mt7603e: fix possible infinite loop in BN_mod_sqrt() (#13368)

The calculation in some cases does not finish for non-prime p.

This fixes CVE-2022-0778.

Based on patch by David Benjamin <davidben@google.com>.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
This commit is contained in:
tabudz 2025-02-26 16:44:12 +08:00 committed by GitHub
parent 84884dd637
commit 8a984fc1dd
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GPG Key ID: B5690EEEBB952194

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@ -6555,7 +6555,8 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
/*
* Returns 'ret' such that ret^2 == a (mod p), using the Tonelli/Shanks
* algorithm (cf. Henri Cohen, "A Course in Algebraic Computational Number
* Theory", algorithm 1.5.1). 'p' must be prime!
* Theory", algorithm 1.5.1). 'p' must be prime, otherwise an error or
* an incorrect "result" will be returned.
*/
{
BIGNUM *ret = in;
@ -6871,22 +6872,23 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
goto vrfy;
}
/* find smallest i such that b^(2^i) = 1 */
i = 1;
if (!BN_mod_sqr(t, b, p, ctx))
goto end;
while (!BN_is_one(t)) {
i++;
if (i == e) {
BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
goto end;
/* Find the smallest i, 0 < i < e, such that b^(2^i) = 1. */
for (i = 1; i < e; i++) {
if (i == 1) {
if (!BN_mod_sqr(t, b, p, ctx))
goto end;
} else {
if (!BN_mod_mul(t, t, t, p, ctx))
goto end;
}
if (!BN_mod_mul(t, t, t, p, ctx))
goto end;
if (BN_is_one(t))
break;
}
/* If not found, a is not a square or p is not prime. */
if (i >= e) {
BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
goto end;
}
/* t := y^2^(e - i - 1) */