Refactor preserved path guard

codex-rs/shell-command/src/lib.rs

@@ -6,6 +6,8 @@ pub mod bash;
 pub(crate) mod command_safety;
 pub mod parse_command;
 pub mod powershell;
+mod preserved_path_write;
 
 pub use command_safety::is_dangerous_command;
 pub use command_safety::is_safe_command;
+pub use preserved_path_write::preserved_path_write_forbidden_reason;

codex-rs/shell-command/src/preserved_path_write.rs

@@ -0,0 +1,290 @@
+use std::path::Path;
+use std::path::PathBuf;
+
+use codex_protocol::permissions::FileSystemSandboxPolicy;
+use codex_protocol::permissions::forbidden_agent_preserved_path_write;
+
+pub fn preserved_path_write_forbidden_reason(
+    command: &[String],
+    cwd: &Path,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+) -> Option<String> {
+    let commands = crate::bash::parse_shell_lc_plain_commands(command)
+        .or_else(|| crate::bash::parse_shell_lc_command_word_prefixes(command))
+        .unwrap_or_else(|| vec![command.to_vec()]);
+
+    for simple_command in commands {
+        if let Some(name) =
+            simple_command_preserved_path_write(&simple_command, cwd, file_system_sandbox_policy)
+        {
+            return Some(preserved_path_write_reason(name));
+        }
+    }
+
+    if let Some(targets) = crate::bash::parse_shell_lc_write_redirection_targets(command) {
+        for target in targets {
+            if let Some(name) = forbidden_agent_preserved_path_write(
+                Path::new(&target),
+                cwd,
+                file_system_sandbox_policy,
+            ) {
+                return Some(preserved_path_write_reason(name));
+            }
+        }
+    }
+    None
+}
+
+fn preserved_path_write_reason(name: &str) -> String {
+    format!("command targets preserved workspace metadata path `{name}`")
+}
+
+fn simple_command_preserved_path_write(
+    command: &[String],
+    cwd: &Path,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+) -> Option<&'static str> {
+    let program = command.first().map(|program| {
+        Path::new(program)
+            .file_name()
+            .and_then(|name| name.to_str())
+            .unwrap_or(program)
+    })?;
+
+    match program {
+        "git" => git_init_preserved_path_write(command, cwd, file_system_sandbox_policy),
+        "touch" | "mkdir" | "rm" | "rmdir" | "ln" | "mv" | "cp" | "install" => command
+            .iter()
+            .skip(1)
+            .filter(|arg| !arg.starts_with('-'))
+            .find_map(|arg| {
+                forbidden_agent_preserved_path_write(
+                    Path::new(arg),
+                    cwd,
+                    file_system_sandbox_policy,
+                )
+            }),
+        _ => None,
+    }
+}
+
+fn git_init_preserved_path_write(
+    command: &[String],
+    cwd: &Path,
+    file_system_sandbox_policy: &FileSystemSandboxPolicy,
+) -> Option<&'static str> {
+    let mut git_cwd = PathBuf::from(cwd);
+    let mut index = 1;
+
+    while index < command.len() {
+        match command[index].as_str() {
+            "-C" => {
+                let next = command.get(index + 1)?;
+                git_cwd = resolve_shell_operand(Path::new(next), &git_cwd);
+                index += 2;
+            }
+            "--" => {
+                index += 1;
+                break;
+            }
+            arg if arg.starts_with('-') => {
+                index += 1;
+            }
+            _ => break,
+        }
+    }
+
+    if command.get(index).map(String::as_str) != Some("init") {
+        return None;
+    }
+
+    let init_target = command
+        .iter()
+        .skip(index + 1)
+        .find(|arg| !arg.starts_with('-'))
+        .map_or_else(
+            || git_cwd.clone(),
+            |arg| resolve_shell_operand(Path::new(arg), &git_cwd),
+        );
+
+    forbidden_agent_preserved_path_write(
+        init_target.join(".git").as_path(),
+        &git_cwd,
+        file_system_sandbox_policy,
+    )
+}
+
+fn resolve_shell_operand(path: &Path, cwd: &Path) -> PathBuf {
+    if path.is_absolute() {
+        path.to_path_buf()
+    } else {
+        cwd.join(path)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+    use std::path::PathBuf;
+
+    use codex_protocol::permissions::FileSystemSandboxPolicy;
+    use codex_protocol::protocol::ReadOnlyAccess;
+    use codex_protocol::protocol::SandboxPolicy;
+    use pretty_assertions::assert_eq;
+
+    use super::preserved_path_write_forbidden_reason;
+
+    struct TestDir {
+        path: PathBuf,
+    }
+
+    impl TestDir {
+        fn new(name: &str) -> Self {
+            let path = std::env::temp_dir().join(format!(
+                "codex-preserved-path-write-{name}-{}",
+                std::process::id()
+            ));
+            let _ = std::fs::remove_dir_all(&path);
+            std::fs::create_dir(&path).expect("create tempdir");
+            Self { path }
+        }
+
+        fn path(&self) -> &Path {
+            &self.path
+        }
+    }
+
+    impl Drop for TestDir {
+        fn drop(&mut self) {
+            let _ = std::fs::remove_dir_all(&self.path);
+        }
+    }
+
+    fn legacy_workspace_write_policy(cwd: &Path) -> FileSystemSandboxPolicy {
+        let policy = SandboxPolicy::WorkspaceWrite {
+            writable_roots: vec![],
+            read_only_access: ReadOnlyAccess::Restricted {
+                include_platform_defaults: false,
+                readable_roots: vec![],
+            },
+            network_access: false,
+            exclude_tmpdir_env_var: true,
+            exclude_slash_tmp: true,
+        };
+        FileSystemSandboxPolicy::from_legacy_sandbox_policy(&policy, cwd)
+    }
+
+    #[test]
+    fn preserved_path_detector_blocks_git_init_under_parent_repo() {
+        let repo = TestDir::new("git-init-under-parent-repo");
+        std::fs::create_dir(repo.path().join(".git")).expect("create parent .git");
+        let cwd = repo.path().join("sub");
+        std::fs::create_dir(&cwd).expect("create cwd");
+        let policy = legacy_workspace_write_policy(&cwd);
+
+        let reason = preserved_path_write_forbidden_reason(
+            &[
+                "/bin/bash".to_string(),
+                "-lc".to_string(),
+                "git init".to_string(),
+            ],
+            &cwd,
+            &policy,
+        );
+
+        assert_eq!(
+            reason,
+            Some("command targets preserved workspace metadata path `.git`".to_string())
+        );
+    }
+
+    #[test]
+    fn preserved_path_detector_allows_normal_git_under_parent_repo() {
+        let repo = TestDir::new("normal-git-under-parent-repo");
+        std::fs::create_dir(repo.path().join(".git")).expect("create parent .git");
+        let cwd = repo.path().join("sub");
+        std::fs::create_dir(&cwd).expect("create cwd");
+        let policy = legacy_workspace_write_policy(&cwd);
+
+        let reason = preserved_path_write_forbidden_reason(
+            &[
+                "/bin/bash".to_string(),
+                "-lc".to_string(),
+                "git status --short".to_string(),
+            ],
+            &cwd,
+            &policy,
+        );
+
+        assert_eq!(reason, None);
+    }
+
+    #[test]
+    fn preserved_path_detector_blocks_direct_preserved_path_writes() {
+        let cwd = TestDir::new("direct-preserved-path-writes");
+        let policy = legacy_workspace_write_policy(cwd.path());
+
+        let reason = preserved_path_write_forbidden_reason(
+            &[
+                "/bin/bash".to_string(),
+                "-lc".to_string(),
+                "touch .git && mkdir -p .codex".to_string(),
+            ],
+            cwd.path(),
+            &policy,
+        );
+
+        assert_eq!(
+            reason,
+            Some("command targets preserved workspace metadata path `.git`".to_string())
+        );
+    }
+
+    #[test]
+    fn preserved_path_detector_blocks_preserved_path_redirections() {
+        let repo = TestDir::new("preserved-path-redirections");
+        std::fs::create_dir(repo.path().join(".git")).expect("create parent .git");
+        let cwd = repo.path().join("sub");
+        std::fs::create_dir(&cwd).expect("create cwd");
+        let policy = legacy_workspace_write_policy(&cwd);
+
+        let reason = preserved_path_write_forbidden_reason(
+            &[
+                "/bin/bash".to_string(),
+                "-lc".to_string(),
+                "printf pwned > .git".to_string(),
+            ],
+            &cwd,
+            &policy,
+        );
+
+        assert_eq!(
+            reason,
+            Some("command targets preserved workspace metadata path `.git`".to_string())
+        );
+    }
+
+    #[test]
+    fn preserved_path_detector_blocks_git_init_inside_complex_script() {
+        let repo = TestDir::new("git-init-inside-complex-script");
+        std::fs::create_dir(repo.path().join(".git")).expect("create parent .git");
+        let cwd = repo.path().join("sub");
+        std::fs::create_dir(&cwd).expect("create cwd");
+        let policy = legacy_workspace_write_policy(&cwd);
+
+        let reason = preserved_path_write_forbidden_reason(
+            &[
+                "/bin/bash".to_string(),
+                "-lc".to_string(),
+                "set -e\nif git init -q; then\n  exit 22\nfi".to_string(),
+            ],
+            &cwd,
+            &policy,
+        );
+
+        assert_eq!(
+            reason,
+            Some("command targets preserved workspace metadata path `.git`".to_string())
+        );
+    }
+}