1 /*
2  * Copyright (c) 2013, Kenneth MacKay
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions are
7  * met:
8  *  * Redistributions of source code must retain the above copyright
9  *   notice, this list of conditions and the following disclaimer.
10  *  * Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
15  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
16  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
17  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
18  * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
19  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
20  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 #ifndef _CRYPTO_ECC_H
27 #define _CRYPTO_ECC_H
28 
29 #include <crypto/ecc_curve.h>
30 #include <asm/unaligned.h>
31 
32 /* One digit is u64 qword. */
33 #define ECC_CURVE_NIST_P192_DIGITS  3
34 #define ECC_CURVE_NIST_P256_DIGITS  4
35 #define ECC_CURVE_NIST_P384_DIGITS  6
36 #define ECC_MAX_DIGITS              (512 / 64) /* due to ecrdsa */
37 
38 #define ECC_DIGITS_TO_BYTES_SHIFT 3
39 
40 #define ECC_MAX_BYTES (ECC_MAX_DIGITS << ECC_DIGITS_TO_BYTES_SHIFT)
41 
42 #define ECC_POINT_INIT(x, y, ndigits)	(struct ecc_point) { x, y, ndigits }
43 
44 /**
45  * ecc_swap_digits() - Copy ndigits from big endian array to native array
46  * @in:       Input array
47  * @out:      Output array
48  * @ndigits:  Number of digits to copy
49  */
ecc_swap_digits(const void * in,u64 * out,unsigned int ndigits)50 static inline void ecc_swap_digits(const void *in, u64 *out, unsigned int ndigits)
51 {
52 	const __be64 *src = (__force __be64 *)in;
53 	int i;
54 
55 	for (i = 0; i < ndigits; i++)
56 		out[i] = get_unaligned_be64(&src[ndigits - 1 - i]);
57 }
58 
59 /**
60  * ecc_is_key_valid() - Validate a given ECDH private key
61  *
62  * @curve_id:		id representing the curve to use
63  * @ndigits:		curve's number of digits
64  * @private_key:	private key to be used for the given curve
65  * @private_key_len:	private key length
66  *
67  * Returns 0 if the key is acceptable, a negative value otherwise
68  */
69 int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,
70 		     const u64 *private_key, unsigned int private_key_len);
71 
72 /**
73  * ecc_gen_privkey() -  Generates an ECC private key.
74  * The private key is a random integer in the range 0 < random < n, where n is a
75  * prime that is the order of the cyclic subgroup generated by the distinguished
76  * point G.
77  * @curve_id:		id representing the curve to use
78  * @ndigits:		curve number of digits
79  * @private_key:	buffer for storing the generated private key
80  *
81  * Returns 0 if the private key was generated successfully, a negative value
82  * if an error occurred.
83  */
84 int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey);
85 
86 /**
87  * ecc_make_pub_key() - Compute an ECC public key
88  *
89  * @curve_id:		id representing the curve to use
90  * @ndigits:		curve's number of digits
91  * @private_key:	pregenerated private key for the given curve
92  * @public_key:		buffer for storing the generated public key
93  *
94  * Returns 0 if the public key was generated successfully, a negative value
95  * if an error occurred.
96  */
97 int ecc_make_pub_key(const unsigned int curve_id, unsigned int ndigits,
98 		     const u64 *private_key, u64 *public_key);
99 
100 /**
101  * crypto_ecdh_shared_secret() - Compute a shared secret
102  *
103  * @curve_id:		id representing the curve to use
104  * @ndigits:		curve's number of digits
105  * @private_key:	private key of part A
106  * @public_key:		public key of counterpart B
107  * @secret:		buffer for storing the calculated shared secret
108  *
109  * Note: It is recommended that you hash the result of crypto_ecdh_shared_secret
110  * before using it for symmetric encryption or HMAC.
111  *
112  * Returns 0 if the shared secret was generated successfully, a negative value
113  * if an error occurred.
114  */
115 int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
116 			      const u64 *private_key, const u64 *public_key,
117 			      u64 *secret);
118 
119 /**
120  * ecc_is_pubkey_valid_partial() - Partial public key validation
121  *
122  * @curve:		elliptic curve domain parameters
123  * @pk:			public key as a point
124  *
125  * Valdiate public key according to SP800-56A section 5.6.2.3.4 ECC Partial
126  * Public-Key Validation Routine.
127  *
128  * Note: There is no check that the public key is in the correct elliptic curve
129  * subgroup.
130  *
131  * Return: 0 if validation is successful, -EINVAL if validation is failed.
132  */
133 int ecc_is_pubkey_valid_partial(const struct ecc_curve *curve,
134 				struct ecc_point *pk);
135 
136 /**
137  * ecc_is_pubkey_valid_full() - Full public key validation
138  *
139  * @curve:		elliptic curve domain parameters
140  * @pk:			public key as a point
141  *
142  * Valdiate public key according to SP800-56A section 5.6.2.3.3 ECC Full
143  * Public-Key Validation Routine.
144  *
145  * Return: 0 if validation is successful, -EINVAL if validation is failed.
146  */
147 int ecc_is_pubkey_valid_full(const struct ecc_curve *curve,
148 			     struct ecc_point *pk);
149 
150 /**
151  * vli_is_zero() - Determine is vli is zero
152  *
153  * @vli:		vli to check.
154  * @ndigits:		length of the @vli
155  */
156 bool vli_is_zero(const u64 *vli, unsigned int ndigits);
157 
158 /**
159  * vli_cmp() - compare left and right vlis
160  *
161  * @left:		vli
162  * @right:		vli
163  * @ndigits:		length of both vlis
164  *
165  * Returns sign of @left - @right, i.e. -1 if @left < @right,
166  * 0 if @left == @right, 1 if @left > @right.
167  */
168 int vli_cmp(const u64 *left, const u64 *right, unsigned int ndigits);
169 
170 /**
171  * vli_sub() - Subtracts right from left
172  *
173  * @result:		where to write result
174  * @left:		vli
175  * @right		vli
176  * @ndigits:		length of all vlis
177  *
178  * Note: can modify in-place.
179  *
180  * Return: carry bit.
181  */
182 u64 vli_sub(u64 *result, const u64 *left, const u64 *right,
183 	    unsigned int ndigits);
184 
185 /**
186  * vli_from_be64() - Load vli from big-endian u64 array
187  *
188  * @dest:		destination vli
189  * @src:		source array of u64 BE values
190  * @ndigits:		length of both vli and array
191  */
192 void vli_from_be64(u64 *dest, const void *src, unsigned int ndigits);
193 
194 /**
195  * vli_from_le64() - Load vli from little-endian u64 array
196  *
197  * @dest:		destination vli
198  * @src:		source array of u64 LE values
199  * @ndigits:		length of both vli and array
200  */
201 void vli_from_le64(u64 *dest, const void *src, unsigned int ndigits);
202 
203 /**
204  * vli_mod_inv() - Modular inversion
205  *
206  * @result:		where to write vli number
207  * @input:		vli value to operate on
208  * @mod:		modulus
209  * @ndigits:		length of all vlis
210  */
211 void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
212 		 unsigned int ndigits);
213 
214 /**
215  * vli_mod_mult_slow() - Modular multiplication
216  *
217  * @result:		where to write result value
218  * @left:		vli number to multiply with @right
219  * @right:		vli number to multiply with @left
220  * @mod:		modulus
221  * @ndigits:		length of all vlis
222  *
223  * Note: Assumes that mod is big enough curve order.
224  */
225 void vli_mod_mult_slow(u64 *result, const u64 *left, const u64 *right,
226 		       const u64 *mod, unsigned int ndigits);
227 
228 /**
229  * vli_num_bits() - Counts the number of bits required for vli.
230  *
231  * @vli:		vli to check.
232  * @ndigits:		Length of the @vli
233  *
234  * Return: The number of bits required to represent @vli.
235  */
236 unsigned int vli_num_bits(const u64 *vli, unsigned int ndigits);
237 
238 /**
239  * ecc_aloc_point() - Allocate ECC point.
240  *
241  * @ndigits:		Length of vlis in u64 qwords.
242  *
243  * Return: Pointer to the allocated point or NULL if allocation failed.
244  */
245 struct ecc_point *ecc_alloc_point(unsigned int ndigits);
246 
247 /**
248  * ecc_free_point() - Free ECC point.
249  *
250  * @p:			The point to free.
251  */
252 void ecc_free_point(struct ecc_point *p);
253 
254 /**
255  * ecc_point_is_zero() - Check if point is zero.
256  *
257  * @p:			Point to check for zero.
258  *
259  * Return: true if point is the point at infinity, false otherwise.
260  */
261 bool ecc_point_is_zero(const struct ecc_point *point);
262 
263 /**
264  * ecc_point_mult_shamir() - Add two points multiplied by scalars
265  *
266  * @result:		resulting point
267  * @x:			scalar to multiply with @p
268  * @p:			point to multiply with @x
269  * @y:			scalar to multiply with @q
270  * @q:			point to multiply with @y
271  * @curve:		curve
272  *
273  * Returns result = x * p + x * q over the curve.
274  * This works faster than two multiplications and addition.
275  */
276 void ecc_point_mult_shamir(const struct ecc_point *result,
277 			   const u64 *x, const struct ecc_point *p,
278 			   const u64 *y, const struct ecc_point *q,
279 			   const struct ecc_curve *curve);
280 
281 #endif
282