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package main
import (
"encoding/hex"
"flag"
"fmt"
"io"
"os"
"github.com/rfjakob/gocryptfs/internal/configfile"
"github.com/rfjakob/gocryptfs/internal/contentenc"
"github.com/rfjakob/gocryptfs/internal/cryptocore"
"github.com/rfjakob/gocryptfs/internal/exitcodes"
"github.com/rfjakob/gocryptfs/internal/readpassword"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
ivLen = contentenc.DefaultIVBits / 8
authTagLen = cryptocore.AuthTagLen
blockSize = contentenc.DefaultBS + ivLen + cryptocore.AuthTagLen
myName = "gocryptfs-xray"
)
func errExit(err error) {
fmt.Println(err)
os.Exit(1)
}
func prettyPrintHeader(h *contentenc.FileHeader, aessiv bool) {
id := hex.EncodeToString(h.ID)
msg := "Header: Version: %d, Id: %s"
if aessiv {
msg += ", assuming AES-SIV mode"
} else {
msg += ", assuming AES-GCM mode"
}
fmt.Printf(msg+"\n", h.Version, id)
}
func main() {
dumpmasterkey := flag.Bool("dumpmasterkey", false, "Decrypt and dump the master key")
aessiv := flag.Bool("aessiv", false, "Assume AES-SIV mode instead of AES-GCM")
flag.Parse()
if flag.NArg() != 1 {
fmt.Fprintf(os.Stderr, "Usage: %s [OPTIONS] FILE\n"+
"\n"+
"Options:\n", myName)
flag.PrintDefaults()
fmt.Fprintf(os.Stderr, "\n"+
"Examples:\n"+
" gocryptfs-xray myfs/mCXnISiv7nEmyc0glGuhTQ\n"+
" gocryptfs-xray -dumpmasterkey myfs/gocryptfs.conf\n")
os.Exit(1)
}
fn := flag.Arg(0)
fd, err := os.Open(fn)
if err != nil {
errExit(err)
}
defer fd.Close()
if *dumpmasterkey {
dumpMasterKey(fn)
} else {
inspectCiphertext(fd, *aessiv)
}
}
func dumpMasterKey(fn string) {
tlog.Info.Enabled = false
pw := readpassword.Once(nil, "", "")
masterkey, _, err := configfile.LoadAndDecrypt(fn, pw)
if err != nil {
fmt.Fprintln(os.Stderr, err)
exitcodes.Exit(err)
}
fmt.Println(hex.EncodeToString(masterkey))
for i := range pw {
pw[i] = 0
}
}
func inspectCiphertext(fd *os.File, aessiv bool) {
headerBytes := make([]byte, contentenc.HeaderLen)
n, err := fd.ReadAt(headerBytes, 0)
if err == io.EOF && n == 0 {
fmt.Println("empty file")
os.Exit(0)
} else if err == io.EOF {
fmt.Printf("incomplete file header: read %d bytes, want %d\n", n, contentenc.HeaderLen)
os.Exit(1)
} else if err != nil {
errExit(err)
}
header, err := contentenc.ParseHeader(headerBytes)
if err != nil {
errExit(err)
}
prettyPrintHeader(header, aessiv)
var i int64
buf := make([]byte, blockSize)
for i = 0; ; i++ {
off := contentenc.HeaderLen + i*blockSize
n, err := fd.ReadAt(buf, off)
if err != nil && err != io.EOF {
errExit(err)
}
if n == 0 && err == io.EOF {
break
}
// A block contains at least the IV, the Auth Tag and 1 data byte
if n < ivLen+authTagLen+1 {
errExit(fmt.Errorf("corrupt block: truncated data, len=%d", n))
}
data := buf[:n]
// Parse block data
iv := data[:ivLen]
tag := data[len(data)-authTagLen:]
if aessiv {
tag = data[ivLen : ivLen+authTagLen]
}
fmt.Printf("Block %2d: IV: %s, Tag: %s, Offset: %5d Len: %d\n",
i, hex.EncodeToString(iv), hex.EncodeToString(tag), off, len(data))
}
}
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