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Simple AES CBC encryptor and decryptor in Golang
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| package main | |
| import ( | |
| "os" | |
| "flag" | |
| "fmt" | |
| "syscall" | |
| "io/ioutil" | |
| "crypto/rand" | |
| "crypto/cipher" | |
| "crypto/aes" | |
| "encoding/hex" | |
| ) | |
| var encrypt, decrypt, key, iv string | |
| func init() { | |
| flag.StringVar(&encrypt, "e", "", "Encrypt the file") | |
| flag.StringVar(&decrypt, "d", "", "Decrypt the file") | |
| flag.StringVar(&key, "k", "", "Key used to encrypt") | |
| flag.StringVar(&iv, "i", "", "IV used to CBC") | |
| flag.Parse() | |
| } | |
| func readFileBytes(filePath string) ([]byte) { | |
| data, err := ioutil.ReadFile(filePath) | |
| checkErr(err) | |
| return data | |
| } | |
| func writeFileBytes(filePath string, data []byte) { | |
| ioutil.WriteFile(filePath, data, 0644) | |
| } | |
| func encryptAes(input []byte , key []byte , iv []byte ) ([]byte) { | |
| block, err := aes.NewCipher(key) | |
| checkErr(err) | |
| for i := len(input); len(input) % aes.BlockSize != 0; i++ { | |
| input = append(input, 0) | |
| } | |
| cbcEncryptor := cipher.NewCBCEncrypter(block, iv) | |
| ciphered := make([]byte, aes.BlockSize + len(input)) | |
| cbcEncryptor.CryptBlocks(ciphered, input) | |
| return ciphered | |
| } | |
| func decryptAes(input []byte, key []byte, iv []byte) ([]byte) { | |
| block, err := aes.NewCipher(key) | |
| checkErr(err) | |
| cbcDecryptor := cipher.NewCBCDecrypter(block, iv) | |
| cbcDecryptor.CryptBlocks(input, input) | |
| return input; | |
| } | |
| func genRandomValue(size uint32) ([]byte) { | |
| v := make([]byte, size) | |
| rand.Read(v) | |
| return v | |
| } | |
| func main() { | |
| if len(os.Args) < 2 { | |
| flag.Usage() | |
| os.Exit(1) | |
| } | |
| var filePath string | |
| var fileBytes []byte | |
| if encrypt != "" { | |
| filePath = encrypt | |
| checkAccess(filePath) | |
| var randomKey []byte = genRandomValue(16) | |
| var iv []byte = genRandomValue(16) | |
| fileBytes = readFileBytes(filePath) | |
| encryptedInput := encryptAes(fileBytes, randomKey, iv) | |
| writeFileBytes(filePath + ".aes", encryptedInput) | |
| fmt.Printf("File encrypted\nKey: %x\nIV: %x\n", randomKey, iv) | |
| } else if decrypt != "" && iv != "" && key != "" { | |
| filePath = decrypt | |
| checkAccess(filePath) | |
| encodedKey, err := hex.DecodeString(key) | |
| checkErr(err) | |
| encodedIv, err := hex.DecodeString(iv) | |
| checkErr(err) | |
| fmt.Printf("Attempt to decrypt %s with key %x and iv %x...\n", filePath, encodedKey, encodedIv) | |
| fileBytes = readFileBytes(filePath) | |
| decryptedFile := decryptAes(fileBytes, encodedKey, encodedIv) | |
| writeFileBytes(filePath + ".dec", decryptedFile) | |
| } else { | |
| flag.Usage() | |
| } | |
| } | |
| func checkErr(err error) { | |
| if err != nil { | |
| panic(err) | |
| } | |
| } | |
| func checkAccess(filePath string) { | |
| if err := syscall.Access(filePath, syscall.O_RDONLY); err != nil { | |
| fmt.Fprintf(os.Stderr, "Unable to open file %s", filePath) | |
| os.Exit(1) | |
| } | |
| } |
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