Zip Slip in Actix with Api Keys

Zip Slip is a path traversal vulnerability where an attacker-supplied archive causes files to be extracted outside the intended directory. When Api Keys are handled insecurely in an Actix-based API, the combination can expose both the keys and the application to path traversal. For example, if an endpoint accepts an uploaded archive and uses user-controlled metadata (such as a request header containing an Api Key) to construct extraction paths, insufficient validation allows ../ sequences to escape the target directory.

Consider an Actix service that authenticates requests via an Api Key passed in a header and then processes uploaded archives. If the service uses the Api Key to derive a storage subdirectory without normalizing or restricting paths, an attacker can supply a malicious archive containing files like ../../etc/passwd. During extraction, the traversal sequences write files outside the intended location, potentially overwriting configuration or sensitive files. Because the Api Key is tied to authentication and authorization logic, its exposure through path traversal can grant an attacker insight into key storage patterns or facilitate further compromise.

Insecure code pattern in Actix might look like accepting an archive and concatenating the Api Key directly into a path:

use actix_web::{web, HttpResponse, Error};
use std::path::Path;

async fn extract_archive(
    api_key: web::Header<String>,
    payload: web::Payload,
) -> Result<HttpResponse, Error> {
    let key = api_key.into_inner();
    let base = format!("/data/uploads/{}/", key);
    // Unsafe: base is used without cleaning the filename from the archive
    let file_path = format!("{}{}", base, "malicious.zip");
    // ... extraction logic that does not validate paths
    Ok(HttpResponse::Ok().finish())
}

If the archive contains path traversal entries, the concatenation does not prevent writes outside /data/uploads/{key}/. This illustrates how combining Api Key usage with unsafe archive handling creates a Zip Slip vector: the key influences the path, and traversal leads to unauthorized file operations.

Additionally, if the API exposes endpoints that list or retrieve files keyed by Api Key without canonicalizing paths, an attacker can probe for traversal patterns and learn valid key formats or directory structures. The scanner checks in middleBrick’s 12 parallel security checks will flag such path traversal risks under BOLA/IDOR and Input Validation, while the LLM/AI Security probes can detect whether logs or error messages inadvertently leak Api Key material through verbose traversal errors.

To mitigate Zip Slip in Actix when using Api Keys, ensure that paths are constructed safely and that user-controlled values never directly influence filesystem locations. Always normalize and validate paths, avoid concatenating keys or user input into file paths, and store keys in environment variables or secure vaults rather than deriving paths from them.

Secure Actix example with explicit base directory and path sanitization:

use actix_web::{web, HttpResponse, Error};
use std::path::{Path, PathBuf};

/// Ensure the path is confined under a base directory
fn safe_path(base: &Path, requested: &str) -> Option<PathBuf> {
    let normalized = Path::new(requested).components().fold(PathBuf::new(), |mut acc, c| {
        if let std::path::Component::ParentDir = c {
            // Reject any attempt to traverse upward
            acc
        } else {
            acc.push(c);
            acc
        }
    });
    let full = base.join(normalized);
    if full.starts_with(base) {
        Some(full)
    } else {
        None
    }
}

async fn extract_archive_safe(
    api_key: web::Header<String>,
    payload: web::Payload,
) -> Result<HttpResponse, Error> {
    // Api Key is used for access control, not for path construction
    let key = api_key.into_inner();
    // Validate key format without using it in filesystem paths
    if !key.chars().all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_') {
        return Ok(HttpResponse::BadRequest().body("Invalid Api Key"));
    }

    // Base directory is fixed and not derived from the key
    let base = Path::new("/data/uploads");
    // Simulated uploaded filename from archive metadata (must be validated)
    let filename = "allowed.txt";

    match safe_path(base, filename) {
        Some(path) => {
            // Proceed with extraction to `path`
            Ok(HttpResponse::Ok().body(format!("Safe path: {:?}", path)))
        }
        None => Ok(HttpResponse::BadRequest().body("Invalid path")),
    }
}

Key remediation practices:

• Never derive filesystem paths from Api Keys; use keys strictly for authentication and authorization checks.
• Define a fixed base directory for uploads and use path sanitization functions that reject .. and other traversal components.
• Validate Api Key format with a strict allowlist (alphanumeric plus a few safe symbols) to reduce information leakage via error messages.
• Use middleware to enforce scope and rate limits per key, reducing the impact of a compromised key.
• Store keys in environment variables or a secrets manager and reference them via configuration, avoiding hardcoded values.

middleBrick’s scans will highlight path traversal and improper key usage findings; the Pro plan’s continuous monitoring can alert you if new endpoints introduce similar patterns, and the CI/CD integration can fail builds when unsafe path construction is detected in code changes.