hardcoresushi/libgocryptfs
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main: overwrite keys and let them run out of scope

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As soon as we don't need them anymore, overwrite
keys with zeros. Make sure they run out of scope
so we don't create a risk of inadvertedly using
all-zero keys for encryption.

https://github.com/rfjakob/gocryptfs/issues/211
This commit is contained in:
Jakob Unterwurzacher 2018-02-18 12:42:22 +01:00
parent bd78b44389
commit 5b5c7a0a5d
2 changed files with 49 additions and 39 deletions
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19
init_dir.go
View File

@ -36,13 +36,18 @@ func initDir(args *argContainer) {
if args.extpass == "" {
tlog.Info.Printf("Choose a password for protecting your files.")
}
password := readpassword.Twice(args.extpass)
readpassword.CheckTrailingGarbage()
creator := tlog.ProgramName + " " + GitVersion
err = configfile.CreateConfFile(args.config, password, args.plaintextnames, args.scryptn, creator, args.aessiv, args.devrandom)
if err != nil {
tlog.Fatal.Println(err)
os.Exit(exitcodes.WriteConf)
{
creator := tlog.ProgramName + " " + GitVersion
password := readpassword.Twice(args.extpass)
readpassword.CheckTrailingGarbage()
err = configfile.CreateConfFile(args.config, password, args.plaintextnames, args.scryptn, creator, args.aessiv, args.devrandom)
if err != nil {
tlog.Fatal.Println(err)
os.Exit(exitcodes.WriteConf)
}
// Note: cannot overwrite password because in Go, strings are
// read-only byte slices.
// password runs out of scope here
}
// Forward mode with filename encryption enabled needs a gocryptfs.diriv
// in the root dir

69
mount.go
View File

@ -93,37 +93,47 @@ func doMount(args *argContainer) int {
}
}()
}
// Get master key (may prompt for the password)
var masterkey []byte
var confFile *configfile.ConfFile
if args.masterkey != "" {
// "-masterkey"
masterkey = parseMasterKey(args.masterkey)
} else if args.zerokey {
// "-zerokey"
tlog.Info.Printf("Using all-zero dummy master key.")
tlog.Info.Printf(tlog.ColorYellow +
"ZEROKEY MODE PROVIDES NO SECURITY AT ALL AND SHOULD ONLY BE USED FOR TESTING." +
tlog.ColorReset)
masterkey = make([]byte, cryptocore.KeyLen)
} else {
// Load master key from config file
// Prompts the user for the password
masterkey, confFile, err = loadConfig(args)
if err != nil {
if args._ctlsockFd != nil {
// Close the socket file (which also deletes it)
args._ctlsockFd.Close()
var srv *fuse.Server
var wipeKeys func()
{
// Get master key (may prompt for the password)
var masterkey []byte
if args.masterkey != "" {
// "-masterkey"
masterkey = parseMasterKey(args.masterkey)
} else if args.zerokey {
// "-zerokey"
tlog.Info.Printf("Using all-zero dummy master key.")
tlog.Info.Printf(tlog.ColorYellow +
"ZEROKEY MODE PROVIDES NO SECURITY AT ALL AND SHOULD ONLY BE USED FOR TESTING." +
tlog.ColorReset)
masterkey = make([]byte, cryptocore.KeyLen)
} else {
// Load master key from config file
// Prompts the user for the password
masterkey, confFile, err = loadConfig(args)
if err != nil {
if args._ctlsockFd != nil {
// Close the socket file (which also deletes it)
args._ctlsockFd.Close()
}
exitcodes.Exit(err)
}
exitcodes.Exit(err)
readpassword.CheckTrailingGarbage()
printMasterKey(masterkey)
}
readpassword.CheckTrailingGarbage()
printMasterKey(masterkey)
// We cannot use JSON for pretty-printing as the fields are unexported
tlog.Debug.Printf("cli args: %#v", args)
// Initialize FUSE server
srv, wipeKeys = initFuseFrontend(masterkey, args, confFile)
// fusefrontend / fusefrontend_reverse have initialized their crypto,
// we can purge the master key from memory.
for i := range masterkey {
masterkey[i] = 0
}
// masterkey runs out of scope here
}
// We cannot use JSON for pretty-printing as the fields are unexported
tlog.Debug.Printf("cli args: %#v", args)
// Initialize FUSE server
srv, wipeKeys := initFuseFrontend(masterkey, args, confFile)
tlog.Info.Println(tlog.ColorGreen + "Filesystem mounted and ready." + tlog.ColorReset)
// We have been forked into the background, as evidenced by the set
// "notifypid".
@ -267,11 +277,6 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
} else {
fs = fusefrontend.NewFS(frontendArgs, cEnc, nameTransform)
}
// fusefrontend / fusefrontend_reverse have initialized their crypto with
// derived keys (HKDF), we can purge the master key from memory.
for i := range masterkey {
masterkey[i] = 0
}
// We have opened the socket early so that we cannot fail here after
// asking the user for the password
if args._ctlsockFd != nil {