libcontainer/user: platform dependent calls

This rearranges a bit of the user and group lookup, such that only a
basic subset is exposed.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

libcontainer/user/lookup.go

@@ -12,84 +12,30 @@ var (
 	ErrNoGroupEntries  = errors.New("no matching entries in group file")
 )
 
-func lookupUser(filter func(u User) bool) (User, error) {
-	// Get operating system-specific passwd reader-closer.
-	passwd, err := GetPasswd()
-	if err != nil {
-		return User{}, err
-	}
-	defer passwd.Close()
-
-	// Get the users.
-	users, err := ParsePasswdFilter(passwd, filter)
-	if err != nil {
-		return User{}, err
-	}
-
-	// No user entries found.
-	if len(users) == 0 {
-		return User{}, ErrNoPasswdEntries
-	}
-
-	// Assume the first entry is the "correct" one.
-	return users[0], nil
-}
-
 // LookupUser looks up a user by their username in /etc/passwd. If the user
 // cannot be found (or there is no /etc/passwd file on the filesystem), then
 // LookupUser returns an error.
 func LookupUser(username string) (User, error) {
-	return lookupUser(func(u User) bool {
-		return u.Name == username
-	})
+	return lookupUser(username)
 }
 
 // LookupUid looks up a user by their user id in /etc/passwd. If the user cannot
 // be found (or there is no /etc/passwd file on the filesystem), then LookupId
 // returns an error.
 func LookupUid(uid int) (User, error) {
-	return lookupUser(func(u User) bool {
-		return u.Uid == uid
-	})
-}
-
-func lookupGroup(filter func(g Group) bool) (Group, error) {
-	// Get operating system-specific group reader-closer.
-	group, err := GetGroup()
-	if err != nil {
-		return Group{}, err
-	}
-	defer group.Close()
-
-	// Get the users.
-	groups, err := ParseGroupFilter(group, filter)
-	if err != nil {
-		return Group{}, err
-	}
-
-	// No user entries found.
-	if len(groups) == 0 {
-		return Group{}, ErrNoGroupEntries
-	}
-
-	// Assume the first entry is the "correct" one.
-	return groups[0], nil
+	return lookupUid(uid)
 }
 
 // LookupGroup looks up a group by its name in /etc/group. If the group cannot
 // be found (or there is no /etc/group file on the filesystem), then LookupGroup
 // returns an error.
 func LookupGroup(groupname string) (Group, error) {
-	return lookupGroup(func(g Group) bool {
-		return g.Name == groupname
-	})
+	return lookupGroup(groupname)
 }
 
 // LookupGid looks up a group by its group id in /etc/group. If the group cannot
 // be found (or there is no /etc/group file on the filesystem), then LookupGid
 // returns an error.
 func LookupGid(gid int) (Group, error) {
-	return lookupGroup(func(g Group) bool {
-		return g.Gid == gid
-	})
+	return lookupGid(gid)
 }

libcontainer/user/lookup_unix.go

@@ -15,6 +15,76 @@ const (
 	unixGroupPath  = "/etc/group"
 )
 
+func lookupUser(username string) (User, error) {
+	return lookupUserFunc(func(u User) bool {
+		return u.Name == username
+	})
+}
+
+func lookupUid(uid int) (User, error) {
+	return lookupUserFunc(func(u User) bool {
+		return u.Uid == uid
+	})
+}
+
+func lookupUserFunc(filter func(u User) bool) (User, error) {
+	// Get operating system-specific passwd reader-closer.
+	passwd, err := GetPasswd()
+	if err != nil {
+		return User{}, err
+	}
+	defer passwd.Close()
+
+	// Get the users.
+	users, err := ParsePasswdFilter(passwd, filter)
+	if err != nil {
+		return User{}, err
+	}
+
+	// No user entries found.
+	if len(users) == 0 {
+		return User{}, ErrNoPasswdEntries
+	}
+
+	// Assume the first entry is the "correct" one.
+	return users[0], nil
+}
+
+func lookupGroup(groupname string) (Group, error) {
+	return lookupGroupFunc(func(g Group) bool {
+		return g.Name == groupname
+	})
+}
+
+func lookupGid(gid int) (Group, error) {
+	return lookupGroupFunc(func(g Group) bool {
+		return g.Gid == gid
+	})
+}
+
+func lookupGroupFunc(filter func(g Group) bool) (Group, error) {
+	// Get operating system-specific group reader-closer.
+	group, err := GetGroup()
+	if err != nil {
+		return Group{}, err
+	}
+	defer group.Close()
+
+	// Get the users.
+	groups, err := ParseGroupFilter(group, filter)
+	if err != nil {
+		return Group{}, err
+	}
+
+	// No user entries found.
+	if len(groups) == 0 {
+		return Group{}, ErrNoGroupEntries
+	}
+
+	// Assume the first entry is the "correct" one.
+	return groups[0], nil
+}
+
 func GetPasswdPath() (string, error) {
 	return unixPasswdPath, nil
 }

libcontainer/user/lookup_windows.go

@@ -0,0 +1,40 @@
+// +build windows
+
+package user
+
+import (
+	"fmt"
+	"os/user"
+)
+
+func lookupUser(username string) (User, error) {
+	u, err := user.Lookup(username)
+	if err != nil {
+		return User{}, err
+	}
+	return userFromOS(u)
+}
+
+func lookupUid(uid int) (User, error) {
+	u, err := user.LookupId(fmt.Sprintf("%d", uid))
+	if err != nil {
+		return User{}, err
+	}
+	return userFromOS(u)
+}
+
+func lookupGroup(groupname string) (Group, error) {
+	g, err := user.LookupGroup(groupname)
+	if err != nil {
+		return Group{}, err
+	}
+	return groupFromOS(g)
+}
+
+func lookupGid(gid int) (Group, error) {
+	g, err := user.LookupGroupId(fmt.Sprintf("%d", gid))
+	if err != nil {
+		return Group{}, err
+	}
+	return groupFromOS(g)
+}

libcontainer/user/user.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/user"
 	"strconv"
 	"strings"
 )
@@ -28,6 +29,28 @@ type User struct {
 	Shell string
 }
 
+// userFromOS converts an os/user.(*User) to local User
+//
+// (This does not include Pass, Shell or Gecos)
+func userFromOS(u *user.User) (User, error) {
+	newUser := User{
+		Name: u.Username,
+		Home: u.HomeDir,
+	}
+	id, err := strconv.Atoi(u.Uid)
+	if err != nil {
+		return newUser, err
+	}
+	newUser.Uid = id
+
+	id, err = strconv.Atoi(u.Gid)
+	if err != nil {
+		return newUser, err
+	}
+	newUser.Gid = id
+	return newUser, nil
+}
+
 type Group struct {
 	Name string
 	Pass string
@@ -35,6 +58,23 @@ type Group struct {
 	List []string
 }
 
+// groupFromOS converts an os/user.(*Group) to local Group
+//
+// (This does not include Pass, Shell or Gecos)
+func groupFromOS(g *user.Group) (Group, error) {
+	newGroup := Group{
+		Name: g.Name,
+	}
+
+	id, err := strconv.Atoi(g.Gid)
+	if err != nil {
+		return newGroup, err
+	}
+	newGroup.Gid = id
+
+	return newGroup, nil
+}
+
 func parseLine(line string, v ...interface{}) {
 	if line == "" {
 		return