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121 lines
4.1 KiB
C
121 lines
4.1 KiB
C
/* zb32.c - z-base-32 functions
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* Copyright (C) 2014 Werner Koch
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*
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* This file is part of GnuPG.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of either
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*
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* - the GNU Lesser General Public License as published by the Free
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* Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* or
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*
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* - the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* or both in parallel, as here.
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*
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* This file is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <assert.h>
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#include "util.h"
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#include "zb32.h"
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/* Zooko's base32 variant. See RFC-6189 and
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http://philzimmermann.com/docs/human-oriented-base-32-encoding.txt
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Caller must xfree the returned string. Returns NULL and sets ERRNO
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on error. To avoid integer overflow DATALEN is limited to 2^16
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bytes. Note, that DATABITS is measured in bits!. */
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char *
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zb32_encode (const void *data, unsigned int databits)
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{
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static char const zb32asc[32] = {'y','b','n','d','r','f','g','8',
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'e','j','k','m','c','p','q','x',
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'o','t','1','u','w','i','s','z',
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'a','3','4','5','h','7','6','9' };
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const unsigned char *s;
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char *output, *d;
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size_t datalen;
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datalen = (databits + 7) / 8;
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if (datalen > (1 << 16))
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{
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errno = EINVAL;
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return NULL;
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}
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d = output = xtrymalloc (8 * (datalen / 5)
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+ 2 * (datalen % 5)
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- ((datalen%5)>2)
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+ 1);
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if (!output)
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return NULL;
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/* I use straightforward code. The compiler should be able to do a
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better job on optimization than me and it is easier to read. */
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for (s = data; datalen >= 5; s += 5, datalen -= 5)
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{
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*d++ = zb32asc[((s[0] ) >> 3) ];
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*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
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*d++ = zb32asc[((s[1] & 63) >> 1) ];
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*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
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*d++ = zb32asc[((s[2] & 15) << 1) | (s[3] >> 7) ];
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*d++ = zb32asc[((s[3] & 127) >> 2) ];
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*d++ = zb32asc[((s[3] & 3) << 3) | (s[4] >> 5) ];
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*d++ = zb32asc[((s[4] & 31) ) ];
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}
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switch (datalen)
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{
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case 4:
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*d++ = zb32asc[((s[0] ) >> 3) ];
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*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
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*d++ = zb32asc[((s[1] & 63) >> 1) ];
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*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
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*d++ = zb32asc[((s[2] & 15) << 1) | (s[3] >> 7) ];
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*d++ = zb32asc[((s[3] & 127) >> 2) ];
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*d++ = zb32asc[((s[3] & 3) << 3) ];
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break;
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case 3:
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*d++ = zb32asc[((s[0] ) >> 3) ];
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*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
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*d++ = zb32asc[((s[1] & 63) >> 1) ];
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*d++ = zb32asc[((s[1] & 1) << 4) | (s[2] >> 4) ];
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*d++ = zb32asc[((s[2] & 15) << 1) ];
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break;
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case 2:
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*d++ = zb32asc[((s[0] ) >> 3) ];
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*d++ = zb32asc[((s[0] & 7) << 2) | (s[1] >> 6) ];
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*d++ = zb32asc[((s[1] & 63) >> 1) ];
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*d++ = zb32asc[((s[1] & 1) << 4) ];
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break;
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case 1:
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*d++ = zb32asc[((s[0] ) >> 3) ];
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*d++ = zb32asc[((s[0] & 7) << 2) ];
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break;
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default:
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break;
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}
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*d = 0;
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/* Need to strip some bytes if not a multiple of 40. */
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output[(databits + 5 - 1) / 5] = 0;
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return output;
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}
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