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分析工具: softice , OD
我的操作系统: win 2000 sp4 , win 98
分析对象: QQ2005贺岁版 珊瑚虫外挂
为了方便分析,我先把CoralQQ.dll和coralqq.exe先脱壳,这两个文件加的都是超弱壳,脱壳过程不在这里多说.
由于win nt 平台和win9x 的差异,珊瑚虫外挂因系统的不同而分开两种工作原理.
我们都知道,珊瑚外挂是给QQ的主程序QQ.exe外挂了一个Coralqq.dll,而完成这个工作的就是coralqq.exe .要加载一个dll文件必须是qq.exe自己的某个线程执行LoadLibraryA,并且以coralqq.dll为参数,但qq.exe本来根本没有这样的一段代码,怎么办?答案很简单,既然它没有,那就让我们帮它加上去,coralqq.exe就是利用WriteProcessMemory帮QQ.exe加上了这样一段代码,并且改变程序流程,让qq.exe先加载coralqq.dll再跳到原来的oep执行.
想了一下,比较合理的方法有:
1.在nt内核的系统上,利用远程线程的方法,首先用CreateProcess创建QQ.exe的进程,同时创建了主线程,再用VirtualAllocEx在qq.exe中申请一块内存,然后把我们的代码写进去,最后用CreateRemoteThread在qq的进程中创建另外一个线程,其开始执行的地方正是我们自己加入的代码首地址.
2.先用CreateProcess创建QQ进程和主线程,在QQ的内存空间中找个合理的地方写入我们的代码,然后修改某个地方(例如OEP)使QQ先跳去执行我们写入的代码,加载coralqq.dll,修复原来改过的oep,然后跳回oep让程序正常执行.
下面就让我们分析一下珊瑚虫的外挂是怎样做到的,首先分析nt平台上的运行过程.
用OD载入脱壳后的coralqq.exe,停在下面:
00418E2C >/$ 55 push ebp
00418E2D . 8BEC mov ebp,esp
00418E2F . 83C4 F0 add esp,-10
00418E32 . B8 648D4100 mov eax,CoralQQ.00418D64
00418E37 . E8 A4BAFEFF call CoralQQ.004048E0
00418E3C . A1 F49D4100 mov eax,dword ptr ds:[419DF4]
00418E41 . 33D2 xor edx,edx
00418E43 . E8 30F4FFFF call CoralQQ.00418278
00418E48 . A1 F49D4100 mov eax,dword ptr ds:[419DF4]
00418E4D . 8B00 mov eax,dword ptr ds:[eax]
00418E4F . 83C0 18 add eax,18
00418E52 . E8 F9C6FEFF call CoralQQ.00405550
00418E57 . E8 08A9FEFF call CoralQQ.00403764
然后下断点: bp CreateRemoteThread ,然后运行,结果发现,OD根本没有断下,证明珊瑚虫的外挂没有使用远程线程的方法,难道它是用了第二种方法?我们再验证一下:首先在OD中bp CreateProcess,断下,反回后,用winhex打开QQ.exe的内存,把QQ.exe的OEP处改为CC,接着在softice中 bpint 3 ,在OD中按F9运行,接着就是中断在softice中,把oep(464b58)处还原,在再softice下 bpm 464b58 ,然后结束程序,再运行coralqq.exe发现自始至终那个bpm断点还是没有断下,证明珊瑚虫外挂在2000下也没有修改QQ.exe的oep来改变程序流程,晕.没办法,只好在OD中下WriteProcessMemory断点,看看它究竟修改了哪里.
00231012 57 push edi
00231013 8B4424 24 mov eax,dword ptr ss:[esp+24]
00231017 A3 70302300 mov dword ptr ds:[233070],eax
0023101C 8305 70302300 04 add dword ptr ds:[233070],4
00231023 E8 5C000000 call ;创建QQ的进程
上面创建后的QQ主线程是暂停的,不会马上执行,在win9x下也是这样.
第一次中断时堆栈显示:
0012EBDC 0040C75C /CALL 到 WriteProcessMemory 来自 CoralQQ.0040C756
0012EBE0 00000018 hProcess = 00000018
0012EBE4 5F000000 Address = 5F000000
0012EBE8 00CC0F44 Buffer = 00CC0F44
0012EBEC 000000D2 BytesToWrite = D2 (210.)
0012EBF0 0012EC68 \pBytesWritten = 0012EC68
第二次:
0012EC70 00416231 /CALL 到 WriteProcessMemory 来自 CoralQQ.0041622C
0012EC74 00000018 hProcess = 00000018
0012EC78 5F010000 Address = 5F010000
0012EC7C 0012EE9F Buffer = 0012EE9F
0012EC80 00000025 BytesToWrite = 25 (37.)
0012EC84 0012EFD0 \pBytesWritten = 0012EFD0
第三次:
0012EC70 004162CB /CALL 到 WriteProcessMemory 来自 CoralQQ.004162C6
0012EC74 00000018 hProcess = 00000018
0012EC78 77F84BC0 Address = 77F84BC0
0012EC7C 0012EFC3 Buffer = 0012EFC3
0012EC80 00000005 BytesToWrite = 5
0012EC84 0012EFD0 \pBytesWritten = 0012EFD0
第四次:
0012EC70 0041632B /CALL 到 WriteProcessMemory 来自 CoralQQ.00416326
0012EC74 00000018 hProcess = 00000018
0012EC78 5F010025 Address = 5F010025
0012EC7C 0012EC96 Buffer = 0012EC96
0012EC80 00000208 BytesToWrite = 208 (520.)
0012EC84 0012EFD0 \pBytesWritten = 0012EFD0
第五次:
0012EC70 0041634B /CALL 到 WriteProcessMemory 来自 CoralQQ.00416346
0012EC74 00000018 hProcess = 00000018
0012EC78 5F010000 Address = 5F010000
0012EC7C 0012EE9F Buffer = 0012EE9F
0012EC80 00000025 BytesToWrite = 25 (37.)
0012EC84 0012EFD0 \pBytesWritten = 0012EFD0
留意第三次中断: 77F84BC0 对应着: NtTestAlert 所在库：ntdll.dll
程序每次执行前都要经过 ntdll.dll 的 NtTestAlert函数,它使函数首句跳到某个
地方,从而改变程序流程.
00417E7E 8B45 F4 mov eax,dword ptr ss:[ebp-C]
00417E81 50 push eax
00417E82 E8 DDCDFEFF call ;使得QQ的主线程继续执行
把 0012efc3 处的E9改为CC,再在softice中bpint 3 ,让其中断后跟踪:
001B:77F84BC0 E93BB408E7 JMP 5F010000
单步执行跟踪
001B:5F010000 B80000015F MOV EAX,5F010000
001B:5F010005 B90000005F MOV ECX,5F000000
001B:5F01000A FFD1 CALL ECX
此时ecx的值为5F000000
001B:5F000000 55 PUSH EBP
001B:5F000001 8BEC MOV EBP,ESP
001B:5F000003 83C4EC ADD ESP,-14
001B:5F000006 53 PUSH EBX
001B:5F000007 56 PUSH ESI
001B:5F000008 8BD8 MOV EBX,EAX
001B:5F00000A 896DFC MOV [EBP-04],EBP
001B:5F00000D 8B431C MOV EAX,[EBX+1C]
001B:5F000010 8B55FC MOV EDX,[EBP-04]
001B:5F000013 83C204 ADD EDX,04
001B:5F000016 8902 MOV [EDX],EAX
001B:5F000018 8B431C MOV EAX,[EBX+1C]
001B:5F00001B 8945EC MOV [EBP-14],EAX
001B:5F00001E C745FC05000000 MOV DWORD PTR [EBP-04],00000005
001B:5F000025 8D45F8 LEA EAX,[EBP-08]
001B:5F000028 50 PUSH EAX
001B:5F000029 6A40 PUSH 40
001B:5F00002B 8D45FC LEA EAX,[EBP-04]
001B:5F00002E 50 PUSH EAX
001B:5F00002F 8D45EC LEA EAX,[EBP-14]
001B:5F000032 50 PUSH EAX
001B:5F000033 6AFF PUSH FF
001B:5F000035 FF15C600005F CALL [5F0000C6]
001B:5F00003B 8B431C MOV EAX,[EBX+1C]
001B:5F00003E 8B5320 MOV EDX,[EBX+20]
001B:5F000041 8910 MOV [EAX],EDX ;恢复Ntdll.NtTestAlert入口处
001B:5F000043 8A5324 MOV DL,[EBX+24]
001B:5F000046 885004 MOV [EAX+04],DL
001B:5F000049 C745FC05000000 MOV DWORD PTR [EBP-04],00000005
001B:5F000050 8D45F8 LEA EAX,[EBP-08]
001B:5F000053 50 PUSH EAX
001B:5F000054 8B45F8 MOV EAX,[EBP-08]
001B:5F000057 50 PUSH EAX
001B:5F000058 8D45FC LEA EAX,[EBP-04]
001B:5F00005B 50 PUSH EAX
001B:5F00005C 8D45EC LEA EAX,[EBP-14]
001B:5F00005F 50 PUSH EAX
001B:5F000060 6AFF PUSH FF
001B:5F000062 FF15CA00005F CALL [5F0000CA]
001B:5F000068 8B7318 MOV ESI,[EBX+18]
001B:5F00006B 4E DEC ESI
001B:5F00006C 85F6 TEST ESI,ESI
001B:5F00006E 7C4C JL 5F0000BC
001B:5F000070 46 INC ESI
001B:5F000071 8D4325 LEA EAX,[EBX+25]
001B:5F000074 8BD8 MOV EBX,EAX
001B:5F000076 33D2 XOR EDX,EDX
001B:5F000078 8BC3 MOV EAX,EBX
001B:5F00007A 66833800 CMP WORD PTR [EAX],00
001B:5F00007E 740C JZ 5F00008C
001B:5F000080 42 INC EDX
001B:5F000081 83C002 ADD EAX,02
001B:5F000084 81FA03010000 CMP EDX,00000103
001B:5F00008A 75EE JNZ 5F00007A
001B:5F00008C 8BC2 MOV EAX,EDX
001B:5F00008E 03C0 ADD EAX,EAX
001B:5F000090 668945F0 MOV [EBP-10],AX
001B:5F000094 6683C002 ADD AX,02
001B:5F000098 668945F2 MOV [EBP-0E],AX
001B:5F00009C 8BC3 MOV EAX,EBX
001B:5F00009E 8945F4 MOV [EBP-0C],EAX
001B:5F0000A1 8D45FC LEA EAX,[EBP-04]
001B:5F0000A4 50 PUSH EAX
001B:5F0000A5 8D45F0 LEA EAX,[EBP-10]
001B:5F0000A8 50 PUSH EAX
001B:5F0000A9 6A00 PUSH 00
001B:5F0000AB 6A00 PUSH 00
001B:5F0000AD FF15CE00005F CALL [5F0000CE] ;call LoadLibraryA
001B:5F0000B3 81C308020000 ADD EBX,00000208
001B:5F0000B9 4E DEC ESI
001B:5F0000BA 75BA JNZ 5F000076
001B:5F0000BC 5E POP ESI
001B:5F0000BD 5B POP EBX
001B:5F0000BE 8BE5 MOV ESP,EBP
001B:5F0000C0 5D POP EBP
001B:5F0000C1 C3 RET
001B:5F0000C2 0000 ADD [EAX],AL
001B:5F0000C4 0000 ADD [EAX],AL
001B:5F0000C6 C4BFF877C4BF LES EDI,[EDI+BFC477F8]
001B:5F0000CC F8 CLC
001B:5F0000CD 7761 JA 5F000130
001B:5F0000CF 32F8 XOR BH,AL
001B:5F0000D1 7700 JA 5F0000D3
我们再分析一下win9x下珊瑚虫的外挂又是怎样运行的.
再次用OD载入Coralqq.exe
00415C9D mov dword ptr ss:[ebp-C],ecx
00415CA0 mov dword ptr ss:[ebp-4],edx
00415CA3 mov dword ptr ss:[ebp-8],eax
00415CA6 xor ebx,ebx
00415CA8 call ;判断操作系统
00415CAD test eax,80000000
00415CB2 je short CORALQQ.00415CFE
00415CB4 xor edi,edi
00415CB6 xor esi,esi
00415CB8 jmp short CORALQQ.00415CE7
00415CBA /cmp esi,dword ptr ss:[ebp-24]
00415CBD je short CORALQQ.00415CE2
00415CBF mov eax,dword ptr ss:[ebp-4]
00415CC2 mov edx,dword ptr ss:[ebp-24]
00415CC5 mov dword ptr ds:[eax],edx
00415CC7 cmp dword ptr ss:[ebp-18],1000
00415CCE jnz short CORALQQ.00415CDF
00415CD0 push ebp ; /Arg1
00415CD1 call CORALQQ.00415BD4 ; \CoralQQ.00415BD4
00415CD6 pop ecx
00415CD7 test al,al
00415CD9 je short CORALQQ.00415CDF
00415CDB mov bl,1
00415CDD jmp short CORALQQ.00415D29
00415CDF mov esi,dword ptr ss:[ebp-24]
00415CE2 mov eax,dword ptr ss:[ebp-1C]
00415CE5 add edi,eax
00415CE7 push 1C ; /BufSize = 1C (28.)
00415CE9 lea eax,dword ptr ss:[ebp-28] ;
00415CEC push eax ; Buffer
00415CED push edi ; Address
00415CEE mov eax,dword ptr ss:[ebp-8] ;
00415CF1 push eax ; hProcess
00415CF2 call ; \VirtualQueryEx 获得内存业面信息
00415CF7 cmp eax,1C
00415CFA \je short CORALQQ.00415CBA
00415CFC jmp short CORALQQ.00415D29
上面的代码是判断操作系统的版本,如果是win9x的话就先跳到415ce7,
00415A4B > \8>lea eax,dword ptr ss:[ebp-8]
00415A4E . 5>push eax ; /pBytesWritten
00415A4F . 5>push edi ; BytesToWrite
00415A50 . 8>mov eax,dword ptr ss:[ebp-4] ;
00415A53 . 5>push eax ; Buffer
00415A54 . 5>push esi ; Address
00415A55 . 5>push ebx ; hProcess
00415A56 . E>call ; \WriteProcessMemory
看一下此时的堆栈:
0067EA5C 0000000C hProcess = 0000000C
0067EA60 83138AAC Address = 83138AAC
0067EA64 0067EABC Buffer = 0067EABC
0067EA68 00000292 BytesToWrite = 292 (658.)
0067EA6C 0067EA7C \pBytesWritten = 0067EA7C
它把缓冲区 0067eabc的658的字节写进QQ.exe的内存 83138aac处,在win98下,进程内存中的共享(M
MF)分区是0x80000000~0xbfffffff,所有的内存映射文件和系统共享DLL将加载在这个地址,而
那些映射文件和系统共享DLL往往都在比较高的地址,所以说,从80000000地址对上的一大段地址空间
往往是比较"空闲"的,当然,并不是说这些地址就可以乱读乱写,至于这个83138aac的地址值具体是怎样计算出来的,
我还没有分析清楚,但我想到另外一种可行的方法,而且经过我自己编程证实,那就是以1000h大小为单位,从80000000
开始用WriteProcessMemory一直往上写数据,直到写入成功,证明那段1000h的地址可用,而且1000h
大小的内存空间已经够我们放代码的了,之所以用1000h为单位大小,是因为考虑到块对齐.
继续跟踪:
00415A39 . 8D45 F8 lea eax,dword ptr ss:[ebp-8]
00415A3C . 50 push eax ; /pOldProtect
00415A3D . 6A 40 push 40 ; NewProtect = PAGE_EXECUTE_READWRITE
00415A3F . 57 push edi ; Size
00415A40 . 56 push esi ; Address
00415A41 . 53 push ebx ; hProcess
00415A42 . E8 85F2FEFF call ; \VirtualProtectEx
上面的代码是改变QQ.exe的oep处的属性,使其可读可写可执行,为改写oep处的代码做准备
接着,又一次中断在WriteProcessMemory
看看堆栈:
0067EA5C 0000000C hProcess = 0000000C
0067EA60 00464B58 Address = 464B58
0067EA64 0067EE46 Buffer = 0067EE46
0067EA68 00000005 BytesToWrite = 5
0067EA6C 0067EA7C \pBytesWritten = 0067EA7C
464b58就是QQ.exe的OEP,很明显,它要改变oep来改变程序流程!!
好了,我们又用那套方法,把0067eea6的第一个字节改为cc,在softice中bpint 3,然后中断,再
跟踪.
在softice下中断后:
0167:00464B58 E91328CE82 JMP 83147370
0167:83147370 C705584B4600558BEC6AMOV DWORD PTR [00464B58],6AEC8B55 ;马上恢复oep处的代码
0167:8314737A C6055C4B4600FF MOV BYTE PTR [00464B5C],FF
0167:83147381 68FA731483 PUSH 831473FA
0167:83147386 6838000000 PUSH 00000038
0167:8314738B 6A40 PUSH 40
0167:8314738D FF15F6731483 CALL [KERNEL32!GlobalAlloc] ;再申请内存
0167:83147393 C700B85077F7 MOV DWORD PTR [EAX],F77750B8 ;从这里开始一直填入新数据
0167:83147399 C74004BFFFD068 MOV DWORD PTR [EAX+04],68D0FFBF
0167:831473A0 C7400870731483 MOV DWORD PTR [EAX+08],83147370
0167:831473A7 C7400CB89348E9 MOV DWORD PTR [EAX+0C],E94893B8
0167:831473AE C74010BFFFD0B8 MOV DWORD PTR [EAX+10],B8D0FFBF
0167:831473B5 C74014584B4600 MOV DWORD PTR [EAX+14],00464B58
0167:831473BC C74018FFE0C705 MOV DWORD PTR [EAX+18],05C7E0FF
0167:831473C3 C7401C584B4600 MOV DWORD PTR [EAX+1C],00464B58
0167:831473CA C74020558BEC6A MOV DWORD PTR [EAX+20],6AEC8B55
0167:831473D1 C74024C6055C4B MOV DWORD PTR [EAX+24],4B5C05C6
0167:831473D8 C740284600FF68 MOV DWORD PTR [EAX+28],68FF0046
0167:831473DF C7402CFA731483 MOV DWORD PTR [EAX+2C],831473FA
0167:831473E6 C7403068380000 MOV DWORD PTR [EAX+30],00003868
0167:831473ED C74034006A40FF MOV DWORD PTR [EAX+34],FF406A00
0167:831473F4 FFE0 JMP EAX ;此时eax为 0063059C
0167:0063059C B85077F7BF MOV EAX,KERNEL32!LoadLibraryA;加载Coralqq.dll
0167:006305A1 FFD0 CALL EAX
0167:006305A3 6870731483 PUSH 83147370
0167:006305A8 B89348E9BF MOV EAX,COMCTL32!ORD_0049
0167:006305AD FFD0 CALL EAX
0167:006305AF B8584B4600 MOV EAX,00464B58
0167:006305B4 FFE0 JMP EAX ;跳回QQ.exe的入口点
分析完毕.
到了这里,我们可以总结一下了,在win2000/xp下coralqq.exe先创建QQ的进程,同时也就创建了
QQ的暂停的主线程,接着往QQ进程的内存写入代码,修改Ntdll.NtTestAlert的代码跳让程序跳到自己的
代码处执行,在执行的过程中恢复Ntdll.NtTestAlert处被改了的代码,同时加载Coralqq.dll.
在win9x下,coralqq.exe先创建QQ的进程,同时也就创建了QQ的暂停的主线程,接着往QQ.exe的内存
写数据,改写QQ.exe的oep从而达到改变程序流程的目的,让其先执行加入了的代码,加载Coralqq.dll,
加载完后再跳到原来的QQ.exe的oep继续执行.
其实在win2000/xp下面完全可以用远程线程的方法来实现加载dll文件,我后来自己编程实现了外挂
这一步.
也许有读者读完这编文章后会问:"加载了coralqq.dll又有什么用?它是怎样显IP的?"
其实,要显IP当然要修改QQ的内存中的代码,而修改内存代码这一步是在加载coralqq.dll的时候由
coralqq.dll完成的.也就是说,在执行LoadLibrary的过程中系统会执行corall.dll的 LibMain ,修改
的过程就在LibMain中完成了!而说到显IP的原理,抱歉,不在我们这编文章的讨论范围之内,我们只是讨论
外挂中"挂"这一步.
下面是我写的代码,可以做出一个顶替Coralqq.exe的程序,但原理上和Coralqq.exe有一点点不同
.586
.model flat, stdcall
option casemap :none ; case sensitive
include windows.inc
include kernel32.inc
includelib kernel32.lib
.data
qq db ".\QQ.exe",0
ikeyname db "qq",0
isecname db "main",0
szBuffer dw 50 dup(0)
dllname db ".\CoralQQ.dll",0
szkernel32 db "Kernel32.dll",0
dllin dd 0
szloadlibrary db "LoadLibraryA",0
oaddr dd 0
wriaddr dd 0
ininame db ".\CoralQQ.ini",0
.data?
align dword
con CONTEXT <>
align dword
con2 CONTEXT <>
stStartUp STARTUPINFO
stProcInfo PROCESS_INFORMATION
.code
start:
main proc
local wrisize:dword ;用来存放要写入的代码的大小
local num:dword
local oldpro:dword
local lastwri:dword
local wribase:dword ;用来存放写入代码的基址
invoke GetPrivateProfileString,offset isecname,offset ikeyname,\
offset szloadlibrary,offset szBuffer,\
sizeof szBuffer,offset ininame ;从Coralqq.ini中获取QQ程序的路径
invoke GetModuleHandle,offset szkernel32
invoke GetProcAddress,eax,offset szloadlibrary
mov dllin,eax
invoke GetStartupInfo,addr stStartUp
invoke CreateProcess,NULL,offset szBuffer,NULL,NULL,FALSE,\
CREATE_SUSPENDED,NULL,NULL,addr stStartUp,addr stProcInfo ;创建QQ进程
cmp eax,0
jz exit
invoke GetVersion
test eax,080000000h ;判断操作系统类型
jnz win9x
invoke VirtualAllocEx,stProcInfo.hProcess,NULL,01000h,MEM_COMMIT,\
PAGE_EXECUTE_READWRITE ;在QQ内存中分配空间
mov oaddr,eax
invoke WriteProcessMemory,stProcInfo.hProcess,oaddr,offset dllname,\
sizeof dllname,addr num ;写入数据
invoke CreateRemoteThread,stProcInfo.hProcess,NULL,0,dllin,oaddr,0,\
addr num ;创建远程线程
invoke CloseHandle,eax
invoke ResumeThread,stProcInfo.hThread ;让QQ继续运行
invoke ExitProcess,0
ret
win9x:
mov wribase,oepwrite
mov wrisize,codeend-oepwrite
invoke VirtualProtect,wribase,wrisize,\
PAGE_EXECUTE_READWRITE,addr oldpro ;改变这个程序的要写入代码的地方的属性,其实可以在编译时加上开关
mov wrisize,codeend-codewrite
mov wriaddr,080000000h
sub wriaddr,1000h
again:
add wriaddr,1000h
mov wribase,codewrite
invoke WriteProcessMemory,stProcInfo.hProcess,wriaddr,\
wribase,wrisize,addr num ;写入代码
mov eax,wrisize
cmp eax,num
jnz again
mov eax,wriaddr
mov ebx,chan0-4
mov [ebx],eax
invoke VirtualProtectEx,stProcInfo.hProcess,0464b58h,7,\
PAGE_EXECUTE_READWRITE,addr oldpro ;改变QQ.exe的oep处的属性
mov wribase,oepwrite
invoke WriteProcessMemory,stProcInfo.hProcess,0464b58h, wribase,7,\
addr num ;写入数据
mov eax,dllin
mov ebx,chan2-4
mov [ebx],eax
mov eax,codeend-codewrite
add eax,wriaddr
mov ebx,chan1-4
mov [ebx],eax
mov wribase,codewrite
mov wrisize,codeend-codewrite
invoke WriteProcessMemory,stProcInfo.hProcess,wriaddr,\
wribase,wrisize,addr num
mov eax,codeend-codewrite
add eax,wriaddr
mov lastwri,eax
invoke WriteProcessMemory,stProcInfo.hProcess,lastwri,offset dllname,\
sizeof dllname,addr num
invoke ResumeThread,stProcInfo.hThread ;让QQ继续执行
exit:
invoke ExitProcess,0
ret
main endp
;下面的都是要写入到QQ.exe的内存的附加代码,但有些数值在写入前要实时修正
oepwrite:
mov eax,0
chan0: jmp eax
codewrite:
mov eax,0464b58h
push 6aec8b55h
pop [eax]
mov eax,0464b5ch
push 101868ffh
pop [eax]
push 080000000
chan1:
push 464b58h
mov eax,0
chan2:
jmp eax
codeend:
end start
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