mirror of
https://github.com/zlib-ng/minizip-ng
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87 lines
3.3 KiB
C
87 lines
3.3 KiB
C
/* crypt.h -- base code for crypt/uncrypt ZIPfile
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Version 1.01e, February 12th, 2005
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Copyright (C) 1998-2005 Gilles Vollant
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This code is a modified version of crypting code in Infozip distribution
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The encryption/decryption parts of this source code (as opposed to the
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non-echoing password parts) were originally written in Europe. The
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whole source package can be freely distributed, including from the USA.
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(Prior to January 2000, re-export from the US was a violation of US law.)
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This encryption code is a direct transcription of the algorithm from
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Roger Schlafly, described by Phil Katz in the file appnote.txt. This
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file (appnote.txt) is distributed with the PKZIP program (even in the
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version without encryption capabilities).
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If you don't need crypting in your application, just define symbols
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NOCRYPT and NOUNCRYPT.
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This code support the "Traditional PKWARE Encryption".
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The new AES encryption added on Zip format by Winzip (see the page
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http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
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Encryption is not supported.
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*/
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#ifndef _ZLIB_H
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# ifndef ZLIB_VERNUM
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/* No zlib */
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typedef uint32_t z_crc_t;
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# elif (ZLIB_VERNUM & 0xf != 0xf) && (ZLIB_VERNUM < 0x1270)
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/* Define z_crc_t in zlib 1.2.6 and less */
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typedef unsigned long z_crc_t;
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# elif (ZLIB_VERNUM & 0xf == 0xf) && (ZLIB_VERNUM < 0x12df)
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/* Define z_crc_t in zlib-ng 2.0.7 and less */
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typedef unsigned int z_crc_t;
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# endif
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#endif
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#define CRC32(c, b) ((*(pcrc_32_tab + (((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
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/***************************************************************************/
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/* Return the next byte in the pseudo-random sequence */
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static int decrypt_byte(unsigned long *pkeys, const z_crc_t *pcrc_32_tab) {
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unsigned temp; /* POTENTIAL BUG: temp*(temp^1) may overflow in an
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* unpredictable manner on 16-bit systems; not a problem
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* with any known compiler so far, though */
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(void)pcrc_32_tab;
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temp = ((unsigned)(*(pkeys + 2)) & 0xffff) | 2;
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return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
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}
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/***************************************************************************/
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/* Update the encryption keys with the next byte of plain text */
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static int update_keys(unsigned long *pkeys, const z_crc_t *pcrc_32_tab, int c) {
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(*(pkeys + 0)) = CRC32((*(pkeys + 0)), c);
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(*(pkeys + 1)) += (*(pkeys + 0)) & 0xff;
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(*(pkeys + 1)) = (*(pkeys + 1)) * 134775813L + 1;
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{
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register int keyshift = (int)((*(pkeys + 1)) >> 24);
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(*(pkeys + 2)) = CRC32((*(pkeys + 2)), keyshift);
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}
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return c;
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}
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/***************************************************************************/
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/* Initialize the encryption keys and the random header according to the password. */
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static void init_keys(const char *passwd, unsigned long *pkeys, const z_crc_t *pcrc_32_tab) {
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*(pkeys + 0) = 305419896L;
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*(pkeys + 1) = 591751049L;
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*(pkeys + 2) = 878082192L;
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while (*passwd != '\0') {
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update_keys(pkeys, pcrc_32_tab, (int)*passwd);
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passwd++;
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}
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}
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#define zdecode(pkeys, pcrc_32_tab, c) (update_keys(pkeys, pcrc_32_tab, c ^= decrypt_byte(pkeys, pcrc_32_tab)))
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#define zencode(pkeys, pcrc_32_tab, c, t) \
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(t = decrypt_byte(pkeys, pcrc_32_tab), update_keys(pkeys, pcrc_32_tab, c), (Byte)t ^ (c))
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