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fix object rebinding SSE-C security guarantee violation (#6121)

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This commit fixes a weakness of the key-encryption-key
derivation for SSE-C encrypted objects. Before this
change the key-encryption-key was not bound to / didn't
depend on the object path. This allows an attacker to
repalce objects - encrypted with the same
client-key - with each other.

This change fixes this issue by updating the
key-encryption-key derivation to include:
 - the domain (in this case SSE-C)
 - a canonical object path representation
 - the encryption & key derivation algorithm

Changing the object path now causes the KDF to derive a
different key-encryption-key such that the object-key
unsealing fails.
Including the domain (SSE-C) and encryption & key
derivation algorithm is not directly neccessary for this
fix. However, both will be included for the SSE-S3 KDF.
So they are included here to avoid updating the KDF
again when we add SSE-S3.

The leagcy KDF 'DARE-SHA256' is only used for existing
objects and never for new objects / key rotation.
This commit is contained in:
Andreas Auernhammer
2018-07-10 02:18:28 +02:00
committed by kannappanr
parent 4ddc222f46
commit b181a693fb
5 changed files with 178 additions and 96 deletions
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22
cmd/object-handlers.go
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@@ -161,7 +161,7 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
// additionally also skipping mod(offset)64KiB boundaries.
writer = ioutil.LimitedWriter(writer, startOffset%(64*1024), length)
writer, startOffset, length, err = DecryptBlocksRequest(writer, r, startOffset, length, objInfo, false)
writer, startOffset, length, err = DecryptBlocksRequest(writer, r, bucket, object, startOffset, length, objInfo, false)
if err != nil {
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
@@ -270,7 +270,7 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
writeErrorResponse(w, apiErr, r.URL)
return
} else if encrypted {
if _, err = DecryptRequest(w, r, objInfo.UserDefined); err != nil {
if _, err = DecryptRequest(w, r, bucket, object, objInfo.UserDefined); err != nil {
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
}
@@ -463,7 +463,7 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
for k, v := range srcInfo.UserDefined {
encMetadata[k] = v
}
if err = rotateKey(oldKey, newKey, encMetadata); err != nil {
if err = rotateKey(oldKey, newKey, srcBucket, srcObject, encMetadata); err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
@@ -475,7 +475,7 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
if sseCopyC {
// Source is encrypted make sure to save the encrypted size.
writer = ioutil.LimitedWriter(writer, 0, srcInfo.Size)
writer, srcInfo.Size, err = DecryptAllBlocksCopyRequest(writer, r, srcInfo)
writer, srcInfo.Size, err = DecryptAllBlocksCopyRequest(writer, r, srcBucket, srcObject, srcInfo)
if err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
@@ -490,7 +490,7 @@ func (api objectAPIHandlers) CopyObjectHandler(w http.ResponseWriter, r *http.Re
}
}
if sseC {
reader, err = newEncryptReader(pipeReader, newKey, encMetadata)
reader, err = newEncryptReader(reader, newKey, dstBucket, dstObject, encMetadata)
if err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
@@ -789,7 +789,7 @@ func (api objectAPIHandlers) PutObjectHandler(w http.ResponseWriter, r *http.Req
if objectAPI.IsEncryptionSupported() {
if hasSSECustomerHeader(r.Header) && !hasSuffix(object, slashSeparator) { // handle SSE-C requests
reader, err = EncryptRequest(hashReader, r, metadata)
reader, err = EncryptRequest(hashReader, r, bucket, object, metadata)
if err != nil {
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
@@ -888,7 +888,7 @@ func (api objectAPIHandlers) NewMultipartUploadHandler(w http.ResponseWriter, r
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
}
_, err = newEncryptMetadata(key, encMetadata)
_, err = newEncryptMetadata(key, bucket, object, encMetadata)
if err != nil {
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
@@ -1056,7 +1056,7 @@ func (api objectAPIHandlers) CopyObjectPartHandler(w http.ResponseWriter, r *htt
// Response writer should be limited early on for decryption upto required length,
// additionally also skipping mod(offset)64KiB boundaries.
writer = ioutil.LimitedWriter(writer, startOffset%(64*1024), length)
writer, startOffset, length, err = DecryptBlocksRequest(pipeWriter, r, startOffset, length, srcInfo, true)
writer, startOffset, length, err = DecryptBlocksRequest(writer, r, srcBucket, srcObject, startOffset, length, srcInfo, true)
if err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
@@ -1078,14 +1078,14 @@ func (api objectAPIHandlers) CopyObjectPartHandler(w http.ResponseWriter, r *htt
// Calculating object encryption key
var objectEncryptionKey []byte
objectEncryptionKey, err = decryptObjectInfo(key, li.UserDefined)
objectEncryptionKey, err = decryptObjectInfo(key, dstBucket, dstObject, li.UserDefined)
if err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return
}
reader, err = sio.EncryptReader(pipeReader, sio.Config{Key: objectEncryptionKey})
reader, err = sio.EncryptReader(reader, sio.Config{Key: objectEncryptionKey})
if err != nil {
pipeWriter.CloseWithError(err)
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
@@ -1281,7 +1281,7 @@ func (api objectAPIHandlers) PutObjectPartHandler(w http.ResponseWriter, r *http
// Calculating object encryption key
var objectEncryptionKey []byte
objectEncryptionKey, err = decryptObjectInfo(key, li.UserDefined)
objectEncryptionKey, err = decryptObjectInfo(key, bucket, object, li.UserDefined)
if err != nil {
writeErrorResponse(w, toAPIErrorCode(err), r.URL)
return