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users: eliminate nobody user memoization (#16904) 

This PR eliminates code specific to looking up and caching the uid/gid/user.User
object associated with the nobody user in an init block. This code existed before
adding the generic users cache and was meant to optimize the one search path we
knew would happen often. Now that we have the cache, seems reasonable to eliminate
this init block and use the cache instead like for any other user.

Also fixes a constraint on the podman (and other) drivers, where building without
CGO became problematic on some OS like Fedora IoT where the nobody user cannot
be found with the pure-Go standard library.

Fixes github.com/hashicorp/nomad-driver-podman/issues/228
This commit is contained in:
Seth Hoenig 2023-04-17 12:30:30 -05:00 committed by GitHub
parent ee071531de
commit 92d4a05534
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 9 additions and 65 deletions
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9
client/allocdir/fs_unix.go
View File

@ -43,14 +43,17 @@ func dropDirPermissions(path string, desired os.FileMode) error {
return nil
}
nobody := users.Nobody()
u, err := users.Lookup("nobody")
if err != nil {
return fmt.Errorf("Unable to find nobody user: %w", err)
}
uid, err := getUid(&nobody)
uid, err := getUid(u)
if err != nil {
return err
}
gid, err := getGid(&nobody)
gid, err := getGid(u)
if err != nil {
return err
}

10
helper/users/lookup_linux_test.go
View File

@ -43,12 +43,6 @@ func TestLookup_Linux(t *testing.T) {
}
}
func TestLookup_NobodyIDs(t *testing.T) {
uid, gid := NobodyIDs()
must.Eq(t, 65534, uid) // ubuntu
must.Eq(t, 65534, gid) // ubuntu
}
func TestWriteFileFor_Linux(t *testing.T) {
// This is really how you have to retrieve umask. See `man 2 umask`
umask := unix.Umask(0)
@ -93,7 +87,9 @@ func TestSocketFileFor_Linux(t *testing.T) {
ln, err := SocketFileFor(logger, path, "nobody")
must.NoError(t, err)
must.NotNil(t, ln)
defer ln.Close()
t.Cleanup(func() {
_ = ln.Close()
})
stat, err := os.Lstat(path)
must.NoError(t, err)

55
helper/users/lookup_unix.go
View File

@ -1,55 +0,0 @@
// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
//go:build unix
package users
import (
"fmt"
"os/user"
"strconv"
)
var (
// nobody is a cached copy of the nobody user, which is going to be looked-up
// frequently and is unlikely to be modified on the underlying system.
nobody user.User
// nobodyUID is a cached copy of the int value of the nobody user's UID.
nobodyUID uint32
// nobodyGID int is a cached copy of the int value of the nobody users's GID.
nobodyGID uint32
)
// Nobody returns User data for the "nobody" user on the system, bypassing the
// locking / file read / NSS lookup.
func Nobody() user.User {
return nobody
}
// NobodyIDs returns the integer UID and GID of the nobody user.
func NobodyIDs() (uint32, uint32) {
return nobodyUID, nobodyGID
}
func init() {
u, err := internalLookupUser("nobody")
if err != nil {
panic(fmt.Sprintf("failed to lookup nobody user: %v", err))
}
nobody = *u
uid, err := strconv.Atoi(u.Uid)
if err != nil {
panic(fmt.Sprintf("failed to parse nobody UID: %v", err))
}
gid, err := strconv.Atoi(u.Gid)
if err != nil {
panic(fmt.Sprintf("failed to parse nobody GID: %v", err))
}
nobodyUID, nobodyGID = uint32(uid), uint32(gid)
}