bus: replace sd_bus_label_{escape,unescape}() by new sd_bus_path_{encode,decode}()

The new calls work similarly, but enforce a that a common, fixed bus
path prefix is used.

This follows discussions with Simon McVittie on IRC that it should be a
good idea to make sure that people don't use the escaping applied here
too wildly as anything other than the last label of a bus path.

5 files changed, 71 insertions, 15 deletions

diff --git a/src/libsystemd/sd-bus/bus-creds.c b/src/libsystemd/sd-bus/bus-creds.c
index 2d56f3c461..3da77cf1d7 100644
--- a/src/libsystemd/sd-bus/bus-creds.c
+++ b/src/libsystemd/sd-bus/bus-creds.c
@@ -30,6 +30,7 @@
 #include "time-util.h"
 #include "strv.h"
 #include "bus-creds.h"
+#include "bus-label.h"
 
 enum {
         CAP_OFFSET_INHERITABLE = 0,
@@ -474,7 +475,7 @@ _public_ int sd_bus_creds_get_connection_name(sd_bus_creds *c, const char **ret)
         assert(c->conn_name);
 
         if (!c->unescaped_conn_name) {
-                c->unescaped_conn_name = sd_bus_label_unescape(c->conn_name);
+                c->unescaped_conn_name = bus_label_unescape(c->conn_name);
                 if (!c->unescaped_conn_name)
                         return -ENOMEM;
         }
diff --git a/src/libsystemd/sd-bus/bus-kernel.c b/src/libsystemd/sd-bus/bus-kernel.c
index 2a1b0b424a..8a2ca02996 100644
--- a/src/libsystemd/sd-bus/bus-kernel.c
+++ b/src/libsystemd/sd-bus/bus-kernel.c
@@ -36,6 +36,7 @@
 #include "bus-kernel.h"
 #include "bus-bloom.h"
 #include "bus-util.h"
+#include "bus-label.h"
 #include "cgroup-util.h"
 
 #define UNIQUE_NAME_MAX (3+DECIMAL_STR_MAX(uint64_t))
@@ -658,7 +659,7 @@ int bus_kernel_take_fd(sd_bus *b) {
         b->use_memfd = 1;
 
         if (b->connection_name) {
-                g = sd_bus_label_escape(b->connection_name);
+                g = bus_label_escape(b->connection_name);
                 if (!g)
                         return -ENOMEM;
 
@@ -678,7 +679,7 @@ int bus_kernel_take_fd(sd_bus *b) {
                 } else {
                         _cleanup_free_ char *e = NULL;
 
-                        e = sd_bus_label_escape(pr);
+                        e = bus_label_escape(pr);
                         if (!e)
                                 return -ENOMEM;
 
@@ -691,7 +692,7 @@ int bus_kernel_take_fd(sd_bus *b) {
                         name = g;
                 }
 
-                b->connection_name = sd_bus_label_unescape(name);
+                b->connection_name = bus_label_unescape(name);
                 if (!b->connection_name)
                         return -ENOMEM;
         }
@@ -1119,7 +1120,7 @@ int bus_kernel_pop_memfd(sd_bus *bus, void **address, size_t *mapped, size_t *al
 
                 assert(bus->connection_name);
 
-                g = sd_bus_label_escape(bus->connection_name);
+                g = bus_label_escape(bus->connection_name);
                 if (!g)
                         return -ENOMEM;
 
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index fbf1a5919f..ffa3369feb 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -3063,12 +3063,46 @@ _public_ int sd_bus_get_tid(sd_bus *b, pid_t *tid) {
         return -ENXIO;
 }
 
-_public_ char *sd_bus_label_escape(const char *s) {
-        return bus_label_escape(s);
+_public_ int sd_bus_path_encode(const char *prefix, const char *external_id, char **ret_path) {
+        _cleanup_free_ char *e = NULL;
+        char *ret;
+
+        assert_return(object_path_is_valid(prefix), -EINVAL);
+        assert_return(external_id, -EINVAL);
+        assert_return(ret_path, -EINVAL);
+
+        e = bus_label_escape(external_id);
+        if (!e)
+                return -ENOMEM;
+
+        ret = strjoin(prefix, "/", e, NULL);
+        if (!ret)
+                return -ENOMEM;
+
+        *ret_path = ret;
+        return 0;
 }
 
-_public_ char *sd_bus_label_unescape(const char *f) {
-        return bus_label_unescape(f);
+_public_ int sd_bus_path_decode(const char *path, const char *prefix, char **external_id) {
+        const char *e;
+        char *ret;
+
+        assert_return(object_path_is_valid(path), -EINVAL);
+        assert_return(object_path_is_valid(prefix), -EINVAL);
+        assert_return(external_id, -EINVAL);
+
+        e = object_path_startswith(path, prefix);
+        if (!e) {
+                *external_id = NULL;
+                return 0;
+        }
+
+        ret = bus_label_unescape(e);
+        if (!ret)
+                return -ENOMEM;
+
+        *external_id = ret;
+        return 1;
 }
 
 _public_ int sd_bus_get_peer_creds(sd_bus *bus, uint64_t mask, sd_bus_creds **ret) {
diff --git a/src/libsystemd/sd-bus/sd-memfd.c b/src/libsystemd/sd-bus/sd-memfd.c
index 7c71476eee..8f9e236392 100644
--- a/src/libsystemd/sd-bus/sd-memfd.c
+++ b/src/libsystemd/sd-bus/sd-memfd.c
@@ -27,6 +27,7 @@
 
 #include "util.h"
 #include "kdbus.h"
+#include "bus-label.h"
 
 #include "sd-memfd.h"
 #include "sd-bus.h"
@@ -56,7 +57,7 @@ _public_ int sd_memfd_new(sd_memfd **m, const char *name) {
                  * set here, let's do the usual bus escaping to deal
                  * with that. */
 
-                g = sd_bus_label_escape(name);
+                g = bus_label_escape(name);
                 if (!g)
                         return -ENOMEM;
 
@@ -76,7 +77,7 @@ _public_ int sd_memfd_new(sd_memfd **m, const char *name) {
                 else {
                         _cleanup_free_ char *e = NULL;
 
-                        e = sd_bus_label_escape(pr);
+                        e = bus_label_escape(pr);
                         if (!e)
                                 return -ENOMEM;
 
@@ -311,7 +312,7 @@ _public_ int sd_memfd_get_name(sd_memfd *m, char **name) {
         if (!n)
                 return -ENOMEM;
 
-        e = sd_bus_label_unescape(n);
+        e = bus_label_unescape(n);
         if (!e)
                 return -ENOMEM;
 
diff --git a/src/libsystemd/sd-bus/test-bus-marshal.c b/src/libsystemd/sd-bus/test-bus-marshal.c
index d438a231a6..2321873da5 100644
--- a/src/libsystemd/sd-bus/test-bus-marshal.c
+++ b/src/libsystemd/sd-bus/test-bus-marshal.c
@@ -38,17 +38,35 @@
 #include "bus-message.h"
 #include "bus-util.h"
 #include "bus-dump.h"
+#include "bus-label.h"
+
+static void test_bus_path_encode(void) {
+        _cleanup_free_ char *a = NULL, *b = NULL, *c = NULL, *d = NULL, *e = NULL, *f = NULL;
+
+        assert_se(sd_bus_path_encode("/foo/bar", "waldo", &a) >= 0 && streq(a, "/foo/bar/waldo"));
+        assert_se(sd_bus_path_decode(a, "/waldo", &b) == 0 && b == NULL);
+        assert_se(sd_bus_path_decode(a, "/foo/bar", &b) > 0 && streq(b, "waldo"));
+
+        assert_se(sd_bus_path_encode("xxxx", "waldo", &c) < 0);
+        assert_se(sd_bus_path_encode("/foo/", "waldo", &c) < 0);
+
+        assert_se(sd_bus_path_encode("/foo/bar", "", &c) >= 0 && streq(c, "/foo/bar/_"));
+        assert_se(sd_bus_path_decode(c, "/foo/bar", &d) > 0 && streq(d, ""));
+
+        assert_se(sd_bus_path_encode("/foo/bar", "foo.bar", &e) >= 0 && streq(e, "/foo/bar/foo_2ebar"));
+        assert_se(sd_bus_path_decode(e, "/foo/bar", &f) > 0 && streq(f, "foo.bar"));
+}
 
 static void test_bus_label_escape_one(const char *a, const char *b) {
         _cleanup_free_ char *t = NULL, *x = NULL, *y = NULL;
 
-        assert_se(t = sd_bus_label_escape(a));
+        assert_se(t = bus_label_escape(a));
         assert_se(streq(t, b));
 
-        assert_se(x = sd_bus_label_unescape(t));
+        assert_se(x = bus_label_unescape(t));
         assert_se(streq(a, x));
 
-        assert_se(y = sd_bus_label_unescape(b));
+        assert_se(y = bus_label_unescape(b));
         assert_se(streq(a, y));
 }
 
@@ -322,6 +340,7 @@ int main(int argc, char *argv[]) {
         assert_se(streq(d, "3"));
 
         test_bus_label_escape();
+        test_bus_path_encode();
 
         return 0;
 }