微信开发之消息体签名和加解密

  前几篇主要是微信开发的准备工作，也没有什么技术含量。在第一篇和第二篇中，我主要讲的是使用花生壳来配合vs进行代码调试，也一度被园友吐槽本人是花生壳请来的逗比，没办法，为了和花生壳划清界限，在本篇进入正文前，为大家介绍一个比花生壳更好用的工具ngrok，ngrok的好处我就不在此具体说明了，毕竟不是本文的重点

   出于安全考虑，微信公众平台在10月份的时候加入了消息体的加解密功能，首先，需要先验证签名，用于公众平台和公众账号验证消息体的正确性，其次，针对推送给公众号的普通消息和事件消息，以及推送给设备公众账号的设备进行加密，最后，公众号对密文消息的回复也需要加密。启用加解密功能后，公众平台服务器在向公众号服务器配置地址推送消息时，url将新增加两个参数，一个是加密类型一个是消息体签名，并以此来体现新功能。加密算法采用AES。关于明文模式，兼容模式，安全模式的说明，大家请参考官方文档.

验证消息真实性和加解密的帮助类官方提供的有demo，再次不详细讲述了，下载下来可以直接调用，下面请看代码：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Security.Cryptography;using System.IO;using System.Net;namespace WxApi
{    public class Cryptography
    {        public static UInt32 HostToNetworkOrder(UInt32 inval)
        {
            UInt32 outval = 0;            for (int i = 0; i < 4; i++)
                outval = (outval << 8) + ((inval >> (i * 8)) & 255);            return outval;
        }        public static Int32 HostToNetworkOrder(Int32 inval)
        {
            Int32 outval = 0;            for (int i = 0; i < 4; i++)
                outval = (outval << 8) + ((inval >> (i * 8)) & 255);            return outval;
        }        /// <summary>
        /// 解密方法        /// </summary>
        /// <param name="Input">密文</param>
        /// <param name="EncodingAESKey"></param>
        /// <returns></returns>
        /// 
        public static string AES_decrypt(String Input, string EncodingAESKey, ref string appid)
        {            byte[] Key;
            Key = Convert.FromBase64String(EncodingAESKey + "=");            byte[] Iv = new byte[16];
            Array.Copy(Key, Iv, 16);            byte[] btmpMsg = AES_decrypt(Input, Iv, Key);            int len = BitConverter.ToInt32(btmpMsg, 16);
            len = IPAddress.NetworkToHostOrder(len);            byte[] bMsg = new byte[len];            byte[] bAppid = new byte[btmpMsg.Length - 20 - len];
            Array.Copy(btmpMsg, 20, bMsg, 0, len);
            Array.Copy(btmpMsg, 20 + len, bAppid, 0, btmpMsg.Length - 20 - len);            string oriMsg = Encoding.UTF8.GetString(bMsg);
            appid = Encoding.UTF8.GetString(bAppid);            return oriMsg;
        }        public static String AES_encrypt(String Input, string EncodingAESKey, string appid)
        {            byte[] Key;
            Key = Convert.FromBase64String(EncodingAESKey + "=");            byte[] Iv = new byte[16];
            Array.Copy(Key, Iv, 16);            string Randcode = CreateRandCode(16);            byte[] bRand = Encoding.UTF8.GetBytes(Randcode);            byte[] bAppid = Encoding.UTF8.GetBytes(appid);            byte[] btmpMsg = Encoding.UTF8.GetBytes(Input);            byte[] bMsgLen = BitConverter.GetBytes(HostToNetworkOrder(btmpMsg.Length));            byte[] bMsg = new byte[bRand.Length + bMsgLen.Length + bAppid.Length + btmpMsg.Length];

            Array.Copy(bRand, bMsg, bRand.Length);
            Array.Copy(bMsgLen, 0, bMsg, bRand.Length, bMsgLen.Length);
            Array.Copy(btmpMsg, 0, bMsg, bRand.Length + bMsgLen.Length, btmpMsg.Length);
            Array.Copy(bAppid, 0, bMsg, bRand.Length + bMsgLen.Length + btmpMsg.Length, bAppid.Length);            return AES_encrypt(bMsg, Iv, Key);

        }        private static string CreateRandCode(int codeLen)
        {            string codeSerial = "2,3,4,5,6,7,a,c,d,e,f,h,i,j,k,m,n,p,r,s,t,A,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,U,V,W,X,Y,Z";            if (codeLen == 0)
            {
                codeLen = 16;
            }            string[] arr = codeSerial.Split(&#39;,&#39;);            string code = "";            int randValue = -1;
            Random rand = new Random(unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < codeLen; i++)
            {
                randValue = rand.Next(0, arr.Length - 1);
                code += arr[randValue];
            }            return code;
        }        private static String AES_encrypt(String Input, byte[] Iv, byte[] Key)
        {            var aes = new RijndaelManaged();            //秘钥的大小，以位为单位
            aes.KeySize = 256;            //支持的块大小
            aes.BlockSize = 128;            //填充模式
            aes.Padding = PaddingMode.PKCS7;
            aes.Mode = CipherMode.CBC;
            aes.Key = Key;
            aes.IV = Iv;            var encrypt = aes.CreateEncryptor(aes.Key, aes.IV);            byte[] xBuff = null;            using (var ms = new MemoryStream())
            {                using (var cs = new CryptoStream(ms, encrypt, CryptoStreamMode.Write))
                {                    byte[] xXml = Encoding.UTF8.GetBytes(Input);
                    cs.Write(xXml, 0, xXml.Length);
                }
                xBuff = ms.ToArray();
            }
            String Output = Convert.ToBase64String(xBuff);            return Output;
        }        private static String AES_encrypt(byte[] Input, byte[] Iv, byte[] Key)
        {            var aes = new RijndaelManaged();            //秘钥的大小，以位为单位
            aes.KeySize = 256;            //支持的块大小
            aes.BlockSize = 128;            //填充模式            //aes.Padding = PaddingMode.PKCS7;
            aes.Padding = PaddingMode.None;
            aes.Mode = CipherMode.CBC;
            aes.Key = Key;
            aes.IV = Iv;            var encrypt = aes.CreateEncryptor(aes.Key, aes.IV);            byte[] xBuff = null;            #region 自己进行PKCS7补位，用系统自己带的不行            byte[] msg = new byte[Input.Length + 32 - Input.Length % 32];
            Array.Copy(Input, msg, Input.Length);            byte[] pad = KCS7Encoder(Input.Length);
            Array.Copy(pad, 0, msg, Input.Length, pad.Length);            #endregion

            #region 注释的也是一种方法，效果一样            //ICryptoTransform transform = aes.CreateEncryptor();            //byte[] xBuff = transform.TransformFinalBlock(msg, 0, msg.Length);
            #endregion

            using (var ms = new MemoryStream())
            {                using (var cs = new CryptoStream(ms, encrypt, CryptoStreamMode.Write))
                {
                    cs.Write(msg, 0, msg.Length);
                }
                xBuff = ms.ToArray();
            }

            String Output = Convert.ToBase64String(xBuff);            return Output;
        }        private static byte[] KCS7Encoder(int text_length)
        {            int block_size = 32;            // 计算需要填充的位数
            int amount_to_pad = block_size - (text_length % block_size);            if (amount_to_pad == 0)
            {
                amount_to_pad = block_size;
            }            // 获得补位所用的字符
            char pad_chr = chr(amount_to_pad);            string tmp = "";            for (int index = 0; index < amount_to_pad; index++)
            {
                tmp += pad_chr;
            }            return Encoding.UTF8.GetBytes(tmp);
        }        /**
         * 将数字转化成ASCII码对应的字符，用于对明文进行补码
         * 
         * @param a 需要转化的数字
         * @return 转化得到的字符         */
        static char chr(int a)
        {            byte target = (byte)(a & 0xFF);            return (char)target;
        }        private static byte[] AES_decrypt(String Input, byte[] Iv, byte[] Key)
        {
            RijndaelManaged aes = new RijndaelManaged();
            aes.KeySize = 256;
            aes.BlockSize = 128;
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.None;
            aes.Key = Key;
            aes.IV = Iv;            var decrypt = aes.CreateDecryptor(aes.Key, aes.IV);            byte[] xBuff = null;            using (var ms = new MemoryStream())
            {                using (var cs = new CryptoStream(ms, decrypt, CryptoStreamMode.Write))
                {                    byte[] xXml = Convert.FromBase64String(Input);                    byte[] msg = new byte[xXml.Length + 32 - xXml.Length % 32];
                    Array.Copy(xXml, msg, xXml.Length);
                    cs.Write(xXml, 0, xXml.Length);
                }
                xBuff = decode2(ms.ToArray());
            }            return xBuff;
        }        private static byte[] decode2(byte[] decrypted)
        {            int pad = (int)decrypted[decrypted.Length - 1];            if (pad < 1 || pad > 32)
            {
                pad = 0;
            }            byte[] res = new byte[decrypted.Length - pad];
            Array.Copy(decrypted, 0, res, 0, decrypted.Length - pad);            return res;
        }
    }
}

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Xml;using System.Collections;//using System.Web;using System.Security.Cryptography;//-40001 ： 签名验证错误//-40002 :  xml解析失败//-40003 :  sha加密生成签名失败//-40004 :  AESKey 非法//-40005 :  appid 校验错误//-40006 :  AES 加密失败//-40007 ： AES 解密失败//-40008 ： 解密后得到的buffer非法//-40009 :  base64加密异常//-40010 :  base64解密异常namespace WxApi
{   public class MsgCrypt
    {        string m_sToken;        string m_sEncodingAESKey;        string m_sAppID;        enum WXBizMsgCryptErrorCode
        {
            WXBizMsgCrypt_OK = 0,
            WXBizMsgCrypt_ValidateSignature_Error = -40001,
            WXBizMsgCrypt_ParseXml_Error = -40002,
            WXBizMsgCrypt_ComputeSignature_Error = -40003,
            WXBizMsgCrypt_IllegalAesKey = -40004,
            WXBizMsgCrypt_ValidateAppid_Error = -40005,
            WXBizMsgCrypt_EncryptAES_Error = -40006,
            WXBizMsgCrypt_DecryptAES_Error = -40007,
            WXBizMsgCrypt_IllegalBuffer = -40008,
            WXBizMsgCrypt_EncodeBase64_Error = -40009,
            WXBizMsgCrypt_DecodeBase64_Error = -40010
        };        //构造函数        // @param sToken: 公众平台上，开发者设置的Token        // @param sEncodingAESKey: 公众平台上，开发者设置的EncodingAESKey        // @param sAppID: 公众帐号的appid
        public MsgCrypt(string sToken, string sEncodingAESKey, string sAppID)
        {
            m_sToken = sToken;
            m_sAppID = sAppID;
            m_sEncodingAESKey = sEncodingAESKey;
        }        // 检验消息的真实性，并且获取解密后的明文        // @param sMsgSignature: 签名串，对应URL参数的msg_signature        // @param sTimeStamp: 时间戳，对应URL参数的timestamp        // @param sNonce: 随机串，对应URL参数的nonce        // @param sPostData: 密文，对应POST请求的数据        // @param sMsg: 解密后的原文，当return返回0时有效        // @return: 成功0，失败返回对应的错误码
        public int DecryptMsg(string sMsgSignature, string sTimeStamp, string sNonce, string sPostData, ref string sMsg)
        {            if (m_sEncodingAESKey.Length != 43)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_IllegalAesKey;
            }
            XmlDocument doc = new XmlDocument();
            XmlNode root;            string sEncryptMsg;            try
            {
                doc.LoadXml(sPostData);
                root = doc.FirstChild;
                sEncryptMsg = root["Encrypt"].InnerText;
            }            catch (Exception)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ParseXml_Error;
            }            //verify signature
            int ret = 0;
            ret = VerifySignature(m_sToken, sTimeStamp, sNonce, sEncryptMsg, sMsgSignature);            if (ret != 0)                return ret;            //decrypt
            string cpid = "";            try
            {
                sMsg = Cryptography.AES_decrypt(sEncryptMsg, m_sEncodingAESKey, ref cpid);
            }            catch (FormatException)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_DecodeBase64_Error;
            }            catch (Exception)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_DecryptAES_Error;
            }            if (cpid != m_sAppID)                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ValidateAppid_Error;            return 0;
        }        //将企业号回复用户的消息加密打包        // @param sReplyMsg: 企业号待回复用户的消息，xml格式的字符串        // @param sTimeStamp: 时间戳，可以自己生成，也可以用URL参数的timestamp        // @param sNonce: 随机串，可以自己生成，也可以用URL参数的nonce        // @param sEncryptMsg: 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串,        //                        当return返回0时有效        // return：成功0，失败返回对应的错误码
        public int EncryptMsg(string sReplyMsg, string sTimeStamp, string sNonce, ref string sEncryptMsg)
        {            if (m_sEncodingAESKey.Length != 43)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_IllegalAesKey;
            }            string raw = "";            try
            {
                raw = Cryptography.AES_encrypt(sReplyMsg, m_sEncodingAESKey, m_sAppID);
            }            catch (Exception)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_EncryptAES_Error;
            }            string MsgSigature = "";            int ret = 0;
            ret = GenarateSinature(m_sToken, sTimeStamp, sNonce, raw, ref MsgSigature);            if (0 != ret)                return ret;
            sEncryptMsg = "";            string EncryptLabelHead = "<Encrypt><![CDATA[";            string EncryptLabelTail = "]]></Encrypt>";            string MsgSigLabelHead = "<MsgSignature><![CDATA[";            string MsgSigLabelTail = "]]></MsgSignature>";            string TimeStampLabelHead = "<TimeStamp><![CDATA[";            string TimeStampLabelTail = "]]></TimeStamp>";            string NonceLabelHead = "<Nonce><![CDATA[";            string NonceLabelTail = "]]></Nonce>";
            sEncryptMsg = sEncryptMsg + "<xml>" + EncryptLabelHead + raw + EncryptLabelTail;
            sEncryptMsg = sEncryptMsg + MsgSigLabelHead + MsgSigature + MsgSigLabelTail;
            sEncryptMsg = sEncryptMsg + TimeStampLabelHead + sTimeStamp + TimeStampLabelTail;
            sEncryptMsg = sEncryptMsg + NonceLabelHead + sNonce + NonceLabelTail;
            sEncryptMsg += "</xml>";            return 0;
        }        public class DictionarySort : System.Collections.IComparer
        {            public int Compare(object oLeft, object oRight)
            {                string sLeft = oLeft as string;                string sRight = oRight as string;                int iLeftLength = sLeft.Length;                int iRightLength = sRight.Length;                int index = 0;                while (index < iLeftLength && index < iRightLength)
                {                    if (sLeft[index] < sRight[index])                        return -1;                    else if (sLeft[index] > sRight[index])                        return 1;                    else
                        index++;
                }                return iLeftLength - iRightLength;

            }
        }        //Verify Signature
        private static int VerifySignature(string sToken, string sTimeStamp, string sNonce, string sMsgEncrypt, string sSigture)
        {            string hash = "";            int ret = 0;
            ret = GenarateSinature(sToken, sTimeStamp, sNonce, sMsgEncrypt, ref hash);            if (ret != 0)                return ret;            //System.Console.WriteLine(hash);
            if (hash == sSigture)                return 0;            else
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ValidateSignature_Error;
            }
        }        public static int GenarateSinature(string sToken, string sTimeStamp, string sNonce, string sMsgEncrypt, ref string sMsgSignature)
        {
            ArrayList AL = new ArrayList();
            AL.Add(sToken);
            AL.Add(sTimeStamp);
            AL.Add(sNonce);
            AL.Add(sMsgEncrypt);
            AL.Sort(new DictionarySort());            string raw = "";            for (int i = 0; i < AL.Count; ++i)
            {
                raw += AL[i];
            }

            SHA1 sha;
            ASCIIEncoding enc;            string hash = "";            try
            {
                sha = new SHA1CryptoServiceProvider();
                enc = new ASCIIEncoding();                byte[] dataToHash = enc.GetBytes(raw);                byte[] dataHashed = sha.ComputeHash(dataToHash);
                hash = BitConverter.ToString(dataHashed).Replace("-", "");
                hash = hash.ToLower();
            }            catch (Exception)
            {                return (int)WXBizMsgCryptErrorCode.WXBizMsgCrypt_ComputeSignature_Error;
            }
            sMsgSignature = hash;            return 0;
        }
    }
}

在处理程序中，首先获取到公众平台服务器发送过来的数据，并转成字符串。代码如下

string postStr = "";
            Stream s = VqiRequest.GetInputStream();//此方法是对System.Web.HttpContext.Current.Request.InputStream的封装，可直接代码
            byte[] b = new byte[s.Length];
            s.Read(b, 0, (int)s.Length);
            postStr = Encoding.UTF8.GetString(b);

然后再分别获取url中的参数：timestamp，nonce，msg_signature，encrypt_type。可以看到，在明文模式下是没有encrypt_type参数的。如图：

明文模式

 

兼容模式和安全模式

兼容模式和安全模式则加入了消息体的签名与加密类型两个参数。

由于在实际的运营中，兼容模式不太可能使用，所以在此不做详细介绍了。

接着上面的讲。获取到url中的参数后，判断encrypt_type的值是否为aes，如果是则说明是使用的兼容模式或安全模式，此时则需调用解密相关的方法进行解密。

if (encrypt_type == "aes")
            {
                requestXML.IsAes = true;
                requestXML.EncodingAESKey = aeskey;
                requestXML.token = token;
                requestXML.appid = appid;                var ret = new MsgCrypt(token, aeskey, appid);                int r = ret.DecryptMsg(msg_signature, timestamp, nonce, postStr, ref data);                if (r!=0)
                {
                    WxApi.Base.WriteBug("消息解密失败");                    return null;
               
                }
            }

否则则直接解析接收到的xml字符串。

下图是接收到的密文：

解密之后的内容如下：

此时就可以解析此xml了。

当需要回复加密的请求时，回复的内容也是需要加密的，所以在回复前需要判断此条接收到的消息是否加密，如果是加密的，则需要将需要回复的内容加密后，再进行回复。回复消息的方法将在下一篇中具体讲解，此篇只讲解加密的过程。

处理代码如下：

private static void Response(WeiXinRequest requestXML, string data)
        {            if (requestXML.IsAes)
            {                var wxcpt = new MsgCrypt(requestXML.token, requestXML.EncodingAESKey, requestXML.appid);
                 wxcpt.EncryptMsg(data, Utils.ConvertDateTimeInt(DateTime.Now).ToString(), Utils.GetRamCode(), ref data);
            }
            Utils.ResponseWrite(data);
      
        }

将接收到的消息实体和需要回复的内容xml传递过来，如果是加密的，则加密后再Response，否则直接Response。

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