From e2b13e22244df773df06c280425acc78828f7747 Mon Sep 17 00:00:00 2001
From: EC2 Default User <eisin@users.noreply.github.com>
Date: Sun, 1 Jul 2018 02:28:15 +0000
Subject: initial added

---
 pamldapd.go | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 pamldapd.go

diff --git a/pamldapd.go b/pamldapd.go
new file mode 100644
index 0000000..af1d36a
--- /dev/null
+++ b/pamldapd.go
@@ -0,0 +1,143 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"github.com/msteinert/pam"
+	"github.com/nmcclain/ldap"
+	"log"
+	"net"
+	"os"
+	"os/user"
+	"strings"
+)
+
+type Backend struct {
+	ldap.Binder
+	ldap.Searcher
+	ldap.Closer
+	logger         *log.Logger
+	BaseDN         string
+	PAMServiceName string
+}
+
+var logger = log.New(os.Stdout, "", log.LstdFlags)
+
+func main() {
+	logger.Println("start")
+	l := ldap.NewServer()
+	l.EnforceLDAP = true
+	var handler = Backend{
+		PAMServiceName: "password-auth",
+		logger:         logger,
+		BaseDN:         "dc=example,dc=com",
+	}
+	l.BindFunc("", handler)
+	l.SearchFunc("", handler)
+	l.CloseFunc("", handler)
+	if err := l.ListenAndServe("0.0.0.0:10893"); err != nil {
+		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)
+	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())
+	var username string
+	if username, err = b.getUserNameFromBindDN(bindDN); err != nil {
+		return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, err
+	}
+	filterEntity, err := ldap.GetFilterObjectClass(req.Filter)
+	if err != nil {
+		b.logger.Printf("Search Error: error parsing filter: %s", req.Filter)
+		return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("Search Error: error parsing filter: %s", req.Filter)
+	}
+	if filterEntity == "posixaccount" || filterEntity == "" {
+		var entry *ldap.Entry
+		if entry, err = b.makeSearchEntry(bindDN, username); err != nil {
+			return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, err
+		}
+		return ldap.ServerSearchResult{[]*ldap.Entry{entry}, []string{}, []ldap.Control{}, ldap.LDAPResultSuccess}, nil
+	} else {
+		return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("filter entity could be: posixaccount")
+	}
+
+	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.BaseDN) {
+		return "", errors.New("bindDN not matched")
+	}
+	rest := strings.TrimSuffix(bindDN, ","+b.BaseDN)
+	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=") {
+		return "", errors.New("bindDN contains no uid entry")
+	}
+	username = strings.TrimPrefix(rest, "uid=")
+	return username, nil
+}
+
+func (b Backend) makeSearchEntry(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
+}
-- 
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