Re: [musl] Bug: installed symlinks are unreadable on MacOS

[Tim Cuthbertson <tim@gfxmonk.net>]

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Ah that makes sense, attached an updated patch. I don't know whether the
`umask 077` after making the symlink is strictly necessary but it might
avoid nasty surprises later on in the script.

Cheers,
- Tim

On Thu, 1 Feb 2024 at 10:32, Rich Felker <dalias@libc.org> wrote:

> On Thu, Feb 01, 2024 at 09:39:56AM +1100, Tim Cuthbertson wrote:
> > Yeah, setting it to `chmod 000` in just the symlink branch seems good to
> me
> > too.
> >
> > Looking at the script more closely, `mode` is always set and so I'm
> unclear
> > why there is also a `umask 077` at all. Whatever permissions we create
> the
> > file with, we `chmod` it explicitly before doing anything else.
> >
> > Is that line just there to undo the potential change to `umask` in the
> > mkdirp branch? If so, maybe that should be done explicitly by capturing
> the
> > old umask? e.g:
>
> No, it's so that the install.sh never exposes a file to users who
> should not have access to it via the existing umask being more
> permissive than the requested install mode. Normally this does not
> matter for use as part of musl's install process, but the script is
> written to be general and not have security bugs like that.
>
> Rich
>

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commit 60ab5657d006f36032fe5a348349f9c38330ed91
Author: Tim Cuthbertson <tim@gfxmonk.net>
Date:   Wed Jan 31 12:45:06 2024 +1100

    install.sh: clear umask when making a symlink, so permissions on MacOS match Linux

diff --git a/tools/install.sh b/tools/install.sh
index d913b60b..855a8ca2 100755
--- a/tools/install.sh
+++ b/tools/install.sh
@@ -48,7 +48,9 @@ trap 'rm -f "$tmp"' EXIT INT QUIT TERM HUP
 umask 077
 
 if test "$symlink" ; then
+umask 000
 ln -s "$1" "$tmp"
+umask 077
 else
 cat < "$1" > "$tmp"
 chmod "$mode" "$tmp"