libmbim-glib,tlv: allow 0-length strings for MBIM_TLV_TYPE_WCHAR_STR

Document Microsoft MBIM Extensions for 5G (rev 1.17) considers the possibility
of having wchar strings tlvs with datalength == 0 in the information buffer
(e.g. AccessString field in MBIM_CONNECT_INFO_EX3 data structure).

Modify mbim_tlv_string_get for dealing with these situations, returning an
empty string.

2 files changed, 84 insertions, 0 deletions

diff --git a/src/libmbim-glib/mbim-tlv.c b/src/libmbim-glib/mbim-tlv.c
index 283abc2..e02d460 100644
--- a/src/libmbim-glib/mbim-tlv.c
+++ b/src/libmbim-glib/mbim-tlv.c
@@ -260,6 +260,9 @@ mbim_tlv_string_get (const MbimTlv  *self,
     /* Duplicate array unconditionally to avoid alignment issues as we don't
      * know if the 16bit array is aligned properly or not in the TLV */
     size = MBIM_TLV_GET_DATA_LENGTH (self);
+    /* If size == 0, an empty string is returned since 0-length strings are allowed */
+    if (!size)
+        return g_strdup ("");
     tmp = (gunichar2 *) g_memdup ((gconstpointer) MBIM_TLV_FIELD_DATA (self), size);
 
     /* For BE systems, convert from LE to BE */
diff --git a/src/libmbim-glib/test/test-message-parser.c b/src/libmbim-glib/test/test-message-parser.c
index 93a4d51..e13d94f 100644
--- a/src/libmbim-glib/test/test-message-parser.c
+++ b/src/libmbim-glib/test/test-message-parser.c
@@ -2612,6 +2612,86 @@ test_ms_basic_connect_v3_connect_0_unnamed_tlvs (void)
 }
 
 static void
+test_ms_basic_connect_v3_connect_0_unnamed_tlvs_empty_access_string (void)
+{
+    g_autoptr(GError)       error = NULL;
+    g_autoptr(MbimMessage)  response = NULL;
+    gboolean                result;
+    GList                  *unnamed_ies = NULL;
+    guint32                 session_id;
+    MbimActivationState     activation_state;
+    MbimVoiceCallState      voice_call_state;
+    MbimContextIpType       ip_type;
+    MbimAccessMediaType     media_type = MBIM_ACCESS_MEDIA_TYPE_UNKNOWN;
+    g_autofree gchar       *access_string = NULL;
+    const MbimUuid         *context_type;
+    guint32                 nw_error;
+
+    const guint8 buffer [] =  {
+        /* header */
+        0x03, 0x00, 0x00, 0x80, /* type */
+        0x60, 0x00, 0x00, 0x00, /* length */
+        0x04, 0x00, 0x00, 0x00, /* transaction id */
+        /* fragment header */
+        0x01, 0x00, 0x00, 0x00, /* total */
+        0x00, 0x00, 0x00, 0x00, /* current */
+        /* command_done_message */
+        0xA2, 0x89, 0xCC, 0x33, /* service id */
+        0xBC, 0xBB, 0x8B, 0x4F,
+        0xB6, 0xB0, 0x13, 0x3E,
+        0xC2, 0xAA, 0xE6, 0xDF,
+        0x0C, 0x00, 0x00, 0x00, /* command id */
+        0x00, 0x00, 0x00, 0x00, /* status code */
+        0x30, 0x00, 0x00, 0x00, /* buffer_length */
+        /* information buffer */
+        0x01, 0x00, 0x00, 0x00, /* session id */
+        0x01, 0x00, 0x00, 0x00, /* activation state */
+        0x00, 0x00, 0x00, 0x00, /* voice call state */
+        0x01, 0x00, 0x00, 0x00, /* ip type */
+        0x7E, 0x5E, 0x2A, 0x7E, /* context type */
+        0x4E, 0x6F, 0x72, 0x72,
+        0x73, 0x6B, 0x65, 0x6E,
+        0x7E, 0x5E, 0x2A, 0x7E,
+        0x00, 0x00, 0x00, 0x00, /* nw error */
+        0x01, 0x00, 0x00, 0x00, /* media type */
+        0x0A, 0x00, 0x00, 0x00, /* access string empty */
+        0x00, 0x00, 0x00, 0x00,
+        /* no unnamed TLVs */
+    };
+
+    response = mbim_message_new (buffer, sizeof (buffer));
+    g_assert (mbim_message_validate (response, &error));
+    g_assert_no_error (error);
+
+    test_message_printable (response, 3, 0);
+
+    result = (mbim_message_ms_basic_connect_v3_connect_response_parse (
+                  response,
+                  &session_id,
+                  &activation_state,
+                  &voice_call_state,
+                  &ip_type,
+                  &context_type,
+                  &nw_error,
+                  &media_type,
+                  &access_string,
+                  &unnamed_ies,
+                  &error));
+
+    g_assert_no_error (error);
+    g_assert (result);
+
+    g_assert_cmpuint (session_id, ==, 1);
+    g_assert_cmpuint (activation_state, ==, MBIM_ACTIVATION_STATE_ACTIVATED);
+    g_assert_cmpuint (voice_call_state, ==, MBIM_VOICE_CALL_STATE_NONE);
+    g_assert_cmpuint (ip_type, ==, MBIM_CONTEXT_IP_TYPE_IPV4);
+    g_assert_cmpuint (mbim_uuid_to_context_type (context_type), ==, MBIM_CONTEXT_TYPE_INTERNET);
+    g_assert_cmpuint (media_type, ==, MBIM_ACCESS_MEDIA_TYPE_3GPP);
+    g_assert_cmpstr  (access_string, ==, "");
+    g_assert_cmpuint (g_list_length (unnamed_ies), ==, 0);
+}
+
+static void
 test_ms_basic_connect_v3_connect_1_unnamed_tlv (void)
 {
     g_autoptr(GError)       error = NULL;
@@ -3346,6 +3426,7 @@ int main (int argc, char **argv)
     g_test_add_func (PREFIX "/basic-connect-extensions/registration-parameters/1-unnamed-tlv", test_ms_basic_connect_extensions_registration_parameters_1_unnamed_tlv);
     g_test_add_func (PREFIX "/basic-connect-extensions/registration-parameters/3-unnamed-tlvs", test_ms_basic_connect_extensions_registration_parameters_3_unnamed_tlvs);
     g_test_add_func (PREFIX "/basic-connect-v3/connect/0-unnamed-tlvs", test_ms_basic_connect_v3_connect_0_unnamed_tlvs);
+    g_test_add_func (PREFIX "/basic-connect-v3/connect/0-unnamed-tlvs-empty-access-string", test_ms_basic_connect_v3_connect_0_unnamed_tlvs_empty_access_string);
     g_test_add_func (PREFIX "/basic-connect-v3/connect/1-unnamed-tlv", test_ms_basic_connect_v3_connect_1_unnamed_tlv);
     g_test_add_func (PREFIX "/basic-connect-v3/connect/3-unnamed-tlvs", test_ms_basic_connect_v3_connect_3_unnamed_tlvs);
     g_test_add_func (PREFIX "/basic-connect-extensions/device-caps-v3", test_ms_basic_connect_extensions_device_caps_v3);