Ldap Injection in Buffalo with Jwt Tokens

LDAP Injection is an injection attack that occurs when an application constructs LDAP queries using unsanitized user input. In the Buffalo framework, this risk can arise when authentication or authorization logic builds LDAP filter strings by concatenating request-supplied values, such as identifiers extracted from JWT tokens. JWTs are commonly used for stateless authentication and may carry user identifiers, roles, or group memberships. If a Buffalo application decodes a JWT and directly uses a claim (e.g., sub, email, or groups) to build an LDAP search or bind filter, the application can unintentionally introduce injection points.

Consider a scenario where the JWT contains a username claim and the server uses it to query an LDAP directory to retrieve group memberships for authorization. A vulnerable pattern might look like constructing an LDAP filter by string interpolation:

ldapFilter := fmt.Sprintf("(&(objectClass=person)(uid=%s))", userSuppliedValue)

If userSuppliedValue originates from a JWT claim and is not strictly validated, an attacker who can influence the JWT (via a weak signing algorithm, token leakage, or an insecure client-side payload) can inject LDAP metacharacters. For example, a token containing username=admin)(objectClass=*) would alter the filter to (&(objectClass=person)(uid=admin)(objectClass=*)), potentially returning all entries. This can lead to unauthorized data retrieval or bypass intended access controls. Because JWTs are often considered trustworthy, developers may skip rigorous input validation, inadvertently widening the attack surface. The combination of Buffalo’s routing and template handling with JWT-based identity and LDAP directory queries creates a scenario where injection can affect authentication and authorization decisions without obvious errors in the application code.

Additionally, if the application uses JWTs for session handling or to pass authorization claims that influence LDAP queries (such as group-based access), improper parsing or over-trust in token contents can expose path traversal or wildcard injection risks within LDAP filters. Attack patterns like escaping filters, leveraging reserved characters (e.g., asterisk, parentheses, backslash), or exploiting null byte handling may be leveraged depending on the LDAP server implementation. The key vulnerability arises not from JWTs themselves, but from the unsafe composition of LDAP queries using data extracted from those tokens without strict allow-listing, canonicalization, or parameterization.

To mitigate LDAP Injection risks when working with JWT tokens in Buffalo, ensure that any data derived from JWT claims is treated as untrusted input. Apply strict allow-listing validation, avoid direct string interpolation into LDAP filters, and use parameterized LDAP queries or builder APIs where available. Below are concrete remediation patterns and code examples tailored for Buffalo applications.

• Validate and sanitize JWT claims before using them in LDAP queries. Use a strict allow-list for known claims and enforce type and pattern checks. For example, if a JWT contains a username claim, ensure it matches a safe regular expression before use:

import (
    "regexp"
    "github.com/gobuffalo/buffalo"
)

var usernameRegex = regexp.MustCompile(`^[a-zA-Z0-9._-]{3,64}$`)

func validateUsernameFromToken(c buffalo.Context) (string, error) {
    // Assume claims have been extracted and validated earlier
    username := c.Params().Get("username") // or from JWT claims map
    if !usernameRegex.MatchString(username) {
        return "", buffalo.NewError(400, "invalid_username_format")
    }
    return username, nil
}

• Use parameterized LDAP filters instead of string concatenation. Construct filters using a structured approach to prevent metacharacter injection. If your LDAP library supports it, prefer building filters with placeholders or dedicated builder functions:

import (
    "github.com/go-ldap/ldap/v3"
    "github.com/gobuffalo/buffalo"
)

func buildSafeLDAPFilter(username string) (*ldap.Filter, error) {
    // Use library functions to construct filters safely
    return ldap.NewFilter("objectClass", "person").And(ldap.NewFilter("uid", username)), nil
}

func searchLDAP(c buffalo.Context) buffalo.Render {
    username, err := validateUsernameFromToken(c)
    if err != nil {
        return c.Render(400, r.JSON(map[string]string{"error": err.Error()}))
    }
    baseDN := "dc=example,dc=com"
    scope := ldap.ScopeWholeSubtree
    filter, err := buildSafeLDAPFilter(username)
    if err != nil {
        return c.Render(400, r.JSON(map[string]string{"error": "invalid_filter"}))
    }
    // Assuming an established LDAP connection conn
    searchReq := ldap.NewSearchRequest(baseDN, scope, ldap.NeverDerefAliases, 0, 0, false, filter.String(), []string{"dn", "mail"}, nil)
    // Execute search with conn.Search(searchReq)
    return c.Render(200, r.JSON(map[string]interface{}{"filter": filter.String()}))
}

• Apply principle of least privilege and avoid trusting JWT content for authorization decisions that map directly to LDAP queries. Consider mapping JWT roles or groups to a local authorization model rather than using raw claims to form LDAP filters. If you must use LDAP queries, perform server-side checks and use precompiled or parameterized queries to ensure that special characters are never interpreted as control elements.

By combining strict input validation, safe LDAP filter construction, and reduced trust in JWT-derived data, Buffalo applications can neutralize LDAP Injection vectors that might otherwise be introduced through token-based identity claims.