signatures: Add data_end_offset to signature_match() and custom events

This change tracks the current offset (number of bytes fed into matchers)
on the top-level RuleEndpointState such that we can compute the relative ending
for matched texts individually.

Additionally, it adds the data_end_offset as a new optional parameter to
signature_match().

NEWS

@@ -62,6 +62,12 @@ New Functionality
 * The DNS analyzer was extended to support TKEY RRs (RFC 2390). A corresponding
   ``dns_TKEY`` event was added.
 
+* The ``signature_match()`` and custom signature events now receive the end of
+  match offset within the ``data`` parameter as an optional parameter named
+  ``end_of_match``.
+
+	event signature_match(state: signature_state, msg: string, data: string, end_of_match: count);
+
 Changed Functionality
 ---------------------
 

scripts/base/init-bare.zeek

@@ -4527,7 +4527,6 @@ type signature_state: record {
 	conn:         connection;	##< Matching connection.
 	is_orig:      bool;	##< True if matching endpoint is originator.
 	payload_size: count;	##< Payload size of the first matching packet of current endpoint.
-	pattern_end_offset: count &optional; ##< 0-based offset of the last character of the matched payload in the last matching chunk of current endpoint. Non-existing for pure rules
 };
 
 ## A BitTorrent peer.

src/RuleAction.cc

@@ -2,12 +2,17 @@
 
 #include "zeek/zeek-config.h"
 
+#include <algorithm>
 #include <string>
 
 #include "zeek/Conn.h"
+#include "zeek/Desc.h"
 #include "zeek/Event.h"
+#include "zeek/Func.h"
+#include "zeek/ID.h"
 #include "zeek/NetVar.h"
 #include "zeek/RuleMatcher.h"
+#include "zeek/Type.h"
 #include "zeek/analyzer/Manager.h"
 #include "zeek/analyzer/protocol/pia/PIA.h"
 
@@ -18,7 +23,7 @@ namespace zeek::detail {
 bool is_event(const char* id) { return zeek::event_registry->Lookup(id) != nullptr; }
 
 RuleActionEvent::RuleActionEvent(const char* arg_msg)
-    : msg(make_intrusive<StringVal>(arg_msg)), handler(signature_match) {}
+    : msg(make_intrusive<StringVal>(arg_msg)), handler(signature_match), want_end_of_match(true) {}
 
 RuleActionEvent::RuleActionEvent(const char* arg_msg, const char* event_name) {
     if ( arg_msg ) // Message can be null (not provided).
@@ -36,33 +41,75 @@ RuleActionEvent::RuleActionEvent(const char* arg_msg, const char* event_name) {
 
     static const auto& signature_match_params = signature_match->GetFunc()->GetType()->ParamList()->GetTypes();
     // Fabricated params for non-message event(state: signature_state, data: string)
-    static const std::vector<zeek::TypePtr> signature_match2_params = {signature_match_params[0],
+    static const std::vector<zeek::TypePtr> signature_match_no_msg2_params = {signature_match_params[0],
-                                                                       signature_match_params[2]};
+                                                                              signature_match_params[2]};
+    // Fabricated params for non-message event(state: signature_state, data: string, end_of_match: count)
+    static const std::vector<zeek::TypePtr> signature_match_no_msg3_params = {signature_match_params[0],
+                                                                              signature_match_params[2],
+                                                                              signature_match_params[3]};
 
     if ( msg ) {
         // If msg was provided, the function signature needs to agree with
-        // the signature_match event, even if it's a different event.
+        // one of the signature_match() events that take the message.
-        if ( ! handler->GetFunc()->GetType()->CheckArgs(signature_match_params, true, true) )
+        const auto& handler_args_rt = handler->GetType()->Params();
-            zeek::reporter->Error("wrong event parameters for '%s'", event_name);
+        auto prototype = signature_match->GetFunc()->GetType()->FindPrototype(*handler_args_rt);
+
+        // No prototype matched, call CheckArgs() for those where at least
+        // the number of arguments matches for better error messaging (if any).
+        if ( ! prototype ) {
+            for ( const auto& p : signature_match->GetType()->Prototypes() ) {
+                if ( p.args->NumFields() != handler_args_rt->NumFields() )
+                    continue;
+
+                std::vector<TypePtr> tplist;
+                std::for_each(p.args->Types()->begin(), p.args->Types()->end(),
+                              [&tplist](const auto* td) { tplist.push_back(td->type); });
+
+                (void)handler->GetType()->CheckArgs(tplist, true, true);
+            }
+
+            zeek::reporter->Error("wrong event parameters for '%s' (%s)", event_name,
+                                  obj_desc_short(handler_args_rt.get()).c_str());
+            return;
+        }
+
+        // signature_match(state, msg, data, [end_of_match])
+        want_end_of_match = prototype->args->NumFields() > 3;
     }
     else {
         // When no message is provided, use non-message parameters.
-        if ( ! handler->GetFunc()->GetType()->CheckArgs(signature_match2_params, true, true) )
+        const auto& handler_args_rt = handler->GetType()->Params();
+        want_end_of_match = handler_args_rt->NumFields() > 2;
+
+        const auto& check_args =
+            handler_args_rt->NumFields() == 2 ? signature_match_no_msg2_params : signature_match_no_msg3_params;
+
+        if ( ! handler->GetFunc()->GetType()->CheckArgs(check_args, true, true) )
             zeek::reporter->Error("wrong event parameters for '%s'", event_name);
     }
 }
+
 void RuleActionEvent::DoAction(const Rule* parent, RuleEndpointState* state, const u_char* data, int len) {
     if ( handler ) {
         zeek::Args args;
         args.reserve(msg ? 3 : 2);
         args.push_back({AdoptRef{}, rule_matcher->BuildRuleStateValue(parent, state)});
+
         if ( msg )
             args.push_back(msg);
+
         if ( data )
             args.push_back(make_intrusive<StringVal>(len, reinterpret_cast<const char*>(data)));
         else
             args.push_back(zeek::val_mgr->EmptyString());
 
+        if ( want_end_of_match ) {
+            // PList::member_pos() doesn't like const Rule*, need const_cast.
+            int rule_offset = state->matched_by_patterns.member_pos(const_cast<Rule*>(parent));
+            MatchPos end_of_match = (rule_offset >= 0 && data) ? state->matched_text_end_of_match[rule_offset] : 0;
+            args.push_back(zeek::val_mgr->Count(end_of_match));
+        }
+
         event_mgr.Enqueue(handler, std::move(args));
     }
 }

src/RuleAction.h

@@ -43,6 +43,7 @@ public:
 private:
     StringValPtr msg;
     EventHandlerPtr handler;
+    bool want_end_of_match; // Whether handler accepts end_of_match parameter.
 };
 
 class RuleActionMIME : public RuleAction {

src/RuleMatcher.cc

@@ -91,10 +91,6 @@ Val* RuleMatcher::BuildRuleStateValue(const Rule* rule, const RuleEndpointState*
     val->Assign(1, state->GetAnalyzer()->ConnVal());
     val->Assign(2, state->is_orig);
     val->Assign(3, state->payload_size);
-
-    int rule_offset = state->matched_by_patterns.member_pos(const_cast<Rule*>(rule));
-    if ( rule_offset >= 0 )
-        val->Assign(4, state->match_offsets[rule_offset]);
     return val;
 }
 
@@ -180,6 +176,7 @@ void RuleHdrTest::PrintDebug() const {
 RuleEndpointState::RuleEndpointState(analyzer::Analyzer* arg_analyzer, bool arg_is_orig,
                                      RuleEndpointState* arg_opposite, analyzer::pia::PIA* arg_PIA) {
     payload_size = -1;
+    current_pos = 0;
     analyzer = arg_analyzer;
     is_orig = arg_is_orig;
 
@@ -654,8 +651,7 @@ RuleMatcher::MIME_Matches* RuleMatcher::Match(RuleFileMagicState* state, const u
     set<Rule*> rule_matches;
 
     for ( AcceptingMatchSet::const_iterator it = accepted_matches.begin(); it != accepted_matches.end(); ++it ) {
-        AcceptIdx aidx = it->first;
+        auto [aidx, mpos] = *it;
-        MatchPos mpos = it->second;
 
         Rule* r = Rule::rule_table[aidx - 1];
 
@@ -805,12 +801,19 @@ void RuleMatcher::Match(RuleEndpointState* state, Rule::PatternType type, const
             state->payload_size = 0;
     }
 
+    if ( clear )
+        state->current_pos = 0;
+
+    size_t pre_match_pos = state->current_pos;
+
     // Feed data into all relevant matchers.
     for ( const auto& m : state->matchers ) {
         if ( m->type == type && m->state->Match((const u_char*)data, data_len, bol, eol, clear) )
             newmatch = true;
     }
 
+    state->current_pos += data_len;
+
     // If no new match found, we're already done.
     if ( ! newmatch )
         return;
@@ -844,8 +847,7 @@ void RuleMatcher::Match(RuleEndpointState* state, Rule::PatternType type, const
     // Check which of the matching rules really belong to any of our nodes.
 
     for ( set<pair<Rule*, MatchPos>>::const_iterator it = rule_matches.begin(); it != rule_matches.end(); ++it ) {
-        Rule* r = it->first;
+        auto [r, match_end_pos] = *it;
-        MatchPos match_end_offset = it->second;
 
         DBG_LOG(DBG_RULES, "Accepted rule: %s", r->id);
 
@@ -867,7 +869,7 @@ void RuleMatcher::Match(RuleEndpointState* state, Rule::PatternType type, const
                 state->matched_by_patterns.push_back(r);
                 String* s = new String(data, data_len, false);
                 state->matched_text.push_back(s);
-                state->match_offsets.push_back(match_end_offset);
+                state->matched_text_end_of_match.push_back(match_end_pos - pre_match_pos);
             }
 
             DBG_LOG(DBG_RULES, "And has not already fired");

src/RuleMatcher.h

@@ -161,6 +161,7 @@ public:
 
 private:
     friend class RuleMatcher;
+    friend class RuleActionEvent; // For access to match state.
 
     // Constructor is private; use RuleMatcher::InitEndpoint()
     // for creating an instance.
@@ -184,13 +185,14 @@ private:
 
     // The follow tracks which rules for which all patterns have matched,
     // in a parallel list the (first instance of the) corresponding
-	// matched text, and in another parallel list the offset of the
+    // matched text, and in another parallel list the offset of the
-	// end of the last pattern match.
+    // end of the last pattern match.
     rule_list matched_by_patterns;
     bstr_list matched_text;
-    match_offset_list match_offsets;
+    match_offset_list matched_text_end_of_match;
 
     int payload_size;
+    size_t current_pos; // The number of bytes fed into state.
     bool is_orig;
 
     int_list matched_rules; // Rules for which all conditions have matched

src/event.bif

@@ -575,6 +575,11 @@ event file_weird%(name: string, f: fa_file, addl: string%);
 ##       specifics here are not well-defined as Zeek does not buffer any input.
 ##       If a match is split across packet boundaries, only the last chunk
 ##       triggering the match will be passed on to the event.
+## end_of_match: Where within data the pattern match ended. 0 if not applicable or when *data* is empty.
+event signature_match%(state: signature_state, msg: string, data: string, end_of_match: count%);
+
+# Same as above, but allow users to ignore the end_of_match parameter
+# for backwards compatibility, but also convenience.
 event signature_match%(state: signature_state, msg: string, data: string%);
 
 ## Generated each time Zeek's internal profiling log is updated. The file is

testing/btest/Baseline/signatures.custom-event-errors/.stderr

@@ -1,10 +1,9 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
-warning in <...>/custom-event-errors.zeek, line 7: Wrong number of arguments for function. Expected 3, got 2. (event(state:signature_state, data:string))
+error: wrong event parameters for 'wrong_signature2' (record { state:signature_state; data:string; })
-error: wrong event parameters for 'wrong_signature2'
+warning in <...>/custom-event-errors.zeek, line 9: Type mismatch in function argument #2. Expected count, got string. (event(state:signature_state, msg:string, data:string))
-warning in <...>/custom-event-errors.zeek, line 9: Wrong number of arguments for function. Expected 2, got 3. (event(state:signature_state, msg:string, data:string))
 error: wrong event parameters for 'wrong_signature3'
 warning in <...>/custom-event-errors.zeek, line 11: Type mismatch in function argument #1. Expected string, got count. (event(state:signature_state, msg:count, data:string))
-error: wrong event parameters for 'wrong_signature4'
+error: wrong event parameters for 'wrong_signature4' (record { state:signature_state; msg:count; data:string; })
 error: Error in signature (./id.sig:19): identifier is not an event (non_existing_event)
 error: Error in signature (./id.sig:24): identifier is not an event (cat)
 error: Error in signature (./id.sig:29): identifier is not an event (ignore_checksums)

testing/btest/Baseline/signatures.custom-event/out

@@ -1,3 +1,5 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
 signature_match2 [orig_h=127.0.0.1, orig_p=30000/udp, resp_h=127.0.0.1, resp_p=13000/udp]
+signature_match5 [orig_h=127.0.0.1, orig_p=30000/udp, resp_h=127.0.0.1, resp_p=13000/udp] - end_of_match=0
+signature_match4 [orig_h=127.0.0.1, orig_p=30000/udp, resp_h=127.0.0.1, resp_p=13000/udp] - message end_of_match=0
 signature_match3 [orig_h=127.0.0.1, orig_p=30000/udp, resp_h=127.0.0.1, resp_p=13000/udp] - message

testing/btest/Baseline/signatures.tcp-end-of-match-2/.stdout

@@ -0,0 +1,7 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+signature_match, message, 6
+signature_match with end_of_match, message, 6, end_of_match, 2, match, BX
+custom_match with end_of_match, 6, end_of_match, 2, match, BX
+custom_match, 6
+custom_match_with_msg with end_of_match, custom message, 6, end_of_match, 2, match, BX
+custom_match_with_msg, custom message, 6

testing/btest/Baseline/signatures.tcp-end-of-match/.stderr

@@ -0,0 +1 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.

testing/btest/Baseline/signatures.tcp-end-of-match/.stdout

@@ -0,0 +1,7 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+signature_match, message, 1448
+signature_match with end_of_match, message, 1448,    rather than all. (Robin Sommer)\x0a\x0a  * Fix parallel make portability
+portability_match with end_of_match, 1448,    rather than all. (Robin Sommer)\x0a\x0a  * Fix parallel make portability
+portability_match, 1448
+portability_match_with_msg with end_of_match, custom message, 1448, 69,    rather than all. (Robin Sommer)\x0a\x0a  * Fix parallel make portability
+portability_match_with_msg, custom message, 1448

testing/btest/Baseline/signatures.udp-end-of-match/.stderr

@@ -0,0 +1 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.

testing/btest/Baseline/signatures.udp-end-of-match/.stdout

@@ -0,0 +1,5 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+signature_match [orig_h=192.168.17.58, orig_p=58755/udp, resp_h=8.8.8.8, resp_p=53/udp] - my_sig_udp_orig - offset=19
+0000  35 5e 01 00 00 01 00 00  00 00 00 00 06 67 6f 6f  5^...... .....goo
+0010  67 6c 65                                          gle
+

testing/btest/signatures/custom-event.zeek

@@ -10,6 +10,16 @@ signature udp-proto {
   event my_signature_match3 "message"
 }
 
+signature udp-proto-with-offset {
+  ip-proto == 17
+  event my_signature_match4 "message"
+}
+
+signature udp-proto-with-offset-no-msg {
+  ip-proto == 17
+  event my_signature_match5
+}
+
 signature udp-stuff {
   dst-ip == mynets
   event my_signature_match2
@@ -37,3 +47,13 @@ event my_signature_match3(state: signature_state, msg: string, data: string)
 	{
 	print fmt("signature_match3 %s - %s", state$conn$id, msg);
 	}
+
+event my_signature_match4(state: signature_state, msg: string, data: string, end_of_match: count)
+	{
+	print fmt("signature_match4 %s - %s end_of_match=%s", state$conn$id, msg, end_of_match);
+	}
+
+event my_signature_match5(state: signature_state, data: string, end_of_match: count)
+	{
+	print fmt("signature_match5 %s - end_of_match=%s", state$conn$id, end_of_match);
+	}

testing/btest/signatures/tcp-end-of-match.zeek

@@ -0,0 +1,69 @@
+# @TEST-DOC: Check optional end_of_match parameter for signature_match() and custom events.
+# @TEST-EXEC: zeek -b %INPUT -r $TRACES/http/get.trace
+# @TEST-EXEC: btest-diff .stdout
+# @TEST-EXEC: btest-diff .stderr
+
+# Default is 1024, so we don't even peek into the second packet.
+redef dpd_buffer_size = 1024 * 1024;
+
+module DataEndOffset;
+
+export {
+	global portability_match: event(state: signature_state, data: string, end_of_match: count);
+	global portability_match: event(state: signature_state, data: string);
+
+	global portability_match_with_msg: event(state: signature_state, msg: string, data: string, end_of_match: count);
+	global portability_match_with_msg: event(state: signature_state, msg: string, data: string);
+}
+
+@load-sigs ./test.sig
+
+event signature_match(state: signature_state, msg: string, data: string)
+	{
+	print "signature_match", msg, |data|;
+	}
+
+event signature_match(state: signature_state, msg: string, data: string, end_of_match: count)
+	{
+	print "signature_match with end_of_match", msg, |data|, data[:end_of_match];
+	}
+
+event portability_match(state: signature_state, data: string, end_of_match: count)
+	{
+	print "portability_match with end_of_match", |data|, data[:end_of_match];
+	}
+
+event portability_match(state: signature_state, data: string)
+	{
+	print "portability_match", |data|;
+	}
+
+event portability_match_with_msg(state: signature_state, msg: string, data: string, end_of_match: count)
+	{
+	print "portability_match_with_msg with end_of_match", msg, |data|, end_of_match, data[:end_of_match];
+	}
+
+event portability_match_with_msg(state: signature_state, msg: string, data: string)
+	{
+	print "portability_match_with_msg", msg, |data|;
+	}
+
+@TEST-START-FILE test.sig
+signature with-msg {
+	ip-proto == tcp
+	payload /.*portability.*/  # this is in the second packet.
+	event "message"
+}
+
+signature my-custom-event {
+	ip-proto == tcp
+	payload /.*portability.*/  # this is in the second packet.
+	event DataEndOffset::portability_match
+}
+
+signature my-custom-event2 {
+	ip-proto == tcp
+	payload /.*portability.*/  # this is in the second packet.
+	event DataEndOffset::portability_match_with_msg "custom message"
+}
+@TEST-END-FILE

testing/btest/signatures/udp-end-of-match.zeek

@@ -0,0 +1,22 @@
+# @TEST-DOC: Check optional data_end_offset parameter for signature_match()
+# @TEST-EXEC: zeek -b -r $TRACES/dns-caa.pcap %INPUT
+# @TEST-EXEC: btest-diff .stdout
+# @TEST-EXEC: btest-diff .stderr
+
+@load-sigs ./test.sig
+
+event signature_match(state: signature_state, msg: string, data: string, data_end_offset: count)
+	{
+	print fmt("signature_match %s - %s - offset=%s", state$conn$id, msg, data_end_offset);
+	local s = split_string(hexdump(data[:data_end_offset]), /\n/);
+	for ( i in s ) print s[i];
+	}
+
+@TEST-START-FILE test.sig
+signature my_sig_udp_orig {
+	ip-proto == udp
+	payload /.+google/
+	udp-state originator
+	event "my_sig_udp_orig"
+}
+@TEST-END-FILE