1 files changed, 296 insertions, 0 deletions
diff --git a/src/pamldapd.go b/src/pamldapd.go
new file mode 100644
index 0000000..b43797b
--- /dev/null
+++ b/src/pamldapd.go
@@ -0,0 +1,296 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"flag"
+	"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
+	PAMServiceName    string
+	PeopleDN          string
+	GroupsDN          string
+	BindAdminDN       string
+	BindAdminPassword string
+}
+
+func main() {
+	var configfile = flag.String("c", "pamldapd.json", "Configuration file")
+	var logfile = flag.String("l", "", "Log file (STDOUT if blank)")
+	flag.Parse()
+	var backend = Backend{}
+	{
+		confighandle, err := os.Open(*configfile)
+		if err != nil {
+			fmt.Printf("Could not read: %s\n", err)
+			os.Exit(1)
+		}
+		decoder := json.NewDecoder(confighandle)
+		if err := decoder.Decode(&backend); err != nil {
+			fmt.Printf("Could not decode configuration configfile %s: %s\n", *configfile, err)
+			confighandle.Close()
+			os.Exit(1)
+		}
+		confighandle.Close()
+	}
+	if *logfile == "" {
+		backend.logger = log.New(os.Stdout, "", log.LstdFlags)
+	} else {
+		loghandle, err := os.OpenFile(*logfile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
+		if err != nil {
+			fmt.Printf("Could not open log file: %s\n", err)
+			os.Exit(1)
+		}
+		defer loghandle.Close()
+		log.SetOutput(loghandle)
+		backend.logger = log.New(loghandle, "", log.LstdFlags)
+	}
+
+	current_user, err := user.Current()
+	if err != nil {
+		fmt.Printf("Could not get current user: %s\n", err)
+		os.Exit(1)
+	}
+	if current_user.Uid != "0" {
+		backend.logger.Printf("WARNING: PAM authentication will fail because not running as root user")
+	}
+
+	l := ldap.NewServer()
+	l.EnforceLDAP = true
+	l.BindFunc("", backend)
+	l.SearchFunc("", backend)
+	l.CloseFunc("", backend)
+	backend.logger.Printf("LDAP server listen: %s", backend.Listen)
+	if err := l.ListenAndServe(backend.Listen); err != nil {
+		backend.logger.Fatalf("LDAP server listen failed: %s", err.Error())
+	}
+}
+
+func (b Backend) Bind(bindDN, bindSimplePw string, conn net.Conn) (resultCode ldap.LDAPResultCode, err error) {
+	var logger_title = fmt.Sprintf("Bind addr=%s bindDN=%s", conn.RemoteAddr().String(), bindDN)
+	b.logger.Printf("%s begin", logger_title)
+	if bindDN == b.BindAdminDN {
+		if bindSimplePw != b.BindAdminPassword {
+			return ldap.LDAPResultInvalidCredentials, errors.New("Password Incorrect")
+		}
+		b.logger.Printf("%s success as administrator", logger_title)
+		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
+		}
+		b.logger.Printf("%s success as normal user", logger_title)
+		return ldap.LDAPResultSuccess, nil
+	}
+}
+
+func (b Backend) Search(bindDN string, req ldap.SearchRequest, conn net.Conn) (result ldap.ServerSearchResult, err error) {
+	var logger_title = fmt.Sprintf("Search bindDN=%s baseDN=%s filter=%s addr=%s", bindDN, req.BaseDN, req.Filter, conn.RemoteAddr().String())
+	b.logger.Printf("%s begin", logger_title)
+	filterObjectClass, err := ldap.GetFilterObjectClass(req.Filter)
+	if err != nil {
+		return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("%s error parsing ObjectClass: %s", logger_title, 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("%s error: Filter does not contain objectclass=posixaccount nor objectclass=posixgroup", logger_title)
+	}
+
+	if bindDN == b.BindAdminDN {
+		filterUid, err := GetFilterEntity(user_entity_name, req.Filter)
+		if err != nil {
+			return ldap.ServerSearchResult{ResultCode: ldap.LDAPResultOperationsError}, fmt.Errorf("%s error find condition uid: %s", logger_title, 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("%s error: Filter does not contain objectclass=posixaccount nor objectclass=posixgroup", logger_title)
+	}
+	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", conn.RemoteAddr().String())
+	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
+}