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Merge remote-tracking branch 'teor/rand-failure-modes-v2'
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09e0ae0588
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changes/rand-failure-modes
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5
changes/rand-failure-modes
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o Minor features (unit tests, random number generation):
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- Add unit tests that check for common RNG failure modes, such as
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returning all zeroes, identical values, or incrementing values
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(OpenSSL's rand_predictable feature).
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Patch by "teor".
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@ -1831,6 +1831,110 @@ test_crypto_siphash(void *arg)
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;
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}
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/* We want the likelihood that the random buffer exhibits any regular pattern
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* to be far less than the memory bit error rate in the int return value.
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* Using 2048 bits provides a failure rate of 1/(3 * 10^616), and we call
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* 3 functions, leading to an overall error rate of 1/10^616.
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* This is comparable with the 1/10^603 failure rate of test_crypto_rng_range.
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*/
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#define FAILURE_MODE_BUFFER_SIZE (2048/8)
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/** Check crypto_rand for a failure mode where it does nothing to the buffer,
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* or it sets the buffer to all zeroes. Return 0 when the check passes,
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* or -1 when it fails. */
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static int
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crypto_rand_check_failure_mode_zero(void)
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{
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char buf[FAILURE_MODE_BUFFER_SIZE];
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memset(buf, 0, FAILURE_MODE_BUFFER_SIZE);
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crypto_rand(buf, FAILURE_MODE_BUFFER_SIZE);
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for (size_t i = 0; i < FAILURE_MODE_BUFFER_SIZE; i++) {
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if (buf[i] != 0) {
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return 0;
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}
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}
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return -1;
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}
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/** Check crypto_rand for a failure mode where every int64_t in the buffer is
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* the same. Return 0 when the check passes, or -1 when it fails. */
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static int
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crypto_rand_check_failure_mode_identical(void)
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{
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/* just in case the buffer size isn't a multiple of sizeof(int64_t) */
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#define FAILURE_MODE_BUFFER_SIZE_I64 \
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(FAILURE_MODE_BUFFER_SIZE/SIZEOF_INT64_T)
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#define FAILURE_MODE_BUFFER_SIZE_I64_BYTES \
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(FAILURE_MODE_BUFFER_SIZE_I64*SIZEOF_INT64_T)
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#if FAILURE_MODE_BUFFER_SIZE_I64 < 2
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#error FAILURE_MODE_BUFFER_SIZE needs to be at least 2*SIZEOF_INT64_T
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#endif
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int64_t buf[FAILURE_MODE_BUFFER_SIZE_I64];
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memset(buf, 0, FAILURE_MODE_BUFFER_SIZE_I64_BYTES);
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crypto_rand((char *)buf, FAILURE_MODE_BUFFER_SIZE_I64_BYTES);
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for (size_t i = 1; i < FAILURE_MODE_BUFFER_SIZE_I64; i++) {
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if (buf[i] != buf[i-1]) {
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return 0;
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}
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}
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return -1;
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}
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/** Check crypto_rand for a failure mode where it increments the "random"
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* value by 1 for every byte in the buffer. (This is OpenSSL's PREDICT mode.)
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* Return 0 when the check passes, or -1 when it fails. */
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static int
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crypto_rand_check_failure_mode_predict(void)
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{
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unsigned char buf[FAILURE_MODE_BUFFER_SIZE];
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memset(buf, 0, FAILURE_MODE_BUFFER_SIZE);
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crypto_rand((char *)buf, FAILURE_MODE_BUFFER_SIZE);
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for (size_t i = 1; i < FAILURE_MODE_BUFFER_SIZE; i++) {
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/* check if the last byte was incremented by 1, including integer
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* wrapping */
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if (buf[i] - buf[i-1] != 1 && buf[i-1] - buf[i] != 255) {
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return 0;
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}
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}
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return -1;
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}
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#undef FAILURE_MODE_BUFFER_SIZE
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static void
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test_crypto_failure_modes(void *arg)
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{
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int rv = 0;
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(void)arg;
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rv = crypto_early_init();
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tt_assert(rv == 0);
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/* Check random works */
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rv = crypto_rand_check_failure_mode_zero();
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tt_assert(rv == 0);
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rv = crypto_rand_check_failure_mode_identical();
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tt_assert(rv == 0);
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rv = crypto_rand_check_failure_mode_predict();
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tt_assert(rv == 0);
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done:
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;
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}
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#define CRYPTO_LEGACY(name) \
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{ #name, test_crypto_ ## name , 0, NULL, NULL }
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@ -1869,6 +1973,7 @@ struct testcase_t crypto_tests[] = {
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{ "ed25519_fuzz_donna", test_crypto_ed25519_fuzz_donna, TT_FORK, NULL,
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NULL },
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{ "siphash", test_crypto_siphash, 0, NULL, NULL },
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{ "failure_modes", test_crypto_failure_modes, TT_FORK, NULL, NULL },
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END_OF_TESTCASES
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};
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