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

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2013, Google Inc.
 */

#ifndef USE_HOSTCC
#include <common.h>
#include <fdtdec.h>
#include <asm/types.h>
#include <asm/byteorder.h>
#include <linux/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
83d290c5	1	// SPDX-License-Identifier: GPL-2.0+
fc2f4246 RG	2	/*
fc2f4246 RG	3	* Copyright (c) 2013, Google Inc.
fc2f4246 RG	4	*/
	5
	6	#ifndef USE_HOSTCC
	7	#include <common.h>
	8	#include <fdtdec.h>
	9	#include <asm/types.h>
	10	#include <asm/byteorder.h>
1221ce45	11	#include <linux/errno.h>
fc2f4246 RG	12	#include <asm/types.h>
	13	#include <asm/unaligned.h>
	14	#else
	15	#include "fdt_host.h"
	16	#include "mkimage.h"
	17	#include <fdt_support.h>
	18	#endif
	19	#include <u-boot/rsa.h>
	20	#include <u-boot/rsa-mod-exp.h>
	21
	22	#define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby)))
	23
	24	#define get_unaligned_be32(a) fdt32_to_cpu((uint32_t )a)
	25	#define put_unaligned_be32(a, b) ((uint32_t )(b) = cpu_to_fdt32(a))
	26
	27	/* Default public exponent for backward compatibility */
	28	#define RSA_DEFAULT_PUBEXP 65537
	29
	30	/**
	31	* subtract_modulus() - subtract modulus from the given value
	32	*
	33	* @key: Key containing modulus to subtract
	34	* @num: Number to subtract modulus from, as little endian word array
	35	*/
	36	static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[])
	37	{
	38	int64_t acc = 0;
	39	uint i;
	40
	41	for (i = 0; i < key->len; i++) {
	42	acc += (uint64_t)num[i] - key->modulus[i];
	43	num[i] = (uint32_t)acc;
	44	acc >>= 32;
	45	}
	46	}
	47
	48	/**
	49	* greater_equal_modulus() - check if a value is >= modulus
	50	*
	51	* @key: Key containing modulus to check
	52	* @num: Number to check against modulus, as little endian word array
	53	* @return 0 if num < modulus, 1 if num >= modulus
	54	*/
	55	static int greater_equal_modulus(const struct rsa_public_key *key,
	56	uint32_t num[])
	57	{
	58	int i;
	59
	60	for (i = (int)key->len - 1; i >= 0; i--) {
	61	if (num[i] < key->modulus[i])
	62	return 0;
	63	if (num[i] > key->modulus[i])
	64	return 1;
	65	}
	66
	67	return 1; /* equal */
	68	}
	69
	70	/**
	71	* montgomery_mul_add_step() - Perform montgomery multiply-add step
	72	*
	73	* Operation: montgomery result[] += a * b[] / n0inv % modulus
	74	*
	75	* @key: RSA key
76	* @result: Place to put result, as little endian word array
77	* @a: Multiplier
78	* @b: Multiplicand, as little endian word array
79	*/
80	static void montgomery_mul_add_step(const struct rsa_public_key *key,
81	uint32_t result[], const uint32_t a, const uint32_t b[])
82	{
83	uint64_t acc_a, acc_b;
84	uint32_t d0;
85	uint i;
86
87	acc_a = (uint64_t)a * b[0] + result[0];
88	d0 = (uint32_t)acc_a * key->n0inv;
89	acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a;
90	for (i = 1; i < key->len; i++) {
91	acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i];
92	acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] +
93	(uint32_t)acc_a;
94	result[i - 1] = (uint32_t)acc_b;
95	}
96
97	acc_a = (acc_a >> 32) + (acc_b >> 32);
98
99	result[i - 1] = (uint32_t)acc_a;
100
101	if (acc_a >> 32)
102	subtract_modulus(key, result);
103	}
104
105	/**
106	* montgomery_mul() - Perform montgomery mutitply
107	*
108	* Operation: montgomery result[] = a[] * b[] / n0inv % modulus
109	*
110	* @key: RSA key
111	* @result: Place to put result, as little endian word array
112	* @a: Multiplier, as little endian word array
113	* @b: Multiplicand, as little endian word array
114	*/
115	static void montgomery_mul(const struct rsa_public_key *key,
116	uint32_t result[], uint32_t a[], const uint32_t b[])
117	{
118	uint i;
119
120	for (i = 0; i < key->len; ++i)
121	result[i] = 0;
122	for (i = 0; i < key->len; ++i)
123	montgomery_mul_add_step(key, result, a[i], b);
124	}
125
126	/**
127	* num_pub_exponent_bits() - Number of bits in the public exponent
128	*
129	* @key: RSA key
130	* @num_bits: Storage for the number of public exponent bits
131	*/
132	static int num_public_exponent_bits(const struct rsa_public_key *key,
133	int *num_bits)
134	{
135	uint64_t exponent;
136	int exponent_bits;
137	const uint max_bits = (sizeof(exponent) * 8);
138
139	exponent = key->exponent;
140	exponent_bits = 0;
141
142	if (!exponent) {
143	*num_bits = exponent_bits;
144	return 0;
145	}
146
147	for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits)
148	if (!(exponent >>= 1)) {
149	*num_bits = exponent_bits;
150	return 0;
151	}
152
153	return -EINVAL;
154	}
155
156	/**
157	* is_public_exponent_bit_set() - Check if a bit in the public exponent is set
158	*
159	* @key: RSA key
160	* @pos: The bit position to check
161	*/
162	static int is_public_exponent_bit_set(const struct rsa_public_key *key,
163	int pos)
164	{
165	return key->exponent & (1ULL << pos);
166	}
167
168	/**
169	* pow_mod() - in-place public exponentiation
170	*
171	* @key: RSA key
172	* @inout: Big-endian word array containing value and result
173	*/
174	static int pow_mod(const struct rsa_public_key key, uint32_t inout)
175	{
176	uint32_t result, ptr;
177	uint i;
178	int j, k;
179
180	/* Sanity check for stack size - key->len is in 32-bit words */
181	if (key->len > RSA_MAX_KEY_BITS / 32) {
182	debug("RSA key words %u exceeds maximum %d\n", key->len,
183	RSA_MAX_KEY_BITS / 32);
184	return -EINVAL;
185	}
186
187	uint32_t val[key->len], acc[key->len], tmp[key->len];
188	uint32_t a_scaled[key->len];
189	result = tmp; /* Re-use location. */
190
191	/* Convert from big endian byte array to little endian word array. */
192	for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--)
193	val[i] = get_unaligned_be32(ptr);
194
195	if (0 != num_public_exponent_bits(key, &k))
196	return -EINVAL;
197
198	if (k < 2) {
199	debug("Public exponent is too short (%d bits, minimum 2)\n",
200	k);
201	return -EINVAL;
202	}
203
204	if (!is_public_exponent_bit_set(key, 0)) {
205	debug("LSB of RSA public exponent must be set.\n");
206	return -EINVAL;
207	}
208
209	/* the bit at e[k-1] is 1 by definition, so start with: C := M */
210	montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */
211	/* retain scaled version for intermediate use */
212	memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0]));
213
214	for (j = k - 2; j > 0; --j) {
215	montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
216
217	if (is_public_exponent_bit_set(key, j)) {
218	/* acc = tmp * val / R mod n */
219	montgomery_mul(key, acc, tmp, a_scaled);
220	} else {
221	/* e[j] == 0, copy tmp back to acc for next operation */
222	memcpy(acc, tmp, key->len * sizeof(acc[0]));
223	}
224	}
225
226	/* the bit at e[0] is always 1 */
227	montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
228	montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */
229	memcpy(result, acc, key->len * sizeof(result[0]));
230
231	/* Make sure result < mod; result is at most 1x mod too large. */
232	if (greater_equal_modulus(key, result))
233	subtract_modulus(key, result);
234
235	/* Convert to bigendian byte array */
236	for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++)
237	put_unaligned_be32(result[i], ptr);
238	return 0;
239	}
240
241	static void rsa_convert_big_endian(uint32_t dst, const uint32_t src, int len)
242	{
243	int i;
244
245	for (i = 0; i < len; i++)
246	dst[i] = fdt32_to_cpu(src[len - 1 - i]);
247	}
248
249	int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len,
250	struct key_prop prop, uint8_t out)
251	{
252	struct rsa_public_key key;
253	int ret;
254
255	if (!prop) {
256	debug("%s: Skipping invalid prop", __func__);
257	return -EBADF;
258	}
259	key.n0inv = prop->n0inv;
260	key.len = prop->num_bits;
261
262	if (!prop->public_exponent)
263	key.exponent = RSA_DEFAULT_PUBEXP;
264	else
265	key.exponent =
266	fdt64_to_cpu(((uint64_t )(prop->public_exponent)));
267
268	if (!key.len \|\| !prop->modulus \|\| !prop->rr) {
269	debug("%s: Missing RSA key info", __func__);
270	return -EFAULT;
271	}
272
273	/* Sanity check for stack size */
274	if (key.len > RSA_MAX_KEY_BITS \|\| key.len < RSA_MIN_KEY_BITS) {
275	debug("RSA key bits %u outside allowed range %d..%d\n",
276	key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS);
277	return -EFAULT;
278	}
279	key.len /= sizeof(uint32_t) * 8;
280	uint32_t key1[key.len], key2[key.len];
281
282	key.modulus = key1;
283	key.rr = key2;
284	rsa_convert_big_endian(key.modulus, (uint32_t *)prop->modulus, key.len);
285	rsa_convert_big_endian(key.rr, (uint32_t *)prop->rr, key.len);
286	if (!key.modulus \|\| !key.rr) {
287	debug("%s: Out of memory", __func__);
288	return -ENOMEM;
289	}
290
291	uint32_t buf[sig_len / sizeof(uint32_t)];
292
293	memcpy(buf, sig, sig_len);
294
295	ret = pow_mod(&key, buf);
296	if (ret)
297	return ret;
298
299	memcpy(out, buf, sig_len);
300
301	return 0;
302	}