| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
To reach (at least) a conceptually equivalent security level as
implemented by --enable-sandbox in slirp4netns, we need to create a
new mount namespace and pivot_root() into a new (empty) mountpoint, so
that passt and pasta can't access any filesystem resource after
initialisation.
While at it, also detach IPC, PID (only for passt, to prevent
vulnerabilities based on the knowledge of a target PID), and UTS
namespaces.
With this approach, if we apply the seccomp filters right after the
configuration step, the number of allowed syscalls grows further. To
prevent this, defer the application of seccomp policies after the
initialisation phase, before the main loop, that's where we expect bad
things to happen, potentially. This way, we get back to 22 allowed
syscalls for passt and 34 for pasta, on x86_64.
While at it, move #syscalls notes to specific code paths wherever it
conceptually makes sense.
We have to open all the file handles we'll ever need before
sandboxing:
- the packet capture file can only be opened once, drop instance
numbers from the default path and use the (pre-sandbox) PID instead
- /proc/net/tcp{,v6} and /proc/net/udp{,v6}, for automatic detection
of bound ports in pasta mode, are now opened only once, before
sandboxing, and their handles are stored in the execution context
- the UNIX domain socket for passt is also bound only once, before
sandboxing: to reject clients after the first one, instead of
closing the listening socket, keep it open, accept and immediately
discard new connection if we already have a valid one
Clarify the (unchanged) behaviour for --netns-only in the man page.
To actually make passt and pasta processes run in a separate PID
namespace, we need to unshare(CLONE_NEWPID) before forking to
background (if configured to do so). Introduce a small daemon()
implementation, __daemon(), that additionally saves the PID file
before forking. While running in foreground, the process itself can't
move to a new PID namespace (a process can't change the notion of its
own PID): mention that in the man page.
For some reason, fork() in a detached PID namespace causes SIGTERM
and SIGQUIT to be ignored, even if the handler is still reported as
SIG_DFL: add a signal handler that just exits.
We can now drop most of the pasta_child_handler() implementation,
that took care of terminating all processes running in the same
namespace, if pasta started a shell: the shell itself is now the
init process in that namespace, and all children will terminate
once the init process exits.
Issuing 'echo $$' in a detached PID namespace won't return the
actual namespace PID as seen from the init namespace: adapt
demo and test setup scripts to reflect that.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
|
|
|
Warning: draft quality, not really tested, --enable-sandbox not
supported yet.
Example:
$ unshare -rUn
# echo $$
3130879
$ ./slirp4netns.sh -m 65520 -c 3130879 tap0
sent tapfd=5 for tap0
received tapfd=5
Starting slirp
* MTU: 65520
* Network: 10.0.2.0
* Netmask: 255.255.255.0
* Gateway: 10.0.2.2
* DNS: 10.0.2.3
* Recommended IP: 10.0.2.100
WARNING: 127.0.0.1:* on the host is accessible as 10.0.2.2 (set --disable-host-loopback to prohibit connecting to 127.0.0.1:*)
# ip li sh
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
33: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 65520 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
link/ether 5e:9d:a0:c5:cf:67 brd ff:ff:ff:ff:ff:ff
# ip ad sh
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
33: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 65520 qdisc pfifo_fast state UNKNOWN group default qlen 1000
link/ether 5e:9d:a0:c5:cf:67 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.0/24 scope global tap0
valid_lft forever preferred_lft forever
inet6 fe80::5c9d:a0ff:fec5:cf67/64 scope link
valid_lft forever preferred_lft forever
# ip ro sh
default via 10.0.2.2 dev tap0
10.0.2.0/24 dev tap0 proto kernel scope link src 10.0.2.0
root@epycfail:~# ip -6 ro sh
fe80::/64 dev tap0 proto kernel metric 256 pref medium
# iperf3 -c 10.0.2.2 -l1M
Connecting to host 10.0.2.2, port 5201
[ 5] local 10.0.2.0 port 43014 connected to 10.0.2.2 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 1.38 GBytes 11.8 Gbits/sec 0 9.96 MBytes
[ 5] 1.00-2.00 sec 1.59 GBytes 13.6 Gbits/sec 0 13.3 MBytes
[ 5] 2.00-3.00 sec 1.63 GBytes 14.0 Gbits/sec 0 13.3 MBytes
[ 5] 3.00-4.00 sec 1.78 GBytes 15.3 Gbits/sec 0 13.3 MBytes
[ 5] 4.00-5.00 sec 1.80 GBytes 15.5 Gbits/sec 0 15.8 MBytes
[ 5] 5.00-6.00 sec 1.69 GBytes 14.5 Gbits/sec 0 15.8 MBytes
[ 5] 6.00-7.00 sec 1.65 GBytes 14.2 Gbits/sec 0 15.8 MBytes
[ 5] 7.00-8.00 sec 1.68 GBytes 14.4 Gbits/sec 0 15.8 MBytes
[ 5] 8.00-9.00 sec 1.60 GBytes 13.7 Gbits/sec 0 15.8 MBytes
[ 5] 9.00-10.00 sec 1.66 GBytes 14.3 Gbits/sec 0 15.8 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 16.5 GBytes 14.1 Gbits/sec 0 sender
[ 5] 0.00-10.01 sec 16.4 GBytes 14.1 Gbits/sec receiver
iperf Done.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
|
