M2Crypto：验证 DSA 签名
我在使用 Python/M2Crypto 验证 DSA 签名时遇到问题。签名是在 Java 中使用标准 java.security.Signature 类以及 Sun 的加密提供程序和 SHA1withDSA 算法指定生成的。
下面是一些 shell 输出：
>>> pk
<M2Crypto.DSA.DSA_pub instance at 0x20b6a28>
>>> sig = '302c02141c4bbb218215ebfec57288059ce814dc430d849502144dd0c581bf2213aff79d17eb37c939e120a97bd2'.decode('hex')
>>> data ='0501...9794'.decode('hex')
>>> pk.verify_asn1(sig, data)
------------------------------------------------------------
Traceback (most recent call last):
...
DSAError: wrong tag
签名值对我来说似乎没问题，它看起来像是两个整数的正确 ASN.1 编码序列（0x302c 指定 44 字节序列，0x0214 指定 20 字节整数），这是标准编码DSA 签名。
由于 DSA_pub.verify_asn1 方法甚至没有记录，我也尝试使用记录的 DSA_pub.verify 方法，但仍然没有雪茄：
>>> r = sig[4:24]
>>> s = sig[26:]
>>> md = sha1(data).digest()
>>> pk.verify(md, r, s)
------------------------------------------------------------
Traceback (most recent call last):
...
DSAError: encoding error
文档声明所有参数应该是“字节字符串”，但 verify 方法以某种方式设法提高编码错误。 我还尝试反转 r 和 s，以检查潜在的字节顺序问题，但这没有帮助。
我做错了什么？
I'm having trouble verifying DSA signatures using Python/M2Crypto. The signatures are generated in Java, using standard java.security.Signature class, with Sun's crypto provider and SHA1withDSA algorithm designation.
Here's some shell output:
>>> pk
<M2Crypto.DSA.DSA_pub instance at 0x20b6a28>
>>> sig = '302c02141c4bbb218215ebfec57288059ce814dc430d849502144dd0c581bf2213aff79d17eb37c939e120a97bd2'.decode('hex')
>>> data ='0501...9794'.decode('hex')
>>> pk.verify_asn1(sig, data)
------------------------------------------------------------
Traceback (most recent call last):
...
DSAError: wrong tag
The signature value seems OK to me, it looks like a proper ASN.1 encoded sequence of two integers (0x302c designates a 44-byte sequence, and 0x0214 designates a 20-byte integer), which is the standard encoding of DSA signatures.
Since the DSA_pub.verify_asn1 method isn't even documented, I also tried using the documented DSA_pub.verify method, but still no cigar:
>>> r = sig[4:24]
>>> s = sig[26:]
>>> md = sha1(data).digest()
>>> pk.verify(md, r, s)
------------------------------------------------------------
Traceback (most recent call last):
...
DSAError: encoding error
The docs state that all the parameters should be "byte strings", but the verify method somehow manages to raise an encoding error.
I also tried reversing r and s, to check for potential endianness problems but that didn't help.
What am I doing wrong?
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在测试中找到了解决方案： http://svn.osafoundation.org/m2crypto /trunk/tests/test_dsa.py
verify_asn1 方法应按如下方式使用：
Found a solution in the tests: http://svn.osafoundation.org/m2crypto/trunk/tests/test_dsa.py
The verify_asn1 method should be used as follows: