int BN_hex2bn(BIGNUM **bn, const char *a)
{
    BIGNUM *ret = NULL;
    BN_ULONG l = 0;
    int neg = 0, h, m, i, j, k, c;
    int num;
    if (a == NULL || *a == '\0')
        return 0;
    if (*a == '-') {
        neg = 1;
        a++;
    }
    for (i = 0; i <= INT_MAX / 4 && ossl_isxdigit(a[i]); i++)
        continue;
    if (i == 0 || i > INT_MAX / 4)
        goto err;
    num = i + neg;
    if (bn == NULL)
        return num;
    if (*bn == NULL) {
        if ((ret = BN_new()) == NULL)
            return 0;
    } else {
        ret = *bn;
        BN_zero(ret);
    }
    if (bn_expand(ret, i * 4) == NULL)
        goto err;
    j = i;
    m = 0;
    h = 0;
    while (j > 0) {
        m = (BN_BYTES * 2 <= j) ? BN_BYTES * 2 : j;
        l = 0;
        for (;;) {
            c = a[j - m];
            k = OPENSSL_hexchar2int(c);
            if (k < 0)
                k = 0;
            l = (l << 4) | k;
            if (--m <= 0) {
                ret->d[h++] = l;
                break;
            }
        }
        j -= BN_BYTES * 2;
    }
    ret->top = h;
    bn_correct_top(ret);
    *bn = ret;
    bn_check_top(ret);
    if (ret->top != 0)
        ret->neg = neg;
    return num;
 err:
    if (*bn == NULL)
        BN_free(ret);
    return 0;
}
['static int test_modexp_mont5(void)\n{\n    BIGNUM *a = NULL, *p = NULL, *m = NULL, *d = NULL, *e = NULL;\n    BIGNUM *b = NULL, *n = NULL, *c = NULL;\n    BN_MONT_CTX *mont = NULL;\n    int st = 0;\n    if (!TEST_ptr(a = BN_new())\n            || !TEST_ptr(p = BN_new())\n            || !TEST_ptr(m = BN_new())\n            || !TEST_ptr(d = BN_new())\n            || !TEST_ptr(e = BN_new())\n            || !TEST_ptr(b = BN_new())\n            || !TEST_ptr(n = BN_new())\n            || !TEST_ptr(c = BN_new())\n            || !TEST_ptr(mont = BN_MONT_CTX_new()))\n        goto err;\n    BN_bntest_rand(m, 1024, 0, 1);\n    BN_bntest_rand(a, 1024, 0, 0);\n    BN_zero(p);\n    if (!TEST_true(BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL)))\n        goto err;\n    if (!TEST_BN_eq_one(d))\n        goto err;\n    BN_hex2bn(&a,\n        "7878787878787878787878787878787878787878787878787878787878787878"\n        "7878787878787878787878787878787878787878787878787878787878787878"\n        "7878787878787878787878787878787878787878787878787878787878787878"\n        "7878787878787878787878787878787878787878787878787878787878787878");\n    BN_hex2bn(&b,\n        "095D72C08C097BA488C5E439C655A192EAFB6380073D8C2664668EDDB4060744"\n        "E16E57FB4EDB9AE10A0CEFCDC28A894F689A128379DB279D48A2E20849D68593"\n        "9B7803BCF46CEBF5C533FB0DD35B080593DE5472E3FE5DB951B8BFF9B4CB8F03"\n        "9CC638A5EE8CDD703719F8000E6A9F63BEED5F2FCD52FF293EA05A251BB4AB81");\n    BN_hex2bn(&n,\n        "D78AF684E71DB0C39CFF4E64FB9DB567132CB9C50CC98009FEB820B26F2DED9B"\n        "91B9B5E2B83AE0AE4EB4E0523CA726BFBE969B89FD754F674CE99118C3F2D1C5"\n        "D81FDC7C54E02B60262B241D53C040E99E45826ECA37A804668E690E1AFC1CA4"\n        "2C9A15D84D4954425F0B7642FC0BD9D7B24E2618D2DCC9B729D944BADACFDDAF");\n    BN_MONT_CTX_set(mont, n, ctx);\n    BN_mod_mul_montgomery(c, a, b, mont, ctx);\n    BN_mod_mul_montgomery(d, b, a, mont, ctx);\n    if (!TEST_BN_eq(c, d))\n        goto err;\n    parse_bigBN(&n, bn1strings);\n    parse_bigBN(&a, bn2strings);\n    BN_free(b);\n    b = BN_dup(a);\n    BN_MONT_CTX_set(mont, n, ctx);\n    BN_mod_mul_montgomery(c, a, a, mont, ctx);\n    BN_mod_mul_montgomery(d, a, b, mont, ctx);\n    if (!TEST_BN_eq(c, d))\n        goto err;\n    {\n        static const char *ahex[] = {\n                      "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8FFEADBCFC4DAE7FFF908E92820306B",\n            "9544D954000000006C0000000000000000000000000000000000000000000000",\n            "00000000000000000000FF030202FFFFF8FFEBDBCFC4DAE7FFF908E92820306B",\n            "9544D954000000006C000000FF0302030000000000FFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF01FC00FF02FFFFFFFF",\n            "00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00FCFD",\n            "FCFFFFFFFFFF000000000000000000FF0302030000000000FFFFFFFFFFFFFFFF",\n            "FF00FCFDFDFF030202FF00000000FFFFFFFFFFFFFFFFFF00FCFDFCFFFFFFFFFF",\n            NULL\n        };\n        static const char *nhex[] = {\n                      "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8F8F8F8000000",\n            "00000010000000006C0000000000000000000000000000000000000000000000",\n            "00000000000000000000000000000000000000FFFFFFFFFFFFF8F8F8F8000000",\n            "00000010000000006C000000000000000000000000FFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFF000000000000000000000000000000000000FFFFFFFFFFFFFFFF",\n            "FFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",\n            NULL\n        };\n        parse_bigBN(&a, ahex);\n        parse_bigBN(&n, nhex);\n    }\n    BN_free(b);\n    b = BN_dup(a);\n    BN_MONT_CTX_set(mont, n, ctx);\n    if (!TEST_true(BN_mod_mul_montgomery(c, a, a, mont, ctx))\n            || !TEST_true(BN_mod_mul_montgomery(d, a, b, mont, ctx))\n            || !TEST_BN_eq(c, d))\n        goto err;\n    BN_hex2bn(&a,\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF");\n    BN_hex2bn(&n,\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF");\n    BN_MONT_CTX_set(mont, n, ctx);\n    if (!TEST_false(BN_mod_mul_montgomery(d, a, a, mont, ctx)))\n        goto err;\n    BN_hex2bn(&a,\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF2020202020DF");\n    BN_hex2bn(&b,\n        "2020202020202020202020202020202020202020202020202020202020202020"\n        "2020202020202020202020202020202020202020202020202020202020202020"\n        "20202020202020FF202020202020202020202020202020202020202020202020"\n        "2020202020202020202020202020202020202020202020202020202020202020");\n    BN_hex2bn(&n,\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"\n        "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF2020202020FF");\n    BN_MONT_CTX_set(mont, n, ctx);\n    BN_mod_exp_mont_consttime(c, a, b, n, ctx, mont);\n    BN_mod_exp_mont(d, a, b, n, ctx, mont);\n    if (!TEST_BN_eq(c, d))\n        goto err;\n    BN_bntest_rand(p, 1024, 0, 0);\n    BN_zero(a);\n    if (!TEST_true(BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL))\n            || !TEST_BN_eq_zero(d))\n        goto err;\n    BN_one(a);\n    BN_MONT_CTX_set(mont, m, ctx);\n    if (!TEST_true(BN_from_montgomery(e, a, mont, ctx))\n            || !TEST_true(BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))\n            || !TEST_true(BN_mod_exp_simple(a, e, p, m, ctx))\n            || !TEST_BN_eq(a, d))\n        goto err;\n    BN_bntest_rand(e, 1024, 0, 0);\n    if (!TEST_true(BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))\n            || !TEST_true(BN_mod_exp_simple(a, e, p, m, ctx))\n            || !TEST_BN_eq(a, d))\n        goto err;\n    st = 1;\nerr:\n    BN_MONT_CTX_free(mont);\n    BN_free(a);\n    BN_free(p);\n    BN_free(m);\n    BN_free(d);\n    BN_free(e);\n    BN_free(b);\n    BN_free(n);\n    BN_free(c);\n    return st;\n}', "int BN_hex2bn(BIGNUM **bn, const char *a)\n{\n    BIGNUM *ret = NULL;\n    BN_ULONG l = 0;\n    int neg = 0, h, m, i, j, k, c;\n    int num;\n    if (a == NULL || *a == '\\0')\n        return 0;\n    if (*a == '-') {\n        neg = 1;\n        a++;\n    }\n    for (i = 0; i <= INT_MAX / 4 && ossl_isxdigit(a[i]); i++)\n        continue;\n    if (i == 0 || i > INT_MAX / 4)\n        goto err;\n    num = i + neg;\n    if (bn == NULL)\n        return num;\n    if (*bn == NULL) {\n        if ((ret = BN_new()) == NULL)\n            return 0;\n    } else {\n        ret = *bn;\n        BN_zero(ret);\n    }\n    if (bn_expand(ret, i * 4) == NULL)\n        goto err;\n    j = i;\n    m = 0;\n    h = 0;\n    while (j > 0) {\n        m = (BN_BYTES * 2 <= j) ? BN_BYTES * 2 : j;\n        l = 0;\n        for (;;) {\n            c = a[j - m];\n            k = OPENSSL_hexchar2int(c);\n            if (k < 0)\n                k = 0;\n            l = (l << 4) | k;\n            if (--m <= 0) {\n                ret->d[h++] = l;\n                break;\n            }\n        }\n        j -= BN_BYTES * 2;\n    }\n    ret->top = h;\n    bn_correct_top(ret);\n    *bn = ret;\n    bn_check_top(ret);\n    if (ret->top != 0)\n        ret->neg = neg;\n    return num;\n err:\n    if (*bn == NULL)\n        BN_free(ret);\n    return 0;\n}"]