73 lines
1.8 KiB
Go
73 lines
1.8 KiB
Go
package tunnel
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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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"crypto/sha256"
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"io"
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)
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// Encrypt encrypts data and returns the encrypted data
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func Encrypt(data []byte, key string) ([]byte, error) {
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// generate a new AES cipher using our 32 byte key
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c, err := aes.NewCipher(hash(key))
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if err != nil {
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return nil, err
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}
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// gcm or Galois/Counter Mode, is a mode of operation
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// for symmetric key cryptographic block ciphers
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// - https://en.wikipedia.org/wiki/Galois/Counter_Mode
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gcm, err := cipher.NewGCM(c)
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if err != nil {
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return nil, err
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}
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// create a new byte array the size of the nonce
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// NOTE: we might use smaller nonce size in the future
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nonce := make([]byte, gcm.NonceSize())
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if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, err
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}
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// NOTE: we prepend the nonce to the payload
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// we need to do this as we need the same nonce
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// to decrypt the payload when receiving it
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return gcm.Seal(nonce, nonce, data, nil), nil
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}
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// Decrypt decrypts the payload and returns the decrypted data
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func Decrypt(data []byte, key string) ([]byte, error) {
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// generate AES cipher for decrypting the message
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c, err := aes.NewCipher(hash(key))
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if err != nil {
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return nil, err
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}
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// we use GCM to encrypt the payload
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gcm, err := cipher.NewGCM(c)
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if err != nil {
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return nil, err
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}
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nonceSize := gcm.NonceSize()
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// NOTE: we need to parse out nonce from the payload
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// we prepend the nonce to every encrypted payload
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nonce, ciphertext := data[:nonceSize], data[nonceSize:]
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plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
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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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// hash hahes the data into 32 bytes key and returns it
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// hash uses sha256 underneath to hash the supplied key
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func hash(key string) []byte {
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hasher := sha256.New()
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hasher.Write([]byte(key))
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return hasher.Sum(nil)
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}
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