🛡️ Sentinel: [HIGH] Fix command blocklist bypass via shell splitting

.jules/sentinel.md

@@ -17,3 +17,8 @@
 **Vulnerability:** The `verify_github_sig` function in `apps/server/src/infra_routes.rs` verified GitHub webhook signatures using standard string comparison `expected.eq_ignore_ascii_case(hex_sig)`.
 **Learning:** String comparison functions exit early as soon as a character mismatch is found. In a cryptographic context, this variable response time leaks information and allows an attacker to perform a timing attack to forge a valid HMAC signature by guessing it byte by byte.
 **Prevention:** Always use a constant-time comparison library (like `hmac`'s `verify_slice()`) to compare cryptographic hashes, secrets, and signatures to prevent side-channel timing attacks. Avoid custom implementations of standard cryptographic algorithms.
+
+## 2024-11-04 - Fix command blocklist bypass via trailing spaces
+**Vulnerability:** The blocklist check in `crates/agent/src/tools/workdir_cmd.rs` used `.contains("rm ")` with a space to prevent false positives like "format". However, this failed to block "rm" if it was at the very end of the command string (e.g. `npm run rm`).
+**Learning:** Checking for substrings with spaces is fragile and easily bypassed if the string is the last token in a command without a trailing space.
+**Prevention:** Implement exact match token checking after shell word splitting, while keeping the main string match for multi-word blocks.

crates/agent/src/tools/workdir_cmd.rs

@@ -105,13 +105,26 @@ fn validate_command(raw: &str) -> std::result::Result<Vec<String>, String> {
     if parts.is_empty() {
         return Err("command invalide".into());
     }
+
     let joined = parts.join(" ");
     let lower = joined.to_ascii_lowercase();
     for bad in BLOCKED_TOKENS {
         if lower.contains(bad) {
             return Err(format!("token interdit dans la commande : {bad}"));
         }
     }
+
+    // Validate individual tokenized arguments to prevent quotation/concatenation bypasses
+    for part in &parts {
+        let lower = part.to_ascii_lowercase();
+
+        // Exact match check to block bypasses like `npm run rm`
+        // where "rm " with space fails to match "rm" from the joined string.
+        if lower == "rm" {
+            return Err(format!("commande interdite : {lower}"));
+        }
+    }
+
     let bin = parts[0].as_str();
     let bin_base = Path::new(bin)
         .file_name()