7 files changed, 721 insertions, 0 deletions
diff --git a/go/parabola_hackers/nslcd_backend/db_config.go b/go/parabola_hackers/nslcd_backend/db_config.go
new file mode 100644
index 0000000..556aa76
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/db_config.go
@@ -0,0 +1,39 @@
+// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	p "git.lukeshu.com/go/libnslcd/nslcd_proto"
+	s "golang.org/x/sys/unix"
+)
+
+func (o *Hackers) Config_Get(cred s.Ucred, req p.Request_Config_Get) <-chan p.Config {
+	o.lock.RLock()
+	ret := make(chan p.Config)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		switch req.Key {
+		case p.NSLCD_CONFIG_PAM_PASSWORD_PROHIBIT_MESSAGE:
+			if o.cfg.Pam_password_prohibit_message != "" {
+				ret <- p.Config{Value: o.cfg.Pam_password_prohibit_message}
+			}
+		}
+	}()
+	return ret
+}
diff --git a/go/parabola_hackers/nslcd_backend/db_group.go b/go/parabola_hackers/nslcd_backend/db_group.go
new file mode 100644
index 0000000..41f049e
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/db_group.go
@@ -0,0 +1,141 @@
+// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	"parabola_hackers"
+
+	p "git.lukeshu.com/go/libnslcd/nslcd_proto"
+	s "golang.org/x/sys/unix"
+)
+
+func (o *Hackers) groupByName(name string, users bool) p.Group {
+	members_set, found := o.groups[name]
+	if !found {
+		return p.Group{ID: -1}
+	}
+	gid := name2gid(name)
+	if gid < 0 {
+		return p.Group{ID: -1}
+	}
+	var members_list []string
+	if users {
+		members_list = parabola_hackers.Set2list(members_set)
+	} else {
+		members_list = make([]string, 0)
+	}
+	return p.Group{
+		Name:    name,
+		PwHash:  "x",
+		ID:      gid,
+		Members: members_list,
+	}
+}
+
+func (o *Hackers) groupByGid(gid int32, users bool) p.Group {
+	name, found := gid2name(gid)
+	if !found {
+		return p.Group{ID: -1}
+	}
+	members_set, found := o.groups[name]
+	if !found {
+		return p.Group{ID: -1}
+	}
+	var members_list []string
+	if users {
+		members_list = parabola_hackers.Set2list(members_set)
+	} else {
+		members_list = make([]string, 0)
+	}
+	return p.Group{
+		Name:    name,
+		PwHash:  "x",
+		ID:      gid,
+		Members: members_list,
+	}
+}
+
+func (o *Hackers) Group_ByName(cred s.Ucred, req p.Request_Group_ByName) <-chan p.Group {
+	o.lock.RLock()
+	ret := make(chan p.Group)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		group := o.groupByName(req.Name, true)
+		if group.ID < 0 {
+			return
+		}
+		ret <- group
+	}()
+	return ret
+}
+
+func (o *Hackers) Group_ByGid(cred s.Ucred, req p.Request_Group_ByGid) <-chan p.Group {
+	o.lock.RLock()
+	ret := make(chan p.Group)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		group := o.groupByGid(req.Gid, true)
+		if group.ID < 0 {
+			return
+		}
+		ret <- group
+	}()
+	return ret
+}
+
+// note that the BYMEMBER call returns an empty members list
+func (o *Hackers) Group_ByMember(cred s.Ucred, req p.Request_Group_ByMember) <-chan p.Group {
+	o.lock.RLock()
+	ret := make(chan p.Group)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		uid := o.name2uid(req.Member)
+		if uid < 0 {
+			return
+		}
+		for _, name := range o.users[uid].Groups {
+			group := o.groupByName(name, false)
+			if group.ID >= 0 {
+				ret <- group
+			}
+		}
+	}()
+	return ret
+}
+
+func (o *Hackers) Group_All(cred s.Ucred, req p.Request_Group_All) <-chan p.Group {
+	o.lock.RLock()
+	ret := make(chan p.Group)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		for name, _ := range o.groups {
+			group := o.groupByName(name, true)
+			if group.ID >= 0 {
+				ret <- group
+			}
+		}
+	}()
+	return ret
+}
diff --git a/go/parabola_hackers/nslcd_backend/db_pam.go b/go/parabola_hackers/nslcd_backend/db_pam.go
new file mode 100644
index 0000000..0538e70
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/db_pam.go
@@ -0,0 +1,202 @@
+// Copyright 2015-2016 Luke Shumaker <git.lukeshu@sbcglobal>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	"fmt"
+	"os"
+	"parabola_hackers"
+
+	s "golang.org/x/sys/unix"
+	p "git.lukeshu.com/go/libnslcd/nslcd_proto"
+
+	"git.lukeshu.com/go/libgnulinux/crypt"
+	"git.lukeshu.com/go/libsystemd/sd_daemon"
+)
+
+func checkPassword(password string, hash string) bool {
+	return crypt.Crypt(password, hash) == hash
+}
+
+func hashPassword(newPassword string, oldHash string) string {
+	salt := oldHash
+	if salt == "!" {
+		str, err := parabola_hackers.RandomString(crypt.SaltAlphabet, 8)
+		if err != nil {
+			sd_daemon.Log.Err("Could not generate a random string")
+			str = ""
+		}
+		salt = "$6$" + str + "$"
+	}
+	return crypt.Crypt(newPassword, salt)
+}
+
+func dirExists(path string) bool {
+	stat, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+	return stat.IsDir()
+}
+
+func (o *Hackers) PAM_Authentication(cred s.Ucred, req p.Request_PAM_Authentication) <-chan p.PAM_Authentication {
+	o.lock.RLock()
+	ret := make(chan p.PAM_Authentication)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		if len(req.UserName) == 0 && len(req.Password) == 0 && cred.Uid == 0 {
+			ret <- p.PAM_Authentication{
+				AuthenticationResult: p.NSLCD_PAM_SUCCESS,
+				UserName:             "",
+				AuthorizationResult:  p.NSLCD_PAM_SUCCESS,
+				AuthorizationError:   "",
+			}
+			return
+		}
+
+		uid := o.name2uid(req.UserName)
+		if uid < 0 {
+			return
+		}
+
+		user := o.users[uid]
+		obj := p.PAM_Authentication{
+			AuthenticationResult: p.NSLCD_PAM_AUTH_ERR,
+			UserName:             "",
+			AuthorizationResult:  p.NSLCD_PAM_AUTH_ERR,
+			AuthorizationError:   "",
+		}
+		if checkPassword(req.Password, user.Passwd.PwHash) {
+			obj.AuthenticationResult = p.NSLCD_PAM_SUCCESS
+			obj.AuthorizationResult = obj.AuthenticationResult
+			obj.UserName = user.Passwd.Name
+		}
+		ret <- obj
+	}()
+	return ret
+}
+
+func (o *Hackers) PAM_Authorization(cred s.Ucred, req p.Request_PAM_Authorization) <-chan p.PAM_Authorization {
+	o.lock.RLock()
+	ret := make(chan p.PAM_Authorization)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		uid := o.name2uid(req.UserName)
+		if uid < 0 {
+			return
+		}
+		ret <- p.PAM_Authorization{
+			Result: p.NSLCD_PAM_SUCCESS,
+			Error:  "",
+		}
+	}()
+	return ret
+}
+
+const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+
+func (o *Hackers) PAM_SessionOpen(cred s.Ucred, req p.Request_PAM_SessionOpen) <-chan p.PAM_SessionOpen {
+	ret := make(chan p.PAM_SessionOpen)
+	go func() {
+		defer close(ret)
+
+		sessionid, err := parabola_hackers.RandomString(alphabet, 24)
+		if err != nil {
+			return
+		}
+		ret <- p.PAM_SessionOpen{SessionID: sessionid}
+	}()
+	return ret
+}
+
+func (o *Hackers) PAM_SessionClose(cred s.Ucred, req p.Request_PAM_SessionClose) <-chan p.PAM_SessionClose {
+	ret := make(chan p.PAM_SessionClose)
+	go close(ret)
+	return ret
+}
+
+func (o *Hackers) PAM_PwMod(cred s.Ucred, req p.Request_PAM_PwMod) <-chan p.PAM_PwMod {
+	ret := make(chan p.PAM_PwMod)
+	o.lock.Lock()
+	go func() {
+		defer close(ret)
+		defer o.lock.Unlock()
+
+		uid := o.name2uid(req.UserName)
+		if uid < 0 {
+			return
+		}
+		user := o.users[uid]
+
+		// Check the OldPassword
+		if req.AsRoot == 1 && cred.Uid == 0 {
+			goto update
+		}
+		// special hack: if the old password is not
+		// set, but the home directory exists, let the
+		// user set their password
+		if user.Passwd.PwHash == "!" && dirExists(user.Passwd.HomeDir) {
+			goto update
+		}
+		if !checkPassword(req.OldPassword, user.Passwd.PwHash) {
+			ret <- p.PAM_PwMod{
+				Result: p.NSLCD_PAM_PERM_DENIED,
+				Error:  fmt.Sprintf("password change failed: %s", "Old password did not match"),
+			}
+			return
+		}
+	update:
+		if len(req.NewPassword) == 0 {
+			ret <- p.PAM_PwMod{
+				Result: p.NSLCD_PAM_PERM_DENIED,
+				Error:  "password cannot be empty",
+			}
+			return
+		}
+
+		// Update the PwHash in memory
+		user.Passwd.PwHash = hashPassword(req.NewPassword, user.Passwd.PwHash)
+		if len(user.Passwd.PwHash) == 0 {
+			sd_daemon.Log.Err("Password hashing failed")
+			return
+		}
+
+		// Update the PwHash on disk
+		passwords := make(map[string]string, len(o.users))
+		for _, ouser := range o.users {
+			passwords[ouser.Passwd.Name] = ouser.Passwd.PwHash
+		}
+		passwords[user.Passwd.Name] = user.Passwd.PwHash
+		err := parabola_hackers.SaveAllPasswords(passwords)
+		if err != nil {
+			sd_daemon.Log.Err(fmt.Sprintf("Writing passwords to disk: %v", err))
+			return
+		}
+
+		// Ok, we're done, commit the changes
+		o.users[uid] = user
+		ret <- p.PAM_PwMod{
+			Result: p.NSLCD_PAM_SUCCESS,
+			Error:  "",
+		}
+	}()
+	return ret
+}
diff --git a/go/parabola_hackers/nslcd_backend/db_passwd.go b/go/parabola_hackers/nslcd_backend/db_passwd.go
new file mode 100644
index 0000000..c5faf5c
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/db_passwd.go
@@ -0,0 +1,81 @@
+// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	p "git.lukeshu.com/go/libnslcd/nslcd_proto"
+	s "golang.org/x/sys/unix"
+)
+
+/* Note that the output password hash value should be one of:
+   <empty> - no password set, allow login without password
+   !       - used to prevent logins
+   x       - "valid" encrypted password that does not match any valid password
+             often used to indicate that the password is defined elsewhere
+   other   - encrypted password, in crypt(3) format */
+
+func (o *Hackers) Passwd_ByName(cred s.Ucred, req p.Request_Passwd_ByName) <-chan p.Passwd {
+	o.lock.RLock()
+	ret := make(chan p.Passwd)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		uid := o.name2uid(req.Name)
+		if uid < 0 {
+			return
+		}
+		passwd := o.users[uid].Passwd
+		passwd.PwHash = "x" // only put actual hashes in the Shadow DB
+		ret <- passwd
+	}()
+	return ret
+}
+
+func (o *Hackers) Passwd_ByUID(cred s.Ucred, req p.Request_Passwd_ByUID) <-chan p.Passwd {
+	o.lock.RLock()
+	ret := make(chan p.Passwd)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		user, found := o.users[req.UID]
+		if !found {
+			return
+		}
+		passwd := user.Passwd
+		passwd.PwHash = "x" // only put actual hashes in the Shadow DB
+		ret <- passwd
+	}()
+	return ret
+}
+
+func (o *Hackers) Passwd_All(cred s.Ucred, req p.Request_Passwd_All) <-chan p.Passwd {
+	o.lock.RLock()
+	ret := make(chan p.Passwd)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		for _, user := range o.users {
+			passwd := user.Passwd
+			passwd.PwHash = "x" // only put actual hashes in the Shadow DB
+			ret <- passwd
+		}
+	}()
+	return ret
+}
diff --git a/go/parabola_hackers/nslcd_backend/db_shadow.go b/go/parabola_hackers/nslcd_backend/db_shadow.go
new file mode 100644
index 0000000..58b13ec
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/db_shadow.go
@@ -0,0 +1,77 @@
+// Copyright 2015-2016 Luke Shumaker <git.lukeshu@sbcglobal>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	p "git.lukeshu.com/go/libnslcd/nslcd_proto"
+	s "golang.org/x/sys/unix"
+)
+
+func (o *Hackers) Shadow_ByName(cred s.Ucred, req p.Request_Shadow_ByName) <-chan p.Shadow {
+	o.lock.RLock()
+	ret := make(chan p.Shadow)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		if cred.Uid != 0 {
+			return
+		}
+		uid := o.name2uid(req.Name)
+		user := o.users[uid]
+		ret <- p.Shadow{
+			Name:           user.Passwd.Name,
+			PwHash:         user.Passwd.PwHash,
+			LastChangeDate: -1,
+			MinDays:        -1,
+			MaxDays:        -1,
+			WarnDays:       -1,
+			InactDays:      -1,
+			ExpireDate:     -1,
+			Flag:           -1,
+		}
+	}()
+	return ret
+}
+
+func (o *Hackers) Shadow_All(cred s.Ucred, req p.Request_Shadow_All) <-chan p.Shadow {
+	o.lock.RLock()
+	ret := make(chan p.Shadow)
+	go func() {
+		defer o.lock.RUnlock()
+		defer close(ret)
+
+		if cred.Uid != 0 {
+			return
+		}
+
+		for _, user := range o.users {
+			ret <- p.Shadow{
+				Name:           user.Passwd.Name,
+				PwHash:         user.Passwd.PwHash,
+				LastChangeDate: -1,
+				MinDays:        -1,
+				MaxDays:        -1,
+				WarnDays:       -1,
+				InactDays:      -1,
+				ExpireDate:     -1,
+				Flag:           -1,
+			}
+		}
+	}()
+	return ret
+}
diff --git a/go/parabola_hackers/nslcd_backend/hackers.go b/go/parabola_hackers/nslcd_backend/hackers.go
new file mode 100644
index 0000000..9cff815
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/hackers.go
@@ -0,0 +1,123 @@
+// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+// Package hackers_nslcd_backend is an nslcd_server Backend that
+// speaks to hackers.git.
+package hackers_nslcd_backend
+
+import (
+	"fmt"
+	"parabola_hackers"
+	"sync"
+
+	"git.lukeshu.com/go/libnslcd/nslcd_server"
+	"git.lukeshu.com/go/libnslcd/nslcd_systemd"
+	"git.lukeshu.com/go/libsystemd/sd_daemon"
+)
+
+type config struct {
+	Pam_password_prohibit_message string
+}
+
+type Hackers struct {
+	nslcd_server.NilBackend
+	lock sync.RWMutex
+
+	CfgFilename string
+
+	cfg    config
+	users  map[int32]parabola_hackers.User
+	groups map[string]map[string]bool
+}
+
+var _ nslcd_systemd.Backend = &Hackers{}
+var _ nslcd_server.Backend = &Hackers{}
+
+func (o *Hackers) Init() error {
+	sd_daemon.Log.Debug(fmt.Sprintf("hackers.git: CfgFilename = %v", o.CfgFilename))
+	err := o.Reload()
+	if err != nil {
+		sd_daemon.Log.Err(fmt.Sprintf("hackers.git: Could not initialize: %v", err))
+		return err
+	}
+	return nil
+}
+
+func (o *Hackers) Close() {
+	sd_daemon.Log.Info("hackers.git: Closing session")
+	o.lock.Lock()
+	defer o.lock.Unlock()
+
+	o.users = make(map[int32]parabola_hackers.User, 0)
+	o.groups = make(map[string]map[string]bool)
+}
+
+func (o *Hackers) Reload() error {
+	sd_daemon.Log.Info("hackers.git: Loading session")
+	o.lock.Lock()
+	defer o.lock.Unlock()
+
+	var err error
+	o.cfg, err = parse_config(o.CfgFilename)
+	if err != nil {
+		return err
+	}
+	sd_daemon.Log.Info(fmt.Sprintf("hackers.git: pam_password_prohibit_message: %#v", o.cfg.Pam_password_prohibit_message))
+
+	sd_daemon.Log.Debug("hackers.git: Parsing user data")
+	o.users, err = parabola_hackers.LoadAllUsers()
+	if err != nil {
+		return err
+	}
+
+	passwords, err := parabola_hackers.LoadAllPasswords()
+	if err != nil {
+		return err
+	}
+
+	o.groups = make(map[string]map[string]bool)
+	for uid, user := range o.users {
+		user.Passwd.GID = usersGid
+		hash, hasHash := passwords[user.Passwd.Name]
+		if !hasHash {
+			hash = "!"
+		}
+		user.Passwd.PwHash = hash
+		o.users[uid] = user
+		for _, groupname := range user.Groups {
+			o.add_user_to_group(user.Passwd.Name, groupname)
+		}
+	}
+	return nil
+}
+
+func (o *Hackers) name2uid(name string) int32 {
+	for uid, data := range o.users {
+		if data.Passwd.Name == name {
+			return uid
+		}
+	}
+	return -1
+}
+
+func (o *Hackers) add_user_to_group(username string, groupname string) {
+	group, found := o.groups[groupname]
+	if !found {
+		group = make(map[string]bool)
+		o.groups[groupname] = group
+	}
+	group[username] = true
+}
diff --git a/go/parabola_hackers/nslcd_backend/util.go b/go/parabola_hackers/nslcd_backend/util.go
new file mode 100644
index 0000000..a3b2b5d
--- /dev/null
+++ b/go/parabola_hackers/nslcd_backend/util.go
@@ -0,0 +1,58 @@
+// Copyright 2015-2016 Luke Shumaker <lukeshu@sbcglobal.net>.
+//
+// This is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// This software is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public
+// License along with this manual; if not, see
+// <http://www.gnu.org/licenses/>.
+
+package hackers_nslcd_backend
+
+import (
+	"io/ioutil"
+	"os"
+
+	yaml "gopkg.in/yaml.v2"
+	"git.lukeshu.com/go/libgnulinux/getgr"
+)
+
+func name2gid(name string) int32 {
+	gr, err := getgr.ByName(name)
+	if gr == nil || err != nil {
+		return -1
+	} else {
+		return int32(gr.Gid)
+	}
+}
+
+func gid2name(gid int32) (string, bool) {
+	gr, err := getgr.ByGid(gid)
+	if gr == nil || err != nil {
+		return "", false
+	} else {
+		return gr.Name, true
+	}
+}
+
+var usersGid = name2gid("users")
+
+func parse_config(filename string) (cfg config, err error) {
+	file, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	contents, err := ioutil.ReadAll(file)
+	if err != nil {
+		return
+	}
+	err = yaml.Unmarshal(contents, &cfg)
+	return
+}