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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Microchip / Atmel ECC (I2C) driver.
4 *
5 * Copyright (c) 2017, Microchip Technology Inc.
6 * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
7 */
8
9#include <linux/delay.h>
10#include <linux/device.h>
11#include <linux/err.h>
12#include <linux/errno.h>
13#include <linux/i2c.h>
14#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/of_device.h>
18#include <linux/scatterlist.h>
19#include <linux/slab.h>
20#include <linux/workqueue.h>
21#include <crypto/internal/kpp.h>
22#include <crypto/ecdh.h>
23#include <crypto/kpp.h>
24#include "atmel-i2c.h"
25
26static struct atmel_ecc_driver_data driver_data;
27
28/**
29 * atmel_ecdh_ctx - transformation context
30 * @client : pointer to i2c client device
31 * @fallback : used for unsupported curves or when user wants to use its own
32 * private key.
33 * @public_key : generated when calling set_secret(). It's the responsibility
34 * of the user to not call set_secret() while
35 * generate_public_key() or compute_shared_secret() are in flight.
36 * @curve_id : elliptic curve id
37 * @n_sz : size in bytes of the n prime
38 * @do_fallback: true when the device doesn't support the curve or when the user
39 * wants to use its own private key.
40 */
41struct atmel_ecdh_ctx {
42 struct i2c_client *client;
43 struct crypto_kpp *fallback;
44 const u8 *public_key;
45 unsigned int curve_id;
46 size_t n_sz;
47 bool do_fallback;
48};
49
50static void atmel_ecdh_done(struct atmel_i2c_work_data *work_data, void *areq,
51 int status)
52{
53 struct kpp_request *req = areq;
54 struct atmel_ecdh_ctx *ctx = work_data->ctx;
55 struct atmel_i2c_cmd *cmd = &work_data->cmd;
56 size_t copied, n_sz;
57
58 if (status)
59 goto free_work_data;
60
61 /* might want less than we've got */
62 n_sz = min_t(size_t, ctx->n_sz, req->dst_len);
63
64 /* copy the shared secret */
65 copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, n_sz),
66 &cmd->data[RSP_DATA_IDX], n_sz);
67 if (copied != n_sz)
68 status = -EINVAL;
69
70 /* fall through */
71free_work_data:
72 kfree_sensitive(work_data);
73 kpp_request_complete(req, status);
74}
75
76static unsigned int atmel_ecdh_supported_curve(unsigned int curve_id)
77{
78 if (curve_id == ECC_CURVE_NIST_P256)
79 return ATMEL_ECC_NIST_P256_N_SIZE;
80
81 return 0;
82}
83
84/*
85 * A random private key is generated and stored in the device. The device
86 * returns the pair public key.
87 */
88static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
89 unsigned int len)
90{
91 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
92 struct atmel_i2c_cmd *cmd;
93 void *public_key;
94 struct ecdh params;
95 int ret = -ENOMEM;
96
97 /* free the old public key, if any */
98 kfree(ctx->public_key);
99 /* make sure you don't free the old public key twice */
100 ctx->public_key = NULL;
101
102 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) {
103 dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
104 return -EINVAL;
105 }
106
107 ctx->n_sz = atmel_ecdh_supported_curve(params.curve_id);
108 if (!ctx->n_sz || params.key_size) {
109 /* fallback to ecdh software implementation */
110 ctx->do_fallback = true;
111 return crypto_kpp_set_secret(ctx->fallback, buf, len);
112 }
113
114 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
115 if (!cmd)
116 return -ENOMEM;
117
118 /*
119 * The device only supports NIST P256 ECC keys. The public key size will
120 * always be the same. Use a macro for the key size to avoid unnecessary
121 * computations.
122 */
123 public_key = kmalloc(ATMEL_ECC_PUBKEY_SIZE, GFP_KERNEL);
124 if (!public_key)
125 goto free_cmd;
126
127 ctx->do_fallback = false;
128 ctx->curve_id = params.curve_id;
129
130 atmel_i2c_init_genkey_cmd(cmd, DATA_SLOT_2);
131
132 ret = atmel_i2c_send_receive(ctx->client, cmd);
133 if (ret)
134 goto free_public_key;
135
136 /* save the public key */
137 memcpy(public_key, &cmd->data[RSP_DATA_IDX], ATMEL_ECC_PUBKEY_SIZE);
138 ctx->public_key = public_key;
139
140 kfree(cmd);
141 return 0;
142
143free_public_key:
144 kfree(public_key);
145free_cmd:
146 kfree(cmd);
147 return ret;
148}
149
150static int atmel_ecdh_generate_public_key(struct kpp_request *req)
151{
152 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
153 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
154 size_t copied, nbytes;
155 int ret = 0;
156
157 if (ctx->do_fallback) {
158 kpp_request_set_tfm(req, ctx->fallback);
159 return crypto_kpp_generate_public_key(req);
160 }
161
162 if (!ctx->public_key)
163 return -EINVAL;
164
165 /* might want less than we've got */
166 nbytes = min_t(size_t, ATMEL_ECC_PUBKEY_SIZE, req->dst_len);
167
168 /* public key was saved at private key generation */
169 copied = sg_copy_from_buffer(req->dst,
170 sg_nents_for_len(req->dst, nbytes),
171 ctx->public_key, nbytes);
172 if (copied != nbytes)
173 ret = -EINVAL;
174
175 return ret;
176}
177
178static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
179{
180 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
181 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
182 struct atmel_i2c_work_data *work_data;
183 gfp_t gfp;
184 int ret;
185
186 if (ctx->do_fallback) {
187 kpp_request_set_tfm(req, ctx->fallback);
188 return crypto_kpp_compute_shared_secret(req);
189 }
190
191 /* must have exactly two points to be on the curve */
192 if (req->src_len != ATMEL_ECC_PUBKEY_SIZE)
193 return -EINVAL;
194
195 gfp = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ? GFP_KERNEL :
196 GFP_ATOMIC;
197
198 work_data = kmalloc(sizeof(*work_data), gfp);
199 if (!work_data)
200 return -ENOMEM;
201
202 work_data->ctx = ctx;
203 work_data->client = ctx->client;
204
205 ret = atmel_i2c_init_ecdh_cmd(&work_data->cmd, req->src);
206 if (ret)
207 goto free_work_data;
208
209 atmel_i2c_enqueue(work_data, atmel_ecdh_done, req);
210
211 return -EINPROGRESS;
212
213free_work_data:
214 kfree(work_data);
215 return ret;
216}
217
218static struct i2c_client *atmel_ecc_i2c_client_alloc(void)
219{
220 struct atmel_i2c_client_priv *i2c_priv, *min_i2c_priv = NULL;
221 struct i2c_client *client = ERR_PTR(-ENODEV);
222 int min_tfm_cnt = INT_MAX;
223 int tfm_cnt;
224
225 spin_lock(&driver_data.i2c_list_lock);
226
227 if (list_empty(&driver_data.i2c_client_list)) {
228 spin_unlock(&driver_data.i2c_list_lock);
229 return ERR_PTR(-ENODEV);
230 }
231
232 list_for_each_entry(i2c_priv, &driver_data.i2c_client_list,
233 i2c_client_list_node) {
234 tfm_cnt = atomic_read(&i2c_priv->tfm_count);
235 if (tfm_cnt < min_tfm_cnt) {
236 min_tfm_cnt = tfm_cnt;
237 min_i2c_priv = i2c_priv;
238 }
239 if (!min_tfm_cnt)
240 break;
241 }
242
243 if (min_i2c_priv) {
244 atomic_inc(&min_i2c_priv->tfm_count);
245 client = min_i2c_priv->client;
246 }
247
248 spin_unlock(&driver_data.i2c_list_lock);
249
250 return client;
251}
252
253static void atmel_ecc_i2c_client_free(struct i2c_client *client)
254{
255 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
256
257 atomic_dec(&i2c_priv->tfm_count);
258}
259
260static int atmel_ecdh_init_tfm(struct crypto_kpp *tfm)
261{
262 const char *alg = kpp_alg_name(tfm);
263 struct crypto_kpp *fallback;
264 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
265
266 ctx->client = atmel_ecc_i2c_client_alloc();
267 if (IS_ERR(ctx->client)) {
268 pr_err("tfm - i2c_client binding failed\n");
269 return PTR_ERR(ctx->client);
270 }
271
272 fallback = crypto_alloc_kpp(alg, 0, CRYPTO_ALG_NEED_FALLBACK);
273 if (IS_ERR(fallback)) {
274 dev_err(&ctx->client->dev, "Failed to allocate transformation for '%s': %ld\n",
275 alg, PTR_ERR(fallback));
276 return PTR_ERR(fallback);
277 }
278
279 crypto_kpp_set_flags(fallback, crypto_kpp_get_flags(tfm));
280 ctx->fallback = fallback;
281
282 return 0;
283}
284
285static void atmel_ecdh_exit_tfm(struct crypto_kpp *tfm)
286{
287 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
288
289 kfree(ctx->public_key);
290 crypto_free_kpp(ctx->fallback);
291 atmel_ecc_i2c_client_free(ctx->client);
292}
293
294static unsigned int atmel_ecdh_max_size(struct crypto_kpp *tfm)
295{
296 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
297
298 if (ctx->fallback)
299 return crypto_kpp_maxsize(ctx->fallback);
300
301 /*
302 * The device only supports NIST P256 ECC keys. The public key size will
303 * always be the same. Use a macro for the key size to avoid unnecessary
304 * computations.
305 */
306 return ATMEL_ECC_PUBKEY_SIZE;
307}
308
309static struct kpp_alg atmel_ecdh = {
310 .set_secret = atmel_ecdh_set_secret,
311 .generate_public_key = atmel_ecdh_generate_public_key,
312 .compute_shared_secret = atmel_ecdh_compute_shared_secret,
313 .init = atmel_ecdh_init_tfm,
314 .exit = atmel_ecdh_exit_tfm,
315 .max_size = atmel_ecdh_max_size,
316 .base = {
317 .cra_flags = CRYPTO_ALG_NEED_FALLBACK,
318 .cra_name = "ecdh",
319 .cra_driver_name = "atmel-ecdh",
320 .cra_priority = ATMEL_ECC_PRIORITY,
321 .cra_module = THIS_MODULE,
322 .cra_ctxsize = sizeof(struct atmel_ecdh_ctx),
323 },
324};
325
326static int atmel_ecc_probe(struct i2c_client *client,
327 const struct i2c_device_id *id)
328{
329 struct atmel_i2c_client_priv *i2c_priv;
330 int ret;
331
332 ret = atmel_i2c_probe(client, id);
333 if (ret)
334 return ret;
335
336 i2c_priv = i2c_get_clientdata(client);
337
338 spin_lock(&driver_data.i2c_list_lock);
339 list_add_tail(&i2c_priv->i2c_client_list_node,
340 &driver_data.i2c_client_list);
341 spin_unlock(&driver_data.i2c_list_lock);
342
343 ret = crypto_register_kpp(&atmel_ecdh);
344 if (ret) {
345 spin_lock(&driver_data.i2c_list_lock);
346 list_del(&i2c_priv->i2c_client_list_node);
347 spin_unlock(&driver_data.i2c_list_lock);
348
349 dev_err(&client->dev, "%s alg registration failed\n",
350 atmel_ecdh.base.cra_driver_name);
351 } else {
352 dev_info(&client->dev, "atmel ecc algorithms registered in /proc/crypto\n");
353 }
354
355 return ret;
356}
357
358static int atmel_ecc_remove(struct i2c_client *client)
359{
360 struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
361
362 /* Return EBUSY if i2c client already allocated. */
363 if (atomic_read(&i2c_priv->tfm_count)) {
364 dev_err(&client->dev, "Device is busy\n");
365 return -EBUSY;
366 }
367
368 crypto_unregister_kpp(&atmel_ecdh);
369
370 spin_lock(&driver_data.i2c_list_lock);
371 list_del(&i2c_priv->i2c_client_list_node);
372 spin_unlock(&driver_data.i2c_list_lock);
373
374 return 0;
375}
376
377#ifdef CONFIG_OF
378static const struct of_device_id atmel_ecc_dt_ids[] = {
379 {
380 .compatible = "atmel,atecc508a",
381 }, {
382 /* sentinel */
383 }
384};
385MODULE_DEVICE_TABLE(of, atmel_ecc_dt_ids);
386#endif
387
388static const struct i2c_device_id atmel_ecc_id[] = {
389 { "atecc508a", 0 },
390 { }
391};
392MODULE_DEVICE_TABLE(i2c, atmel_ecc_id);
393
394static struct i2c_driver atmel_ecc_driver = {
395 .driver = {
396 .name = "atmel-ecc",
397 .of_match_table = of_match_ptr(atmel_ecc_dt_ids),
398 },
399 .probe = atmel_ecc_probe,
400 .remove = atmel_ecc_remove,
401 .id_table = atmel_ecc_id,
402};
403
404static int __init atmel_ecc_init(void)
405{
406 spin_lock_init(&driver_data.i2c_list_lock);
407 INIT_LIST_HEAD(&driver_data.i2c_client_list);
408 return i2c_add_driver(&atmel_ecc_driver);
409}
410
411static void __exit atmel_ecc_exit(void)
412{
413 flush_scheduled_work();
414 i2c_del_driver(&atmel_ecc_driver);
415}
416
417module_init(atmel_ecc_init);
418module_exit(atmel_ecc_exit);
419
420MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
421MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
422MODULE_LICENSE("GPL v2");
1/*
2 * Microchip / Atmel ECC (I2C) driver.
3 *
4 * Copyright (c) 2017, Microchip Technology Inc.
5 * Author: Tudor Ambarus <tudor.ambarus@microchip.com>
6 *
7 * This software is licensed under the terms of the GNU General Public
8 * License version 2, as published by the Free Software Foundation, and
9 * may be copied, distributed, and modified under those terms.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 */
17
18#include <linux/bitrev.h>
19#include <linux/crc16.h>
20#include <linux/delay.h>
21#include <linux/device.h>
22#include <linux/err.h>
23#include <linux/errno.h>
24#include <linux/i2c.h>
25#include <linux/init.h>
26#include <linux/kernel.h>
27#include <linux/module.h>
28#include <linux/of_device.h>
29#include <linux/scatterlist.h>
30#include <linux/slab.h>
31#include <linux/workqueue.h>
32#include <crypto/internal/kpp.h>
33#include <crypto/ecdh.h>
34#include <crypto/kpp.h>
35#include "atmel-ecc.h"
36
37/* Used for binding tfm objects to i2c clients. */
38struct atmel_ecc_driver_data {
39 struct list_head i2c_client_list;
40 spinlock_t i2c_list_lock;
41} ____cacheline_aligned;
42
43static struct atmel_ecc_driver_data driver_data;
44
45/**
46 * atmel_ecc_i2c_client_priv - i2c_client private data
47 * @client : pointer to i2c client device
48 * @i2c_client_list_node: part of i2c_client_list
49 * @lock : lock for sending i2c commands
50 * @wake_token : wake token array of zeros
51 * @wake_token_sz : size in bytes of the wake_token
52 * @tfm_count : number of active crypto transformations on i2c client
53 *
54 * Reads and writes from/to the i2c client are sequential. The first byte
55 * transmitted to the device is treated as the byte size. Any attempt to send
56 * more than this number of bytes will cause the device to not ACK those bytes.
57 * After the host writes a single command byte to the input buffer, reads are
58 * prohibited until after the device completes command execution. Use a mutex
59 * when sending i2c commands.
60 */
61struct atmel_ecc_i2c_client_priv {
62 struct i2c_client *client;
63 struct list_head i2c_client_list_node;
64 struct mutex lock;
65 u8 wake_token[WAKE_TOKEN_MAX_SIZE];
66 size_t wake_token_sz;
67 atomic_t tfm_count ____cacheline_aligned;
68};
69
70/**
71 * atmel_ecdh_ctx - transformation context
72 * @client : pointer to i2c client device
73 * @fallback : used for unsupported curves or when user wants to use its own
74 * private key.
75 * @public_key : generated when calling set_secret(). It's the responsibility
76 * of the user to not call set_secret() while
77 * generate_public_key() or compute_shared_secret() are in flight.
78 * @curve_id : elliptic curve id
79 * @n_sz : size in bytes of the n prime
80 * @do_fallback: true when the device doesn't support the curve or when the user
81 * wants to use its own private key.
82 */
83struct atmel_ecdh_ctx {
84 struct i2c_client *client;
85 struct crypto_kpp *fallback;
86 const u8 *public_key;
87 unsigned int curve_id;
88 size_t n_sz;
89 bool do_fallback;
90};
91
92/**
93 * atmel_ecc_work_data - data structure representing the work
94 * @ctx : transformation context.
95 * @cbk : pointer to a callback function to be invoked upon completion of this
96 * request. This has the form:
97 * callback(struct atmel_ecc_work_data *work_data, void *areq, u8 status)
98 * where:
99 * @work_data: data structure representing the work
100 * @areq : optional pointer to an argument passed with the original
101 * request.
102 * @status : status returned from the i2c client device or i2c error.
103 * @areq: optional pointer to a user argument for use at callback time.
104 * @work: describes the task to be executed.
105 * @cmd : structure used for communicating with the device.
106 */
107struct atmel_ecc_work_data {
108 struct atmel_ecdh_ctx *ctx;
109 void (*cbk)(struct atmel_ecc_work_data *work_data, void *areq,
110 int status);
111 void *areq;
112 struct work_struct work;
113 struct atmel_ecc_cmd cmd;
114};
115
116static u16 atmel_ecc_crc16(u16 crc, const u8 *buffer, size_t len)
117{
118 return cpu_to_le16(bitrev16(crc16(crc, buffer, len)));
119}
120
121/**
122 * atmel_ecc_checksum() - Generate 16-bit CRC as required by ATMEL ECC.
123 * CRC16 verification of the count, opcode, param1, param2 and data bytes.
124 * The checksum is saved in little-endian format in the least significant
125 * two bytes of the command. CRC polynomial is 0x8005 and the initial register
126 * value should be zero.
127 *
128 * @cmd : structure used for communicating with the device.
129 */
130static void atmel_ecc_checksum(struct atmel_ecc_cmd *cmd)
131{
132 u8 *data = &cmd->count;
133 size_t len = cmd->count - CRC_SIZE;
134 u16 *crc16 = (u16 *)(data + len);
135
136 *crc16 = atmel_ecc_crc16(0, data, len);
137}
138
139static void atmel_ecc_init_read_cmd(struct atmel_ecc_cmd *cmd)
140{
141 cmd->word_addr = COMMAND;
142 cmd->opcode = OPCODE_READ;
143 /*
144 * Read the word from Configuration zone that contains the lock bytes
145 * (UserExtra, Selector, LockValue, LockConfig).
146 */
147 cmd->param1 = CONFIG_ZONE;
148 cmd->param2 = DEVICE_LOCK_ADDR;
149 cmd->count = READ_COUNT;
150
151 atmel_ecc_checksum(cmd);
152
153 cmd->msecs = MAX_EXEC_TIME_READ;
154 cmd->rxsize = READ_RSP_SIZE;
155}
156
157static void atmel_ecc_init_genkey_cmd(struct atmel_ecc_cmd *cmd, u16 keyid)
158{
159 cmd->word_addr = COMMAND;
160 cmd->count = GENKEY_COUNT;
161 cmd->opcode = OPCODE_GENKEY;
162 cmd->param1 = GENKEY_MODE_PRIVATE;
163 /* a random private key will be generated and stored in slot keyID */
164 cmd->param2 = cpu_to_le16(keyid);
165
166 atmel_ecc_checksum(cmd);
167
168 cmd->msecs = MAX_EXEC_TIME_GENKEY;
169 cmd->rxsize = GENKEY_RSP_SIZE;
170}
171
172static int atmel_ecc_init_ecdh_cmd(struct atmel_ecc_cmd *cmd,
173 struct scatterlist *pubkey)
174{
175 size_t copied;
176
177 cmd->word_addr = COMMAND;
178 cmd->count = ECDH_COUNT;
179 cmd->opcode = OPCODE_ECDH;
180 cmd->param1 = ECDH_PREFIX_MODE;
181 /* private key slot */
182 cmd->param2 = cpu_to_le16(DATA_SLOT_2);
183
184 /*
185 * The device only supports NIST P256 ECC keys. The public key size will
186 * always be the same. Use a macro for the key size to avoid unnecessary
187 * computations.
188 */
189 copied = sg_copy_to_buffer(pubkey, 1, cmd->data, ATMEL_ECC_PUBKEY_SIZE);
190 if (copied != ATMEL_ECC_PUBKEY_SIZE)
191 return -EINVAL;
192
193 atmel_ecc_checksum(cmd);
194
195 cmd->msecs = MAX_EXEC_TIME_ECDH;
196 cmd->rxsize = ECDH_RSP_SIZE;
197
198 return 0;
199}
200
201/*
202 * After wake and after execution of a command, there will be error, status, or
203 * result bytes in the device's output register that can be retrieved by the
204 * system. When the length of that group is four bytes, the codes returned are
205 * detailed in error_list.
206 */
207static int atmel_ecc_status(struct device *dev, u8 *status)
208{
209 size_t err_list_len = ARRAY_SIZE(error_list);
210 int i;
211 u8 err_id = status[1];
212
213 if (*status != STATUS_SIZE)
214 return 0;
215
216 if (err_id == STATUS_WAKE_SUCCESSFUL || err_id == STATUS_NOERR)
217 return 0;
218
219 for (i = 0; i < err_list_len; i++)
220 if (error_list[i].value == err_id)
221 break;
222
223 /* if err_id is not in the error_list then ignore it */
224 if (i != err_list_len) {
225 dev_err(dev, "%02x: %s:\n", err_id, error_list[i].error_text);
226 return err_id;
227 }
228
229 return 0;
230}
231
232static int atmel_ecc_wakeup(struct i2c_client *client)
233{
234 struct atmel_ecc_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
235 u8 status[STATUS_RSP_SIZE];
236 int ret;
237
238 /*
239 * The device ignores any levels or transitions on the SCL pin when the
240 * device is idle, asleep or during waking up. Don't check for error
241 * when waking up the device.
242 */
243 i2c_master_send(client, i2c_priv->wake_token, i2c_priv->wake_token_sz);
244
245 /*
246 * Wait to wake the device. Typical execution times for ecdh and genkey
247 * are around tens of milliseconds. Delta is chosen to 50 microseconds.
248 */
249 usleep_range(TWHI_MIN, TWHI_MAX);
250
251 ret = i2c_master_recv(client, status, STATUS_SIZE);
252 if (ret < 0)
253 return ret;
254
255 return atmel_ecc_status(&client->dev, status);
256}
257
258static int atmel_ecc_sleep(struct i2c_client *client)
259{
260 u8 sleep = SLEEP_TOKEN;
261
262 return i2c_master_send(client, &sleep, 1);
263}
264
265static void atmel_ecdh_done(struct atmel_ecc_work_data *work_data, void *areq,
266 int status)
267{
268 struct kpp_request *req = areq;
269 struct atmel_ecdh_ctx *ctx = work_data->ctx;
270 struct atmel_ecc_cmd *cmd = &work_data->cmd;
271 size_t copied;
272 size_t n_sz = ctx->n_sz;
273
274 if (status)
275 goto free_work_data;
276
277 /* copy the shared secret */
278 copied = sg_copy_from_buffer(req->dst, 1, &cmd->data[RSP_DATA_IDX],
279 n_sz);
280 if (copied != n_sz)
281 status = -EINVAL;
282
283 /* fall through */
284free_work_data:
285 kzfree(work_data);
286 kpp_request_complete(req, status);
287}
288
289/*
290 * atmel_ecc_send_receive() - send a command to the device and receive its
291 * response.
292 * @client: i2c client device
293 * @cmd : structure used to communicate with the device
294 *
295 * After the device receives a Wake token, a watchdog counter starts within the
296 * device. After the watchdog timer expires, the device enters sleep mode
297 * regardless of whether some I/O transmission or command execution is in
298 * progress. If a command is attempted when insufficient time remains prior to
299 * watchdog timer execution, the device will return the watchdog timeout error
300 * code without attempting to execute the command. There is no way to reset the
301 * counter other than to put the device into sleep or idle mode and then
302 * wake it up again.
303 */
304static int atmel_ecc_send_receive(struct i2c_client *client,
305 struct atmel_ecc_cmd *cmd)
306{
307 struct atmel_ecc_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
308 int ret;
309
310 mutex_lock(&i2c_priv->lock);
311
312 ret = atmel_ecc_wakeup(client);
313 if (ret)
314 goto err;
315
316 /* send the command */
317 ret = i2c_master_send(client, (u8 *)cmd, cmd->count + WORD_ADDR_SIZE);
318 if (ret < 0)
319 goto err;
320
321 /* delay the appropriate amount of time for command to execute */
322 msleep(cmd->msecs);
323
324 /* receive the response */
325 ret = i2c_master_recv(client, cmd->data, cmd->rxsize);
326 if (ret < 0)
327 goto err;
328
329 /* put the device into low-power mode */
330 ret = atmel_ecc_sleep(client);
331 if (ret < 0)
332 goto err;
333
334 mutex_unlock(&i2c_priv->lock);
335 return atmel_ecc_status(&client->dev, cmd->data);
336err:
337 mutex_unlock(&i2c_priv->lock);
338 return ret;
339}
340
341static void atmel_ecc_work_handler(struct work_struct *work)
342{
343 struct atmel_ecc_work_data *work_data =
344 container_of(work, struct atmel_ecc_work_data, work);
345 struct atmel_ecc_cmd *cmd = &work_data->cmd;
346 struct i2c_client *client = work_data->ctx->client;
347 int status;
348
349 status = atmel_ecc_send_receive(client, cmd);
350 work_data->cbk(work_data, work_data->areq, status);
351}
352
353static void atmel_ecc_enqueue(struct atmel_ecc_work_data *work_data,
354 void (*cbk)(struct atmel_ecc_work_data *work_data,
355 void *areq, int status),
356 void *areq)
357{
358 work_data->cbk = (void *)cbk;
359 work_data->areq = areq;
360
361 INIT_WORK(&work_data->work, atmel_ecc_work_handler);
362 schedule_work(&work_data->work);
363}
364
365static unsigned int atmel_ecdh_supported_curve(unsigned int curve_id)
366{
367 if (curve_id == ECC_CURVE_NIST_P256)
368 return ATMEL_ECC_NIST_P256_N_SIZE;
369
370 return 0;
371}
372
373/*
374 * A random private key is generated and stored in the device. The device
375 * returns the pair public key.
376 */
377static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
378 unsigned int len)
379{
380 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
381 struct atmel_ecc_cmd *cmd;
382 void *public_key;
383 struct ecdh params;
384 int ret = -ENOMEM;
385
386 /* free the old public key, if any */
387 kfree(ctx->public_key);
388 /* make sure you don't free the old public key twice */
389 ctx->public_key = NULL;
390
391 if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) {
392 dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
393 return -EINVAL;
394 }
395
396 ctx->n_sz = atmel_ecdh_supported_curve(params.curve_id);
397 if (!ctx->n_sz || params.key_size) {
398 /* fallback to ecdh software implementation */
399 ctx->do_fallback = true;
400 return crypto_kpp_set_secret(ctx->fallback, buf, len);
401 }
402
403 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
404 if (!cmd)
405 return -ENOMEM;
406
407 /*
408 * The device only supports NIST P256 ECC keys. The public key size will
409 * always be the same. Use a macro for the key size to avoid unnecessary
410 * computations.
411 */
412 public_key = kmalloc(ATMEL_ECC_PUBKEY_SIZE, GFP_KERNEL);
413 if (!public_key)
414 goto free_cmd;
415
416 ctx->do_fallback = false;
417 ctx->curve_id = params.curve_id;
418
419 atmel_ecc_init_genkey_cmd(cmd, DATA_SLOT_2);
420
421 ret = atmel_ecc_send_receive(ctx->client, cmd);
422 if (ret)
423 goto free_public_key;
424
425 /* save the public key */
426 memcpy(public_key, &cmd->data[RSP_DATA_IDX], ATMEL_ECC_PUBKEY_SIZE);
427 ctx->public_key = public_key;
428
429 kfree(cmd);
430 return 0;
431
432free_public_key:
433 kfree(public_key);
434free_cmd:
435 kfree(cmd);
436 return ret;
437}
438
439static int atmel_ecdh_generate_public_key(struct kpp_request *req)
440{
441 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
442 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
443 size_t copied;
444 int ret = 0;
445
446 if (ctx->do_fallback) {
447 kpp_request_set_tfm(req, ctx->fallback);
448 return crypto_kpp_generate_public_key(req);
449 }
450
451 /* public key was saved at private key generation */
452 copied = sg_copy_from_buffer(req->dst, 1, ctx->public_key,
453 ATMEL_ECC_PUBKEY_SIZE);
454 if (copied != ATMEL_ECC_PUBKEY_SIZE)
455 ret = -EINVAL;
456
457 return ret;
458}
459
460static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
461{
462 struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
463 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
464 struct atmel_ecc_work_data *work_data;
465 gfp_t gfp;
466 int ret;
467
468 if (ctx->do_fallback) {
469 kpp_request_set_tfm(req, ctx->fallback);
470 return crypto_kpp_compute_shared_secret(req);
471 }
472
473 gfp = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ? GFP_KERNEL :
474 GFP_ATOMIC;
475
476 work_data = kmalloc(sizeof(*work_data), gfp);
477 if (!work_data)
478 return -ENOMEM;
479
480 work_data->ctx = ctx;
481
482 ret = atmel_ecc_init_ecdh_cmd(&work_data->cmd, req->src);
483 if (ret)
484 goto free_work_data;
485
486 atmel_ecc_enqueue(work_data, atmel_ecdh_done, req);
487
488 return -EINPROGRESS;
489
490free_work_data:
491 kfree(work_data);
492 return ret;
493}
494
495static struct i2c_client *atmel_ecc_i2c_client_alloc(void)
496{
497 struct atmel_ecc_i2c_client_priv *i2c_priv, *min_i2c_priv = NULL;
498 struct i2c_client *client = ERR_PTR(-ENODEV);
499 int min_tfm_cnt = INT_MAX;
500 int tfm_cnt;
501
502 spin_lock(&driver_data.i2c_list_lock);
503
504 if (list_empty(&driver_data.i2c_client_list)) {
505 spin_unlock(&driver_data.i2c_list_lock);
506 return ERR_PTR(-ENODEV);
507 }
508
509 list_for_each_entry(i2c_priv, &driver_data.i2c_client_list,
510 i2c_client_list_node) {
511 tfm_cnt = atomic_read(&i2c_priv->tfm_count);
512 if (tfm_cnt < min_tfm_cnt) {
513 min_tfm_cnt = tfm_cnt;
514 min_i2c_priv = i2c_priv;
515 }
516 if (!min_tfm_cnt)
517 break;
518 }
519
520 if (min_i2c_priv) {
521 atomic_inc(&min_i2c_priv->tfm_count);
522 client = min_i2c_priv->client;
523 }
524
525 spin_unlock(&driver_data.i2c_list_lock);
526
527 return client;
528}
529
530static void atmel_ecc_i2c_client_free(struct i2c_client *client)
531{
532 struct atmel_ecc_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
533
534 atomic_dec(&i2c_priv->tfm_count);
535}
536
537static int atmel_ecdh_init_tfm(struct crypto_kpp *tfm)
538{
539 const char *alg = kpp_alg_name(tfm);
540 struct crypto_kpp *fallback;
541 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
542
543 ctx->client = atmel_ecc_i2c_client_alloc();
544 if (IS_ERR(ctx->client)) {
545 pr_err("tfm - i2c_client binding failed\n");
546 return PTR_ERR(ctx->client);
547 }
548
549 fallback = crypto_alloc_kpp(alg, 0, CRYPTO_ALG_NEED_FALLBACK);
550 if (IS_ERR(fallback)) {
551 dev_err(&ctx->client->dev, "Failed to allocate transformation for '%s': %ld\n",
552 alg, PTR_ERR(fallback));
553 return PTR_ERR(fallback);
554 }
555
556 crypto_kpp_set_flags(fallback, crypto_kpp_get_flags(tfm));
557
558 dev_info(&ctx->client->dev, "Using '%s' as fallback implementation.\n",
559 crypto_tfm_alg_driver_name(crypto_kpp_tfm(fallback)));
560
561 ctx->fallback = fallback;
562
563 return 0;
564}
565
566static void atmel_ecdh_exit_tfm(struct crypto_kpp *tfm)
567{
568 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
569
570 kfree(ctx->public_key);
571 crypto_free_kpp(ctx->fallback);
572 atmel_ecc_i2c_client_free(ctx->client);
573}
574
575static unsigned int atmel_ecdh_max_size(struct crypto_kpp *tfm)
576{
577 struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
578
579 if (ctx->fallback)
580 return crypto_kpp_maxsize(ctx->fallback);
581
582 /*
583 * The device only supports NIST P256 ECC keys. The public key size will
584 * always be the same. Use a macro for the key size to avoid unnecessary
585 * computations.
586 */
587 return ATMEL_ECC_PUBKEY_SIZE;
588}
589
590static struct kpp_alg atmel_ecdh = {
591 .set_secret = atmel_ecdh_set_secret,
592 .generate_public_key = atmel_ecdh_generate_public_key,
593 .compute_shared_secret = atmel_ecdh_compute_shared_secret,
594 .init = atmel_ecdh_init_tfm,
595 .exit = atmel_ecdh_exit_tfm,
596 .max_size = atmel_ecdh_max_size,
597 .base = {
598 .cra_flags = CRYPTO_ALG_NEED_FALLBACK,
599 .cra_name = "ecdh",
600 .cra_driver_name = "atmel-ecdh",
601 .cra_priority = ATMEL_ECC_PRIORITY,
602 .cra_module = THIS_MODULE,
603 .cra_ctxsize = sizeof(struct atmel_ecdh_ctx),
604 },
605};
606
607static inline size_t atmel_ecc_wake_token_sz(u32 bus_clk_rate)
608{
609 u32 no_of_bits = DIV_ROUND_UP(TWLO_USEC * bus_clk_rate, USEC_PER_SEC);
610
611 /* return the size of the wake_token in bytes */
612 return DIV_ROUND_UP(no_of_bits, 8);
613}
614
615static int device_sanity_check(struct i2c_client *client)
616{
617 struct atmel_ecc_cmd *cmd;
618 int ret;
619
620 cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
621 if (!cmd)
622 return -ENOMEM;
623
624 atmel_ecc_init_read_cmd(cmd);
625
626 ret = atmel_ecc_send_receive(client, cmd);
627 if (ret)
628 goto free_cmd;
629
630 /*
631 * It is vital that the Configuration, Data and OTP zones be locked
632 * prior to release into the field of the system containing the device.
633 * Failure to lock these zones may permit modification of any secret
634 * keys and may lead to other security problems.
635 */
636 if (cmd->data[LOCK_CONFIG_IDX] || cmd->data[LOCK_VALUE_IDX]) {
637 dev_err(&client->dev, "Configuration or Data and OTP zones are unlocked!\n");
638 ret = -ENOTSUPP;
639 }
640
641 /* fall through */
642free_cmd:
643 kfree(cmd);
644 return ret;
645}
646
647static int atmel_ecc_probe(struct i2c_client *client,
648 const struct i2c_device_id *id)
649{
650 struct atmel_ecc_i2c_client_priv *i2c_priv;
651 struct device *dev = &client->dev;
652 int ret;
653 u32 bus_clk_rate;
654
655 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
656 dev_err(dev, "I2C_FUNC_I2C not supported\n");
657 return -ENODEV;
658 }
659
660 ret = of_property_read_u32(client->adapter->dev.of_node,
661 "clock-frequency", &bus_clk_rate);
662 if (ret) {
663 dev_err(dev, "of: failed to read clock-frequency property\n");
664 return ret;
665 }
666
667 if (bus_clk_rate > 1000000L) {
668 dev_err(dev, "%d exceeds maximum supported clock frequency (1MHz)\n",
669 bus_clk_rate);
670 return -EINVAL;
671 }
672
673 i2c_priv = devm_kmalloc(dev, sizeof(*i2c_priv), GFP_KERNEL);
674 if (!i2c_priv)
675 return -ENOMEM;
676
677 i2c_priv->client = client;
678 mutex_init(&i2c_priv->lock);
679
680 /*
681 * WAKE_TOKEN_MAX_SIZE was calculated for the maximum bus_clk_rate -
682 * 1MHz. The previous bus_clk_rate check ensures us that wake_token_sz
683 * will always be smaller than or equal to WAKE_TOKEN_MAX_SIZE.
684 */
685 i2c_priv->wake_token_sz = atmel_ecc_wake_token_sz(bus_clk_rate);
686
687 memset(i2c_priv->wake_token, 0, sizeof(i2c_priv->wake_token));
688
689 atomic_set(&i2c_priv->tfm_count, 0);
690
691 i2c_set_clientdata(client, i2c_priv);
692
693 ret = device_sanity_check(client);
694 if (ret)
695 return ret;
696
697 spin_lock(&driver_data.i2c_list_lock);
698 list_add_tail(&i2c_priv->i2c_client_list_node,
699 &driver_data.i2c_client_list);
700 spin_unlock(&driver_data.i2c_list_lock);
701
702 ret = crypto_register_kpp(&atmel_ecdh);
703 if (ret) {
704 spin_lock(&driver_data.i2c_list_lock);
705 list_del(&i2c_priv->i2c_client_list_node);
706 spin_unlock(&driver_data.i2c_list_lock);
707
708 dev_err(dev, "%s alg registration failed\n",
709 atmel_ecdh.base.cra_driver_name);
710 } else {
711 dev_info(dev, "atmel ecc algorithms registered in /proc/crypto\n");
712 }
713
714 return ret;
715}
716
717static int atmel_ecc_remove(struct i2c_client *client)
718{
719 struct atmel_ecc_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
720
721 /* Return EBUSY if i2c client already allocated. */
722 if (atomic_read(&i2c_priv->tfm_count)) {
723 dev_err(&client->dev, "Device is busy\n");
724 return -EBUSY;
725 }
726
727 crypto_unregister_kpp(&atmel_ecdh);
728
729 spin_lock(&driver_data.i2c_list_lock);
730 list_del(&i2c_priv->i2c_client_list_node);
731 spin_unlock(&driver_data.i2c_list_lock);
732
733 return 0;
734}
735
736#ifdef CONFIG_OF
737static const struct of_device_id atmel_ecc_dt_ids[] = {
738 {
739 .compatible = "atmel,atecc508a",
740 }, {
741 /* sentinel */
742 }
743};
744MODULE_DEVICE_TABLE(of, atmel_ecc_dt_ids);
745#endif
746
747static const struct i2c_device_id atmel_ecc_id[] = {
748 { "atecc508a", 0 },
749 { }
750};
751MODULE_DEVICE_TABLE(i2c, atmel_ecc_id);
752
753static struct i2c_driver atmel_ecc_driver = {
754 .driver = {
755 .name = "atmel-ecc",
756 .of_match_table = of_match_ptr(atmel_ecc_dt_ids),
757 },
758 .probe = atmel_ecc_probe,
759 .remove = atmel_ecc_remove,
760 .id_table = atmel_ecc_id,
761};
762
763static int __init atmel_ecc_init(void)
764{
765 spin_lock_init(&driver_data.i2c_list_lock);
766 INIT_LIST_HEAD(&driver_data.i2c_client_list);
767 return i2c_add_driver(&atmel_ecc_driver);
768}
769
770static void __exit atmel_ecc_exit(void)
771{
772 flush_scheduled_work();
773 i2c_del_driver(&atmel_ecc_driver);
774}
775
776module_init(atmel_ecc_init);
777module_exit(atmel_ecc_exit);
778
779MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
780MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
781MODULE_LICENSE("GPL v2");