sd-bus: when augmenting creds, remember which ones were augmented

[elogind.git] / src / libelogind / sd-bus / bus-convenience.c

diff --git a/src/libelogind/sd-bus/bus-convenience.c b/src/libelogind/sd-bus/bus-convenience.c
index a6317e97857bd7a19eda2e690cf089b8b1d1f4e4..28bc8d28181b1df349ca6659eb216d659b8d534f 100644 (file)
--- a/src/libelogind/sd-bus/bus-convenience.c
+++ b/src/libelogind/sd-bus/bus-convenience.c
@@ -462,11 +462,22 @@ _public_ int sd_bus_query_sender_creds(sd_bus_message *call, uint64_t mask, sd_b
         /* 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 */
+                 * to get it from the sender or peer. */
 
                 if (call->sender)
+                        /* There's a sender, but the creds are
+                         * missing. This means we are talking via
+                         * dbus1, or are getting a message that was
+                         * sent to us via kdbus, but was converted
+                         * from a dbus1 message by the bus-proxy and
+                         * thus also lacks the creds. */
                         return sd_bus_get_name_creds(call->bus, call->sender, mask, creds);
                 else
+                        /* There's no sender, hence we are on a dbus1
+                         * direct connection. For direct connections
+                         * the credentials of the AF_UNIX peer matter,
+                         * which may be queried via
+                         * sd_bus_get_owner_creds(). */
                         return sd_bus_get_owner_creds(call->bus, mask, creds);
         }
 
@@ -488,10 +499,18 @@ _public_ int sd_bus_query_sender_privilege(sd_bus_message *call, int capability)
                 return -ENOTCONN;
 
         if (capability >= 0) {
+
                 r = sd_bus_query_sender_creds(call, SD_BUS_CREDS_UID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EFFECTIVE_CAPS, &creds);
                 if (r < 0)
                         return r;
 
+                /* We cannot use augmented caps for authorization,
+                 * since then data is acquired raceful from
+                 * /proc. This can never actually happen, but let's
+                 * better be safe than sorry, and do an extra check
+                 * here. */
+                assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_EFFECTIVE_CAPS) == 0, -EPERM);
+
                 /* Note that not even on kdbus we might have the caps
                  * field, due to faked identities, or namespace
                  * translation issues. */
@@ -512,6 +531,13 @@ _public_ int sd_bus_query_sender_privilege(sd_bus_message *call, int capability)
         if (our_uid != 0 || !know_caps || capability < 0) {
                 uid_t sender_uid;
 
+                /* We cannot use augmented uid/euid for authorization,
+                 * since then data is acquired raceful from
+                 * /proc. This can never actually happen, but let's
+                 * better be safe than sorry, and do an extra check
+                 * here. */
+                assert_return((sd_bus_creds_get_augmented_mask(creds) & (SD_BUS_CREDS_UID|SD_BUS_CREDS_EUID)) == 0, -EPERM);
+
                 /* Try to use the EUID, if we have it. */
                 r = sd_bus_creds_get_euid(creds, &sender_uid);
                 if (r < 0)