From 53ef97231df3f32a6b7d908a5e13e1ad4e049cac Mon Sep 17 00:00:00 2001
From: Fabio Bozzo <fabio.bozzo@consensys.net>
Date: Tue, 17 Sep 2024 13:18:12 +0200
Subject: [PATCH] iterative glob.go and limit FuzzMatch input size

---
 capability/policy/glob.go       | 64 +++++++++++++--------------------
 capability/policy/match_test.go |  6 ++++
 2 files changed, 31 insertions(+), 39 deletions(-)

diff --git a/capability/policy/glob.go b/capability/policy/glob.go
index 23fe8f2..5ab2f9b 100644
--- a/capability/policy/glob.go
+++ b/capability/policy/glob.go
@@ -22,7 +22,7 @@ func validateGlobPattern(pattern string) bool {
 	return true
 }
 
-// globMatch matches a string against a pattern with '*' wildcards, handling escaped '\*' literals.
+// globMatch matches a string against a pattern with * wildcards, handling escaped '\*' literals.
 func globMatch(pattern, str string) bool {
 	if !validateGlobPattern(pattern) {
 		return false
@@ -31,55 +31,41 @@ func globMatch(pattern, str string) bool {
 	// i is the index for the pattern
 	// j is the index for the string
 	var i, j int
-	for i < len(pattern) && j < len(str) {
-		switch pattern[i] {
-		case '*':
-			// skip consecutive '*' characters
-			for i < len(pattern) && pattern[i] == '*' {
-				i++
-			}
-			if i == len(pattern) {
-				return true
-			}
 
-			// match the rest of the pattern
-			for j < len(str) {
-				if globMatch(pattern[i:], str[j:]) {
-					return true
-				}
-				j++
-			}
+	// starIdx keeps track of the position of the last * in the pattern.
+	// matchIdx keeps track of the position in the string where the last * matched.
+	var starIdx, matchIdx int = -1, -1
 
-			return false
-		case '\\':
-			// handle escaped '*'
-			i++
-			if i < len(pattern) && pattern[i] == '*' {
-				if str[j] != '*' {
-					return false
-				}
+	for j < len(str) {
+		if i < len(pattern) && (pattern[i] == str[j] || pattern[i] == '\\' && i+1 < len(pattern) && pattern[i+1] == str[j]) {
+			// characters match or if there's an escaped character that matches
+			if pattern[i] == '\\' {
+				// skip the escape character
 				i++
-				j++
-			} else {
-				if i >= len(pattern) || pattern[i] != str[j] {
-					return false
-				}
-				i++
-				j++
-			}
-		default:
-			if pattern[i] != str[j] {
-				return false
 			}
 			i++
 			j++
+		} else if i < len(pattern) && pattern[i] == '*' {
+			// there's a * wildcard in the pattern
+			starIdx = i
+			matchIdx = j
+			i++
+		} else if starIdx != -1 {
+			// there's a previous * wildcard, backtrack
+			i = starIdx + 1
+			matchIdx++
+			j = matchIdx
+		} else {
+			// no match found
+			return false
 		}
 	}
 
-	// check for remaining characters in pattern
+	// check for remaining characters in the pattern
 	for i < len(pattern) && pattern[i] == '*' {
 		i++
 	}
 
-	return i == len(pattern) && j == len(str)
+	// the entire pattern is processed, it's a match
+	return i == len(pattern)
 }
diff --git a/capability/policy/match_test.go b/capability/policy/match_test.go
index 4f7dc9b..d7d9360 100644
--- a/capability/policy/match_test.go
+++ b/capability/policy/match_test.go
@@ -491,6 +491,8 @@ func TestPolicyExamples(t *testing.T) {
 	})
 }
 
+const maxFuzzInputLength = 128
+
 func FuzzMatch(f *testing.F) {
 	// Policy + Data examples
 	f.Add([]byte(`[["==", ".status", "draft"]]`), []byte(`{"status": "draft"}`))
@@ -520,6 +522,10 @@ func FuzzMatch(f *testing.F) {
 	)
 
 	f.Fuzz(func(t *testing.T, policyBytes []byte, dataBytes []byte) {
+		if len(policyBytes) > maxFuzzInputLength || len(dataBytes) > maxFuzzInputLength {
+			t.Skip()
+		}
+
 		policyNode, err := ipld.Decode(policyBytes, dagjson.Decode)
 		if err != nil {
 			t.Skip()