RLIMIT_NOFILE pseudo-sandbox on FreeBSD. In some configurations,
libc will attempt to open additional file descriptors for crypto
offload and crash if they cannot be opened.
[sandbox-null.c sandbox-rlimit.c sandbox-seccomp-filter.c]
[sandbox-systrace.c ssh-sandbox.h sshd.c] Support preauth sandboxing
using the Capsicum API introduced in FreeBSD 10. Patch by Dag-Erling
Smorgrav, updated by Loganaden Velvindron @ AfriNIC; ok dtucker@
[sshd.c ssh-sandbox.h sandbox.h sandbox-rlimit.c sandbox-systrace.c]
[sandbox-null.c]
rename sandbox.h => ssh-sandbox.h to make things easier for portable
[servconf.c servconf.h sshd.c sshd_config.5 sandbox-rlimit.c]
[sandbox-systrace.c sandbox.h configure.ac Makefile.in]
introduce sandboxing of the pre-auth privsep child using systrace(4).
This introduces a new "UsePrivilegeSeparation=sandbox" option for
sshd_config that applies mandatory restrictions on the syscalls the
privsep child can perform. This prevents a compromised privsep child
from being used to attack other hosts (by opening sockets and proxying)
or probing local kernel attack surface.
The sandbox is implemented using systrace(4) in unsupervised "fast-path"
mode, where a list of permitted syscalls is supplied. Any syscall not
on the list results in SIGKILL being sent to the privsep child. Note
that this requires a kernel with the new SYSTR_POLICY_KILL option.
UsePrivilegeSeparation=sandbox will become the default in the future
so please start testing it now.
feedback dtucker@; ok markus@
Damien Miller
Darren Tucker