view fuzzer-verify.c @ 1665:7c17995bcdfb

Improve address logging on early exit messages (#83) Change 'Early exit' and 'Exit before auth' messages to include the IP address & port as part of the message. This allows log scanning utilities such as 'fail2ban' to obtain the offending IP address as part of the failure event instead of extracting the PID from the message and then scanning the log again for match 'child connection from' messages Signed-off-by: Kevin Darbyshire-Bryant <[email protected]>
author Kevin Darbyshire-Bryant <6500011+ldir-EDB0@users.noreply.github.com>
date Wed, 18 Mar 2020 15:28:56 +0000
parents f52919ffd3b1
children ae41624c2198
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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;
}