Http Request Smuggling in Dynamodb

Http Request Smuggling in DynamoDB contexts typically occurs when API Gateway or Lambda functions process malformed HTTP requests that manipulate how the underlying DynamoDB service interprets request boundaries. This can lead to data corruption, unauthorized access, or service disruption.

The most common DynamoDB-specific smuggling pattern involves Content-Length header manipulation when DynamoDB SDK clients parse multipart requests. Consider an API that accepts file uploads alongside DynamoDB operations:

@app.route('/upload-and-save', methods=['POST'])
def upload_and_save():
    # Malicious Content-Length header can smuggle requests
    content_length = int(request.headers.get('Content-Length', 0))
    file_data = request.files['data'].read()  # Reads based on Content-Length
    
    # DynamoDB operation using potentially corrupted data
    dynamodb = boto3.resource('dynamodb')
    table = dynamodb.Table('UserData')
    table.put_item(
        Item={
            'id': request.form['user_id'],
            'file_content': file_data.decode('utf-8')
        }
    )
    return 'Success'

The vulnerability arises when Content-Length and Transfer-Encoding headers conflict. An attacker might send:

POST /upload-and-save HTTP/1.1
Host: api.example.com
Content-Length: 100
Transfer-Encoding: chunked

0

POST /malicious HTTP/1.1
Host: api.example.com
Content-Length: 50

Malicious payload...

DynamoDB's HTTP client in the AWS SDK may process the first chunk correctly but then continue processing the smuggled request, leading to unexpected database operations or data corruption.

Another DynamoDB-specific pattern occurs with batch operations. The BatchWriteItem API accepts multiple write operations in a single request. If an API endpoint doesn't properly validate request boundaries, an attacker could smuggle additional batch operations:

@app.route('/batch-write', methods=['POST'])
def batch_write():
    data = request.get_json()
    dynamodb = boto3.resource('dynamodb')
    table = dynamodb.Table('Orders')
    
    # No validation of request structure or size
    response = table.batch_write_item(RequestItems=data)
    return jsonify(response)

An attacker could exploit this by crafting a request where the Content-Length header indicates fewer bytes than actually sent, causing the DynamoDB client to process multiple logical requests as one, potentially overwriting data or executing unauthorized operations.

Detecting HTTP Request Smuggling in DynamoDB contexts requires examining both the API layer and the DynamoDB-specific request patterns. middleBrick's black-box scanning approach identifies these vulnerabilities without requiring credentials or code access.

middleBrick tests for DynamoDB-specific smuggling by sending malformed requests that target the AWS SDK's HTTP client behavior. The scanner sends requests with conflicting Content-Length and Transfer-Encoding headers to DynamoDB-backed endpoints, then analyzes the responses for signs of smuggling:

{