Ldap Injection in Chi with Cockroachdb

LDAP Injection is an attack technique that manipulates LDAP query construction to bypass authentication or extract data. When using the Chi router with a Cockroachdb backend, risk arises when user-supplied input is concatenated into LDAP filters without validation or parameterization. Chi is a minimal, idiomatic router for Go, and developers often wire it to external services such as LDAP for authentication. If an LDAP client is built by string-interpolating values from Chi context variables (for example, a username or search filter), an attacker can inject malicious syntax like (uid=*)(objectClass=*) or append always-true components ((&(objectClass=person)(cn=*)) into the filter.

Consider a handler created with Chi where a POST parameter user is read and directly used in an LDAP filter:

import (
    "github.com/go-chi/chi/v5"
    "gopkg.in/ldap.v3"
)

func loginHandler(w http.ResponseWriter, r *http.Request) {
    user := chi.URLParam(r, "username")
    ldapFilter := "(uid=" + user + ")"

    l, err := ldap.Dial("tcp", "ldap.example.com:389")
    if err != nil {
        http.Error(w, "cannot connect", 500)
        return
    }
    defer l.Close()

    searchReq := ldap.NewSearchRequest(
        "dc=example,dc=com",
        ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
        ldapFilter,
        []string{"cn", "mail"},
        nil,
    )
    sr, err := l.Search(searchReq)
    if err != nil || len(sr.Entries) == 0 {
        http.Error(w, "invalid credentials", 401)
        return
    }
    // bind and proceed
}

An attacker sending username=*)(objectClass=*) rewrites the filter to (uid=*)(objectClass=*)), which may bypass intended matching logic or cause the server to return more entries than expected. With Cockroachdb storing user metadata or mappings (e.g., a table that links uid to tenant or role data), a successful LDAP injection can lead to information disclosure or unauthorized access patterns that are difficult to detect without audit logging. Cockroachdb’s SQL interface is not directly involved in the LDAP bind, but if the application uses the LDAP-validated identity to construct SQL queries (for example, selecting permissions from Cockroachdb based on the authenticated subject), the injected LDAP content may propagate into SQL strings, compounding the risk.

The vulnerability is not inherent to Chi or Cockroachdb, but to the developer practice of concatenating uncontrolled input into LDAP filters. Chi’s pattern of extracting URL or body parameters is predictable, which makes it straightforward to audit, yet without strict input validation and encoding, it remains a pathway for injection. Cockroachdb’s role is passive here; the exposure occurs because application logic bridges LDAP identities to data stored in the distributed database without sufficient isolation between authentication and authorization layers.

Remediation focuses on preventing LDAP injection by avoiding string concatenation and using parameterized filters or prepared statements where applicable. For Go LDAP clients, constructing filters with ldap.NewFilterControl or using the ldap.BuildFilter pattern ensures that special characters are escaped properly. Below are concrete, idiomatic examples integrating Chi with secure LDAP handling and Cockroachdb-safe patterns.

Secure LDAP Filter Construction

Instead of concatenation, build the filter programmatically:

import (
    "github.com/go-chi/chi/v5"
    "gopkg.in/ldap.v3"
)

func secureLoginHandler(w http.ResponseWriter, r *http.Request) {
    user := chi.URLParam(r, "username")

    // Escape special LDAP characters in user input
    escapedUser := ldap.EscapeFilter(user)
    filter := ldap.BuildFilter(ldap.AndFilter{
        ldap.EqualFoldFilter{"uid", escapedUser},
        ldap.EqualFoldFilter{"objectClass", "person"},
    }).Filter()

    l, err := ldap.Dial("tcp", "ldap.example.com:389")
    if err != nil {
        http.Error(w, "cannot connect", 500)
        return
    }
    defer l.Close()

    searchReq := ldap.NewSearchRequest(
        "dc=example,dc=com",
        ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
        filter,
        []string{"cn", "mail"},
        nil,
    )
    sr, err := l.Search(searchReq)
    if err != nil || len(sr.Entries) == 0 {
        http.Error(w, "invalid credentials", 401)
        return
    }
    // Safe to proceed with bind using sr.Entries[0].DN
}

By using ldap.EscapeFilter and ldap.BuildFilter, special characters such as asterisks, parentheses, and backslashes are properly escaped, neutralizing injection attempts. This approach is compatible with any LDAP server and aligns with best practices for filter construction.

Safe Mapping to Cockroachdb After LDAP Validation

After successful LDAP authentication, minimize the surface area when interacting with Cockroachdb. Use prepared statements or parameterized queries to avoid any residual risk of injection through the identity pipeline:

import (
    "database/sql"
    _ "github.com/lib/pq"
)

func fetchUserPermissions(db *sql.DB, dn string) (string, error) {
    // Use a parameterized query; dn is the authenticated identity from LDAP
    row := db.QueryRow("SELECT permissions FROM users WHERE ldap_dn = $1", dn)
    var perms string
    if err := row.Scan(&perms); err != nil {
        return "", err
    }
    return perms, nil
}

Even though Cockroachdb does not use traditional SQL injection in the same way as some databases, parameterized queries remain the safest pattern. This ensures that the identity derived from LDAP cannot alter query structure. The combination of escaped LDAP filters and parameterized SQL creates defense-in-depth across authentication and data access layers.

Operational Considerations

• Validate and sanitize all Chi URL and body parameters before they reach authentication logic.
• Log failed LDAP filter attempts with sufficient context for audit, but avoid logging raw user input in full to prevent log injection.
• Keep LDAP client libraries updated to mitigate known protocol-level vulnerabilities.