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54 lines
1.5 KiB
C
54 lines
1.5 KiB
C
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/* Copyright (c) 2001, Matej Pfajfar.
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* Copyright (c) 2001-2004, Roger Dingledine.
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* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
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* Copyright (c) 2007-2013, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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#include "crypto.h"
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#include "util.h"
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#include "compat.h"
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/** Implement RFC2440-style iterated-salted S2K conversion: convert the
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* <b>secret_len</b>-byte <b>secret</b> into a <b>key_out_len</b> byte
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* <b>key_out</b>. As in RFC2440, the first 8 bytes of s2k_specifier
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* are a salt; the 9th byte describes how much iteration to do.
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* Does not support <b>key_out_len</b> > DIGEST_LEN.
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*/
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void
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secret_to_key_rfc2440(char *key_out, size_t key_out_len, const char *secret,
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size_t secret_len, const char *s2k_specifier)
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{
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crypto_digest_t *d;
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uint8_t c;
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size_t count, tmplen;
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char *tmp;
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tor_assert(key_out_len < SIZE_T_CEILING);
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#define EXPBIAS 6
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c = s2k_specifier[8];
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count = ((uint32_t)16 + (c & 15)) << ((c >> 4) + EXPBIAS);
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#undef EXPBIAS
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tor_assert(key_out_len <= DIGEST_LEN);
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d = crypto_digest_new();
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tmplen = 8+secret_len;
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tmp = tor_malloc(tmplen);
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memcpy(tmp,s2k_specifier,8);
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memcpy(tmp+8,secret,secret_len);
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secret_len += 8;
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while (count) {
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if (count >= secret_len) {
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crypto_digest_add_bytes(d, tmp, secret_len);
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count -= secret_len;
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} else {
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crypto_digest_add_bytes(d, tmp, count);
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count = 0;
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}
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}
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crypto_digest_get_digest(d, key_out, key_out_len);
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memwipe(tmp, 0, tmplen);
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tor_free(tmp);
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crypto_digest_free(d);
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}
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