/* * Copyright (c) 2013-2014 Kurt Jung (Gmail: kurt.w.jung) * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ // PDF protection is adapted from the work of Klemen VODOPIVEC for the fpdf // product. package gofpdf import ( "crypto/md5" "crypto/rc4" "encoding/binary" "math/rand" ) // Advisory bitflag constants that control document activities const ( CnProtectPrint = 4 CnProtectModify = 8 CnProtectCopy = 16 CnProtectAnnotForms = 32 ) type protectType struct { encrypted bool uValue []byte oValue []byte pValue int padding []byte encryptionKey []byte objNum int rc4cipher *rc4.Cipher rc4n uint32 // Object number associated with rc4 cipher } func (p *protectType) rc4(n uint32, buf *[]byte) { if p.rc4cipher == nil || p.rc4n != n { p.rc4cipher, _ = rc4.NewCipher(p.objectKey(n)) p.rc4n = n } p.rc4cipher.XORKeyStream(*buf, *buf) } func (p *protectType) objectKey(n uint32) []byte { var nbuf, b []byte nbuf = make([]byte, 8, 8) binary.LittleEndian.PutUint32(nbuf, n) b = append(b, p.encryptionKey...) b = append(b, nbuf[0], nbuf[1], nbuf[2], 0, 0) s := md5.Sum(b) return s[0:10] } func oValueGen(userPass, ownerPass []byte) (v []byte) { var c *rc4.Cipher tmp := md5.Sum(ownerPass) c, _ = rc4.NewCipher(tmp[0:5]) size := len(userPass) v = make([]byte, size, size) c.XORKeyStream(v, userPass) return } func (p *protectType) uValueGen() (v []byte) { var c *rc4.Cipher c, _ = rc4.NewCipher(p.encryptionKey) size := len(p.padding) v = make([]byte, size, size) c.XORKeyStream(v, p.padding) return } func (p *protectType) setProtection(privFlag byte, userPassStr, ownerPassStr string) { privFlag = 192 | (privFlag & (CnProtectCopy | CnProtectModify | CnProtectPrint | CnProtectAnnotForms)) p.padding = []byte{ 0x28, 0xBF, 0x4E, 0x5E, 0x4E, 0x75, 0x8A, 0x41, 0x64, 0x00, 0x4E, 0x56, 0xFF, 0xFA, 0x01, 0x08, 0x2E, 0x2E, 0x00, 0xB6, 0xD0, 0x68, 0x3E, 0x80, 0x2F, 0x0C, 0xA9, 0xFE, 0x64, 0x53, 0x69, 0x7A, } userPass := []byte(userPassStr) var ownerPass []byte if ownerPassStr == "" { ownerPass = make([]byte, 8, 8) binary.LittleEndian.PutUint64(ownerPass, uint64(rand.Int63())) } else { ownerPass = []byte(ownerPassStr) } userPass = append(userPass, p.padding...)[0:32] ownerPass = append(ownerPass, p.padding...)[0:32] p.encrypted = true p.oValue = oValueGen(userPass, ownerPass) var buf []byte buf = append(buf, userPass...) buf = append(buf, p.oValue...) buf = append(buf, privFlag, 0xff, 0xff, 0xff) sum := md5.Sum(buf) p.encryptionKey = sum[0:5] p.uValue = p.uValueGen() p.pValue = -(int(privFlag^255) + 1) }