[people/ms/u-boot.git] / lib / rsa / rsa-mod-exp.c

/*
 * 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;
}
Commit	Line	Data
fc2f4246 RG	1	/*
	2	* Copyright (c) 2013, Google Inc.
	3	*
	4	* SPDX-License-Identifier: GPL-2.0+
	5	*/
	6
	7	#ifndef USE_HOSTCC
	8	#include <common.h>
	9	#include <fdtdec.h>
	10	#include <asm/types.h>
	11	#include <asm/byteorder.h>
	12	#include <asm/errno.h>
	13	#include <asm/types.h>
	14	#include <asm/unaligned.h>
	15	#else
	16	#include "fdt_host.h"
	17	#include "mkimage.h"
	18	#include <fdt_support.h>
	19	#endif
	20	#include <u-boot/rsa.h>
	21	#include <u-boot/rsa-mod-exp.h>
	22
	23	#define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby)))
	24
	25	#define get_unaligned_be32(a) fdt32_to_cpu((uint32_t )a)
	26	#define put_unaligned_be32(a, b) ((uint32_t )(b) = cpu_to_fdt32(a))
	27
	28	/* Default public exponent for backward compatibility */
	29	#define RSA_DEFAULT_PUBEXP 65537
	30
	31	/**
	32	* subtract_modulus() - subtract modulus from the given value
	33	*
	34	* @key: Key containing modulus to subtract
	35	* @num: Number to subtract modulus from, as little endian word array
	36	*/
	37	static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[])
	38	{
	39	int64_t acc = 0;
	40	uint i;
	41
	42	for (i = 0; i < key->len; i++) {
	43	acc += (uint64_t)num[i] - key->modulus[i];
	44	num[i] = (uint32_t)acc;
	45	acc >>= 32;
	46	}
	47	}
	48
	49	/**
	50	* greater_equal_modulus() - check if a value is >= modulus
	51	*
	52	* @key: Key containing modulus to check
	53	* @num: Number to check against modulus, as little endian word array
	54	* @return 0 if num < modulus, 1 if num >= modulus
	55	*/
	56	static int greater_equal_modulus(const struct rsa_public_key *key,
	57	uint32_t num[])
	58	{
	59	int i;
	60
	61	for (i = (int)key->len - 1; i >= 0; i--) {
	62	if (num[i] < key->modulus[i])
	63	return 0;
	64	if (num[i] > key->modulus[i])
65	return 1;
66	}
67
68	return 1; /* equal */
69	}
70
71	/**
72	* montgomery_mul_add_step() - Perform montgomery multiply-add step
73	*
74	* Operation: montgomery result[] += a * b[] / n0inv % modulus
75	*
76	* @key: RSA key
77	* @result: Place to put result, as little endian word array
78	* @a: Multiplier
79	* @b: Multiplicand, as little endian word array
80	*/
81	static void montgomery_mul_add_step(const struct rsa_public_key *key,
82	uint32_t result[], const uint32_t a, const uint32_t b[])
83	{
84	uint64_t acc_a, acc_b;
85	uint32_t d0;
86	uint i;
87
88	acc_a = (uint64_t)a * b[0] + result[0];
89	d0 = (uint32_t)acc_a * key->n0inv;
90	acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a;
91	for (i = 1; i < key->len; i++) {
92	acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i];
93	acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] +
94	(uint32_t)acc_a;
95	result[i - 1] = (uint32_t)acc_b;
96	}
97
98	acc_a = (acc_a >> 32) + (acc_b >> 32);
99
100	result[i - 1] = (uint32_t)acc_a;
101
102	if (acc_a >> 32)
103	subtract_modulus(key, result);
104	}
105
106	/**
107	* montgomery_mul() - Perform montgomery mutitply
108	*
109	* Operation: montgomery result[] = a[] * b[] / n0inv % modulus
110	*
111	* @key: RSA key
112	* @result: Place to put result, as little endian word array
113	* @a: Multiplier, as little endian word array
114	* @b: Multiplicand, as little endian word array
115	*/
116	static void montgomery_mul(const struct rsa_public_key *key,
117	uint32_t result[], uint32_t a[], const uint32_t b[])
118	{
119	uint i;
120
121	for (i = 0; i < key->len; ++i)
122	result[i] = 0;
123	for (i = 0; i < key->len; ++i)
124	montgomery_mul_add_step(key, result, a[i], b);
125	}
126
127	/**
128	* num_pub_exponent_bits() - Number of bits in the public exponent
129	*
130	* @key: RSA key
131	* @num_bits: Storage for the number of public exponent bits
132	*/
133	static int num_public_exponent_bits(const struct rsa_public_key *key,
134	int *num_bits)
135	{
136	uint64_t exponent;
137	int exponent_bits;
138	const uint max_bits = (sizeof(exponent) * 8);
139
140	exponent = key->exponent;
141	exponent_bits = 0;
142
143	if (!exponent) {
144	*num_bits = exponent_bits;
145	return 0;
146	}
147
148	for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits)
149	if (!(exponent >>= 1)) {
150	*num_bits = exponent_bits;
151	return 0;
152	}
153
154	return -EINVAL;
155	}
156
157	/**
158	* is_public_exponent_bit_set() - Check if a bit in the public exponent is set
159	*
160	* @key: RSA key
161	* @pos: The bit position to check
162	*/
163	static int is_public_exponent_bit_set(const struct rsa_public_key *key,
164	int pos)
165	{
166	return key->exponent & (1ULL << pos);
167	}
168
169	/**
170	* pow_mod() - in-place public exponentiation
171	*
172	* @key: RSA key
173	* @inout: Big-endian word array containing value and result
174	*/
175	static int pow_mod(const struct rsa_public_key key, uint32_t inout)
176	{
177	uint32_t result, ptr;
178	uint i;
179	int j, k;
180
181	/* Sanity check for stack size - key->len is in 32-bit words */
182	if (key->len > RSA_MAX_KEY_BITS / 32) {
183	debug("RSA key words %u exceeds maximum %d\n", key->len,
184	RSA_MAX_KEY_BITS / 32);
185	return -EINVAL;
186	}
187
188	uint32_t val[key->len], acc[key->len], tmp[key->len];
189	uint32_t a_scaled[key->len];
190	result = tmp; /* Re-use location. */
191
192	/* Convert from big endian byte array to little endian word array. */
193	for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--)
194	val[i] = get_unaligned_be32(ptr);
195
196	if (0 != num_public_exponent_bits(key, &k))
197	return -EINVAL;
198
199	if (k < 2) {
200	debug("Public exponent is too short (%d bits, minimum 2)\n",
201	k);
202	return -EINVAL;
203	}
204
205	if (!is_public_exponent_bit_set(key, 0)) {
206	debug("LSB of RSA public exponent must be set.\n");
207	return -EINVAL;
208	}
209
210	/* the bit at e[k-1] is 1 by definition, so start with: C := M */
211	montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */
212	/* retain scaled version for intermediate use */
213	memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0]));
214
215	for (j = k - 2; j > 0; --j) {
216	montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
217
218	if (is_public_exponent_bit_set(key, j)) {
219	/* acc = tmp * val / R mod n */
220	montgomery_mul(key, acc, tmp, a_scaled);
221	} else {
222	/* e[j] == 0, copy tmp back to acc for next operation */
223	memcpy(acc, tmp, key->len * sizeof(acc[0]));
224	}
225	}
226
227	/* the bit at e[0] is always 1 */
228	montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
229	montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */
230	memcpy(result, acc, key->len * sizeof(result[0]));
231
232	/* Make sure result < mod; result is at most 1x mod too large. */
233	if (greater_equal_modulus(key, result))
234	subtract_modulus(key, result);
235
236	/* Convert to bigendian byte array */
237	for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++)
238	put_unaligned_be32(result[i], ptr);
239	return 0;
240	}
241
242	static void rsa_convert_big_endian(uint32_t dst, const uint32_t src, int len)
243	{
244	int i;
245
246	for (i = 0; i < len; i++)
247	dst[i] = fdt32_to_cpu(src[len - 1 - i]);
248	}
249
250	int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len,
251	struct key_prop prop, uint8_t out)
252	{
253	struct rsa_public_key key;
254	int ret;
255
256	if (!prop) {
257	debug("%s: Skipping invalid prop", __func__);
258	return -EBADF;
259	}
260	key.n0inv = prop->n0inv;
261	key.len = prop->num_bits;
262
263	if (!prop->public_exponent)
264	key.exponent = RSA_DEFAULT_PUBEXP;
265	else
266	key.exponent =
267	fdt64_to_cpu(((uint64_t )(prop->public_exponent)));
268
269	if (!key.len \|\| !prop->modulus \|\| !prop->rr) {
270	debug("%s: Missing RSA key info", __func__);
271	return -EFAULT;
272	}
273
274	/* Sanity check for stack size */
275	if (key.len > RSA_MAX_KEY_BITS \|\| key.len < RSA_MIN_KEY_BITS) {
276	debug("RSA key bits %u outside allowed range %d..%d\n",
277	key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS);
278	return -EFAULT;
279	}
280	key.len /= sizeof(uint32_t) * 8;
281	uint32_t key1[key.len], key2[key.len];
282
283	key.modulus = key1;
284	key.rr = key2;
285	rsa_convert_big_endian(key.modulus, (uint32_t *)prop->modulus, key.len);
286	rsa_convert_big_endian(key.rr, (uint32_t *)prop->rr, key.len);
287	if (!key.modulus \|\| !key.rr) {
288	debug("%s: Out of memory", __func__);
289	return -ENOMEM;
290	}
291
292	uint32_t buf[sig_len / sizeof(uint32_t)];
293
294	memcpy(buf, sig, sig_len);
295
296	ret = pow_mod(&key, buf);
297	if (ret)
298	return ret;
299
300	memcpy(out, buf, sig_len);
301
302	return 0;
303	}