Log Injection in Actix with Dynamodb

Log injection occurs when untrusted input is written directly into application or system logs without proper sanitization. In an Actix-web service that uses Amazon DynamoDB as a persistence layer, the combination of structured logging expectations and DynamoDB’s flexible attribute storage can inadvertently amplify injection risks.

Consider an Actix handler that stores user-supplied data in DynamoDB and then logs the operation. If the input contains newline characters or structured delimiter sequences (e.g., \n, |, or JSON-like fragments), and those values are later echoed into log entries without escaping, attackers can forge log lines. For example, a malicious payload like foo\n"level":"ERROR" appended to a log message can create the appearance of a false log level or inject misleading context.

DynamoDB stores attributes as name–value pairs, where values can be strings, numbers, or binary data. When an application logs a DynamoDB item directly by serializing attributes (e.g., using serde_json::to_string) and then writing that serialized string into a log line, newline or control characters embedded in string attributes can break log structure. This can complicate log parsing and enable log forging, where an attacker’s input influences what operators or automated systems see in monitoring dashboards.

In practice, the risk is not that DynamoDB executes injected log content, but that the data retrieved from DynamoDB is used verbatim in logs. For instance, if a field such as username contains a newline and the logging code does not sanitize it, a single log entry may span multiple lines, making correlation and analysis error-prone. This can obscure genuine events and reduce trust in log-based incident response.

Because middleBrick tests unauthenticated attack surfaces and includes input validation checks, it can flag scenarios where user-controlled data reaches logging paths without canonicalization. Remediation focuses on ensuring that log output is deterministic and structured, and that data from DynamoDB is sanitized before inclusion in log messages.

To mitigate log injection when integrating Actix with DynamoDB, treat all data retrieved from or destined for DynamoDB as potentially untrusted. Apply canonicalization and structured logging so that newlines and other control characters do not affect log integrity.

Below is a realistic Actix handler that retrieves an item from DynamoDB and logs the operation safely. It uses the official AWS SDK for Rust (aws-sdk-dynamodb) and avoids including raw attribute values in logs.

use actix_web::{web, HttpResponse};
use aws_sdk_dynamodb::Client;
use log::{info, warn};

/// Sanitize a string by replacing newlines and other control characters.
fn sanitize_log_value(value: &str) -> String {
    value.replace(['\n', '\r', '\t'], "_")
}

async fn get_item(client: web::Data<Client>, key: web::Path<String>) -> HttpResponse {
    let table_name = "MyTable";
    let key_value = key.into_inner();

    let output = client
        .get_item()
        .table_name(table_name)
        .key("id", aws_sdk_dynamodb::types::AttributeValue::S(key_value.clone()))
        .send()
        .await;

    match output {
        Ok(response) => {
            if let Some(item) = response.item {
                // Extract only the fields you need for logging, and sanitize them.
                let id = sanitize_log_value(
                    item.get("id")
                        .and_then(|v| v.as_s().ok())
                        .unwrap_or(&key_value),
                );
                let status = item
                    .get("status")
                    .and_then(|v| v.as_s().ok())
                    .map(|s| sanitize_log_value(s));

                info!("Retrieved item id={} status={:?}", id, status);
                HttpResponse::Ok().json(item)
            } else {
                warn!("Item not found for id={}", sanitize_log_value(&key_value));
                HttpResponse::NotFound().finish()
            }
        }
        Err(err) => {
            // Log the error without including raw user input.
            warn!("DynamoDB error retrieving id={}: {}", sanitize_log_value(&key_value), err);
            HttpResponse::InternalServerError().finish()
        }
    }
}