156 lines
4.5 KiB
Go
156 lines
4.5 KiB
Go
// Copyright 2016-2018, Pulumi Corporation. All rights reserved.
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package config
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import (
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"crypto/aes"
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"crypto/cipher"
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cryptorand "crypto/rand"
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"crypto/sha256"
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"encoding/base64"
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"fmt"
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"strings"
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"github.com/pkg/errors"
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"github.com/pulumi/pulumi/pkg/util/contract"
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"golang.org/x/crypto/pbkdf2"
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)
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// Encrypter encrypts plaintext into its encrypted ciphertext.
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type Encrypter interface {
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EncryptValue(plaintext string) (string, error)
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}
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// Decrypter decrypts encrypted ciphertext to its plaintext representation.
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type Decrypter interface {
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DecryptValue(ciphertext string) (string, error)
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}
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// Crypter can both encrypt and decrypt values.
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type Crypter interface {
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Encrypter
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Decrypter
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}
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// A nopDecrypter simply returns the ciphertext as-is.
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type nopDecrypter struct{}
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var NopDecrypter Decrypter = nopDecrypter{}
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func (nopDecrypter) DecryptValue(ciphertext string) (string, error) {
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return ciphertext, nil
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}
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// NewBlindingDecrypter returns a Decrypter that instead of decrypting data, just returns "[secret]", it can
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// be used when you want to display configuration information to a user but don't want to prompt for a password
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// so secrets will not be decrypted.
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func NewBlindingDecrypter() Decrypter {
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return blindingDecrypter{}
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}
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type blindingDecrypter struct{}
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func (b blindingDecrypter) DecryptValue(ciphertext string) (string, error) {
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return "[secret]", nil
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}
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// NewPanicCrypter returns a new config crypter that will panic if used.
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func NewPanicCrypter() Crypter {
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return &panicCrypter{}
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}
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type panicCrypter struct{}
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func (p panicCrypter) EncryptValue(plaintext string) (string, error) {
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panic("attempt to encrypt value")
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}
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func (p panicCrypter) DecryptValue(ciphertext string) (string, error) {
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panic("attempt to decrypt value")
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}
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// NewSymmetricCrypter creates a crypter that encrypts and decrypts values using AES-256-GCM. The nonce is stored with
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// the value itself as a pair of base64 values separated by a colon and a version tag `v1` is prepended.
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func NewSymmetricCrypter(key []byte) Crypter {
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contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
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return &symmetricCrypter{key}
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}
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// NewSymmetricCrypterFromPassphrase uses a passphrase and salt to generate a key, and then returns a crypter using it.
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func NewSymmetricCrypterFromPassphrase(phrase string, salt []byte) Crypter {
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// Generate a key using PBKDF2 to slow down attempts to crack it. 1,000,000 iterations was chosen because it
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// took a little over a second on an i7-7700HQ Quad Core procesor
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key := pbkdf2.Key([]byte(phrase), salt, 1000000, SymmetricCrypterKeyBytes, sha256.New)
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return NewSymmetricCrypter(key)
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}
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// SymmetricCrypterKeyBytes is the required key size in bytes.
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const SymmetricCrypterKeyBytes = 32
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type symmetricCrypter struct {
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key []byte
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}
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func (s symmetricCrypter) EncryptValue(value string) (string, error) {
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secret, nonce := encryptAES256GCGM(value, s.key)
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return fmt.Sprintf("v1:%s:%s",
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base64.StdEncoding.EncodeToString(nonce), base64.StdEncoding.EncodeToString(secret)), nil
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}
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func (s symmetricCrypter) DecryptValue(value string) (string, error) {
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vals := strings.Split(value, ":")
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if len(vals) != 3 {
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return "", errors.New("bad value")
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}
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if vals[0] != "v1" {
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return "", errors.New("unknown value version")
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}
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nonce, err := base64.StdEncoding.DecodeString(vals[1])
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if err != nil {
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return "", errors.Wrap(err, "bad value")
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}
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enc, err := base64.StdEncoding.DecodeString(vals[2])
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if err != nil {
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return "", errors.Wrap(err, "bad value")
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}
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return decryptAES256GCM(enc, s.key, nonce)
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}
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// encryptAES256GCGM returns the ciphertext and the generated nonce
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func encryptAES256GCGM(plaintext string, key []byte) ([]byte, []byte) {
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contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
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nonce := make([]byte, 12)
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_, err := cryptorand.Read(nonce)
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contract.Assertf(err == nil, "could not read from system random source")
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block, err := aes.NewCipher(key)
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contract.AssertNoError(err)
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aesgcm, err := cipher.NewGCM(block)
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contract.AssertNoError(err)
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msg := aesgcm.Seal(nil, nonce, []byte(plaintext), nil)
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return msg, nonce
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}
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func decryptAES256GCM(ciphertext []byte, key []byte, nonce []byte) (string, error) {
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contract.Requiref(len(key) == SymmetricCrypterKeyBytes, "key", "AES-256-GCM needs a 32 byte key")
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block, err := aes.NewCipher(key)
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contract.AssertNoError(err)
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aesgcm, err := cipher.NewGCM(block)
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contract.AssertNoError(err)
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msg, err := aesgcm.Open(nil, nonce, ciphertext, nil)
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return string(msg), err
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}
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