view fuzzer-verify.c @ 1663:c795520269f9

Fallback for key gen without hard link support (#89) Add a non-atomic fallback for key generation on platforms where link() is not permitted (such as most stock Android installs) or on filesystems without hard link support (such as FAT).
author Matt Robinson <git@nerdoftheherd.com>
date Sat, 14 Mar 2020 14:37:35 +0000
parents f52919ffd3b1
children ae41624c2198
line wrap: on
line source

#include "fuzz.h"
#include "session.h"
#include "fuzz-wrapfd.h"
#include "debug.h"

static void setup_fuzzer(void) {
	fuzz_common_setup();
}

static buffer *verifydata;

/* Tests reading a public key and verifying a signature */
int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
	static int once = 0;
	if (!once) {
		setup_fuzzer();
		verifydata = buf_new(30);
		buf_putstring(verifydata, "x", 1);
		once = 1;
	}

	if (fuzz_set_input(Data, Size) == DROPBEAR_FAILURE) {
		return 0;
	}

	m_malloc_set_epoch(1);

	if (setjmp(fuzz.jmp) == 0) {
		sign_key *key = new_sign_key();
		enum signkey_type type = DROPBEAR_SIGNKEY_ANY;
		if (buf_get_pub_key(fuzz.input, key, &type) == DROPBEAR_SUCCESS) {
			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, trials;
					trials = mp_prime_rabin_miller_trials(mp_count_bits(key->dsskey->p));
					assert(mp_prime_is_prime(key->dsskey->p, trials, &pprime) == MP_OKAY);
					trials = mp_prime_rabin_miller_trials(mp_count_bits(key->dsskey->q));
					assert(mp_prime_is_prime(key->dsskey->q, trials, &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);
	} else {
		m_malloc_free_epoch(1, 1);
		TRACE(("dropbear_exit longjmped"))
		/* dropbear_exit jumped here */
	}

	return 0;
}