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signer: prevent possibility swap KV-entries in aes_gcm storage, fixes #17635

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This commit is contained in:
Martin Holst Swende 2018-09-12 14:45:35 +02:00
parent 517c4fc2b0
commit 321de9d86c
No known key found for this signature in database
GPG key ID: 683B438C05A5DDF0
2 changed files with 60 additions and 8 deletions
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15
signer/storage/aes_gcm_storage.go
View file

@ -63,7 +63,7 @@ func (s *AESEncryptedStorage) Put(key, value string) {
log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
return
}
ciphertext, iv, err := encrypt(s.key, []byte(value))
ciphertext, iv, err := encrypt(s.key, []byte(value), []byte(key))
if err != nil {
log.Warn("Failed to encrypt entry", "err", err)
return
@ -90,7 +90,7 @@ func (s *AESEncryptedStorage) Get(key string) string {
log.Warn("Key does not exist", "key", key)
return ""
}
entry, err := decrypt(s.key, encrypted.Iv, encrypted.CipherText)
entry, err := decrypt(s.key, encrypted.Iv, encrypted.CipherText, []byte(key))
if err != nil {
log.Warn("Failed to decrypt key", "key", key)
return ""
@ -129,7 +129,10 @@ func (s *AESEncryptedStorage) writeEncryptedStorage(creds map[string]storedCrede
return nil
}
func encrypt(key []byte, plaintext []byte) ([]byte, []byte, error) {
// encrypt encrypts plaingtext with the given key, with additionaldata
// The 'additionalData' is used to place the (plaintext) KV-store key into the V,
// to prevent the possibility to alter a K, or swap two entries in the KV store with eachother.
func encrypt(key []byte, plaintext []byte, additionalData []byte) ([]byte, []byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, nil, err
@ -142,11 +145,11 @@ func encrypt(key []byte, plaintext []byte) ([]byte, []byte, error) {
if err != nil {
return nil, nil, err
}
ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil)
ciphertext := aesgcm.Seal(nil, nonce, plaintext, additionalData)
return ciphertext, nonce, nil
}
func decrypt(key []byte, nonce []byte, ciphertext []byte) ([]byte, error) {
func decrypt(key []byte, nonce []byte, ciphertext []byte, additionalData []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
@ -155,7 +158,7 @@ func decrypt(key []byte, nonce []byte, ciphertext []byte) ([]byte, error) {
if err != nil {
return nil, err
}
plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil)
plaintext, err := aesgcm.Open(nil, nonce, ciphertext, additionalData)
if err != nil {
return nil, err
}

53
signer/storage/aes_gcm_storage_test.go
View file

@ -18,6 +18,7 @@ package storage
import (
"bytes"
"encoding/json"
"fmt"
"io/ioutil"
"testing"
@ -33,13 +34,13 @@ func TestEncryption(t *testing.T) {
key := []byte("AES256Key-32Characters1234567890")
plaintext := []byte("exampleplaintext")
c, iv, err := encrypt(key, plaintext)
c, iv, err := encrypt(key, plaintext, nil)
if err != nil {
t.Fatal(err)
}
fmt.Printf("Ciphertext %x, nonce %x\n", c, iv)
p, err := decrypt(key, iv, c)
p, err := decrypt(key, iv, c, nil)
if err != nil {
t.Fatal(err)
}
@ -113,3 +114,51 @@ func TestEnd2End(t *testing.T) {
t.Errorf("Expected bazonk->foobar, got '%v'", v)
}
}
func TestSwappedKeys(t *testing.T) {
// It should not be possible to swap the keys/values, so that
// K1:V1, K2:V2 can be swapped into K1:V2, K2:V1
log.Root().SetHandler(log.LvlFilterHandler(log.Lvl(3), log.StreamHandler(colorable.NewColorableStderr(), log.TerminalFormat(true))))
d, err := ioutil.TempDir("", "eth-encrypted-storage-test")
if err != nil {
t.Fatal(err)
}
s1 := &AESEncryptedStorage{
filename: fmt.Sprintf("%v/vault.json", d),
key: []byte("AES256Key-32Characters1234567890"),
}
s1.Put("k1", "v1")
s1.Put("k2", "v2")
// Now make a modified copy
creds := make(map[string]storedCredential)
raw, err := ioutil.ReadFile(s1.filename)
if err != nil {
t.Fatal(err)
}
if err = json.Unmarshal(raw, &creds); err != nil {
t.Fatal(err)
}
swap := func() {
// Turn it into K1:V2, K2:V2
v1, v2 := creds["k1"], creds["k2"]
creds["k2"], creds["k1"] = v1, v2
raw, err = json.Marshal(creds)
if err != nil {
t.Fatal(err)
}
if err = ioutil.WriteFile(s1.filename, raw, 0600); err != nil {
t.Fatal(err)
}
}
swap()
if v := s1.Get("k1"); v != "" {
t.Errorf("swapped value should return empty")
}
swap()
if v := s1.Get("k1"); v != "v1" {
t.Errorf("double-swapped value should work fine")
}
}