无法使用pkcs7 PyAsn1从PyAsn1信封中获取加密密钥

Question

我试图从一个PKCS7信封中提取一个RSA加密的AES密钥，并得到一个错误，上面说加密的密钥是一个模式，而不是一个值。为什么信封里有一行写着encryptedKey=.

content, rest = decode(env_der, asn1Spec=rfc2315.ContentInfo())
assert content['contentType'] == rfc2315.envelopedData

myenvelop, rest = decode(content['content'], asn1Spec=rfc2315.EnvelopedData())
print(myenvelop)
print(myenvelop['recipientInfos'][1]['encryptedKey'])

该代码的结果是：

    EnvelopedData:
 version=0
 recipientInfos=RecipientInfos:
  RecipientInfo:
   version=0
   issuerAndSerialNumber=IssuerAndSerialNumber:
    issuer=Name:
     =RDNSequence:
      RelativeDistinguishedName:
       AttributeTypeAndValue:
        type=2.5.4.6
        value=0x13025553
      RelativeDistinguishedName:
       AttributeTypeAndValue:
        type=2.5.4.10
        value=0x130f552e532e20476f7665726e6d656e74
      RelativeDistinguishedName:
       AttributeTypeAndValue:
        type=2.5.4.11
        value=0x131c556e697465642053746174657320506f7374616c2053657276696365
      RelativeDistinguishedName:
       AttributeTypeAndValue:
        type=2.5.4.3
        value=0x131255535053496e7465726e616c537562324341


    serialNumber=488380148491395325238848

   keyEncryptionAlgorithm=KeyEncryptionAlgorithmIdentifier:
    algorithm=1.2.840.113549.1.1.1
    parameters=0x0500

   encryptedKey=0x1b396af2d3a1eca95621262c85fd11835616fc5e1d342c752a2082dd559a23c8f11c21d68b8d5317c721c1d7eba7a1c5bef8ee15d428da74c513a61437d6ba7e6ba4286540ec6c068091b5a611ea36c0aaf44b3055fddbdfe40f5472aa0c1daaa69b67ff5bac3e9de17f5c12f7bd4c86ad4d505341308048c82f29cf71c3bcb9108039ccbf7ebc5f9784570f360a1ec3c529dfc94950d290aa95d80e849688b3cc509851173cedf12e963dcd1d083b87ab3a41b7a0db5f79ca4a52b28b3758fec1f20a627d181e95547d56f0b51fcf2a211371df8d62b5e62473ece192649493d89a72693ffe94c2dbfb7e5ba1fa1c04b623b5094600786b931e6cd1a6f406d1

 encryptedContentInfo=EncryptedContentInfo:
  contentType=1.2.840.113549.1.7.1
  contentEncryptionAlgorithm=ContentEncryptionAlgorithmIdentifier:
   algorithm=2.16.840.1.101.3.4.1.42
   parameters=0x041016b5378e3bfde72671a7a207a4038840



Traceback (most recent call last):
  File "C:/Users/VoxaiLap10/Desktop/pythonbible/cryptotestpemmp3_b_md5_7-19-18b.py", line 81, in <module>
    unEnvelop(filename, pemFile, outfilename)
  File "C:/Users/VoxaiLap10/Desktop/pythonbible/cryptotestpemmp3_b_md5_7-19-18b.py", line 41, in unEnvelop
    print(myenvelop['recipientInfos'][1]['encryptedKey'])
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\pyasn1\type\univ.py", line 882, in __str__
    return self._value.decode(self.encoding)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\pyasn1\type\base.py", line 221, in __getattr__
    raise error.PyAsn1Error('Attempted "%s" operation on ASN.1 schema object' % attr)
pyasn1.error.PyAsn1Error: Attempted "decode" operation on ASN.1 schema object

Answer 1

可疑的部分是[1]订阅，应该是[0]吗？我假设您正在尝试处理RecipientInfos序列的第一个元素，它是基于零的。

错误消息本身意味着您要处理的对象没有初始化，例如，没有填充任何具体的值。这就是为什么它只能用作“模式”，例如，用于类型信息。

当您通过不存在的索引订阅RecipientInfos时，将创建新的RecipientInfo元素，该元素显然不包含任何具体的值(除了默认值)。从这个意义上说，它仍然是一个模式，而不是模式实例。