Buffer Overflow in Rocket with Basic Auth

A buffer overflow occurs when a program writes more data to a fixed-length buffer than it can hold, corrupting adjacent memory. In Rocket, this risk can surface in request-handling logic even when Basic Authentication is used. Basic Auth transmits credentials as a base64-encoded string in the Authorization header; while base64 encoding itself does not prevent overflows, the way headers and parsed values are handled in Rocket routes can expose vulnerabilities if input is not strictly bounded.

Consider a Rocket route that extracts a user-supplied header or query parameter and copies it into a fixed-size stack buffer via FFI or unsafe code. An attacker can send a long string in the Authorization header value (after the Basic prefix) or in another header that the route processes, triggering a buffer overflow. This may lead to memory corruption, arbitrary code execution, or information disclosure. Because the scan tests unauthenticated attack surfaces, a buffer overflow in an endpoint protected by Basic Auth can still be detected: the scanner sends long, malformed, or unexpected payloads in the Authorization header and observes behavior such as crashes or unexpected responses.

One concrete pattern: a Rocket route that manually decodes Basic Auth and passes the password to an unchecked C function. For example, if the password is used in a strcpy without length checks, a long password can overflow the destination buffer. The scanner’s checks include Input Validation and Unsafe Consumption, which flag missing bounds checking when handling header-derived data. Even though Basic Auth is a transport-layer convenience, application-layer code must treat its decoded components as untrusted input.

Real-world analogies include CVEs where improper parsing of headers led to memory corruption. The scanner’s 12 parallel checks help identify such issues by correlating spec definitions (e.g., OpenAPI/Swagger with full $ref resolution) with runtime behavior, ensuring that endpoints using Basic Auth are not inadvertently exposing overflow-prone parsing logic.

To mitigate buffer overflow risks in Rocket when using Basic Authentication, always validate and bound the length of decoded credentials before using them in low-level operations. Prefer safe Rust abstractions over unchecked FFI or manual decoding. Below are concrete, safe patterns for handling Basic Auth in Rocket routes.

Safe Basic Auth parsing with length checks

Use Rocket's built-in guards and types to handle authorization safely. Decode the header and enforce size limits before any further processing.

use rocket::http::Status;
use rocket::request::{self, FromRequest, Request};
use rocket::{Outcome, Request};

struct AuthenticatedUser {
    username: String,
    // Do not store passwords longer than a safe bound
    password_hash: String,
}

#[rocket::async_trait]
impl<'r> FromRequest<'r> for AuthenticatedUser {
    type Error = ();

    async fn from_request(request: &'r Request<'_>) -> request::Outcome<AuthenticatedUser, ()> {
        let header = request.headers().get_one("authorization");
        let header = match header {
            Some(h) => h,
            None => return Outcome::Failure((Status::Unauthorized, ())),
        };
        if !header.starts_with("Basic ") {
            return Outcome::Failure((Status::Unauthorized, ()));
        }
        let encoded = header.trim_start_matches("Basic ");
        // Decode with bounds: reject overly long credentials
        let decoded = match base64::decode(encoded) {
            Ok(d) if d.len() <= 512 => d,
            _ => return Outcome::Failure((Status::Unauthorized, ())),
        };
        let parts: Vec<&str> = std::str::from_utf8(&decoded)
            .map_err(|_| ())
            .and_then(|s| {
                let mut parts = s.splitn(2, ':');
                let user = parts.next().ok_or(())?;
                let pass = parts.next().ok_or(())?;
                Ok((user, pass))
            })
            .map_err(|_| ())?;

        // Enforce per-part length limits to prevent overflow downstream
        if parts.0.len() > 128 || parts.1.len() > 128 {
            return Outcome::Failure((Status::Unauthorized, ()));
        }

        // Here you would verify the hash; avoid using raw passwords in memory
        Outcome::Success(AuthenticatedUser {
            username: parts.0.to_string(),
            password_hash: hash_password(parts.1),
        })
    }
}

fn hash_password(pass: &str) -> String {
    // Use a proper password hasher, e.g., argon2
    pass.to_string()
}

#[get("/profile")]
async fn profile(user: AuthenticatedUser) -> String {
    format!("Welcome, {}", user.username)
}

use std::convert::TryInto;

// Safe copy with length validation
let password_bytes = parts.1.as_bytes();
let mut fixed_buffer: [u8; 64] = [0; 64];
if password_bytes.len() <= fixed_buffer.len() {
    fixed_buffer[..password_bytes.len()].copy_from_slice(password_bytes);
    // Call native function with the bounded buffer
    // unsafe { native_process(fixed_buffer.as_ptr(), fixed_buffer.len()) };
} else {
    // Handle error: credential too long
}