Ldap Injection in Echo Go with Api Keys

Ldap Injection occurs when an attacker can manipulate LDAP query construction through untrusted input. In Echo Go, this risk can be amplified when API keys are handled as user-controlled values that feed into LDAP filters or bind operations. If an API key is accepted as a query parameter, header, or form field and then concatenated into an LDAP search filter without validation or escaping, the attacker can alter the filter logic. For example, a key value containing special LDAP characters such as (, ), *, or \00 can change the intended scope or bypass authentication checks.

Consider an Echo Go handler that receives an api_key and uses it to build an LDAP filter to locate a user entry:

filter := fmt.Sprintf("(uid=%s)", apiKey)

If apiKey is supplied by the caller and not sanitized, an input like admin)(objectClass=*) modifies the filter to:

(uid=admin)(objectClass=*)

This can return unintended entries or bypass intended access controls. In the context of an unauthenticated scan, middleBrick tests such injection paths among its 12 parallel checks, including input validation and authentication checks. The presence of API keys in query parameters or headers does not inherently create LDAP Injection, but using them directly in string building for LDAP filters exposes the attack surface. This pattern can lead to information disclosure, unauthorized binding, or enumeration depending on how the LDAP server responds to the malformed filter.

Additionally, if the API key is used to construct a bind DN without proper validation, an attacker might supply a value like uid=*,cn=users,dc=example,dc=com to attempt broad authentication attempts. Because middleBrick performs active input validation testing, it flags scenarios where special characters in API key values can escape intended filter boundaries, aligning with findings categorized under Input Validation and Authentication in the scan output.

To remediate LDAP Injection risks when using API keys in Echo Go, ensure that API key values are never directly interpolated into LDAP filters or DNs. Instead, treat API keys as opaque identifiers and use parameterized LDAP searches or strict allow-lists. Below are concrete code examples demonstrating safer patterns.

Unsafe pattern (vulnerable):

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

Safe pattern 1 — allow-list validation: Validate the API key format against a known set of values or a strict regex before using it.

// Validate api_key against a pattern (e.g., alphanumeric, fixed length)
apiKey := c.Param("api_key")
matched, err := regexp.MatchString(`^[A-Za-z0-9\-_]{16}$`, apiKey)
if err != nil || !matched {
    c.JSON(http.StatusBadRequest, echo.Map{"error": "invalid api_key format"})
    return
}
// Use the validated key as an indexed lookup rather than direct string inclusion
userEntry, err := ldapSearchByApiKey(apiKey) // internal mapping to uid
if err != nil {
    c.JSON(http.StatusInternalServerError, echo.Map{"error": "lookup failed"})
    return
}

Safe pattern 2 — parameterized search with escaping: If you must build filters dynamically, use proper escaping for special characters. The golang.org/x/net/ldap package provides ldap.EscapeFilter to neutralize injection characters.

import "golang.org/x/net/ldap"

apiKey := c.Param("api_key")
escapedKey := ldap.EscapeFilter(apiKey)
filter := fmt.Sprintf("(uid=%s)", escapedKey)
searchRequest := ldap.NewSearchRequest(
    "dc=example,dc=com",
    ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
    filter,
    []string{"dn", "mail"},
    nil,
)

Safe pattern 3 — bind by mapping, not interpolation: Maintain a server-side mapping between API keys and LDAP DNs or identifiers. Use the key only to index into this mapping, avoiding string construction entirely.

type keyMapping map[string]string // maps api_key -> ldapDN

var store = keyMapping{
    "abc123def456ghi7": "uid=john,ou=people,dc=example,dc=com",
    "xyz987uvw654rst2": "uid=mary,ou=people,dc=example,dc=com",
}

apiKey := c.Param("api_key")
dn, ok := store[apiKey]
if !ok {
    c.JSON(http.StatusUnauthorized, echo.Map{"error": "invalid key"})
    return
}
bindRequest := ldap.NewSimpleBindRequest(dn, nil)

These approaches ensure API keys do not directly manipulate LDAP structures. middleBrick’s scans include checks for Input Validation and Authentication, and applying these fixes will align your implementation with secure handling of credentials and directory queries.