From 63ab06c4d281046b4a2424b6accd407470c91eb5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Fri, 5 Feb 2021 15:22:42 +0100
Subject: [PATCH] sd-bus: extend sd_bus_message_read_strv() to paths and
 signatures

It's rather convenient to be able to read all three types with this function.
Strictly speaking this change is not fully compatible, in case someone was
relying on sd_bus_message_read_strv() returning an error for anything except
"as", but I hope nobody was doing that.
---
 man/sd_bus_message_read_strv.xml    | 19 ++++++++++++++-----
 src/libsystemd/sd-bus/bus-message.c | 15 ++++++++++++---
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/man/sd_bus_message_read_strv.xml b/man/sd_bus_message_read_strv.xml
index a90ae840983..50580d86bcc 100644
--- a/man/sd_bus_message_read_strv.xml
+++ b/man/sd_bus_message_read_strv.xml
@@ -36,11 +36,13 @@
   <refsect1>
     <title>Description</title>
 
-    <para><function>sd_bus_message_read_strv()</function> gives access to an array of strings in message
-    <parameter>m</parameter>. The "read pointer" in the message must be right before an array of strings. On
-    success, a pointer to the <constant>NULL</constant>-terminated array of strings is returned in the output
-    parameter <parameter>l</parameter>. Note that ownership of this array is transferred to the caller.
-    Hence, the caller is responsible for freeing this array and its contents.</para>
+    <para><function>sd_bus_message_read_strv()</function> gives access to an array of string-like items in
+    message <parameter>m</parameter>. The "read pointer" in the message must be right before an array of
+    strings (D-Bus type <literal>as</literal>), object paths (D-Bus type <literal>ao</literal>), or
+    signatures (D-Bus type <literal>ag</literal>). On success, a pointer to a
+    <constant>NULL</constant>-terminated array of strings is returned in the output parameter
+    <parameter>l</parameter>. Note that ownership of this array is transferred to the caller. Hence, the
+    caller is responsible for freeing this array and its contents.</para>
   </refsect1>
 
   <refsect1>
@@ -73,6 +75,13 @@
 
           <listitem><para>The message cannot be parsed.</para></listitem>
         </varlistentry>
+
+        <varlistentry>
+          <term><constant>-ENXIO</constant></term>
+
+          <listitem><para>The message "read pointer" is not right before an array of the appropriate type.
+          </para></listitem>
+        </varlistentry>
       </variablelist>
     </refsect2>
   </refsect1>
diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index f358a8699e8..894d681260f 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -5587,17 +5587,26 @@ int bus_message_get_blob(sd_bus_message *m, void **buffer, size_t *sz) {
 }
 
 int bus_message_read_strv_extend(sd_bus_message *m, char ***l) {
-        const char *s;
+        char type;
+        const char *contents, *s;
         int r;
 
         assert(m);
         assert(l);
 
-        r = sd_bus_message_enter_container(m, 'a', "s");
+        r = sd_bus_message_peek_type(m, &type, &contents);
+        if (r < 0)
+                return r;
+
+        if (type != SD_BUS_TYPE_ARRAY || !STR_IN_SET(contents, "s", "o", "g"))
+                return -ENXIO;
+
+        r = sd_bus_message_enter_container(m, 'a', NULL);
         if (r <= 0)
                 return r;
 
-        while ((r = sd_bus_message_read_basic(m, 's', &s)) > 0) {
+        /* sd_bus_message_read_basic() does content validation for us. */
+        while ((r = sd_bus_message_read_basic(m, *contents, &s)) > 0) {
                 r = strv_extend(l, s);
                 if (r < 0)
                         return r;