From 57fbf053880b92e5832443672eaea3b092dff549 Mon Sep 17 00:00:00 2001
From: Ed Kellett <e@kellett.im>
Date: Fri, 30 Oct 2020 01:06:07 +0000
Subject: [PATCH] Fix a corner case of superset matching

The algorithm we're using gets stuck if it has a ? and can only see a *
to feed to it, even if it could skip over that * and consume a character
following it. Remedy this by rearranging the input so * always precedes
? in runs of wildcards, so when we're matching ? we know we can skip
things.
---
 ircd/match.c   | 33 +++++++++++++++++++++++++++++++--
 tests/match1.c | 23 +++++++++++++++++++++++
 2 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/ircd/match.c b/ircd/match.c
index a8165ffb..417e2ccd 100644
--- a/ircd/match.c
+++ b/ircd/match.c
@@ -104,6 +104,30 @@ int match(const char *mask, const char *name)
 	}
 }
 
+void
+match_arrange_stars(char *mask)
+{
+	char *swap = NULL;
+
+	for (char *p = mask; *p != '\0'; p++)
+	{
+		switch (*p)
+		{
+		case '*':
+			if (swap == NULL) break;
+			*swap++ = '*';
+			*p = '?';
+			break;
+		case '?':
+			if (swap == NULL) swap = p;
+			break;
+		default:
+			swap = NULL;
+			break;
+		}
+	}
+}
+
 /** Check a mask against a mask.
  * This test checks using traditional IRC wildcards only: '*' means
  * match zero or more characters of any type; '?' means match exactly
@@ -115,15 +139,19 @@ int match(const char *mask, const char *name)
  * @param[in] name New wildcard-containing mask.
  * @return 1 if \a name is equal to or more specific than \a mask, 0 otherwise.
  */
-int mask_match(const char *mask, const char *name)
+int mask_match(const char *mask_, const char *name)
 {
+	static char mask[BUFSIZE];
 	const char *m = mask, *n = name;
 	const char *m_tmp = mask, *n_tmp = name;
 	int star_p;
 
-	s_assert(mask != NULL);
+	s_assert(mask_ != NULL);
 	s_assert(name != NULL);
 
+	rb_strlcpy(mask, mask_, sizeof mask);
+	match_arrange_stars(mask);
+
 	for (;;)
 	{
 		switch (*m)
@@ -146,6 +174,7 @@ int mask_match(const char *mask, const char *name)
 				  else if (*m == '?')
 				  {
 					  /* changed for mask_match() */
+					  while (star_p && *n == '*') n++;
 					  if (*n == '*' || !*n)
 						  goto backtrack;
 					  n++;
diff --git a/tests/match1.c b/tests/match1.c
index 9d118ed6..913f71d7 100644
--- a/tests/match1.c
+++ b/tests/match1.c
@@ -30,6 +30,8 @@
 
 struct Client me;
 
+void match_arrange_stars(char *);
+
 static void test_match(void)
 {
 	is_int(0, match("*foo*", "bar"), MSG);
@@ -40,6 +42,7 @@ static void test_match(void)
 
 static void test_mask_match(void)
 {
+
 	is_int(0, mask_match("*foo*", "bar"), MSG);
 	is_int(1, mask_match("*foo*", "foo"), MSG);
 
@@ -63,12 +66,32 @@ static void test_mask_match(void)
 	is_int(0, mask_match("??", "aaa"), MSG);
 }
 
+static void test_arrange_stars(void)
+{
+	{
+		char rearrange[] = "quick brown fox";
+		match_arrange_stars(rearrange);
+		is_string("quick brown fox", rearrange, MSG);
+	}
+	{
+		char rearrange[] = "?*?*?*";
+		match_arrange_stars(rearrange);
+		is_string("***???", rearrange, MSG);
+	}
+	{
+		char rearrange[] = "?*? *?*";
+		match_arrange_stars(rearrange);
+		is_string("*?? **?", rearrange, MSG);
+	}
+}
+
 int main(int argc, char *argv[])
 {
 	plan_lazy();
 
 	test_match();
 	test_mask_match();
+	test_arrange_stars();
 
 	return 0;
 }