int asn1_utctime_to_tm(struct tm *tm, const ASN1_UTCTIME *d)
{
    static const int min[8] = { 0, 1, 1, 0, 0, 0, 0, 0 };
    static const int max[8] = { 99, 12, 31, 23, 59, 59, 12, 59 };
    char *a;
    int n, i, l, o;

    if (d->type != V_ASN1_UTCTIME)
        return (0);
    l = d->length;
    a = (char *)d->data;
    o = 0;

    if (l < 11)
        goto err;
    for (i = 0; i < 6; i++) {
        if ((i == 5) && ((a[o] == 'Z') || (a[o] == '+') || (a[o] == '-'))) {
            i++;
            if (tm)
                tm->tm_sec = 0;
            break;
        }
        if ((a[o] < '0') || (a[o] > '9'))
            goto err;
        n = a[o] - '0';
        if (++o > l)
            goto err;

        if ((a[o] < '0') || (a[o] > '9'))
            goto err;
        n = (n * 10) + a[o] - '0';
        if (++o > l)
            goto err;

        if ((n < min[i]) || (n > max[i]))
            goto err;
        if (tm) {
            switch (i) {
            case 0:
                tm->tm_year = n < 50 ? n + 100 : n;
                break;
            case 1:
                tm->tm_mon = n - 1;
                break;
            case 2:
                tm->tm_mday = n;
                break;
            case 3:
                tm->tm_hour = n;
                break;
            case 4:
                tm->tm_min = n;
                break;
            case 5:
                tm->tm_sec = n;
                break;
            }
        }
    }
    if (a[o] == 'Z')
        o++;
    else if ((a[o] == '+') || (a[o] == '-')) {
        int offsign = a[o] == '-' ? 1 : -1, offset = 0;
        o++;
        if (o + 4 > l)
            goto err;
        for (i = 6; i < 8; i++) {
            if ((a[o] < '0') || (a[o] > '9'))
                goto err;
            n = a[o] - '0';
            o++;
            if ((a[o] < '0') || (a[o] > '9'))
                goto err;
            n = (n * 10) + a[o] - '0';
            if ((n < min[i]) || (n > max[i]))
                goto err;
            if (tm) {
                if (i == 6)
                    offset = n * 3600;
                else if (i == 7)
                    offset += n * 60;
            }
            o++;
        }
        if (offset && !OPENSSL_gmtime_adj(tm, 0, offset * offsign))
            return 0;
    }
    return o == l;
 err:
    return 0;
}