from the mailing list discussion (linked above by @racb), this response from an upstream sudo developer Todd C. Miller:
On Thu, 16 May 2019 07:48:40 -0400, Dan Streetman wrote: > I've cc'ed sudo-users, so the question to the upstream sudo list can > be summarized as: > How likely would it be for upstream sudo to add HOME to env_keep by default? Extremely unlikely. Prior to sudo 1.7.4 the HOME and MAIL environment variables were preserved in the environment by default. This can lead to programs using config files the original user's home directory, which has security implications, so the default was changed in 1.7.4. In the old days, sudo did little more than change the uid. These days sudo tries to run the command in an environment that closely matches what you would get by logging in as that user. This has proven to be safer as it more closely matches the assumptions other programs make. > We ask because Ubuntu carries a patch that adds HOME to env_keep, > unlike the default upstream, or any other Linux/Unix. We are > considering removing that patch, to match upstream defaults, of *not* > including HOME in env_keep. I would be supportive of that. I believe that resetting HOME is the safer default. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to sudo in Ubuntu. https://bugs.launchpad.net/bugs/1556302 Title: Ubuntu patch to add HOME to env_keep makes custom commands vulnerable by default Status in sudo package in Ubuntu: Confirmed Bug description: I wanted to allow certain users to execute a python script as another user, so I created the following sudoers config: Defaults env_reset source_user ALL=(target_user) NOPASSWD: /home/target_user/bin/script.py This results in a highly insecure Python environment because the source user can set HOME and override any Python package by putting files in $HOME/.local/lib/python*/site-packages/. This should be a safe configuration because the default behaviour (as specified in the man page) is that env_reset will replace HOME with the target user's home directory. The "env_reset" option even has special behaviour for bash which has its own potential environment vulnerabilities. However there is an Ubuntu-specific patch in the package (keep_home_by_default.patch) that makes sudo preserve HOME by default, which negates the correct behaviour of "env_reset". It should not be necessary to explicitly specify the "always_set_home" option in order to negate this patch. The patch should be removed and the default /etc/sudoers should explicitly add HOME to "env_keep" for the "allow admins to run any command as root" entries, to get the desired behaviour without creating security issues for other sudoers commands. Note: for quick reference to anyone coming to this bug, this behavior (of sudo keeping the calling user's $HOME) can be disabled by running 'sudo visudo' and adding this line: Defaults always_set_home To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/sudo/+bug/1556302/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
