Migrate enki from osbuilder

Signed-off-by: Dimitris Karakasilis <dimitris@karakasilis.me>

pkg/utils/chroot.go

@@ -0,0 +1,218 @@
+/*
+Copyright © 2022 SUSE LLC
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package utils
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+
+	"github.com/kairos-io/enki/pkg/constants"
+	v1 "github.com/kairos-io/kairos-agent/v2/pkg/types/v1"
+)
+
+// Chroot represents the struct that will allow us to run commands inside a given chroot
+type Chroot struct {
+	path          string
+	defaultMounts []string
+	extraMounts   map[string]string
+	activeMounts  []string
+	config        *v1.Config
+}
+
+func NewChroot(path string, config *v1.Config) *Chroot {
+	return &Chroot{
+		path:          path,
+		defaultMounts: []string{"/dev", "/dev/pts", "/proc", "/sys"},
+		extraMounts:   map[string]string{},
+		activeMounts:  []string{},
+		config:        config,
+	}
+}
+
+// ChrootedCallback runs the given callback in a chroot environment
+func ChrootedCallback(cfg *v1.Config, path string, bindMounts map[string]string, callback func() error) error {
+	chroot := NewChroot(path, cfg)
+	chroot.SetExtraMounts(bindMounts)
+	return chroot.RunCallback(callback)
+}
+
+// Sets additional bind mounts for the chroot enviornment. They are represented
+// in a map where the key is the path outside the chroot and the value is the
+// path inside the chroot.
+func (c *Chroot) SetExtraMounts(extraMounts map[string]string) {
+	c.extraMounts = extraMounts
+}
+
+// Prepare will mount the defaultMounts as bind mounts, to be ready when we run chroot
+func (c *Chroot) Prepare() error {
+	var err error
+	keys := []string{}
+	mountOptions := []string{"bind"}
+
+	if len(c.activeMounts) > 0 {
+		return errors.New("There are already active mountpoints for this instance")
+	}
+
+	defer func() {
+		if err != nil {
+			c.Close()
+		}
+	}()
+
+	for _, mnt := range c.defaultMounts {
+		mountPoint := fmt.Sprintf("%s%s", strings.TrimSuffix(c.path, "/"), mnt)
+		err = MkdirAll(c.config.Fs, mountPoint, constants.DirPerm)
+		if err != nil {
+			return err
+		}
+		err = c.config.Mounter.Mount(mnt, mountPoint, "bind", mountOptions)
+		if err != nil {
+			return err
+		}
+		c.activeMounts = append(c.activeMounts, mountPoint)
+	}
+
+	for k := range c.extraMounts {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	for _, k := range keys {
+		mountPoint := fmt.Sprintf("%s%s", strings.TrimSuffix(c.path, "/"), c.extraMounts[k])
+		err = MkdirAll(c.config.Fs, mountPoint, constants.DirPerm)
+		if err != nil {
+			return err
+		}
+		err = c.config.Mounter.Mount(k, mountPoint, "bind", mountOptions)
+		if err != nil {
+			return err
+		}
+		c.activeMounts = append(c.activeMounts, mountPoint)
+	}
+
+	return nil
+}
+
+// Close will unmount all active mounts created in Prepare on reverse order
+func (c *Chroot) Close() error {
+	failures := []string{}
+	for len(c.activeMounts) > 0 {
+		curr := c.activeMounts[len(c.activeMounts)-1]
+		c.config.Logger.Debugf("Unmounting %s from chroot", curr)
+		c.activeMounts = c.activeMounts[:len(c.activeMounts)-1]
+		err := c.config.Mounter.Unmount(curr)
+		if err != nil {
+			c.config.Logger.Errorf("Error unmounting %s: %s", curr, err)
+			failures = append(failures, curr)
+		}
+	}
+	if len(failures) > 0 {
+		c.activeMounts = failures
+		return fmt.Errorf("failed closing chroot environment. Unmount failures: %v", failures)
+	}
+	return nil
+}
+
+// RunCallback runs the given callback in a chroot environment
+func (c *Chroot) RunCallback(callback func() error) (err error) {
+	var currentPath string
+	var oldRootF *os.File
+
+	// Store current path
+	currentPath, err = os.Getwd()
+	if err != nil {
+		c.config.Logger.Error("Failed to get current path")
+		return err
+	}
+	defer func() {
+		tmpErr := os.Chdir(currentPath)
+		if err == nil && tmpErr != nil {
+			err = tmpErr
+		}
+	}()
+
+	// Store current root
+	oldRootF, err = c.config.Fs.Open("/")
+	if err != nil {
+		c.config.Logger.Errorf("Can't open current root")
+		return err
+	}
+	defer oldRootF.Close()
+
+	if len(c.activeMounts) == 0 {
+		err = c.Prepare()
+		if err != nil {
+			c.config.Logger.Errorf("Can't mount default mounts")
+			return err
+		}
+		defer func() {
+			tmpErr := c.Close()
+			if err == nil {
+				err = tmpErr
+			}
+		}()
+	}
+	// Change to new dir before running chroot!
+	err = c.config.Syscall.Chdir(c.path)
+	if err != nil {
+		c.config.Logger.Errorf("Can't chdir %s: %s", c.path, err)
+		return err
+	}
+
+	err = c.config.Syscall.Chroot(c.path)
+	if err != nil {
+		c.config.Logger.Errorf("Can't chroot %s: %s", c.path, err)
+		return err
+	}
+
+	// Restore to old root
+	defer func() {
+		tmpErr := oldRootF.Chdir()
+		if tmpErr != nil {
+			c.config.Logger.Errorf("Can't change to old root dir")
+			if err == nil {
+				err = tmpErr
+			}
+		} else {
+			tmpErr = c.config.Syscall.Chroot(".")
+			if tmpErr != nil {
+				c.config.Logger.Errorf("Can't chroot back to old root")
+				if err == nil {
+					err = tmpErr
+				}
+			}
+		}
+	}()
+
+	return callback()
+}
+
+// Run executes a command inside a chroot
+func (c *Chroot) Run(command string, args ...string) (out []byte, err error) {
+	callback := func() error {
+		out, err = c.config.Runner.Run(command, args...)
+		return err
+	}
+	err = c.RunCallback(callback)
+	if err != nil {
+		c.config.Logger.Errorf("Cant run command %s with args %v on chroot: %s", command, args, err)
+		c.config.Logger.Debugf("Output from command: %s", out)
+	}
+	return out, err
+}