3 ms·

No, I suppose not, but then, is there really an advantage to doing so? I'm much more concerned with blocking write and execute access than I am about a potenti

No, I suppose not, but then, is there really an advantage to doing so? I'm much more concerned with blocking write and execute access than I am about a potential hacker being able to read the config files of the program they leveraged to get a shell. I think it's a good approach and part of defense in depth, but if we're comparing approaches I'll tale the former every time.

ori_b 2y ago
> No, I suppose not, but then, is there really an advantage to doing so? A massive one; not reading the config is just a consequence of dropping all file system access once you're done with the initial program setup. You can also set up listening sockets, and then stop the program from making any new network connections, even after a compromise. And so on, with most resources. There are a lot of resources that tend to be needed to set up a program. There tend to be very few needed once the program is running. How would you block all file system access after a program is finished reading its config files, the files they include, and the shared libraries and plugins scattered around the file system? How would you turn off all network access after the listening socket is established? With Pledge, it's trivial: load_config(); load_plugins(); open_sockets(); pledge(NULL, NULL); run(); Pledge makes everything you're talking about work trivially, the only thing that's needed is for the program to opt in to security with one line of code. You don't need to micromanage the permissions and what the program is doing to drop privileges from the outside, with all of the race conditions and fragility that implies.
- ruthmarx 2y ago
  > There are a lot of resources that tend to be needed to set up a program. There tend to be very few needed once the program is running. I think this is true for simple programs, and less true the more complex a program is. What about programs that due to their nature need to frequently make new network connections, or to periodically check config files? > How would you block all file system access after a program is finished reading its config files, the files they include, and the shared libraries and plugins scattered around the file system? How would you turn off all network access after the listening socket is established? This could be done with seccomp, although it would be more work than it is to use pledge (although a pledge 'port' also exists), it could also be done with things like SELinux. > Pledge makes everything you're talking about work trivially, I was talking about more complete sandboxing, and pledge doesn't allow for that. Pledge is substantially more limited in scope. > the only thing that's needed is for the program to opt in That's actually a pretty big issue. If all the software you want to use is in the ports tree I guess it's fine, but what about for untrusted or complex code? Say, running an instance of Oracle, or a torrent program that by it's nature constantly needs to make network connections and write/read different files? Pledge is little help in these cases, and especially ineffective as any attempt at sandboxing such applications.
  - ori_b 2y ago
    > I think this is true for simple programs, and less true the more complex a program is. Chrome and Firefox have both been successfully pledged and unveiled. What programs more complex than them are you considering?
    - ruthmarx 2y ago
      I gave examples at the end of my previous reply.
      - ori_b 2y ago
        > Say, running an instance of Oracle, or a torrent program that by it's nature constantly needs to make network connections and write/read different files? Yes, those seem relatively simple to pledge (source availability aside); there are a lot of permissions that they should be able to drop once they decide on, say, where the database lives or what files they're saving to. It gets even better if you're willing to privsep the torrent program, though that could take some refactoring. Note that you can trivially do a looser sandbox around unmodified processes using exec pledges and unveil, even for proprietary code. These kinds of sandboxes need to be permissive, though, since they're not aware of program phases. So they're not nearly as tight as a sandbox written by the developer with knowledge about expected program behavior.
        ruthmarx 2y ago
        > It gets even better if you're willing to privsep the torrent program, though that could take some refactoring. Now you're talking about modifying the code substantially which is out of scope of the thought experiment. Pledge can't really help with the torrent program since it needs to make new network connections and write and read arbitrary files constantly. Unless as you say, you substantially modify the code. If substantially modifying the code is off the table, can you give an example of how pledge can prevent an attacker leveraging an RCE in the torrent program? To what extent would they be restricted? You can't say, limit execution to only certain files/libraries or restrict the ability to delete or overwrite files, right? > Note that you can trivially do a looser sandbox around unmodified processes using exec pledges and unveil, even for proprietary code. These kinds of sandboxes need to be permissive, Yeah, I wouldn't consider that to be a sandbox. Imposing limitations on a program isn't by itself a sandbox, nor is every instance of doing so sandboxing.

ori_b 2y ago

> No, I suppose not, but then, is there really an advantage to doing so? A massive one; not reading the config is just a consequence of dropping all file system access once you're done with the initial program setup. You can also set up listening sockets, and then stop the program from making any new network connections, even after a compromise. And so on, with most resources. There are a lot of resources that tend to be needed to set up a program. There tend to be very few needed once the program is running. How would you block all file system access after a program is finished reading its config files, the files they include, and the shared libraries and plugins scattered around the file system? How would you turn off all network access after the listening socket is established? With Pledge, it's trivial: load_config(); load_plugins(); open_sockets(); pledge(NULL, NULL); run(); Pledge makes everything you're talking about work trivially, the only thing that's needed is for the program to opt in to security with one line of code. You don't need to micromanage the permissions and what the program is doing to drop privileges from the outside, with all of the race conditions and fragility that implies.

ruthmarx 2y ago
> There are a lot of resources that tend to be needed to set up a program. There tend to be very few needed once the program is running. I think this is true for simple programs, and less true the more complex a program is. What about programs that due to their nature need to frequently make new network connections, or to periodically check config files? > How would you block all file system access after a program is finished reading its config files, the files they include, and the shared libraries and plugins scattered around the file system? How would you turn off all network access after the listening socket is established? This could be done with seccomp, although it would be more work than it is to use pledge (although a pledge 'port' also exists), it could also be done with things like SELinux. > Pledge makes everything you're talking about work trivially, I was talking about more complete sandboxing, and pledge doesn't allow for that. Pledge is substantially more limited in scope. > the only thing that's needed is for the program to opt in That's actually a pretty big issue. If all the software you want to use is in the ports tree I guess it's fine, but what about for untrusted or complex code? Say, running an instance of Oracle, or a torrent program that by it's nature constantly needs to make network connections and write/read different files? Pledge is little help in these cases, and especially ineffective as any attempt at sandboxing such applications.
- ori_b 2y ago
  > I think this is true for simple programs, and less true the more complex a program is. Chrome and Firefox have both been successfully pledged and unveiled. What programs more complex than them are you considering?
  - ruthmarx 2y ago
    I gave examples at the end of my previous reply.
    - ori_b 2y ago
      > Say, running an instance of Oracle, or a torrent program that by it's nature constantly needs to make network connections and write/read different files? Yes, those seem relatively simple to pledge (source availability aside); there are a lot of permissions that they should be able to drop once they decide on, say, where the database lives or what files they're saving to. It gets even better if you're willing to privsep the torrent program, though that could take some refactoring. Note that you can trivially do a looser sandbox around unmodified processes using exec pledges and unveil, even for proprietary code. These kinds of sandboxes need to be permissive, though, since they're not aware of program phases. So they're not nearly as tight as a sandbox written by the developer with knowledge about expected program behavior.
      - ruthmarx 2y ago
        > It gets even better if you're willing to privsep the torrent program, though that could take some refactoring. Now you're talking about modifying the code substantially which is out of scope of the thought experiment. Pledge can't really help with the torrent program since it needs to make new network connections and write and read arbitrary files constantly. Unless as you say, you substantially modify the code. If substantially modifying the code is off the table, can you give an example of how pledge can prevent an attacker leveraging an RCE in the torrent program? To what extent would they be restricted? You can't say, limit execution to only certain files/libraries or restrict the ability to delete or overwrite files, right? > Note that you can trivially do a looser sandbox around unmodified processes using exec pledges and unveil, even for proprietary code. These kinds of sandboxes need to be permissive, Yeah, I wouldn't consider that to be a sandbox. Imposing limitations on a program isn't by itself a sandbox, nor is every instance of doing so sandboxing.