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Date: Sun, 19 Nov 2023 07:11:37 -0500
From: "Mike O'Connor" <mjo@...o.mi.org>
To: oss-security@...ts.openwall.com
Subject: Re: hplip: security issues in `hpps` program due to
fixed /tmp path usage in prnt/hpps/hppsfilter.c
[removing security@....com from the Cc:]
This is for hp.com product security, not hpe.com. HP and HPE are two
separate companies, and HPE isn't the printer company.
To report a potential security vulnerability with a HP product,
contact: hp-security-alert@...com
Both HPE and HP are CVE CNAs. Here's HP's CVE CNA information:
https://www.cve.org/PartnerInformation/ListofPartners/partner/hp
HTH,
-Mike
:Thanks for making the community aware of this issue.
:
:Perhaps security@....com can help to route internally to get a CVE issued
:and find the appropriate owners to fix.
:
:
:On Fri, Nov 17, 2023 at 1:38 AM Matthias Gerstner <mgerstner@...e.de> wrote:
:
:> Hello list,
:>
:> this report is about the problematic use of fixed temporary paths in the
:> `hpps` program from the hplip [1] project. Hplip is a collection of
:> utilities for HP printer and scanner devices.
:>
:> There is currently no upstream fix available for this issue and this
:> publication happens after 90 days of attempted coordinated disclosure,
:> but upstream did not react to my report.
:>
:> This report is based on the latest upstream release 3.23.8 [2] of hplip.
:>
:> The Issue
:> =========
:>
:> The program /usr/lib/cups/filter/hpps uses a number of insecure fixed
:> temporary files that can be found in prnt/hpps/hppsfilter.c:
:>
:> prnt/hpps/hppsfilter.c:1027: sprintf(booklet_filename, "/tmp/%
:> s.ps","booklet");
:> prnt/hpps/hppsfilter.c:1028: sprintf(temp_filename, "/tmp/%s.ps
:> ","temp");
:> prnt/hpps/hppsfilter.c:1029: sprintf(Nup_filename, "/tmp/%s.ps
:> ","NUP");
:>
:> These paths are only used if "booklet printing" is enabled. For testing,
:> the
:> logic can be forced by invoking the program similar to this:
:>
:> $ export
:> PPD=/usr/share/cups/model/manufacturer-PPDs/hplip-plugin/hp-laserjet_1020.ppd.gz
:> $ /usr/lib/cups/filter/hpps some-job some-user some-title 10
:> HPBookletFilter=10,fitplot,Duplex=DuplexTumble,number-up=1
:>
:> The program will expect data to print on stdin this way. Just typing in
:> some random data and pressing Ctrl-d will make it continue. There is a
:> chance that it will crash, tough, since error returns from parsing
:> errors are largely not checked in this program.
:>
:> The three paths are created and opened using `fopen()`, so no special
:> open flags are in effect that would prevent following symlinks, also the
:> `O_EXCL` flag is missing to prevent opening existing files. The
:> resulting system calls look like this (for creation / opening for
:> reading):
:>
:> openat(AT_FDCWD, "/tmp/temp.ps", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
:> openat(AT_FDCWD, "/tmp/temp.ps", O_RDONLY)
:>
:> Furthermode there is a `chmod()` on the /tmp/temp.ps file:
:>
:> hppsfilter.c:110 chmod(temp_filename, S_IRUSR | S_IWUSR | S_IRGRP |
:> S_IROTH);
:>
:> The data to print (from stdin) is written to this file, and the file is
:> also made world readable explicitly via this `chmod()`. The issues with
:> these paths are multifold:
:>
:> - There is a local information leak, since the print job data will
:> become visible to everybody in the system.
:> - There is violated data integrity, since other users can pre-create these
:> files and manipulate e.g. the data to print.
:> - This may allow to create files in unexpected places, by placing symbolic
:> links, if the Linux kernel's symlink protection is not active.
:> - Similarly it may allow to grant world read privileges to arbitrary
:> files by following symlinks during the `chmod()`.
:> - It may allow further unspecified impact if crafted data is placed into
:> /tmp/temp.ps which is processed by the complex `PS_Booklet()` function.
:>
:> I did not research the impact of the issue further to see whether this
:> could lead to local code execution in the context of the user that is
:> invoking `hpps`.
:>
:> Suggested Patch
:> ===============
:>
:> To fix this issue all three fixed temporary paths need to be replaced by
:> unpredictably named temporary files that are safely created. Attached to
:> this email is a patch that I authored that accomplishes this. This patch
:> also drops the `chmod()`. The purpose of it is unclear, so it is
:> possible that this breaks something, if other processes with different
:> privileges need to access this file.
:>
:> There is no patch or any other information available from upstream.
:>
:> Affectedness
:> ============
:>
:> Since, to my knowledge, there is no public version control system for
:> hplip, it is difficult to determine when this issue has been introduced.
:> By taking some samples from older SUSE distributions I found the issue
:> to be present at least since upstream release 3.19.12 from 2019-12-12.
:>
:> CVE Assignment
:> ==============
:>
:> Since HP is a CVE CNA, it is itself responsible for assigning a CVE.
:> Since there is no reaction from upstream I don't know if or when CVEs
:> will be available.
:>
:> Timeline
:> ========
:>
:> 2023-08-21: I reported the finding privately to upstream via Launchpad [3],
:> offering coordinated disclosure. No other means of contact are
:> documented for hplip.
:> 2023-09-05: Since I did not get any feedback yet I urged upstream via
:> Launchpad to provide a response.
:> 2023-10-04: I shared the suggested patch with upstream, still no response.
:> 2023-11-17: The 90 days maximum embargo time we offer approached and we
:> published the finding.
:>
:> References
:> ==========
:>
:> [1]: https://sourceforge.net/projects/hplip
:> [2]: https://sourceforge.net/projects/hplip/files/hplip/3.23.8
:> [3]: https://bugs.launchpad.net/hplip/+bug/2032375
:>
:> --
:> Matthias Gerstner <matthias.gerstner@...e.de>
:> Security Engineer
:> https://www.suse.com/security
:> GPG Key ID: 0x14C405C971923553
:>
:> SUSE Software Solutions Germany GmbH
:> HRB 36809, AG Nürnberg
:> Geschäftsführer: Ivo Totev, Andrew McDonald, Werner Knoblich
:>
--
Michael J. O'Connor mjo@...o.mi.org
=--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--=
"Why make trillions when we could make... billions?" -Dr. Evil
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