IFP: Add utility functions to escape and unescape object paths

D-Bus spec says:
Each element must only contain the ASCII characters "[A-Z][a-z][0-9]_"

This patch adds two utility functions to escape raw input into format
suitable for DBus and conversely transform escaped paths back into raw
paths.

Reviewed-by: Stef Walter <stefw@redhat.com>
Reviewed-by: Pavel Březina <pbrezina@redhat.com>

2 files changed, 134 insertions, 1 deletions

diff --git a/src/responder/ifp/ifp_private.h b/src/responder/ifp/ifp_private.h
index e7fcaa4c3..75be038e4 100644
--- a/src/responder/ifp/ifp_private.h
+++ b/src/responder/ifp/ifp_private.h
@@ -69,9 +69,12 @@ errno_t ifp_req_create(struct sbus_request *dbus_req,
 int ifp_req_create_handle_failure(struct sbus_request *dbus_req, errno_t err);
 
 const char *ifp_path_strip_prefix(const char *path, const char *prefix);
+
+char *ifp_bus_path_unescape(TALLOC_CTX *mem_ctx, const char *path);
+char *ifp_bus_path_escape(TALLOC_CTX *mem_ctx, const char *path);
+
 errno_t ifp_add_ldb_el_to_dict(DBusMessageIter *iter_dict,
                                struct ldb_message_element *el);
-
 const char **ifp_parse_attr_list(TALLOC_CTX *mem_ctx, const char *conf_str);
 bool ifp_attr_allowed(const char *whitelist[], const char *attr);
 #endif /* _IFPSRV_PRIVATE_H_ */
diff --git a/src/responder/ifp/ifpsrv_util.c b/src/responder/ifp/ifpsrv_util.c
index 4ef0be6af..6fcd22479 100644
--- a/src/responder/ifp/ifpsrv_util.c
+++ b/src/responder/ifp/ifpsrv_util.c
@@ -106,6 +106,136 @@ const char *ifp_path_strip_prefix(const char *path, const char *prefix)
     return NULL;
 }
 
+/* The following path related functions are based on similar code in
+ * storaged, just tailored to use talloc instead of glib
+ */
+char *ifp_bus_path_escape(TALLOC_CTX *mem_ctx, const char *path)
+{
+    size_t n;
+    char *safe_path = NULL;
+    TALLOC_CTX *tmp_ctx = NULL;
+
+    /* The path must be valid */
+    if (path == NULL) {
+        return NULL;
+    }
+
+    tmp_ctx = talloc_new(NULL);
+    if (tmp_ctx == NULL) {
+        return NULL;
+    }
+
+    safe_path = talloc_strdup(tmp_ctx, "");
+    if (safe_path == NULL) {
+        goto done;
+    }
+
+    /* Special case for an empty string */
+    if (strcmp(path, "") == 0) {
+        /* the for loop would just fall through */
+        safe_path = talloc_asprintf_append_buffer(safe_path, "_");
+    }
+
+    for (n = 0; path[n]; n++) {
+        int c = path[n];
+        /* D-Bus spec says:
+         * *
+         * * Each element must only contain the ASCII characters
+         * "[A-Z][a-z][0-9]_"
+         * */
+        if ((c >= 'A' && c <= 'Z')
+                || (c >= 'a' && c <= 'z')
+                || (c >= '0' && c <= '9')) {
+            safe_path = talloc_asprintf_append_buffer(safe_path, "%c", c);
+            if (safe_path == NULL) {
+                goto done;
+            }
+        } else {
+            safe_path = talloc_asprintf_append_buffer(safe_path, "_%02x", c);
+            if (safe_path == NULL) {
+                goto done;
+            }
+        }
+    }
+
+    safe_path = talloc_steal(mem_ctx, safe_path);
+done:
+    talloc_free(tmp_ctx);
+    return safe_path;
+}
+
+static inline int unhexchar(char c)
+{
+    if (c >= '0' && c <= '9') {
+        return c - '0';
+    }
+
+    if (c >= 'a' && c <= 'f') {
+        return c - 'a' + 10;
+    }
+
+    if (c >= 'A' && c <= 'F') {
+        return c - 'A' + 10;
+    }
+
+    return -1;
+}
+
+char *ifp_bus_path_unescape(TALLOC_CTX *mem_ctx, const char *path)
+{
+    char *safe_path;
+    const char *p;
+    int a, b, c;
+    TALLOC_CTX *tmp_ctx = NULL;
+
+    tmp_ctx = talloc_new(NULL);
+    if (tmp_ctx == NULL) {
+        return NULL;
+    }
+
+    safe_path = talloc_strdup(tmp_ctx, "");
+    if (safe_path == NULL) {
+        goto done;
+    }
+
+    /* Special case for the empty string */
+    if (strcmp(path, "_") == 0) {
+        safe_path = talloc_steal(mem_ctx, safe_path);
+        goto done;
+    }
+
+    for (p = path; *p; p++) {
+        if (*p == '_') {
+            /* There must be at least two more chars after underscore */
+            if (p[1] == '\0' || p[2] == '\0') {
+                safe_path = NULL;
+                goto done;
+            }
+
+            if ((a = unhexchar(p[1])) < 0
+                    || (b = unhexchar(p[2])) < 0) {
+                /* Invalid escape code, let's take it literal then */
+                c = '_';
+            } else {
+                c = ((a << 4) | b);
+                p += 2;
+            }
+        } else  {
+            c = *p;
+        }
+
+        safe_path = talloc_asprintf_append_buffer(safe_path, "%c", c);
+        if (safe_path == NULL) {
+            goto done;
+        }
+    }
+
+    safe_path = talloc_steal(mem_ctx, safe_path);
+done:
+    talloc_free(tmp_ctx);
+    return safe_path;
+}
+
 errno_t ifp_add_ldb_el_to_dict(DBusMessageIter *iter_dict,
                                struct ldb_message_element *el)
 {