BACKPORT: net: core: enable SO_BINDTODEVICE for non-root users
Currently, SO_BINDTODEVICE requires CAP_NET_RAW. This change allows a
non-root user to bind a socket to an interface if it is not already
bound. This is useful to allow an application to bind itself to a
specific VRF for outgoing or incoming connections. Currently, an
application wanting to manage connections through several VRF need to
be privileged.
Previously, IP_UNICAST_IF and IPV6_UNICAST_IF were added for
Wine (76e21053b5bf3 and c4062dfc425e9) specifically for use by
non-root processes. However, they are restricted to sendmsg() and not
usable with TCP. Allowing SO_BINDTODEVICE would allow TCP clients to
get the same privilege. As for TCP servers, outside the VRF use case,
SO_BINDTODEVICE would only further restrict connections a server could
accept.
When an application is restricted to a VRF (with `ip vrf exec`), the
socket is bound to an interface at creation and therefore, a
non-privileged call to SO_BINDTODEVICE to escape the VRF fails.
When an application bound a socket to SO_BINDTODEVICE and transmit it
to a non-privileged process through a Unix socket, a tentative to
change the bound device also fails.
Before:
>>> import socket
>>> s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> s.setsockopt(socket.SOL_SOCKET, socket.SO_BINDTODEVICE, b"dummy0")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
PermissionError: [Errno 1] Operation not permitted
After:
>>> import socket
>>> s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> s.setsockopt(socket.SOL_SOCKET, socket.SO_BINDTODEVICE, b"dummy0")
>>> s.setsockopt(socket.SOL_SOCKET, socket.SO_BINDTODEVICE, b"dummy0")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
PermissionError: [Errno 1] Operation not permitted
Bug: 323792489
Signed-off-by: Vincent Bernat <vincent@bernat.ch>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit c427bfec18f2190b8f4718785ee8ed2db4f84ee6)
Change-Id: Ie3f4c536b78da12dd961dc681c6dfb0cdf1a06b7
Signed-off-by: Peiyong Wang <wangpeiyong@xiaomi.corp-partner.google.com>diff --git a/net/core/sock.c b/net/core/sock.c
index d7ae953..0a5e574 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -578,7 +578,7 @@
/* Sorry... */
ret = -EPERM;
- if (!ns_capable(net->user_ns, CAP_NET_RAW))
+ if (sk->sk_bound_dev_if && !ns_capable(net->user_ns, CAP_NET_RAW))
goto out;
ret = -EINVAL;
