mirror of
https://github.com/k3s-io/k3s.git
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329 lines
10 KiB
Go
329 lines
10 KiB
Go
/*
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Copyright The ocicrypt 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 ocicrypt
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import (
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"encoding/base64"
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"encoding/json"
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"io"
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"strings"
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"github.com/containers/ocicrypt/blockcipher"
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"github.com/containers/ocicrypt/config"
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"github.com/containers/ocicrypt/keywrap"
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"github.com/containers/ocicrypt/keywrap/jwe"
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"github.com/containers/ocicrypt/keywrap/pgp"
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"github.com/containers/ocicrypt/keywrap/pkcs7"
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"github.com/opencontainers/go-digest"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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"github.com/pkg/errors"
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)
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// EncryptLayerFinalizer is a finalizer run to return the annotations to set for
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// the encrypted layer
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type EncryptLayerFinalizer func() (map[string]string, error)
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func init() {
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keyWrappers = make(map[string]keywrap.KeyWrapper)
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keyWrapperAnnotations = make(map[string]string)
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RegisterKeyWrapper("pgp", pgp.NewKeyWrapper())
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RegisterKeyWrapper("jwe", jwe.NewKeyWrapper())
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RegisterKeyWrapper("pkcs7", pkcs7.NewKeyWrapper())
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}
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var keyWrappers map[string]keywrap.KeyWrapper
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var keyWrapperAnnotations map[string]string
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// RegisterKeyWrapper allows to register key wrappers by their encryption scheme
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func RegisterKeyWrapper(scheme string, iface keywrap.KeyWrapper) {
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keyWrappers[scheme] = iface
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keyWrapperAnnotations[iface.GetAnnotationID()] = scheme
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}
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// GetKeyWrapper looks up the encryptor interface given an encryption scheme (gpg, jwe)
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func GetKeyWrapper(scheme string) keywrap.KeyWrapper {
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return keyWrappers[scheme]
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}
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// GetWrappedKeysMap returns a map of wrappedKeys as values in a
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// map with the encryption scheme(s) as the key(s)
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func GetWrappedKeysMap(desc ocispec.Descriptor) map[string]string {
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wrappedKeysMap := make(map[string]string)
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for annotationsID, scheme := range keyWrapperAnnotations {
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if annotation, ok := desc.Annotations[annotationsID]; ok {
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wrappedKeysMap[scheme] = annotation
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}
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}
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return wrappedKeysMap
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}
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// EncryptLayer encrypts the layer by running one encryptor after the other
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func EncryptLayer(ec *config.EncryptConfig, encOrPlainLayerReader io.Reader, desc ocispec.Descriptor) (io.Reader, EncryptLayerFinalizer, error) {
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var (
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encLayerReader io.Reader
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err error
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encrypted bool
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bcFin blockcipher.Finalizer
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privOptsData []byte
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pubOptsData []byte
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)
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if ec == nil {
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return nil, nil, errors.New("EncryptConfig must not be nil")
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}
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for annotationsID := range keyWrapperAnnotations {
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annotation := desc.Annotations[annotationsID]
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if annotation != "" {
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privOptsData, err = decryptLayerKeyOptsData(&ec.DecryptConfig, desc)
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if err != nil {
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return nil, nil, err
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}
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pubOptsData, err = getLayerPubOpts(desc)
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if err != nil {
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return nil, nil, err
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}
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// already encrypted!
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encrypted = true
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}
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}
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if !encrypted {
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encLayerReader, bcFin, err = commonEncryptLayer(encOrPlainLayerReader, desc.Digest, blockcipher.AES256CTR)
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if err != nil {
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return nil, nil, err
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}
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}
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encLayerFinalizer := func() (map[string]string, error) {
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// If layer was already encrypted, bcFin should be nil, use existing optsData
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if bcFin != nil {
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opts, err := bcFin()
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if err != nil {
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return nil, err
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}
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privOptsData, err = json.Marshal(opts.Private)
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if err != nil {
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return nil, errors.Wrapf(err, "could not JSON marshal opts")
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}
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pubOptsData, err = json.Marshal(opts.Public)
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if err != nil {
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return nil, errors.Wrapf(err, "could not JSON marshal opts")
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}
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}
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newAnnotations := make(map[string]string)
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for annotationsID, scheme := range keyWrapperAnnotations {
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b64Annotations := desc.Annotations[annotationsID]
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keywrapper := GetKeyWrapper(scheme)
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b64Annotations, err = preWrapKeys(keywrapper, ec, b64Annotations, privOptsData)
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if err != nil {
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return nil, err
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}
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if b64Annotations != "" {
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newAnnotations[annotationsID] = b64Annotations
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}
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}
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newAnnotations["org.opencontainers.image.enc.pubopts"] = base64.StdEncoding.EncodeToString(pubOptsData)
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if len(newAnnotations) == 0 {
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return nil, errors.New("no encryptor found to handle encryption")
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}
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return newAnnotations, err
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}
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// if nothing was encrypted, we just return encLayer = nil
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return encLayerReader, encLayerFinalizer, err
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}
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// preWrapKeys calls WrapKeys and handles the base64 encoding and concatenation of the
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// annotation data
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func preWrapKeys(keywrapper keywrap.KeyWrapper, ec *config.EncryptConfig, b64Annotations string, optsData []byte) (string, error) {
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newAnnotation, err := keywrapper.WrapKeys(ec, optsData)
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if err != nil || len(newAnnotation) == 0 {
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return b64Annotations, err
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}
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b64newAnnotation := base64.StdEncoding.EncodeToString(newAnnotation)
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if b64Annotations == "" {
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return b64newAnnotation, nil
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}
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return b64Annotations + "," + b64newAnnotation, nil
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}
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// DecryptLayer decrypts a layer trying one keywrap.KeyWrapper after the other to see whether it
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// can apply the provided private key
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// If unwrapOnly is set we will only try to decrypt the layer encryption key and return
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func DecryptLayer(dc *config.DecryptConfig, encLayerReader io.Reader, desc ocispec.Descriptor, unwrapOnly bool) (io.Reader, digest.Digest, error) {
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if dc == nil {
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return nil, "", errors.New("DecryptConfig must not be nil")
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}
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privOptsData, err := decryptLayerKeyOptsData(dc, desc)
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if err != nil || unwrapOnly {
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return nil, "", err
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}
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var pubOptsData []byte
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pubOptsData, err = getLayerPubOpts(desc)
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if err != nil {
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return nil, "", err
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}
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return commonDecryptLayer(encLayerReader, privOptsData, pubOptsData)
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}
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func decryptLayerKeyOptsData(dc *config.DecryptConfig, desc ocispec.Descriptor) ([]byte, error) {
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privKeyGiven := false
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for annotationsID, scheme := range keyWrapperAnnotations {
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b64Annotation := desc.Annotations[annotationsID]
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if b64Annotation != "" {
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keywrapper := GetKeyWrapper(scheme)
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if keywrapper.NoPossibleKeys(dc.Parameters) {
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continue
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}
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if len(keywrapper.GetPrivateKeys(dc.Parameters)) > 0 {
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privKeyGiven = true
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}
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optsData, err := preUnwrapKey(keywrapper, dc, b64Annotation)
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if err != nil {
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// try next keywrap.KeyWrapper
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continue
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}
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if optsData == nil {
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// try next keywrap.KeyWrapper
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continue
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}
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return optsData, nil
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}
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}
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if !privKeyGiven {
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return nil, errors.New("missing private key needed for decryption")
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}
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return nil, errors.Errorf("no suitable key unwrapper found or none of the private keys could be used for decryption")
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}
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func getLayerPubOpts(desc ocispec.Descriptor) ([]byte, error) {
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pubOptsString := desc.Annotations["org.opencontainers.image.enc.pubopts"]
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if pubOptsString == "" {
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return json.Marshal(blockcipher.PublicLayerBlockCipherOptions{})
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}
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return base64.StdEncoding.DecodeString(pubOptsString)
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}
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// preUnwrapKey decodes the comma separated base64 strings and calls the Unwrap function
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// of the given keywrapper with it and returns the result in case the Unwrap functions
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// does not return an error. If all attempts fail, an error is returned.
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func preUnwrapKey(keywrapper keywrap.KeyWrapper, dc *config.DecryptConfig, b64Annotations string) ([]byte, error) {
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if b64Annotations == "" {
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return nil, nil
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}
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for _, b64Annotation := range strings.Split(b64Annotations, ",") {
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annotation, err := base64.StdEncoding.DecodeString(b64Annotation)
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if err != nil {
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return nil, errors.New("could not base64 decode the annotation")
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}
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optsData, err := keywrapper.UnwrapKey(dc, annotation)
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if err != nil {
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continue
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}
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return optsData, nil
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}
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return nil, errors.New("no suitable key found for decrypting layer key")
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}
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// commonEncryptLayer is a function to encrypt the plain layer using a new random
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// symmetric key and return the LayerBlockCipherHandler's JSON in string form for
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// later use during decryption
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func commonEncryptLayer(plainLayerReader io.Reader, d digest.Digest, typ blockcipher.LayerCipherType) (io.Reader, blockcipher.Finalizer, error) {
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lbch, err := blockcipher.NewLayerBlockCipherHandler()
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if err != nil {
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return nil, nil, err
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}
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encLayerReader, bcFin, err := lbch.Encrypt(plainLayerReader, typ)
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if err != nil {
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return nil, nil, err
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}
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newBcFin := func() (blockcipher.LayerBlockCipherOptions, error) {
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lbco, err := bcFin()
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if err != nil {
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return blockcipher.LayerBlockCipherOptions{}, err
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}
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lbco.Private.Digest = d
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return lbco, nil
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}
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return encLayerReader, newBcFin, err
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}
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// commonDecryptLayer decrypts an encrypted layer previously encrypted with commonEncryptLayer
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// by passing along the optsData
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func commonDecryptLayer(encLayerReader io.Reader, privOptsData []byte, pubOptsData []byte) (io.Reader, digest.Digest, error) {
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privOpts := blockcipher.PrivateLayerBlockCipherOptions{}
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err := json.Unmarshal(privOptsData, &privOpts)
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if err != nil {
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return nil, "", errors.Wrapf(err, "could not JSON unmarshal privOptsData")
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}
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lbch, err := blockcipher.NewLayerBlockCipherHandler()
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if err != nil {
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return nil, "", err
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}
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pubOpts := blockcipher.PublicLayerBlockCipherOptions{}
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if len(pubOptsData) > 0 {
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err := json.Unmarshal(pubOptsData, &pubOpts)
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if err != nil {
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return nil, "", errors.Wrapf(err, "could not JSON unmarshal pubOptsData")
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}
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}
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opts := blockcipher.LayerBlockCipherOptions{
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Private: privOpts,
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Public: pubOpts,
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}
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plainLayerReader, opts, err := lbch.Decrypt(encLayerReader, opts)
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if err != nil {
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return nil, "", err
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}
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return plainLayerReader, opts.Private.Digest, nil
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}
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// FilterOutAnnotations filters out the annotations belonging to the image encryption 'namespace'
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// and returns a map with those taken out
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func FilterOutAnnotations(annotations map[string]string) map[string]string {
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a := make(map[string]string)
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if len(annotations) > 0 {
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for k, v := range annotations {
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if strings.HasPrefix(k, "org.opencontainers.image.enc.") {
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continue
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}
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a[k] = v
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}
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}
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return a
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}
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