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package proton_api_bridge
import (
"bytes"
"context"
"io"
"log"
"github.com/ProtonMail/gopenpgp/v2/crypto"
"github.com/henrybear327/go-proton-api"
)
type FileDownloadReader struct {
protonDrive *ProtonDrive
ctx context.Context
link *proton.Link
data *bytes.Buffer
nodeKR *crypto.KeyRing
sessionKey *crypto.SessionKey
revision *proton.Revision
nextRevision int
isEOF bool
// TODO: integrity check if the entire file is read
}
func (r *FileDownloadReader) Read(p []byte) (int, error) {
if r.data.Len() == 0 {
// TODO: do we have memory sharing bug?
// to avoid sharing the underlying buffer array across re-population
r.data = bytes.NewBuffer(nil)
// we download and decrypt more content
err := r.populateBufferOnRead()
if err != nil {
return 0, err
}
if r.isEOF {
// if the file has been downloaded entirely, we return EOF
return 0, io.EOF
}
}
return r.data.Read(p)
}
func (r *FileDownloadReader) Close() error {
r.protonDrive = nil
return nil
}
func (reader *FileDownloadReader) populateBufferOnRead() error {
if len(reader.revision.Blocks) == 0 || len(reader.revision.Blocks) == reader.nextRevision {
reader.isEOF = true
return nil
}
offset := reader.nextRevision
for i := offset; i-offset < DOWNLOAD_BATCH_BLOCK_SIZE && i < len(reader.revision.Blocks); i++ {
// TODO: parallel download
blockReader, err := reader.protonDrive.c.GetBlock(reader.ctx, reader.revision.Blocks[i].BareURL, reader.revision.Blocks[i].Token)
if err != nil {
return err
}
defer blockReader.Close()
signatureVerificationKR, err := reader.protonDrive.getSignatureVerificationKeyring([]string{reader.link.SignatureEmail}, reader.nodeKR)
if err != nil {
return err
}
err = decryptBlockIntoBuffer(reader.sessionKey, signatureVerificationKR, reader.nodeKR, reader.revision.Blocks[i].Hash, reader.revision.Blocks[i].EncSignature, reader.data, blockReader)
if err != nil {
return err
}
reader.nextRevision = i + 1
}
return nil
}
func (protonDrive *ProtonDrive) DownloadFileByID(ctx context.Context, linkID string, offset int64) (io.ReadCloser, int64, *FileSystemAttrs, error) {
/* It's like event system, we need to get the latest information before creating the move request! */
protonDrive.removeLinkIDFromCache(linkID, false)
link, err := protonDrive.getLink(ctx, linkID)
if err != nil {
return nil, 0, nil, err
}
return protonDrive.DownloadFile(ctx, link, offset)
}
func (protonDrive *ProtonDrive) DownloadFile(ctx context.Context, link *proton.Link, offset int64) (io.ReadCloser, int64, *FileSystemAttrs, error) {
if link.Type != proton.LinkTypeFile {
return nil, 0, nil, ErrLinkTypeMustToBeFileType
}
parentNodeKR, err := protonDrive.getLinkKRByID(ctx, link.ParentLinkID)
if err != nil {
return nil, 0, nil, err
}
signatureVerificationKR, err := protonDrive.getSignatureVerificationKeyring([]string{link.SignatureEmail})
if err != nil {
return nil, 0, nil, err
}
nodeKR, err := link.GetKeyRing(parentNodeKR, signatureVerificationKR)
if err != nil {
return nil, 0, nil, err
}
sessionKey, err := link.GetSessionKey(nodeKR)
if err != nil {
return nil, 0, nil, err
}
revision, fileSystemAttrs, err := protonDrive.GetActiveRevisionWithAttrs(ctx, link)
if err != nil {
return nil, 0, nil, err
}
reader := &FileDownloadReader{
protonDrive: protonDrive,
ctx: ctx,
link: link,
data: bytes.NewBuffer(nil),
nodeKR: nodeKR,
sessionKey: sessionKey,
revision: revision,
nextRevision: 0,
isEOF: false,
}
useFallbackDownload := false
if fileSystemAttrs != nil {
// based on offset, infer the nextRevision (0-based)
if fileSystemAttrs.BlockSizes == nil {
useFallbackDownload = true
} else {
// infer nextRevision
totalBytes := int64(0)
for i := 0; i < len(fileSystemAttrs.BlockSizes); i++ {
prevTotalBytes := totalBytes
totalBytes += fileSystemAttrs.BlockSizes[i]
if offset <= totalBytes {
offset = offset - prevTotalBytes
reader.nextRevision = i
break
}
}
// download will start from the specified block
n, err := io.CopyN(io.Discard, reader, offset)
if err != nil {
return nil, 0, nil, err
}
if int64(n) != offset {
return nil, 0, nil, ErrSeekOffsetAfterSkippingBlocks
}
}
}
if useFallbackDownload {
log.Println("Performing inefficient seek as metadata of encrypted file is missing")
n, err := io.CopyN(io.Discard, reader, offset)
if err != nil {
return nil, 0, nil, err
}
if int64(n) != offset {
return nil, 0, nil, ErrSeekOffsetAfterSkippingBlocks
}
}
return reader, link.Size, fileSystemAttrs, nil
}
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