Re: [PATCH] gitk: use mktemp -d to avoid predictable temporary directories

On Sun, Jun 15, 2014 at 04:32:27PM +0000, brian m. carlson wrote:

On Sun, Jun 15, 2014 at 08:51:23AM +0100, Pat Thoyts wrote:

quoted

David Aguilar [off-list ref] writes:

quoted

--- a/gitk
+++ b/gitk

@@ -3502,7 +3502,8 @@ proc gitknewtmpdir {} {

	} else {
	    set tmpdir $gitdir
	}
-	set gitktmpdir [file join $tmpdir [format ".gitk-tmp.%s" [pid]]]
+	set gitktmpformat [file join $tmpdir ".gitk-tmp.XXXXXX"]
+	set gitktmpdir [exec mktemp -d $gitktmpformat]
	if {[catch {file mkdir $gitktmpdir} err]} {
	    error_popup "[mc "Error creating temporary directory %s:" $gitktmpdir] $err"
	    unset gitktmpdir

This is a problem on Windows where we will not have mktemp. In Tcl 8.6
the file command acquired a "file tempfile" command to help with this
kind of issue (https://www.tcl.tk/man/tcl8.6/TclCmd/file.htm#M39) but
for older versions we should probably stick with the existing pattern at
least on Windows.

The existing pattern is a security bug on Unix systems. MITRE (CWE-377)
tells me that it is a vulnerability on Windows as well, so you'd
probably want to come up with a better solution than the existing
pattern.

You also probably want to request a CVE for this, which the Red Hat and
Debian security teams can do for you if you like.  Distributions will
likely want to issue security advisories for this.

I don't think this requires a CVE since it's basically plugging a hole
that my previous patch introduced by making gitk honor the TMPDIR
variable; it hasn't strictly been in any release yet.

Does Git on Windows use a modern tcl?
I checked, and my (old) existing msysgit installation had tcl
8.5, so I unfortunately using "file tempname" won't help there.

Hmm.. I guess what I could do is keep the old behavior (having gitk ignore TMPDIR)
on Windows and only use the new code path on non-Windows.

That seems like it'd be the simplest implementation (no need to check versions)
and the least harmful to existing users (avoids a tcl upgrade or mkdtemp installation
for Windows users).
-- 
David