Реализация шифрования ZipCrypto / Zip 2.0 в Java

Question

Я пытаюсь реализовать алгоритм шифрования zipcrypto / zip 2.0 для работы с зашифрованными файлами zip, как описано в

http://www.pkware.com/documents/casestudies/APPNOTE.TXT

Я верю, что следовал спецификациям, но просто не могу заставить его работать. Я уверен, что проблема связана с моей интерпретацией алгоритма CRC.

В документации говорится

CRC-32: (4 bytes)

The CRC-32 algorithm was generously contributed by
David Schwaderer and can be found in his excellent
book "C Programmers Guide to NetBIOS" published by
Howard W. Sams & Co. Inc.  The 'magic number' for
the CRC is 0xdebb20e3.  The proper CRC pre and post
conditioning is used, meaning that the CRC register
is pre-conditioned with all ones (a starting value
of 0xffffffff) and the value is post-conditioned by
taking the one's complement of the CRC residual.

Вот фрагмент, который я использую для crc32

public class PKZIPCRC32 {
    private static final int    CRC32_POLYNOMIAL    = 0xdebb20e3;
    private int                 crc                 = 0xffffffff;
    private int                 CRCTable[];

    public PKZIPCRC32() {
        buildCRCTable();
    }

    private void buildCRCTable() {
        int i, j;
        CRCTable = new int[256];
        for (i = 0; i <= 255; i++) {
            crc = i;
            for (j = 8; j > 0; j--)
                if ((crc & 1) == 1)
                    crc = (crc >>> 1) ^ CRC32_POLYNOMIAL;
                else
                    crc >>>= 1;
            CRCTable[i] = crc;
        }
    }

    private int crc32(byte buffer[], int start, int count, int lastcrc) {
        int temp1, temp2;
        int i = start;

        crc = lastcrc;

        while (count-- != 0) {
            temp1 = crc >>> 8;
            temp2 = CRCTable[(crc ^ buffer[i++]) & 0xFF];
            crc = temp1 ^ temp2;
        }

        return crc;
    }

    public int crc32(int crc, byte buffer) {
        return crc32(new byte[] { buffer }, 0, 1, crc);
    }
}

Ниже приведен мой полный код. Кто-нибудь может увидеть, что я делаю не так.

package org.apache.commons.compress.archivers.zip;

import java.io.IOException;
import java.io.InputStream;

public class ZipCryptoInputStream extends InputStream {
    public class PKZIPCRC32 {
        private static final int    CRC32_POLYNOMIAL    = 0xdebb20e3;
        private int                 crc                 = 0xffffffff;
        private int                 CRCTable[];

        public PKZIPCRC32() {
            buildCRCTable();
        }

        private void buildCRCTable() {
            int i, j;
            CRCTable = new int[256];
            for (i = 0; i <= 255; i++) {
                crc = i;
                for (j = 8; j > 0; j--)
                    if ((crc & 1) == 1)
                        crc = (crc >>> 1) ^ CRC32_POLYNOMIAL;
                    else
                        crc >>>= 1;
                CRCTable[i] = crc;
            }
        }

        private int crc32(byte buffer[], int start, int count, int lastcrc) {
            int temp1, temp2;
            int i = start;

            crc = lastcrc;

            while (count-- != 0) {
                temp1 = crc >>> 8;
                temp2 = CRCTable[(crc ^ buffer[i++]) & 0xFF];
                crc = temp1 ^ temp2;
            }

            return crc;
        }

        public int crc32(int crc, byte buffer) {
            return crc32(new byte[] { buffer }, 0, 1, crc);
        }
    }

    private static final long   ENCRYPTION_KEY_1    = 0x12345678;
    private static final long   ENCRYPTION_KEY_2    = 0x23456789;
    private static final long   ENCRYPTION_KEY_3    = 0x34567890;
    private InputStream         baseInputStream     = null;
    private final PKZIPCRC32    checksumEngine      = new PKZIPCRC32();
    private long[]              keys                = null;

    public ZipCryptoInputStream(ZipArchiveEntry zipEntry, InputStream inputStream, String passwd) throws Exception {
        baseInputStream = inputStream;
        // Decryption
        // ----------
        // PKZIP encrypts the compressed data stream. Encrypted files must
        // be decrypted before they can be extracted.
        //
        // Each encrypted file has an extra 12 bytes stored at the start of
        // the data area defining the encryption header for that file. The
        // encryption header is originally set to random values, and then
        // itself encrypted, using three, 32-bit keys. The key values are
        // initialized using the supplied encryption password. After each byte
        // is encrypted, the keys are then updated using pseudo-random number
        // generation techniques in combination with the same CRC-32 algorithm
        // used in PKZIP and described elsewhere in this document.
        //
        // The following is the basic steps required to decrypt a file:
        //
        // 1) Initialize the three 32-bit keys with the password.
        // 2) Read and decrypt the 12-byte encryption header, further
        // initializing the encryption keys.
        // 3) Read and decrypt the compressed data stream using the
        // encryption keys.

        // Step 1 - Initializing the encryption keys
        // -----------------------------------------
        //
        // Key(0) <- 305419896
        // Key(1) <- 591751049
        // Key(2) <- 878082192
        //
        // loop for i <- 0 to length(password)-1
        // update_keys(password(i))
        // end loop
        //
        // Where update_keys() is defined as:
        //
        // update_keys(char):
        // Key(0) <- crc32(key(0),char)
        // Key(1) <- Key(1) + (Key(0) & 000000ffH)
        // Key(1) <- Key(1) * 134775813 + 1
        // Key(2) <- crc32(key(2),key(1) >> 24)
        // end update_keys
        //
        // Where crc32(old_crc,char) is a routine that given a CRC value and a
        // character, returns an updated CRC value after applying the CRC-32
        // algorithm described elsewhere in this document.

        keys = new long[] { ENCRYPTION_KEY_1, ENCRYPTION_KEY_2, ENCRYPTION_KEY_3 };
        for (int i = 0; i < passwd.length(); ++i) {
            update_keys((byte) passwd.charAt(i));
        }

        // Step 2 - Decrypting the encryption header
        // -----------------------------------------
        //
        // The purpose of this step is to further initialize the encryption
        // keys, based on random data, to render a plaintext attack on the
        // data ineffective.
        //
        // Read the 12-byte encryption header into Buffer, in locations
        // Buffer(0) thru Buffer(11).
        //
        // loop for i <- 0 to 11
        // C <- buffer(i) ^ decrypt_byte()
        // update_keys(C)
        // buffer(i) <- C
        // end loop
        //
        // Where decrypt_byte() is defined as:
        //
        // unsigned char decrypt_byte()
        // local unsigned short temp
        // temp <- Key(2) | 2
        // decrypt_byte <- (temp * (temp ^ 1)) >> 8
        // end decrypt_byte
        //
        // After the header is decrypted, the last 1 or 2 bytes in Buffer
        // should be the high-order word/byte of the CRC for the file being
        // decrypted, stored in Intel low-byte/high-byte order. Versions of
        // PKZIP prior to 2.0 used a 2 byte CRC check; a 1 byte CRC check is
        // used on versions after 2.0. This can be used to test if the password
        // supplied is correct or not.
        byte[] encryptionHeader = new byte[12];
        baseInputStream.read(encryptionHeader);
        for (int i = 0; i < encryptionHeader.length; i++) {
            encryptionHeader[i] ^= decrypt_byte();
            update_keys(encryptionHeader[i]);
        }
    }

    protected byte decrypt_byte() {
        byte temp = (byte) (keys[2] | 2);
        return (byte) ((temp * (temp ^ 1)) >> 8);
    }

    @Override
    public int read() throws IOException {
        //
        // Step 3 - Decrypting the compressed data stream
        // ----------------------------------------------
        //
        // The compressed data stream can be decrypted as follows:
        //
        // loop until done
        // read a character into C
        // Temp <- C ^ decrypt_byte()
        // update_keys(temp)
        // output Temp
        // end loop
        int read = baseInputStream.read();
        read ^= decrypt_byte();
        update_keys((byte) read);
        return read;
    }

    private final void update_keys(byte ch) {
        keys[0] = checksumEngine.crc32((int) keys[0], ch);
        keys[1] = keys[1] + (byte) keys[0];
        keys[1] = keys[1] * 134775813 + 1;
        keys[2] = checksumEngine.crc32((int) keys[2], (byte) (keys[1] >> 24));
    }

}

Answer 1

Мое окончательное решение - благодаря ZZ Coder :

package org.apache.commons.compress.archivers.zip;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.ZipException;

import org.apache.commons.io.EndianUtils;

public class ZipCryptoInputStream extends InputStream {

    private static final long[] CRC32_TABLE_PRECALCULATED   = { 0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL, 0x076DC419L, 0x706AF48FL, 0xE963A535L, 0x9E6495A3L, 0x0EDB8832L, 0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L, 0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L, 0x90BF1D91L, 0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL, 0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L, 0x136C9856L, 0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL, 0x14015C4FL, 0x63066CD9L, 0xFA0F3D63L, 0x8D080DF5L, 0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L, 0xA2677172L, 0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL, 0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L, 0x32D86CE3L, 0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L, 0x26D930ACL, 0x51DE003AL, 0xC8D75180L, 0xBFD06116L, 0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L, 0xB8BDA50FL, 0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L, 0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL, 0x76DC4190L, 0x01DB7106L, 0x98D220BCL, 0xEFD5102AL, 0x71B18589L, 0x06B6B51FL, 0x9FBFE4A5L,
            0xE8B8D433L, 0x7807C9A2L, 0x0F00F934L, 0x9609A88EL, 0xE10E9818L, 0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L, 0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL, 0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L, 0x65B0D9C6L, 0x12B7E950L, 0x8BBEB8EAL, 0xFCB9887CL, 0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L, 0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L, 0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL, 0x4369E96AL, 0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L, 0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL, 0xDD0D7CC9L, 0x5005713CL, 0x270241AAL, 0xBE0B1010L, 0xC90C2086L, 0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL, 0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L, 0x59B33D17L, 0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL, 0xEDB88320L, 0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL, 0xEAD54739L, 0x9DD277AFL, 0x04DB2615L, 0x73DC1683L, 0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L, 0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L, 0xF00F9344L, 0x8708A3D2L,
            0x1E01F268L, 0x6906C2FEL, 0xF762575DL, 0x806567CBL, 0x196C3671L, 0x6E6B06E7L, 0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL, 0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L, 0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L, 0xD1BB67F1L, 0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL, 0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L, 0x41047A60L, 0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL, 0x4669BE79L, 0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L, 0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL, 0xC5BA3BBEL, 0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L, 0xC2D7FFA7L, 0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL, 0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL, 0x026D930AL, 0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L, 0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L, 0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L, 0x86D3D2D4L, 0xF1D4E242L, 0x68DDB3F8L, 0x1FDA836EL, 0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L, 0x18B74777L, 0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL, 0x8F659EFFL,
            0xF862AE69L, 0x616BFFD3L, 0x166CCF45L, 0xA00AE278L, 0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L, 0xA7672661L, 0xD06016F7L, 0x4969474DL, 0x3E6E77DBL, 0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L, 0x37D83BF0L, 0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L, 0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L, 0xBAD03605L, 0xCDD70693L, 0x54DE5729L, 0x23D967BFL, 0xB3667A2EL, 0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L, 0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL, 0x2D02EF8DL };

    /*
     * Uses irreducible polynomial: 1 + x + x^2 + x^4 + x^5 + x^7 + x^8 + x^10 + x^11 + x^12 + x^16 + x^22 + x^23 + x^26
     * 
     * 0000 0100 1100 0001 0001 1101 1011 0111 0 4 C 1 1 D B 7
     * 
     * The reverse of this polynomial is
     * 
     * 0 2 3 8 8 B D E
     */

    private static final int    CRC32_POLYNOMIAL            = 0xEDB88320;
    private static long[]       crc32Table                  = CRC32_TABLE_PRECALCULATED;

    // This is just here to show how we get the table if it wasn't pre-calculated
    static {
        if (false) {
            int i, j;
            crc32Table = new long[256];
            for (i = 0; i <= 255; i++) {
                int crc = i;
                for (j = 8; j > 0; j--) {
                    if ((crc & 1) == 1) {
                        crc = (crc >>> 1) ^ CRC32_POLYNOMIAL;
                    } else {
                        crc >>>= 1;
                    }
                }
                crc32Table[i] = Long.rotateLeft(crc, 32) >>> 32;
            }
        }
    }

    public static long crc32(long oldCrc, int character) {
        return crc32Table[(int) (oldCrc ^ character) & 0x000000ff] ^ (oldCrc >> 8);
    }

    // public static void main(String[] args) {
    // for (int i = 0; i < CRC_TABLE_PRECALCULATED.length; i++) {
    // System.out.println(Long.toHexString(CRC_TABLE_PRECALCULATED[i]) + "=" + Long.toHexString(crcTable[i]));
    // }
    // }

    private InputStream baseInputStream = null;

    private long[]      keys            = null;

    public ZipCryptoInputStream(ZipArchiveEntry zipEntry, InputStream inputStream, String passwd) throws Exception {
        // PKZIP encrypts the compressed data stream. Encrypted files must
        // be decrypted before they can be extracted.
        //       
        // Each encrypted file has an extra 12 bytes stored at the start of
        // the data area defining the encryption header for that file. The
        // encryption header is originally set to random values, and then
        // itself encrypted, using three, 32-bit keys. The key values are
        // initialized using the supplied encryption password. After each byte
        // is encrypted, the keys are then updated using pseudo-random number
        // generation techniques in combination with the same CRC-32 algorithm
        // used in PKZIP and described elsewhere in this document.
        //       
        // The following is the basic steps required to decrypt a file:
        //       
        // 1) Initialize the three 32-bit keys with the password.
        // 2) Read and decrypt the 12-byte encryption header, further
        // initializing the encryption keys.
        // 3) Read and decrypt the compressed data stream using the
        // encryption keys.

        baseInputStream = inputStream;

        // Step 1 - Initializing the encryption keys
        // -----------------------------------------
        //       
        // Key(0) <- 305419896
        // Key(1) <- 591751049
        // Key(2) <- 878082192

        keys = new long[] { 0x12345678l, 0x23456789l, 0x34567890l };

        // loop for i <- 0 to length(password)-1
        // update_keys(password(i))
        // end loop
        //
        // Where update_keys() is defined as:
        //           
        // update_keys(char):
        // Key(0) <- crc32(key(0),char)
        // Key(1) <- Key(1) + (Key(0) & 000000ffH)
        // Key(1) <- Key(1) * 134775813 + 1
        // Key(2) <- crc32(key(2),key(1) >> 24)
        // end update_keys
        //
        // Where crc32(old_crc,char) is a routine that given a CRC value and a
        // character, returns an updated CRC value after applying the CRC-32
        // algorithm described elsewhere in this document.
        for (int i = 0; i < passwd.length(); i++) {
            update_keys((byte) passwd.charAt(i));
        }

        // Step 2 - Decrypting the encryption header
        // -----------------------------------------
        //       
        // The purpose of this step is to further initialize the encryption
        // keys, based on random data, to render a plaintext attack on the
        // data ineffective.
        //       
        // Read the 12-byte encryption header into Buffer, in locations
        // Buffer(0) thru Buffer(11).
        //       
        // loop for i <- 0 to 11
        // C <- buffer(i) ^ decrypt_byte()
        // update_keys(C)
        // buffer(i) <- C
        // end loop
        //       
        // Where decrypt_byte() is defined as:
        //       
        // unsigned char decrypt_byte()
        // local unsigned short temp
        // temp <- Key(2) | 2
        // decrypt_byte <- (temp * (temp ^ 1)) >> 8
        // end decrypt_byte
        //       

        final byte[] encryptionHeader = new byte[12];
        for (int i = 0; i < 12; i++) {
            encryptionHeader[i] = (byte) read();
        }

        // After the header is decrypted, the last 1 or 2 bytes in Buffer
        // should be the high-order word/byte of the CRC for the file being
        // decrypted, stored in Intel low-byte/high-byte order. Versions of
        // PKZIP prior to 2.0 used a 2 byte CRC check; a 1 byte CRC check is
        // used on versions after 2.0. This can be used to test if the password
        // supplied is correct or not.
        byte[] passwordCheck = new byte[] { encryptionHeader[11], 0, 0, 0, 0, 0, 0, 0 };
        long suppliedPasswordCheck = EndianUtils.readSwappedLong(passwordCheck, 0);
        long actualPasswordCheck = zipEntry.getCrc() & 0xff000000;
        actualPasswordCheck = actualPasswordCheck >> 24;
        if (actualPasswordCheck != suppliedPasswordCheck) {
            throw new ZipException("Invalid password specified");
        }
    }

    private short decrypt_byte() {
        int t = (int) ((keys[2] & 0xFFFF) | 2);
        return (short) ((t * (t ^ 1)) >> 8);
    }

    @Override
    public int read() throws IOException {
        // Step 3 - Decrypting the compressed data stream
        // ----------------------------------------------
        //       
        // The compressed data stream can be decrypted as follows:
        //       
        // loop until done
        // read a character into C
        // Temp <- C ^ decrypt_byte()
        // update_keys(temp)
        // output Temp
        // end loop

        int c = baseInputStream.read();
        if (c != -1) {
            c = c ^ decrypt_byte();
            update_keys((byte) c);
            c = c & 0xffff;
        }
        return c;
    }

    private void update_keys(short byteValue) {
        keys[0] = crc32(keys[0], byteValue);
        keys[1] = keys[1] + (keys[0] & 0x000000ffl);
        keys[1] = (keys[1] * 134775813) + 1;
        keys[2] = crc32(keys[2], (byte) (keys[1] >> 24));
    }
}