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-rw-r--r--src/shared/bus-polkit.c575
1 files changed, 575 insertions, 0 deletions
diff --git a/src/shared/bus-polkit.c b/src/shared/bus-polkit.c
new file mode 100644
index 0000000..904b897
--- /dev/null
+++ b/src/shared/bus-polkit.c
@@ -0,0 +1,575 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "bus-internal.h"
+#include "bus-message.h"
+#include "bus-polkit.h"
+#include "bus-util.h"
+#include "strv.h"
+#include "user-util.h"
+
+static int check_good_user(sd_bus_message *m, uid_t good_user) {
+ _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
+ uid_t sender_uid;
+ int r;
+
+ assert(m);
+
+ if (good_user == UID_INVALID)
+ return 0;
+
+ r = sd_bus_query_sender_creds(m, SD_BUS_CREDS_EUID, &creds);
+ if (r < 0)
+ return r;
+
+ /* Don't trust augmented credentials for authorization */
+ assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_EUID) == 0, -EPERM);
+
+ r = sd_bus_creds_get_euid(creds, &sender_uid);
+ if (r < 0)
+ return r;
+
+ return sender_uid == good_user;
+}
+
+#if ENABLE_POLKIT
+static int bus_message_append_strv_key_value(sd_bus_message *m, const char **l) {
+ int r;
+
+ assert(m);
+
+ r = sd_bus_message_open_container(m, 'a', "{ss}");
+ if (r < 0)
+ return r;
+
+ STRV_FOREACH_PAIR(k, v, l) {
+ r = sd_bus_message_append(m, "{ss}", *k, *v);
+ if (r < 0)
+ return r;
+ }
+
+ r = sd_bus_message_close_container(m);
+ if (r < 0)
+ return r;
+
+ return r;
+}
+
+static int bus_message_new_polkit_auth_call(
+ sd_bus_message *m,
+ const char *action,
+ const char **details,
+ bool interactive,
+ sd_bus_message **ret) {
+
+ _cleanup_(sd_bus_message_unrefp) sd_bus_message *c = NULL;
+ const char *sender;
+ int r;
+
+ assert(m);
+ assert(action);
+ assert(ret);
+
+ sender = sd_bus_message_get_sender(m);
+ if (!sender)
+ return -EBADMSG;
+
+ r = sd_bus_message_new_method_call(
+ ASSERT_PTR(m->bus),
+ &c,
+ "org.freedesktop.PolicyKit1",
+ "/org/freedesktop/PolicyKit1/Authority",
+ "org.freedesktop.PolicyKit1.Authority",
+ "CheckAuthorization");
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_append(c, "(sa{sv})s", "system-bus-name", 1, "name", "s", sender, action);
+ if (r < 0)
+ return r;
+
+ r = bus_message_append_strv_key_value(c, details);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_append(c, "us", interactive, NULL);
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(c);
+ return 0;
+}
+#endif
+
+int bus_test_polkit(
+ sd_bus_message *call,
+ int capability,
+ const char *action,
+ const char **details,
+ uid_t good_user,
+ bool *_challenge,
+ sd_bus_error *ret_error) {
+
+ int r;
+
+ assert(call);
+ assert(action);
+
+ /* Tests non-interactively! */
+
+ r = check_good_user(call, good_user);
+ if (r != 0)
+ return r;
+
+ r = sd_bus_query_sender_privilege(call, capability);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ return 1;
+
+#if ENABLE_POLKIT
+ _cleanup_(sd_bus_message_unrefp) sd_bus_message *request = NULL, *reply = NULL;
+ int authorized = false, challenge = false;
+
+ r = bus_message_new_polkit_auth_call(call, action, details, /* interactive = */ false, &request);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_call(call->bus, request, 0, ret_error, &reply);
+ if (r < 0) {
+ /* Treat no PK available as access denied */
+ if (bus_error_is_unknown_service(ret_error)) {
+ sd_bus_error_free(ret_error);
+ return -EACCES;
+ }
+
+ return r;
+ }
+
+ r = sd_bus_message_enter_container(reply, 'r', "bba{ss}");
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_read(reply, "bb", &authorized, &challenge);
+ if (r < 0)
+ return r;
+
+ if (authorized)
+ return 1;
+
+ if (_challenge) {
+ *_challenge = challenge;
+ return 0;
+ }
+#endif
+
+ return -EACCES;
+}
+
+#if ENABLE_POLKIT
+
+typedef struct AsyncPolkitQueryAction {
+ char *action;
+ char **details;
+
+ LIST_FIELDS(struct AsyncPolkitQueryAction, authorized);
+} AsyncPolkitQueryAction;
+
+static AsyncPolkitQueryAction *async_polkit_query_action_free(AsyncPolkitQueryAction *a) {
+ if (!a)
+ return NULL;
+
+ free(a->action);
+ strv_free(a->details);
+
+ return mfree(a);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(AsyncPolkitQueryAction*, async_polkit_query_action_free);
+
+typedef struct AsyncPolkitQuery {
+ unsigned n_ref;
+
+ AsyncPolkitQueryAction *action;
+
+ sd_bus_message *request;
+ sd_bus_slot *slot;
+
+ Hashmap *registry;
+ sd_event_source *defer_event_source;
+
+ LIST_HEAD(AsyncPolkitQueryAction, authorized_actions);
+ AsyncPolkitQueryAction *denied_action;
+ AsyncPolkitQueryAction *error_action;
+ sd_bus_error error;
+} AsyncPolkitQuery;
+
+static AsyncPolkitQuery *async_polkit_query_free(AsyncPolkitQuery *q) {
+ if (!q)
+ return NULL;
+
+ sd_bus_slot_unref(q->slot);
+
+ if (q->registry && q->request)
+ hashmap_remove(q->registry, q->request);
+
+ sd_bus_message_unref(q->request);
+
+ async_polkit_query_action_free(q->action);
+
+ sd_event_source_disable_unref(q->defer_event_source);
+
+ LIST_CLEAR(authorized, q->authorized_actions, async_polkit_query_action_free);
+
+ async_polkit_query_action_free(q->denied_action);
+ async_polkit_query_action_free(q->error_action);
+
+ sd_bus_error_free(&q->error);
+
+ return mfree(q);
+}
+
+DEFINE_PRIVATE_TRIVIAL_REF_UNREF_FUNC(AsyncPolkitQuery, async_polkit_query, async_polkit_query_free);
+DEFINE_TRIVIAL_CLEANUP_FUNC(AsyncPolkitQuery*, async_polkit_query_unref);
+
+static int async_polkit_defer(sd_event_source *s, void *userdata) {
+ AsyncPolkitQuery *q = ASSERT_PTR(userdata);
+
+ assert(s);
+
+ /* This is called as idle event source after we processed the async polkit reply, hopefully after the
+ * method call we re-enqueued has been properly processed. */
+
+ async_polkit_query_unref(q);
+ return 0;
+}
+
+static int async_polkit_read_reply(sd_bus_message *reply, AsyncPolkitQuery *q) {
+ _cleanup_(async_polkit_query_action_freep) AsyncPolkitQueryAction *a = NULL;
+ int authorized, challenge, r;
+
+ assert(reply);
+ assert(q);
+
+ /* Processing of a PolicyKit checks is canceled on the first auth. error. */
+ assert(!q->denied_action);
+ assert(!q->error_action);
+ assert(!sd_bus_error_is_set(&q->error));
+
+ assert(q->action);
+ a = TAKE_PTR(q->action);
+
+ if (sd_bus_message_is_method_error(reply, NULL)) {
+ const sd_bus_error *e;
+
+ e = sd_bus_message_get_error(reply);
+
+ if (bus_error_is_unknown_service(e))
+ /* Treat no PK available as access denied */
+ q->denied_action = TAKE_PTR(a);
+ else {
+ /* Save error from polkit reply, so it can be returned when the same authorization
+ * is attempted for second time */
+ q->error_action = TAKE_PTR(a);
+ r = sd_bus_error_copy(&q->error, e);
+ if (r == -ENOMEM)
+ return r;
+ }
+
+ return 0;
+ }
+
+ r = sd_bus_message_enter_container(reply, 'r', "bba{ss}");
+ if (r >= 0)
+ r = sd_bus_message_read(reply, "bb", &authorized, &challenge);
+ if (r < 0)
+ return r;
+
+ if (authorized)
+ LIST_PREPEND(authorized, q->authorized_actions, TAKE_PTR(a));
+ else if (challenge) {
+ q->error_action = TAKE_PTR(a);
+ sd_bus_error_set_const(&q->error, SD_BUS_ERROR_INTERACTIVE_AUTHORIZATION_REQUIRED, "Interactive authentication required.");
+ } else
+ q->denied_action = TAKE_PTR(a);
+
+ return 0;
+}
+
+static int async_polkit_process_reply(sd_bus_message *reply, AsyncPolkitQuery *q) {
+ int r;
+
+ assert(reply);
+ assert(q);
+
+ assert(q->slot);
+ q->slot = sd_bus_slot_unref(q->slot);
+
+ r = async_polkit_read_reply(reply, q);
+ if (r < 0)
+ return r;
+
+ /* Now, let's dispatch the original message a second time be re-enqueing. This will then traverse the
+ * whole message processing again, and thus re-validating and re-retrieving the "userdata" field
+ * again.
+ *
+ * We install an idle event loop event to clean-up the PolicyKit request data when we are idle again,
+ * i.e. after the second time the message is processed is complete. */
+
+ if (!q->defer_event_source) {
+ r = sd_event_add_defer(
+ sd_bus_get_event(sd_bus_message_get_bus(reply)),
+ &q->defer_event_source,
+ async_polkit_defer,
+ q);
+ if (r < 0)
+ return r;
+
+ r = sd_event_source_set_priority(q->defer_event_source, SD_EVENT_PRIORITY_IDLE);
+ if (r < 0)
+ return r;
+ }
+
+ r = sd_event_source_set_enabled(q->defer_event_source, SD_EVENT_ONESHOT);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_rewind(q->request, true);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_enqueue_for_read(sd_bus_message_get_bus(q->request), q->request);
+ if (r < 0)
+ return r;
+
+ return 1;
+}
+
+static int async_polkit_callback(sd_bus_message *reply, void *userdata, sd_bus_error *error) {
+ AsyncPolkitQuery *q = ASSERT_PTR(userdata);
+ int r;
+
+ assert(reply);
+
+ r = async_polkit_process_reply(reply, q);
+ if (r < 0) {
+ log_debug_errno(r, "Processing asynchronous PolicyKit reply failed, ignoring: %m");
+ (void) sd_bus_reply_method_errno(q->request, r, NULL);
+ async_polkit_query_unref(q);
+ }
+ return r;
+}
+
+static int async_polkit_query_check_action(
+ AsyncPolkitQuery *q,
+ const char *action,
+ const char **details,
+ sd_bus_error *ret_error) {
+
+ assert(q);
+ assert(action);
+ assert(ret_error);
+
+ LIST_FOREACH(authorized, a, q->authorized_actions)
+ if (streq(a->action, action) && strv_equal(a->details, (char**) details))
+ return 1;
+
+ if (q->error_action && streq(q->error_action->action, action))
+ return sd_bus_error_copy(ret_error, &q->error);
+
+ if (q->denied_action && streq(q->denied_action->action, action))
+ return -EACCES;
+
+ return 0;
+}
+
+#endif
+
+/* bus_verify_polkit_async() handles verification of D-Bus calls with polkit. Because the polkit API
+ * is asynchronous, the whole thing is a bit complex and requires some support in the code that uses
+ * it. It relies on sd-bus's support for interrupting the processing of a message.
+ *
+ * Requirements:
+ *
+ * * bus_verify_polkit_async() must be called before any changes to internal state.
+ * * If bus_verify_polkit_async() has made a new polkit query (signaled by return value 0),
+ * processing of the message should be interrupted. This is done by returning 1--which sd-bus
+ * handles specially--and is usually accompanied by a comment. (The message will be queued for
+ * processing again later when a reply from polkit is received.)
+ * * The code needs to keep a hashmap, here called registry, in which bus_verify_polkit_async()
+ * stores active queries. This hashmap's lifetime must be larger than the method handler's;
+ * e.g., it can be a member of some "manager" object or a global variable.
+ *
+ * Return value:
+ *
+ * * 0 - a new polkit call has been made, which means the processing of the message should be
+ * interrupted;
+ * * 1 - the action has been allowed;
+ * * -EACCES - the action has been denied;
+ * * < 0 - an unspecified error.
+ *
+ * A step-by-step description of how it works:
+ *
+ * 1. A D-Bus method handler calls bus_verify_polkit_async(), passing it the D-Bus message being
+ * processed and the polkit action to verify.
+ * 2. bus_verify_polkit_async() checks the registry for an existing query object associated with the
+ * message. Let's assume this is the first call, so it finds nothing.
+ * 3. A new AsyncPolkitQuery object is created and an async. D-Bus call to polkit is made. The
+ * function then returns 0. The method handler returns 1 to tell sd-bus that the processing of
+ * the message has been interrupted.
+ * 4. (Later) A reply from polkit is received and async_polkit_callback() is called.
+ * 5. async_polkit_callback() reads the reply and stores its result in the passed query.
+ * 6. async_polkit_callback() enqueues the original message again.
+ * 7. (Later) The same D-Bus method handler is called for the same message. It calls
+ * bus_verify_polkit_async() again.
+ * 8. bus_verify_polkit_async() checks the registry for an existing query object associated with the
+ * message. It finds one and returns the result for the action.
+ * 9. The method handler continues processing of the message. If there's another action that needs
+ * to be verified:
+ * 10. bus_verify_polkit_async() is called again for the new action. The registry already contains a
+ * query for the message, but the new action hasn't been seen yet, hence steps 4-8 are repeated.
+ * 11. (In the method handler again.) bus_verify_polkit_async() returns query results for both
+ * actions and the processing continues as in step 9.
+ *
+ * Memory handling:
+ *
+ * async_polkit_callback() registers a deferred call of async_polkit_defer() for the query, which
+ * causes the query to be removed from the registry and freed. Deferred events are run with idle
+ * priority, so this will happen after processing of the D-Bus message, when the query is no longer
+ * needed.
+ *
+ * Schematically:
+ *
+ * (m - D-Bus message, a - polkit action, q - polkit query)
+ *
+ * -> foo_method(m)
+ * -> bus_verify_polkit_async(m, a)
+ * -> async_polkit_query_ref(q)
+ * -> bus_call_method_async(q)
+ * <- bus_verify_polkit_async(m, a) = 0
+ * <- foo_method(m) = 1
+ * ...
+ * -> async_polkit_callback(q)
+ * -> sd_event_add_defer(async_polkit_defer, q)
+ * -> sd_bus_enqueue_for_read(m)
+ * <- async_polkit_callback(q)
+ * ...
+ * -> foo_method(m)
+ * -> bus_verify_polkit_async(m, a)
+ * <- bus_verify_polkit_async(m, a) = 1/-EACCES/error
+ * ...
+ * // possibly another call to bus_verify_polkit_async with action a2
+ * <- foo_method(m)
+ * ...
+ * -> async_polkit_defer(q)
+ * -> async_polkit_query_unref(q)
+ * <- async_polkit_defer(q)
+ */
+
+int bus_verify_polkit_async(
+ sd_bus_message *call,
+ int capability,
+ const char *action,
+ const char **details,
+ bool interactive,
+ uid_t good_user,
+ Hashmap **registry,
+ sd_bus_error *ret_error) {
+
+ int r;
+
+ assert(call);
+ assert(action);
+ assert(registry);
+ assert(ret_error);
+
+ r = check_good_user(call, good_user);
+ if (r != 0)
+ return r;
+
+#if ENABLE_POLKIT
+ _cleanup_(async_polkit_query_unrefp) AsyncPolkitQuery *q = NULL;
+
+ q = async_polkit_query_ref(hashmap_get(*registry, call));
+ /* This is a repeated invocation of this function, hence let's check if we've already got
+ * a response from polkit for this action */
+ if (q) {
+ r = async_polkit_query_check_action(q, action, details, ret_error);
+ if (r != 0)
+ return r;
+ }
+#endif
+
+ r = sd_bus_query_sender_privilege(call, capability);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ return 1;
+
+#if ENABLE_POLKIT
+ _cleanup_(sd_bus_message_unrefp) sd_bus_message *pk = NULL;
+
+ int c = sd_bus_message_get_allow_interactive_authorization(call);
+ if (c < 0)
+ return c;
+ if (c > 0)
+ interactive = true;
+
+ r = hashmap_ensure_allocated(registry, NULL);
+ if (r < 0)
+ return r;
+
+ r = bus_message_new_polkit_auth_call(call, action, details, interactive, &pk);
+ if (r < 0)
+ return r;
+
+ if (!q) {
+ q = new(AsyncPolkitQuery, 1);
+ if (!q)
+ return -ENOMEM;
+
+ *q = (AsyncPolkitQuery) {
+ .n_ref = 1,
+ .request = sd_bus_message_ref(call),
+ };
+ }
+
+ assert(!q->action);
+ q->action = new(AsyncPolkitQueryAction, 1);
+ if (!q->action)
+ return -ENOMEM;
+
+ *q->action = (AsyncPolkitQueryAction) {
+ .action = strdup(action),
+ .details = strv_copy((char**) details),
+ };
+ if (!q->action->action || !q->action->details)
+ return -ENOMEM;
+
+ if (!q->registry) {
+ r = hashmap_put(*registry, call, q);
+ if (r < 0)
+ return r;
+
+ q->registry = *registry;
+ }
+
+ r = sd_bus_call_async(call->bus, &q->slot, pk, async_polkit_callback, q, 0);
+ if (r < 0)
+ return r;
+
+ TAKE_PTR(q);
+
+ return 0;
+#endif
+
+ return -EACCES;
+}
+
+Hashmap *bus_verify_polkit_async_registry_free(Hashmap *registry) {
+#if ENABLE_POLKIT
+ return hashmap_free_with_destructor(registry, async_polkit_query_unref);
+#else
+ assert(hashmap_isempty(registry));
+ return hashmap_free(registry);
+#endif
+}
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