http1: keep monotonic progress for 100-continue

Ticket: 9096

In case of a 100-continue response, we used to
- parse the response line, set progress to headers
- parse headers, set progress back to line

This caused FPs as the engine expects the progress to just increase
so that it skips signatures that did not match yet, and whose
progress is less than the tx progress.

Solution is to keep progress at line when we see a 100 response,
until we get to the body, or after a next response line which
is not 100.

rust/htp/src/response.rs

@@ -80,9 +80,9 @@ impl ConnectionParser {
             input.reset_callback_start();
 
             match resp.response_progress {
-                HtpResponseProgress::HEADERS => self.response_receiver_set(header_fn),
                 HtpResponseProgress::TRAILER => self.response_receiver_set(trailer_fn),
-                _ => Ok(()),
+                // response_state == State::Headers can have progress LINE after a 100 continue
+                _ => self.response_receiver_set(header_fn),
             }?;
         }
         // Same comment as in request_handle_state_change(). Below is a copy.
@@ -465,7 +465,6 @@ impl ConnectionParser {
                     let response_tx = self.response_mut().unwrap();
                     // Ignore any response headers seen so far.
                     response_tx.response_headers.elements.clear();
-                    response_tx.response_progress = HtpResponseProgress::LINE;
                     response_tx.seen_100continue = true;
                     return Ok(());
                 }
@@ -729,7 +728,12 @@ impl ConnectionParser {
         self.state_response_line()?;
         // Move on to the next phase.
         self.response_state = State::Headers;
-        self.response_mut().unwrap().response_progress = HtpResponseProgress::HEADERS;
+        let response_tx = self.response_mut().unwrap();
+        // delay progress in case of a 100 continue
+        // so we do not revert progress to line after headers
+        if !response_tx.response_status_number.eq_num(100) {
+            response_tx.response_progress = HtpResponseProgress::HEADERS;
+        }
         Ok(())
     }
 
@@ -1013,7 +1017,8 @@ impl ConnectionParser {
             }
             // We've seen all response headers. At terminator.
             self.response_state =
-                if self.response().unwrap().response_progress == HtpResponseProgress::HEADERS {
+                // we can have response progress LINE in case of 100 continue
+                if self.response().unwrap().response_progress <= HtpResponseProgress::HEADERS {
                     // Response headers.
                     // The next step is to determine if this response has a body.
                     State::BodyDetermine