noop

Have some program that keeps writing files all over your system? Stop it from opening them with noop!

Note: noop won't work on anything other than Linux.

Usage

noop blocks or modifies calls to open made by the passed program.

USAGE:
  noop [-lh] [FILE[:rw] | FILE=REPLACE]... -- PROGRAM [ARG]...

FLAGS:
  -l Logs open calls and resulting action to stderr
  -h Show this message and exit

ARGS:
  FILE          Block PROGRAM from opening FILE
      [:rw]     If :r or :w is specified only that opening mode is blocked
  FILE=REPLACE  Replace open calls to FILE with REPLACE
  PROGRAM       PROGRAM to run and intercept on
  ARGS          ARGS to pass to the PROGRAM

Example

$ echo foo > bar
$ cat bar
foo
$ # No open
$ noop bar -- cat bar
cat: bar: Operation not permitted
$ # No read
$ noop bar:r -- cat bar
cat: bar: Operation not permitted
$ # No write
$ noop bar:w -- cat bar
foo
$ echo | noop bar:w -- tee bar
tee: bar: Operation not permitted
$ # Redirect
$ noop wrong=bar -- cat wrong
foo

Building

Run cargo build to compile.

The project relies on a recently landed PR of the nix crate so for now the dependency pulls from GitHub rather than crates.io.

Alternatives

There is some overhead of noop, mainly in handling every open call. noop uses seccomp with to avoid having to handle every syscall, however.

See cargo bench for more empirical measure of performance.

Some alternative ways to block the opening of a file:

• Run the program as an unprivileged user.
• If the program is writing files in your home directory, try exporting $HOME as something like /tmp before running.
• Provide a custom open using LD_PRELOAD. Note that this frequently fails in the case that the function used is statically linked / nonstandard.

Bugs

The command line parsing doesn't work very well on files with = or : in them.

Applications that fork aren't handled.

TODO

• Add recursive blocking
• Add folder creation blocking
• Add better command line argument handling