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Update presentation on user namespaces

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4
README.md
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@ -37,11 +37,11 @@ Kernel space:
- Entirely disable the SysRq key so that the Secure Attention Key (SAK)
can no longer be utilized. See [documentation](https://www.kicksecure.com/wiki/SysRq).
- Optional - Disable all use of user namespaces.
- Optional - Restrict user namespaces to `CAP_SYS_ADMIN` as they can lead to substantial
privilege escalation.
- Optional - Disable all use of user namespaces.
- Restrict kernel profiling and the performance events system to `CAP_PERFMON`.
- Force the kernel to panic on both "oopses", which can potentially indicate and thwart

43
usr/lib/sysctl.d/990-security-misc.conf
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@ -117,42 +117,41 @@ vm.unprivileged_userfaultfd=0
##
kernel.sysrq=0
## Restrict user namespaces to users with CAP_SYS_ADMIN.
## Disable user namespaces entirely.
## User namespaces aim to improve sandboxing and accessibility for unprivileged users.
## Unprivileged user namespaces pose substantial privilege escalation risks.
## Restricting may lead to breakages in numerous software packages.
##
## Flatpak requires unprivileged users to create new user namespaces for sandboxing.
## https://github.com/flatpak/flatpak/wiki/User-namespace-requirements
## https://salsa.debian.org/debian/bubblewrap/-/blob/debian/latest/debian/README.Debian
## https://forums.kicksecure.com/t/can-not-run-flatpak-apps-after-kicksecure-update/592
##
## Disabling entirely will reduce compatibility with some AppArmor profiles.
## Disabling entirely is known to break the UPower systemd service.
##
## Also breaks (some?) AppImages.
## https://forums.kicksecure.com/t/cannot-run-some-appimage-apps-after-kicksecure-upate/594
##
## Might also break evolution (e-mail client):
## https://forums.kicksecure.com/t/impossible-to-start-evolution-app-since-the-last-update/601
## Not recommended due to well-known breakages across numerous software packages.
##
## https://lwn.net/Articles/673597/
## https://madaidans-insecurities.github.io/linux.html#kernel
## https://gitlab.com/apparmor/apparmor/-/wikis/unprivileged_userns_restriction
## https://github.com/a13xp0p0v/kernel-hardening-checker#questions-and-answers
## https://github.com/NixOS/nixpkgs/pull/84522#issuecomment-614640601
## https://github.com/flatpak/flatpak/wiki/User-namespace-requirements
## https://github.com/Kicksecure/security-misc/pull/263
## https://github.com/Kicksecure/security-misc/issues/274
##
## KSPP=no
## KSPP sets user.max_user_namespaces=0 sysctl, a Linux mainline, stricter setting.
## KSPP sets the sysctl.
##
## kernel.unprivileged_userns_clone is a Debian specific kernel feature. Not Linux mainline.
#kernel.unprivileged_userns_clone=0
## Uncomment the following sysctl to entirely disable user namespaces.
#user.max_user_namespaces=0
## Restrict user namespaces to users with CAP_SYS_ADMIN.
## See the user.max_user_namespaces setting for more details.
## This is a Debian-specific kernel feature, not a Linux mainline setting.
## Unprivileged user namespaces pose substantial privilege escalation risks.
## Flatpak requires unprivileged users to create new user namespaces for sandboxing.
## Restricting is known to cause breakages in some AppImages and the Evolution Email Client.
## Not recommended due to widespread breakages across many software packages.
##
## https://salsa.debian.org/debian/bubblewrap/-/blob/debian/latest/debian/README.Debian
## https://gitlab.com/apparmor/apparmor/-/wikis/unprivileged_userns_restriction
## https://github.com/flatpak/flatpak/wiki/User-namespace-requirements
## https://forums.kicksecure.com/t/can-not-run-flatpak-apps-after-kicksecure-update/592
## https://forums.kicksecure.com/t/cannot-run-some-appimage-apps-after-kicksecure-upate/594
## https://forums.kicksecure.com/t/impossible-to-start-evolution-app-since-the-last-update/601
## https://github.com/Kicksecure/security-misc/issues/274
##
#kernel.unprivileged_userns_clone=0
## Restricts kernel profiling to users with CAP_PERFMON.
## The performance events system should not be accessible by unprivileged users.
## Other distributions such as Ubuntu and Fedora may permit further restricting.