/Reverse-Engineering-Arsenal

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$$
$$ Author: Javier Vicente Vallejo
$$ Twitter: @vallejocc
$$ Web: http://www.vallejo.cc
$$
$$ $$>a<dump_injected_pe_rwemem_fast.wdbg <destination directory>
$$
$$ This windbg script will walk the results of !address command for each process in the debuggee machine,
$$ searching for RWE memory containing PE files (based on the analysis of PE header).
$$
$$ When a PE file in RWE memory is found, the script will dump it. In addition to dump it, it will fix
$$ some fields of PE header: imagebase will be set to the address where the PE is loaded, and
$$ section[i].PointerToRawData = section[i].VirtualAddress (because we are dumping a mapped PE to disk and,
$$ if we want to analyze the dumped PE with a disassembler for example, we need to fix the sections).
$$
$$ The difference with the script dump_injected_pe_rwemem.wdbg (the non fast version) it is this script is
$$ not paging-in each page before trying to dump a PE file. Usually pages will be there, but it could fail
$$ to dump the entire file if a page is not mapped.
$$
$$ Anyway, for debugging, i recommend to disable swapping, for having pages always in memory.
$$
$$.sympath SRV*c:\symcache*http://msdl.microsoft.com/download/symbols
$$.reload
.logopen ${$arg1}\dump_injected_pe_rwemem_fast.start
.printf "start"
.logclose
aS stage @$t19
aS temp @$t18
aS temp2 @$t17
aS temp3 @$t16
aS isPossiblePE @$t15
aS isDosMessageBased @$t14
aS pe @$t13
aS fileheader @$t12
aS optionalheader @$t11
aS sections @$t10
aS nsections @$t9
aS lastsect @$t8
aS prev1 @$t7
aS prev2 @$t6
aS baseaddr @$t5
aS baseaddrlen @$t4
.block
{
.sympath "SRV*c:\symcache*http://msdl.microsoft.com/download/symbols";
.reload
}
.block
{
r stage = 2
.printf "xxxx"
.foreach (processes_tok { !process 0 0 })
{
.if($scmp("${processes_tok}","PROCESS")==0)
{
.if(${stage}==2)
{
$$stage==2 is used to skip the first apparition of PROCESS string in the results of !process 0 0
r stage = 0
}
.else
{
r stage = 1
}
}
.elsif(${stage}==1)
{
.printf /D "<b>Analyzing process ${processes_tok}</b>\n"
r stage = 0
.process /p /r ${processes_tok}
$$search for memory blocks with ReadWriteExecute protection
$$careful:
$$ when the baseaddress is over 0x10000000 findstr tokens will be:
$$ 93:7640:20010000
$$ 2002c000
$$ 1c000
$$ UserRange
$$ ...
$$ however if the addess is under 0x10000000:
$$ 25:1364:
$$ 60000
$$ 61000
$$ 1000
$$ UserRange
$$ The reason for this its windbg puts spaces before the base address when it hasnt 8 characters to complete 8 characters, but if the address is
$$ ???????? then it doesnt put spaces. We need to have in mind both case, and this is the reason of the stages of the next code
$$
.foreach (tok { .shell -ci "!address" findstr /N /O /R /C:"UserRange.*ExecuteReadWrite" /C:"UserRange.*ReadWriteExecute" })
{
r isPossiblePE = 0
r isDosMessageBased = 0
.printf "${tok}\n"
.if($spat("${tok}","*:*:*")!=0)
{
r stage = 1
}
.elsif(${stage}==1)
{
r prev1 = ${tok}
r stage = 2
}
.elsif(${stage}==2)
{
r prev2 = ${tok}
r stage = 3
}
.elsif(${stage}==3)
{
.if($spat("${tok}","*UserRange*")!=0)
{
r baseaddr = prev1 - prev2
r baseaddrlen = prev2
r stage = 5
}
.else
{
r baseaddr = prev1
r baseaddrlen = ${tok}
r stage = 4
}
}
.elsif(${stage}==4)
{
r stage = 5
}
.elsif(${stage}==5)
{
$$for each block with ReadWriteExecute protection, check MZ / PE
r @$t0 = baseaddr
.if(@$t0!=0)
{
.printf "base %x\n", @$t0
$$.pagein /p ${processes_tok} @$t0
$$g
$$!address @$t0
.if($vvalid(@$t0, 2)==1)
{
.printf "valid base address\n"
.printf "PE_header %x\n", @$t0+@@c++(((nt!_IMAGE_DOS_HEADER * )@$t0)->e_lfanew)
.if($vvalid(@$t0+@@c++(((nt!_IMAGE_DOS_HEADER * )@$t0)->e_lfanew), 2)==1)
{
.printf "valid PE_header address\n"
.if(wo(@$t0)==0x5a4d & dwo(@$t0+@@c++(((nt!_IMAGE_DOS_HEADER * )@$t0)->e_lfanew))==0x454E)
{
$$We can find MZ / NE images, we ignore them
}
.elsif(wo(@$t0)==0x5a4d & dwo(@$t0+@@c++(((nt!_IMAGE_DOS_HEADER * )@$t0)->e_lfanew))==0x4550)
{
$$if MZ and PE signatures, valid pe header
.printf "valid PE_header\n"
r isPossiblePE = 1
}
.else
{
$$if not MZ or not PE signature, but msdos message is found, its a possible pe header
r temp = 0
.foreach (tok2 { s -a @$t0 L 0x80 "This program cannot " })
{
r temp = 1
}
.if(${temp}==1)
{
.printf "possible pe header\n"
r isPossiblePE = 1
r isDosMessageBased = 1
}
}
}
.else
{
.printf "not valid PE_header address\n"
}
}
.else
{
.printf "not valid base address\n"
}
$$if we have found a possible PE in a memory zone with ReadWriteExecute protection, we will check if the base address is in the list of loaded module
.if(${isPossiblePE}==1)
{
.printf "is possible module %x\n", @$t0
$$ r temp = 0
$$ $$search for valid from "is not valid address"
$$ .foreach (tok3 { .shell -ci "!lmi @$t0" findstr /N /O "valid.address" })
$$ {
$$ r temp = ${temp} + 1
$$ }
$$ .printf "%x\n", ${temp}
$$
$$ We are going to disable !lmi check. I have found malware that is unmapping
$$ the main module of a executable when it does process hollowing, and it loads
$$ its injected PE in that address. In this cases, !lmi is not answering not valid
$$ address for that address. However !address command is containing the path
$$ of the module (for example Section [\Windows\explorer.exe]) when the module is
$$ a valid loaded module, and it wont contain the path when it is an injected module
$$ in RWE mem. So, we will skip !lmi check, and we will check !address results
$$ vvvvvvvv DISABLE !LMI CHECK vvvvvvvvv
r temp = 4
$$ ^^^^^^^^ DISABLE !LMI CHECK ^^^^^^^^^
$$ "is not valid address" was found
.if(${temp} > 3)
{
$$ there are some modules that !lmi command is answering: is not valid address, however they seems to be valid loaded modules (not interesing for us).
$$ However if we consults information about the address with !address we find things as:
$$ Memory Usage: Section [\WINDOWS\System32\blablabla.mui] (it happens usually with .mui files, but not only with them
$$ We will discard results of !address with .dll], .mui] and .exe]
r temp = 0
.foreach (tok4 { .shell -ci "!address @$t0" findstr /N /O /R /I "\.mui\]" })
{
r temp = ${temp} + 1
}
r temp2 = 0
.foreach (tok5 { .shell -ci "!address @$t0" findstr /N /O /R /I "\.dll\]" })
{
r temp2 = ${temp2} + 1
}
r temp3 = 0
.foreach (tok6 { .shell -ci "!address @$t0" findstr /N /O /R /I "\.exe\]" })
{
r temp3 = ${temp3} + 1
}
.printf "search !address .mui %x\n", ${temp}
.printf "search !address .dll %x\n", ${temp2}
.printf "search !address .exe %x\n", ${temp3}
.if(${temp} < 4 and ${temp2} < 4 and ${temp3} < 4)
{
.if(${isDosMessageBased}==0)
{
.printf /D "<b>---------------------------------------------------------------------------</b>\n"
.printf /D "<b>Process: ${processes_tok} base: %x -> Possible injected or unpacked PE</b>\n", @$t0
.printf /D "<b>---------------------------------------------------------------------------</b>\n"
}
.else
{
.printf /D "-------------------------------------------------------------------------------------------------------------------------------------\n"
.printf /D "Process: ${processes_tok} base: %x -> Possible injected or unpacked PE, based on the dos header message: This program cannot...\n", @$t0
.printf /D "--------------------------------------------------------------------------------------------------------------------------------------\n"
}
.printf "xxxx1\n"
r pe = @$t0 + poi(@$t0 + @@(#FIELD_OFFSET(nt!_IMAGE_DOS_HEADER, e_lfanew)))
.printf "xxxx2 %x\n", ${pe}
r fileheader = ${pe} + @@(#FIELD_OFFSET(nt!_IMAGE_NT_HEADERS, FileHeader))
.printf "xxxx3 %x\n", ${fileheader}
r optionalheader = ${pe} + @@(#FIELD_OFFSET(nt!_IMAGE_NT_HEADERS, OptionalHeader))
.printf "xxxx4 %x\n", ${optionalheader}
r nsections = poi(${fileheader} + @@(#FIELD_OFFSET(nt!_IMAGE_FILE_HEADER, NumberOfSections )))&0xffff
.printf "xxxx5 %x\n", ${nsections}
r sections = ${pe} + @@c++(sizeof(nt!_IMAGE_NT_HEADERS))
.printf "xxxx6 %x\n", ${sections}
$$ reach the end of the PE file (last section rva + last section vsize)
r lastsect = ${sections} + ( ${nsections} - 1 ) * @@c++(sizeof(nt!_IMAGE_SECTION_HEADER))
r @$t1 = @$t0 + @@c++( ( ( nt!_IMAGE_SECTION_HEADER * ) ${lastsect} )->VirtualAddress ) + @@c++( ( ( nt!_IMAGE_SECTION_HEADER * ) ${lastsect} )->Misc.VirtualSize )
r @$t2 = @$t0 + @@c++( ( ( nt!_IMAGE_SECTION_HEADER * ) ${lastsect} )->VirtualAddress ) + @@c++( ( ( nt!_IMAGE_SECTION_HEADER * ) ${lastsect} )->SizeOfRawData )
r @$t3 = @$t0
.if (@$t2 > @$t1) { r @$t1 = @$t2 }
$$limit to dump = 0x100000 bytes
.if (@$t1-@$t0 > 0x100000)
{
r @$t1 = @$t0+0x100000
}
.printf "xxxx7"
$$ before dumping the PE, we are going to modify sections' raw offset = virtual address for coherency in the dumped PE when we analyze it with IDA or any other tool
r $t2 = ${sections}
r lastsect = ${sections} + ( ${nsections} ) * @@c++(sizeof(nt!_IMAGE_SECTION_HEADER))
.while (@$t2 < ${lastsect})
{
ed (@$t2+@@( #FIELD_OFFSET(nt!_IMAGE_SECTION_HEADER, PointerToRawData))) @@c++((( nt!_IMAGE_SECTION_HEADER *)@$t2)->VirtualAddress)
.if( @@c++((( nt!_IMAGE_SECTION_HEADER *)@$t2)->SizeOfRawData) < @@c++((( nt!_IMAGE_SECTION_HEADER *)@$t2)->Misc.VirtualSize))
{
ed (@$t2+@@( #FIELD_OFFSET(nt!_IMAGE_SECTION_HEADER, SizeOfRawData))) @@c++((( nt!_IMAGE_SECTION_HEADER *)@$t2)->Misc.VirtualSize)
}
.else
{
ed (@$t2+@@( #FIELD_OFFSET(nt!_IMAGE_SECTION_HEADER, Misc))) @@c++((( nt!_IMAGE_SECTION_HEADER *)@$t2)->SizeOfRawData)
}
r $t2 = @$t2 + @@c++(sizeof(nt!_IMAGE_SECTION_HEADER))
}
$$update sizeofimage
.block
{
ed (${optionalheader} + @@(#FIELD_OFFSET(nt!_IMAGE_OPTIONAL_HEADER, SizeOfImage))) (@$t1-@$t0)&0x7fffffff
}
.printf "xxxx8"
$$update imagebase
.block
{
ed (${optionalheader} + @@(#FIELD_OFFSET(nt!_IMAGE_OPTIONAL_HEADER, ImageBase))) ${baseaddr}
}
.printf "xxxx9"
.printf "dumping file address start %x end %x", @$t0, @$t1
.foreach /pS 4 (baseaddr_tok { ? baseaddr })
{
.foreach /pS 4 (baseaddrlen_tok { ? baseaddrlen })
{
.printf "${processes_tok}_${baseaddr_tok}_${baseaddrlen_tok}.pedmp"
.writemem ${$arg1}\${processes_tok}_${baseaddr_tok}_${baseaddrlen_tok}.pedmp @$t3 L (@$t1 - @$t3)
}
}
}
}
}
r stage = 0
}
}
}
r stage = 0
}
}
.logopen ${$arg1}\dump_injected_pe_rwemem_fast.end
.printf "end"
.logclose
ad stage
ad temp
ad temp2
ad temp3
ad isPossiblePE
ad isDosMessageBased
ad pe
ad fileheader
ad optionalheader
ad sections
ad nsections
ad lastsect
ad prev1
ad prev2
ad baseaddr
ad baseaddrlen
}