Xpath Injection in Actix with Cockroachdb

XPath Injection occurs when user input is concatenated into an XPath expression without proper sanitization or parameterization, leading to unauthorized data access or bypass of access controls. In an Actix-web service that uses CockroachDB as the backend, this typically manifests when building dynamic XPath queries in Rust code, often via string formatting or concatenation before sending them to the database.

Actix-web does not inherently introduce XPath risks; the concern arises when application logic builds XPath strings using unchecked user input. CockroachDB supports XPath-like queries for XML data types, and if those queries are constructed insecurely, attackers can manipulate the structure of the XPath to access or modify unintended data. For example, an attacker might supply a payload such as ' or '1'='1 or escape the intended context to read other user records.

Consider a scenario where an endpoint accepts a user identifier to fetch profile data using an XPath expression. If the identifier is interpolated into the query string, an attacker could provide something like admin' or 1=1--, potentially altering the predicate logic. Because the scan testing is unauthenticated, middleBrick can detect input validation weaknesses and insecure query construction by observing deviations in response behavior across crafted probes.

Additionally, in an Actix service, asynchronous handlers may pass raw strings to database drivers that forward them to CockroachDB. Without strict input validation and separation of data from command logic, the XPath becomes vulnerable. The database then evaluates the malicious expression, returning more data than intended or exposing administrative views. This aligns with the BOLA/IDOR and Input Validation checks in middleBrick’s 12 parallel security tests, which look for unsafe data handling patterns that could lead to privilege escalation or data exposure.

Real-world impact includes unauthorized account enumeration or data leakage. Using middleBrick’s OpenAPI/Swagger analysis, the scanner cross-references endpoint definitions with runtime behavior to identify discrepancies, such as missing constraints on path or query parameters that would allow injection attempts. The tool’s input validation checks specifically target these patterns in APIs that interact with XML or structured query backends like CockroachDB.

To mitigate XPath Injection in Actix with CockroachDB, avoid string interpolation for query construction. Instead, use strongly typed queries or prepared statements where possible, and rigorously validate and sanitize all inputs. Below are concrete patterns to follow.

1. Validate and sanitize input

Ensure that any user-supplied data used in XPath-like predicates is validated against a strict allowlist. For identifiers, use regex patterns that permit only alphanumeric characters.

use actix_web::{web, HttpResponse};
use regex::Regex;

fn is_valid_user_id(user_id: &str) -> bool {
    let re = Regex::new(r"^[a-zA-Z0-9_-]{3,32}$").unwrap();
    re.is_match(user_id)
}

async fn get_user_profile(user_id: web::Path<String>) -> HttpResponse {
    if !is_valid_user_id(&user_id) {
        return HttpResponse::BadRequest().body("Invalid user identifier");
    }
    // Proceed with safe query logic
    HttpResponse::Ok().body(format!("Profile for {}", user_id))
}

2. Use parameterized queries or ORM patterns

While CockroachDB does not have native XPath support in its SQL layer, if you are using XML data types and XPath functions, pass values through placeholders or construct queries using safe formatting libraries. Below is an example using sqlx with positional parameters to avoid injection.

use actix_web::web;
use sqlx::postgres::PgPool;

async fn fetch_user_safe(pool: web::Data<PgPool>, user_id: String) -> Result<(), sqlx::Error> {
    // Use parameterized query to avoid injection
    let row: (String,) = sqlx::query_as(
        "SELECT email FROM users WHERE id = $1"
    )
    .bind(&user_id)
    .fetch_one(pool.as_ref())
    .await?;
    // Process row
    Ok(())
}

3. Encode and limit data exposure

If you must construct XML or XPath-like expressions, encode values and restrict the depth of traversal. For example, use base64 encoding for arbitrary strings and limit the XPath context to known-safe nodes.

use base64::encode;

let safe_token = encode(&user_input);
let xpath_expr = format!("/profile/field[@token='{}']", safe_token);
// Use xpath_expr in a controlled context with length checks
if xpath_expr.len() > 256 {
    return Err("Expression too long");
}

4. Apply principle of least privilege

Ensure the database role used by Actix has minimal permissions. In CockroachDB, define a role that can only read necessary tables and cannot execute administrative or metadata queries that might be leveraged via injection.

-- CockroachDB SQL example
CREATE USER web_reader WITH PASSWORD 'secure_password';
GRANT SELECT ON TABLE users TO web_reader;
REVOKE ALL ON DATABASE company FROM web_reader;

5. Monitor and test

Use middleBrick’s CLI to scan your endpoints regularly. The tool’s Input Validation and BOLA/IDOR checks will highlight endpoints where user data reaches query logic without sufficient sanitization. Incorporate the GitHub Action to fail builds if a scan detects high-severity findings related to injection risks.