Recipe: SSCrasher 1.0

created by LociOiling

Profile

• Name: SSCrasher 1.0
• ID: 103227
• Shared with: Public
• Parent: None
• Children: None
• Created on: January 11, 2020 at 20:57 PM UTC
• Updated on: January 11, 2020 at 20:57 PM UTC
• Description:

  Crashes the Foldit client by attempting to set the secondary structure of an invalid segment.

Code

--[[

    SSCrasher - recipe to crash client by setting secondary structure

    Causes a crash on 20191029-32048a6a12-win_x86-devprev, puzzle 1784.

    Also demonstrates use of xpcall with cleanup function.

    version 1.0 -- 2020/01/11 -- LociOiling
    * new recipe
]]--

--
--  define the main routine
--
--  main does not start executing until it's called by the xpcall statement, 
--  which is the very last line in the recipe
--
function main ()
    Recipe = "SSCrasher"                    -- recipe name
    Version = "1.0"                         -- recipe version

    ReVersion = Recipe .. " " .. Version    -- combined name and version

    print ( ReVersion .. " start" )         -- start the scriptlog output

    local len = structure.GetCount ()
    print ( "segment count = " .. len )     -- actual number of segments

--
--  try to set the secondary structure of the segment beyond the end
--
--  this should cause an exception, which will be caught by the cleanup function
--
--  it may also crash the Foldit client
--
    print ( "attempting to crash Foldit by setting invalid segments to loop" )
    for ii = len + 1, len * 2 do
        print ( "setting segment " .. ii )          -- record last segment
        structure.SetSecondaryStructure ( ii, "L" ) -- set segment to loop
    end

    print ( "no crash, disappointing in a way" )

    cleanup () -- always clean up after yourself
end

--  
--  define the cleanup routine
--
--  the cleanup routine is specified on the xpcall below, 
--  but doesn't run until an exception occurs or the main
--  routine finishes and calls it
--
function cleanup ( errmsg )
    if CLEANUPENTRY ~= nil then
        return
    end
    CLEANUPENTRY = true

    print ( "---" )
    local reason
    local start, stop, line, msg
    if errmsg == nil then
        reason = "complete"
    else
    --
    --  civilized error reporting, thanks to Bruno K. and Jean-Bob
    --
        start, stop, line, msg = errmsg:find ( ":(%d+):%s()" )
        if msg ~= nil then
            errmsg = errmsg:sub ( msg, #errmsg )
        end
        if errmsg:find ( "Cancelled" ) ~= nil then
            reason = "cancelled"
        else
            reason = "error"
        end
    end

    print (  ReVersion .. " " .. reason )

    if reason == "error" then
        print ( "Unexpected error detected" )
        print ( "Error line: " .. line )
        print ( "Error: \"" .. errmsg .. "\"" )
    end

end

--
--  the xpcall below is the first executable statement
--
--  it calls function main, which controls execution 
--  from then on
--
--  if something in function generates an exception, 
--  function cleanup is invoked
--
xpcall ( main, cleanup )

Comments

[LociOiling]

This recipe crashes the Windows client, buildid 20191029-32048a6a12-win_x86-devprev, on puzzle 1784.

Puzzle 1784 has 188 segments, and the recipe attempts to set the secondary structure for segment 189.

The recipe uses the xpcall function, and includes a cleanup routine. Normally, an error like specifying an invalid segment generates an exception, which is then caught by the cleanup routine if you're using xpcall. The usual approach is to then simply end the recipe. The recipe is done, but the client keeps running.

In this case, the cleanup routine is invoked, and reports the error as expected. The client also crashes after this, which is unexpected.

See feedback setting secondary structure of invalid segment crashes client.