docs: replace insecure /tmp examples in qsd docs

World-writeable directories have security issues. Avoid showing them in
the documentation since someone might accidentally use them in
situations where they are insecure.

There tend to be 3 security problems:
1. Denial of service. An adversary may be able to create the file
   beforehand, consume all space/inodes, etc to sabotage us.
2. Impersonation. An adversary may be able to create a listen socket and
   accept incoming connections that were meant for us.
3. Unauthenticated client access. An adversary may be able to connect to
   us if we did not set the uid/gid and permissions correctly.

These can be prevented or mitigated with private /tmp, carefully setting
the umask, etc but that requires special action and does not apply to
all situations. Just avoid using /tmp in examples.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210301172728.135331-3-stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst
index 5714794775a2a78fd6c5cd9c22787f9842f75a2a..fe3042d609778f923fb9bc4281e79fd9c7c58d45 100644 (file)
--- a/docs/tools/qemu-storage-daemon.rst
+++ b/docs/tools/qemu-storage-daemon.rst
@@ -69,7 +69,7 @@ Standard options:
   a description of character device properties. A common character device
   definition configures a UNIX domain socket::
 
-  --chardev socket,id=char1,path=/tmp/qmp.sock,server=on,wait=off
+  --chardev socket,id=char1,path=/var/run/qsd-qmp.sock,server=on,wait=off
 
 .. option:: --export [type=]nbd,id=<id>,node-name=<node-name>[,name=<export-name>][,writable=on|off][,bitmap=<name>]
   --export [type=]vhost-user-blk,id=<id>,node-name=<node-name>,addr.type=unix,addr.path=<socket-path>[,writable=on|off][,logical-block-size=<block-size>][,num-queues=<num-queues>]
@@ -108,9 +108,10 @@ Standard options:
   below). TLS encryption can be configured using ``--object`` tls-creds-* and
   authz-* secrets (see below).
 
-  To configure an NBD server on UNIX domain socket path ``/tmp/nbd.sock``::
+  To configure an NBD server on UNIX domain socket path
+  ``/var/run/qsd-nbd.sock``::
 
-  --nbd-server addr.type=unix,addr.path=/tmp/nbd.sock
+  --nbd-server addr.type=unix,addr.path=/var/run/qsd-nbd.sock
 
 .. option:: --object help
   --object <type>,help