This commit refactors the SSE implementation and add S3-compatible SSE-KMS context handling. SSE-KMS differs from SSE-S3 in two main aspects: 1. The client can request a particular key and specify a KMS context as part of the request. 2. The ETag of an SSE-KMS encrypted object is not the MD5 sum of the object content. This commit only focuses on the 1st aspect. A client can send an optional SSE context when using SSE-KMS. This context is remembered by the S3 server such that the client does not have to specify the context again (during multipart PUT / GET / HEAD ...). The crypto. context also includes the bucket/object name to prevent renaming objects at the backend. Now, AWS S3 behaves as following: - If the user does not provide a SSE-KMS context it does not store one - resp. does not include the SSE-KMS context header in the response (e.g. HEAD). - If the user specifies a SSE-KMS context without the bucket/object name then AWS stores the exact context the client provided but adds the bucket/object name internally. The response contains the KMS context without the bucket/object name. - If the user specifies a SSE-KMS context with the bucket/object name then AWS again stores the exact context provided by the client. The response contains the KMS context with the bucket/object name. This commit implements this behavior w.r.t. SSE-KMS. However, as of now, no such object can be created since the server rejects SSE-KMS encryption requests. This commit is one stepping stone for SSE-KMS support. Co-authored-by: Harshavardhana <harsha@minio.io>
175 lines
6.4 KiB
Go
175 lines
6.4 KiB
Go
/*
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* Minio Cloud Storage, (C) 2019-2020 Minio, Inc.
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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 crypto
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import (
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"context"
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"encoding/base64"
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"errors"
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"net/http"
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"path"
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"strings"
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xhttp "github.com/minio/minio/cmd/http"
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"github.com/minio/minio/cmd/logger"
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)
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type sses3 struct{}
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var (
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// S3 represents AWS SSE-S3. It provides functionality to handle
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// SSE-S3 requests.
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S3 = sses3{}
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_ Type = S3
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)
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// String returns the SSE domain as string. For SSE-S3 the
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// domain is "SSE-S3".
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func (sses3) String() string { return "SSE-S3" }
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func (sses3) IsRequested(h http.Header) bool {
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_, ok := h[xhttp.AmzServerSideEncryption]
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return ok && strings.ToLower(h.Get(xhttp.AmzServerSideEncryption)) != xhttp.AmzEncryptionKMS // Return only true if the SSE header is specified and does not contain the SSE-KMS value
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}
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// ParseHTTP parses the SSE-S3 related HTTP headers and checks
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// whether they contain valid values.
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func (sses3) ParseHTTP(h http.Header) error {
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if h.Get(xhttp.AmzServerSideEncryption) != xhttp.AmzEncryptionAES {
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return ErrInvalidEncryptionMethod
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}
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return nil
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}
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// IsEncrypted returns true if the object metadata indicates
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// that the object was uploaded using SSE-S3.
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func (sses3) IsEncrypted(metadata map[string]string) bool {
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if _, ok := metadata[MetaSealedKeyS3]; ok {
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return true
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}
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return false
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}
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// UnsealObjectKey extracts and decrypts the sealed object key
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// from the metadata using KMS and returns the decrypted object
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// key.
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func (s3 sses3) UnsealObjectKey(kms KMS, metadata map[string]string, bucket, object string) (key ObjectKey, err error) {
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keyID, kmsKey, sealedKey, err := s3.ParseMetadata(metadata)
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if err != nil {
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return key, err
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}
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unsealKey, err := kms.UnsealKey(keyID, kmsKey, Context{bucket: path.Join(bucket, object)})
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if err != nil {
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return key, err
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}
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err = key.Unseal(unsealKey, sealedKey, s3.String(), bucket, object)
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return key, err
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}
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// CreateMetadata encodes the sealed object key into the metadata and returns
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// the modified metadata. If the keyID and the kmsKey is not empty it encodes
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// both into the metadata as well. It allocates a new metadata map if metadata
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// is nil.
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func (sses3) CreateMetadata(metadata map[string]string, keyID string, kmsKey []byte, sealedKey SealedKey) map[string]string {
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if sealedKey.Algorithm != SealAlgorithm {
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logger.CriticalIf(context.Background(), Errorf("The seal algorithm '%s' is invalid for SSE-S3", sealedKey.Algorithm))
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}
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// There are two possibilites:
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// - We use a KMS -> There must be non-empty key ID and a KMS data key.
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// - We use a K/V -> There must be no key ID and no KMS data key.
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// Otherwise, the caller has passed an invalid argument combination.
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if keyID == "" && len(kmsKey) != 0 {
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logger.CriticalIf(context.Background(), errors.New("The key ID must not be empty if a KMS data key is present"))
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}
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if keyID != "" && len(kmsKey) == 0 {
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logger.CriticalIf(context.Background(), errors.New("The KMS data key must not be empty if a key ID is present"))
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}
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if metadata == nil {
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metadata = make(map[string]string, 5)
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}
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metadata[MetaAlgorithm] = sealedKey.Algorithm
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metadata[MetaIV] = base64.StdEncoding.EncodeToString(sealedKey.IV[:])
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metadata[MetaSealedKeyS3] = base64.StdEncoding.EncodeToString(sealedKey.Key[:])
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if len(kmsKey) > 0 && keyID != "" { // We use a KMS -> Store key ID and sealed KMS data key.
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metadata[MetaKeyID] = keyID
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metadata[MetaDataEncryptionKey] = base64.StdEncoding.EncodeToString(kmsKey)
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}
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return metadata
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}
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// ParseMetadata extracts all SSE-S3 related values from the object metadata
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// and checks whether they are well-formed. It returns the sealed object key
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// on success. If the metadata contains both, a KMS master key ID and a sealed
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// KMS data key it returns both. If the metadata does not contain neither a
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// KMS master key ID nor a sealed KMS data key it returns an empty keyID and
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// KMS data key. Otherwise, it returns an error.
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func (sses3) ParseMetadata(metadata map[string]string) (keyID string, kmsKey []byte, sealedKey SealedKey, err error) {
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// Extract all required values from object metadata
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b64IV, ok := metadata[MetaIV]
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if !ok {
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return keyID, kmsKey, sealedKey, errMissingInternalIV
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}
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algorithm, ok := metadata[MetaAlgorithm]
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if !ok {
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return keyID, kmsKey, sealedKey, errMissingInternalSealAlgorithm
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}
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b64SealedKey, ok := metadata[MetaSealedKeyS3]
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if !ok {
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return keyID, kmsKey, sealedKey, Errorf("The object metadata is missing the internal sealed key for SSE-S3")
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}
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// There are two possibilites:
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// - We use a KMS -> There must be a key ID and a KMS data key.
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// - We use a K/V -> There must be no key ID and no KMS data key.
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// Otherwise, the metadata is corrupted.
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keyID, idPresent := metadata[MetaKeyID]
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b64KMSSealedKey, kmsKeyPresent := metadata[MetaDataEncryptionKey]
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if !idPresent && kmsKeyPresent {
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return keyID, kmsKey, sealedKey, Errorf("The object metadata is missing the internal KMS key-ID for SSE-S3")
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}
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if idPresent && !kmsKeyPresent {
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return keyID, kmsKey, sealedKey, Errorf("The object metadata is missing the internal sealed KMS data key for SSE-S3")
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}
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// Check whether all extracted values are well-formed
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iv, err := base64.StdEncoding.DecodeString(b64IV)
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if err != nil || len(iv) != 32 {
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return keyID, kmsKey, sealedKey, errInvalidInternalIV
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}
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if algorithm != SealAlgorithm {
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return keyID, kmsKey, sealedKey, errInvalidInternalSealAlgorithm
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}
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encryptedKey, err := base64.StdEncoding.DecodeString(b64SealedKey)
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if err != nil || len(encryptedKey) != 64 {
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return keyID, kmsKey, sealedKey, Errorf("The internal sealed key for SSE-S3 is invalid")
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}
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if idPresent && kmsKeyPresent { // We are using a KMS -> parse the sealed KMS data key.
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kmsKey, err = base64.StdEncoding.DecodeString(b64KMSSealedKey)
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if err != nil {
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return keyID, kmsKey, sealedKey, Errorf("The internal sealed KMS data key for SSE-S3 is invalid")
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}
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}
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sealedKey.Algorithm = algorithm
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copy(sealedKey.IV[:], iv)
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copy(sealedKey.Key[:], encryptedKey)
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return keyID, kmsKey, sealedKey, nil
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}
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