Bola Idor in Echo Go with Dynamodb

Broken Object Level Authorization (BOLA) occurs when an API exposes endpoints that allow an authenticated user to access or modify resources that belong to another user. In Echo Go applications that use Amazon DynamoDB as the persistence layer, this risk is amplified when authorization checks are missing or incorrectly applied at the database query level.

Consider an endpoint like /users/{userID}/profile. If the handler extracts userID from the request context but does not enforce that the requested userID matches the authenticated subject before building a DynamoDB query, an attacker can change the path parameter to another user ID and read or overwrite that profile. Because DynamoDB does not enforce application-level ownership automatically, the onus is on the service to ensure that every query includes the correct access controls.

A typical vulnerable pattern in Echo Go with DynamoDB involves constructing a query using only user-supplied input without validating ownership. For example, a handler might receive a userID path variable and directly use it as a key in a GetItem or Query operation. If the DynamoDB key schema uses a composite primary key (partition key as user ID, sort key as entity type), omitting a server-side check that the authenticated principal matches the partition key means any authenticated user can traverse other rows by changing the ID. This maps directly to the OWASP API Top 10 A1: Broken Object Level Authorization and can be discovered by middleBrick as a BOLA/IDOR finding in the scan results.

DynamoDB-specific factors that enable or surface BOLA include key schema design and the use of secondary indexes. If an index is used to support queries by non-key attributes, and the application does not include the owner identifier in the filter expression, an attacker may be able to enumerate or retrieve other users’ data. Additionally, DynamoDB conditional writes can be bypassed if the condition does not include ownership checks, allowing an attacker to overwrite another user’s record. middleBrick tests these scenarios by probing endpoints with modified identifiers and inspecting responses for unauthorized data exposure, producing findings with severity and remediation guidance mapped to compliance frameworks such as OWASP API Top 10 and SOC2.

To remediate BOLA in Echo Go with DynamoDB, ensure that every database operation includes the authenticated subject as part of the key condition and that application-level authorization is enforced before issuing requests.

• Always include the authenticated user ID as the partition key in queries and scans.
• Use conditional expressions to enforce ownership on updates and deletes.
• Avoid using user-controlled IDs directly in DynamoDB key expressions without validation.

Below are concrete, working examples using the AWS SDK for Go v2 (github.com/aws/aws-sdk-go-v2/service/dynamodb).

// Correct: include authenticated subject in the key and enforce ownership check.
func getUserProfile(ctx context.Context, svc *dynamodb.Client, userID, subjectID string) (*dynamodb.GetItemOutput, error) {
    // Ensure the requested userID matches the authenticated subject.
    if userID != subjectID {
        return nil, echo.ErrUnauthorized
    }
    out, err := svc.GetItem(ctx, &dynamodb.GetItemInput{
        TableName: aws.String("Users"),
        Key: map[string]types.AttributeValue{
            "user_id": &types.AttributeValueMemberS{Value: userID},
            "entity_type": &types.AttributeValueMemberS{Value: "profile"},
        },
    })
    if err != nil {
        return nil, err
    }
    return out, nil
}

For queries that involve a sort key, embed the authenticated subject in both the partition key and the key condition expression:

// Correct: query with ownership enforced via partition key and key condition.
func listUserItems(ctx context.Context, svc *dynamodb.Client, userID, subjectID string) (*dynamodb.QueryOutput, error) {
    if userID != subjectID {
        return nil, echo.ErrUnauthorized
    }
    out, err := svc.Query(ctx, &dynamodb.QueryInput{
        TableName: aws.String("UserItems"),
        KeyConditionExpression: aws.String("user_id = :uid"),
        ExpressionAttributeValues: map[string]types.AttributeValue{
            ":uid": &types.AttributeValueMemberS{Value: userID},
        },
    })
    if err != nil {
        return nil, err
    }
    return out, nil
}

When updates are required, use a conditional expression that includes the owner’s identifier to prevent unauthorized modifications:

// Correct: conditional write to ensure only the owner can update their profile.
func updateUserProfile(ctx context.Context, svc *dynamodb.Client, userID string, input map[string]types.AttributeValue, expectedVersion int64) error {
    if userID != subjectID {
        return echo.ErrUnauthorized
    }
    _, err := svc.UpdateItem(ctx, &dynamodb.UpdateItemInput{
        TableName: aws.String("Users"),
        Key: map[string]types.AttributeValue{
            "user_id": &types.AttributeValueMemberS{Value: userID},
        },
        UpdateExpression: aws.String("set display_name = :name, version = version + :inc"),
        ConditionExpression: aws.String("attribute_exists(user_id) AND version = :version"),
        ExpressionAttributeValues: map[string]types.AttributeValue{
            ":name": &types.AttributeValueMemberS{Value: input["display_name"]},
            ":inc":  &types.AttributeValueMemberN{Value: "1"},
            ":version": &types.AttributeValueMemberN{Value: strconv.FormatInt(expectedVersion, 10)},
        },
    })
    return err
}

By embedding ownership checks in application logic and ensuring DynamoDB key structures and conditions reflect the authenticated subject, you mitigate BOLA while preserving the benefits of DynamoDB’s scalability. middleBrick can validate these patterns by scanning the API endpoints and confirming that BOLA/IDOR findings are cleared, providing prioritized remediation guidance aligned with best practices.