151 lines
3.7 KiB
Go
151 lines
3.7 KiB
Go
package crypto
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/sha1"
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"encoding/base64"
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)
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const (
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KEY_SIZE = 16 // AES-128, 16 bytes
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)
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// Encrypt encrypts the given data using AES encryption in ECB mode with PKCS5 padding
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func WestDexEncrypt(data, secretKey string) (string, error) {
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key := generateAESKey(KEY_SIZE*8, []byte(secretKey))
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ciphertext, err := aesEncrypt([]byte(data), key)
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if err != nil {
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return "", err
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}
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return base64.StdEncoding.EncodeToString(ciphertext), nil
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}
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// Decrypt decrypts the given base64-encoded string using AES encryption in ECB mode with PKCS5 padding
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func WestDexDecrypt(encodedData, secretKey string) ([]byte, error) {
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ciphertext, err := base64.StdEncoding.DecodeString(encodedData)
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if err != nil {
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return nil, err
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}
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key := generateAESKey(KEY_SIZE*8, []byte(secretKey))
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plaintext, err := aesDecrypt(ciphertext, key)
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if err != nil {
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return nil, err
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}
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return plaintext, nil
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}
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// generateAESKey generates a key for AES encryption using a SHA-1 based PRNG
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func generateAESKey(length int, password []byte) []byte {
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h := sha1.New()
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h.Write(password)
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state := h.Sum(nil)
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keyBytes := make([]byte, 0, length/8)
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for len(keyBytes) < length/8 {
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h := sha1.New()
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h.Write(state)
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state = h.Sum(nil)
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keyBytes = append(keyBytes, state...)
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}
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return keyBytes[:length/8]
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}
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// aesEncrypt encrypts plaintext using AES in ECB mode with PKCS5 padding
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func aesEncrypt(plaintext, key []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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paddedPlaintext := pkcs5Padding(plaintext, block.BlockSize())
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ciphertext := make([]byte, len(paddedPlaintext))
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mode := newECBEncrypter(block)
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mode.CryptBlocks(ciphertext, paddedPlaintext)
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return ciphertext, nil
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}
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// aesDecrypt decrypts ciphertext using AES in ECB mode with PKCS5 padding
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func aesDecrypt(ciphertext, key []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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plaintext := make([]byte, len(ciphertext))
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mode := newECBDecrypter(block)
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mode.CryptBlocks(plaintext, ciphertext)
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return pkcs5Unpadding(plaintext), nil
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}
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// pkcs5Padding pads the input to a multiple of the block size using PKCS5 padding
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func pkcs5Padding(src []byte, blockSize int) []byte {
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padding := blockSize - len(src)%blockSize
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padtext := bytes.Repeat([]byte{byte(padding)}, padding)
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return append(src, padtext...)
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}
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// pkcs5Unpadding removes PKCS5 padding from the input
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func pkcs5Unpadding(src []byte) []byte {
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length := len(src)
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unpadding := int(src[length-1])
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return src[:(length - unpadding)]
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}
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// ECB mode encryption/decryption
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type ecb struct {
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b cipher.Block
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blockSize int
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}
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func newECB(b cipher.Block) *ecb {
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return &ecb{
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b: b,
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blockSize: b.BlockSize(),
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}
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}
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type ecbEncrypter ecb
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func newECBEncrypter(b cipher.Block) cipher.BlockMode {
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return (*ecbEncrypter)(newECB(b))
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}
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func (x *ecbEncrypter) BlockSize() int { return x.blockSize }
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func (x *ecbEncrypter) CryptBlocks(dst, src []byte) {
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if len(src)%x.blockSize != 0 {
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panic("crypto/cipher: input not full blocks")
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}
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if len(dst) < len(src) {
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panic("crypto/cipher: output smaller than input")
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}
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for len(src) > 0 {
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x.b.Encrypt(dst, src[:x.blockSize])
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src = src[x.blockSize:]
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dst = dst[x.blockSize:]
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}
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}
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type ecbDecrypter ecb
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func newECBDecrypter(b cipher.Block) cipher.BlockMode {
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return (*ecbDecrypter)(newECB(b))
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}
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func (x *ecbDecrypter) BlockSize() int { return x.blockSize }
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func (x *ecbDecrypter) CryptBlocks(dst, src []byte) {
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if len(src)%x.blockSize != 0 {
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panic("crypto/cipher: input not full blocks")
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}
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if len(dst) < len(src) {
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panic("crypto/cipher: output smaller than input")
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}
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for len(src) > 0 {
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x.b.Decrypt(dst, src[:x.blockSize])
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src = src[x.blockSize:]
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dst = dst[x.blockSize:]
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}
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}
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