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On 03/02/2018 05:08 AM, Rich Freeman wrote: |
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> On the other hand, if netfilter were implemented in userspace such as |
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> via a microkernel, then if it contained a bug the remote attacker would |
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> be able to MITM all network traffic on the machine, but that would |
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> be the extent of the access they have. |
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I don't know that it would be the extent of the access the attacker |
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would have. It might also be a beachhead that could be used as a |
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starting point for future attacks. |
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> The process running the netfilter code doesn't need anything other than |
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> a pipe back to the kernel to receive packets and send packets back, |
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> so it can run with minimal privs otherwise. |
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I think that more than a simple pipe (as in unix socket) is needed. |
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Currently, any program that uses IP is expecting a socket to behave like |
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it currently behaves. I don't think a simple pipe can provide that. |
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I can see a way now, using existing technology, to have an isolated |
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firewall that runs in user space. Remove all IP processing from eth0 in |
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the main kernel. Connect eth0 to a User Mode Linux kernel which does |
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the filtering (in user space) and routes the traffic back over another |
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connection to the host kernel, i.e. uml0. |
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+-----------------------------+ |
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| Host | |
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| +--------------+ | |
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| | UML Firewall | | |
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-----+ eth0 eth1 +---uml0 | |
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| +--------------+ | |
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+-----------------------------+ |
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Processes running on the host can use the uml0 interface just like they |
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formerly used the eth0 interface. |
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All the firewalling / filtering / routing happens in user space |
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(possibly a container) and independent of the host kernel. |
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> a lot of the boot-time mounting logic and devfs/etc logic has gone away |
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> in favor of initramfs and udev. |
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Please provide examples of this "…boot-time mounting logic and devfs/etc |
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logic…" that used to be in kernel. |
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I'll argue that devfs is now in kernel when it used to be files on a |
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file system or dynamically created by a user space process. As far as I |
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know, mounting (more than root as RO) has always been driven from user |
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space via init scripts. |
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Sure, there's a LOT of changes going on in that space, particularly |
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around (anti)systemd. But IMHO this has been user space for as long as |
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I have known. |
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Please provide examples where I'm wrong. I'd like to learn. |
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> And of course if this is done it is done correctly, and not as some kind |
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> of userspace hack on top of an OS to add features that it lacks. |
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??? |
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-- |
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Grant. . . . |
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unix || die |
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