如何将由openSSL生成的RSA公钥加载到RSACryptoServiceProvider中？

Question

我正在编写一个 .Net 类，用于从我们的中央身份验证服务器读取 cookie。它包含 UserId、一些时间戳和由 openssl_sign() 使用 2048 位 RSA 密钥和 SHA1 哈希创建的签名。

当前公钥在服务器上以 openssl PEM 格式提供，并且偶尔会更改。我无法仅使用 .Net 托管代码（尚未）读取密钥，并制定了以下过程使其正常工作：

- 从公钥中提取指数和模数。 - 检查密钥是否仍为 2048 位。 - 将密钥长度、指数和模数存储在源中，编译并部署（删除模数前导零以使其正常工作）。

然后，该类创建一个 new RSACryptoServiceProvider(2048)，并将公共组件使用 RSAParameters 结构馈送到 CSP 中。然后验证签名成功。

我想让这个过程在密钥更改时不需要我创建、编译和部署新程序集。为了使事情更有趣，我想仅使用托管代码（排除了我找到的大多数示例）。当创建 AsnEncodedData(oid, data) 实例时，内部 ASN.1 Reader 听起来很完美，但我找到的唯一 oid，RSA aka 1.2.840.113549.1.1.1，没有起作用，只产生了原始字节。

添加：以前的公钥

-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAMW90O6C17fapbS35auKolsy7kI0FOE1
C08y5HqgZ0rMXoocV4nHSHYBm2HVx2QSR5OLQtERgWDmxOu+vwU1GXUCAwEAAQ==
-----END PUBLIC KEY-----

我发现 pempublic.cs，似乎使用 openSSL 的源代码解决了这个问题。我将保持问题开放，看看是否有其他解决方案。

- Stephan B

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这个问题有进展了吗？我看到了5个完全相同的问题，最接近的答案是pempublic.cs文件。但是这个文件看起来有点凌乱。 - Devela

Answer 1

加载私钥，让我们使用此代码：

private RSACryptoServiceProvider GetPrivateKey(string privateKey)
    {
        byte[] privkey = Convert.FromBase64String(privateKey);
        byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;

        // --------- Set up stream to decode the asn.1 encoded RSA private key ------
        MemoryStream mem = new MemoryStream(privkey);
        BinaryReader binr = new BinaryReader(mem);  //wrap Memory Stream with BinaryReader for easy reading
        byte bt = 0;
        ushort twobytes = 0;
        int elems = 0;
        try
        {
            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8230)
                binr.ReadInt16();    //advance 2 bytes
            else
                return null;

            twobytes = binr.ReadUInt16();
            if (twobytes != 0x0102) //version number
                return null;
            bt = binr.ReadByte();
            if (bt != 0x00)
                return null;


            //------ all private key components are Integer sequences ----
            elems = GetIntegerSize(binr);
            MODULUS = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            E = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            D = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            P = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            Q = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            DP = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            DQ = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            IQ = binr.ReadBytes(elems);

            // ------- create RSACryptoServiceProvider instance and initialize with public key -----
            CspParameters CspParameters = new CspParameters();
            CspParameters.Flags = CspProviderFlags.UseMachineKeyStore;
            RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(1024, CspParameters);
            RSAParameters RSAparams = new RSAParameters();
            RSAparams.Modulus = MODULUS;
            RSAparams.Exponent = E;
            RSAparams.D = D;
            RSAparams.P = P;
            RSAparams.Q = Q;
            RSAparams.DP = DP;
            RSAparams.DQ = DQ;
            RSAparams.InverseQ = IQ;
            RSA.ImportParameters(RSAparams);
            return RSA;
        }
        catch (Exception ex)
        {
            return null;
        }
        finally
        {
            binr.Close();
        }
    }

要加载公钥，我们可以使用以下代码：

private RSACryptoServiceProvider GetPublicKey(string publicKeyString)
    {
        // encoded OID sequence for  PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
        byte[] SeqOID = {0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00} ;
        byte[] x509key;
        byte[] seq = new byte[15];
        int x509size;

        x509key = Convert.FromBase64String(publicKeyString);
        x509size = x509key.Length;

        // ---------  Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob  ------
        MemoryStream mem = new MemoryStream(x509key);
        BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
        byte bt = 0;
        ushort twobytes = 0;

        try
        {

            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8230)
                binr.ReadInt16();   //advance 2 bytes
            else
                return null;

            seq = binr.ReadBytes(15);       //read the Sequence OID
            if (!CompareBytearrays(seq, SeqOID))    //make sure Sequence for OID is correct
                return null;

            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8203)
                binr.ReadInt16();   //advance 2 bytes
            else
                return null;

            bt = binr.ReadByte();
            if (bt != 0x00)     //expect null byte next
                return null;

            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8230)
                binr.ReadInt16();   //advance 2 bytes
            else
                return null;

            twobytes = binr.ReadUInt16();
            byte lowbyte = 0x00;
            byte highbyte = 0x00;

            if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
                lowbyte = binr.ReadByte();  // read next bytes which is bytes in modulus
            else if (twobytes == 0x8202)
            {
                highbyte = binr.ReadByte(); //advance 2 bytes
                lowbyte = binr.ReadByte();
            }
            else
                return null;
            byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };   //reverse byte order since asn.1 key uses big endian order
            int modsize = BitConverter.ToInt32(modint, 0);

            int firstbyte = binr.PeekChar();
            if (firstbyte == 0x00)
            {   //if first byte (highest order) of modulus is zero, don't include it
                binr.ReadByte();    //skip this null byte
                modsize -= 1;   //reduce modulus buffer size by 1
            }

            byte[] modulus = binr.ReadBytes(modsize);   //read the modulus bytes

            if (binr.ReadByte() != 0x02)            //expect an Integer for the exponent data
                return null;
            int expbytes = (int)binr.ReadByte();        // should only need one byte for actual exponent data (for all useful values)
            byte[] exponent = binr.ReadBytes(expbytes);

            // ------- create RSACryptoServiceProvider instance and initialize with public key -----
            RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
            RSAParameters RSAKeyInfo = new RSAParameters();
            RSAKeyInfo.Modulus = modulus;
            RSAKeyInfo.Exponent = exponent;
            RSA.ImportParameters(RSAKeyInfo);

            return RSA;
        }

        finally
        {
            binr.Close();
        }
    }

你可以阅读原帖在此以获取更多细节。

- Pham Hong Phong

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如何获取整数大小？ - th1rdey3

请阅读原始帖子，链接如下：link - Pham Hong Phong

@PhamHongPhong 页面未找到（404） - Alexander

Answer 2

你拥有私钥，因此从密钥生成自签名证书可能更容易。您可以使用 System.Security.Cryptography.X509Certificates.X509Certificate（我认为您应该将证书保存为 DER / ASN.1 格式而不是 PEM）来加载证书，并使用 X509Certificate.GetPublicKey() 获取公钥。

- Mathias Brossard

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抱歉回复晚了，但是你的答案并没有帮到我。我无法从这个应用程序中获取私钥，我的问题的核心是如何从PEM格式中获取DER或ASN.1格式的密钥。 - Stephan B