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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**](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/SQL%20Injection/PostgreSQL%20Injection.md)
**`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 this example**](dblink-lo\_import-data-exfiltration.md) 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`.
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:
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):
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" %}
```sql
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
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_):
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