198 lines
6.7 KiB
C
198 lines
6.7 KiB
C
/* rsa.c
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**
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** Copyright 2008, The Android Open Source Project
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**
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** Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions are met:
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** * Redistributions of source code must retain the above copyright
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** notice, this list of conditions and the following disclaimer.
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** * Redistributions in binary form must reproduce the above copyright
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** notice, this list of conditions and the following disclaimer in the
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** documentation and/or other materials provided with the distribution.
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** * Neither the name of Google Inc. nor the names of its contributors may
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** be used to endorse or promote products derived from this software
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** without specific prior written permission.
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**
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** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR
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** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "mincrypt/rsa.h"
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#include "mincrypt/sha.h"
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/* a[] -= mod */
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static void subM(const RSAPublicKey *key, uint32_t *a) {
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int64_t A = 0;
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int i;
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for (i = 0; i < key->len; ++i) {
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A += (uint64_t)a[i] - key->n[i];
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a[i] = (uint32_t)A;
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A >>= 32;
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}
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}
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/* return a[] >= mod */
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static int geM(const RSAPublicKey *key, const uint32_t *a) {
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int i;
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for (i = key->len; i;) {
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--i;
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if (a[i] < key->n[i]) return 0;
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if (a[i] > key->n[i]) return 1;
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}
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return 1; /* equal */
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}
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/* montgomery c[] += a * b[] / R % mod */
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static void montMulAdd(const RSAPublicKey *key,
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uint32_t* c,
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const uint32_t a,
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const uint32_t* b) {
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uint64_t A = (uint64_t)a * b[0] + c[0];
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uint32_t d0 = (uint32_t)A * key->n0inv;
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uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A;
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int i;
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for (i = 1; i < key->len; ++i) {
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A = (A >> 32) + (uint64_t)a * b[i] + c[i];
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B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A;
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c[i - 1] = (uint32_t)B;
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}
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A = (A >> 32) + (B >> 32);
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c[i - 1] = (uint32_t)A;
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if (A >> 32) {
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subM(key, c);
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}
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}
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/* montgomery c[] = a[] * b[] / R % mod */
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static void montMul(const RSAPublicKey *key,
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uint32_t* c,
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const uint32_t* a,
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const uint32_t* b) {
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int i;
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for (i = 0; i < key->len; ++i) {
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c[i] = 0;
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}
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for (i = 0; i < key->len; ++i) {
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montMulAdd(key, c, a[i], b);
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}
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}
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/* In-place public exponentiation.
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** Input and output big-endian byte array in inout.
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*/
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static void modpow3(const RSAPublicKey *key,
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uint8_t* inout) {
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uint32_t a[RSANUMWORDS];
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uint32_t aR[RSANUMWORDS];
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uint32_t aaR[RSANUMWORDS];
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uint32_t *aaa = aR; /* Re-use location. */
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int i;
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/* Convert from big endian byte array to little endian word array. */
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for (i = 0; i < key->len; ++i) {
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uint32_t tmp =
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(inout[((key->len - 1 - i) * 4) + 0] << 24) |
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(inout[((key->len - 1 - i) * 4) + 1] << 16) |
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(inout[((key->len - 1 - i) * 4) + 2] << 8) |
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(inout[((key->len - 1 - i) * 4) + 3] << 0);
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a[i] = tmp;
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}
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montMul(key, aR, a, key->rr); /* aR = a * RR / R mod M */
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montMul(key, aaR, aR, aR); /* aaR = aR * aR / R mod M */
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montMul(key, aaa, aaR, a); /* aaa = aaR * a / R mod M */
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/* Make sure aaa < mod; aaa is at most 1x mod too large. */
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if (geM(key, aaa)) {
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subM(key, aaa);
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}
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/* Convert to bigendian byte array */
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for (i = key->len - 1; i >= 0; --i) {
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uint32_t tmp = aaa[i];
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*inout++ = tmp >> 24;
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*inout++ = tmp >> 16;
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*inout++ = tmp >> 8;
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*inout++ = tmp >> 0;
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}
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}
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/* Expected PKCS1.5 signature padding bytes, for a keytool RSA signature.
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** Has the 0-length optional parameter encoded in the ASN1 (as opposed to the
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** other flavor which omits the optional parameter entirely). This code does not
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** accept signatures without the optional parameter.
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*/
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static const uint8_t padding[RSANUMBYTES - SHA_DIGEST_SIZE] = {
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0x00,0x01,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
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0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00,
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0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x0e,0x03,0x02,0x1a,0x05,0x00,
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0x04,0x14
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};
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/* Verify a 2048 bit RSA PKCS1.5 signature against an expected SHA-1 hash.
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** Returns 0 on failure, 1 on success.
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*/
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int RSA_verify(const RSAPublicKey *key,
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const uint8_t *signature,
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const int len,
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const uint8_t *sha) {
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uint8_t buf[RSANUMBYTES];
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int i;
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if (key->len != RSANUMWORDS) {
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return 0; /* Wrong key passed in. */
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}
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if (len != sizeof(buf)) {
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return 0; /* Wrong input length. */
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}
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for (i = 0; i < len; ++i) {
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buf[i] = signature[i];
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}
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modpow3(key, buf);
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/* Check pkcs1.5 padding bytes. */
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for (i = 0; i < (int) sizeof(padding); ++i) {
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if (buf[i] != padding[i]) {
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return 0;
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}
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}
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/* Check sha digest matches. */
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for (; i < len; ++i) {
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if (buf[i] != *sha++) {
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return 0;
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}
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}
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return 1;
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}
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