github.com/stolowski/snapd@v0.0.0-20210407085831-115137ce5a22/dirs/dirs.go

// -*- Mode: Go; indent-tabs-mode: t -*-

/*
 * Copyright (C) 2014-2015 Canonical Ltd
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program 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 program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package dirs

import (
	"fmt"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/snapcore/snapd/release"
)

// the various file paths
var (
	GlobalRootDir string

	SnapMountDir string

	DistroLibExecDir string

	SnapBlobDir               string
	SnapDataDir               string
	SnapDataHomeGlob          string
	SnapDownloadCacheDir      string
	SnapAppArmorDir           string
	SnapAppArmorAdditionalDir string
	SnapConfineAppArmorDir    string
	SnapSeccompBase           string
	SnapSeccompDir            string
	SnapMountPolicyDir        string
	SnapUdevRulesDir          string
	SnapKModModulesDir        string
	LocaleDir                 string
	SnapMetaDir               string
	SnapdSocket               string
	SnapSocket                string
	SnapRunDir                string
	SnapRunNsDir              string
	SnapRunLockDir            string
	SnapBootstrapRunDir       string

	SnapdMaintenanceFile string

	SnapdStoreSSLCertsDir string

	SnapSeedDir   string
	SnapDeviceDir string

	SnapAssertsDBDir      string
	SnapCookieDir         string
	SnapTrustedAccountKey string
	SnapAssertsSpoolDir   string
	SnapSeqDir            string

	SnapStateFile     string
	SnapSystemKeyFile string

	SnapRepairDir        string
	SnapRepairStateFile  string
	SnapRepairRunDir     string
	SnapRepairAssertsDir string
	SnapRunRepairDir     string

	SnapRollbackDir string

	SnapCacheDir        string
	SnapNamesFile       string
	SnapSectionsFile    string
	SnapCommandsDB      string
	SnapAuxStoreInfoDir string

	SnapBinariesDir     string
	SnapServicesDir     string
	SnapUserServicesDir string
	SnapSystemdConfDir  string
	SnapDesktopFilesDir string
	SnapDesktopIconsDir string

	SnapDBusSessionPolicyDir   string
	SnapDBusSystemPolicyDir    string
	SnapDBusSessionServicesDir string
	SnapDBusSystemServicesDir  string

	SnapModeenvFile   string
	SnapBootAssetsDir string
	SnapFDEDir        string
	SnapSaveDir       string
	SnapDeviceSaveDir string

	CloudMetaDataFile     string
	CloudInstanceDataFile string

	ClassicDir string

	XdgRuntimeDirBase string
	XdgRuntimeDirGlob string

	CompletionHelperInCore string
	CompletersDir          string

	SystemFontsDir            string
	SystemLocalFontsDir       string
	SystemFontconfigCacheDirs []string

	SnapshotsDir string

	ErrtrackerDbDir string
	SysfsDir        string

	FeaturesDir string
)

const (
	defaultSnapMountDir = "/snap"

	// These are directories which are static inside the core snap and
	// can never be prefixed as they will be always absolute once we
	// are in the snap confinement environment.
	CoreLibExecDir   = "/usr/lib/snapd"
	CoreSnapMountDir = "/snap"

	// Directory with snap data inside user's home
	UserHomeSnapDir = "snap"

	// LocalInstallBlobTempPrefix is used by local install code:
	// * in daemon to spool the snap file to <SnapBlobDir>/<LocalInstallBlobTempPrefix>*
	// * in snapstate to auto-cleans them up using the same prefix
	LocalInstallBlobTempPrefix = ".local-install-"
)

var (
	// not exported because it does not honor the global rootdir
	snappyDir = filepath.Join("var", "lib", "snapd")

	callbacks = []func(string){}
)

func init() {
	// init the global directories at startup
	root := os.Getenv("SNAPPY_GLOBAL_ROOT")

	SetRootDir(root)
}

// StripRootDir strips the custom global root directory from the specified argument.
func StripRootDir(dir string) string {
	if !filepath.IsAbs(dir) {
		panic(fmt.Sprintf("supplied path is not absolute %q", dir))
	}
	if !strings.HasPrefix(dir, GlobalRootDir) {
		panic(fmt.Sprintf("supplied path is not related to global root %q", dir))
	}
	result, err := filepath.Rel(GlobalRootDir, dir)
	if err != nil {
		panic(err)
	}
	return "/" + result
}

// SupportsClassicConfinement returns true if the current directory layout supports classic confinement.
func SupportsClassicConfinement() bool {
	// Core systems don't support classic confinement as a policy decision.
	if !release.OnClassic {
		return false
	}

	// Classic systems support classic confinement if using the primary mount
	// location for snaps, that is /snap or if using the alternate mount
	// location, /var/lib/snapd/snap along with the /snap ->
	// /var/lib/snapd/snap symlink in place.
	smd := filepath.Join(GlobalRootDir, defaultSnapMountDir)
	if SnapMountDir == smd {
		return true
	}
	fi, err := os.Lstat(smd)
	if err == nil && fi.Mode()&os.ModeSymlink != 0 {
		if target, err := filepath.EvalSymlinks(smd); err == nil {
			if target == SnapMountDir {
				return true
			}
		}
	}

	return false
}

var metaSnapPath = "/meta/snap.yaml"

// isInsideBaseSnap returns true if the process is inside a base snap environment.
//
// The things that count as a base snap are:
// - any base snap mounted at /
// - any os snap mounted at /
func isInsideBaseSnap() (bool, error) {
	_, err := os.Stat(metaSnapPath)
	if err != nil && os.IsNotExist(err) {
		return false, nil
	}
	return err == nil, err
}

// SnapdStateDir returns the path to /var/lib/snapd dir under rootdir.
func SnapdStateDir(rootdir string) string {
	return filepath.Join(rootdir, snappyDir)
}

// SnapBlobDirUnder returns the path to the snap blob dir under rootdir.
func SnapBlobDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "snaps")
}

// SnapSeedDirUnder returns the path to the snap seed dir under rootdir.
func SnapSeedDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "seed")
}

// SnapStateFileUnder returns the path to snapd state file under rootdir.
func SnapStateFileUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "state.json")
}

// SnapModeenvFileUnder returns the path to the modeenv file under rootdir.
func SnapModeenvFileUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "modeenv")
}

// FeaturesDirUnder returns the path to the features dir under rootdir.
func FeaturesDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "features")
}

// SnapSystemdConfDirUnder returns the path to the systemd conf dir under
// rootdir.
func SnapSystemdConfDirUnder(rootdir string) string {
	return filepath.Join(rootdir, "/etc/systemd/system.conf.d")
}

// SnapBootAssetsDirUnder returns the path to boot assets directory under a
// rootdir.
func SnapBootAssetsDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "boot-assets")
}

// SnapDeviceDirUnder returns the path to device directory under rootdir.
func SnapDeviceDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "device")
}

// SnapFDEDirUnder returns the path to full disk encryption state directory
// under rootdir.
func SnapFDEDirUnder(rootdir string) string {
	return filepath.Join(SnapDeviceDirUnder(rootdir), "fde")
}

// SnapSaveDirUnder returns the path to device save directory under rootdir.
func SnapSaveDirUnder(rootdir string) string {
	return filepath.Join(rootdir, snappyDir, "save")
}

// SnapFDEDirUnderSave returns the path to full disk encryption state directory
// inside the given save tree dir.
func SnapFDEDirUnderSave(savedir string) string {
	return filepath.Join(savedir, "device/fde")
}

// AddRootDirCallback registers a callback for whenever the global root
// directory (set by SetRootDir) is changed to enable updates to variables in
// other packages that depend on its location.
func AddRootDirCallback(c func(string)) {
	callbacks = append(callbacks, c)
}

// SetRootDir allows settings a new global root directory, this is useful
// for e.g. chroot operations
func SetRootDir(rootdir string) {
	if rootdir == "" {
		rootdir = "/"
	}
	GlobalRootDir = rootdir

	altDirDistros := []string{
		"antergos",
		"arch",
		"archlinux",
		"fedora",
		"gentoo",
		"manjaro",
		"manjaro-arm",
	}

	isInsideBase, _ := isInsideBaseSnap()
	if !isInsideBase && release.DistroLike(altDirDistros...) {
		SnapMountDir = filepath.Join(rootdir, "/var/lib/snapd/snap")
	} else {
		SnapMountDir = filepath.Join(rootdir, defaultSnapMountDir)
	}

	SnapDataDir = filepath.Join(rootdir, "/var/snap")
	SnapDataHomeGlob = filepath.Join(rootdir, "/home/*/", UserHomeSnapDir)
	SnapAppArmorDir = filepath.Join(rootdir, snappyDir, "apparmor", "profiles")
	SnapConfineAppArmorDir = filepath.Join(rootdir, snappyDir, "apparmor", "snap-confine")
	SnapAppArmorAdditionalDir = filepath.Join(rootdir, snappyDir, "apparmor", "additional")
	SnapDownloadCacheDir = filepath.Join(rootdir, snappyDir, "cache")
	SnapSeccompBase = filepath.Join(rootdir, snappyDir, "seccomp")
	SnapSeccompDir = filepath.Join(SnapSeccompBase, "bpf")
	SnapMountPolicyDir = filepath.Join(rootdir, snappyDir, "mount")
	SnapMetaDir = filepath.Join(rootdir, snappyDir, "meta")
	SnapdMaintenanceFile = filepath.Join(rootdir, snappyDir, "maintenance.json")
	SnapBlobDir = SnapBlobDirUnder(rootdir)
	// ${snappyDir}/desktop is added to $XDG_DATA_DIRS.
	// Subdirectories are interpreted according to the relevant
	// freedesktop.org specifications
	SnapDesktopFilesDir = filepath.Join(rootdir, snappyDir, "desktop", "applications")
	SnapDesktopIconsDir = filepath.Join(rootdir, snappyDir, "desktop", "icons")
	SnapRunDir = filepath.Join(rootdir, "/run/snapd")
	SnapRunNsDir = filepath.Join(SnapRunDir, "/ns")
	SnapRunLockDir = filepath.Join(SnapRunDir, "/lock")

	SnapBootstrapRunDir = filepath.Join(SnapRunDir, "snap-bootstrap")

	SnapdStoreSSLCertsDir = filepath.Join(rootdir, snappyDir, "ssl/store-certs")

	// keep in sync with the debian/snapd.socket file:
	SnapdSocket = filepath.Join(rootdir, "/run/snapd.socket")
	SnapSocket = filepath.Join(rootdir, "/run/snapd-snap.socket")

	SnapAssertsDBDir = filepath.Join(rootdir, snappyDir, "assertions")
	SnapCookieDir = filepath.Join(rootdir, snappyDir, "cookie")
	SnapAssertsSpoolDir = filepath.Join(rootdir, "run/snapd/auto-import")
	SnapSeqDir = filepath.Join(rootdir, snappyDir, "sequence")

	SnapStateFile = SnapStateFileUnder(rootdir)
	SnapSystemKeyFile = filepath.Join(rootdir, snappyDir, "system-key")

	SnapCacheDir = filepath.Join(rootdir, "/var/cache/snapd")
	SnapNamesFile = filepath.Join(SnapCacheDir, "names")
	SnapSectionsFile = filepath.Join(SnapCacheDir, "sections")
	SnapCommandsDB = filepath.Join(SnapCacheDir, "commands.db")
	SnapAuxStoreInfoDir = filepath.Join(SnapCacheDir, "aux")

	SnapSeedDir = SnapSeedDirUnder(rootdir)
	SnapDeviceDir = SnapDeviceDirUnder(rootdir)

	SnapModeenvFile = SnapModeenvFileUnder(rootdir)
	SnapBootAssetsDir = SnapBootAssetsDirUnder(rootdir)
	SnapFDEDir = SnapFDEDirUnder(rootdir)
	SnapSaveDir = SnapSaveDirUnder(rootdir)
	SnapDeviceSaveDir = filepath.Join(SnapSaveDir, "device")

	SnapRepairDir = filepath.Join(rootdir, snappyDir, "repair")
	SnapRepairStateFile = filepath.Join(SnapRepairDir, "repair.json")
	SnapRepairRunDir = filepath.Join(SnapRepairDir, "run")
	SnapRepairAssertsDir = filepath.Join(SnapRepairDir, "assertions")
	SnapRunRepairDir = filepath.Join(SnapRunDir, "repair")

	SnapRollbackDir = filepath.Join(rootdir, snappyDir, "rollback")

	SnapBinariesDir = filepath.Join(SnapMountDir, "bin")
	SnapServicesDir = filepath.Join(rootdir, "/etc/systemd/system")
	SnapUserServicesDir = filepath.Join(rootdir, "/etc/systemd/user")
	SnapSystemdConfDir = SnapSystemdConfDirUnder(rootdir)

	SnapDBusSystemPolicyDir = filepath.Join(rootdir, "/etc/dbus-1/system.d")
	SnapDBusSessionPolicyDir = filepath.Join(rootdir, "/etc/dbus-1/session.d")
	// Use 'dbus-1/services' and `dbus-1/system-services' to mirror
	// '/usr/share/dbus-1' hierarchy.
	SnapDBusSessionServicesDir = filepath.Join(rootdir, snappyDir, "dbus-1", "services")
	SnapDBusSystemServicesDir = filepath.Join(rootdir, snappyDir, "dbus-1", "system-services")

	CloudInstanceDataFile = filepath.Join(rootdir, "/run/cloud-init/instance-data.json")

	SnapUdevRulesDir = filepath.Join(rootdir, "/etc/udev/rules.d")

	SnapKModModulesDir = filepath.Join(rootdir, "/etc/modules-load.d/")

	LocaleDir = filepath.Join(rootdir, "/usr/share/locale")
	ClassicDir = filepath.Join(rootdir, "/writable/classic")

	opensuseTWWithLibexec := func() bool {
		// XXX: this is pretty naive if openSUSE ever starts going back
		// and forth about the change
		if !release.DistroLike("opensuse-tumbleweed") {
			return false
		}
		v, err := strconv.Atoi(release.ReleaseInfo.VersionID)
		if err != nil {
			// nothing we can do here
			return false
		}
		// first seen on snapshot "20200826"
		if v < 20200826 {
			return false
		}
		return true
	}

	if release.DistroLike("fedora") || opensuseTWWithLibexec() {
		// RHEL, CentOS, Fedora and derivatives, some more recent
		// snapshots of openSUSE Tumbleweed;
		// both RHEL and CentOS list "fedora" in ID_LIKE
		DistroLibExecDir = filepath.Join(rootdir, "/usr/libexec/snapd")
	} else {
		DistroLibExecDir = filepath.Join(rootdir, "/usr/lib/snapd")
	}

	XdgRuntimeDirBase = filepath.Join(rootdir, "/run/user")
	XdgRuntimeDirGlob = filepath.Join(XdgRuntimeDirBase, "*/")

	CompletionHelperInCore = filepath.Join(CoreLibExecDir, "etelpmoc.sh")
	CompletersDir = filepath.Join(rootdir, "/usr/share/bash-completion/completions/")

	// These paths agree across all supported distros
	SystemFontsDir = filepath.Join(rootdir, "/usr/share/fonts")
	SystemLocalFontsDir = filepath.Join(rootdir, "/usr/local/share/fonts")
	// The cache path is true for Ubuntu, Debian, openSUSE, Arch
	SystemFontconfigCacheDirs = []string{filepath.Join(rootdir, "/var/cache/fontconfig")}
	if release.DistroLike("fedora") && !release.DistroLike("amzn") {
		// Applies to Fedora and CentOS, Amazon Linux 2 is behind with
		// updates to fontconfig and uses /var/cache/fontconfig instead,
		// see:
		// https://fedoraproject.org/wiki/Changes/FontconfigCacheDirChange
		// https://bugzilla.redhat.com/show_bug.cgi?id=1416380
		// https://bugzilla.redhat.com/show_bug.cgi?id=1377367
		//
		// However, snaps may still use older libfontconfig, which fails
		// to parse the new config and defaults to
		// /var/cache/fontconfig. In this case we need to make both
		// locations available
		SystemFontconfigCacheDirs = append(SystemFontconfigCacheDirs, filepath.Join(rootdir, "/usr/lib/fontconfig/cache"))
	}

	SnapshotsDir = filepath.Join(rootdir, snappyDir, "snapshots")

	ErrtrackerDbDir = filepath.Join(rootdir, snappyDir, "errtracker.db")
	SysfsDir = filepath.Join(rootdir, "/sys")

	FeaturesDir = FeaturesDirUnder(rootdir)

	// call the callbacks last so that the callbacks can just reference the
	// global vars if they want, instead of using the new rootdir directly
	for _, c := range callbacks {
		c(rootdir)
	}
}

// what inside a (non-classic) snap is /usr/lib/snapd, outside can come from different places
func libExecOutside(base string) string {
	if base == "" {
		// no explicit base; core is it
		return filepath.Join(SnapMountDir, "core/current/usr/lib/snapd")
	}
	// if a base is set, libexec comes from the snapd snap if it's
	// installed, and otherwise from the distro.
	p := filepath.Join(SnapMountDir, "snapd/current/usr/lib/snapd")
	if st, err := os.Stat(p); err == nil && st.IsDir() {
		return p
	}
	return DistroLibExecDir
}

func CompleteShPath(base string) string {
	return filepath.Join(libExecOutside(base), "complete.sh")
}

func IsCompleteShSymlink(compPath string) bool {
	target, err := os.Readlink(compPath)
	// check if the target paths ends with "/snapd/complete.sh"
	return err == nil && filepath.Base(filepath.Dir(target)) == "snapd" && filepath.Base(target) == "complete.sh"
}