ldap4gin

README

ldap4gin

Authenticator for gin framework using ldap server

Installing

Usual way for go module

go get -u github.com/vodolaz095/ldap4gin

Code was tested against popular osixia/openldap:1.4.0 container, with records generated using ldapaccountmanager/lam web ui.

Example

Working example is published in example/ subdirectory of this repo

package main

import (
	"bytes"
	"crypto/tls"
	"fmt"
	"log"
	"net/http"

	"github.com/gin-contrib/sessions"
	"github.com/gin-contrib/sessions/cookie"
	"github.com/gin-gonic/gin"
	"github.com/vodolaz095/ldap4gin"
)

func main() {
	r := gin.Default()
	r.LoadHTMLGlob("views/*")
	// configuring options used to connect to LDAP database
	authenticator, err := ldap4gin.New(ldap4gin.Options{
		Debug:            gin.IsDebugging(),
		ConnectionString: "ldap://127.0.0.1:389",
		UserBaseTpl:      "uid=%s,ou=people,dc=vodolaz095,dc=life",
		TLS:              &tls.Config{}, // nearly sane default values
		StartTLS:         false,
		ExtraFields:      []string{"l"}, // get location too
	})
	if err != nil {
		log.Fatalf("%s : while initializing ldap4gin authenticator", err)
	}
	log.Println("LDAP server dialed!")
	store := cookie.NewStore([]byte("secret"))
	r.Use(sessions.Sessions("mysession", store))

	r.GET("/", func(c *gin.Context) {
		session := sessions.Default(c)
		flashes := session.Flashes()
		user, err := authenticator.Extract(c)
		if err != nil {
			if err.Error() == "unauthorized" {
				session.Save()
				c.HTML(http.StatusUnauthorized, "unauthorized.html", gin.H{
					"flashes": flashes,
				})
				return
			}
			panic(err)
		}
		buff := bytes.NewBuffer(nil)
		fmt.Fprintf(buff, "DN: %s\n", user.Entry.DN)
		for _, attr := range user.Entry.Attributes {
			fmt.Fprintf(buff, "%s: %s\n", attr.Name, attr.Values)
		}
		session.Save()
		c.HTML(http.StatusOK, "profile.html", gin.H{
			"user":    user,
			"flashes": flashes,
			"raw":     buff.String(),
		})
	})

	r.POST("/login", func(c *gin.Context) {
		session := sessions.Default(c)
		username := c.PostForm("username")
		password := c.PostForm("password")
		log.Printf("User %s tries to authorize from %s...", username, c.ClientIP())
		err := authenticator.Authorize(c, username, password)
		if err != nil {
			log.Printf("User %s failed to authorize from %s because of %s", username, c.ClientIP(), err.Error())
			session.AddFlash(fmt.Sprintf("Authorization error  %s", err))
		} else {
			log.Printf("User %s authorized from %s!", username, c.ClientIP())
			session.AddFlash(fmt.Sprintf("Welcome, %s!", username))
		}
		session.Save()
		c.Redirect(http.StatusFound, "/")
	})

	r.GET("/logout", func(c *gin.Context) {
		authenticator.Logout(c)
		c.Redirect(http.StatusFound, "/")
	})

	err = r.Run("0.0.0.0:3000")
	if err != nil {
		log.Fatalf("%s : while starting application", err)
	}
}

How it works?

You can read very good article in Russian language describing authentication process via LDAP.

Shortly, these steps are performed in authorize.go module:

1. we build DN using username parameter provided and UserBaseTpl of options

    
    authenticator, err := ldap4gin.New(ldap4gin.Options{
        Debug:            gin.IsDebugging(),
        ConnectionString: "ldap://127.0.0.1:389",
        UserBaseTpl:      "uid=%s,ou=people,dc=vodolaz095,dc=life",
        TLS:              &tls.Config{}, // nearly sane default values
        StartTLS:         false,
        ExtraFields:      []string{"l"}, // get location too
    })

    // some code

    // in gin handler
    err = authenticator.Authorize(c, username, password)

like this: uid=vodolaz095,ou=people,dc=vodolaz095,dc=life.

1. we try to perform bind using DN and password

    authenticator.LDAPConn.Bind(dn, password)

1. if we succeeded, it means user provided good password, and we can try to extract user profile calling this query:

searchRequest := ldap.NewSearchRequest(
    dn,                                // base DN
    ldap.ScopeBaseObject,              // scope 
    ldap.NeverDerefAliases,            // DerefAliases
    0,                                 // size limit
    timeout,                           // timeout
    false,                             // types only
    fmt.Sprintf("(uid=%s)", username), // filter
    a.fields,                          // fields
    nil,                               // controls
)

1. After we extract data, we marshal it in User object, and store it in session using gob encoding. Its is worth notice that sometimes profile size is too big for session storage, and it can be wise not to store all users fields in session

Documentation

Overview

Package ldap4gin is authenticator for gin framework using ldap server

Index

• Constants
• func GetDefaultFields() []string
• type Authenticator
  • func New(opts Options) (a *Authenticator, err error)
  • func (a *Authenticator) Authorize(c *gin.Context, username, password string) (err error)
  • func (a *Authenticator) Extract(c *gin.Context) (user User, err error)
  • func (a *Authenticator) Logout(c *gin.Context) (err error)
• type Options
• type User

Constants

const SessionKeyName = "ldap4gin_user"

SessionKeyName names key used to store user profile in session

Functions

func GetDefaultFields

func GetDefaultFields() []string

GetDefaultFields returns fields we extract from LDAP by default

Types

type Authenticator

type Authenticator struct {

	// LDAPConn is ldap connection being used
	LDAPConn *ldap.Conn
	// contains filtered or unexported fields
}

Authenticator links ldap and gin context together

func New

func New(opts Options) (a *Authenticator, err error)

New creates new authenticator using options provided

func (*Authenticator) Authorize

func (a *Authenticator) Authorize(c *gin.Context, username, password string) (err error)

Authorize tries to find user in ldap database, check his/her password via `bind` and populate session, if password matches

func (*Authenticator) Extract

func (a *Authenticator) Extract(c *gin.Context) (user User, err error)

Extract extracts users profile from session

func (*Authenticator) Logout

func (a *Authenticator) Logout(c *gin.Context) (err error)

Logout terminates user's session

type Options

type Options struct {
	// Debug outputs debugging information, better leave it to false
	Debug bool
	//ConnectionString depicts how we dial LDAP server, something like ldap://127.0.0.1:389 or ldaps://ldap.example.org:636
	ConnectionString string
	// UserBaseTpl is template to extract user profiles by UID, for example  "uid=%s,ou=people,dc=example,dc=org",
	UserBaseTpl string
	// TLS is configuration for encryption to use
	TLS *tls.Config
	// StartTLS shows, do we need to execute StartTLS or not
	StartTLS bool
	// ExtraFields is array of fields, we also extract from database. NOTICE - if you add too many fields, it can hit session size limits!
	ExtraFields []string
}

Options depicts parameters used to instantiate Authenticator

type User

type User struct {
	// General
	DN  string // dn: uid=sveta,ou=people,dc=vodolaz095,dc=life
	UID string //uid: sveta

	// Names
	GivenName  string // `givenname` - Svetlana
	CommonName string // `cn` - Svetlana Belaya
	Initials   string // `initials` - SA
	Surname    string // `sn` - Belaya

	// work specific
	Organization     string // o: R&D
	OrganizationUnit string // Laboratory 47
	Title            string // title: developer
	Description      string // description: writes code

	// Internet related
	Website string   // labeleduri: https://vodolaz095.life
	Emails  []string // `mail` user can have few emails

	// Linux specific
	UIDNumber     uint64 // uidnumber 1000
	GIDNumber     uint64 // gidnumber 1000
	HomeDirectory string // homedirectory: /home/sveta
	LoginShell    string // loginshell - /bin/bash

	// Raw entry extracted from LDAP
	Entry *ldap.Entry
}

User depicts profile of authorized user