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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vitaly Chikunov <vt@altlinux.org>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: [PATCH 5.4 21/34] crypto: ecrdsa - Fix incorrect use of vli_cmp
Date:   Fri,  3 Jun 2022 19:43:17 +0200
Message-Id: <20220603173816.609143086@linuxfoundation.org>
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From: Vitaly Chikunov <vt@altlinux.org>

commit 7cc7ab73f83ee6d50dc9536bc3355495d8600fad upstream.

Correctly compare values that shall be greater-or-equal and not just
greater.

Fixes: 0d7a78643f69 ("crypto: ecrdsa - add EC-RDSA (GOST 34.10) algorithm")
Cc: <stable@vger.kernel.org>
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 crypto/ecrdsa.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/crypto/ecrdsa.c
+++ b/crypto/ecrdsa.c
@@ -112,15 +112,15 @@ static int ecrdsa_verify(struct akcipher
 
 	/* Step 1: verify that 0 < r < q, 0 < s < q */
 	if (vli_is_zero(r, ndigits) ||
-	    vli_cmp(r, ctx->curve->n, ndigits) == 1 ||
+	    vli_cmp(r, ctx->curve->n, ndigits) >= 0 ||
 	    vli_is_zero(s, ndigits) ||
-	    vli_cmp(s, ctx->curve->n, ndigits) == 1)
+	    vli_cmp(s, ctx->curve->n, ndigits) >= 0)
 		return -EKEYREJECTED;
 
 	/* Step 2: calculate hash (h) of the message (passed as input) */
 	/* Step 3: calculate e = h \mod q */
 	vli_from_le64(e, digest, ndigits);
-	if (vli_cmp(e, ctx->curve->n, ndigits) == 1)
+	if (vli_cmp(e, ctx->curve->n, ndigits) >= 0)
 		vli_sub(e, e, ctx->curve->n, ndigits);
 	if (vli_is_zero(e, ndigits))
 		e[0] = 1;
@@ -136,7 +136,7 @@ static int ecrdsa_verify(struct akcipher
 	/* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */
 	ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key,
 			      ctx->curve);
-	if (vli_cmp(cc.x, ctx->curve->n, ndigits) == 1)
+	if (vli_cmp(cc.x, ctx->curve->n, ndigits) >= 0)
 		vli_sub(cc.x, cc.x, ctx->curve->n, ndigits);
 
 	/* Step 7: if R == r signature is valid */