From c80961c646b0962ab152619ac0a7c6a21850a380 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Niels=20M=C3=B6ller?= Date: Tue, 8 Jun 2021 21:32:38 +0200 Subject: [PATCH 2/2] Add input check to rsa_decrypt family of functions. (cherry picked from commit 0ad0b5df315665250dfdaa4a1e087f4799edaefe) Upstream-Status: Backport CVE: CVE-2021-3580 Signed-off-by: Armin Kuster --- ChangeLog | 10 +++++++++- 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, 62 insertions(+), 9 deletions(-) Index: nettle-3.5.1/rsa-decrypt-tr.c =================================================================== --- nettle-3.5.1.orig/rsa-decrypt-tr.c +++ nettle-3.5.1/rsa-decrypt-tr.c @@ -52,6 +52,10 @@ rsa_decrypt_tr(const struct rsa_public_k 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); Index: nettle-3.5.1/rsa-decrypt.c =================================================================== --- nettle-3.5.1.orig/rsa-decrypt.c +++ nettle-3.5.1/rsa-decrypt.c @@ -48,6 +48,16 @@ rsa_decrypt(const struct rsa_private_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); Index: nettle-3.5.1/rsa-sec-decrypt.c =================================================================== --- nettle-3.5.1.orig/rsa-sec-decrypt.c +++ nettle-3.5.1/rsa-sec-decrypt.c @@ -55,6 +55,10 @@ rsa_sec_decrypt(const struct rsa_public_ 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); Index: nettle-3.5.1/rsa.h =================================================================== --- nettle-3.5.1.orig/rsa.h +++ nettle-3.5.1/rsa.h @@ -428,13 +428,14 @@ rsa_sec_decrypt(const struct rsa_public_ 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, Index: nettle-3.5.1/testsuite/rsa-encrypt-test.c =================================================================== --- nettle-3.5.1.orig/testsuite/rsa-encrypt-test.c +++ nettle-3.5.1/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); }