* 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.
		
			
				
	
	
		
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			78 lines
		
	
	
	
		
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Copied from upstream nettle git repository.
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Removed changes to ChangeLog, to allow this patch to apply to nettle-3.5.
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From 7616541e6eff73353bf682c62e3a68e4fe696707 Mon Sep 17 00:00:00 2001
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From: Niels Möller <nisse@lysator.liu.se>
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Date: Thu, 6 May 2021 21:29:56 +0200
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Subject: [PATCH] Add check that message length to _pkcs1_sec_decrypt is valid.
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* pkcs1-sec-decrypt.c (_pkcs1_sec_decrypt): Check that message
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length is valid, for given key size.
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* testsuite/rsa-sec-decrypt-test.c (test_main): Add test cases for
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calls to rsa_sec_decrypt specifying a too large message length.
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---
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 ChangeLog                        |  7 +++++++
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 pkcs1-sec-decrypt.c              |  4 +++-
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 testsuite/rsa-sec-decrypt-test.c | 17 ++++++++++++++++-
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 3 files changed, 26 insertions(+), 2 deletions(-)
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diff --git a/pkcs1-sec-decrypt.c b/pkcs1-sec-decrypt.c
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index 4f13080e..16833691 100644
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--- a/pkcs1-sec-decrypt.c
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+++ b/pkcs1-sec-decrypt.c
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@@ -63,7 +63,9 @@ _pkcs1_sec_decrypt (size_t length, uint8_t *message,
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   volatile int ok;
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   size_t i, t;
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-  assert (padded_message_length >= length);
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+  /* Message independent branch */
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+  if (length + 11 > padded_message_length)
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+    return 0;
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   t = padded_message_length - length - 1;
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diff --git a/testsuite/rsa-sec-decrypt-test.c b/testsuite/rsa-sec-decrypt-test.c
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index fb0ed3a1..3419322e 100644
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--- a/testsuite/rsa-sec-decrypt-test.c
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+++ b/testsuite/rsa-sec-decrypt-test.c
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@@ -55,6 +55,7 @@ rsa_decrypt_for_test(const struct rsa_public_key *pub,
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 #endif
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 #define PAYLOAD_SIZE 50
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+#define DECRYPTED_SIZE 256
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 void
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 test_main(void)
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 {
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@@ -63,7 +64,7 @@ test_main(void)
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   struct knuth_lfib_ctx random_ctx;
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   uint8_t plaintext[PAYLOAD_SIZE];
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-  uint8_t decrypted[PAYLOAD_SIZE];
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+  uint8_t decrypted[DECRYPTED_SIZE];
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   uint8_t verifybad[PAYLOAD_SIZE];
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   unsigned n_size = 1024;
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   mpz_t gibberish;
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@@ -99,6 +100,20 @@ test_main(void)
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                                     PAYLOAD_SIZE, decrypted, gibberish) == 1);
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       ASSERT (MEMEQ (PAYLOAD_SIZE, plaintext, decrypted));
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+      ASSERT (pub.size > 10);
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+      ASSERT (pub.size <= DECRYPTED_SIZE);
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+
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+      /* Check that too large message length is rejected, largest
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+	 valid size is pub.size - 11. */
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+      ASSERT (!rsa_decrypt_for_test (&pub, &key, &random_ctx,
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+				     (nettle_random_func *) knuth_lfib_random,
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+				     pub.size - 10, decrypted, gibberish));
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+
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+      /* This case used to result in arithmetic underflow and a crash. */
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+      ASSERT (!rsa_decrypt_for_test (&pub, &key, &random_ctx,
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+				     (nettle_random_func *) knuth_lfib_random,
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+				     pub.size, decrypted, gibberish));
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+
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       /* bad one */
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       memcpy(decrypted, verifybad, PAYLOAD_SIZE);
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       nettle_mpz_random_size(garbage, &random_ctx,
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-- 
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2.31.1
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