Commit 0ad0b5df authored by Niels Möller's avatar Niels Möller
Browse files

Add input check to rsa_decrypt family of functions.

parent 485b5e28
2021-05-17 Niels Möller <nisse@lysator.liu.se>
* rsa-decrypt-tr.c (rsa_decrypt_tr): Check up-front that input is
in range.
* rsa-sec-decrypt.c (rsa_sec_decrypt): Likewise.
* rsa-decrypt.c (rsa_decrypt): Likewise.
* testsuite/rsa-encrypt-test.c (test_main): Add tests with input > n.
2021-05-14 Niels Möller <nisse@lysator.liu.se>
* rsa-sign-tr.c (rsa_sec_blind): Delete mn argument.
......
......@@ -52,6 +52,10 @@ rsa_decrypt_tr(const struct rsa_public_key *pub,
mp_size_t key_limb_size;
int res;
/* First check that input is in range. */
if (mpz_sgn (gibberish) < 0 || mpz_cmp (gibberish, pub->n) >= 0)
return 0;
key_limb_size = mpz_size(pub->n);
TMP_GMP_ALLOC (m, key_limb_size);
......
......@@ -48,6 +48,16 @@ rsa_decrypt(const struct rsa_private_key *key,
int res;
mpz_init(m);
/* First check that input is in range. Since we don't have the
public key available here, we need to reconstruct n. */
mpz_mul (m, key->p, key->q);
if (mpz_sgn (gibberish) < 0 || mpz_cmp (gibberish, m) >= 0)
{
mpz_clear (m);
return 0;
}
rsa_compute_root(key, m, gibberish);
res = pkcs1_decrypt (key->size, m, length, message);
......
......@@ -55,6 +55,10 @@ rsa_sec_decrypt(const struct rsa_public_key *pub,
TMP_GMP_DECL (em, uint8_t);
int res;
/* First check that input is in range. */
if (mpz_sgn (gibberish) < 0 || mpz_cmp (gibberish, pub->n) >= 0)
return 0;
TMP_GMP_ALLOC (m, mpz_size(pub->n));
TMP_GMP_ALLOC (em, key->size);
......
......@@ -428,13 +428,14 @@ rsa_sec_decrypt(const struct rsa_public_key *pub,
size_t length, uint8_t *message,
const mpz_t gibberish);
/* Compute x, the e:th root of m. Calling it with x == m is allowed. */
/* Compute x, the e:th root of m. Calling it with x == m is allowed.
It is required that 0 <= m < n. */
void
rsa_compute_root(const struct rsa_private_key *key,
mpz_t x, const mpz_t m);
/* Safer variant, using RSA blinding, and checking the result after
CRT. */
CRT. It is required that 0 <= m < n. */
int
rsa_compute_root_tr(const struct rsa_public_key *pub,
const struct rsa_private_key *key,
......
......@@ -19,11 +19,12 @@ test_main(void)
uint8_t after;
mpz_t gibberish;
mpz_t zero;
mpz_t bad_input;
rsa_private_key_init(&key);
rsa_public_key_init(&pub);
mpz_init(gibberish);
mpz_init(bad_input);
knuth_lfib_init(&lfib, 17);
......@@ -103,15 +104,40 @@ test_main(void)
ASSERT(decrypted[0] == 'A');
/* Test zero input. */
mpz_init_set_ui (zero, 0);
mpz_set_ui (bad_input, 0);
decrypted_length = msg_length;
ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, zero));
ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, bad_input));
ASSERT(!rsa_decrypt_tr(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
&decrypted_length, decrypted, zero));
&decrypted_length, decrypted, bad_input));
ASSERT(!rsa_sec_decrypt(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
decrypted_length, decrypted, zero));
decrypted_length, decrypted, bad_input));
ASSERT(decrypted_length == msg_length);
/* Test input that is slightly larger than n */
mpz_add(bad_input, gibberish, pub.n);
decrypted_length = msg_length;
ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, bad_input));
ASSERT(!rsa_decrypt_tr(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
&decrypted_length, decrypted, bad_input));
ASSERT(!rsa_sec_decrypt(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
decrypted_length, decrypted, bad_input));
ASSERT(decrypted_length == msg_length);
/* Test input that is considerably larger than n */
mpz_mul_2exp (bad_input, pub.n, 100);
mpz_add (bad_input, bad_input, gibberish);
decrypted_length = msg_length;
ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, bad_input));
ASSERT(!rsa_decrypt_tr(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
&decrypted_length, decrypted, bad_input));
ASSERT(!rsa_sec_decrypt(&pub, &key,
&lfib, (nettle_random_func *) knuth_lfib_random,
decrypted_length, decrypted, bad_input));
ASSERT(decrypted_length == msg_length);
/* Test invalid key. */
......@@ -124,6 +150,6 @@ test_main(void)
rsa_private_key_clear(&key);
rsa_public_key_clear(&pub);
mpz_clear(gibberish);
mpz_clear(zero);
mpz_clear(bad_input);
free(decrypted);
}
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