309 lines
11 KiB
C
309 lines
11 KiB
C
/* rsa.c
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**
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** Copyright 2012, 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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#include "mincrypt/sha256.h"
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// a[] -= mod
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static void subM(const RSAPublicKey* key,
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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,
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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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static void modpow(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 = 0;
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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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if (key->exponent == 65537) {
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aaa = aaR; // Re-use location.
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montMul(key, aR, a, key->rr); // aR = a * RR / R mod M
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for (i = 0; i < 16; i += 2) {
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montMul(key, aaR, aR, aR); // aaR = aR * aR / R mod M
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montMul(key, aR, aaR, aaR); // aR = aaR * aaR / R mod M
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}
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montMul(key, aaa, aR, a); // aaa = aR * a / R mod M
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} else if (key->exponent == 3) {
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aaa = aR; // Re-use location.
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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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}
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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 sha_padding[RSANUMBYTES] = {
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0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x21, 0x30,
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0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a,
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0x05, 0x00, 0x04, 0x14,
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// 20 bytes of hash go here.
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0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
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};
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*/
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// SHA-1 of PKCS1.5 signature sha_padding for 2048 bit, as above.
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// At the location of the bytes of the hash all 00 are hashed.
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static const uint8_t kExpectedPadShaRsa2048[SHA_DIGEST_SIZE] = {
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0xdc, 0xbd, 0xbe, 0x42, 0xd5, 0xf5, 0xa7, 0x2e,
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0x6e, 0xfc, 0xf5, 0x5d, 0xaf, 0x9d, 0xea, 0x68,
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0x7c, 0xfb, 0xf1, 0x67
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};
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/*
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static const uint8_t sha256_padding[RSANUMBYTES] = {
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0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0x00, 0x30, 0x31, 0x30,
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0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65,
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0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20,
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// 32 bytes of hash go here.
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0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
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0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
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};
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*/
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// SHA-256 of PKCS1.5 signature sha256_padding for 2048 bit, as above.
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// At the location of the bytes of the hash all 00 are hashed.
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static const uint8_t kExpectedPadSha256Rsa2048[SHA256_DIGEST_SIZE] = {
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0xab, 0x28, 0x8d, 0x8a, 0xd7, 0xd9, 0x59, 0x92,
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0xba, 0xcc, 0xf8, 0x67, 0x20, 0xe1, 0x15, 0x2e,
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0x39, 0x8d, 0x80, 0x36, 0xd6, 0x6f, 0xf0, 0xfd,
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0x90, 0xe8, 0x7d, 0x8b, 0xe1, 0x7c, 0x87, 0x59,
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};
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// Verify a 2048-bit RSA PKCS1.5 signature against an expected hash.
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// Both e=3 and e=65537 are supported. hash_len may be
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// SHA_DIGEST_SIZE (== 20) to indicate a SHA-1 hash, or
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// SHA256_DIGEST_SIZE (== 32) to indicate a SHA-256 hash. No other
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// values are supported.
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//
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// Returns 1 on successful verification, 0 on failure.
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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 *hash,
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const int hash_len) {
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uint8_t buf[RSANUMBYTES];
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int i;
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const uint8_t* padding_hash;
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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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if (hash_len != SHA_DIGEST_SIZE &&
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hash_len != SHA256_DIGEST_SIZE) {
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return 0; // Unsupported hash.
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}
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if (key->exponent != 3 && key->exponent != 65537) {
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return 0; // Unsupported exponent.
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}
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for (i = 0; i < len; ++i) { // Copy input to local workspace.
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buf[i] = signature[i];
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}
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modpow(key, buf); // In-place exponentiation.
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// Xor sha portion, so it all becomes 00 iff equal.
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for (i = len - hash_len; i < len; ++i) {
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buf[i] ^= *hash++;
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}
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// Hash resulting buf, in-place.
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switch (hash_len) {
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case SHA_DIGEST_SIZE:
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padding_hash = kExpectedPadShaRsa2048;
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SHA_hash(buf, len, buf);
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break;
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case SHA256_DIGEST_SIZE:
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padding_hash = kExpectedPadSha256Rsa2048;
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SHA256_hash(buf, len, buf);
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break;
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default:
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return 0;
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}
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// Compare against expected hash value.
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for (i = 0; i < hash_len; ++i) {
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if (buf[i] != padding_hash[i]) {
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return 0;
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}
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}
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return 1; // All checked out OK.
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}
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