M2Crypto.SMIME.PKCS7_Error：没有内容答案

【问题标题】：M2Crypto.SMIME.PKCS7_Error: no contentM2Crypto.SMIME.PKCS7_Error：没有内容
【发布时间】：2021-10-24 12:16:06
【问题描述】：

verify_data = b'MIIEEwYJKoZIhvcNAQcCoIIEBDCCBAACAQExCzAJBgUrDgMCGgUAMAsGCSqGSIb3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\nKhWAgLyDMCKYf16bDvpAJTtqr/jG6sH7NK0a4wxiLu8yb2ZFnijs'

这是我要反序列化的数据。我正在尝试从签名内容中获取数据。

from M2Crypto import SMIME, X509, BIO

s = SMIME.SMIME()
sig = b"""
-----BEGIN PKCS7-----
%s
-----END PKCS7-----
    """ % verify_data

buf = BIO.MemoryBuffer(sig)
p7 = SMIME.load_pkcs7_bio(buf)
sk = X509.X509_Stack()
signers = p7.get0_signers(sk)
signer = signers[0]
sk.push(signer)
s.set_x509_stack(sk)
stor = X509.X509_Store()
stor.add_cert(signer)
s.set_x509_store(stor)
v = s.verify(p7, flags=SMIME.PKCS7_NOVERIFY)

我收到了这个错误

M2Crypto.SMIME.PKCS7_Error：无内容

【问题讨论】：

标签： python-3.x cryptography signature m2crypto

【解决方案1】：

确实没有内容。

$ openssl asn1parse <68904580.p7 -i
    0:d=0  hl=4 l=1043 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim:  OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1028 cons:  cont [ 0 ]
   19:d=2  hl=4 l=1024 cons:   SEQUENCE
   23:d=3  hl=2 l=   1 prim:    INTEGER           :01
   26:d=3  hl=2 l=  11 cons:    SET
   28:d=4  hl=2 l=   9 cons:     SEQUENCE
   30:d=5  hl=2 l=   5 prim:      OBJECT            :sha1
   37:d=5  hl=2 l=   0 prim:      NULL
   39:d=3  hl=2 l=  11 cons:    SEQUENCE
   41:d=4  hl=2 l=   9 prim:     OBJECT            :pkcs7-data
   52:d=3  hl=4 l= 519 cons:    cont [ 0 ]
[snip cert]
  575:d=3  hl=4 l= 468 cons:    SET
  579:d=4  hl=4 l= 464 cons:     SEQUENCE
[snip signerinfo]

如您所见，39 处的ContentInfo 仅包含 contentType OID 而不是 ASN.1-ly OPTIONAL 内容。这就是 PKCS7 所称的external signature，现在通常被称为分离签名——也就是说，与它所应用的数据分开传输和/或存储的签名。由于数据不在带有签名的消息中，为了验证签名，数据必须从其他地方提供，并且在 OpenSSL 中是一个 BIO。

你需要supply a data_BIO that contains/reads the data

【讨论】：