Copied from upstream nettle git repository. Removed changes to ChangeLog, to allow this patch to apply to nettle-3.5. From 0ad0b5df315665250dfdaa4a1e087f4799edaefe Mon Sep 17 00:00:00 2001 From: Niels Möller Date: Mon, 17 May 2021 22:02:47 +0200 Subject: [PATCH 2/2] Add input check to rsa_decrypt family of functions. --- ChangeLog | 8 ++++++++ rsa-decrypt-tr.c | 4 ++++ rsa-decrypt.c | 10 ++++++++++ rsa-sec-decrypt.c | 4 ++++ rsa.h | 5 +++-- testsuite/rsa-encrypt-test.c | 38 ++++++++++++++++++++++++++++++------ 6 files changed, 61 insertions(+), 8 deletions(-) diff --git a/rsa-decrypt-tr.c b/rsa-decrypt-tr.c index 927a8915..4a9e9d74 100644 --- a/rsa-decrypt-tr.c +++ b/rsa-decrypt-tr.c @@ -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); diff --git a/rsa-decrypt.c b/rsa-decrypt.c index 7681439d..540d8baa 100644 --- a/rsa-decrypt.c +++ b/rsa-decrypt.c @@ -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); diff --git a/rsa-sec-decrypt.c b/rsa-sec-decrypt.c index fc4757a0..4c98958d 100644 --- a/rsa-sec-decrypt.c +++ b/rsa-sec-decrypt.c @@ -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); diff --git a/rsa.h b/rsa.h index 3b10155f..2dd35a2d 100644 --- a/rsa.h +++ b/rsa.h @@ -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, diff --git a/testsuite/rsa-encrypt-test.c b/testsuite/rsa-encrypt-test.c index d3bc374b..d1a440f6 100644 --- a/testsuite/rsa-encrypt-test.c +++ b/testsuite/rsa-encrypt-test.c @@ -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); } -- 2.31.1