Ldap Injection in Buffalo with Dynamodb

Ldap Injection occurs when untrusted input is concatenated into LDAP queries without validation or escaping, allowing an attacker to manipulate the query structure. In a Buffalo application that uses Dynamodb as a backend data store, this typically happens when the app builds LDAP filter strings dynamically using user-controlled parameters such as usernames or group identifiers. While Dynamodb itself does not speak LDAP, the vulnerability arises in the application layer where LDAP queries are constructed before any data is written to or read from Dynamodb.

For example, a Buffalo handler might retrieve a username from a request, then embed it directly into an LDAP filter to authorize or look up a user before performing a Dynamodb operation. If the input is not sanitized, an attacker can supply something like admin)(uid=*) as the username, which alters the LDAP filter logic and may bypass authentication or cause unauthorized data retrieval. The combination is risky because it couples an inherently unsafe string-building pattern with a sensitive protocol (LDAP), and the data ultimately persisted or retrieved from Dynamodb may reflect the malicious query’s scope.

An illustrative scenario: a search function builds an LDAP filter as (&(uid=USER_INPUT)(objectClass=person)). If USER_INPUT is not escaped, an attacker can break out of the intended filter context. Even though Dynamodb stores profile attributes, the compromised LDAP query can lead to exposure of sensitive identity data or enable privilege escalation in systems that rely on LDAP for authentication against the Dynamodb-backed identity store.

To prevent Ldap Injection in a Buffalo application that interacts with Dynamodb, always treat user input as untrusted and avoid building LDAP filters via string concatenation. Use parameterized APIs or well-defined escaping libraries for LDAP filter components. Below are concrete code examples demonstrating a vulnerable pattern and a remediated pattern in Go using the Buffalo framework and the AWS SDK for Dynamodb.

Vulnerable pattern (do not use)

// WARNING: vulnerable to LDAP Injection
username := params.Get("username")
ldapFilter := "(&(uid=" + username + ")(objectClass=person))"
// Use ldapFilter in LDAP operations…
// Then, based on LDAP result, perform a Dynamodb operation:
input := &dynamodb.GetItemInput{
    TableName: aws.String("Users"),
    Key: map[string]awstypes.AttributeValue{
        "Username": &awstypes.AttributeValueMemberS{Value: username},
    },
}
result, err := dynamoClient.GetItem(context.Background(), input)
if err != nil {
    // handle error
}

Remediated pattern

// Safe approach: validate and escape user input for LDAP, and use DynamoDB expressions for data access
import (
    "github.com/gobuffalo/buffalo"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
    "gopkg.in/ldap.v3"
)

func safeHandler(c buffalo.Context) error {
    username := c.Param("username")

    // 1) Validate username format (alphanumeric + limited symbols)
    if !regexp.MustCompile(`^[a-zA-Z0-9._-]{1,64}$`).MatchString(username) {
        return c.Render(400, r.Text("Invalid username"))
    }

    // 2) Build LDAP filter safely using ldap.EscapeFilter
    ldapFilter := ldap.Filter{Attributes: []string{"uid"}, Values: []string{username}}.Build()
    // ldapFilter is now safe: special characters are escaped

    // 3) Use the same validated username for DynamoDB operations
    // Prefer DynamoDB condition expressions or parameterized queries
    input := &dynamodb.GetItemInput{
        TableName: aws.String("Users"),
        Key: map[string]awstypes.AttributeValue{
            "Username": &awstypes.AttributeValueMemberS{Value: username},
        },
    }

    // Alternatively, use ExpressionAttributeNames/Values for more complex queries:
    /*
    input := &dynamodb.QueryInput{
        TableName: aws.String("Users"),
        KeyConditionExpression: aws.String("username = :u"),
        ExpressionAttributeValues: map[string]awstypes.AttributeValue{
            ":u": &awstypes.AttributeValueMemberS{Value: username},
        },
    }
    */

    result, err := dynamoClient.GetItem(context.Background(), input)
    if err != nil {
        return c.Render(500, r.Text("Server error"))
    }

    var user Profile
    if err := dynamodbattribute.UnmarshalMap(result.Item, &user); err != nil {
        return c.Render(500, r.Text("Deserialization error"))
    }

    // Optionally, if you still need LDAP for group membership checks:
    // conn, err := ldap.Dial("tcp", "ldap.example.com:389")
    // searchRequest := ldap.NewSearchRequest(
    //     "dc=example,dc=com",
    //     ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
    //     ldapFilter,
    //     []string{"dn"},
    //     nil,
    // )
    // ...

    return c.Render(200, r.JSON(user))
}

Key takeaways: validate input strictly, use LDAP libraries to escape filter components, and rely on DynamoDB’s expression-based APIs with parameterized values to avoid injection across the stack. This reduces risk in applications that use LDAP for identity while persisting data in Dynamodb.