librlimit

librlimit: rlimit sandbox for any process

DESCRIPTION

librlimit sets up rlimit process restrictions for dynamically linked executables. The restrictions are enforced after the executable has loaded any shared libraries.

The shell ulimit or daemontools softlimit apply to the process lifetime from fork() to exec(). The process will typically need to perform operations like opening a file descriptor to linked libraries:

• fork a subprocess
• load shared libraries
• nsswitch: read configuration files

For example:

• ulimit

$ (ulimit -n 0; ls)
ls: error while loading shared libraries: libselinux.so.1: cannot open shared object file: Error 24

• softlimit

$ softlimit -o 0 ls
ls: error while loading shared libraries: libselinux.so.1: cannot open shared object file: Error 24

• librlimit

LD_PRELOAD=librlimit.so RLIMIT_NOFILE=0 ls
ls: cannot open directory '.': Too many open files

EXAMPLES

$ LD_PRELOAD=librlimit.so RLIMIT_FSIZE=0 yes > test
File size limit exceeded (core dumped)

$ LD_PRELOAD=librlimit.so RLIMIT_NPROC=0 sh -c "sleep 60 & sleep 60 & sleep 60 & sleep 60"
sh: 0: Cannot fork

$ LD_PRELOAD=librlimit.so RLIMIT_NOFILE=0 cat -n
abc
     1  abc

ENVIRONMENT VARIABLES

LIBRLIMIT_OPT

set options for the library behaviour (default: 1)

• 0: no options enabled
• 1: exit with status 111 if setting rlimit fails
• 2: enable debug
• 3: exit on failure and debug enabled

Supported resources are platform dependent. See setrlimit(3).

RLIMIT_AS

maximum size of process' virtual memory (address space)

RLIMIT_CORE

maximum size of a core file

RLIMIT_CPU

limit in seconds on CPU time

RLIMIT_DATA

maximum size of the process' data segment

RLIMIT_FSIZE

maximum file size in bytes

RLIMIT_LOCKS

limits the number of flock(2) locks and fcntl(2) leases

RLIMIT_MEMLOCK

maximum number of bytes available to be locked into memory

RLIMIT_MSGQUEUE

maximum of bytes allocated for POSIX message queues

RLIMIT_NICE

limits priority of process

RLIMIT_NOFILE

maximum number of file descriptors

RLIMIT_NPROC

maximum number of processes

RLIMIT_RSS

maximum number of bytes for a process resident set size

RLIMIT_RTPRIO

maximum real-time priority of process

RLIMIT_RTTIME

limit in microseconds for real-time scheduled CPU time

RLIMIT_SIGPENDING

maximum number of queued signals

RLIMIT_STACK

maximum size of process stack

RLIMIT_SBSIZE

maximum size of all socket buffers (FreeBSD)

RLIMIT_VMEM

virtual process size (incl. mmap) (equivalent to RLIMIT_AS) (FreeBSD)

RLIMIT_NPTS

pseudo-terminals (FreeBSD)

RLIMIT_SWAP

swap used (FreeBSD)

RLIMIT_KQUEUES

kqueues allocated (FreeBSD)

RLIMIT_UMTXP

process-shared umtx (FreeBSD)