M2Crypto - Extract detached PKCS7 signature from PKCS7 (signature&data)
Alexander Williams
alexandrucalin29 at gmail.com
Sun Aug 3 11:13:45 EDT 2014
I want to break a PKCS7 signature that contains data + signature into separate: raw data & detached PKCS7 signature in python.
I can get the data fro the signature because the verification routine returns it, but how can I get the detached signature ?
def verify_pkcs7(data_bio, signature_bio, cacert_bio, format=X509.FORMAT_PEM):
sm_obj = SMIME.SMIME()
st = X509.X509_Store()
st.add_cert(X509.load_cert_string(cacert_bio))
sm_obj.set_x509_store(st)
if format == X509.FORMAT_PEM:
p7 = SMIME.load_pkcs7_bio(signature_bio)
else:
p7 = SMIME.PKCS7(m2.pkcs7_read_bio_der(signature_bio._ptr()), 1)
sk = p7.get0_signers(X509.X509_Stack())
sm_obj.set_x509_stack(sk)
try:
v = sm_obj.verify(p7, data_bio)
if v:
print "Client signature verified."
with open('file.rar', 'wb') as ff:
ff.write(v)
except Exception as e:
print str(e)
print "*** INVALID CLIENT MESSAGE SIGNATURE ***"
My wild guess is that it one of these functions.. I base my assumption on the fact that M2Crypto is a wrapper over OpenSSL.
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