clipboard_file: cannot handle files more than 2GiB unintendedly and HUGE_FILE_SUPPORT

[metalefty]

I found that clipboard file transfer might not work properly if the filesize > 4GiB.

Also, there are some codes using int that might have values of more than 2^32 like #1087.

I started adding some tests for this.

xrdp/sesman/chansrv/clipboard_file.c

Lines 53 to 60 in b481351

	struct cb_file_info
	{
	char pathname[256];
	char filename[256];
	int flags;
	int size;
	tui64 time;
	};

xrdp/sesman/chansrv/clipboard_file.c

Line 191 in b481351

cfi->size = g_file_get_size(full_fn);

xrdp/common/os_calls.c

Lines 2493 to 2494 in b481351

	int
	g_file_get_size(const char *filename)

[matt335672]

Good point.

int is going to be signed, so potentially 2Gb rather than 4Gb isn't it?

What do you think about the idea of using off_t from <sys/types.h> for this? We're already using it for the FUSE stuff, as it's in the FUSE data structures.

We should also consider g_file_seek() in this.

I think most uses could be found quite easily

1. Rename g_file_get_size() and g_file_seek() as zzzz_g_file_get_size() and zzzz_g_file_seek()
2. Fix these functions to work correctly with off_t (or whatever)
3. Recompile and fix references to zzzz_, changing types along the way. Where calls are assigned to variables or struct members, give these variables a prefix of zzzz_ also.
4. Use github actions locally to check everything is OK.
5. When all is working, remove all the zzzz_ with something like (I HAVEN'T TESTED THIS):-

filelist=$(find . -type f -exec grep zzzz_ {} +)
echo $filelist ; Check it looks sane
for file in $filelist; do sed -i -e 's/zzzz_//g'; ;done

Does that make sense? Will it work OK?

[metalefty]

Indeed, it is actually 2GiB.

Also, it sounds good to me to use off_t instead.

The steps you show makes sense to me, I'll give it a try.

[metalefty]

I found that the file size transferred over the clipboard is limited to 4 GiB in protocol design.

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpeclip/7718c8c9-798d-4788-bb75-64afdc913869

Indicates support for transferring files that are larger than 4,294,967,295 bytes in size. If this flag is not set, then only files of size less than or equal to 4,294,967,295 bytes can be exchanged using the File Contents Request PDU and File Contents Response PDU.

Large file (4GiB) support will be implemented as an extension and indicated by CB_HUGE_FILE_SUPPORT_ENABLED.

xrdp/sesman/chansrv/clipboard.c

Lines 238 to 240 in b367f57

	static int g_cliprdr_flags = CB_USE_LONG_FORMAT_NAMES |
	CB_STREAM_FILECLIP_ENABLED |
	CB_FILECLIP_NO_FILE_PATHS;

However, g_file_get_size() returns file size as signed int. So the first goal is to extend 2GiB file size limit to 4GiB.

[matt335672]

Sounds reasonable.

We'll still need to pass an error back from g_get_file_size() somehow though, if we don't use off_t or something like it.