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-rw-r--r--libc/rsa.c199
1 files changed, 199 insertions, 0 deletions
diff --git a/libc/rsa.c b/libc/rsa.c
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index 0000000..2aea562
--- /dev/null
+++ b/libc/rsa.c
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+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "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 THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS 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 "rsa.h"
+#include "sha.h"
+
+/* a[] -= mod */
+static void subM(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(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(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(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 modpow3(RSAPublicKey *key,
+ uint8_t* inout) {
+ uint32_t a[RSANUMWORDS];
+ uint32_t aR[RSANUMWORDS];
+ uint32_t aaR[RSANUMWORDS];
+ uint32_t *aaa = aR; /* 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 */
+ montMul(key, aaR, aR, aR); /* aaR = aR * aR / R mod M */
+ montMul(key, aaa, aaR, a); /* aaa = aaR * 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 - SHA_DIGEST_SIZE] = {
+ 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
+};
+
+/* Verify a 2048 bit RSA PKCS1.5 signature against an expected SHA-1 hash.
+** Returns 0 on failure, 1 on success.
+*/
+int RSA_verify(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. */
+ }
+
+ for (i = 0; i < len; ++i) {
+ buf[i] = signature[i];
+ }
+
+ modpow3(key, buf);
+
+ /* Check pkcs1.5 padding bytes. */
+ for (i = 0; i < (int) sizeof(padding); ++i) {
+ if (buf[i] != padding[i]) {
+ return 0;
+ }
+ }
+
+ /* Check sha digest matches. */
+ for (; i < len; ++i) {
+ if (buf[i] != *sha++) {
+ return 0;
+ }
+ }
+
+ return 1;
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-05 16:31:35 +0000