Ldap Injection in Gin with Api Keys

Ldap Injection occurs when user-controlled input is concatenated directly into LDAP query strings without sanitization or parameterization. In a Gin-based Go service that uses API keys for access control, this vulnerability can emerge when an attacker-supplied key or key-derived value is passed into an LDAP filter. For example, if an API key is stored as an attribute in an LDAP directory and is used to construct a filter like (uid=API_KEY_VALUE), an attacker who can influence the API key value may inject LDAP metacharacters such as *, (, ), or &. These characters can alter the query logic, enabling unauthorized searches, bypassing intended filters, or extracting sensitive directory information.

Gin does not inherently validate or sanitize inputs used for authentication or authorization. When API keys are bound into LDAP queries using string formatting, the framework’s flexibility becomes a liability. A typical vulnerable pattern involves retrieving an API key from a request header, performing a lookup in LDAP, and constructing the filter via fmt.Sprintf. If the key contains malicious payloads, the LDAP server may interpret them as query operators, leading to classic injection outcomes. This is especially dangerous when the same key is used both for rate limiting and for authorization checks, because an attacker may leverage injection to escalate privileges or harvest directory data.

Moreover, the combination of unauthenticated endpoints and API key usage can amplify risk. If an endpoint that accepts API keys is also exposed through an unauthenticated LLM or public interface, injection vectors may be discovered more easily. Since middleBrick tests unauthenticated attack surfaces and includes checks for Unsafe Consumption and Input Validation, it can flag scenarios where API keys are improperly embedded in LDAP logic. The presence of such patterns does not imply automated fixing—middleBrick reports findings with remediation guidance, highlighting the need for strict input validation and parameterized approaches.

To mitigate Ldap Injection when using API keys in Gin, avoid constructing LDAP filters via string concatenation. Instead, use parameterized LDAP queries or an abstraction that enforces strict input handling. Validate and sanitize API keys before use, and treat them as opaque strings rather than building them into search filters. Below are concrete, working examples demonstrating secure patterns.

Vulnerable Example

// DO NOT DO THIS
key := c.GetHeader("X-API-Key")
filter := fmt.Sprintf("(uid=%s)", key)
searchRequest := ldap.NewSearchRequest(
    "dc=example,dc=com",
    ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
    filter,
    []string{"dn", "mail"},
    nil,
)

Secure Remediation with Input Validation and Parameterization

// Recommended approach in Gin
key := c.GetHeader("X-API-Key")
if !isValidAPIKeyFormat(key) {
    c.AbortWithStatusJSON(400, gin.H{"error": "invalid_api_key_format"})
    return
}

// Use a dedicated LDAP client method that supports parameterized filters if available,
// or construct filter safely using escaping for permitted characters.
escapedKey := ldap.EscapeFilter(key)
filter := fmt.Sprintf("(uid=%s)", escapedKey)

searchRequest := &ldap.SearchRequest{
    BaseDN: "dc=example,dc=com",
    Scope:  ldap.ScopeWholeSubtree,
    DerefAliases: ldap.NeverDerefAliases,
    SizeLimit: 0,
    TimeLimit: 0,
    TypesOnly: false,
    Filter: filter,
    Attributes: []string{"dn", "mail"},
    Controls: nil,
}

The helper function isValidAPIKeyFormat should enforce strict rules, such as allowing only alphanumeric characters and a limited set of safe symbols, and should reject any input containing LDAP metacharacters. For production systems, consider using an LDAP library that supports bind-level authentication with pre-validated credentials rather than constructing complex filters from API keys.

Additionally, integrate middleBrick into your workflow using the CLI (middlebrick scan <url>) or the GitHub Action to detect such patterns during development. The scanner evaluates Input Validation and Unsafe Consumption checks, providing prioritized findings and remediation guidance without modifying your codebase.