Unicode Normalization in Echo Go with Dynamodb

Unicode normalization inconsistencies between an HTTP framework and a database can create authorization bypass and data exposure risks. In Echo Go, if route parameters or JSON payloads accept user-controlled strings and are passed to DynamoDB without normalization, equivalent characters can map to different keys. For example, the Latin small letter "a" with combining acute accent (á, U+00E1) can be represented as a single code point or as "a" + combining acute (U+0061 + U+0301). If DynamoDB stores the normalized form but Echo Go passes the raw, unnormalized input to construct keys or query conditions, attackers can bypass ownership checks or access unintended items.

Consider an endpoint like /widgets/:id where :id is used to build a DynamoDB key (partition/sort). An attacker supplies a decomposed form that normalizes to the same logical ID as another user’s item. Because the scan tests input validation and property authorization across normalized and unnormalized forms, such mismatches are flagged as BOLA/IDOR risks. Data exposure can occur when query filters fail to align with the primary key schema due to inconsistent normalization, potentially returning items that should be restricted.

Echo Go handlers that bind JSON bodies or URL parameters should normalize before any DynamoDB operation. For example, if a request includes a user-controlled identifier that participates in a DynamoDB GetItem or Query, the application must normalize the identifier using a standard form (NFC or NFD) consistently across all layers. Without this, the scan’s checks for Input Validation and Property Authorization highlight the risk of treating canonically equivalent strings as distinct, which can lead to privilege escalation or unauthorized data access patterns similar to BOLA/IDOR.

Remediation requires normalizing user input to a canonical form before using it with DynamoDB operations in Echo Go. Choose NFC (or NFD) and apply it consistently for all key construction, filtering, and attribute comparisons. Use the golang.org/x/text/unicode/norm package to normalize strings and ensure that any string used in a DynamoDB key or condition expression is already normalized.

Example: Normalized GetItem by ID

import (
    "github.com/labstack/echo/v4"
    "golang.org/x/text/unicode/norm"
    "github.com/aws/aws-sdk-go-v2/service/dynamodb"
    "github.com/aws/aws-sdk-go-v2/aws"
)

func GetWidget(c echo.Context) error {
    client := c.Get("dynamoClient").(*dynamodb.Client)
    rawID := c.Param("id")
    id := norm.NFC.String(rawID)

    out, err := client.GetItem(c.Request().Context(), &dynamodb.GetItemInput{
        TableName: aws.String("Widgets"),
        Key: map[string]types.AttributeValue{
            "ID": &types.AttributeValueMemberS{Value: id},
        },
    })
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    if out.Item == nil {
        return echo.NewHTTPError(http.StatusNotFound)
    }
    return c.JSON(out.Item)
}

Example: Normalized Query with Filter

func ListWidgetsByOwner(c echo.Context) error {
    client := c.Get("dynamoClient").(*dynamodb.Client)
    rawOwner := c.QueryParam("owner")
    owner := norm.NFC.String(rawOwner)

    out, err := client.Query(c.Request().Context(), &dynamodb.QueryInput{
        TableName: aws.String("Widgets"),
        KeyConditionExpression: aws.String("Owner = :o"),
        ExpressionAttributeValues: map[string]types.AttributeValue{
            ":o": &types.AttributeValueMemberS{Value: owner},
        },
    })
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    return c.JSON(out.Items)
}

Example: Normalizing JSON Payload Attributes

type CreateWidgetRequest struct {
    ID     string `json:"id"`
    Name   string `json:"name"`
    Labels []string `json:"labels"`
}

func CreateWidget(c echo.Context) error {
    var req CreateWidgetRequest
    if err := c.Bind(&req); err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, err.Error())
    }

    client := c.Get("dynamoClient").(*dynamodb.Client)
    normID := norm.NFC.String(req.ID)
    normName := norm.NFC.String(req.Name)
    normLabels := make([]string, len(req.Labels))
    for i, lbl := range req.Labels {
        normLabels[i] = norm.NFC.String(lbl)
    }

    _, err := client.PutItem(c.Request().Context(), &dynamodb.PutItemInput{
        TableName: aws.String("Widgets"),
        Item: map[string]types.AttributeValue{
            "ID":   &types.AttributeValueMemberS{Value: normID},
            "Name": &types.AttributeValueMemberS{Value: normName},
            "Labels": &types.AttributeValueMemberSS{Value: normLabels},
        },
    })
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    return c.JSON(map[string]string{"status": "created"})
}

These patterns ensure that the same logical string always maps to the same DynamoDB key, reducing the risk of BOLA/IDOR and data exposure flagged by the scan. The scan’s checks for Input Validation and Property Authorization will highlight remaining mismatches if normalization is applied inconsistently across endpoints.