如何在C＃中验证用于签名APK文件的链接证书

Question

This code fails every time I pass it an APK file that has a certification chain (intermediate and Root CA). If the file is self-signed it works correctly.

RSACryptoServiceProvider csp = (RSACryptoServiceProvider)Cert.PublicKey.Key;
bool verified = csp.VerifyHash(hash, CryptoConfig.MapNameToOID("SHA1"), vData)

"hash" is the sha1 digest of the signature file (SF) and vData the encrypted hash of a signature (CMSG_ENCRYPTED_DIGEST,), both are byte arrays.

Answer 1

I will answer my own question after finding the answer. The problem resides when specifying the digest method.

A X509 certificate uses two algorithms that may not coincide (SignatureAlgorithm.FriendlyName and PublicKey.Key.SignatureAlgorithm). When verifying the hash you must make sure that it matches the SignatureAlgorithm of the certificate and not the algorithm used in the public key (which was my fault).

If in doubt, check both:

                            if (cert.SignatureAlgorithm.FriendlyName.ToString().Contains("sha256"))
                        {
                            SHA256Managed sha256 = new SHA256Managed();
                            byte[] hash256 = sha256.ComputeHash(sig);
                            RSACryptoServiceProvider csp = (RSACryptoServiceProvider)cert.PublicKey.Key;
                            verify_all.Add(csp.VerifyHash(hash256, CryptoConfig.MapNameToOID("SHA256"), vData));
                        }

                        else if (cert.SignatureAlgorithm.FriendlyName.ToString().Contains("sha1"))
                        {
                            SHA1Managed Sha1 = new SHA1Managed();
                            byte[] hash1 = sha1.ComputeHash(sig);                                
                            RSACryptoServiceProvider csp = (RSACryptoServiceProvider)cert.PublicKey.Key;
                            verify_all.Add(csp.VerifyHash(hash1, CryptoConfig.MapNameToOID("SHA256"), vData));
                        }