OERV-RUNTIME/boringssl
2
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Make BN_mod_inverse() deal with repeated arguments

Browse Source 
BN_nnmod() can deal with the situation that the first and the second
arguments are the same, but it cannot deal with the first and the
second argument being equal. In that situation, if BN_mod(x, y, x, ctx)
results in a negative x, then the result of BN_nnmod() is zero. This
breaks the strange BN_mod_inverse(m, a, m, ctx).

Reported by Guido Vranken in
https://github.com/openssl/openssl/issues/21110

Change-Id: I8584720660f214f172b3b33716a5e3b29e8f2fd8
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/60365
Reviewed-by: Bob Beck <bbe@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
This commit is contained in:
Theo Buehler
2023-06-02 18:16:40 +00:00
committed by Boringssl LUCI CQ
parent e106b536ee
commit b0341041b0
2 changed files with 13 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crypto/fipsmodule/bn/bn_test.cc
+8
View File
@@ -909,6 +909,14 @@ static void TestModInv(BIGNUMFileTest *t, BN_CTX *ctx) {
bn_mod_inverse_consttime(ret.get(), &no_inverse, a.get(), m.get(), ctx));
EXPECT_BIGNUMS_EQUAL("inv(A) (mod M) (constant-time)", mod_inv.get(),
ret.get());
ASSERT_TRUE(BN_copy(ret.get(), m.get()));
ASSERT_TRUE(BN_mod_inverse(ret.get(), a.get(), ret.get(), ctx));
EXPECT_BIGNUMS_EQUAL("inv(A) (mod M) (ret == m)", mod_inv.get(), ret.get());
ASSERT_TRUE(BN_copy(ret.get(), a.get()));
ASSERT_TRUE(BN_mod_inverse(ret.get(), ret.get(), m.get(), ctx));
EXPECT_BIGNUMS_EQUAL("inv(A) (mod M) (ret == a)", mod_inv.get(), ret.get());
}
static void TestGCD(BIGNUMFileTest *t, BN_CTX *ctx) {
crypto/fipsmodule/bn/gcd.c
+5 -6
View File
@@ -263,15 +263,14 @@ int BN_mod_inverse_odd(BIGNUM *out, int *out_no_inverse, const BIGNUM *a,
// Now Y*a == A (mod |n|).
// Y*a == 1 (mod |n|)
if (!Y->neg && BN_ucmp(Y, n) < 0) {
if (!BN_copy(R, Y)) {
goto err;
}
} else {
if (!BN_nnmod(R, Y, n, ctx)) {
if (Y->neg || BN_ucmp(Y, n) >= 0) {
if (!BN_nnmod(Y, Y, n, ctx)) {
goto err;
}
}
if (!BN_copy(R, Y)) {
goto err;
}
ret = 1;