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Remove Z = 1 special-case in generic point_get_affine.

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As the point may be the output of some private key operation, whether Z
accidentally hit one is secret.

Bug: 239
Change-Id: I7db34cd3b5dd5ca4b96980e8993a9b4eda49eb88
Reviewed-on: https://boringssl-review.googlesource.com/27664
Reviewed-by: Adam Langley <alangley@gmail.com>
This commit is contained in:
David Benjamin 2018-04-23 18:33:20 -04:00 committed by Adam Langley
parent f5858ca008
commit 5c0e0cec83
1 changed files with 48 additions and 58 deletions
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10
crypto/fipsmodule/ec/ec_montgomery.c
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@ -184,15 +184,6 @@ static int ec_GFp_mont_point_get_affine_coordinates(const EC_GROUP *group,
BN_CTX_start(ctx);
if (BN_cmp(&point->Z, &group->one) == 0) {
// |point| is already affine.
if (x != NULL && !BN_from_montgomery(x, &point->X, group->mont, ctx)) {
goto err;
}
if (y != NULL && !BN_from_montgomery(y, &point->Y, group->mont, ctx)) {
goto err;
}
} else {
// transform (X, Y, Z) into (x, y) := (X/Z^2, Y/Z^3)
BIGNUM *Z_1 = BN_CTX_get(ctx);
@ -246,7 +237,6 @@ static int ec_GFp_mont_point_get_affine_coordinates(const EC_GROUP *group,
goto err;
}
}
}
ret = 1;