Privilege Escalation in Echo Go with Dynamodb

Privilege escalation in the context of an Echo Go service that uses DynamoDB typically occurs when authorization checks are incomplete or when IAM policies attached to the service role are over-permissive. Because Echo Go handles HTTP routing and request lifecycle, developers often focus on routing logic and may inadvertently allow an authenticated subject to influence which DynamoDB operations are executed. If the application derives a DynamoDB key (such as a partition key or sort key) directly from user-supplied input without strict validation or context checks, an attacker can manipulate that input to access or modify items they should not own.

DynamoDB does not perform application-level ownership checks; it enforces permissions strictly based on the IAM policy attached to the credentials used by the client. In Echo Go, if the server assumes the caller is authorized after a simple JWT validation and then calls DynamoDB with a key derived from request parameters, the IAM policy used by the service may allow broader actions than intended. For example, an endpoint like /users/{userID}/settings might construct a DynamoDB key as userID = requestParam("userID"). Without verifying that the authenticated subject matches the requested userID, an attacker can enumerate or modify any user’s settings. This is a BOLA/IDOR pattern enabled by weak mapping between application identity and DynamoDB key design.

Additionally, privilege escalation can arise from missing property-level authorization before invoking DynamoDB operations. Echo Go may call UpdateItem with an update expression that modifies fields based on user input. If the application does not validate which fields can be updated by the current role, an attacker can supply fields intended for privileged attributes (such as role or admin) and have them persisted. Because DynamoDB only sees the final request, the service must enforce property authorization before constructing update expressions. Lack of rate limiting or inadequate per-endpoint authorization in Echo Go can also amplify the impact by enabling automated attempts to escalate via crafted requests.

These issues are detectable by middleBrick’s BOLA/IDOR and BFLA/Privilege Escalation checks, which correlate runtime behavior with the OpenAPI specification and observed IAM-friendly patterns. When a scan targets an Echo Go endpoint backed by DynamoDB, it can identify endpoints where user-controlled input directly shapes DynamoDB keys or update expressions without proper authorization. Remediation focuses on strict mapping between authenticated identity and DynamoDB keys, and on validating each field against the caller’s role before any DynamoDB operation.

Remediation for privilege escalation in Echo Go with DynamoDB centers on ensuring that every DynamoDB operation is constrained by the authenticated identity and validated against a strict allowlist of updatable fields. Below are concrete, idiomatic Go examples that demonstrate secure patterns.

1. Enforce ownership by deriving the DynamoDB key from authenticated claims, not request parameters

// Good: key derived from authenticated subject, not user-supplied path param
func getUserSettings(c echo.Context) error {
    subject := c.Get("user").(*models.User) // authenticated subject from JWT
    tableName := "UserSettings"
    key := map[string]*dynamodb.AttributeValue{
        "PK": {S: aws.String(fmt.Sprintf("USER#%s", subject.ID))},
    }
    out, err := svc.GetItem(context.TODO(), &dynamodb.GetItemInput{
        TableName: aws.String(tableName),
        Key:       key,
    })
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    if out.Item == nil {
        return echo.NewHTTPError(http.StatusNotFound)
    }
    return c.JSON(out.Item)
}

// Bad: uses request param directly, enabling horizontal escalation
// func badGetUserSettings(c echo.Context) error {
//     userID := c.Param("userID") // attacker-controlled
//     key := map[string]*dynamodb.AttributeValue{
//         "PK": {S: aws.String("USER#" + userID)},
//     }
//     out, _ := svc.GetItem(...)
//     ...
// }

2. Use condition expressions and pre-checks for property-level authorization

// Good: validate allowed fields before constructing update expression
func updateUserSettings(c echo.Context) error {
    subject := c.Get("user").(*models.User)
    var payload map[string]interface{}
    if err := c.Bind(&payload); err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, err.Error())
    }

    // Explicit allowlist for this endpoint
    allowed := map[string]bool{"theme": true, "notificationsEnabled": true}
    for k := range payload {
        if !allowed[k] {
            return echo.NewHTTPError(http.StatusBadRequest, "field not allowed")
        }
    }

    // Build update expression safely
    var setParts []string
    exprAttrVals := make(map[string]*dynamodb.AttributeValue)
    for k, v := range payload {
        setParts = append(setParts, fmt.Sprintf("#f = :val%d", k))
        exprAttrVals[fmt.Sprintf(":val%d", k)] = &dynamodb.AttributeValue{S: aws.String(fmt.Sprintf("%v", v))}
    }

    pk := fmt.Sprintf("USER#%s", subject.ID)
    update := fmt.Sprintf("SET %s", strings.Join(setParts, ", "))
    condition := "attribute_exists(PK)"

    _, err := svc.UpdateItem(context.TODO(), &dynamodb.UpdateItemInput{
        TableName:                 aws.String("UserSettings"),
        Key:                       map[string]*dynamodb.AttributeValue{"PK": {S: aws.String(pk)}},
        UpdateExpression:          aws.String(update),
        ExpressionAttributeNames:  map[string]string{"#f": "settings"},
        ExpressionAttributeValues: exprAttrVals,
        ConditionExpression:       aws.String(condition),
    })
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    return c.NoContent(http.StatusNoContent)
}

3. Apply least-privilege IAM policies scoped to the authenticated subject

While not Go code, ensure the service role used by Echo Go has a policy that restricts DynamoDB actions by the partition key prefix derived from the authenticated subject. For example, a policy condition like dynamodb:LeadingKeys can enforce that requests only affect items where the partition key begins with USER#<subject_id>. This prevents an compromised token from being used to target other users’ items even if request validation is bypassed.

By combining subject-derived keys, strict allowlists, and condition expressions, Echo Go applications can mitigate privilege escalation risks when interacting with DynamoDB.