From 271c3af797311222713e1573330fe45bb5609e6a Mon Sep 17 00:00:00 2001
From: Yves Orton <demerphq@gmail.com>
Date: Sun, 20 Feb 2022 10:38:09 +0100
Subject: regex engine: Issue #19168 - Fix variable length lookbehind matches

We were not validating that when (?<=a|ab) matched that the right hand
side of the match lined up with the position of the assertion. Similar
for (?<!a|ab) and related patterns, eg, (*positive_lookbehind:).
Note these problems do NOT affect lookahead.

Part of the difficulty here was that the SUCCEED node was serving too
many purposes, necessitating a new regop LOOKBEHIND_END.

Includes more tests for various lookahead or lookbehind cases.
---
 regcomp.sym | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'regcomp.sym')

diff --git a/regcomp.sym b/regcomp.sym
index 510a6162be..bdf6e47551 100644
--- a/regcomp.sym
+++ b/regcomp.sym
@@ -282,6 +282,9 @@ CUTGROUP    VERB,       no-sv 1   ; On failure go to the next alternation in the
 #*Control what to keep in $&.
 KEEPS       KEEPS,      no        ; $& begins here.
 
+#*Validate that lookbehind IFMATCH and UNLESSM end at the right place
+LOOKBEHIND_END   END,        no        ; Return from lookbehind (IFMATCH/UNLESSM) and validate position
+
 # NEW STUFF SOMEWHERE ABOVE THIS LINE.  Stuff that regexec.c: find_byclass()
 # and regrepeat() use should go way above, near LNBREAK to allow a more compact
 # jump table to be generated for their switch() statements
-- 
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