Api Scraping in Axum (Rust)

Api scraping in Axum with Rust typically refers to the extraction of data from third‑party HTTP APIs by a Rust service built on the Axum web framework. While Axum provides a robust, async runtime for handling HTTP requests, the act of scraping external APIs introduces a distinct attack surface that can lead to security issues such as SSRF, insecure data exposure, and injection of malicious payloads. Because Axum routes are often thin wrappers around HTTP client calls, developers may inadvertently forward user input directly into outbound requests without proper validation, enabling path traversal or host‑based attacks.

Consider an endpoint that accepts a URL parameter intended to specify which resource to fetch from an external service. If the parameter is used without validation in a reqwest or surf call, an attacker can supply internal addresses, cloud metadata endpoints (e.g., http://169.254.169.254), or sensitive services that are not routable from the public internet. This pattern maps directly to SSRF and can also facilitate data exposure when the scraped response contains sensitive information that is then returned to the client without filtering. In addition, scraped responses might include executable code or PII, and without output scanning or schema validation, the Axum handler can propagate that content to downstream consumers, violating data exposure and input validation controls.

The risk is compounded when the scraping logic is coupled with authentication mechanisms or when tokens are passed through query parameters or headers derived from user input. BOLA/IDOR can occur if the identifier used to select a target API endpoint is predictable or improperly scoped, allowing one user to access another’s data by manipulating the scraped resource identifier. Because Axum does not enforce boundaries between user context and outbound calls, these vulnerabilities must be mitigated at the application layer through strict input validation, schema enforcement, and separation of trusted configuration from user-supplied data.

Remediation centers on strict input validation, schema enforcement, and isolating outbound HTTP calls from user-controlled data. In Axum, define a dedicated configuration layer for allowed hosts and paths, and use typed extractors to enforce constraints before constructing outbound requests. Never directly forward query parameters or path segments to external URLs; instead, map them to a controlled set of resources or use an allowlist approach.

Example of a vulnerable Axum handler that accepts a raw URL:

use axum::{routing::get, Router};
use reqwest::Client;
use std::net::SocketAddr;

async fn scrape_raw(url: String) -> Result {
    let client = Client::new();
    client.get(&url).send().await?.text().await
}

async fn handler(url: axum::extract::Query>) -> String {
    scrape_raw(url.0.get("url").cloned().unwrap_or_default()).await.unwrap_or_default()
}

#[tokio::main]
async fn main() {
    let app = Router::new().route("/scrape", get(handler));
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr).serve(app.into_make_service()).await.unwrap();
}

This pattern is unsafe because the url parameter is used without validation, enabling SSRF and data exposure. A secure version validates the target against an allowlist, normalizes the path, and enforces timeouts and response size limits.

Secure handler with validation and controlled scraping:

use axum::{routing::get, Router, extract::Query};
use reqwest::Client;
use std::collections::HashSet;
use std::net::SocketAddr;

async fn scrape_safe(Query(params): Query>) -> Result {
    let allowed_hosts: HashSet<&str> = ["api.example.com", "data.example.org"].iter().copied().collect();
    let base = params.get("resource").ok_or((axum::http::StatusCode::BAD_REQUEST, "missing resource".to_string()))?;
    if !allowed_hosts.contains(base.as_str()) {
        return Err((axum::http::StatusCode::FORBIDDEN, "host not allowed".to_string()));
    }
    let url = format!("https://{}/v1/{}", base, params.get("path").unwrap_or(&"data".to_string()));
    let client = Client::new();
    let response = client.get(&url)
        .timeout(std::time::Duration::from_secs(5))
        .send()
        .await
        .map_err(|e| (axum::http::StatusCode::BAD_GATEWAY, e.to_string()))?
        .text()
        .await
        .map_err(|e| (axum::http::StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
    // Apply schema validation and PII filtering here before returning
    Ok(response)
}

async fn handler() -> String {
    // Placeholder for route wiring
    "Secure handler configured".to_string()
}

#[tokio::main]
async fn main() {
    let app = Router::new()
        .route("/scrape", get(scrape_safe));
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    axum::Server::bind(&addr).serve(app.into_make_service()).await.unwrap();
}

This approach ensures that only predefined hosts are scraped, paths are constrained, and timeouts prevent hanging requests. Complement this with schema validation (e.g., using serde and validator) and output scanning to detect PII or secrets before returning data to the client. For continuous assurance in development and deployment, use the middleBrick CLI (middlebrick scan <url>) or integrate the GitHub Action to fail builds if security scores drop below your threshold, and leverage the MCP Server to scan APIs directly from your AI coding assistant during implementation.