Question 71890 in Amazon Web Sevices Question posted in
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AWS DynamoDB user authorization – Amazon web services

currently I am working with AWS DynamoDB and I struggle with user authorization and restricting access to specific items inside of a DynamoDB Table.
I have already read the documentation and came across multiple blog posts, but unfortunately I haven’t found my use case yet.

Some background information:

Each user of the web app belongs to a company and each company has multiple orders. These orders are inside of the DynamoDB table "Orders". What I want to achieve is that the users can only read order items from the company they belong to.

My Approach

My idea was to create the "Orders" table with a partition key of "companyId" and a sort key of "orderId". During my research I figured out that I can restrict the access through IAM Policy roles, but I couldn’t find a way to access the companyId of the user inside of the policy role. Users are authenticating through AWS Cognito.

My Question

How can I restrict the user access specific items inside of a DynamoDB? Taking into account the each user belongs to a company and should only see orders of this company.

Looking forward to some help!

Tags:

2

Answers


  1. 0

    Using custom attributes, you can create a backend layer that will check these parameters, query DynamoDB with the specified attribute, and return them – https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-settings-attributes.html

    The second option is to set up role for each company – https://docs.aws.amazon.com/cognito/latest/developerguide/role-based-access-control.html#using-rules-to-assign-roles-to-users

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  2. 0

    AWS has published Isolating SaaS Tenants with Dynamically Generated IAM Policies blog on their website. This blog explains exactly the thing that you want to achieve.

    In short, I can explain:

    1. Use CustomerId as PartitionKey

    2. Create an IAM policy with access on Orders table like below

      1 {
2  "Version": "2012-10-17",
3  "Statement": [
4    {
5      "Action": [
6        "dynamodb:GetItem",
7        "dynamodb:BatchGetItem",
8        "dynamodb:Query",
9        "dynamodb:DescribeTable"
10      ],
11      "Resource": "arn:aws:dynamodb:us-west-2:123456789012:table/Orders",
12      "Effect": "Allow"
13    }
14  ]
15 }

    3. Create a template for Session Policy where you will replace CustomerId with incoming request’s customerId on runtime.

      1  {
2    "Effect": "Allow",
3    "Action": [
4         "dynamodb:*"
5    ],
6    "Resource": [
7         "arn:aws:dynamodb:*:*:table/{{table}}"
8    ],
9    "Condition": {
10        "ForAllValues:StringEquals": {
11            "dynamodb: LeadingKeys": [ "{{customerId}}" ]
12        }
13    }
14 }

    4. Now, invoke STS (Security Token Service) with above IAM & Session policy to get temporary credentials that has access limited to a single tenant/customer data.

      Below is the pseudo code, you can use your programming language’s SDK to write below code.

      AssumeRoleResponse response = sts.assumeRole (ar -> ar
     .webIdentityToken(openIdToken)
     .policy(scopedPolicy)
     .roleArn(role));
Credentials tenantCredentials = response.credentials();
DynamoDbClient dynamoDbClient = DynamoDbClient.builder()
     .credentialsProvider(tenantCredentials)
     .build();

    5. Finally, create DynamoDBClient object using these temporary credentials and use it. This object of DynamoDBClient will have access to only current user’s customer data.

    Hope this should help!

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