Thanks for the help above. However, I think I'm still missing something. When piping the DER binary data to openssl on the command line, the output appears to have three certificates in the example DER early in this thread. The code above has a list for certs, but it appears to only contain one cert at the end of the for loop. Is there a way to view the data from the other two? I've attached the output from openssl command line.
On Mon, Dec 24, 2018 at 11:51 AM Paul Kehrer <paul.l.keh...@gmail.com>
wrote:
> Great! I have an idea of how to implement an API for this limited subset
> of pkcs7 as a utility function like the pkcs12 support we recently merged.
> Hopefully I or someone else can get to it soon.
>
> -Paul
>
> On Dec 23, 2018, at 6:32 PM, Robert Simmons <rsimmo...@gmail.com> wrote:
>
> This works great! Thanks!
>
> On Sun, Dec 23, 2018 at 7:05 PM Paul Kehrer <paul.l.keh...@gmail.com>
> wrote:
>
>> One day I will learn to run the code I write before I ask people to use
>> it. The missing signers variable should go after the pkcs7 assignment. It
>> looks like this:
>>
>> signers = backend._lib.PKCS7_get0_signers(pkcs7, backend._ffi.NULL, 0)
>>
>> With that in place and using the extracted.der you previously provided I
>> can parse a cert, which has the following subject/issuer data:
>>
>> Issuer: C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA
>> Limited, CN=COMODO RSA Code Signing CA
>> Validity
>> Not Before: Oct 19 00:00:00 2018 GMT
>> Not After : Sep 25 23:59:59 2019 GMT
>> Subject: C=GB/postalCode=WA1 1RG, ST=UK,
>> L=WARRINGTON/street=Brunel House, 340 Firecrest Court, O=TATIANA PUK,
>> LIMITED, CN=TATIANA PUK, LIMITED
>>
>> I've also attached the cert. If this is what you're looking for then your
>> use case is covered by the existing issue, although I still need to decide
>> on an API for this.
>>
>> -Paul
>>
>>
>>
>> On December 23, 2018 at 2:17:54 AM, Robert Simmons (rsimmo...@gmail.com)
>> wrote:
>>
>> import os
>> import pathlib
>> import pefile
>>
>> target =
>> pathlib.Path().home().joinpath('Desktop').joinpath('HWID_4_0_6YMBWX.exe')
>> fname = str(target)
>> totsize = os.path.getsize(target)
>> pe = pefile.PE(fname)
>>
>> pe.parse_data_directories(directories=[pefile.DIRECTORY_ENTRY['IMAGE_DIRECTORY_ENTRY_SECURITY']])
>> sigoff = 0
>> siglen = 0
>> for s in pe.__structures__:
>> if s.name == 'IMAGE_DIRECTORY_ENTRY_SECURITY':
>> sigoff = s.VirtualAddress
>> siglen = s.Size
>> pe.close()
>> with open(fname, 'rb') as fh:
>> fh.seek(sigoff)
>> thesig = fh.read(siglen)
>>
>> from cryptography.hazmat.backends.openssl.backend import backend
>> from cryptography.hazmat.backends.openssl import x509
>>
>> bio = backend._bytes_to_bio(thesig[8:])
>> pkcs7 = backend._lib.d2i_PKCS7_bio(bio.bio, backend._ffi.NULL)
>> certs = []
>> for i in range(backend._lib.sk_X509_num(signers)):
>> x509_ptr = backend._lib.sk_X509_value(signers, i)
>> certs.append(x509._Certificate(backend, x509_ptr))
>>
>> That's the exact code I'm trying to run with the provided code snippet at
>> the end. If you want to follow along with the exact file I'm working with:
>> hxxps://dangerous[.]link/d9b72c43-1bdd-415b-b15f-3a436b26bca8
>>
>> The password to that file is "infected" and btw: it is live malware, so
>> please treat it accordingly. Run code on it in a safe environment for
>> handling malware.
>>
>> On Sun, Dec 23, 2018 at 4:10 AM Robert Simmons <rsimmo...@gmail.com>
>> wrote:
>>
>>> I've added the use case to the issue as requested. I tried the code
>>> snippet, but the contents of signers is missing. What should that be?
>>>
>>> NameError: name 'signers' is not defined
>>>
>>> On Fri, Dec 21, 2018 at 11:21 AM Paul Kehrer <paul.l.keh...@gmail.com>
>>> wrote:
>>>
>>>> Out of curiosity, does the following code load the cert you expect? der
>>>> should be the bytes of extracted.der:
>>>>
>>>> from cryptography.hazmat.backends.openssl.backend import backend
>>>> from cryptography.hazmat.backends.openssl import x509
>>>>
>>>> bio = backend._bytes_to_bio(der)
>>>> pkcs7 = backend._lib.d2i_PKCS7_bio(bio.bio, backend._ffi.NULL)
>>>> certs = []
>>>> for i in range(backend._lib.sk_X509_num(signers)):
>>>> x509_ptr = backend._lib.sk_X509_value(signers, i)
>>>> certs.append(x509._Certificate(backend, x509_ptr))
>>>>
>>>> Certs will be a list of signer certificates -- in this case, just one
>>>> cert in the list. Please note that this code does not manage memory
>>>> correctly so it should strictly be used to test if the cert you need is
>>>> being properly extracted :)
>>>>
>>>> -Paul (reaperhulk)
>>>>
>>>>
>>>> On December 21, 2018 at 8:02:13 AM, Paul Kehrer (
>>>> paul.l.keh...@gmail.com) wrote:
>>>>
>>>> Thanks, that's perfect. Looking at this data it's actually a PKCS7
>>>> envelope holding multiple certificates and at the moment cryptography
>>>> unfortunately has no interface for parsing PKCS7. If you wouldn't mind
>>>> sharing your use case directly on
>>>> https://github.com/pyca/cryptography/issues/3983 then it will help me
>>>> when I'm prioritizing features for upcoming releases.
>>>>
>>>> -Paul
>>>>
>>>>
>>>> On December 20, 2018 at 2:23:11 PM, Robert Simmons (rsimmo...@gmail.com)
>>>> wrote:
>>>>
>>>> Definitely. I've attached the DER data as extracted from the PE file
>>>> using the following code:
>>>>
>>>> pe = pefile.PE(fname)
>>>>
>>>> pe.parse_data_directories(directories=[pefile.DIRECTORY_ENTRY['IMAGE_DIRECTORY_ENTRY_SECURITY']])
>>>> sigoff = 0
>>>> siglen = 0
>>>> for s in pe.__structures__:
>>>> if s.name == 'IMAGE_DIRECTORY_ENTRY_SECURITY':
>>>> sigoff = s.VirtualAddress
>>>> siglen = s.Size
>>>> pe.close()
>>>> with open(fname, 'rb') as fh:
>>>> fh.seek(sigoff)
>>>> thesig = fh.read(siglen)
>>>> with open('extracted.der', 'wb') as fh:
>>>> fh.write(thesig[8:])
>>>>
>>>> I've attached extracted.der as a zip file to maintain integrity as an
>>>> attachment.
>>>>
>>>> Thanks!
>>>>
>>>> On Thu, Dec 20, 2018 at 11:12 AM Paul Kehrer <paul.l.keh...@gmail.com>
>>>> wrote:
>>>>
>>>>> Could you give us an example (in hex or b64 or something) so we can
>>>>> easily reproduce? Make sure any certs you're giving us don't contain
>>>>> sensitive data of course.
>>>>>
>>>>> -Paul
>>>>>
>>>>>
>>>>> On December 19, 2018 at 11:55:04 PM, Robert Simmons (
>>>>> rsimmo...@gmail.com) wrote:
>>>>>
>>>>> I've asked this question on Stack Overflow here:
>>>>> https://stackoverflow.com/q/53862702/1033217
>>>>>
>>>>> I have compared my code to Dider Stevens's disitool here (examine the
>>>>> function ExtractDigitalSignature):
>>>>>
>>>>> https://github.com/DidierStevens/DidierStevensSuite/blob/master/disitool.py
>>>>>
>>>>> When I load that extracted file into a variable and try to parse it
>>>>> with cryptography, it fails. If I pipe the same file to openssl on the
>>>>> command line, it works.
>>>>>
>>>>> I am thinking this has to do with the number of certificates in the
>>>>> directory in the PE file. There can be three (cert, intermediate CA, and
>>>>> CA, etc).
>>>>>
>>>>> Any idea what's going on?
>>>>> _______________________________________________
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cert
Description: Binary data
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