config: fix file/folder ownership

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

util/confutil/config.go

@@ -1,39 +1,143 @@
 package confutil
 
 import (
+	"crypto/rand"
+	"encoding/hex"
 	"os"
-	"path"
 	"path/filepath"
+	"sync"
 
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/docker/pkg/ioutils"
 	"github.com/pelletier/go-toml"
 	"github.com/pkg/errors"
-	"github.com/sirupsen/logrus"
+	fs "github.com/tonistiigi/fsutil/copy"
 )
 
-// ConfigDir will look for correct configuration store path;
-// if `$BUILDX_CONFIG` is set - use it, otherwise use parent directory
-// of Docker config file (i.e. `${DOCKER_CONFIG}/buildx`)
-func ConfigDir(dockerCli command.Cli) string {
-	if buildxConfig := os.Getenv("BUILDX_CONFIG"); buildxConfig != "" {
-		logrus.Debugf("using config store %q based in \"$BUILDX_CONFIG\" environment variable", buildxConfig)
-		return buildxConfig
-	}
+const defaultBuildKitConfigFile = "buildkitd.default.toml"
 
-	buildxConfig := filepath.Join(filepath.Dir(dockerCli.ConfigFile().Filename), "buildx")
-	logrus.Debugf("using default config store %q", buildxConfig)
-	return buildxConfig
+type Config struct {
+	dir     string
+	chowner *chowner
 }
 
-// DefaultConfigFile returns the default BuildKit configuration file path
-func DefaultConfigFile(dockerCli command.Cli) (string, bool) {
-	f := path.Join(ConfigDir(dockerCli), "buildkitd.default.toml")
+type chowner struct {
+	uid int
+	gid int
+}
+
+type ConfigOption func(*configOptions)
+
+type configOptions struct {
+	dir string
+}
+
+func WithDir(dir string) ConfigOption {
+	return func(o *configOptions) {
+		o.dir = dir
+	}
+}
+
+func NewConfig(dockerCli command.Cli, opts ...ConfigOption) *Config {
+	co := configOptions{}
+	for _, opt := range opts {
+		opt(&co)
+	}
+
+	configDir := co.dir
+	if configDir == "" {
+		configDir = os.Getenv("BUILDX_CONFIG")
+		if configDir == "" {
+			configDir = filepath.Join(filepath.Dir(dockerCli.ConfigFile().Filename), "buildx")
+		}
+	}
+
+	return &Config{
+		dir:     configDir,
+		chowner: sudoer(configDir),
+	}
+}
+
+// Dir will look for correct configuration store path;
+// if `$BUILDX_CONFIG` is set - use it, otherwise use parent directory
+// of Docker config file (i.e. `${DOCKER_CONFIG}/buildx`)
+func (c *Config) Dir() string {
+	return c.dir
+}
+
+// BuildKitConfigFile returns the default BuildKit configuration file path
+func (c *Config) BuildKitConfigFile() (string, bool) {
+	f := filepath.Join(c.dir, defaultBuildKitConfigFile)
 	if _, err := os.Stat(f); err == nil {
 		return f, true
 	}
 	return "", false
 }
 
+// MkdirAll creates a directory and all necessary parents within the config dir.
+func (c *Config) MkdirAll(dir string, perm os.FileMode) error {
+	var chown fs.Chowner
+	if c.chowner != nil {
+		chown = func(user *fs.User) (*fs.User, error) {
+			return &fs.User{UID: c.chowner.uid, GID: c.chowner.gid}, nil
+		}
+	}
+	d := filepath.Join(c.dir, dir)
+	st, err := os.Stat(d)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return fs.MkdirAll(d, perm, chown, nil)
+		}
+		return err
+	}
+	// if directory already exists, fix the owner if necessary
+	if c.chowner == nil {
+		return nil
+	}
+	currentOwner := fileOwner(st)
+	if currentOwner != nil && (currentOwner.uid != c.chowner.uid || currentOwner.gid != c.chowner.gid) {
+		return os.Chown(d, c.chowner.uid, c.chowner.gid)
+	}
+	return nil
+}
+
+// AtomicWriteFile writes data to a file within the config dir atomically
+func (c *Config) AtomicWriteFile(filename string, data []byte, perm os.FileMode) error {
+	f := filepath.Join(c.dir, filename)
+	if err := ioutils.AtomicWriteFile(f, data, perm); err != nil {
+		return err
+	}
+	if c.chowner == nil {
+		return nil
+	}
+	return os.Chown(f, c.chowner.uid, c.chowner.gid)
+}
+
+var nodeIdentifierMu sync.Mutex
+
+func (c *Config) TryNodeIdentifier() (out string) {
+	nodeIdentifierMu.Lock()
+	defer nodeIdentifierMu.Unlock()
+	sessionFilename := ".buildNodeID"
+	sessionFilepath := filepath.Join(c.Dir(), sessionFilename)
+	if _, err := os.Lstat(sessionFilepath); err != nil {
+		if os.IsNotExist(err) { // create a new file with stored randomness
+			b := make([]byte, 8)
+			if _, err := rand.Read(b); err != nil {
+				return out
+			}
+			if err := c.AtomicWriteFile(sessionFilename, []byte(hex.EncodeToString(b)), 0600); err != nil {
+				return out
+			}
+		}
+	}
+	dt, err := os.ReadFile(sessionFilepath)
+	if err == nil {
+		return string(dt)
+	}
+	return
+}
+
 // LoadConfigTree loads BuildKit config toml tree
 func LoadConfigTree(fp string) (*toml.Tree, error) {
 	f, err := os.Open(fp)

util/confutil/config_unix.go

@@ -0,0 +1,60 @@
+//go:build !windows
+// +build !windows
+
+package confutil
+
+import (
+	"os"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+// sudoer returns the user that invoked the current process with sudo only if
+// sudo HOME env matches the home directory of the user that ran sudo and is
+// part of configDir.
+func sudoer(configDir string) *chowner {
+	if _, ok := os.LookupEnv("SUDO_COMMAND"); !ok {
+		return nil
+	}
+	suidenv := os.Getenv("SUDO_UID") // https://www.sudo.ws/docs/man/sudo.man/#SUDO_UID
+	sgidenv := os.Getenv("SUDO_GID") // https://www.sudo.ws/docs/man/sudo.man/#SUDO_GID
+	if suidenv == "" || sgidenv == "" {
+		return nil
+	}
+	u, err := user.LookupId(suidenv)
+	if err != nil {
+		return nil
+	}
+	suid, err := strconv.Atoi(suidenv)
+	if err != nil {
+		return nil
+	}
+	sgid, err := strconv.Atoi(sgidenv)
+	if err != nil {
+		return nil
+	}
+	home, _ := os.UserHomeDir()
+	if home == "" || u.HomeDir != home {
+		return nil
+	}
+	if ok, _ := isSubPath(home, configDir); !ok {
+		return nil
+	}
+	return &chowner{uid: suid, gid: sgid}
+}
+
+func fileOwner(fi os.FileInfo) *chowner {
+	st := fi.Sys().(*syscall.Stat_t)
+	return &chowner{uid: int(st.Uid), gid: int(st.Gid)}
+}
+
+func isSubPath(basePath, subPath string) (bool, error) {
+	rel, err := filepath.Rel(basePath, subPath)
+	if err != nil {
+		return false, err
+	}
+	return !strings.HasPrefix(rel, "..") && rel != ".", nil
+}

util/confutil/config_unix_test.go

@@ -0,0 +1,58 @@
+//go:build !windows
+// +build !windows
+
+package confutil
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsSubPath(t *testing.T) {
+	tests := []struct {
+		name     string
+		basePath string
+		subPath  string
+		expected bool
+	}{
+		{
+			name:     "SubPath is a direct subdirectory",
+			basePath: "/home/user",
+			subPath:  "/home/user/docs",
+			expected: true,
+		},
+		{
+			name:     "SubPath is the same as basePath",
+			basePath: "/home/user",
+			subPath:  "/home/user",
+			expected: false,
+		},
+		{
+			name:     "SubPath is not a subdirectory",
+			basePath: "/home/user",
+			subPath:  "/home/otheruser",
+			expected: false,
+		},
+		{
+			name:     "SubPath is a nested subdirectory",
+			basePath: "/home/user",
+			subPath:  "/home/user/docs/reports",
+			expected: true,
+		},
+		{
+			name:     "SubPath is a sibling directory",
+			basePath: "/home/user",
+			subPath:  "/home/user2",
+			expected: false,
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			ok, err := isSubPath(tt.basePath, tt.subPath)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.expected, ok)
+		})
+	}
+}

util/confutil/config_windows.go

@@ -0,0 +1,11 @@
+package confutil
+
+import "os"
+
+func sudoer(_ string) *chowner {
+	return nil
+}
+
+func fileOwner(_ os.FileInfo) *chowner {
+	return nil
+}

util/confutil/node.go

@@ -1,34 +0,0 @@
-package confutil
-
-import (
-	"crypto/rand"
-	"encoding/hex"
-	"os"
-	"path/filepath"
-	"sync"
-)
-
-var nodeIdentifierMu sync.Mutex
-
-func TryNodeIdentifier(configDir string) (out string) {
-	nodeIdentifierMu.Lock()
-	defer nodeIdentifierMu.Unlock()
-	sessionFile := filepath.Join(configDir, ".buildNodeID")
-	if _, err := os.Lstat(sessionFile); err != nil {
-		if os.IsNotExist(err) { // create a new file with stored randomness
-			b := make([]byte, 8)
-			if _, err := rand.Read(b); err != nil {
-				return out
-			}
-			if err := os.WriteFile(sessionFile, []byte(hex.EncodeToString(b)), 0600); err != nil {
-				return out
-			}
-		}
-	}
-
-	dt, err := os.ReadFile(sessionFile)
-	if err == nil {
-		return string(dt)
-	}
-	return
-}