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(',');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);#endregionusing (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appidpublic 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 signatureint ret = 0;ret = VerifySignature(m_sToken, sTimeStamp, sNonce, sEncryptMsg, sMsgSignature);if (ret != 0)return ret;//decryptstring 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;elseindex++;}return iLeftLength - iRightLength;}}//Verify Signatureprivate 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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