[HOME] [DOWNLOAD] [DOCS] [NEWS] [SUPPORT] [TIPS] [ISSUES] [DONATE]

Kernel Hardening

1 Like

Could you please have a look here?

https://outflux.net/blog/

1 Like
1 Like

Most seem to be kernel config options. Not things that can be changed via sysctl or boot parameters.

One that does look interesting though is page_alloc.shuffle=1 although this is only for later kernel versions. Debian will likely enable this by default once it comes.

There’s nothing here we don’t already do or would require a custom kernel.

Also, Copperhead is not a good source anymore after they kicked out Daniel Micay and started scamming users.

2 Likes

@madaidan can you also exempt sysrq + f from being blocked?

This key is particularly useful when killing a hanging process considering swap is disabled on the host for Whonix live mode to be traceless.

Call oom_kill, which kills a process to alleviate an OOM condition f

2 Likes

Indeed.

perhaps it is more efficient to tell ujpstream to not include map files in the package?

Does removing them add any protection for a publicly compiled kernel anyhow?

2 Likes

I don’t see how this is any better than just using Ctrl + C or kill -9.

They likely won’t want to do that as the map files are good for debugging.

It would protect against malware attempting to check for local files instead of having to use another source.

1 Like

sysrq is immediately applied when the whole machine is stalled and you can’t really open a terminal and type anything. Also isn’t Ctrl + C just the copy command?

2 Likes

Ctrl + C seems fine for that then.

No, Ctrl + C sends the SIGINT command to kill a process. For example, run yes in a terminal and press Ctrl + C to kill it. Ctrl + D can also be used to kill an open terminal.

1 Like

madaidan via Whonix Forum:

There’s nothing here we don’t already do or would require a custom kernel.

Also, Copperhead is not a good source anymore after they kicked out Daniel Micay and started scamming users.

I didn’t follow these developments. However, possibly these these
websites are still the same as created by Daniel Micay and never updated
since. Also, we’d use them as as inspiration (like from any source
anyway), and then independently verify all claims (before we make
changes on our side) not for face value.

1 Like

madaidan via Whonix Forum:

Ctrl + C seems fine for that then.

When the whole machine appears frozen Ctrl + C won’t have any effect.
sysrq might work.

2 Likes

Of course, but we shouldn’t be too trusting of Copperhead.

If Ctrl + C doesn’t work, I doubt sysrq would.

@onion_knight wrote in VMs do no start until the CPU configuration is set to “Copy host CPU configuration”

sysrq is immediately enforced by a running kernel. That’s what makes these commands so special. If there isn’t a security argument against it, please add it to the mask.

1 Like

Can a user only kill it’s own processes with it or any process?

What if an unprivileged user kills a very important process that is usually only accessible by root?

1 Like

It seems that restricting sysrq was unnecessary as no non admin/root user is allowed to trigger it. A process with root privileges has many more options for killing a process or doing worse.

https://www.kernel.org/doc/html/v4.14/admin-guide/sysrq.html

Note that the value of /proc/sys/kernel/sysrq influences only the invocation via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always allowed (by a user with admin privileges).

1 Like

No, it says only root can trigger it via /proc/sysrq-trigger. Any user can trigger it with the actual SysRq key on the keyboard.

1 Like

Could any compromised non-root user generate the keyboard event for SysRq and thereby use SysRq?

1 Like

Yes, it shouldn’t be too hard to emulate the SysRq key the same way something like an on-screen keyboard works.

1 Like

Could you test please? We need to know this for sure.

If any non-root user can use SysRq via emulated keyboard event, then this changes security considerations.

Maybe a real keyboard (perhaps PS/2 only) can generate an event (hardware interrupt) that cannot be generated by a non-root user?

2 Likes
[Imprint] [Privacy Policy] [Cookie Policy] [Terms of Use] [E-Sign Consent] [DMCA] [Investors] [Priority Support] [Professional Support]