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Native library calls
====================
Goals
-----
Behavioural goals:
* Route system function via arena
* Allocate memory via arena, so it gets freed.
* Catch signals and turn them into "SLUL exceptions"
Safety goals:
* Disallow memory operations outside of the arena and sub-arenas?
I.e. sandbox the arena.
* (Perhaps even outside of parameters?)
Implementation
--------------
It could be implemented as a "throw away" process running with seccomp.
Perhaps add a new arena type: "secure arenas", that work like "threaded
arenas", except that there is also isolation via seccomp and a separated
address space etc.
Creating a secure arena could perhaps work as follows (pseudo-code):
For Linux:
pipe()
clone(...) /* create an "empty" process, perhaps with exec("/usr/lib/.../slul_empty") */
...map any wanted native libraries into memory...
...set up fake/wrapper libc, that forwards calls to the pipe...
capset({ _LINUX_CAPABILITY_VERSION_3, 0 }, { 0, 0, 0 })
/*prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0) - should not be needed */
prctl(PR_SET_NO_NEW_PRIVS, 1)
setrlimit(RLIMIT_NOFILE, { 0, 0 })
setrlimit(RLIMIT_NPROC, { 0, 0 })
prctl(PR_SET_SECCOMP, SECCOMP_MODE_STRICT)
...call initialization functions of native libraries...
For BSD:
pipe()
clone(...) /* create an "empty" process */
...map any wanted native libraries into memory...
...set up fake/wrapper libc, that forwards calls to the pipe...
setrlimit(RLIMIT_NOFILE, { 0, 0 })
setrlimit(RLIMIT_NPROC, { 0, 0 })
unveil(NULL, NULL)
pledge("")
...call initialization functions of native libraries...
Tricky parts:
- ELF mapping needs to be implemented (at least to load the system's dynamic
loader)
- There can be a lot of libc calls
- libc calls can be system specific
- Things like exec, clone, threading, etc. is tricky
- Some libc calls could be really hard to emulate
- Supporting non-POSIX systems could be tricky.
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