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dcerpc: mimic gap behavior for invalid data #14766

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dcerpc: mimic gap behavior for invalid data #14766

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74 changes: 47 additions & 27 deletions rust/src/dcerpc/dcerpc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -762,21 +762,20 @@ impl DCERPCState {
}
}

pub fn handle_input_data(&mut self, stream_slice: StreamSlice, direction: Direction) -> AppLayerResult {
let retval;
let mut cur_i = stream_slice.as_slice();
let mut consumed = 0u32;
let mut rem = cur_i.len() as u32;
fn handle_gap (&mut self, i: &[u8], direction: Direction, mimic: bool) -> (u32, i8) {
let mut consumed;

if !mimic && ((self.ts_gap && direction != Direction::ToServer) || (self.tc_gap && direction != Direction::ToClient)) {
return (0, 0);
}
// Skip the record since this means that its in the middle of a known length record
if (self.ts_gap && direction == Direction::ToServer) || (self.tc_gap && direction == Direction::ToClient) {
SCLogDebug!("Trying to catch up after GAP (input {})", cur_i.len());
match self.search_dcerpc_record(cur_i) {
Ok((_, pg)) => {
SCLogDebug!("DCERPC record found");
let offset = cur_i.len() - pg.len();
cur_i = &cur_i[offset..];
consumed = offset as u32;
SCLogDebug!("Trying to catch up after GAP (input {})", i.len());
match self.search_dcerpc_record(i) {
Ok((_, pg)) => {
SCLogDebug!("DCERPC record found");
let offset = i.len() - pg.len();
consumed = offset as u32;
if !mimic {
match direction {
Direction::ToServer => {
self.ts_gap = false;
Expand All @@ -785,20 +784,35 @@ impl DCERPCState {
self.tc_gap = false;
}
}
},
_ => {
consumed = cur_i.len() as u32;
// At least 2 bytes are required to know if a new record is beginning
if consumed < 2 {
consumed = 0;
} else {
consumed -= 1;
}
SCLogDebug!("DCERPC record NOT found");
return AppLayerResult::incomplete(consumed, 2);
},
}
}
},
_ => {
consumed = i.len() as u32;
// At least 2 bytes are required to know if a new record is beginning
if consumed < 2 {
consumed = 0;
} else {
consumed -= 1;
}
SCLogDebug!("DCERPC record NOT found");
return (consumed, -1);
},
}

(consumed, 0)
}

pub fn handle_input_data(&mut self, stream_slice: StreamSlice, direction: Direction) -> AppLayerResult {
let retval;
let mut cur_i = stream_slice.as_slice();
let mut rem = cur_i.len() as u32;

let (nb, ret) = self.handle_gap(cur_i, direction, false /* handling the actual gap */);
let mut consumed = nb;
if ret == -1 {
return AppLayerResult::incomplete(consumed, 2);
}
cur_i = &cur_i[consumed as usize..];
rem -= consumed;

let mut flow = std::ptr::null_mut();
Expand All @@ -817,7 +831,13 @@ impl DCERPCState {
header.rpc_vers,
header.rpc_vers_minor
);
return AppLayerResult::err();

let (nb, ret) = self.handle_gap(cur_i, direction, true /* mimicing a gap */);
consumed += nb;
/* no need to update rem/cur_i as it won't be used anymore */
if ret == -1 {
return AppLayerResult::incomplete(consumed, 2);
}
}
header
}
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