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synced 2024-11-27 22:03:31 +01:00
Improve test coverage of our strongest-rng code.
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@ -2571,6 +2571,11 @@ crypto_seed_weak_rng(tor_weak_rng_t *rng)
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tor_init_weak_random(rng, seed);
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}
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#ifdef TOR_UNIT_TESTS
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int break_strongest_rng_syscall = 0;
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int break_strongest_rng_fallback = 0;
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#endif
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/** Try to get <b>out_len</b> bytes of the strongest entropy we can generate,
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* via system calls, storing it into <b>out</b>. Return 0 on success, -1 on
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* failure. A maximum request size of 256 bytes is imposed.
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@ -2580,6 +2585,11 @@ crypto_strongest_rand_syscall(uint8_t *out, size_t out_len)
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{
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tor_assert(out_len <= MAX_STRONGEST_RAND_SIZE);
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#ifdef TOR_UNIT_TESTS
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if (break_strongest_rng_syscall)
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return -1;
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#endif
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#if defined(_WIN32)
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static int provider_set = 0;
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static HCRYPTPROV provider;
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@ -2664,6 +2674,11 @@ crypto_strongest_rand_syscall(uint8_t *out, size_t out_len)
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static int
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crypto_strongest_rand_fallback(uint8_t *out, size_t out_len)
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{
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#ifdef TOR_UNIT_TESTS
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if (break_strongest_rng_fallback)
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return -1;
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#endif
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#ifdef _WIN32
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/* Windows exclusively uses crypto_strongest_rand_syscall(). */
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(void)out;
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@ -2701,7 +2716,7 @@ crypto_strongest_rand_fallback(uint8_t *out, size_t out_len)
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* storing it into <b>out</b>. Return 0 on success, -1 on failure. A maximum
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* request size of 256 bytes is imposed.
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*/
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static int
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STATIC int
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crypto_strongest_rand_raw(uint8_t *out, size_t out_len)
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{
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static const size_t sanity_min_size = 16;
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@ -2735,13 +2750,17 @@ crypto_strongest_rand_raw(uint8_t *out, size_t out_len)
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return 0;
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}
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/* We tried max_attempts times to fill a buffer >= 128 bits long,
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/* LCOV_EXCL_START
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*
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* We tried max_attempts times to fill a buffer >= 128 bits long,
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* and each time it returned all '0's. Either the system entropy
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* source is busted, or the user should go out and buy a ticket to
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* every lottery on the planet.
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*/
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log_warn(LD_CRYPTO, "Strong OS entropy returned all zero buffer.");
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return -1;
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/* LCOV_EXCL_STOP */
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}
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/** Try to get <b>out_len</b> bytes of the strongest entropy we can generate,
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@ -317,6 +317,7 @@ void crypto_add_spaces_to_fp(char *out, size_t outlen, const char *in);
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#ifdef CRYPTO_PRIVATE
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STATIC int crypto_force_rand_ssleay(void);
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STATIC int crypto_strongest_rand_raw(uint8_t *out, size_t out_len);
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#endif
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#endif
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@ -190,6 +190,67 @@ test_crypto_rng_range(void *arg)
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;
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}
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extern int break_strongest_rng_fallback;
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extern int break_strongest_rng_syscall;
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static void
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test_crypto_rng_strongest(void *arg)
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{
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const char *how = arg;
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int broken = 0;
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if (how == NULL) {
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;
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} else if (!strcmp(how, "nosyscall")) {
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break_strongest_rng_syscall = 1;
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} else if (!strcmp(how, "nofallback")) {
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break_strongest_rng_fallback = 1;
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} else if (!strcmp(how, "broken")) {
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broken = break_strongest_rng_syscall = break_strongest_rng_fallback = 1;
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}
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#define N 128
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uint8_t combine_and[N];
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uint8_t combine_or[N];
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int i, j;
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memset(combine_and, 0xff, N);
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memset(combine_or, 0, N);
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for (i = 0; i < 100; ++i) { /* 2^-100 chances just don't happen. */
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uint8_t output[N];
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memset(output, 0, N);
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if (how == NULL) {
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/* this one can't fail. */
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crypto_strongest_rand(output, sizeof(output));
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} else {
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int r = crypto_strongest_rand_raw(output, sizeof(output));
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if (r == -1) {
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if (broken) {
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goto done; /* we're fine. */
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}
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/* This function is allowed to break, but only if it always breaks. */
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tt_int_op(i, OP_EQ, 0);
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tt_skip();
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} else {
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tt_assert(! broken);
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}
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}
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for (j = 0; j < N; ++j) {
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combine_and[j] &= output[j];
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combine_or[j] |= output[j];
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}
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}
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for (j = 0; j < N; ++j) {
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tt_int_op(combine_and[j], OP_EQ, 0);
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tt_int_op(combine_or[j], OP_EQ, 0xff);
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}
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done:
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;
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#undef N
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}
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/* Test for rectifying openssl RAND engine. */
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static void
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test_crypto_rng_engine(void *arg)
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@ -2750,6 +2811,13 @@ struct testcase_t crypto_tests[] = {
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CRYPTO_LEGACY(rng),
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{ "rng_range", test_crypto_rng_range, 0, NULL, NULL },
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{ "rng_engine", test_crypto_rng_engine, TT_FORK, NULL, NULL },
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{ "rng_strongest", test_crypto_rng_strongest, TT_FORK, NULL, NULL },
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{ "rng_strongest_nosyscall", test_crypto_rng_strongest, TT_FORK,
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&passthrough_setup, (void*)"nosyscall" },
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{ "rng_strongest_nofallback", test_crypto_rng_strongest, TT_FORK,
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&passthrough_setup, (void*)"nofallback" },
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{ "rng_strongest_broken", test_crypto_rng_strongest, TT_FORK,
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&passthrough_setup, (void*)"broken" },
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{ "openssl_version", test_crypto_openssl_version, TT_FORK, NULL, NULL },
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{ "aes_AES", test_crypto_aes, TT_FORK, &passthrough_setup, (void*)"aes" },
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{ "aes_EVP", test_crypto_aes, TT_FORK, &passthrough_setup, (void*)"evp" },
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