🛡️ Sentinel: [CRITICAL] Fix command validation bypass

.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.
+
+## 2024-05-24 - Workdir Command Validation Vulnerability
+**Vulnerability:** The command validator (`validate_command` in `workdir_cmd.rs`) used `joined.to_ascii_lowercase().contains(bad)` against a list of blocked tokens like `rm ` to prevent command injection and destructive behavior. This is vulnerable if an attacker provides a command like `npm run rm`, which bypasses `rm ` (because there's no trailing space) but might still execute `rm`. Furthermore, the application relies solely on string matching, creating a bypass risk.
+**Learning:** Checking for substrings against joined shell commands doesn't sufficiently protect against commands without expected spacing or specific subcommands. When validating inputs for a process executor, we need to inspect both the full joined string (for multi-word blocked phrases) AND the individual tokenized arguments to ensure exact matches for sensitive/blocked binaries or commands are caught. Relying solely on one method breaks either multi-word substring blocks or exact single word matches.
+**Prevention:** Iteratively check each tokenized argument exactly against dangerous terms like `"rm"`, `"chmod"`, or `"chown"` in addition to substring checks on the entire command string.

crates/agent/src/tools/workdir_cmd.rs

@@ -112,6 +112,13 @@ fn validate_command(raw: &str) -> std::result::Result<Vec<String>, String> {
             return Err(format!("token interdit dans la commande : {bad}"));
         }
     }
+
+    for p in &parts {
+        let p_lower = p.to_ascii_lowercase();
+        if p_lower == "rm" || p_lower == "chmod" || p_lower == "chown" {
+             return Err(format!("token interdit dans la commande : {p}"));
+        }
+    }
     let bin = parts[0].as_str();
     let bin_base = Path::new(bin)
         .file_name()
@@ -340,6 +347,13 @@ mod tests {
         assert_eq!(p[0], "npm");
     }
 
+    #[test]
+    fn blocks_npm_run_rm() {
+        assert!(validate_command("npm run rm").is_err());
+        assert!(validate_command("npm run chmod").is_err());
+        assert!(validate_command("npm run chown").is_err());
+    }
+
     #[test]
     fn blocks_pipe() {
         assert!(validate_command("npm run build | cat").is_err());