rust/smb/dcerpc: parse context id

As context id is used to know to which variant of the endpoint the
request is done, it is interesting to parse it.

Feature #5413.

rust/src/smb/dcerpc.rs

@@ -69,6 +69,7 @@ pub struct DCERPCIface {
     pub ack_result: u16,
     pub ack_reason: u16,
     pub acked: bool,
+    pub context_id: u16,
 }
 
 impl DCERPCIface {
@@ -85,6 +86,7 @@ impl DCERPCIface {
 #[derive(Default, Debug)]
 pub struct SMBTransactionDCERPC {
     pub opnum: u16,
+    pub context_id: u16,
     pub req_cmd: u8,
     pub req_set: bool,
     pub res_cmd: u8,
@@ -100,6 +102,7 @@ impl SMBTransactionDCERPC {
     fn new_request(req: u8, call_id: u32) -> Self {
         return Self {
             opnum: 0,
+            context_id: 0,
             req_cmd: req,
             req_set: true,
             call_id: call_id,
@@ -236,6 +239,7 @@ pub fn smb_write_dcerpc_record<'b>(state: &mut SMBState,
                                 SCLogDebug!("first frag size {}", recr.data.len());
                                 tdn.stub_data_ts.extend_from_slice(recr.data);
                                 tdn.opnum = recr.opnum;
+                                tdn.context_id = recr.context_id;
                                 tdn.frag_cnt_ts += 1;
                                 SCLogDebug!("DCERPC: REQUEST opnum {} stub data len {}",
                                         tdn.opnum, tdn.stub_data_ts.len());

rust/src/smb/dcerpc_records.rs

@@ -48,6 +48,7 @@ pub fn parse_dcerpc_response_record(i:&[u8], frag_len: u16 )
 #[derive(Debug,PartialEq)]
 pub struct DceRpcRequestRecord<'a> {
     pub opnum: u16,
+    pub context_id: u16,
     pub data: &'a[u8],
 }
 
@@ -59,11 +60,12 @@ pub fn parse_dcerpc_request_record(i:&[u8], frag_len: u16, little: bool)
     if frag_len < 24 {
         return Err(Err::Error(SmbError::RecordTooSmall));
     }
-    let (i, _) = take(6_usize)(i)?;
+    let (i, _) = take(4_usize)(i)?;
     let endian = if little { Endianness::Little } else { Endianness::Big };
+    let (i, context_id) = u16(endian)(i)?;
     let (i, opnum) = u16(endian)(i)?;
     let (i, data) = take(frag_len - 24)(i)?;
-    let record = DceRpcRequestRecord { opnum, data };
+    let record = DceRpcRequestRecord { opnum, context_id, data };
     Ok((i, record))
 }