| /* crypt.h -- base code for crypt/uncrypt ZIPfile |
| |
| |
| Version 1.01e, February 12th, 2005 |
| |
| Copyright (C) 1998-2005 Gilles Vollant |
| |
| This code is a modified version of crypting code in Infozip distribution |
| |
| The encryption/decryption parts of this source code (as opposed to the |
| non-echoing password parts) were originally written in Europe. The |
| whole source package can be freely distributed, including from the USA. |
| (Prior to January 2000, re-export from the US was a violation of US law.) |
| |
| This encryption code is a direct transcription of the algorithm from |
| Roger Schlafly, described by Phil Katz in the file appnote.txt. This |
| file (appnote.txt) is distributed with the PKZIP program (even in the |
| version without encryption capabilities). |
| |
| If you don't need crypting in your application, just define symbols |
| NOCRYPT and NOUNCRYPT. |
| |
| This code support the "Traditional PKWARE Encryption". |
| |
| The new AES encryption added on Zip format by Winzip (see the page |
| http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong |
| Encryption is not supported. |
| */ |
| |
| #define CRC32(c, b) ((*(pcrc_32_tab+(((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8)) |
| |
| /*********************************************************************** |
| * Return the next byte in the pseudo-random sequence |
| */ |
| static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab) |
| { |
| (void) pcrc_32_tab; /* avoid "unused parameter" warning */ |
| unsigned temp; /* POTENTIAL BUG: temp*(temp^1) may overflow in an |
| * unpredictable manner on 16-bit systems; not a problem |
| * with any known compiler so far, though */ |
| |
| temp = ((unsigned)(*(pkeys+2)) & 0xffff) | 2; |
| return (int)(((temp * (temp ^ 1)) >> 8) & 0xff); |
| } |
| |
| /*********************************************************************** |
| * Update the encryption keys with the next byte of plain text |
| */ |
| static int update_keys(unsigned long* pkeys,const unsigned long* pcrc_32_tab,int c) |
| { |
| (*(pkeys+0)) = CRC32((*(pkeys+0)), c); |
| (*(pkeys+1)) += (*(pkeys+0)) & 0xff; |
| (*(pkeys+1)) = (*(pkeys+1)) * 134775813L + 1; |
| { |
| register int keyshift = (int)((*(pkeys+1)) >> 24); |
| (*(pkeys+2)) = CRC32((*(pkeys+2)), keyshift); |
| } |
| return c; |
| } |
| |
| |
| /*********************************************************************** |
| * Initialize the encryption keys and the random header according to |
| * the given password. |
| */ |
| static void init_keys(const char* passwd,unsigned long* pkeys,const unsigned long* pcrc_32_tab) |
| { |
| *(pkeys+0) = 305419896L; |
| *(pkeys+1) = 591751049L; |
| *(pkeys+2) = 878082192L; |
| while (*passwd != '\0') { |
| update_keys(pkeys,pcrc_32_tab,(int)*passwd); |
| passwd++; |
| } |
| } |
| |
| #define zdecode(pkeys,pcrc_32_tab,c) \ |
| (update_keys(pkeys,pcrc_32_tab,c ^= decrypt_byte(pkeys,pcrc_32_tab))) |
| |
| #define zencode(pkeys,pcrc_32_tab,c,t) \ |
| (t=decrypt_byte(pkeys,pcrc_32_tab), update_keys(pkeys,pcrc_32_tab,c), t^(c)) |
| |
| #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED |
| |
| #define RAND_HEAD_LEN 12 |
| /* "last resort" source for second part of crypt seed pattern */ |
| # ifndef ZCR_SEED2 |
| # define ZCR_SEED2 3141592654UL /* use PI as default pattern */ |
| # endif |
| |
| static int crypthead(passwd, buf, bufSize, pkeys, pcrc_32_tab, crcForCrypting) |
| const char *passwd; /* password string */ |
| unsigned char *buf; /* where to write header */ |
| int bufSize; |
| unsigned long* pkeys; |
| const unsigned long* pcrc_32_tab; |
| unsigned long crcForCrypting; |
| { |
| int n; /* index in random header */ |
| int t; /* temporary */ |
| int c; /* random byte */ |
| unsigned char header[RAND_HEAD_LEN-2]; /* random header */ |
| static unsigned calls = 0; /* ensure different random header each time */ |
| |
| if (bufSize<RAND_HEAD_LEN) |
| return 0; |
| |
| /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the |
| * output of rand() to get less predictability, since rand() is |
| * often poorly implemented. |
| */ |
| if (++calls == 1) |
| { |
| srand((unsigned)(time(NULL) ^ ZCR_SEED2)); |
| } |
| init_keys(passwd, pkeys, pcrc_32_tab); |
| for (n = 0; n < RAND_HEAD_LEN-2; n++) |
| { |
| c = (rand() >> 7) & 0xff; |
| header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t); |
| } |
| /* Encrypt random header (last two bytes is high word of crc) */ |
| init_keys(passwd, pkeys, pcrc_32_tab); |
| for (n = 0; n < RAND_HEAD_LEN-2; n++) |
| { |
| buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t); |
| } |
| buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t); |
| buf[n++] = zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t); |
| return n; |
| } |
| |
| #endif |