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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Pdfpasswd searches for the password for an encrypted PDF
// by trying all strings over a given alphabet up to a given length.
package main // import "rsc.io/pdf/pdfpasswd"
import (
"flag"
"fmt"
"log"
"os"
"rsc.io/pdf"
)
var (
alphabet = flag.String("a", "0123456789", "alphabet")
maxLength = flag.Int("m", 4, "max length")
)
func usage() {
fmt.Fprintf(os.Stderr, "usage: pdfpasswd [-a alphabet] [-m maxlength] file\n")
os.Exit(2)
}
func main() {
log.SetFlags(0)
log.SetPrefix("pdfpasswd: ")
flag.Usage = usage
flag.Parse()
if flag.NArg() != 1 {
usage()
}
f, err := os.Open(flag.Arg(0))
if err != nil {
log.Fatal(err)
}
last := ""
alpha := *alphabet
ctr := make([]int, *maxLength)
pw := func() string {
inc(ctr, len(alpha)+1)
for !valid(ctr) {
inc(ctr, len(alpha)+1)
}
if done(ctr) {
return ""
}
buf := make([]byte, len(ctr))
var i int
for i = 0; i < len(buf); i++ {
if ctr[i] == 0 {
break
}
buf[i] = alpha[ctr[i]-1]
}
last = string(buf[:i])
println(last)
return last
}
st, err := f.Stat()
if err != nil {
log.Fatal(err)
}
_, err = pdf.NewReaderEncrypted(f, st.Size(), pw)
if err != nil {
if err == pdf.ErrInvalidPassword {
log.Fatal("password not found")
}
log.Fatal("reading pdf: %v", err)
}
fmt.Printf("password: %q\n", last)
}
func inc(ctr []int, n int) {
for i := 0; i < len(ctr); i++ {
ctr[i]++
if ctr[i] < n {
break
}
ctr[i] = 0
}
}
func done(ctr []int) bool {
for _, x := range ctr {
if x != 0 {
return false
}
}
return true
}
func valid(ctr []int) bool {
i := len(ctr)
for i > 0 && ctr[i-1] == 0 {
i--
}
for i--; i >= 0; i-- {
if ctr[i] == 0 {
return false
}
}
return true
}
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