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);
#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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