feature (nfs): 16 group limit sorting

server/plugin/plg_backend_nfs/auth_helper.go

@@ -19,13 +19,13 @@ func init() {
 	cacheForGroup = NewAppCache(120, 60)
 }
 
-func extractUserInfo(uidHint string, gidHint string, gidsHint string) (uint32, uint32, []uint32) {
+func extractUserInfo(uidHint string, gidHint string, gidsHint string) (uint32, uint32, []groupLabel) {
 	// case 1: everything is being sent as "uid=number, gid=number and gids=number,number,number"
 	if _uid, err := strconv.Atoi(uidHint); err == nil {
 		var (
 			uid  uint32 = uint32(_uid)
 			gid  uint32
-			gids []uint32
+			gids []groupLabel
 		)
 		if _gid, err := strconv.Atoi(gidHint); err == nil {
 			gid = uint32(_gid)
@@ -33,8 +33,9 @@ func extractUserInfo(uidHint string, gidHint string, gidsHint string) (uint32, u
 			gid = uid
 		}
 		for _, t := range strings.Split(gidsHint, ",") {
-			if gid, err := strconv.Atoi(strings.TrimSpace(t)); err == nil {
-				gids = append(gids, uint32(gid))
+			tmp := strings.TrimSpace(t)
+			if gid, err := strconv.Atoi(tmp); err == nil {
+				gids = append(gids, groupLabel{uint32(gid), tmp, 0})
 			}
 		}
 		return uid, gid, gids
@@ -44,7 +45,7 @@ func extractUserInfo(uidHint string, gidHint string, gidsHint string) (uint32, u
 		return _uid, _gid, extractFromEtcGroup(uidHint, _gid)
 	}
 	// case 3: base case
-	return 0, 0, []uint32{}
+	return 0, 0, []groupLabel{}
 }
 
 func extractFromEtcPasswd(username string) (uint32, uint32, error) {
@@ -83,16 +84,22 @@ func extractFromEtcPasswd(username string) (uint32, uint32, error) {
 	return 0, 0, ErrNotFound
 }
 
-func extractFromEtcGroup(username string, primary uint32) []uint32 {
+type groupLabel struct {
+	id       uint32
+	label    string
+	priority int
+}
+
+func extractFromEtcGroup(username string, primary uint32) []groupLabel {
 	if v := cacheForGroup.Get(map[string]string{"username": username}); v != nil {
-		return v.([]uint32)
+		return v.([]groupLabel)
 	}
 	f, err := os.OpenFile("/etc/group", os.O_RDONLY, os.ModePerm)
 	if err != nil {
-		return []uint32{}
+		return []groupLabel{}
 	}
 	defer f.Close()
-	gids := []uint32{}
+	gids := []groupLabel{}
 	lines := bufio.NewReader(f)
 	for {
 		line, _, err := lines.ReadLine()
@@ -116,7 +123,7 @@ func extractFromEtcGroup(username string, primary uint32) []uint32 {
 		if gid, err := strconv.Atoi(s[2]); err == nil {
 			ugid := uint32(gid)
 			if ugid != primary {
-				gids = append(gids, ugid)
+				gids = append(gids, groupLabel{ugid, s[0], 0})
 			}
 		}
 		cacheForGroup.Set(map[string]string{"username": username}, gids)

server/plugin/plg_backend_nfs/auth_unix.go

@@ -3,6 +3,8 @@ package plg_backend_nfs
 import (
 	"bytes"
 	"math/rand"
+	"sort"
+	"strings"
 	"time"
 
 	"github.com/vmware/go-nfs-client/nfs/rpc"
@@ -21,17 +23,34 @@ type AuthUnix struct {
 }
 
 // ref: RFC5531 - page25
-func NewAuthUnix(machineName string, uid, gid uint32, gids []uint32) rpc.Auth {
+func NewAuthUnix(machineName string, uid, gid uint32, gids []groupLabel, gidsHint string) rpc.Auth {
 	w := new(bytes.Buffer)
-	if len(gids) > 16 { // limit of NFS in AUTH_UNIX
-		gids = gids[len(gids)-16 : len(gids)]
+	if len(gids) > 16 { // https://www.rfc-editor.org/rfc/rfc5531.html#page-25
+		// when the limit of AUTH_UNIX is reached, we want to filter out the
+		// groups that are of less of importance
+		for i, _ := range gids {
+			score := 0
+			for _, h := range strings.Split(gidsHint, ",") {
+				if strings.Contains(gids[i].label, strings.TrimSpace(h)) {
+					score += 1
+				}
+			}
+			gids[i].priority = score
+		}
+		sort.Slice(gids, func(i, j int) bool {
+			return gids[i].priority > gids[j].priority
+		})
+		gids = gids[0:16]
+		sort.Slice(gids, func(i, j int) bool {
+			return gids[i].id < gids[j].id
+		})
 	}
 	xdr.Write(w, AuthUnix{
 		Stamp:       rand.New(rand.NewSource(time.Now().UnixNano())).Uint32(),
 		Machinename: machineName,
 		Uid:         uid,
 		Gid:         gid,
-		Gids:        gids,
+		Gids:        toGids(gids),
 	})
 	return rpc.Auth{
 		1, // = AUTH_SYS in RFC5531

server/plugin/plg_backend_nfs/index.go

@@ -44,7 +44,7 @@ func (this NfsShare) Init(params map[string]string, app *App) (IBackend, error)
 	if err != nil {
 		return nil, err
 	}
-	auth := NewAuthUnix(params["machine_name"], uid, gid, gids)
+	auth := NewAuthUnix(params["machine_name"], uid, gid, gids, params["gids"])
 	v, err := mount.Mount(
 		params["target"],
 		auth,
@@ -52,7 +52,15 @@ func (this NfsShare) Init(params map[string]string, app *App) (IBackend, error)
 	if err != nil {
 		return nil, err
 	}
-	return NfsShare{mount, v, auth, app.Context, uid, gid, gids}, nil
+	return NfsShare{mount, v, auth, app.Context, uid, gid, toGids(gids)}, nil
+}
+
+func toGids(gids []groupLabel) []uint32 {
+	g := make([]uint32, len(gids))
+	for _, gid := range gids {
+		g = append(g, gid.id)
+	}
+	return g
 }
 
 func (this NfsShare) LoginForm() Form {