// 回复消息给微信服务器(安全模式).
// 要求 msg 是有效的消息数据结构(经过 encoding/xml marshal 后符合消息的格式);
// 如果有必要可以修改 Request 里面的某些值, 比如 TimeStamp.
func WriteAESResponse(w http.ResponseWriter, r *Request, msg interface{}) (err error) {
if w == nil {
return errors.New("nil http.ResponseWriter")
}
if r == nil {
return errors.New("nil Request")
}
if msg == nil {
return errors.New("nil message")
}
MsgRawXML, err := xml.Marshal(msg)
if err != nil {
return
}
EncryptedMsg := util.AESEncryptMsg(r.Random, MsgRawXML, r.WechatAppId, r.AESKey)
base64EncryptedMsg := base64.StdEncoding.EncodeToString(EncryptedMsg)
responseHttpBody := ResponseHttpBody{
EncryptedMsg: base64EncryptedMsg,
TimeStamp: r.TimeStamp,
Nonce: r.Nonce,
}
TimestampStr := strconv.FormatInt(responseHttpBody.TimeStamp, 10)
responseHttpBody.MsgSignature = util.MsgSign(r.WechatToken, TimestampStr,
responseHttpBody.Nonce, responseHttpBody.EncryptedMsg)
return xml.NewEncoder(w).Encode(&responseHttpBody)
}
// ServeHTTP 处理 http 消息请求
// NOTE: 调用者保证所有参数有效
func ServeHTTP(w http.ResponseWriter, r *http.Request, urlValues url.Values,
wechatServer WechatServer, invalidRequestHandler InvalidRequestHandler) {
switch r.Method {
case "POST": // 消息处理
signature1, timestampStr, nonce, encryptType, msgSignature1, err := parsePostURLQuery(urlValues)
if err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
timestamp, err := strconv.ParseInt(timestampStr, 10, 64)
if err != nil {
err = errors.New("can not parse timestamp to int64: " + timestampStr)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
switch encryptType {
case "aes": // 兼容模式, 安全模式
//if len(signature1) != 40 {
// err = fmt.Errorf("the length of signature mismatch, have: %d, want: 40", len(signature1))
// invalidRequestHandler.ServeInvalidRequest(w, r, err)
// return
//}
//WechatToken := wechatServer.Token()
//signature2 := util.Sign(WechatToken, timestampStr, nonce)
//if subtle.ConstantTimeCompare([]byte(signature1), []byte(signature2)) != 1 {
// err = fmt.Errorf("check signature failed, input: %s, local: %s", signature1, signature2)
// invalidRequestHandler.ServeInvalidRequest(w, r, err)
// return
//}
// 首先验证密文签名
if len(msgSignature1) != 40 {
err = fmt.Errorf("the length of msg_signature mismatch, have: %d, want: 40", len(msgSignature1))
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
var requestHttpBody RequestHttpBody
if err := xml.NewDecoder(r.Body).Decode(&requestHttpBody); err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 安全考虑验证下 ToUserName
haveToUserName := requestHttpBody.ToUserName
wantToUserName := wechatServer.Id()
if len(haveToUserName) != len(wantToUserName) {
err = fmt.Errorf("the RequestHttpBody's ToUserName mismatch, have: %s, want: %s", haveToUserName, wantToUserName)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
if subtle.ConstantTimeCompare([]byte(haveToUserName), []byte(wantToUserName)) != 1 {
err = fmt.Errorf("the RequestHttpBody's ToUserName mismatch, have: %s, want: %s", haveToUserName, wantToUserName)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
WechatToken := wechatServer.Token()
msgSignature2 := util.MsgSign(WechatToken, timestampStr, nonce, requestHttpBody.EncryptedMsg)
if subtle.ConstantTimeCompare([]byte(msgSignature1), []byte(msgSignature2)) != 1 {
err = fmt.Errorf("check signature failed, input: %s, local: %s", msgSignature1, msgSignature2)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 验证签名成功, 解密
EncryptedMsgBytes, err := base64.StdEncoding.DecodeString(requestHttpBody.EncryptedMsg)
if err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
WechatAppId := wechatServer.AppId()
AESKey := wechatServer.CurrentAESKey()
Random, RawMsgXML, err := util.AESDecryptMsg(EncryptedMsgBytes, WechatAppId, AESKey)
if err != nil {
// 尝试用上一次的 AESKey 来解密
LastAESKey := wechatServer.LastAESKey()
if bytes.Equal(zeroAESKey[:], LastAESKey[:]) || bytes.Equal(AESKey[:], LastAESKey[:]) {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
AESKey = LastAESKey // NOTE
Random, RawMsgXML, err = util.AESDecryptMsg(EncryptedMsgBytes, WechatAppId, AESKey)
if err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
}
// 解密成功, 解析 MixedMessage
var MixedMsg MixedMessage
if err = xml.Unmarshal(RawMsgXML, &MixedMsg); err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 安全考虑再次验证 ToUserName
if haveToUserName != MixedMsg.ToUserName {
err = fmt.Errorf("the RequestHttpBody's ToUserName(==%s) mismatch the MixedMessage's ToUserName(==%s)", haveToUserName, MixedMsg.ToUserName)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 成功, 交给 MessageHandler
r := &Request{
HttpRequest: r,
Signature: signature1,
TimeStamp: timestamp,
Nonce: nonce,
RawMsgXML: RawMsgXML,
MixedMsg: &MixedMsg,
MsgSignature: msgSignature1,
EncryptType: encryptType,
AESKey: AESKey,
Random: Random,
WechatId: wantToUserName,
WechatToken: WechatToken,
WechatAppId: WechatAppId,
}
wechatServer.MessageHandler().ServeMessage(w, r)
case "", "raw": // 明文模式
// 首先验证签名
if len(signature1) != 40 {
err = fmt.Errorf("the length of signature mismatch, have: %d, want: 40", len(signature1))
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
WechatToken := wechatServer.Token()
signature2 := util.Sign(WechatToken, timestampStr, nonce)
if subtle.ConstantTimeCompare([]byte(signature1), []byte(signature2)) != 1 {
err = fmt.Errorf("check signature failed, input: %s, local: %s", signature1, signature2)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 验证签名成功, 解析 MixedMessage
RawMsgXML, err := ioutil.ReadAll(r.Body)
if err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
var MixedMsg MixedMessage
if err := xml.Unmarshal(RawMsgXML, &MixedMsg); err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 安全考虑验证 ToUserName
haveToUserName := MixedMsg.ToUserName
wantToUserName := wechatServer.Id()
if len(haveToUserName) != len(wantToUserName) {
err = fmt.Errorf("the message's ToUserName mismatch, have: %s, want: %s", haveToUserName, wantToUserName)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
if subtle.ConstantTimeCompare([]byte(haveToUserName), []byte(wantToUserName)) != 1 {
err = fmt.Errorf("the message's ToUserName mismatch, have: %s, want: %s", haveToUserName, wantToUserName)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
// 成功, 交给 MessageHandler
r := &Request{
HttpRequest: r,
Signature: signature1,
TimeStamp: timestamp,
Nonce: nonce,
RawMsgXML: RawMsgXML,
MixedMsg: &MixedMsg,
WechatId: wantToUserName,
WechatToken: WechatToken,
WechatAppId: wechatServer.AppId(),
}
wechatServer.MessageHandler().ServeMessage(w, r)
default: // 未知的加密类型
err := errors.New("unknown encrypt_type: " + encryptType)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
case "GET": // 首次验证
signature1, timestamp, nonce, echostr, err := parseGetURLQuery(urlValues)
if err != nil {
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
if len(signature1) != 40 {
err = fmt.Errorf("the length of signature mismatch, have: %d, want: 40", len(signature1))
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
signature2 := util.Sign(wechatServer.Token(), timestamp, nonce)
if subtle.ConstantTimeCompare([]byte(signature1), []byte(signature2)) != 1 {
err = fmt.Errorf("check signature failed, input: %s, local: %s", signature1, signature2)
invalidRequestHandler.ServeInvalidRequest(w, r, err)
return
}
io.WriteString(w, echostr)
}
}