[PATCH 5.17 41/75] crypto: ecrdsa - Fix incorrect use of vli_cmp

Greg Kroah-Hartman
2022-06-03T18:11:37Z

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
@@ -113,15 +113,15 @@ 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;
@@ -137,7 +137,7 @@ 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 */