test: implement missing glob_fuzz target (#926)

Closes #915

Author: chaliy

.github/workflows/fuzz.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        target: [parser_fuzz, lexer_fuzz, arithmetic_fuzz]
+        target: [parser_fuzz, lexer_fuzz, arithmetic_fuzz, glob_fuzz]
 
     steps:
       - uses: actions/checkout@v6

crates/bashkit/fuzz/Cargo.toml

@@ -45,3 +45,10 @@ path = "fuzz_targets/arithmetic_fuzz.rs"
 test = false
 doc = false
 bench = false
+
+[[bin]]
+name = "glob_fuzz"
+path = "fuzz_targets/glob_fuzz.rs"
+test = false
+doc = false
+bench = false

crates/bashkit/fuzz/fuzz_targets/glob_fuzz.rs

@@ -0,0 +1,78 @@
+//! Fuzz target for glob/pathname expansion
+//!
+//! Tests glob pattern matching and expansion to find:
+//! - Exponential blowup with pathological patterns (TM-DOS-031)
+//! - Stack overflow with deeply nested extglob operators
+//! - Panics on malformed bracket expressions
+//! - Resource exhaustion from recursive globstar patterns
+//!
+//! Run with: cargo +nightly fuzz run glob_fuzz -- -max_total_time=300
+
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|data: &[u8]| {
+    // Only process valid UTF-8
+    if let Ok(input) = std::str::from_utf8(data) {
+        // Limit input size to prevent OOM on huge patterns
+        if input.len() > 512 {
+            return;
+        }
+
+        // Reject deeply nested extglob operators that could blow up
+        let nesting: i32 = input
+            .bytes()
+            .map(|b| match b {
+                b'(' => 1,
+                b')' => -1,
+                _ => 0,
+            })
+            .scan(0i32, |acc, d| {
+                *acc += d;
+                Some(*acc)
+            })
+            .max()
+            .unwrap_or(0);
+        if nesting > 15 {
+            return;
+        }
+
+        let rt = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .unwrap();
+
+        rt.block_on(async {
+            // Build a small VFS with some files to match against
+            let mut bash = bashkit::Bash::builder()
+                .limits(
+                    bashkit::ExecutionLimits::new()
+                        .max_commands(50)
+                        .timeout(std::time::Duration::from_millis(200)),
+                )
+                .mount_text("/tmp/a.txt", "")
+                .mount_text("/tmp/b.sh", "")
+                .mount_text("/tmp/c.md", "")
+                .mount_text("/tmp/sub/d.txt", "")
+                .mount_text("/tmp/sub/e.rs", "")
+                .mount_text("/tmp/.hidden", "")
+                .build();
+
+            // Test 1: glob expansion via ls (triggers expand_glob)
+            let script = format!("ls /tmp/{} 2>/dev/null; true", input);
+            let _ = bash.exec(&script).await;
+
+            // Test 2: pattern matching via case statement
+            let script2 = format!(
+                "case \"test.txt\" in {}) echo match;; *) echo no;; esac",
+                input
+            );
+            let _ = bash.exec(&script2).await;
+
+            // Test 3: [[ conditional pattern matching
+            let script3 = format!("if [[ \"hello.world\" == {} ]]; then echo y; fi", input);
+            let _ = bash.exec(&script3).await;
+        });
+    }
+});