifydata) == DROPBEAR_FAILURE); + if (buf_verify(fuzz.input, key, verifydata) == DROPBEAR_SUCCESS) { + /* The fuzzer is capable of generating keys with a signature to match. + We don't want false positives if the key is bogus, since a client/server + wouldn't be trusting a bogus key anyway */ + int boguskey = 0; + + if (type == DROPBEAR_SIGNKEY_DSS) { + /* So far have seen dss keys with bad p/q/g domain parameters */ + int pprime, qprime; + assert(mp_prime_is_prime(key->dsskey->p, 5, &pprime) == MP_OKAY); + assert(mp_prime_is_prime(key->dsskey->q, 18, &qprime) == MP_OKAY); + boguskey = !(pprime && qprime); + /* Could also check g**q mod p == 1 */ + } + + if (!boguskey) { + printf("Random key/signature managed to verify!\n"); + abort(); + } + + + } } sign_key_free(key); m_malloc_free_epoch(1, 0); |