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