-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-EN-24:11.ldns Errata Notice The FreeBSD Project Topic: LDNS uses nameserver commented out in resolv.conf Category: contrib Module: ldns Announced: 2024-06-19 Credits: Michael Gmelin Dag-Erling Smørgrav Affects: FreeBSD 13.3 and FreeBSD 14.0. Corrected: 2024-05-20 09:04:54 UTC (stable/14, 14.0-STABLE) 2024-06-19 20:36:59 UTC (releng/14.0, 14.0-RELEASE-p7) 2024-05-20 09:04:59 UTC (stable/13, 13.3-STABLE) 2024-06-19 20:37:08 UTC (releng/13.3, 13.3-RELEASE-p3) For general information regarding FreeBSD Errata Notices and Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background LDNS is a DNS library that facilitates DNS tool programming. II. Problem Description Due to a bug in the library's configuration file parser, commented out configuration settings in /etc/resolv.conf were picked up by the LDNS resolver, potentially leading to malfunction and/or information leakage. This included, but was not limited to, the nameserver setting. Given this example # /etc/resolv.conf # nameserver 8.8.8.8 nameserver 127.0.0.1 DNS requests were sent to the commented out external resolver instead of the local one. III. Impact Programs using the LDNS library might behave in unexpected ways. Name resolution could be inconsistent with what other tools which use libc return, e.g., `ping` vs. `host`. DNS request containing private information could leak to third parties. A system's attack surface is increased. Affected tools include host(1), drill(1), and ssh(1), which uses LDNS in the VerifyHostKeyDNS feature to fetch SSHFP records. IV. Workaround Removing empty lines from /etc/resolv.conf mitigates the problem: sed -i '' '/^[[:space:]]*$/d' /etc/resolv.conf V. Solution Upgrade your system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. Perform one of the following: 1) To update your system via a binary patch: Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms, or the i386 platform on FreeBSD 13, can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install 2) To update your system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch https://security.FreeBSD.org/patches/EN-24:11/ldns.patch # fetch https://security.FreeBSD.org/patches/EN-24:11/ldns.patch.asc # gpg --verify ldns.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in . Restart all daemons that use the library, or reboot the system. VI. Correction details This issue is corrected as of the corresponding Git commit hash in the following stable and release branches: Branch/path Hash Revision - ------------------------------------------------------------------------- stable/14/ 7daf36028411 stable/14-n267742 releng/14.0/ bdf75e830a77 releng/14.0-n265418 stable/13/ e95e16191f63 stable/13-n257915 releng/13.3/ d45cf1d2f124 releng/13.3-n257434 - ------------------------------------------------------------------------- Run the following command to see which files were modified by a particular commit: # git show --stat Or visit the following URL, replacing NNNNNN with the hash: To determine the commit count in a working tree (for comparison against nNNNNNN in the table above), run: # git rev-list --count --first-parent HEAD VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEthUnfoEIffdcgYM7bljekB8AGu8FAmZzRTkACgkQbljekB8A Gu9BYBAApSQZbv3wgT5PhJRsaCulmOZOH5gywlVdaBA1I4sDF3on0CFwLQfy7lLH q2xFEfll5vBVbfGCVp2zVBgb4IyknqMgf8Ae4uBEEJJejRgxxnFTnQmdlzg7a8TR 9UW3g6QB/5tUIGrxFqIdx4qRAQz1ie6NwR+KvP8ojXk0xVscKIaijXACbmAgT6nH HygG7snrB9VmMMlRIHYhoarhRBd+aX68Jg3F+yGUX76FB4HVMSFMYo0fEWgi7SQ3 psZfq54GvCH+kSvYduXS3QkTJ7N/S9p6JAVraRlJmFnjQ69qE7u59bc68zW0D2pn Pj6/c0OZtWE2SQGqCuqgnBffjArisAJ/BKiK/XeO8B1fSvaVKJToR18+6KGTmc0f nnqQLxFeGbh5gHHcM8QaLBJFUgm5TVvdevcDmLuiVMSvQyt5iC6rIGwb3UNYAnW7 w/UFSresVKppsB2JDqyGjaSf2FI00rYIKHChZ8nkKYPMhb6V/TJZr3k25/3idbvi 6zO7wfbOhwAYQ44Mg/gY/v206qpoYiZO2tMQazbiicOqBOQBYWdXsojYhCB6qkyU ++kBNAMugpOAsDkIvN9mWLniRnvycrbEqthQlmfR7X3tZRiuz+0S1alx03Z5VsP6 zM5//i6W2Lt8DmX34zQDeQAMTZXD3bG1JSe2UbKyZkL20vrSTfg= =lQUa -----END PGP SIGNATURE-----