gnu: nettle-3.5: Add replacement to fix CVE-2021-3580 et al.

* gnu/packages/patches/nettle-3.5-check-_pkcs1_sec_decrypt-msg-len.patch,
gnu/packages/patches/nettle-3.5-CVE-2021-3580-pt1.patch,
gnu/packages/patches/nettle-3.5-CVE-2021-3580-pt2.patch: New files.
* gnu/local.mk (dist_patch_DATA): Add them.
* gnu/packages/nettle.scm (nettle)[replacement]: New field.
(nettle-3.5/fixed): New variable.

1 files changed, 163 insertions, 0 deletions

diff --git a/gnu/packages/patches/nettle-3.5-CVE-2021-3580-pt2.patch b/gnu/packages/patches/nettle-3.5-CVE-2021-3580-pt2.patch
new file mode 100644
index 0000000000..5f19bd80d3
--- /dev/null
+++ b/gnu/packages/patches/nettle-3.5-CVE-2021-3580-pt2.patch
@@ -0,0 +1,163 @@
+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 <nisse@lysator.liu.se>
+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
+