Wireshark-bugs: [Wireshark-bugs] [Bug 6346] New: Lua: TvbRange missing unicode string method
Date: Thu, 15 Sep 2011 09:56:41 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6346

           Summary: Lua: TvbRange missing unicode string method
           Product: Wireshark
           Version: 1.7.x (Experimental)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Enhancement
          Priority: Low
         Component: Extras
        AssignedTo: [email protected]
        ReportedBy: [email protected]


Created an attachment (id=7023)
 --> (https://bugs.wireshark.org/bugzilla/attachment.cgi?id=7023)
Sample capture

Build Information:
[email protected]:~$ ~/usr/bin/wireshark -v
wireshark 1.7.0 (SVN Rev 39010 from /trunk)

Copyright 1998-2011 Gerald Combs <[email protected]> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled (64-bit) with GTK+ 2.22.0, with Cairo 1.10.0, with Pango 1.28.2, with
GLib 2.26.1, with libpcap 1.1.1, with libz 1.2.3.4, without POSIX capabilities,
with threads support, without SMI, without c-ares, without ADNS, with Lua 5.1,
without Python, with GnuTLS 2.8.6, with Gcrypt 1.4.5, without Kerberos, with
GeoIP, without PortAudio, without AirPcap.

Running on Linux 2.6.35-30-virtual, with locale en_US.utf8, with libpcap
version
1.1.1, with libz 1.2.3.4, GnuTLS 2.8.6, Gcrypt 1.4.5.

Built using gcc 4.4.5.

--
Trying to read UTF-16 strings from a capture in a lua dissector is either
difficult or we must convert the bytes manually to UTF-8 that Wireshark will
understand.

In this example dissector with the attached pcap

foo = Proto("foo", "FOO")
foo.fields.string = ProtoField.string("foo.s", "name", "desc")
function foo.dissector( buffer, pinfo, tree )
    local sub = tree:add(foo, buffer())
    local a = buffer(0,22):le_ustring()
    sub:add(foo.fields.string, buffer(0,22), a)
end
DissectorTable.get("tcp.port"):add(5707, foo)

I'd expect frame 6 to have the tree item foo.s="name: Hello World"

Proposed patch

Index: epan/wslua/wslua_tvb.c
===================================================================
--- epan/wslua/wslua_tvb.c    (revision 39010)
+++ epan/wslua/wslua_tvb.c    (working copy)
@@ -1065,6 +1065,31 @@
     WSLUA_RETURN(1); /* The string */
 }

+static int TvbRange_ustring_any(lua_State* L, gboolean little_endian) {
+    /* Obtain a UTF-16 encoded string from a TvbRange */
+    TvbRange tvbr = checkTvbRange(L,1);
+
+    if ( !(tvbr && tvbr->tvb)) return 0;
+    if (tvbr->tvb->expired) {
+        luaL_error(L,"expired tvb");
+        return 0;
+    }
+
+    lua_pushlstring(L,
(gchar*)tvb_get_ephemeral_unicode_string(tvbr->tvb->ws_tvb,tvbr->offset,tvbr->len,
little_endian), tvbr->len );
+
+    return 1; /* The string */
+}
+
+WSLUA_METHOD TvbRange_ustring(lua_State* L) {
+    /* Obtain a Big Endian (network order) UTF-16 encoded string from a
TvbRange */
+    WSLUA_RETURN(TvbRange_ustring_any(L, FALSE)); /* The string */
+}
+
+WSLUA_METHOD TvbRange_le_ustring(lua_State* L) {
+    /* Obtain a Little Endian UTF-16 encoded string from a TvbRange */
+    WSLUA_RETURN(TvbRange_ustring_any(L, TRUE)); /* The string */
+}
+
 WSLUA_METHOD TvbRange_stringz(lua_State* L) {
     /* Obtain a zero terminated string from a TvbRange */
     TvbRange tvbr = checkTvbRange(L,1);
@@ -1234,6 +1259,8 @@
     {"len", TvbRange_len},
     {"offset", TvbRange_offset},
     {"tvb", TvbRange_tvb},
+    {"le_ustring", TvbRange_le_ustring},
+    {"ustring", TvbRange_ustring},
     { NULL, NULL }
 };

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