On Mon, Oct 05, 2020 at 08:21:50AM -0500, Eric Blake wrote:
On 10/3/20 1:50 PM, Richard W.M. Jones wrote:
> New nbdkit_peer_pid, nbdkit_peer_uid and nbdkit_peer_gid calls can be
> used on Linux (only) to read the peer PID, UID and GID from clients
> connected over a Unix domain socket. This can be used in the
> preconnect phase to add additional filtering.
>
> One use for this is to add an extra layer of authentication for local
> connections. A subsequent commit will enhance the now misnamed
> nbdkit-ip-filter to allow filtering on these extra fields.
>
> It appears as if it would be possible to implement this for FreeBSD
> too (see comment in code).
> ---
> docs/nbdkit-plugin.pod | 47 +++++++++++++++--
> include/nbdkit-common.h | 3 ++
> server/nbdkit.syms | 3 ++
> server/public.c | 108 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 156 insertions(+), 5 deletions(-)
>
> +=head2 C<nbdkit_peer_pid>
> +
> +(nbdkit E<ge> 1.24)
> +
> + int nbdkit_peer_pid (void);
> +
> +Return the peer process ID. This is only available when the client
> +connected over a Unix domain socket, and only works for Linux.
> +
> +On success this returns the peer process ID. On error,
> +C<nbdkit_error> is called and this call returns C<-1>.
Is int always going to be sufficient? Or are there platforms with
64-bit pid_t? Mingw is an interesting beast; I've seen conflicting
stories on whether 64-bit windows has 32- or 64-bit pids (the spawn APIs
manage 64-bit handles, but other windows APIs return 32-bit int), so
64-bit pid_t on mingw does seem to be a real concern.
> +
> +=head2 C<nbdkit_peer_uid>
> +
> +(nbdkit E<ge> 1.24)
> +
> + int nbdkit_peer_uid (void);
> +
> +Return the peer user ID. This is only available when the client
> +connected over a Unix domain socket, and only works for Linux.
> +
> +On success this returns the user ID. On error, C<nbdkit_error> is
> +called and this call returns C<-1>.
> +
> +=head2 C<nbdkit_peer_gid>
> +
> +(nbdkit E<ge> 1.24)
> +
> + int nbdkit_peer_gid (void);
int for these two is probably fine.
> +
> +Return the peer group ID. This is only available when the client
> +connected over a Unix domain socket, and only works for Linux.
> +
> +On success this returns the user ID. On error, C<nbdkit_error> is
> +called and this call returns C<-1>.
> +
> =head1 DEBUGGING
>
> +static int
> +get_peercred (int s, int *pid, int *uid, int *gid)
> +{
> + struct ucred ucred;
> + socklen_t n = sizeof ucred;
> +
> + if (getsockopt (s, SOL_SOCKET, SO_PEERCRED, &ucred, &n) == -1) {
> + nbdkit_error ("getsockopt: SO_PEERCRED: %m");
> + return -1;
> + }
> +
> + if (pid && ucred.pid >= 1) {
> + if (ucred.pid <= INT_MAX)
> + *pid = ucred.pid;
> + else
> + nbdkit_error ("pid out of range: cannot be mapped to int");
> + }
well, at least you are acknowledging that int might not always map to pid_t.
Otherwise, looks fine to me.
I wonder if I should just change all of them to int64_t?
Rich.
--
Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
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