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On Tue, Jan 9, 2024 at 12:45 AM Harry Sintonen <harry () sintonen fi> wrote:

On Mon, 8 Jan 2024, Georgi Guninski wrote:

When extracting archives cpio (at least version 2.13) preserves
the setuid flag, which might lead to privilege escalation.

So does for example tar. The same rules that apply to tar also apply to
cpio:

Hi, thanks for the feedback :)

Which version of tar is vulnerable to this attack? I am pretty sure
this was fixed in tar and zip `long long` ago.

tar and zip on fedora 38 are definitely not vulnerable, they clear
the setuid bit.

I continue to suspect this is vulnerability because:
1. There is directory traversal protection for untrusted archives
2. tar and zip and not vulnerable

bash script for setuid files in tar:


#!/bin/bash

mkdir -p /tmp/1 ; cd /tmp/1 ; :> a
chmod 4755 a ; tar cvf a.tar a
mkdir -p /tmp/2 ; cd /tmp/2 ; tar xvf /tmp/1/a.tar
ls -lh /tmp/1/a
#-rwsr-xr-x. 1 joro joro 0 Jan  9 06:13 /tmp/1/a #original setuid
ls -lh /tmp/2/a
#-rwxr-xr-x. 1 joro joro 0 Jan  9 06:13 /tmp/2/a #NOT setuid
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Current thread:

• cpio privilege escalation vulnerability via setuid files in cpio archive Georgi Guninski (Jan 08)
  • Re: cpio privilege escalation vulnerability via setuid files in cpio archive fulldisclosure (Jan 14)
  • Re: cpio privilege escalation vulnerability via setuid files in cpio archive Harry Sintonen via Fulldisclosure (Jan 14)
    • Re: cpio privilege escalation vulnerability via setuid files in cpio archive Georgi Guninski (Jan 14)
      • Re: cpio privilege escalation vulnerability via setuid files in cpio archive Harry Sintonen via Fulldisclosure (Jan 14)