crypto: add a basic KMS implementation (#6161)

This commit adds a basic KMS implementation for an
operator-specified SSE-S3 master key. The master key
is wrapped as KMS such that using SSE-S3 with master key
and SSE-S3 with KMS can use the same code.

Bindings for a remote / true KMS (like hashicorp vault)
will be added later on.
master
Andreas Auernhammer 6 years ago committed by kannappanr
parent 0c9f4c9092
commit 6c93c60424
  1. 6
      cmd/crypto/error.go
  2. 6
      cmd/crypto/key.go
  3. 139
      cmd/crypto/kms.go
  4. 84
      cmd/crypto/kms_test.go

@ -28,3 +28,9 @@ var (
// is not supported.
ErrInvalidEncryptionMethod = errors.New("The encryption method is not supported")
)
var (
// errOutOfEntropy indicates that the a source of randomness (PRNG) wasn't able
// to produce enough random data. This is fatal error and should cause a panic.
errOutOfEntropy = errors.New("Unable to read enough randomness from the system")
)

@ -43,13 +43,13 @@ func GenerateKey(extKey [32]byte, random io.Reader) (key ObjectKey) {
}
var nonce [32]byte
if _, err := io.ReadFull(random, nonce[:]); err != nil {
logger.CriticalIf(context.Background(), errors.New("Unable to read enough randomness from the system"))
logger.CriticalIf(context.Background(), errOutOfEntropy)
}
sha := sha256.New()
sha.Write(extKey[:])
sha.Write(nonce[:])
sha.Sum(key[:0])
return
return key
}
// SealedKey represents a sealed object key. It can be stored
@ -126,5 +126,5 @@ func (key ObjectKey) DerivePartKey(id uint32) (partKey [32]byte) {
mac := hmac.New(sha256.New, key[:])
mac.Write(bin[:])
mac.Sum(partKey[:0])
return
return partKey
}

@ -0,0 +1,139 @@
// Minio Cloud Storage, (C) 2015, 2016, 2017, 2018 Minio, Inc.
//
// 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 crypto
import (
"bytes"
"context"
"crypto/hmac"
"crypto/rand"
"errors"
"fmt"
"io"
"sort"
"github.com/minio/minio/cmd/logger"
sha256 "github.com/minio/sha256-simd"
"github.com/minio/sio"
)
// Context is a list of key-value pairs cryptographically
// associated with a certain object.
type Context map[string]string
// WriteTo writes the context in a canonical from to w.
// It returns the number of bytes and the first error
// encounter during writing to w, if any.
//
// WriteTo sorts the context keys and writes the sorted
// key-value pairs as canonical JSON object to w.
func (c Context) WriteTo(w io.Writer) (n int64, err error) {
sortedKeys := make(sort.StringSlice, 0, len(c))
for k := range c {
sortedKeys = append(sortedKeys, k)
}
sort.Sort(sortedKeys)
nn, err := io.WriteString(w, "{")
if err != nil {
return n + int64(nn), err
}
n += int64(nn)
for i, k := range sortedKeys {
s := fmt.Sprintf("\"%s\":\"%s\",", k, c[k])
if i == len(sortedKeys)-1 {
s = s[:len(s)-1] // remove last ','
}
nn, err = io.WriteString(w, s)
if err != nil {
return n + int64(nn), err
}
n += int64(nn)
}
nn, err = io.WriteString(w, "}")
return n + int64(nn), err
}
// KMS represents an active and authenticted connection
// to a Key-Management-Service. It supports generating
// data key generation and unsealing of KMS-generated
// data keys.
type KMS interface {
// GenerateKey generates a new random data key using
// the master key referenced by the keyID. It returns
// the plaintext key and the sealed plaintext key
// on success.
//
// The context is cryptographically bound to the
// generated key. The same context must be provided
// again to unseal the generated key.
GenerateKey(keyID string, context Context) (key, sealedKey []byte, err error)
// UnsealKey unseals the sealedKey using the master key
// referenced by the keyID. The provided context must
// match the context used to generate the sealed key.
UnsealKey(keyID string, sealedKey []byte, context Context) (key []byte, err error)
}
type masterKeyKMS struct {
masterKey [32]byte
}
// NewKMS returns a basic KMS implementation from a single 256 bit master key.
//
// The KMS accepts any keyID but binds the keyID and context cryptographically
// to the generated keys.
func NewKMS(key [32]byte) KMS { return &masterKeyKMS{masterKey: key} }
func (kms *masterKeyKMS) GenerateKey(keyID string, ctx Context) (key, sealedKey []byte, err error) {
key = make([]byte, 32)
if _, err = io.ReadFull(rand.Reader, key); err != nil {
logger.CriticalIf(context.Background(), errOutOfEntropy)
}
var (
buffer bytes.Buffer
derivedKey = kms.deriveKey(keyID, ctx)
)
if n, err := sio.Encrypt(&buffer, bytes.NewReader(key), sio.Config{Key: derivedKey[:]}); err != nil || n != 64 {
logger.CriticalIf(context.Background(), errors.New("KMS: unable to encrypt data key"))
}
sealedKey = buffer.Bytes()
return key, sealedKey, nil
}
func (kms *masterKeyKMS) UnsealKey(keyID string, sealedKey []byte, ctx Context) (key []byte, err error) {
var (
buffer bytes.Buffer
derivedKey = kms.deriveKey(keyID, ctx)
)
if n, err := sio.Decrypt(&buffer, bytes.NewReader(sealedKey), sio.Config{Key: derivedKey[:]}); err != nil || n != 32 {
return nil, err // TODO(aead): upgrade sio to use sio.Error
}
key = buffer.Bytes()
return key, nil
}
func (kms *masterKeyKMS) deriveKey(keyID string, context Context) (key [32]byte) {
if context == nil {
context = Context{}
}
mac := hmac.New(sha256.New, kms.masterKey[:])
mac.Write([]byte(keyID))
context.WriteTo(mac)
mac.Sum(key[:0])
return key
}

@ -0,0 +1,84 @@
// Minio Cloud Storage, (C) 2015, 2016, 2017, 2018 Minio, Inc.
//
// 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 crypto
import (
"bytes"
"path"
"strings"
"testing"
)
var masterKeyKMSTests = []struct {
GenKeyID, UnsealKeyID string
GenContext, UnsealContext Context
ShouldFail bool
}{
{GenKeyID: "", UnsealKeyID: "", GenContext: Context{}, UnsealContext: nil, ShouldFail: false}, // 0
{GenKeyID: "ac47be7f", UnsealKeyID: "ac47be7f", GenContext: Context{}, UnsealContext: Context{}, ShouldFail: false}, // 1
{GenKeyID: "ac47be7f", UnsealKeyID: "ac47be7f", GenContext: Context{"bucket": "object"}, UnsealContext: Context{"bucket": "object"}, ShouldFail: false}, // 2
{GenKeyID: "", UnsealKeyID: "", GenContext: Context{"bucket": path.Join("bucket", "object")}, UnsealContext: Context{"bucket": path.Join("bucket", "object")}, ShouldFail: false}, // 3
{GenKeyID: "", UnsealKeyID: "", GenContext: Context{"a": "a", "0": "0", "b": "b"}, UnsealContext: Context{"b": "b", "a": "a", "0": "0"}, ShouldFail: false}, // 4
{GenKeyID: "ac47be7f", UnsealKeyID: "ac47be7e", GenContext: Context{}, UnsealContext: Context{}, ShouldFail: true}, // 5
{GenKeyID: "ac47be7f", UnsealKeyID: "ac47be7f", GenContext: Context{"bucket": "object"}, UnsealContext: Context{"Bucket": "object"}, ShouldFail: true}, // 6
{GenKeyID: "", UnsealKeyID: "", GenContext: Context{"bucket": path.Join("bucket", "Object")}, UnsealContext: Context{"bucket": path.Join("bucket", "object")}, ShouldFail: true}, // 7
{GenKeyID: "", UnsealKeyID: "", GenContext: Context{"a": "a", "0": "1", "b": "b"}, UnsealContext: Context{"b": "b", "a": "a", "0": "0"}, ShouldFail: true}, // 8
}
func TestMasterKeyKMS(t *testing.T) {
kms := NewKMS([32]byte{})
for i, test := range masterKeyKMSTests {
key, sealedKey, err := kms.GenerateKey(test.GenKeyID, test.GenContext)
if err != nil {
t.Errorf("Test %d: KMS failed to generate key: %v", i, err)
}
unsealedKey, err := kms.UnsealKey(test.UnsealKeyID, sealedKey, test.UnsealContext)
if err != nil && !test.ShouldFail {
t.Errorf("Test %d: KMS failed to unseal the generated key: %v", i, err)
}
if err == nil && test.ShouldFail {
t.Errorf("Test %d: KMS unsealed the generated successfully but should have failed", i)
}
if !test.ShouldFail && !bytes.Equal(key, unsealedKey) {
t.Errorf("Test %d: The generated and unsealed key differ", i)
}
}
}
var contextWriteToTests = []struct {
Context Context
ExpectedJSON string
}{
{Context: Context{}, ExpectedJSON: "{}"}, // 0
{Context: Context{"a": "b"}, ExpectedJSON: `{"a":"b"}`}, // 1
{Context: Context{"a": "b", "c": "d"}, ExpectedJSON: `{"a":"b","c":"d"}`}, // 2
{Context: Context{"c": "d", "a": "b"}, ExpectedJSON: `{"a":"b","c":"d"}`}, // 3
{Context: Context{"0": "1", "-": "2", ".": "#"}, ExpectedJSON: `{"-":"2",".":"#","0":"1"}`}, // 4
}
func TestContextWriteTo(t *testing.T) {
for i, test := range contextWriteToTests {
var jsonContext strings.Builder
if _, err := test.Context.WriteTo(&jsonContext); err != nil {
t.Errorf("Test %d: Failed to encode context: %v", i, err)
continue
}
if s := jsonContext.String(); s != test.ExpectedJSON {
t.Errorf("Test %d: JSON representation differ - got: '%s' want: '%s'", i, s, test.ExpectedJSON)
}
}
}
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