forked from pulumi/pulumi
/
crypt.go
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/
crypt.go
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// Copyright 2016-2018, Pulumi Corporation.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package config
import (
"crypto/aes"
"crypto/cipher"
cryptorand "crypto/rand"
"crypto/sha256"
"encoding/base64"
"fmt"
"strings"
"github.com/pkg/errors"
"github.com/pulumi/pulumi/pkg/util/contract"
"golang.org/x/crypto/pbkdf2"
)
// Encrypter encrypts plaintext into its encrypted ciphertext.
type Encrypter interface {
EncryptValue(plaintext string) (string, error)
}
// Decrypter decrypts encrypted ciphertext to its plaintext representation.
type Decrypter interface {
DecryptValue(ciphertext string) (string, error)
}
// Crypter can both encrypt and decrypt values.
type Crypter interface {
Encrypter
Decrypter
}
// A nopDecrypter simply returns the ciphertext as-is.
type nopDecrypter struct{}
var NopDecrypter Decrypter = nopDecrypter{}
func (nopDecrypter) DecryptValue(ciphertext string) (string, error) {
return ciphertext, nil
}
// NewBlindingDecrypter returns a Decrypter that instead of decrypting data, just returns "[secret]", it can
// be used when you want to display configuration information to a user but don't want to prompt for a password
// so secrets will not be decrypted.
func NewBlindingDecrypter() Decrypter {
return blindingDecrypter{}
}
type blindingDecrypter struct{}
func (b blindingDecrypter) DecryptValue(ciphertext string) (string, error) {
return "[secret]", nil
}
// NewPanicCrypter returns a new config crypter that will panic if used.
func NewPanicCrypter() Crypter {
return &panicCrypter{}
}
type panicCrypter struct{}
func (p panicCrypter) EncryptValue(plaintext string) (string, error) {
panic("attempt to encrypt value")
}
func (p panicCrypter) DecryptValue(ciphertext string) (string, error) {
panic("attempt to decrypt value")
}
// NewSymmetricCrypter creates a crypter that encrypts and decrypts values using AES-256-GCM. The nonce is stored with
// the value itself as a pair of base64 values separated by a colon and a version tag `v1` is prepended.
func NewSymmetricCrypter(key []byte) Crypter {
contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
return &symmetricCrypter{key}
}
// NewSymmetricCrypterFromPassphrase uses a passphrase and salt to generate a key, and then returns a crypter using it.
func NewSymmetricCrypterFromPassphrase(phrase string, salt []byte) Crypter {
// Generate a key using PBKDF2 to slow down attempts to crack it. 1,000,000 iterations was chosen because it
// took a little over a second on an i7-7700HQ Quad Core procesor
key := pbkdf2.Key([]byte(phrase), salt, 1000000, SymmetricCrypterKeyBytes, sha256.New)
return NewSymmetricCrypter(key)
}
// SymmetricCrypterKeyBytes is the required key size in bytes.
const SymmetricCrypterKeyBytes = 32
type symmetricCrypter struct {
key []byte
}
func (s symmetricCrypter) EncryptValue(value string) (string, error) {
secret, nonce := encryptAES256GCGM(value, s.key)
return fmt.Sprintf("v1:%s:%s",
base64.StdEncoding.EncodeToString(nonce), base64.StdEncoding.EncodeToString(secret)), nil
}
func (s symmetricCrypter) DecryptValue(value string) (string, error) {
vals := strings.Split(value, ":")
if len(vals) != 3 {
return "", errors.New("bad value")
}
if vals[0] != "v1" {
return "", errors.New("unknown value version")
}
nonce, err := base64.StdEncoding.DecodeString(vals[1])
if err != nil {
return "", errors.Wrap(err, "bad value")
}
enc, err := base64.StdEncoding.DecodeString(vals[2])
if err != nil {
return "", errors.Wrap(err, "bad value")
}
return decryptAES256GCM(enc, s.key, nonce)
}
// encryptAES256GCGM returns the ciphertext and the generated nonce
func encryptAES256GCGM(plaintext string, key []byte) ([]byte, []byte) {
contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
nonce := make([]byte, 12)
_, err := cryptorand.Read(nonce)
contract.Assertf(err == nil, "could not read from system random source")
block, err := aes.NewCipher(key)
contract.AssertNoError(err)
aesgcm, err := cipher.NewGCM(block)
contract.AssertNoError(err)
msg := aesgcm.Seal(nil, nonce, []byte(plaintext), nil)
return msg, nonce
}
func decryptAES256GCM(ciphertext []byte, key []byte, nonce []byte) (string, error) {
contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
block, err := aes.NewCipher(key)
contract.AssertNoError(err)
aesgcm, err := cipher.NewGCM(block)
contract.AssertNoError(err)
msg, err := aesgcm.Open(nil, nonce, ciphertext, nil)
return string(msg), err
}