Cryptographic Failures in Rocket with Dynamodb

Cryptographic failures occur when sensitive data is not adequately protected at rest or in transit. In a Rocket application that uses Amazon DynamoDB as its persistence layer, the combination of an asynchronous, schema-less database and Rocket's request handling can inadvertently expose secrets or weaken encryption guarantees if developers assume the ORM or the database will enforce security automatically.

DynamoDB does not by itself encrypt data using customer-managed keys unless explicitly configured; default encryption at rest is AWS-managed. In Rocket, if a route handler deserializes a DynamoDB record into a struct and passes it to a template or API response without verifying which fields should be encrypted, credentials or personal information may be transmitted in clear text. For example, storing a user password as a plain string in a DynamoDB item and then returning it (even accidentally via a debug endpoint) is a cryptographic failure under OWASP API Security Top 10:2023 — Cryptographic Failures.

Additionally, client-side encryption is often omitted in favor of server-side encryption, which means Rocket code may construct queries that filter on sensitive fields (e.g., email) without considering that those fields might be stored in plaintext if envelope encryption was not applied. A common pattern is to load an item by ID and return it directly; if the item contains secrets and the TLS termination is misconfigured or an internal proxy is compromised, the data is exposed. The DynamoDB SDK for Rust does not implicitly sign or encrypt payloads; it is the developer’s responsibility to ensure that sensitive fields are encrypted before being placed into a PutItem or UpdateItem request, and decrypted only when necessary in a secure context.

SSRF (Server-Side Request Forgery) can compound cryptographic failures: an attacker able to coerce Rocket into making requests to internal AWS metadata services might discover IAM credentials attached to the DynamoDB role, further undermining encryption boundaries. Proper input validation and separation of sensitive operations mitigate this class of risk.

Remediation focuses on ensuring sensitive fields are encrypted before they ever reach DynamoDB and are only decrypted in controlled contexts. Use envelope encryption with AWS KMS keys to protect data at rest, and enforce field-level encryption for secrets such as passwords, API keys, and PII.

Below is a syntactically correct example using the official AWS SDK for Rust and Rocket. It demonstrates encrypting a sensitive field before storage and decrypting it only when necessary, using KMS GenerateDataKey.

use aws_sdk_dynamodb::{Client, types::AttributeValue};
use aws_sdk_kms::Client as KmsClient;
use rocket::serde::json::Json;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
struct User {
    id: String,
    email: String,
    // Do not store plain secrets in struct fields that map directly to responses
    password_hash: String,
}

async fn store_user(
    ddb: &Client,
    kms: &KmsClient,
    user: User,
) -> Result<(), Box> {
    // Generate a data key from KMS
    let key_resp = kms.generate_data_key()
        .key_id("alias/rocket-app-key")
        .send()
        .await?;
    let plaintext_key = key_resp.plaintext().ok_or("Missing plaintext key")?;
    let ciphertext_key = key_resp.ciphertext_blob().to_vec();

    // Encrypt the sensitive field (password_hash) using the plaintext key
    // In production, use an authenticated encryption scheme like AES-GCM
    let encrypted_password = encrypt_aes_gcm(plaintext_key, user.password_hash.as_bytes())?;

    let mut item = std::collections::HashMap::new();
    item.insert("id".to_string(), AttributeValue::S(user.id));
    item.insert("email".to_string(), AttributeValue::S(user.email));
    item.insert("password_hash".to_string(), AttributeValue::B(encrypted_password.into()));
    item.insert("kms_key_blob".to_string(), AttributeValue::B(ciphertext_key.into()));

    ddb.put_item()
        .table_name("users")
        .set_item(Some(item))
        .send()
        .await?;
    Ok(())
}

async fn get_user(
    ddb: &Client,
    kms: &KmsClient,
    user_id: &str,
) -> Result> {
    let resp = ddb.get_item()
        .table_name("users")
        .key("id", AttributeValue::S(user_id.to_string()))
        .send()
        .await?;

    let item = resp.item().ok_or("Item not found")?;
    let enc_password = match item.get("password_hash") {
        Some(AttributeValue::B(b)) => b.to_vec(),
        _ => return Err("Missing password hash".into()),
    };
    let key_blob = match item.get("kms_key_blob") {
        Some(AttributeValue::B(b)) => b.to_vec(),
        _ => return Err("Missing KMS key blob".into()),
    };

    // Decrypt the data key using KMS (simplified; in practice use Decrypt)
    // For brevity, assume we have the plaintext key; in real code call kms.decrypt
    let plaintext_key = decrypt_kms_key(&key_blob)?; // Placeholder
    let password_hash = decrypt_aes_gcm(plaintext_key, &enc_password)?;

    Ok(User {
        id: user_id.to_string(),
        email: item.get("email").and_then(|v| v.as_s().ok()).unwrap_or("").to_string(),
        password_hash,
    })
}

// Placeholder crypto functions — use a vetted crate like `aes-gcm` in production
fn encrypt_aes_gcm(key: &[u8], data: &[u8]) -> Result, Box> { Ok(data.to_vec()) }
fn decrypt_aes_gcm(key: &[u8], data: &[u8]) -> Result> { Ok(String::from_utf8(data.to_vec())) }
fn decrypt_kms_key(blob: &[u8]) -> Result, Box> { Ok(blob.to_vec()) }

Additional remediation steps include using Rocket's managed state to hold KMS clients safely, validating input IDs to prevent IDOR when querying DynamoDB, and enabling DynamoDB encryption at rest with customer-managed keys where compliance requires it. Combine these practices with the middleBrick CLI (middlebrick scan <url>) or GitHub Action to detect missing encryption in API endpoints during CI/CD, and consider the Pro plan for continuous monitoring to catch regressions before deployment.