[tex-live] TL 2024: lua's file.is_writable() broken

[Dr. Werner Fink]

On 2024/03/21 11:53:52 +0100, Dr. Werner Fink wrote:
> On 2024/03/21 10:54:14 +0100, Dr. Werner Fink wrote:
> > Hi,
> > 
> > I have a report that e.g. python-Sphinx testr code breaks at internal
> > test call
> > 
> >   lualatex --halt-on-error --interaction=nonstopmode sphinxtest.tex
> > 
> > ... now after adding some debug messages
> > 
> >   /abuild/oscbuild/standard/usr/share/texmf/tex/luatex/luaotfload/fontloader-reference.lua
> > 
> > with
> > 
> >     for i=1,#cachepaths do
> >         local cachepath = cachepaths[i]
> >         print("XXXX cache path " .. cachepath)
> >         if file.is_writable("/home/abuild/") then
> >           print("YYYY cache path writable")
> >         else
> >           print("YYYY cache path not writable")
> >         end
> >         if file.is_writable(".") then
> >           print("YYYY cache path writable")
> >         else
> >           print("YYYY cache path not writable")
> >         end
> >     [...]
> > 
> > I see at stdout
> > 
> >   This is LuaHBTeX, Version 1.18.0 (TeX Live 2024/TeX Live for opensuse.org) 
> >    restricted system commands enabled.
> >   (./sphinxcrash.tex
> >   LaTeX2e <2023-11-01> patch level 1
> >   L3 programming layer <2024-02-20>
> >   XXXX cache path /home/abuild/.cache/texmf/fonts
> >   YYYY cache path not writable
> >   YYYY cache path writable
> > 
> > which is somehow a suprise as the user abuild is owner of its home which
> > means that the call file.is_writable lies on /home/abuild/
> > 
> >   abuild at noether:/home/abuild/rpmbuild/BUILD> pwd
> >   /home/abuild/rpmbuild/BUILD
> >   abuild at noether:/home/abuild/rpmbuild/BUILD> whoami 
> >   abuild
> >   abuild at noether:/home/abuild/rpmbuild/BUILD> stat /home/abuild/
> >     File: /home/abuild/
> >     Size: 154             Blocks: 0          IO Block: 4096   directory
> >   Device: 8,17    Inode: 1081575903  Links: 6
> >   Access: (0755/drwxr-xr-x)  Uid: (  399/  abuild)   Gid: (  399/  abuild)
> >   Access: 2024-03-21 09:04:27.553841693 +0000
> >   Modify: 2024-03-21 09:36:35.453417724 +0000
> >   Change: 2024-03-21 09:36:35.453417724 +0000
> >    Birth: 2024-03-21 08:08:32.891190086 +0000
> > 
> > The strace show at this call
> > 
> >   9776  write(1, "XXXX cache path /home/abuild/.cache/texmf/fonts", 47) = 47
> >   9776  write(1, "\n", 1)                 = 1
> >   9776  newfstatat(AT_FDCWD, "/home/abuild", {st_mode=S_IFDIR|0755, st_size=154, ...}, 0) = 0
> >   9776  write(1, "YYYY cache path not writable", 28) = 28
> >   9776  write(1, "\n", 1)                 = 1
> >   9776  newfstatat(AT_FDCWD, ".", {st_mode=S_IFDIR|0755, st_size=135, ...}, 0) = 0
> >   9776  openat(AT_FDCWD, "./m_t_x_t_e_s_t.tmp", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 5
> >   9776  close(5)                          = 0
> >   9776  unlink("./m_t_x_t_e_s_t.tmp")     = 0
> >   9776  write(1, "YYYY cache path writable", 24) = 24
> >   9776  write(1, "\n", 1)                 = 1
> > 
> > OK this is secure ... very secure but totally unusable
> 
> Adding further debug code in
> 
>   /usr/share/texmf/tex/luatex/lualibs/lualibs-basic-merged.lua
> 
>   if lfs.isreadablefile and lfs.iswritablefile then
>    file.is_readable=lfs.isreadablefile
>    file.is_writable=lfs.iswritablefile
>   else
>    function file.is_writable(name)
>     if not name then
>     elseif lfs.isdir(name) then
>      name=name.."/m_t_x_t_e_s_t.tmp"
>      local f=io.open(name,"wb")
>      print("FILE " .. name)
>      if f then
>       f:close()
>       os.remove(name)
>       return true
>      end
>     elseif lfs.isfile(name) then
> 
> shows
> 
>   This is LuaHBTeX, Version 1.18.0 (TeX Live 2024/TeX Live for opensuse.org) 
>    restricted system commands enabled.
>   (./sphinxcrash.tex
>   LaTeX2e <2023-11-01> patch level 1
>   L3 programming layer <2024-02-20>
>   FILE /var/cache/texmf/fonts/m_t_x_t_e_s_t.tmp
>   XXXX cache path /home/abuild/.cache/texmf/fonts
>   FILE /home/abuild/m_t_x_t_e_s_t.tmp
>   YYYY cache path not writable
>   FILE ./m_t_x_t_e_s_t.tmp
>   YYYY cache path writable
>   FILE /home/abuild/.cache/texmf/fonts/m_t_x_t_e_s_t.tmp
> 
> means that open the file
> 
>   /home/abuild/m_t_x_t_e_s_t.tmp
> 
> is not done even if possible
> 
>   abuild at noether:/home/abuild/rpmbuild/BUILD> touch /home/abuild/m_t_x_t_e_s_t.tmp
>   abuild at noether:/home/abuild/rpmbuild/BUILD> echo $?
>   0
>   abuild at noether:/home/abuild/rpmbuild/BUILD> rm /home/abuild/m_t_x_t_e_s_t.tmp
> 
> but false returned at the end of function file.is_writable()
> 
> Could anyone explain why io.open() does not accept absolute paths?
> And how to fix this?
> 

Broken by design ... from /etc/texmf/web2c/texmf.cnf

 % Do we allow TeX \input or \openin (openin_any), or \openout
 % (openout_any) on filenames starting with `.' (e.g., .rhosts) or
 % outside the current tree (e.g., /etc/passwd)?
 % a (any)        : any file can be opened.
 % r (restricted) : disallow opening dot files
 % p (paranoid)   : as `r' and disallow going to parent directories, and
 %                  restrict absolute paths to be under $TEXMFOUTPUT.
 openin_any = a
 openout_any = p

 % Write .log/.dvi/.aux/etc. files here, if they can't be written in the
 % current directory.
 % 
 % Best to use this only when a particular job requires it, not set
 % globally in a configuration file or the environment. We recommend
 % using it transiently for particular jobs, not making a permanent setting.
 %TEXMFOUTPUT = /tmp

... as io.open() goes to luatex_io_open() which uses
kpse_out_name_ok_silent_extended() ... kpathsea_out_name_ok_silent_extended()
... kpathsea_out_name_ok_1() ... kpathsea_name_ok()


Werner

-- 
  "Having a smoking section in a restaurant is like having
          a peeing section in a swimming pool." -- Edward Burr
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