280 lines
7.0 KiB
Go
280 lines
7.0 KiB
Go
package app
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import (
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"errors"
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"io/fs"
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"os/user"
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"path"
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"strconv"
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"git.ophivana.moe/security/fortify/dbus"
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"git.ophivana.moe/security/fortify/internal"
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"git.ophivana.moe/security/fortify/internal/fmsg"
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"git.ophivana.moe/security/fortify/internal/shim"
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"git.ophivana.moe/security/fortify/internal/state"
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"git.ophivana.moe/security/fortify/internal/system"
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)
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const (
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LaunchMethodSudo uint8 = iota
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LaunchMethodMachineCtl
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)
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var method = [...]string{
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LaunchMethodSudo: "sudo",
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LaunchMethodMachineCtl: "systemd",
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}
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var (
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ErrConfig = errors.New("no configuration to seal")
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ErrUser = errors.New("unknown user")
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ErrLaunch = errors.New("invalid launch method")
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ErrSudo = errors.New("sudo not available")
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ErrSystemd = errors.New("systemd not available")
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ErrMachineCtl = errors.New("machinectl not available")
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)
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// appSeal seals the application with child-related information
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type appSeal struct {
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// app unique ID string representation
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id string
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// wayland mediation, disabled if nil
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wl *shim.Wayland
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// freedesktop application ID
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fid string
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// argv to start process with in the final confined environment
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command []string
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// persistent process state store
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store state.Store
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// uint8 representation of launch method sealed from config
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launchOption uint8
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// process-specific share directory path
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share string
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// process-specific share directory path local to XDG_RUNTIME_DIR
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shareLocal string
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// path to launcher program
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toolPath string
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// pass-through enablement tracking from config
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et system.Enablements
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// prevents sharing from happening twice
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shared bool
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// seal system-level component
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sys *appSealSys
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internal.Paths
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// protected by upstream mutex
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}
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// Seal seals the app launch context
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func (a *app) Seal(config *Config) error {
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a.lock.Lock()
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defer a.lock.Unlock()
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if a.seal != nil {
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panic("app sealed twice")
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}
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if config == nil {
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return fmsg.WrapError(ErrConfig,
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"attempted to seal app with nil config")
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}
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// create seal
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seal := new(appSeal)
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// fetch system constants
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seal.Paths = a.os.Paths()
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// pass through config values
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seal.id = a.id.String()
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seal.fid = config.ID
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seal.command = config.Command
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// parses launch method text and looks up tool path
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switch config.Method {
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case method[LaunchMethodSudo]:
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seal.launchOption = LaunchMethodSudo
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if sudoPath, err := a.os.LookPath("sudo"); err != nil {
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return fmsg.WrapError(ErrSudo,
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"sudo not found")
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} else {
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seal.toolPath = sudoPath
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}
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case method[LaunchMethodMachineCtl]:
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seal.launchOption = LaunchMethodMachineCtl
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if !a.os.SdBooted() {
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return fmsg.WrapError(ErrSystemd,
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"system has not been booted with systemd as init system")
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}
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if machineCtlPath, err := a.os.LookPath("machinectl"); err != nil {
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return fmsg.WrapError(ErrMachineCtl,
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"machinectl not found")
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} else {
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seal.toolPath = machineCtlPath
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}
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default:
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return fmsg.WrapError(ErrLaunch,
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"invalid launch method")
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}
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// create seal system component
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seal.sys = new(appSealSys)
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// look up fortify executable path
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if p, err := a.os.Executable(); err != nil {
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return fmsg.WrapErrorSuffix(err, "cannot look up fortify executable path:")
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} else {
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seal.sys.executable = p
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}
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// look up user from system
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if u, err := a.os.Lookup(config.User); err != nil {
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if errors.As(err, new(user.UnknownUserError)) {
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return fmsg.WrapError(ErrUser, "unknown user", config.User)
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} else {
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// unreachable
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panic(err)
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}
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} else {
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seal.sys.user = u
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seal.sys.runtime = path.Join("/run/user", u.Uid)
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}
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// map sandbox config to bwrap
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if config.Confinement.Sandbox == nil {
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fmsg.VPrintln("sandbox configuration not supplied, PROCEED WITH CAUTION")
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// permissive defaults
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conf := &SandboxConfig{
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UserNS: true,
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Net: true,
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NoNewSession: true,
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}
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// bind entries in /
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if d, err := a.os.ReadDir("/"); err != nil {
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return err
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} else {
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b := make([]*FilesystemConfig, 0, len(d))
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for _, ent := range d {
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p := "/" + ent.Name()
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switch p {
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case "/proc":
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case "/dev":
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case "/run":
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case "/tmp":
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case "/mnt":
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case "/etc":
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b = append(b, &FilesystemConfig{Src: p, Dst: "/dev/fortify/etc", Write: false, Must: true})
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default:
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b = append(b, &FilesystemConfig{Src: p, Write: true, Must: true})
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}
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}
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conf.Filesystem = append(conf.Filesystem, b...)
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}
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// bind entries in /run
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if d, err := a.os.ReadDir("/run"); err != nil {
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return err
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} else {
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b := make([]*FilesystemConfig, 0, len(d))
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for _, ent := range d {
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name := ent.Name()
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switch name {
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case "user":
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case "dbus":
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default:
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p := "/run/" + name
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b = append(b, &FilesystemConfig{Src: p, Write: true, Must: true})
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}
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}
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conf.Filesystem = append(conf.Filesystem, b...)
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}
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// hide nscd from sandbox if present
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nscd := "/var/run/nscd"
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if _, err := a.os.Stat(nscd); !errors.Is(err, fs.ErrNotExist) {
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conf.Override = append(conf.Override, nscd)
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}
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// bind GPU stuff
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if config.Confinement.Enablements.Has(system.EX11) || config.Confinement.Enablements.Has(system.EWayland) {
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conf.Filesystem = append(conf.Filesystem, &FilesystemConfig{Src: "/dev/dri", Device: true})
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}
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// link host /etc to prevent passwd/group from being overwritten
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if d, err := a.os.ReadDir("/etc"); err != nil {
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return err
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} else {
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b := make([][2]string, 0, len(d))
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for _, ent := range d {
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name := ent.Name()
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switch name {
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case "passwd":
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case "group":
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case "mtab":
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b = append(b, [2]string{
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"/proc/mounts",
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"/etc/" + name,
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})
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default:
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b = append(b, [2]string{
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"/dev/fortify/etc/" + name,
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"/etc/" + name,
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})
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}
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}
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conf.Link = append(conf.Link, b...)
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}
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config.Confinement.Sandbox = conf
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}
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seal.sys.bwrap = config.Confinement.Sandbox.Bwrap()
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seal.sys.override = config.Confinement.Sandbox.Override
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if seal.sys.bwrap.SetEnv == nil {
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seal.sys.bwrap.SetEnv = make(map[string]string)
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}
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// create wayland struct and client wait channel if mediated wayland is enabled
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// this field being set enables mediated wayland setup later on
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if config.Confinement.Sandbox.Wayland {
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seal.wl = shim.NewWayland()
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}
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// open process state store
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// the simple store only starts holding an open file after first action
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// store activity begins after Start is called and must end before Wait
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seal.store = state.NewSimple(seal.RunDirPath, seal.sys.user.Uid)
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// parse string UID
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if u, err := strconv.Atoi(seal.sys.user.Uid); err != nil {
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// unreachable unless kernel bug
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panic("uid parse")
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} else {
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seal.sys.I = system.New(u)
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}
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// pass through enablements
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seal.et = config.Confinement.Enablements
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// this method calls all share methods in sequence
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if err := seal.shareAll([2]*dbus.Config{config.Confinement.SessionBus, config.Confinement.SystemBus}, a.os); err != nil {
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return err
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}
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// verbose log seal information
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fmsg.VPrintln("created application seal as user",
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seal.sys.user.Username, "("+seal.sys.user.Uid+"),",
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"method:", config.Method+",",
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"launcher:", seal.toolPath+",",
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"command:", config.Command)
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// seal app and release lock
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a.seal = seal
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return nil
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}
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