mirror of https://github.com/k3s-io/k3s
Add an AEAD encrypting transformer for storing secrets encrypted at rest
Tweak the ValueTransformer interface slightly to support additional context information (to allow authenticated data to be generated by the store and passed to the transformer). Add a prefix transformer that looks for known matching prefixes and uses them. Add an AES GCM transformer that performs AEAD on the values coming in and out of the store.pull/6/head
Clayton Coleman
parent
d823a6e228
commit
f418468c87
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@ -0,0 +1,80 @@
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/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// Package aes transforms values for storage at rest using AES-GCM.
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package aes
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import (
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"crypto/cipher"
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"crypto/rand"
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"fmt"
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"k8s.io/apiserver/pkg/storage/value"
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)
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// gcm implements AEAD encryption of the provided values given a cipher.Block algorithm.
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// The authenticated data provided as part of the value.Context method must match when the same
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// value is set to and loaded from storage. In order to ensure that values cannot be copied by
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// an attacker from a location under their control, use characteristics of the storage location
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// (such as the etcd key) as part of the authenticated data.
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//
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// Because this mode requires a generated IV and IV reuse is a known weakness of AES-GCM, keys
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// must be rotated before a birthday attack becomes feasible. NIST SP 800-38D
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// (http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf) recommends using the same
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// key with random 96-bit nonces (the default nonce length) no more than 2^32 times, and
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// therefore transformers using this implementation *must* ensure they allow for frequent key
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// rotation. Future work should include investigation of AES-GCM-SIV as an alternative to
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// random nonces.
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type gcm struct {
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block cipher.Block
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}
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// NewGCMTransformer takes the given block cipher and performs encryption and decryption on the given
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// data.
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func NewGCMTransformer(block cipher.Block) value.Transformer {
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return &gcm{block: block}
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}
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func (t *gcm) TransformFromStorage(data []byte, context value.Context) ([]byte, bool, error) {
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aead, err := cipher.NewGCM(t.block)
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if err != nil {
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return nil, false, err
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}
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nonceSize := aead.NonceSize()
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if len(data) < nonceSize {
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return nil, false, fmt.Errorf("the stored data was shorter than the required size")
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}
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result, err := aead.Open(nil, data[:nonceSize], data[nonceSize:], context.AuthenticatedData())
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return result, false, err
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}
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func (t *gcm) TransformToStorage(data []byte, context value.Context) ([]byte, error) {
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aead, err := cipher.NewGCM(t.block)
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if err != nil {
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return nil, err
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}
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nonceSize := aead.NonceSize()
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result := make([]byte, nonceSize+aead.Overhead()+len(data))
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n, err := rand.Read(result[:nonceSize])
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if err != nil {
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return nil, err
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}
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if n != nonceSize {
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return nil, fmt.Errorf("unable to read sufficient random bytes")
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}
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cipherText := aead.Seal(result[nonceSize:nonceSize], result[:nonceSize], data, context.AuthenticatedData())
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return result[:nonceSize+len(cipherText)], nil
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}
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@ -0,0 +1,172 @@
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/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package aes
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"fmt"
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"testing"
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"k8s.io/apiserver/pkg/storage/value"
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)
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func TestGCMDataStable(t *testing.T) {
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block, err := aes.NewCipher([]byte("0123456789abcdef"))
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if err != nil {
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t.Fatal(err)
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}
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aead, err := cipher.NewGCM(block)
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if err != nil {
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t.Fatal(err)
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}
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// IMPORTANT: If you must fix this test, then all previously encrypted data from previously compiled versions is broken unless you hardcode the nonce size to 12
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if aead.NonceSize() != 12 {
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t.Fatalf("The underlying Golang crypto size has changed, old version of AES on disk will not be readable unless the AES implementation is changed to hardcode nonce size.")
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}
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}
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func TestGCMKeyRotation(t *testing.T) {
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testErr := fmt.Errorf("test error")
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block1, err := aes.NewCipher([]byte("abcdefghijklmnop"))
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if err != nil {
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t.Fatal(err)
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}
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block2, err := aes.NewCipher([]byte("0123456789abcdef"))
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if err != nil {
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t.Fatal(err)
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}
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context := value.DefaultContext([]byte("authenticated_data"))
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p := value.NewPrefixTransformers(testErr,
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value.PrefixTransformer{Prefix: []byte("first:"), Transformer: NewGCMTransformer(block1)},
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value.PrefixTransformer{Prefix: []byte("second:"), Transformer: NewGCMTransformer(block2)},
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)
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out, err := p.TransformToStorage([]byte("firstvalue"), context)
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if err != nil {
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t.Fatal(err)
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}
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if !bytes.HasPrefix(out, []byte("first:")) {
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t.Fatalf("unexpected prefix: %q", out)
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}
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from, stale, err := p.TransformFromStorage(out, context)
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if err != nil {
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t.Fatal(err)
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}
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if stale || !bytes.Equal([]byte("firstvalue"), from) {
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t.Fatalf("unexpected data: %t %q", stale, from)
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}
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// verify changing the context fails storage
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from, stale, err = p.TransformFromStorage(out, value.DefaultContext([]byte("incorrect_context")))
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if err == nil {
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t.Fatalf("expected unauthenticated data")
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}
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// reverse the order, use the second key
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p = value.NewPrefixTransformers(testErr,
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value.PrefixTransformer{Prefix: []byte("second:"), Transformer: NewGCMTransformer(block2)},
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value.PrefixTransformer{Prefix: []byte("first:"), Transformer: NewGCMTransformer(block1)},
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)
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from, stale, err = p.TransformFromStorage(out, context)
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if err != nil {
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t.Fatal(err)
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}
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if !stale || !bytes.Equal([]byte("firstvalue"), from) {
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t.Fatalf("unexpected data: %t %q", stale, from)
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}
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}
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func BenchmarkGCMRead_16_1024(b *testing.B) { benchmarkGCMRead(b, 16, 1024, false) }
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func BenchmarkGCMRead_32_1024(b *testing.B) { benchmarkGCMRead(b, 32, 1024, false) }
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func BenchmarkGCMRead_32_16384(b *testing.B) { benchmarkGCMRead(b, 32, 16384, false) }
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func BenchmarkGCMRead_32_16384_Stale(b *testing.B) { benchmarkGCMRead(b, 32, 16384, true) }
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func BenchmarkGCMWrite_16_1024(b *testing.B) { benchmarkGCMWrite(b, 16, 1024) }
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func BenchmarkGCMWrite_32_1024(b *testing.B) { benchmarkGCMWrite(b, 32, 1024) }
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func BenchmarkGCMWrite_32_16384(b *testing.B) { benchmarkGCMWrite(b, 32, 16384) }
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func benchmarkGCMRead(b *testing.B, keyLength int, valueLength int, stale bool) {
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block1, err := aes.NewCipher(bytes.Repeat([]byte("a"), keyLength))
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if err != nil {
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b.Fatal(err)
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}
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block2, err := aes.NewCipher(bytes.Repeat([]byte("b"), keyLength))
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if err != nil {
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b.Fatal(err)
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}
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p := value.NewPrefixTransformers(nil,
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value.PrefixTransformer{Prefix: []byte("first:"), Transformer: NewGCMTransformer(block1)},
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value.PrefixTransformer{Prefix: []byte("second:"), Transformer: NewGCMTransformer(block2)},
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)
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context := value.DefaultContext([]byte("authenticated_data"))
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v := bytes.Repeat([]byte("0123456789abcdef"), valueLength/16)
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out, err := p.TransformToStorage(v, context)
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if err != nil {
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b.Fatal(err)
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}
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// reverse the key order if stale
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if stale {
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p = value.NewPrefixTransformers(nil,
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value.PrefixTransformer{Prefix: []byte("first:"), Transformer: NewGCMTransformer(block1)},
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value.PrefixTransformer{Prefix: []byte("second:"), Transformer: NewGCMTransformer(block2)},
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)
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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from, stale, err := p.TransformFromStorage(out, context)
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if err != nil {
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b.Fatal(err)
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}
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if stale {
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b.Fatalf("unexpected data: %t %q", stale, from)
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}
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}
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b.StopTimer()
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}
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func benchmarkGCMWrite(b *testing.B, keyLength int, valueLength int) {
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block1, err := aes.NewCipher(bytes.Repeat([]byte("a"), keyLength))
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if err != nil {
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b.Fatal(err)
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}
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block2, err := aes.NewCipher(bytes.Repeat([]byte("b"), keyLength))
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if err != nil {
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b.Fatal(err)
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}
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p := value.NewPrefixTransformers(nil,
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value.PrefixTransformer{Prefix: []byte("first:"), Transformer: NewGCMTransformer(block1)},
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value.PrefixTransformer{Prefix: []byte("second:"), Transformer: NewGCMTransformer(block2)},
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)
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context := value.DefaultContext([]byte("authenticated_data"))
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v := bytes.Repeat([]byte("0123456789abcdef"), valueLength/16)
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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_, err := p.TransformToStorage(v, context)
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if err != nil {
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b.Fatal(err)
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}
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}
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b.StopTimer()
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}
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@ -0,0 +1,146 @@
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/*
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Copyright 2017 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// Package value contains methods for assisting with transformation of values in storage.
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package value
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import (
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"bytes"
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"fmt"
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"sync"
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)
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// Context is additional information that a storage transformation may need to verify the data at rest.
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type Context interface {
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// AuthenticatedData should return an array of bytes that describes the current value. If the value changes,
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// the transformer may report the value as unreadable or tampered. This may be nil if no such description exists
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// or is needed. For additional verification, set this to data that strongly identifies the value, such as
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// the key and creation version of the stored data.
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AuthenticatedData() []byte
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}
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// Transformer allows a value to be transformed before being read from or written to the underlying store. The methods
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// must be able to undo the transformation caused by the other.
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type Transformer interface {
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// TransformFromStorage may transform the provided data from its underlying storage representation or return an error.
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// Stale is true if the object on disk is stale and a write to etcd should be issued, even if the contents of the object
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// have not changed.
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TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error)
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// TransformToStorage may transform the provided data into the appropriate form in storage or return an error.
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TransformToStorage(data []byte, context Context) (out []byte, err error)
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}
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type identityTransformer struct{}
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// IdentityTransformer performs no transformation of the provided data.
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var IdentityTransformer Transformer = identityTransformer{}
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func (identityTransformer) TransformFromStorage(b []byte, ctx Context) ([]byte, bool, error) {
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return b, false, nil
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}
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func (identityTransformer) TransformToStorage(b []byte, ctx Context) ([]byte, error) {
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return b, nil
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}
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// DefaultContext is a simple implementation of Context for a slice of bytes.
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type DefaultContext []byte
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// AuthenticatedData returns itself.
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func (c DefaultContext) AuthenticatedData() []byte { return []byte(c) }
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// MutableTransformer allows a transformer to be changed safely at runtime.
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type MutableTransformer struct {
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lock sync.RWMutex
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transformer Transformer
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}
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// NewMutableTransformer creates a transformer that can be updated at any time by calling Set()
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func NewMutableTransformer(transformer Transformer) *MutableTransformer {
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return &MutableTransformer{transformer: transformer}
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}
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// Set updates the nested transformer.
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func (t *MutableTransformer) Set(transformer Transformer) {
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t.lock.Lock()
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t.transformer = transformer
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t.lock.Unlock()
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}
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func (t *MutableTransformer) TransformFromStorage(data []byte, context Context) (out []byte, stale bool, err error) {
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t.lock.RLock()
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transformer := t.transformer
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t.lock.RUnlock()
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return transformer.TransformFromStorage(data, context)
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}
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func (t *MutableTransformer) TransformToStorage(data []byte, context Context) (out []byte, err error) {
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t.lock.RLock()
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transformer := t.transformer
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t.lock.RUnlock()
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return transformer.TransformToStorage(data, context)
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}
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// PrefixTransformer holds a transformer interface and the prefix that the transformation is located under.
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type PrefixTransformer struct {
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Prefix []byte
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Transformer Transformer
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}
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type prefixTransformers struct {
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transformers []PrefixTransformer
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err error
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}
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var _ Transformer = &prefixTransformers{}
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// NewPrefixTransformers supports the Transformer interface by checking the incoming data against the provided
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// prefixes in order. The first matching prefix will be used to transform the value (the prefix is stripped
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// before the Transformer interface is invoked). The first provided transformer will be used when writing to
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// the store.
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func NewPrefixTransformers(err error, transformers ...PrefixTransformer) Transformer {
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if err == nil {
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err = fmt.Errorf("the provided value does not match any of the supported transformers")
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}
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return &prefixTransformers{
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transformers: transformers,
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err: err,
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}
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}
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// TransformFromStorage finds the first transformer with a prefix matching the provided data and returns
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// the result of transforming the value. It will always mark any transformation as stale that is not using
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// the first transformer.
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func (t *prefixTransformers) TransformFromStorage(data []byte, context Context) ([]byte, bool, error) {
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for i, transformer := range t.transformers {
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if bytes.HasPrefix(data, transformer.Prefix) {
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result, stale, err := transformer.Transformer.TransformFromStorage(data[len(transformer.Prefix):], context)
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return result, stale || i != 0, err
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}
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}
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return nil, false, t.err
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}
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// TransformToStorage uses the first transformer and adds its prefix to the data.
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func (t *prefixTransformers) TransformToStorage(data []byte, context Context) ([]byte, error) {
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transformer := t.transformers[0]
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prefixedData := make([]byte, len(transformer.Prefix), len(data)+len(transformer.Prefix))
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copy(prefixedData, transformer.Prefix)
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result, err := transformer.Transformer.TransformToStorage(data, context)
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if err != nil {
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return nil, err
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}
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prefixedData = append(prefixedData, result...)
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return prefixedData, nil
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}
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@ -0,0 +1,101 @@
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/*
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Copyright 2017 The Kubernetes Authors.
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|
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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.
|
||||
*/
|
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|
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package value
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|
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import (
|
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"bytes"
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"fmt"
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"testing"
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)
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type testTransformer struct {
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from, to []byte
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err error
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stale bool
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receivedFrom, receivedTo []byte
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}
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func (t *testTransformer) TransformFromStorage(from []byte, context Context) (data []byte, stale bool, err error) {
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t.receivedFrom = from
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return t.from, t.stale, t.err
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}
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func (t *testTransformer) TransformToStorage(to []byte, context Context) (data []byte, err error) {
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t.receivedTo = to
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return t.to, t.err
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}
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func TestPrefixFrom(t *testing.T) {
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testErr := fmt.Errorf("test error")
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transformErr := fmt.Errorf("test error")
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transformers := []PrefixTransformer{
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{Prefix: []byte("first:"), Transformer: &testTransformer{from: []byte("value1")}},
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{Prefix: []byte("second:"), Transformer: &testTransformer{from: []byte("value2")}},
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{Prefix: []byte("fails:"), Transformer: &testTransformer{err: transformErr}},
|
||||
{Prefix: []byte("stale:"), Transformer: &testTransformer{from: []byte("value3"), stale: true}},
|
||||
}
|
||||
p := NewPrefixTransformers(testErr, transformers...)
|
||||
|
||||
testCases := []struct {
|
||||
input []byte
|
||||
expect []byte
|
||||
stale bool
|
||||
err error
|
||||
match int
|
||||
}{
|
||||
{[]byte("first:value"), []byte("value1"), false, nil, 0},
|
||||
{[]byte("second:value"), []byte("value2"), true, nil, 1},
|
||||
{[]byte("third:value"), nil, false, testErr, -1},
|
||||
{[]byte("fails:value"), nil, true, transformErr, 2},
|
||||
{[]byte("stale:value"), []byte("value3"), true, nil, 3},
|
||||
}
|
||||
for i, test := range testCases {
|
||||
got, stale, err := p.TransformFromStorage(test.input, nil)
|
||||
if err != test.err || stale != test.stale || !bytes.Equal(got, test.expect) {
|
||||
t.Errorf("%d: unexpected out: %q %t %#v", i, string(got), stale, err)
|
||||
continue
|
||||
}
|
||||
if test.match != -1 && !bytes.Equal([]byte("value"), transformers[test.match].Transformer.(*testTransformer).receivedFrom) {
|
||||
t.Errorf("%d: unexpected value received by transformer: %s", i, transformers[test.match].Transformer.(*testTransformer).receivedFrom)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func TestPrefixTo(t *testing.T) {
|
||||
testErr := fmt.Errorf("test error")
|
||||
transformErr := fmt.Errorf("test error")
|
||||
testCases := []struct {
|
||||
transformers []PrefixTransformer
|
||||
expect []byte
|
||||
err error
|
||||
}{
|
||||
{[]PrefixTransformer{{Prefix: []byte("first:"), Transformer: &testTransformer{to: []byte("value1")}}}, []byte("first:value1"), nil},
|
||||
{[]PrefixTransformer{{Prefix: []byte("second:"), Transformer: &testTransformer{to: []byte("value2")}}}, []byte("second:value2"), nil},
|
||||
{[]PrefixTransformer{{Prefix: []byte("fails:"), Transformer: &testTransformer{err: transformErr}}}, nil, transformErr},
|
||||
}
|
||||
for i, test := range testCases {
|
||||
p := NewPrefixTransformers(testErr, test.transformers...)
|
||||
got, err := p.TransformToStorage([]byte("value"), nil)
|
||||
if err != test.err || !bytes.Equal(got, test.expect) {
|
||||
t.Errorf("%d: unexpected out: %q %#v", i, string(got), err)
|
||||
continue
|
||||
}
|
||||
if !bytes.Equal([]byte("value"), test.transformers[0].Transformer.(*testTransformer).receivedTo) {
|
||||
t.Errorf("%d: unexpected value received by transformer: %s", i, test.transformers[0].Transformer.(*testTransformer).receivedTo)
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue