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package main
import (
"errors"
"fmt"
"github.com/msteinert/pam"
"github.com/nmcclain/asn1-ber"
"github.com/nmcclain/ldap"
"log"
"net"
"os"
"os/user"
"strings"
)
type Backend struct {
ldap.Binder
ldap.Searcher
ldap.Closer
logger *log.Logger
Listen string
BaseDN string
PAMServiceName string
PeopleDN string
GroupsDN string
BindAdminDN string
BindAdminPassword string
}
var logger = log.New(os.Stdout, "", log.LstdFlags)
func main() {
logger.Println("start")
l := ldap.NewServer()
l.EnforceLDAP = true
var backend = Backend{
PAMServiceName: "password-auth",
logger: logger,
Listen: "127.0.0.1:10389",
BaseDN: "dc=example,dc=com",
PeopleDN: "ou=people,dc=example,dc=com",
GroupsDN: "ou=groups,dc=example,dc=com",
BindAdminDN: "uid=user,dc=example,dc=com",
BindAdminPassword: "password",
}
l.BindFunc("", backend)
l.SearchFunc("", backend)
l.CloseFunc("", backend)
if err := l.ListenAndServe(backend.Listen); err != nil {
backend.logger.Fatalf("LDAP serve failed: %s", err.Error())
}
}
func (b Backend) Bind(bindDN, bindSimplePw string, conn net.Conn) (resultCode ldap.LDAPResultCode, err error) {
b.logger.Printf("Bind attempt addr=%s bindDN=%s", conn.RemoteAddr().String(), bindDN)
if bindDN == b.BindAdminDN {
if bindSimplePw != b.BindAdminPassword {
return ldap.LDAPResultInvalidCredentials, errors.New("Password Incorrect")
}
return ldap.LDAPResultSuccess, nil
} else {
var username string
if username, err = b.getUserNameFromBindDN(bindDN); err != nil {
return ldap.LDAPResultInvalidCredentials, err
}
if err := PAMAuth(b.PAMServiceName, username, bindSimplePw); err != nil {
return ldap.LDAPResultInvalidCredentials, err
}
return ldap.LDAPResultSuccess, nil
}
}
func (b Backend) Search(bindDN string, req ldap.SearchRequest, conn net.Conn) (result ldap.ServerSearchResult, err error) {
b.logger.Printf("Search bindDN=%s baseDN=%s filter=%s addr=%s", bindDN, req.BaseDN, req.Filter, conn.RemoteAddr().String())
filterObjectClass, err := ldap.GetFilterObjectClass(req.Filter)
if err != nil {
b.logger.Printf("Search Error: error parsing ObjectClass: %s", req.Filter)
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("Search Error: error parsing ObjectClass: %s", req.Filter)
}
var username string
var user_entity_name string
if filterObjectClass == "posixaccount" || filterObjectClass == "" {
user_entity_name = "uid"
} else if filterObjectClass == "posixgroup" {
user_entity_name = "memberUid"
} else {
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("Filter does not contain objectclass=posixaccount nor objectclass=posixgroup")
}
if bindDN == b.BindAdminDN {
filterUid, err := GetFilterEntity(user_entity_name, req.Filter)
if err != nil {
b.logger.Printf("Search Error: error find condition uid: %s", req.Filter)
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("Search Error: error find condition uid: %s", req.Filter)
}
username = filterUid
} else {
if username, err = b.getUserNameFromBindDN(bindDN); err != nil {
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, err
}
}
var entry *ldap.Entry
if filterObjectClass == "posixaccount" || filterObjectClass == "" {
if entry, err = b.makeSearchEntryAccount("cn="+username+","+b.PeopleDN, username); err != nil {
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, err
}
} else if filterObjectClass == "posixgroup" {
if entry, err = b.makeSearchEntryGroup(b.GroupsDN, username); err != nil {
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, err
}
} else {
return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("Filter does not contain objectclass=posixaccount nor objectclass=posixgroup")
}
return ldap.ServerSearchResult{[]*ldap.Entry{entry}, []string{}, []ldap.Control{}, ldap.LDAPResultSuccess}, nil
return ldap.ServerSearchResult{make([]*ldap.Entry, 0), []string{}, []ldap.Control{}, ldap.LDAPResultSuccess}, nil
}
func (b Backend) Close(bindDN string, conn net.Conn) (err error) {
b.logger.Printf("Close addr=%s bindDN=%s", conn.RemoteAddr().String(), bindDN)
return nil
}
func PAMAuth(serviceName, userName, passwd string) error {
t, err := pam.StartFunc(serviceName, userName, func(s pam.Style, msg string) (string, error) {
switch s {
case pam.PromptEchoOff:
return passwd, nil
case pam.PromptEchoOn, pam.ErrorMsg, pam.TextInfo:
return "", nil
}
return "", errors.New("Unrecognized PAM message style")
})
if err != nil {
return err
}
if err = t.Authenticate(0); err != nil {
return err
}
return nil
}
func (b Backend) getUserNameFromBindDN(bindDN string) (username string, err error) {
if bindDN == "" {
return "", errors.New("bindDN not specified")
}
if !strings.HasSuffix(bindDN, ","+b.PeopleDN) {
return "", errors.New("bindDN not matched")
}
rest := strings.TrimSuffix(bindDN, ","+b.PeopleDN)
if rest == "" {
return "", errors.New("bindDN format error")
}
if strings.Contains(rest, ",") {
return "", errors.New("bindDN has too much entities")
}
if strings.HasPrefix(rest, "uid=") {
username = strings.TrimPrefix(rest, "uid=")
} else if strings.HasPrefix(rest, "cn=") {
username = strings.TrimPrefix(rest, "cn=")
} else {
return "", errors.New("bindDN contains no cn/uid entry")
}
return username, nil
}
func (b Backend) makeSearchEntryAccount(dn string, username string) (entry *ldap.Entry, err error) {
attrs := []*ldap.EntryAttribute{}
var u *user.User
if u, err = user.Lookup(username); err != nil {
return entry, err
}
attrs = append(attrs, &ldap.EntryAttribute{"objectClass", []string{"posixAccount"}})
attrs = append(attrs, &ldap.EntryAttribute{"cn", []string{username}})
attrs = append(attrs, &ldap.EntryAttribute{"uid", []string{username}})
attrs = append(attrs, &ldap.EntryAttribute{"uidNumber", []string{u.Uid}})
attrs = append(attrs, &ldap.EntryAttribute{"givenName", []string{u.Name}})
attrs = append(attrs, &ldap.EntryAttribute{"gidNumber", []string{u.Gid}})
attrs = append(attrs, &ldap.EntryAttribute{"homeDirectory", []string{u.HomeDir}})
entry = &ldap.Entry{dn, attrs}
return entry, nil
}
func (b Backend) makeSearchEntryGroup(basedn string, username string) (entry *ldap.Entry, err error) {
attrs := []*ldap.EntryAttribute{}
var (
u *user.User
g *user.Group
)
if u, err = user.Lookup(username); err != nil {
return entry, err
}
if g, err = user.LookupGroupId(u.Gid); err != nil {
return entry, err
}
attrs = append(attrs, &ldap.EntryAttribute{"objectClass", []string{"posixGroup"}})
attrs = append(attrs, &ldap.EntryAttribute{"cn", []string{g.Name}})
attrs = append(attrs, &ldap.EntryAttribute{"gidNumber", []string{u.Gid}})
attrs = append(attrs, &ldap.EntryAttribute{"memberUid", []string{username}})
dn := "cn=" + g.Name + "," + basedn
entry = &ldap.Entry{dn, attrs}
return entry, nil
}
func GetFilterEntity(entity string, filter string) (string, error) {
f, err := ldap.CompileFilter(filter)
if err != nil {
return "", err
}
return parseFilterEntity(entity, f)
}
func parseFilterEntity(entity string, f *ber.Packet) (string, error) {
foundEntity := ""
switch ldap.FilterMap[f.Tag] {
case "Equality Match":
if len(f.Children) != 2 {
return "", errors.New("Equality match must have only two children")
}
attribute := strings.ToLower(f.Children[0].Value.(string))
value := f.Children[1].Value.(string)
if attribute == entity {
foundEntity = strings.ToLower(value)
}
case "And":
for _, child := range f.Children {
subType, err := parseFilterEntity(entity, child)
if err != nil {
return "", err
}
if len(subType) > 0 {
foundEntity = subType
}
}
case "Or":
for _, child := range f.Children {
subType, err := parseFilterEntity(entity, child)
if err != nil {
return "", err
}
if len(subType) > 0 {
foundEntity = subType
}
}
case "Not":
if len(f.Children) != 1 {
return "", errors.New("Not filter must have only one child")
}
subType, err := parseFilterEntity(entity, f.Children[0])
if err != nil {
return "", err
}
if len(subType) > 0 {
foundEntity = subType
}
}
return strings.ToLower(foundEntity), nil
}
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