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-rw-r--r--lib/rsa/rsa-mod-exp.c303
1 files changed, 303 insertions, 0 deletions
diff --git a/lib/rsa/rsa-mod-exp.c b/lib/rsa/rsa-mod-exp.c
new file mode 100644
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+++ b/lib/rsa/rsa-mod-exp.c
@@ -0,0 +1,303 @@
+/*
+ * Copyright (c) 2013, Google Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#ifndef USE_HOSTCC
+#include <common.h>
+#include <fdtdec.h>
+#include <asm/types.h>
+#include <asm/byteorder.h>
+#include <asm/errno.h>
+#include <asm/types.h>
+#include <asm/unaligned.h>
+#else
+#include "fdt_host.h"
+#include "mkimage.h"
+#include <fdt_support.h>
+#endif
+#include <u-boot/rsa.h>
+#include <u-boot/rsa-mod-exp.h>
+
+#define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby)))
+
+#define get_unaligned_be32(a) fdt32_to_cpu(*(uint32_t *)a)
+#define put_unaligned_be32(a, b) (*(uint32_t *)(b) = cpu_to_fdt32(a))
+
+/* Default public exponent for backward compatibility */
+#define RSA_DEFAULT_PUBEXP 65537
+
+/**
+ * subtract_modulus() - subtract modulus from the given value
+ *
+ * @key: Key containing modulus to subtract
+ * @num: Number to subtract modulus from, as little endian word array
+ */
+static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[])
+{
+ int64_t acc = 0;
+ uint i;
+
+ for (i = 0; i < key->len; i++) {
+ acc += (uint64_t)num[i] - key->modulus[i];
+ num[i] = (uint32_t)acc;
+ acc >>= 32;
+ }
+}
+
+/**
+ * greater_equal_modulus() - check if a value is >= modulus
+ *
+ * @key: Key containing modulus to check
+ * @num: Number to check against modulus, as little endian word array
+ * @return 0 if num < modulus, 1 if num >= modulus
+ */
+static int greater_equal_modulus(const struct rsa_public_key *key,
+ uint32_t num[])
+{
+ int i;
+
+ for (i = (int)key->len - 1; i >= 0; i--) {
+ if (num[i] < key->modulus[i])
+ return 0;
+ if (num[i] > key->modulus[i])
+ return 1;
+ }
+
+ return 1; /* equal */
+}
+
+/**
+ * montgomery_mul_add_step() - Perform montgomery multiply-add step
+ *
+ * Operation: montgomery result[] += a * b[] / n0inv % modulus
+ *
+ * @key: RSA key
+ * @result: Place to put result, as little endian word array
+ * @a: Multiplier
+ * @b: Multiplicand, as little endian word array
+ */
+static void montgomery_mul_add_step(const struct rsa_public_key *key,
+ uint32_t result[], const uint32_t a, const uint32_t b[])
+{
+ uint64_t acc_a, acc_b;
+ uint32_t d0;
+ uint i;
+
+ acc_a = (uint64_t)a * b[0] + result[0];
+ d0 = (uint32_t)acc_a * key->n0inv;
+ acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a;
+ for (i = 1; i < key->len; i++) {
+ acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i];
+ acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] +
+ (uint32_t)acc_a;
+ result[i - 1] = (uint32_t)acc_b;
+ }
+
+ acc_a = (acc_a >> 32) + (acc_b >> 32);
+
+ result[i - 1] = (uint32_t)acc_a;
+
+ if (acc_a >> 32)
+ subtract_modulus(key, result);
+}
+
+/**
+ * montgomery_mul() - Perform montgomery mutitply
+ *
+ * Operation: montgomery result[] = a[] * b[] / n0inv % modulus
+ *
+ * @key: RSA key
+ * @result: Place to put result, as little endian word array
+ * @a: Multiplier, as little endian word array
+ * @b: Multiplicand, as little endian word array
+ */
+static void montgomery_mul(const struct rsa_public_key *key,
+ uint32_t result[], uint32_t a[], const uint32_t b[])
+{
+ uint i;
+
+ for (i = 0; i < key->len; ++i)
+ result[i] = 0;
+ for (i = 0; i < key->len; ++i)
+ montgomery_mul_add_step(key, result, a[i], b);
+}
+
+/**
+ * num_pub_exponent_bits() - Number of bits in the public exponent
+ *
+ * @key: RSA key
+ * @num_bits: Storage for the number of public exponent bits
+ */
+static int num_public_exponent_bits(const struct rsa_public_key *key,
+ int *num_bits)
+{
+ uint64_t exponent;
+ int exponent_bits;
+ const uint max_bits = (sizeof(exponent) * 8);
+
+ exponent = key->exponent;
+ exponent_bits = 0;
+
+ if (!exponent) {
+ *num_bits = exponent_bits;
+ return 0;
+ }
+
+ for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits)
+ if (!(exponent >>= 1)) {
+ *num_bits = exponent_bits;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+/**
+ * is_public_exponent_bit_set() - Check if a bit in the public exponent is set
+ *
+ * @key: RSA key
+ * @pos: The bit position to check
+ */
+static int is_public_exponent_bit_set(const struct rsa_public_key *key,
+ int pos)
+{
+ return key->exponent & (1ULL << pos);
+}
+
+/**
+ * pow_mod() - in-place public exponentiation
+ *
+ * @key: RSA key
+ * @inout: Big-endian word array containing value and result
+ */
+static int pow_mod(const struct rsa_public_key *key, uint32_t *inout)
+{
+ uint32_t *result, *ptr;
+ uint i;
+ int j, k;
+
+ /* Sanity check for stack size - key->len is in 32-bit words */
+ if (key->len > RSA_MAX_KEY_BITS / 32) {
+ debug("RSA key words %u exceeds maximum %d\n", key->len,
+ RSA_MAX_KEY_BITS / 32);
+ return -EINVAL;
+ }
+
+ uint32_t val[key->len], acc[key->len], tmp[key->len];
+ uint32_t a_scaled[key->len];
+ result = tmp; /* Re-use location. */
+
+ /* Convert from big endian byte array to little endian word array. */
+ for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--)
+ val[i] = get_unaligned_be32(ptr);
+
+ if (0 != num_public_exponent_bits(key, &k))
+ return -EINVAL;
+
+ if (k < 2) {
+ debug("Public exponent is too short (%d bits, minimum 2)\n",
+ k);
+ return -EINVAL;
+ }
+
+ if (!is_public_exponent_bit_set(key, 0)) {
+ debug("LSB of RSA public exponent must be set.\n");
+ return -EINVAL;
+ }
+
+ /* the bit at e[k-1] is 1 by definition, so start with: C := M */
+ montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */
+ /* retain scaled version for intermediate use */
+ memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0]));
+
+ for (j = k - 2; j > 0; --j) {
+ montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
+
+ if (is_public_exponent_bit_set(key, j)) {
+ /* acc = tmp * val / R mod n */
+ montgomery_mul(key, acc, tmp, a_scaled);
+ } else {
+ /* e[j] == 0, copy tmp back to acc for next operation */
+ memcpy(acc, tmp, key->len * sizeof(acc[0]));
+ }
+ }
+
+ /* the bit at e[0] is always 1 */
+ montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
+ montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */
+ memcpy(result, acc, key->len * sizeof(result[0]));
+
+ /* Make sure result < mod; result is at most 1x mod too large. */
+ if (greater_equal_modulus(key, result))
+ subtract_modulus(key, result);
+
+ /* Convert to bigendian byte array */
+ for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++)
+ put_unaligned_be32(result[i], ptr);
+ return 0;
+}
+
+static void rsa_convert_big_endian(uint32_t *dst, const uint32_t *src, int len)
+{
+ int i;
+
+ for (i = 0; i < len; i++)
+ dst[i] = fdt32_to_cpu(src[len - 1 - i]);
+}
+
+int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len,
+ struct key_prop *prop, uint8_t *out)
+{
+ struct rsa_public_key key;
+ int ret;
+
+ if (!prop) {
+ debug("%s: Skipping invalid prop", __func__);
+ return -EBADF;
+ }
+ key.n0inv = prop->n0inv;
+ key.len = prop->num_bits;
+
+ if (!prop->public_exponent)
+ key.exponent = RSA_DEFAULT_PUBEXP;
+ else
+ key.exponent =
+ fdt64_to_cpu(*((uint64_t *)(prop->public_exponent)));
+
+ if (!key.len || !prop->modulus || !prop->rr) {
+ debug("%s: Missing RSA key info", __func__);
+ return -EFAULT;
+ }
+
+ /* Sanity check for stack size */
+ if (key.len > RSA_MAX_KEY_BITS || key.len < RSA_MIN_KEY_BITS) {
+ debug("RSA key bits %u outside allowed range %d..%d\n",
+ key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS);
+ return -EFAULT;
+ }
+ key.len /= sizeof(uint32_t) * 8;
+ uint32_t key1[key.len], key2[key.len];
+
+ key.modulus = key1;
+ key.rr = key2;
+ rsa_convert_big_endian(key.modulus, (uint32_t *)prop->modulus, key.len);
+ rsa_convert_big_endian(key.rr, (uint32_t *)prop->rr, key.len);
+ if (!key.modulus || !key.rr) {
+ debug("%s: Out of memory", __func__);
+ return -ENOMEM;
+ }
+
+ uint32_t buf[sig_len / sizeof(uint32_t)];
+
+ memcpy(buf, sig, sig_len);
+
+ ret = pow_mod(&key, buf);
+ if (ret)
+ return ret;
+
+ memcpy(out, buf, sig_len);
+
+ return 0;
+}