Fix Extended Clipboard implementation issues #561
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According to zlib manual (https://zlib.net/manual.htm): "inflate() returns Z_OK if some progress has been made (more input processed or more output produced), Z_STREAM_END if the end of the compressed data has been reached and all uncompressed output has been produced"
Text data sent via extended clipboard encoding is null-terminated and this null character is counted in the length field sent to server.
E.g. for "abc", bytes {'a', 'b', 'c', '\0'} are sent with length = 4.
Many servers can't handle zlib streams created by compress() function of zlib library. Primary bug is that these servers don't expect inflate() to return Z_STREAM_END, which is the case for streams created by compress(). Affected servers: LibVNCServer UltraVNC TigerVNC (<= 1.10)
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cc @wuhanck |
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it looks ok. it is safer if client dont include \0 in the end. |
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According to spec, clipboard text is null terminated and text length includes the null byte. This is how LibVNCServer and other clients encode this. Fixed by 2nd commit 7ff0a53
This is a big one. Many servers (including LibVNCServer) can't properly handle zlib streams created by
compress()function of zlib library. When decompressing such streams,inflate()correctly returnsZ_STREAM_END, but these servers are only expectingZ_OK. So they end up crashing, while LibVNCserver abruptly disconnects from client.This is probably why the original PR Libvncclient clipboard utf8 support #552 was not working. New PR simply suppressed it by adding extra byte, which made
inflate()returnZ_OK.Solution: