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 /* One digit is u64 qword. */
30 #define ECC_CURVE_NIST_P192_DIGITS 3
31 #define ECC_CURVE_NIST_P256_DIGITS 4
32 #define ECC_CURVE_NIST_P384_DIGITS 6
33 #define ECC_MAX_DIGITS (512 / 64) /* due to ecrdsa */
34
35 #define ECC_DIGITS_TO_BYTES_SHIFT 3
36
37 #define ECC_MAX_BYTES (ECC_MAX_DIGITS << ECC_DIGITS_TO_BYTES_SHIFT)
38
39 /**
40 * struct ecc_point - elliptic curve point in affine coordinates
41 *
42 * @x: X coordinate in vli form.
43 * @y: Y coordinate in vli form.
44 * @ndigits: Length of vlis in u64 qwords.
45 */
46 struct ecc_point {
47 u64 *x;
48 u64 *y;
49 u8 ndigits;
50 };
51
52 #define ECC_POINT_INIT(x, y, ndigits) (struct ecc_point) { x, y, ndigits }
53
54 /**
55 * struct ecc_curve - definition of elliptic curve
56 *
57 * @name: Short name of the curve.
58 * @g: Generator point of the curve.
59 * @p: Prime number, if Barrett's reduction is used for this curve
60 * pre-calculated value 'mu' is appended to the @p after ndigits.
61 * Use of Barrett's reduction is heuristically determined in
62 * vli_mmod_fast().
63 * @n: Order of the curve group.
64 * @a: Curve parameter a.
65 * @b: Curve parameter b.
66 */
67 struct ecc_curve {
68 char *name;
69 struct ecc_point g;
70 u64 *p;
71 u64 *n;
72 u64 *a;
73 u64 *b;
74 };
75
76 /**
77 * ecc_swap_digits() - Copy ndigits from big endian array to native array
78 * @in: Input array
79 * @out: Output array
80 * @ndigits: Number of digits to copy
81 */
ecc_swap_digits(const u64 * in,u64 * out,unsigned int ndigits)82 static inline void ecc_swap_digits(const u64 *in, u64 *out, unsigned int ndigits)
83 {
84 const __be64 *src = (__force __be64 *)in;
85 int i;
86
87 for (i = 0; i < ndigits; i++)
88 out[i] = be64_to_cpu(src[ndigits - 1 - i]);
89 }
90
91 /**
92 * ecc_get_curve() - Get a curve given its curve_id
93 * @curve_id: Id of the curve
94 *
95 * Returns pointer to the curve data, NULL if curve is not available
96 */
97 const struct ecc_curve *ecc_get_curve(unsigned int curve_id);
98
99 /**
100 * ecc_is_key_valid() - Validate a given ECDH private key
101 *
102 * @curve_id: id representing the curve to use
103 * @ndigits: curve's number of digits
104 * @private_key: private key to be used for the given curve
105 * @private_key_len: private key length
106 *
107 * Returns 0 if the key is acceptable, a negative value otherwise
108 */
109 int ecc_is_key_valid(unsigned int curve_id, unsigned int ndigits,
110 const u64 *private_key, unsigned int private_key_len);
111
112 /**
113 * ecc_gen_privkey() - Generates an ECC private key.
114 * The private key is a random integer in the range 0 < random < n, where n is a
115 * prime that is the order of the cyclic subgroup generated by the distinguished
116 * point G.
117 * @curve_id: id representing the curve to use
118 * @ndigits: curve number of digits
119 * @private_key: buffer for storing the generated private key
120 *
121 * Returns 0 if the private key was generated successfully, a negative value
122 * if an error occurred.
123 */
124 int ecc_gen_privkey(unsigned int curve_id, unsigned int ndigits, u64 *privkey);
125
126 /**
127 * ecc_make_pub_key() - Compute an ECC public key
128 *
129 * @curve_id: id representing the curve to use
130 * @ndigits: curve's number of digits
131 * @private_key: pregenerated private key for the given curve
132 * @public_key: buffer for storing the generated public key
133 *
134 * Returns 0 if the public key was generated successfully, a negative value
135 * if an error occurred.
136 */
137 int ecc_make_pub_key(const unsigned int curve_id, unsigned int ndigits,
138 const u64 *private_key, u64 *public_key);
139
140 /**
141 * crypto_ecdh_shared_secret() - Compute a shared secret
142 *
143 * @curve_id: id representing the curve to use
144 * @ndigits: curve's number of digits
145 * @private_key: private key of part A
146 * @public_key: public key of counterpart B
147 * @secret: buffer for storing the calculated shared secret
148 *
149 * Note: It is recommended that you hash the result of crypto_ecdh_shared_secret
150 * before using it for symmetric encryption or HMAC.
151 *
152 * Returns 0 if the shared secret was generated successfully, a negative value
153 * if an error occurred.
154 */
155 int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits,
156 const u64 *private_key, const u64 *public_key,
157 u64 *secret);
158
159 /**
160 * ecc_is_pubkey_valid_partial() - Partial public key validation
161 *
162 * @curve: elliptic curve domain parameters
163 * @pk: public key as a point
164 *
165 * Valdiate public key according to SP800-56A section 5.6.2.3.4 ECC Partial
166 * Public-Key Validation Routine.
167 *
168 * Note: There is no check that the public key is in the correct elliptic curve
169 * subgroup.
170 *
171 * Return: 0 if validation is successful, -EINVAL if validation is failed.
172 */
173 int ecc_is_pubkey_valid_partial(const struct ecc_curve *curve,
174 struct ecc_point *pk);
175
176 /**
177 * ecc_is_pubkey_valid_full() - Full public key validation
178 *
179 * @curve: elliptic curve domain parameters
180 * @pk: public key as a point
181 *
182 * Valdiate public key according to SP800-56A section 5.6.2.3.3 ECC Full
183 * Public-Key Validation Routine.
184 *
185 * Return: 0 if validation is successful, -EINVAL if validation is failed.
186 */
187 int ecc_is_pubkey_valid_full(const struct ecc_curve *curve,
188 struct ecc_point *pk);
189
190 /**
191 * vli_is_zero() - Determine is vli is zero
192 *
193 * @vli: vli to check.
194 * @ndigits: length of the @vli
195 */
196 bool vli_is_zero(const u64 *vli, unsigned int ndigits);
197
198 /**
199 * vli_cmp() - compare left and right vlis
200 *
201 * @left: vli
202 * @right: vli
203 * @ndigits: length of both vlis
204 *
205 * Returns sign of @left - @right, i.e. -1 if @left < @right,
206 * 0 if @left == @right, 1 if @left > @right.
207 */
208 int vli_cmp(const u64 *left, const u64 *right, unsigned int ndigits);
209
210 /**
211 * vli_sub() - Subtracts right from left
212 *
213 * @result: where to write result
214 * @left: vli
215 * @right vli
216 * @ndigits: length of all vlis
217 *
218 * Note: can modify in-place.
219 *
220 * Return: carry bit.
221 */
222 u64 vli_sub(u64 *result, const u64 *left, const u64 *right,
223 unsigned int ndigits);
224
225 /**
226 * vli_from_be64() - Load vli from big-endian u64 array
227 *
228 * @dest: destination vli
229 * @src: source array of u64 BE values
230 * @ndigits: length of both vli and array
231 */
232 void vli_from_be64(u64 *dest, const void *src, unsigned int ndigits);
233
234 /**
235 * vli_from_le64() - Load vli from little-endian u64 array
236 *
237 * @dest: destination vli
238 * @src: source array of u64 LE values
239 * @ndigits: length of both vli and array
240 */
241 void vli_from_le64(u64 *dest, const void *src, unsigned int ndigits);
242
243 /**
244 * vli_mod_inv() - Modular inversion
245 *
246 * @result: where to write vli number
247 * @input: vli value to operate on
248 * @mod: modulus
249 * @ndigits: length of all vlis
250 */
251 void vli_mod_inv(u64 *result, const u64 *input, const u64 *mod,
252 unsigned int ndigits);
253
254 /**
255 * vli_mod_mult_slow() - Modular multiplication
256 *
257 * @result: where to write result value
258 * @left: vli number to multiply with @right
259 * @right: vli number to multiply with @left
260 * @mod: modulus
261 * @ndigits: length of all vlis
262 *
263 * Note: Assumes that mod is big enough curve order.
264 */
265 void vli_mod_mult_slow(u64 *result, const u64 *left, const u64 *right,
266 const u64 *mod, unsigned int ndigits);
267
268 /**
269 * ecc_point_mult_shamir() - Add two points multiplied by scalars
270 *
271 * @result: resulting point
272 * @x: scalar to multiply with @p
273 * @p: point to multiply with @x
274 * @y: scalar to multiply with @q
275 * @q: point to multiply with @y
276 * @curve: curve
277 *
278 * Returns result = x * p + x * q over the curve.
279 * This works faster than two multiplications and addition.
280 */
281 void ecc_point_mult_shamir(const struct ecc_point *result,
282 const u64 *x, const struct ecc_point *p,
283 const u64 *y, const struct ecc_point *q,
284 const struct ecc_curve *curve);
285 #endif
286