bus: add new sd_bus_creds object to encapsulate process credentials

This way we can unify handling of credentials that are attached to
messages, or can be queried for bus name owners or connection peers.

This also adds the ability to extend incomplete credential information
with data from /proc,

Also, provide a convenience call that will automatically determine the
most appropriate credential object for an incoming message, by using the
the attached information if possible, the sending name information if
available and otherwise the peer's credentials.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/libsystemd-bus/bus-convenience.c b/src/libsystemd-bus/bus-convenience.c
index e765ddb21d..e57b26bf6b 100644
--- a/src/libsystemd-bus/bus-convenience.c
+++ b/src/libsystemd-bus/bus-convenience.c
@@ -410,3 +410,33 @@ _public_ int sd_bus_set_property(
 
         return sd_bus_call(bus, m, 0, error, NULL);
 }
+
+_public_ int sd_bus_query_sender_creds(sd_bus_message *call, uint64_t mask, sd_bus_creds **creds) {
+        sd_bus_creds *c;
+
+        assert_return(call, -EINVAL);
+        assert_return(call->sealed, -EPERM);
+        assert_return(call->bus && BUS_IS_OPEN(call->bus->state), -ENOTCONN);
+        assert_return(!bus_pid_changed(call->bus), -ECHILD);
+
+        c = sd_bus_message_get_creds(call);
+
+        /* All data we need? */
+        if (c && (mask & ~c->mask) == 0) {
+                *creds = sd_bus_creds_ref(c);
+                return 0;
+        }
+
+        /* No data passed? Or not enough data passed to retrieve the missing bits? */
+        if (!c || !(c->mask & SD_BUS_CREDS_PID)) {
+                /* We couldn't read anything from the call, let's try
+                 * to get it from the sender or peer */
+
+                if (call->sender)
+                        return sd_bus_get_owner_creds(call->bus, call->sender, mask, creds);
+                else
+                        return sd_bus_get_peer_creds(call->bus, mask, creds);
+        }
+
+        return sd_bus_creds_extend(c, mask, creds);
+}