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path: root/isolation.h
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* passt, util: Close any open file that the parent might have leakedStefano Brivio2024-08-081-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a parent accidentally or due to implementation reasons leaks any open file, we don't want to have access to them, except for the file passed via --fd, if any. This is the case for Podman when Podman's parent leaks files into Podman: it's not practical for Podman to close unrelated files before starting pasta, as reported by Paul. Use close_range(2) to close all open files except for standard streams and the one from --fd. Given that parts of conf() depend on other files to be already opened, such as the epoll file descriptor, we can't easily defer this to a more convenient point, where --fd was already parsed. Introduce a minimal, duplicate version of --fd parsing to keep this simple. As we need to check that the passed --fd option doesn't exceed INT_MAX, because we'll parse it with strtol() but file descriptor indices are signed ints (regardless of the arguments close_range() take), extend the existing check in the actual --fd parsing in conf(), also rejecting file descriptors numbers that match standard streams, while at it. Suggested-by: Paul Holzinger <pholzing@redhat.com> Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Paul Holzinger <pholzing@redhat.com>
* cppcheck: Make many pointers constDavid Gibson2023-10-041-1/+1
| | | | | | | | | Newer versions of cppcheck (as of 2.12.0, at least) added a warning for pointers which could be declared to point at const data, but aren't. Based on that, make many pointers throughout the codebase const. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* passt: Relicense to GPL 2.0, or any later versionStefano Brivio2023-04-061-1/+1
| | | | | | | | | | | | | | | | | | | In practical terms, passt doesn't benefit from the additional protection offered by the AGPL over the GPL, because it's not suitable to be executed over a computer network. Further, restricting the distribution under the version 3 of the GPL wouldn't provide any practical advantage either, as long as the passt codebase is concerned, and might cause unnecessary compatibility dilemmas. Change licensing terms to the GNU General Public License Version 2, or any later version, with written permission from all current and past contributors, namely: myself, David Gibson, Laine Stump, Andrea Bolognani, Paul Holzinger, Richard W.M. Jones, Chris Kuhn, Florian Weimer, Giuseppe Scrivano, Stefan Hajnoczi, and Vasiliy Ulyanov. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* isolation: Replace drop_caps() with a version that actually does somethingDavid Gibson2022-10-151-1/+2
| | | | | | | | | | | | | | | | | | | | The current implementation of drop_caps() doesn't really work because it attempts to drop capabilities from the bounding set. That's not the set that really matters, it's about limiting the abilities of things we might later exec() rather than our own capabilities. It also requires CAP_SETPCAP which we won't usually have. Replace it with a new version which uses setcap(2) to drop capabilities from the effective and permitted sets. For now we leave the inheritable set as is, since we don't want to preclude the user from passing inheritable capabilities to the command spawed by pasta. Correctly dropping caps reveals that we were relying on some capabilities we'd supposedly dropped. Re-divide the dropping of capabilities between isolate_initial(), isolate_user() and isolate_prefork() to make this work. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* isolation: Clarify various self-isolation stepsDavid Gibson2022-10-151-3/+3
| | | | | | | | | | We have a number of steps of self-isolation scattered across our code. Improve function names and add comments to make it clearer what the self isolation model is, what the steps do, and why they happen at the points they happen. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* Handle userns isolation and dropping root at the same timeDavid Gibson2022-09-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | passt/pasta can interact with user namespaces in a number of ways: 1) With --netns-only we'll remain in our original user namespace 2) With --userns or a PID option to pasta we'll join either the given user namespace or that of the PID 3) When pasta spawns a shell or command we'll start a new user namespace for the command and then join it 4) With passt we'll create a new user namespace when we sandbox() ourself However (3) and (4) turn out to have essentially the same effect. In both cases we create one new user namespace. The spawned command starts there, and passt/pasta itself will live there from sandbox() onwards. Because of this, we can simplify user namespace handling by moving the userns handling earlier, to the same point we drop root in the original namespace. Extend the drop_user() function to isolate_user() which does both. After switching UID and GID in the original userns, isolate_user() will either join or create the userns we require. When we spawn a command with pasta_start_ns()/pasta_setup_ns() we no longer need to create a userns, because we're already made one. sandbox() likewise no longer needs to create (or join) an userns because we're already in the one we need. We no longer need c->pasta_userns_fd, since the fd is only used locally in isolate_user(). Likewise we can replace c->netns_only with a local in conf(), since it's not used outside there. Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
* Move self-isolation code into a separate fileDavid Gibson2022-09-131-0/+15
passt/pasta contains a number of routines designed to isolate passt from the rest of the system for security. These are spread through util.c and passt.c. Move them together into a new isolation.c file. Signed-off-by: David Gibson <david@gibson.dropbear.id.au>