Hallucination Attacks in Axum with Cockroachdb

In an Axum application that uses CockroachDB, a hallucination attack can occur when a language model or an AI-based assistant generates SQL queries or API parameters that do not correspond to any real user intent or valid data access pattern. Because Axum is a Rust web framework that typically deserializes request payloads into strongly typed structures, mismatched or invented field names may be silently accepted if runtime validation is incomplete. When these unvalidated inputs are forwarded to CockroachDB, which relies on strict SQL semantics and schema-defined tables, the system may produce plausible but incorrect query results or errors that an attacker can interpret.

For example, an attacker might supply crafted JSON such as { "user_id": "1", "report_type": "financial_summary", "extra_column": "1=1; SELECT * FROM pg_stat_statements" }. If Axum passes this to CockroachDB via a dynamic query builder or an ORM that interpolates fields without strict schema checks, the injected SQL fragments can cause the database to return unintended rows or metadata. Because CockroachDB supports PostgreSQL wire protocol, typical SQL injection techniques can be adapted to exploit lax input validation in Axum handlers, leading to data exposure or unauthorized inference of schema details.

The risk is amplified when Axum endpoints expose database error messages directly to clients, as these messages may reveal table names, column definitions, or execution plans that do not exist in the attacker’s knowledge base—effectively a hallucination vector where the system fabricates or misrepresents data relationships. Without schema-aware validation and strict type binding, the combination of Axum’s flexibility and CockroachDB’s SQL expressiveness creates a surface where attackers can probe for inconsistencies and induce the service to generate incorrect or hallucinated responses that leak information or bypass intended access controls.

Remediation focuses on strict schema enforcement, typed query interfaces, and eliminating dynamic SQL construction in Axum handlers. Use CockroachDB’s supported PostgreSQL interface with prepared statements and strongly typed parameters to ensure that user input never directly alters query structure.

// Example: Axum handler with typed SQL via `sqlx` and CockroachDB
use axum::{routing::post, Json, Router};
use serde::Deserialize;
use sqlx::postgres::PgPoolOptions;
use sqlx::FromRow;

#[derive(Deserialize)]
struct ReportRequest {
    user_id: i64,
    report_type: String,
}

#[derive(FromRow)]
struct ReportRow {
    id: i64,
    summary: String,
}

async fn generate_report(
    Json(payload): Json,
    pool: &axum::extract::State,
) -> Result, (axum::http::StatusCode, String)> {
    let record = sqlx::query_as::<_, ReportRow>(
        "SELECT id, summary FROM reports WHERE user_id = $1 AND report_type = $2",
    )
    .bind(payload.user_id)
    .bind(payload.report_type)
    .fetch_one(pool.as_ref())
    .await
    .map_err(|e| (axum::http::StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
    Ok(Json(record))
}

fn app() -> Router {
    let pool = PgPoolOptions::new()
        .connect("postgresql://user:pass@localhost:26257/dbname?sslmode=disable")
        .await
        .expect("failed to create pool");
    Router::new()
        .route("/report", post(generate_report))
        .with_state(pool)
}

This pattern ensures that user_id and report_type are passed as parameters, preventing SQL injection and eliminating hallucination opportunities where an attacker could inject column names or SQL fragments. Additionally, enforce strict schema validation at the Axum layer by rejecting unknown fields during deserialization:

// Reject extra fields to prevent hallucination-based parameter tampering
use serde::de::DeserializeOwned;
use axum::extract::Json;

fn strict_json(req: Json) -> Json {
    // serde will reject unknown fields if #[serde(deny_unknown_fields)] is set on T
    req
}

#[derive(Deserialize)]
#[serde(deny_unknown_fields)]
struct StrictReportRequest {
    user_id: i64,
    report_type: String,
}

async fn strict_handler(Json(payload): Json) -> String {
    format!("Processing {} for user {}", payload.report_type, payload.user_id)
}

For CockroachDB-specific hardening, avoid constructing table or column names from user input. If dynamic queries are unavoidable, use a strict allowlist for identifiers and employ CockroachDB’s format_name quoting via sqlx::postgres::PgArguments or equivalent safe identifier handling. Combine these practices with Axum’s extractor validation to ensure that only expected, schema-compliant requests reach the database, thereby neutralizing hallucination attack vectors that rely on malformed or inventive input.