3 files changed, 101 insertions, 0 deletions

diff --git a/src/libsystemd-bus/libsystemd-bus.sym b/src/libsystemd-bus/libsystemd-bus.sym
index 8fa2cdec6d..a8df513009 100644
--- a/src/libsystemd-bus/libsystemd-bus.sym
+++ b/src/libsystemd-bus/libsystemd-bus.sym
@@ -187,6 +187,10 @@ global:
         sd_bus_error_is_set;
         sd_bus_error_has_name;
 
+        /* Escaping */
+        sd_bus_label_escape;
+        sd_bus_label_unescape;
+
         /* sd-memfd functions */
         sd_memfd_new;
         sd_memfd_make;
diff --git a/src/libsystemd-bus/sd-bus.c b/src/libsystemd-bus/sd-bus.c
index 72d04d28f1..0ae52563e7 100644
--- a/src/libsystemd-bus/sd-bus.c
+++ b/src/libsystemd-bus/sd-bus.c
@@ -2712,3 +2712,75 @@ _public_ int sd_bus_get_tid(sd_bus *b, pid_t *tid) {
 
         return -ENXIO;
 }
+
+_public_ char *sd_bus_label_escape(const char *s) {
+        char *r, *t;
+        const char *f;
+
+        assert_return(s, NULL);
+
+        /* Escapes all chars that D-Bus' object path cannot deal
+         * with. Can be reversed with bus_path_unescape(). We special
+         * case the empty string. */
+
+        if (*s == 0)
+                return strdup("_");
+
+        r = new(char, strlen(s)*3 + 1);
+        if (!r)
+                return NULL;
+
+        for (f = s, t = r; *f; f++) {
+
+                /* Escape everything that is not a-zA-Z0-9. We also
+                 * escape 0-9 if it's the first character */
+
+                if (!(*f >= 'A' && *f <= 'Z') &&
+                    !(*f >= 'a' && *f <= 'z') &&
+                    !(f > s && *f >= '0' && *f <= '9')) {
+                        *(t++) = '_';
+                        *(t++) = hexchar(*f >> 4);
+                        *(t++) = hexchar(*f);
+                } else
+                        *(t++) = *f;
+        }
+
+        *t = 0;
+
+        return r;
+}
+
+_public_ char *sd_bus_label_unescape(const char *f) {
+        char *r, *t;
+
+        assert_return(f, NULL);
+
+        /* Special case for the empty string */
+        if (streq(f, "_"))
+                return strdup("");
+
+        r = new(char, strlen(f) + 1);
+        if (!r)
+                return NULL;
+
+        for (t = r; *f; f++) {
+
+                if (*f == '_') {
+                        int a, b;
+
+                        if ((a = unhexchar(f[1])) < 0 ||
+                            (b = unhexchar(f[2])) < 0) {
+                                /* Invalid escape code, let's take it literal then */
+                                *(t++) = '_';
+                        } else {
+                                *(t++) = (char) ((a << 4) | b);
+                                f += 2;
+                        }
+                } else
+                        *(t++) = *f;
+        }
+
+        *t = 0;
+
+        return r;
+}
diff --git a/src/libsystemd-bus/test-bus-marshal.c b/src/libsystemd-bus/test-bus-marshal.c
index b7606d7708..98737b6811 100644
--- a/src/libsystemd-bus/test-bus-marshal.c
+++ b/src/libsystemd-bus/test-bus-marshal.c
@@ -39,6 +39,29 @@
 #include "bus-util.h"
 #include "bus-dump.h"
 
+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(streq(t, b));
+
+        assert_se(x = sd_bus_label_unescape(t));
+        assert_se(streq(a, x));
+
+        assert_se(y = sd_bus_label_unescape(b));
+        assert_se(streq(a, y));
+}
+
+static void test_bus_label_escape(void) {
+        test_bus_label_escape_one("foo123bar", "foo123bar");
+        test_bus_label_escape_one("foo.bar", "foo_2ebar");
+        test_bus_label_escape_one("foo_2ebar", "foo_5f2ebar");
+        test_bus_label_escape_one("", "_");
+        test_bus_label_escape_one("_", "_5f");
+        test_bus_label_escape_one("1", "_31");
+        test_bus_label_escape_one(":1", "_3a1");
+}
+
 int main(int argc, char *argv[]) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL, *copy = NULL;
         int r, boolean;
@@ -294,5 +317,7 @@ int main(int argc, char *argv[]) {
         assert_se(streq(c, "ccc"));
         assert_se(streq(d, "3"));
 
+        test_bus_label_escape();
+
         return 0;
 }