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package app
import (
"errors"
"fmt"
"os"
"os/exec"
"path"
"git.ophivana.moe/cat/fortify/acl"
"git.ophivana.moe/cat/fortify/dbus"
"git.ophivana.moe/cat/fortify/internal/state"
"git.ophivana.moe/cat/fortify/internal/verbose"
)
const (
dbusSessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
dbusSystemBusAddress = "DBUS_SYSTEM_BUS_ADDRESS"
xdgDBusProxy = "xdg-dbus-proxy"
)
var (
ErrDBusConfig = errors.New("dbus config not supplied")
ErrDBusProxy = errors.New(xdgDBusProxy + " not found")
)
type (
SealDBusError BaseError
LookupDBusError BaseError
StartDBusError BaseError
CloseDBusError BaseError
)
func (seal *appSeal) shareDBus(config [2]*dbus.Config) error {
if !seal.et.Has(state.EnableDBus) {
return nil
}
// session bus is mandatory
if config[0] == nil {
return (*SealDBusError)(wrapError(ErrDBusConfig, "attempted to seal session bus proxy with nil config"))
}
// system bus is optional
seal.sys.dbusSystem = config[1] != nil
// upstream address, downstream socket path
var sessionBus, systemBus [2]string
// downstream socket paths
sessionBus[1] = path.Join(seal.share, "bus")
systemBus[1] = path.Join(seal.share, "system_bus_socket")
// resolve upstream session bus address
if addr, ok := os.LookupEnv(dbusSessionBusAddress); !ok {
// fall back to default format
sessionBus[0] = fmt.Sprintf("unix:path=/run/user/%d/bus", os.Getuid())
} else {
sessionBus[0] = addr
}
// resolve upstream system bus address
if addr, ok := os.LookupEnv(dbusSystemBusAddress); !ok {
// fall back to default hardcoded value
systemBus[0] = "unix:path=/run/dbus/system_bus_socket"
} else {
systemBus[0] = addr
}
// look up proxy program path for dbus.New
if b, err := exec.LookPath(xdgDBusProxy); err != nil {
return (*LookupDBusError)(wrapError(ErrDBusProxy, xdgDBusProxy, "not found"))
} else {
// create proxy instance
seal.sys.dbus = dbus.New(b, sessionBus, systemBus)
}
// seal dbus proxy
if err := seal.sys.dbus.Seal(config[0], config[1]); err != nil {
return (*SealDBusError)(wrapError(err, "cannot seal message bus proxy:", err))
}
// store addresses for cleanup and logging
seal.sys.dbusAddr = &[2][2]string{sessionBus, systemBus}
// share proxy sockets
seal.appendEnv(dbusSessionBusAddress, "unix:path="+sessionBus[1])
seal.sys.updatePerm(sessionBus[1], acl.Read, acl.Write)
if seal.sys.dbusSystem {
seal.appendEnv(dbusSystemBusAddress, "unix:path="+systemBus[1])
seal.sys.updatePerm(systemBus[1], acl.Read, acl.Write)
}
return nil
}
func (tx *appSealTx) startDBus() error {
// ready channel passed to dbus package
ready := make(chan error, 1)
// used by waiting goroutine to notify process return
tx.dbusWait = make(chan struct{})
// background dbus proxy start
if err := tx.dbus.Start(ready, os.Stderr); err != nil {
return (*StartDBusError)(wrapError(err, "cannot start message bus proxy:", err))
}
verbose.Println("starting message bus proxy:", tx.dbus)
// background wait for proxy instance and notify completion
go func() {
if err := tx.dbus.Wait(); err != nil {
fmt.Println("fortify: warn: message bus proxy returned error:", err)
} else {
verbose.Println("message bus proxy exit")
}
// ensure socket removal so ephemeral directory is empty at revert
if err := os.Remove(tx.dbusAddr[0][1]); err != nil && !errors.Is(err, os.ErrNotExist) {
fmt.Println("fortify: cannot remove dangling session bus socket:", err)
}
if tx.dbusSystem {
if err := os.Remove(tx.dbusAddr[1][1]); err != nil && !errors.Is(err, os.ErrNotExist) {
fmt.Println("fortify: cannot remove dangling system bus socket:", err)
}
}
// notify proxy completion
tx.dbusWait <- struct{}{}
}()
// ready is not nil if the proxy process faulted
if err := <-ready; err != nil {
// note that err here is either an I/O related error or a predetermined unexpected behaviour error
return (*StartDBusError)(wrapError(err, "message bus proxy fault after start:", err))
}
verbose.Println("message bus proxy ready")
return nil
}
func (tx *appSealTx) stopDBus() error {
if err := tx.dbus.Close(); err != nil {
if errors.Is(err, os.ErrClosed) {
return (*CloseDBusError)(wrapError(err, "message bus proxy already closed"))
} else {
return (*CloseDBusError)(wrapError(err, "cannot close message bus proxy:", err))
}
}
// block until proxy wait returns
<-tx.dbusWait
return nil
}
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