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From 51b721b69fd08ef1c4c4989f5e12b643e170ff56 Mon Sep 17 00:00:00 2001
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From: Pedro Monreal <pmgdeb@gmail.com>
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Date: Thu, 16 Feb 2023 17:02:38 +0100
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Subject: [PATCH] pk: extend pair-wise consistency to cover DH key generation
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Perform SP800 56A (rev 3) 5.6.2.1.4 Owner Assurance of Pair-wise
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Consistency check, even if we only support ephemeral DH, as it is
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required by FIPS 140-3 IG 10.3.A.
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Signed-off-by: Pedro Monreal <pmgdeb@gmail.com>
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Co-authored-by: Daiki Ueno <ueno@gnu.org>
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---
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 lib/nettle/pk.c | 29 +++++++++++++++++++++++++++++
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 1 file changed, 29 insertions(+)
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diff --git a/lib/nettle/pk.c b/lib/nettle/pk.c
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index d30bca594f..bd9c1b4c74 100644
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--- a/lib/nettle/pk.c
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+++ b/lib/nettle/pk.c
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@@ -2642,6 +2642,35 @@ static int pct_test(gnutls_pk_algorithm_t algo,
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 		}
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 		break;
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 	case GNUTLS_PK_DH:
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+		{
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+			mpz_t y;
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+
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+			/* Perform SP800 56A (rev 3) 5.6.2.1.4 Owner Assurance
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+			 * of Pair-wise Consistency check, even if we only
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+			 * support ephemeral DH, as it is required by FIPS
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+			 * 140-3 IG 10.3.A.
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+			 *
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+			 * Use the private key, x, along with the generator g
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+			 * and prime modulus p included in the domain
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+			 * parameters associated with the key pair to compute
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+			 * g^x mod p. Compare the result to the public key, y.
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+			 */
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+			mpz_init(y);
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+			mpz_powm(y,
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+				 TOMPZ(params->params[DSA_G]),
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+				 TOMPZ(params->params[DSA_X]),
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+				 TOMPZ(params->params[DSA_P]));
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+			if (unlikely
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+			    (mpz_cmp(y, TOMPZ(params->params[DSA_Y])) != 0)) {
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+				ret =
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+				    gnutls_assert_val
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+				    (GNUTLS_E_PK_GENERATION_ERROR);
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+				mpz_clear(y);
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+				goto cleanup;
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+			}
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+			mpz_clear(y);
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+			break;
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+		}
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 	case GNUTLS_PK_ECDH_X25519:
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 	case GNUTLS_PK_ECDH_X448:
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 		ret = 0;
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-- 
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2.39.2
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