pbkdf2_hmac_sha1

static VALUE
ossl_pkcs5_pbkdf2_hmac_sha1(VALUE self, VALUE pass, VALUE salt, VALUE iter, VALUE keylen)
{
    VALUE str;
    int len = NUM2INT(keylen);

    StringValue(pass);
    StringValue(salt);

    str = rb_str_new(0, len);

    if (PKCS5_PBKDF2_HMAC_SHA1(RSTRING_PTR(pass), RSTRING_LENINT(pass),
                               (const unsigned char *)RSTRING_PTR(salt), RSTRING_LENINT(salt), NUM2INT(iter),
                               len, (unsigned char *)RSTRING_PTR(str)) != 1)
        ossl_raise(ePKCS5, "PKCS5_PBKDF2_HMAC_SHA1");

    return str;
}