summaryrefslogtreecommitdiff
path: root/libmincrypt/rsa_e_f4.c
diff options
context:
space:
mode:
Diffstat (limited to 'libmincrypt/rsa_e_f4.c')
-rw-r--r--libmincrypt/rsa_e_f4.c196
1 files changed, 196 insertions, 0 deletions
diff --git a/libmincrypt/rsa_e_f4.c b/libmincrypt/rsa_e_f4.c
new file mode 100644
index 000000000..6701bcc20
--- /dev/null
+++ b/libmincrypt/rsa_e_f4.c
@@ -0,0 +1,196 @@
+/* rsa_e_f4.c
+**
+** Copyright 2012, The Android Open Source Project
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are met:
+** * Redistributions of source code must retain the above copyright
+** notice, this list of conditions and the following disclaimer.
+** * Redistributions in binary form must reproduce the above copyright
+** notice, this list of conditions and the following disclaimer in the
+** documentation and/or other materials provided with the distribution.
+** * Neither the name of Google Inc. nor the names of its contributors may
+** be used to endorse or promote products derived from this software
+** without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR
+** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include "mincrypt/rsa.h"
+#include "mincrypt/sha.h"
+
+// a[] -= mod
+static void subM(const RSAPublicKey* key,
+ uint32_t* a) {
+ int64_t A = 0;
+ int i;
+ for (i = 0; i < key->len; ++i) {
+ A += (uint64_t)a[i] - key->n[i];
+ a[i] = (uint32_t)A;
+ A >>= 32;
+ }
+}
+
+// return a[] >= mod
+static int geM(const RSAPublicKey* key,
+ const uint32_t* a) {
+ int i;
+ for (i = key->len; i;) {
+ --i;
+ if (a[i] < key->n[i]) return 0;
+ if (a[i] > key->n[i]) return 1;
+ }
+ return 1; // equal
+}
+
+// montgomery c[] += a * b[] / R % mod
+static void montMulAdd(const RSAPublicKey* key,
+ uint32_t* c,
+ const uint32_t a,
+ const uint32_t* b) {
+ uint64_t A = (uint64_t)a * b[0] + c[0];
+ uint32_t d0 = (uint32_t)A * key->n0inv;
+ uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A;
+ int i;
+
+ for (i = 1; i < key->len; ++i) {
+ A = (A >> 32) + (uint64_t)a * b[i] + c[i];
+ B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A;
+ c[i - 1] = (uint32_t)B;
+ }
+
+ A = (A >> 32) + (B >> 32);
+
+ c[i - 1] = (uint32_t)A;
+
+ if (A >> 32) {
+ subM(key, c);
+ }
+}
+
+// montgomery c[] = a[] * b[] / R % mod
+static void montMul(const RSAPublicKey* key,
+ uint32_t* c,
+ const uint32_t* a,
+ const uint32_t* b) {
+ int i;
+ for (i = 0; i < key->len; ++i) {
+ c[i] = 0;
+ }
+ for (i = 0; i < key->len; ++i) {
+ montMulAdd(key, c, a[i], b);
+ }
+}
+
+// In-place public exponentiation.
+// Input and output big-endian byte array in inout.
+static void modpowF4(const RSAPublicKey* key,
+ uint8_t* inout) {
+ uint32_t a[RSANUMWORDS];
+ uint32_t aR[RSANUMWORDS];
+ uint32_t aaR[RSANUMWORDS];
+ uint32_t* aaa = aaR; // Re-use location.
+ int i;
+
+ // Convert from big endian byte array to little endian word array.
+ for (i = 0; i < key->len; ++i) {
+ uint32_t tmp =
+ (inout[((key->len - 1 - i) * 4) + 0] << 24) |
+ (inout[((key->len - 1 - i) * 4) + 1] << 16) |
+ (inout[((key->len - 1 - i) * 4) + 2] << 8) |
+ (inout[((key->len - 1 - i) * 4) + 3] << 0);
+ a[i] = tmp;
+ }
+
+ montMul(key, aR, a, key->rr); // aR = a * RR / R mod M
+ for (i = 0; i < 16; i += 2) {
+ montMul(key, aaR, aR, aR); // aaR = aR * aR / R mod M
+ montMul(key, aR, aaR, aaR); // aR = aaR * aaR / R mod M
+ }
+ montMul(key, aaa, aR, a); // aaa = aR * a / R mod M
+
+ // Make sure aaa < mod; aaa is at most 1x mod too large.
+ if (geM(key, aaa)) {
+ subM(key, aaa);
+ }
+
+ // Convert to bigendian byte array
+ for (i = key->len - 1; i >= 0; --i) {
+ uint32_t tmp = aaa[i];
+ *inout++ = tmp >> 24;
+ *inout++ = tmp >> 16;
+ *inout++ = tmp >> 8;
+ *inout++ = tmp >> 0;
+ }
+}
+
+// Expected PKCS1.5 signature padding bytes, for a keytool RSA signature.
+// Has the 0-length optional parameter encoded in the ASN1 (as opposed to the
+// other flavor which omits the optional parameter entirely). This code does not
+// accept signatures without the optional parameter.
+/*
+static const uint8_t padding[RSANUMBYTES] = {
+0x00,0x01,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x0e,0x03,0x02,0x1a,0x05,0x00,0x04,0x14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
+};
+*/
+
+// SHA-1 of PKCS1.5 signature padding for 2048 bit, as above.
+// At the location of the bytes of the hash all 00 are hashed.
+static const uint8_t kExpectedPadShaRsa2048[SHA_DIGEST_SIZE] = {
+ 0xdc, 0xbd, 0xbe, 0x42, 0xd5, 0xf5, 0xa7, 0x2e, 0x6e, 0xfc,
+ 0xf5, 0x5d, 0xaf, 0x9d, 0xea, 0x68, 0x7c, 0xfb, 0xf1, 0x67
+};
+
+// Verify a 2048 bit RSA e=65537 PKCS1.5 signature against an expected
+// SHA-1 hash. Returns 0 on failure, 1 on success.
+int RSA_e_f4_verify(const RSAPublicKey* key,
+ const uint8_t* signature,
+ const int len,
+ const uint8_t* sha) {
+ uint8_t buf[RSANUMBYTES];
+ int i;
+
+ if (key->len != RSANUMWORDS) {
+ return 0; // Wrong key passed in.
+ }
+
+ if (len != sizeof(buf)) {
+ return 0; // Wrong input length.
+ }
+
+ if (key->exponent != 65537) {
+ return 0; // Wrong exponent.
+ }
+
+ for (i = 0; i < len; ++i) { // Copy input to local workspace.
+ buf[i] = signature[i];
+ }
+
+ modpowF4(key, buf); // In-place exponentiation.
+
+ // Xor sha portion, so it all becomes 00 iff equal.
+ for (i = len - SHA_DIGEST_SIZE; i < len; ++i) {
+ buf[i] ^= *sha++;
+ }
+
+ // Hash resulting buf, in-place.
+ SHA(buf, len, buf);
+
+ // Compare against expected hash value.
+ for (i = 0; i < SHA_DIGEST_SIZE; ++i) {
+ if (buf[i] != kExpectedPadShaRsa2048[i]) {
+ return 0;
+ }
+ }
+
+ return 1; // All checked out OK.
+}