186 lines
4.7 KiB
Go
186 lines
4.7 KiB
Go
package fqapi
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"math/big"
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)
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// CM 加密管理器
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type CM struct {
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bigC *big.Int // 大素数C
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bigB int64 // 底数B
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arryD []byte // 固定密钥
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thisD [2]*big.Int // 密钥对(私钥, 公钥)
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thisC []byte // 随机IV
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}
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// NewCM 创建新的CM实例
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func NewCM() *CM {
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// 大素数C
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bigCStr := "2410312426921032588552076022197566074856950548502459942654116941958108831682612228890093858261341614673227141477904012196503648957050582631942730706805009223062734745341073406696246014589361659774041027169249453200378729434170325843778659198143763193776859869524088940195577346119843545301547043747207749969763750084308926339295559968882457872412993810129130294592999947926365264059284647209730384947211681434464714438488520940127459844288859336526896320919633919"
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bigC := new(big.Int)
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bigC.SetString(bigCStr, 10)
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// 固定密钥（base64解码）
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arryD, _ := base64.StdEncoding.DecodeString("rCXGfd2POMGzeiNIgo4iLg==")
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return &CM{
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bigC: bigC,
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bigB: 2,
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arryD: arryD,
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}
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}
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// generateKeyPair 生成密钥对
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func (cm *CM) generateKeyPair() [2]*big.Int {
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// 生成随机私钥
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randomBytes := make([]byte, 32)
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rand.Read(randomBytes)
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x := new(big.Int).SetBytes(randomBytes)
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x = x.Mod(x, new(big.Int).Sub(cm.bigC, big.NewInt(1)))
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// 计算公钥: y = b^x mod c
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y := new(big.Int).Exp(big.NewInt(cm.bigB), x, cm.bigC)
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cm.thisD = [2]*big.Int{x, y}
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return cm.thisD
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}
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// pairToBytes 将公钥转换为字节数组
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func (cm *CM) pairToBytes(keyPair [2]*big.Int) []byte {
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return keyPair[1].Bytes()
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}
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// randIV 生成随机IV
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func (cm *CM) randIV() []byte {
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iv := make([]byte, 16)
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rand.Read(iv)
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return iv
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}
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// encodeAES AES-CBC加密
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func (cm *CM) encodeAES(key, iv, data []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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// PKCS7填充
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padding := aes.BlockSize - len(data)%aes.BlockSize
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padText := make([]byte, padding)
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for i := range padText {
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padText[i] = byte(padding)
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}
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paddedData := append(data, padText...)
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ciphertext := make([]byte, len(paddedData))
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mode := cipher.NewCBCEncrypter(block, iv)
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mode.CryptBlocks(ciphertext, paddedData)
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return ciphertext, nil
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}
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// decodeAES AES-CBC解密
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func (cm *CM) decodeAES(key, iv, data []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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mode := cipher.NewCBCDecrypter(block, iv)
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decrypted := make([]byte, len(data))
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mode.CryptBlocks(decrypted, data)
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// 移除PKCS7填充
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padding := int(decrypted[len(decrypted)-1])
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if padding > len(decrypted) || padding > aes.BlockSize {
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return nil, fmt.Errorf("无效的填充")
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}
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return decrypted[:len(decrypted)-padding], nil
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}
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// ClientHandshake 客户端握手，生成请求头y
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func (cm *CM) ClientHandshake() string {
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keyPair := cm.generateKeyPair()
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cm.thisC = cm.randIV()
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publicKeyBytes := cm.pairToBytes(keyPair)
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encrypted, _ := cm.encodeAES(cm.arryD, cm.thisC, publicKeyBytes)
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combined := append(cm.thisC, encrypted...)
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return base64.StdEncoding.EncodeToString(combined)
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}
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// decryptF 解密函数
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func (cm *CM) decryptF(peerPublicKey []byte, keyPair [2]*big.Int, iv, data []byte) ([]byte, error) {
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x := keyPair[0]
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// 计算共享密钥: shared_secret = peer_public_key^x mod c
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peerPubInt := new(big.Int).SetBytes(peerPublicKey)
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sharedSecret := new(big.Int).Exp(peerPubInt, x, cm.bigC)
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key := sharedSecret.Bytes()
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// 确保key长度为32字节
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if len(key) < 32 {
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// 前面补0
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paddedKey := make([]byte, 32)
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copy(paddedKey[32-len(key):], key)
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key = paddedKey
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} else if len(key) > 32 {
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key = key[:32]
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}
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return cm.decodeAES(key, iv, data)
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}
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// Decrypt 解密响应内容
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func (cm *CM) Decrypt(c, y, content string) (string, error) {
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// c 应该为 "1" 表示启用加密
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// y 是服务器返回的公钥
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// content 是加密的内容
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if c != "1" || y == "" {
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return content, nil
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}
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// 解码content
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contentDecoded, err := base64.StdEncoding.DecodeString(content)
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if err != nil {
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return "", err
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}
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if len(contentDecoded) < 16 {
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return "", fmt.Errorf("内容太短")
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}
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// 提取IV和数据
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iv := contentDecoded[:16]
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data := contentDecoded[16:]
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// 解码服务器公钥
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peerPublicKey, err := base64.StdEncoding.DecodeString(y)
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if err != nil {
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return "", err
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}
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// 检查密钥对是否已初始化
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if cm.thisD[0] == nil {
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return "", fmt.Errorf("密钥对未初始化")
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}
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// 解密
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decrypted, err := cm.decryptF(peerPublicKey, cm.thisD, iv, data)
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if err != nil {
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return "", err
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}
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return string(decrypted), nil
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}
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