This commit adds two functions for sealing/unsealing the etag (a.k.a. content MD5) in case of SSE single-part upload. Sealing the ETag is neccessary in case of SSE-S3 to preserve the security guarantees. In case of SSE-S3 AWS returns the content-MD5 of the plaintext object as ETag. However, we must not store the MD5 of the plaintext for encrypted objects. Otherwise it becomes possible for an attacker to detect equal/non-equal encrypted objects. Therefore we encrypt the ETag before storing on the backend. But we only need to encrypt the ETag (content-MD5) if the client send it - otherwise the client cannot verify it anyway.
225 lines
7.6 KiB
Go
225 lines
7.6 KiB
Go
// Minio Cloud Storage, (C) 2015, 2016, 2017, 2018 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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package crypto
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import (
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"context"
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"encoding/base64"
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"fmt"
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"github.com/minio/minio/cmd/logger"
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)
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// IsMultiPart returns true if the object metadata indicates
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// that it was uploaded using some form of server-side-encryption
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// and the S3 multipart API.
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func IsMultiPart(metadata map[string]string) bool {
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if _, ok := metadata[SSEMultipart]; 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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// RemoveSensitiveEntries removes confidential encryption
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// information - e.g. the SSE-C key - from the metadata map.
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// It has the same semantics as RemoveSensitiveHeaders.
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func RemoveSensitiveEntries(metadata map[string]string) { // The functions is tested in TestRemoveSensitiveHeaders for compatibility reasons
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delete(metadata, SSECKey)
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delete(metadata, SSECopyKey)
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}
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// IsEncrypted returns true if the object metadata indicates
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// that it was uploaded using some form of server-side-encryption.
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//
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// IsEncrypted only checks whether the metadata contains at least
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// one entry indicating SSE-C or SSE-S3.
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func IsEncrypted(metadata map[string]string) bool {
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if _, ok := metadata[SSEIV]; ok {
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return true
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}
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if _, ok := metadata[SSESealAlgorithm]; ok {
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return true
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}
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if IsMultiPart(metadata) {
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return true
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}
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if S3.IsEncrypted(metadata) {
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return true
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}
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if SSEC.IsEncrypted(metadata) {
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return true
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}
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return false
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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 (s3) IsEncrypted(metadata map[string]string) bool {
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if _, ok := metadata[S3SealedKey]; ok {
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return true
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}
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if _, ok := metadata[S3KMSKeyID]; ok {
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return true
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}
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if _, ok := metadata[S3KMSSealedKey]; 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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// IsEncrypted returns true if the object metadata indicates
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// that the object was uploaded using SSE-C.
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func (ssec) IsEncrypted(metadata map[string]string) bool {
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if _, ok := metadata[SSECSealedKey]; 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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// CreateMultipartMetadata adds the multipart flag entry to metadata
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// and returns modifed metadata. It allocates a new metadata map if
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// metadata is nil.
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func CreateMultipartMetadata(metadata map[string]string) map[string]string {
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if metadata == nil {
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metadata = map[string]string{}
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}
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metadata[SSEMultipart] = ""
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return metadata
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}
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// CreateMetadata encodes the keyID, the sealed kms data key and the sealed key
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// into the metadata and returns the modified metadata. It allocates a new
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// metadata map if metadata is nil.
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func (s3) 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(), fmt.Errorf("The seal algorithm '%s' is invalid for SSE-S3", sealedKey.Algorithm))
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}
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if metadata == nil {
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metadata = map[string]string{}
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}
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metadata[S3KMSKeyID] = keyID
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metadata[SSESealAlgorithm] = sealedKey.Algorithm
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metadata[SSEIV] = base64.StdEncoding.EncodeToString(sealedKey.IV[:])
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metadata[S3SealedKey] = base64.StdEncoding.EncodeToString(sealedKey.Key[:])
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metadata[S3KMSSealedKey] = base64.StdEncoding.EncodeToString(kmsKey)
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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 KMS key-ID, the
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// sealed KMS key and the sealed object key on success.
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func (s3) 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[SSEIV]
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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[SSESealAlgorithm]
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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[S3SealedKey]
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if !ok {
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return keyID, kmsKey, sealedKey, Error{"The object metadata is missing the internal sealed key for SSE-S3"}
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}
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keyID, ok = metadata[S3KMSKeyID]
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if !ok {
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return keyID, kmsKey, sealedKey, Error{"The object metadata is missing the internal KMS key-ID for SSE-S3"}
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}
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b64KMSSealedKey, ok := metadata[S3KMSSealedKey]
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if !ok {
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return keyID, kmsKey, sealedKey, Error{"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, Error{"The internal sealed key for SSE-S3 is invalid"}
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}
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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, Error{"The internal sealed KMS data key for SSE-S3 is invalid"}
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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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// CreateMetadata encodes the sealed key into the metadata and returns the modified metadata.
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// It allocates a new metadata map if metadata is nil.
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func (ssec) CreateMetadata(metadata map[string]string, sealedKey SealedKey) map[string]string {
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if sealedKey.Algorithm != SealAlgorithm {
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logger.CriticalIf(context.Background(), fmt.Errorf("The seal algorithm '%s' is invalid for SSE-C", sealedKey.Algorithm))
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}
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if metadata == nil {
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metadata = map[string]string{}
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}
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metadata[SSESealAlgorithm] = SealAlgorithm
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metadata[SSEIV] = base64.StdEncoding.EncodeToString(sealedKey.IV[:])
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metadata[SSECSealedKey] = base64.StdEncoding.EncodeToString(sealedKey.Key[:])
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return metadata
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}
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// ParseMetadata extracts all SSE-C 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.
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func (ssec) ParseMetadata(metadata map[string]string) (sealedKey SealedKey, err error) {
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// Extract all required values from object metadata
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b64IV, ok := metadata[SSEIV]
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if !ok {
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return sealedKey, errMissingInternalIV
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}
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algorithm, ok := metadata[SSESealAlgorithm]
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if !ok {
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return sealedKey, errMissingInternalSealAlgorithm
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}
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b64SealedKey, ok := metadata[SSECSealedKey]
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if !ok {
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return sealedKey, Error{"The object metadata is missing the internal sealed key for SSE-C"}
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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 sealedKey, errInvalidInternalIV
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}
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if algorithm != SealAlgorithm && algorithm != InsecureSealAlgorithm {
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return 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 sealedKey, Error{"The internal sealed key for SSE-C is invalid"}
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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 sealedKey, nil
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}
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// IsETagSealed returns true if the etag seems to be encrypted.
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func IsETagSealed(etag []byte) bool { return len(etag) > 16 }
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