3 Commits

Author	SHA1	Message	Date
Ryan Wilson	2665425176	core: Set /proc/pid/setgroups to allow for PrivateUsers=full ... When trying to run dbus-broker in a systemd unit with PrivateUsers=full, we see dbus-broker fails with EPERM at `util_audit_drop_permissions`. The root cause is dbus-broker calls the setgroups() system call and this is disallowed via systemd's implementation of PrivateUsers= by setting /proc/pid/setgroups = deny. This is done to remediate potential privilege escalation vulnerabilities in user namespaces where an attacker can remove supplementary groups and gain access to resources where those groups are restricted. However, for OS-like containers, setgroups() is a pretty common API and disabling it is not feasible. So we allow setgroups() by setting /proc/pid/setgroups to allow in PrivateUsers=full. Note security conscious users can still use SystemCallFilter= to disable setgroups() if they want to specifically prevent this system call. Fixes: #35425	2024-12-12 11:36:10 +00:00
Ryan Wilson	705cc82938	core: Add PrivateUsers=full ... Recently, PrivateUsers=identity was added to support mapping the first 65536 UIDs/GIDs from parent to the child namespace and mapping the other UID/GIDs to the nobody user. However, there are use cases where users have UIDs/GIDs > 65536 and need to do a similar identity mapping. Moreover, in some of those cases, users want a full identity mapping from 0 -> UID_MAX. Note to differentiate ourselves from the init user namespace, we need to set up the uid_map/gid_map like: ``` 0 0 1 1 1 UINT32_MAX - 1 ``` as the init user namedspace uses `0 0 UINT32_MAX` and some applications - like systemd itself - determine if its a non-init user namespace based on uid_map/gid_map files. Note systemd will remove this heuristic in running_in_userns() in version 258 and uses namespace inode. But some users may be running a container image with older systemd < 258 so we keep this hack until version 259. To support this, we add PrivateUsers=full that does identity mapping for all available UID/GIDs. Fixes: #35168	2024-12-05 10:34:32 -08:00
Daan De Meyer	fa693fdc7e	core: Add support for PrivateUsers=identity ... This configures an indentity mapping similar to systemd-nspawn --private-users=identity.	2024-09-09 18:31:01 +02:00