jdx/mise · error

brew-cask: binary target

Error message

brew-cask: binary target '{}' must not contain '..'

What it means

This error is thrown by `binary_target_path` in src/system/packages/brew/cask/paths.rs when the fully resolved binary target path contains a `..` (ParentDir) component. The library rejects parent-directory traversal so a cask binary cannot be linked outside the sanctioned Homebrew/appdir trees; this is a path-traversal guard applied after `$HOMEBREW_PREFIX` substitution and prefix-relative resolution.

Solutions

  1. Rewrite the binary target as an absolute path or one relative to the Homebrew prefix without any `..` components
  2. Use `$HOMEBREW_PREFIX` substitution instead of climbing with `..` to reach another tree
  3. Verify the cask formula is from a trusted source; a `..` in an official formula is suspicious
  4. If the intended binary is genuinely outside the allowed roots, link it manually instead of via this path

Example fix

// before
binary_target_path("$HOMEBREW_PREFIX/bin/../libexec/tool", &appdir)
// error: binary target must not contain '..'

// after
binary_target_path("$HOMEBREW_PREFIX/libexec/tool", &appdir)
Defensive patterns

Strategy: validation

Validate before calling

fn target_has_parent_dir(target: &std::path::Path) -> bool {
    target.components().any(|c| matches!(c, std::path::Component::ParentDir))
}

Type guard

fn safe_target(t: &str) -> Option<&str> {
    if target_has_parent_dir(std::path::Path::new(t)) { None } else { Some(t) }
}

Try / catch

match binary_target_path(target_name, &appdir) {
    Ok(path) => use(path),
    Err(e) if e.to_string().contains("must not contain '..'") => rewrite_without_traversal(target_name),
    Err(e) => return Err(e),
}

Prevention

When it happens

Trigger: Calling `binary_target_path(target_name, appdir)` where, after replacing `$HOMEBREW_PREFIX` and resolving bare names to `<prefix>/bin/<name>`, the resulting path contains a `..` component — e.g. `../evil`, `$HOMEBREW_PREFIX/bin/../../tmp/x`, or `$APPDIR/../elsewhere` (that last one is caught earlier by `reject_appdir_escape` but the same rule applies to prefix targets).

Common situations: A malicious or buggy cask formula uses relative escapes; a user hand-edits a binary stanza with `..`; generated target strings from scripts accidentally embed `..`; migration of a formula from another manager kept relative links.

Understand the failure class

Background: Path traversal blocked: "path escapes the workspace" and "outside site root" errors when a path will not stay inside its allowed directory — this error's family across 26 libraries.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/4a5d7b1723b1d4de. Report an issue: GitHub.

Appendix: source

Thrown at src/system/packages/brew/cask/paths.rs:298

    if target_name.contains("$APPDIR") {
        bail!("brew-cask: $APPDIR must prefix a binary target");
    }
    let prefix = prefix::prefix();
    let prefix_str = prefix.to_string_lossy();
    let target_name = target_name.replace("$HOMEBREW_PREFIX", prefix_str.as_ref());
    let path = PathBuf::from(&target_name);
    let target = if path.is_absolute() {
        path
    } else if target_name.contains('/') {
        prefix.join(path)
    } else {
        prefix.join("bin").join(path)
    };
    if target
        .components()
        .any(|component| matches!(component, Component::ParentDir))
    {
        bail!(
            "brew-cask: binary target '{}' must not contain '..'",
            target.display()
        );
    }
    let roots = allowed_binary_target_roots();
    if !roots.iter().any(|root| target.starts_with(root)) {
        bail!(
            "brew-cask: binary target '{}' must be under {}",
            target.display(),
            allowed_binary_target_roots_display(&roots)
        );
    }
    Ok(target)
}

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