Adam Van Ymeren
7a04f298d2
- update to latest telegram layer - remove some references to fields in tg.Entities that don't exist in the schema - originally added here: https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e - referenced here - https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3 - https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e
99 lines
2.6 KiB
Go
99 lines
2.6 KiB
Go
package downloader
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import (
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"context"
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"crypto/aes"
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"crypto/cipher"
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"encoding/binary"
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"github.com/go-faster/errors"
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"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
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"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
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)
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// ExpiredTokenError error is returned when Downloader get expired file token for CDN.
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// See https://core.telegram.org/constructor/upload.fileCdnRedirect.
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type ExpiredTokenError struct {
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*tg.UploadCDNFileReuploadNeeded
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}
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// Error implements error interface.
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func (r *ExpiredTokenError) Error() string {
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return "redirect to master DC for requesting new file token"
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}
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// cdn is a CDN DC download schema.
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// See https://core.telegram.org/cdn#getting-files-from-a-cdn.
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type cdn struct {
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cdn CDN
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client Client
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pool *bin.Pool
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redirect *tg.UploadFileCDNRedirect
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}
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var _ schema = cdn{}
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// decrypt decrypts file chunk from Telegram CDN.
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// See https://core.telegram.org/cdn#decrypting-files.
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func (c cdn) decrypt(src []byte, offset int64) ([]byte, error) {
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block, err := aes.NewCipher(c.redirect.EncryptionKey)
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if err != nil {
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return nil, errors.Wrap(err, "create cipher")
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}
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if block.BlockSize() != len(c.redirect.EncryptionIv) {
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return nil, errors.Errorf(
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"invalid IV or key length, block size %d != IV %d",
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block.BlockSize(), len(c.redirect.EncryptionIv),
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)
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}
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// Copy IV to buffer from Pool.
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iv := c.pool.GetSize(len(c.redirect.EncryptionIv))
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defer c.pool.Put(iv)
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copy(iv.Buf, c.redirect.EncryptionIv)
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// For IV, it should use the value of encryption_iv, modified in the following manner:
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// for each offset replace the last 4 bytes of the encryption_iv with offset / 16 in big-endian.
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binary.BigEndian.PutUint32(iv.Buf[iv.Len()-4:], uint32(offset/16))
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dst := make([]byte, len(src))
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cipher.NewCTR(block, iv.Buf).XORKeyStream(dst, src)
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return dst, nil
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}
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func (c cdn) Chunk(ctx context.Context, offset int64, limit int) (chunk, error) {
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r, err := c.cdn.UploadGetCDNFile(ctx, &tg.UploadGetCDNFileRequest{
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Offset: offset,
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Limit: limit,
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FileToken: c.redirect.FileToken,
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})
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if err != nil {
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return chunk{}, err
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}
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switch result := r.(type) {
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case *tg.UploadCDNFile:
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data, err := c.decrypt(result.Bytes, offset)
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if err != nil {
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return chunk{}, err
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}
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return chunk{
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data: data,
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}, nil
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case *tg.UploadCDNFileReuploadNeeded:
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return chunk{}, &ExpiredTokenError{UploadCDNFileReuploadNeeded: result}
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default:
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return chunk{}, errors.Errorf("unexpected type %T", r)
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}
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}
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func (c cdn) Hashes(ctx context.Context, offset int64) ([]tg.FileHash, error) {
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return c.client.UploadGetCDNFileHashes(ctx, &tg.UploadGetCDNFileHashesRequest{
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FileToken: c.redirect.FileToken,
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Offset: offset,
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})
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}
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