This bug was fixed in the package fscrypt - 0.2.2-0ubuntu2.1 --------------- fscrypt (0.2.2-0ubuntu2.1) bionic-security; urgency=medium
* SECURITY UPDATE: Privilege escalation via improperly restored supplementary groups in libpam-fscrypt (LP: #1787548) - CVE-2018-6558.patch: Save the euid, egid, and supplementary groups when entering the PAM module, drop privileges to perform actions on behalf of the user, and then properly restore the saved values before exiting the PAM module. Based on patch from upstream. - CVE-2018-6558 * 0001-security-drop-and-regain-privileges-in-all-threads.patch: Drop and regain privileges in all threads of the current process * 0001-Ensure-keyring-privilege-changes-are-reversible.patch: Ensure keyring privilege changes are reversible to prevent failures when, for example, "su <user>" is executed as an unprivileged user -- Tyler Hicks <tyhi...@canonical.com> Wed, 22 Aug 2018 18:57:26 +0000 ** Changed in: fscrypt (Ubuntu) Status: Confirmed => Fix Released -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to shadow in Ubuntu. https://bugs.launchpad.net/bugs/1787548 Title: PAM fscrypt adds root(0) group to all users called by su Status in Shadow: Invalid Status in fscrypt package in Ubuntu: Fix Released Status in shadow package in Ubuntu: Invalid Bug description: related packages: /bin/su (from login , shadow) OS: ubuntu 18.04.1, updated Bug: a normal user (not in 'root' group), when the PAM module fscrypt is active, all calls of su give the user additional group root(0). Results: this is a permission escalation, such user can now delete files owned by root group (where permisions are g+w) Steps to reproduce: 0/ login uses pam unix authentication module (default on ubuntu, no action needed) 0.1/ create a new user: # useradd developer 1/ verify: #id developer // on my system, shows // uid=1004(developer) gid=1004(developer) groups=1004(developer) \su - developer -c id sudo -u developer id 2/ enable pam-fscrypt # apt install libpam-fscrypt # pam-auth-update --enable fscrypt 3/ verify again (bug shows) // repeate step 1/ // the su command will show the bug (sudo won't, interestingly) \su - developer -c id // uid=1004(developer) gid=1004(developer) groups=1004(developer),0(root) 4/ workaround and return to original state: pam-auth-update --disable fscrypt apt remove libpam-fscrypt Thank you, To manage notifications about this bug go to: https://bugs.launchpad.net/shadow/+bug/1787548/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp