storj/pkg/client/crypto.go

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// Copyright (C) 2018 Storj Labs, Inc.
// See LICENSE for copying information.
package client
import (
"crypto/aes"
"crypto/cipher"
"crypto/hmac"
"crypto/sha256"
"crypto/sha512"
"encoding/base64"
"encoding/hex"
bip39 "github.com/tyler-smith/go-bip39"
)
const (
bucketNameMagic = "398734aab3c4c30c9f22590e83a95f7e43556a45fc2b3060e0c39fde31f50272"
gcmDigestSize = 16
ivSize = 32
)
var bucketMetaMagic = []byte{
66, 150, 71, 16, 50, 114, 88, 160, 163, 35, 154, 65, 162, 213, 226, 215,
70, 138, 57, 61, 52, 19, 210, 170, 38, 164, 162, 200, 86, 201, 2, 81}
func sha256Sum(str string) string {
checksum := sha256.Sum256([]byte(str))
return hex.EncodeToString(checksum[:])
}
func mnemonicToSeed(mnemonic string) (string, error) {
seed, err := bip39.NewSeedWithErrorChecking(mnemonic, "")
if err != nil {
return "", err
}
return hex.EncodeToString(seed), nil
}
func getDeterministicKey(key, id string) (string, error) {
input, err := hex.DecodeString(key + id)
if err != nil {
return "", err
}
checksum := sha512.Sum512(input)
str := hex.EncodeToString(checksum[:])
return str[0 : len(str)/2], nil
}
func generateBucketKey(mnemonic, bucketID string) (string, error) {
seed, err := mnemonicToSeed(mnemonic)
if err != nil {
return "", err
}
return getDeterministicKey(seed, bucketNameMagic)
}
func decryptMeta(encryptedName string, key []byte) ([]byte, error) {
nameBase64, err := base64.StdEncoding.DecodeString(encryptedName)
if err != nil {
return []byte{}, err
}
if len(nameBase64) <= gcmDigestSize+ivSize {
return []byte{}, CryptoError.New("Invalid encrypted name")
}
block, err := aes.NewCipher(key)
if err != nil {
return []byte{}, err
}
aesgcm, err := cipher.NewGCMWithNonceSize(block, ivSize)
if err != nil {
return []byte{}, err
}
digest := nameBase64[:gcmDigestSize]
iv := nameBase64[gcmDigestSize : gcmDigestSize+ivSize]
cipherText := nameBase64[gcmDigestSize+ivSize:]
return aesgcm.Open(nil, iv, append(cipherText, digest...), nil)
}
func decryptBucketName(name, mnemonic string) (string, error) {
bucketKey, err := generateBucketKey(mnemonic, bucketNameMagic)
if err != nil {
return "", err
}
bucketKeyHex, err := hex.DecodeString(bucketKey)
if err != nil {
return "", err
}
sig := hmac.New(sha512.New, bucketKeyHex)
_, err = sig.Write(bucketMetaMagic)
if err != nil {
return "", err
}
hmacSHA512 := sig.Sum(nil)
key := hmacSHA512[0 : len(hmacSHA512)/2]
decryptedName, err := decryptMeta(name, key)
if err != nil {
return "", err
}
return string(decryptedName), nil
}