From c80961c646b0962ab152619ac0a7c6a21850a380 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
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 <akuster@mvista.com>
---
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);
}