engine/tpi/wechat.go

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2024-02-11 01:31:01 +08:00
package tpi
import (
"crypto/aes"
"crypto/cipher"
"encoding/base64"
"errors"
)
func WeChat_Decrypt(sessionKey, encryptedData, iv string) (string, error) {
aesKey, err := base64.StdEncoding.DecodeString(sessionKey)
if err != nil {
return "", err
}
cipherText, err := base64.StdEncoding.DecodeString(encryptedData)
if err != nil {
return "", err
}
ivBytes, err := base64.StdEncoding.DecodeString(iv)
if err != nil {
return "", err
}
block, err := aes.NewCipher(aesKey)
if err != nil {
return "", err
}
mode := cipher.NewCBCDecrypter(block, ivBytes)
mode.CryptBlocks(cipherText, cipherText)
cipherText, err = WeChat_Pkcs7Unpad(cipherText, block.BlockSize())
if err != nil {
return "", err
}
return string(cipherText), nil
}
// pkcs7Unpad returns slice of the original data without padding
func WeChat_Pkcs7Unpad(data []byte, blockSize int) ([]byte, error) {
var (
// ErrInvalidBlockSize block size不合法
ErrInvalidBlockSize = errors.New("invalid block size")
// ErrInvalidPKCS7Data PKCS7数据不合法
ErrInvalidPKCS7Data = errors.New("invalid PKCS7 data")
// ErrInvalidPKCS7Padding 输入padding失败
ErrInvalidPKCS7Padding = errors.New("invalid padding on input")
)
if blockSize <= 0 {
return nil, ErrInvalidBlockSize
}
if len(data)%blockSize != 0 || len(data) == 0 {
return nil, ErrInvalidPKCS7Data
}
c := data[len(data)-1]
n := int(c)
if n == 0 || n > len(data) {
return nil, ErrInvalidPKCS7Padding
}
for i := 0; i < n; i++ {
if data[len(data)-n+i] != c {
return nil, ErrInvalidPKCS7Padding
}
}
return data[:len(data)-n], nil
}