mod_http_file_share: Handle out of bounds Range request

Turns out you can seek past the end of the file without getting an
error.

Also rejects empty range instead of sending the whole file.

1 files changed, 8 insertions, 3 deletions

diff --git a/plugins/mod_http_file_share.lua b/plugins/mod_http_file_share.lua
index 4b6030bf..ba6b97c5 100644
--- a/plugins/mod_http_file_share.lua
+++ b/plugins/mod_http_file_share.lua
@@ -361,10 +361,15 @@ function handle_download(event, path) -- GET /uploads/:slot+filename
 	if request_range then
 		local range_start, range_end = request_range:match("^bytes=(%d+)%-(%d*)$")
 		-- Only support resumption, ie ranges from somewhere in the middle until the end of the file.
-		if (range_start and range_start ~= "0" and range_start ~= filesize) and (range_end == "" or range_end == filesize) then
-			if handle:seek("set", tonumber(range_start)) then
+		if (range_start and range_start ~= "0") and (range_end == "" or range_end == filesize) then
+			local pos, size = tonumber(range_start), tonumber(filesize);
+			local new_pos = pos < size and handle:seek("set", pos);
+			if new_pos and new_pos < size then
 				response_range = "bytes "..range_start.."-"..filesize.."/"..filesize;
-				filesize = string.format("%d", tonumber(filesize)-tonumber(range_start));
+				filesize = string.format("%d", size-pos);
+			else
+				handle:close();
+				return 416;
 			end
 		end
 	end