// SPDX-License-Identifier: GPL-2.0
/*
* Microchip / Atmel ECC (I2C) driver.
*
* Copyright (c) 2017, Microchip Technology Inc.
* Author: Tudor Ambarus <tudor.ambarus@microchip.com>
*/
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <crypto/internal/kpp.h>
#include <crypto/ecdh.h>
#include <crypto/kpp.h>
#include "atmel-i2c.h"
static struct atmel_ecc_driver_data driver_data;
/**
* struct atmel_ecdh_ctx - transformation context
* @client : pointer to i2c client device
* @fallback : used for unsupported curves or when user wants to use its own
* private key.
* @public_key : generated when calling set_secret(). It's the responsibility
* of the user to not call set_secret() while
* generate_public_key() or compute_shared_secret() are in flight.
* @curve_id : elliptic curve id
* @do_fallback: true when the device doesn't support the curve or when the user
* wants to use its own private key.
*/
struct atmel_ecdh_ctx {
struct i2c_client *client;
struct crypto_kpp *fallback;
const u8 *public_key;
unsigned int curve_id;
bool do_fallback;
};
static void atmel_ecdh_done(struct atmel_i2c_work_data *work_data, void *areq,
int status)
{
struct kpp_request *req = areq;
struct atmel_i2c_cmd *cmd = &work_data->cmd;
size_t copied, n_sz;
if (status)
goto free_work_data;
/* might want less than we've got */
n_sz = min_t(size_t, ATMEL_ECC_NIST_P256_N_SIZE, req->dst_len);
/* copy the shared secret */
copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, n_sz),
&cmd->data[RSP_DATA_IDX], n_sz);
if (copied != n_sz)
status = -EINVAL;
/* fall through */
free_work_data:
kfree_sensitive(work_data);
kpp_request_complete(req, status);
}
/*
* A random private key is generated and stored in the device. The device
* returns the pair public key.
*/
static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
unsigned int len)
{
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
struct atmel_i2c_cmd *cmd;
void *public_key;
struct ecdh params;
int ret = -ENOMEM;
/* free the old public key, if any */
kfree(ctx->public_key);
/* make sure you don't free the old public key twice */
ctx->public_key = NULL;
if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) {
dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
return -EINVAL;
}
if (params.key_size) {
/* fallback to ecdh software implementation */
ctx->do_fallback = true;
return crypto_kpp_set_secret(ctx->fallback, buf, len);
}
cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
if (!cmd)
return -ENOMEM;
/*
* The device only supports NIST P256 ECC keys. The public key size will
* always be the same. Use a macro for the key size to avoid unnecessary
* computations.
*/
public_key = kmalloc(ATMEL_ECC_PUBKEY_SIZE, GFP_KERNEL);
if (!public_key)
goto free_cmd;
ctx->do_fallback = false;
atmel_i2c_init_genkey_cmd(cmd, DATA_SLOT_2);
ret = atmel_i2c_send_receive(ctx->client, cmd);
if (ret)
goto free_public_key;
/* save the public key */
memcpy(public_key, &cmd->data[RSP_DATA_IDX], ATMEL_ECC_PUBKEY_SIZE);
ctx->public_key = public_key;
kfree(cmd);
return 0;
free_public_key:
kfree(public_key);
free_cmd:
kfree(cmd);
return ret;
}
static int atmel_ecdh_generate_public_key(struct kpp_request *req)
{
struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
size_t copied, nbytes;
int ret = 0;
if (ctx->do_fallback) {
kpp_request_set_tfm(req, ctx->fallback);
return crypto_kpp_generate_public_key(req);
}
if (!ctx->public_key)
return -EINVAL;
/* might want less than we've got */
nbytes = min_t(size_t, ATMEL_ECC_PUBKEY_SIZE, req->dst_len);
/* public key was saved at private key generation */
copied = sg_copy_from_buffer(req->dst,
sg_nents_for_len(req->dst, nbytes),
ctx->public_key, nbytes);
if (copied != nbytes)
ret = -EINVAL;
return ret;
}
static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
{
struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
struct atmel_i2c_work_data *work_data;
gfp_t gfp;
int ret;
if (ctx->do_fallback) {
kpp_request_set_tfm(req, ctx->fallback);
return crypto_kpp_compute_shared_secret(req);
}
/* must have exactly two points to be on the curve */
if (req->src_len != ATMEL_ECC_PUBKEY_SIZE)
return -EINVAL;
gfp = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ? GFP_KERNEL :
GFP_ATOMIC;
work_data = kmalloc(sizeof(*work_data), gfp);
if (!work_data)
return -ENOMEM;
work_data->ctx = ctx;
work_data->client = ctx->client;
ret = atmel_i2c_init_ecdh_cmd(&work_data->cmd, req->src);
if (ret)
goto free_work_data;
atmel_i2c_enqueue(work_data, atmel_ecdh_done, req);
return -EINPROGRESS;
free_work_data:
kfree(work_data);
return ret;
}
static struct i2c_client *atmel_ecc_i2c_client_alloc(void)
{
struct atmel_i2c_client_priv *i2c_priv, *min_i2c_priv = NULL;
struct i2c_client *client = ERR_PTR(-ENODEV);
int min_tfm_cnt = INT_MAX;
int tfm_cnt;
spin_lock(&driver_data.i2c_list_lock);
if (list_empty(&driver_data.i2c_client_list)) {
spin_unlock(&driver_data.i2c_list_lock);
return ERR_PTR(-ENODEV);
}
list_for_each_entry(i2c_priv, &driver_data.i2c_client_list,
i2c_client_list_node) {
tfm_cnt = atomic_read(&i2c_priv->tfm_count);
if (tfm_cnt < min_tfm_cnt) {
min_tfm_cnt = tfm_cnt;
min_i2c_priv = i2c_priv;
}
if (!min_tfm_cnt)
break;
}
if (min_i2c_priv) {
atomic_inc(&min_i2c_priv->tfm_count);
client = min_i2c_priv->client;
}
spin_unlock(&driver_data.i2c_list_lock);
return client;
}
static void atmel_ecc_i2c_client_free(struct i2c_client *client)
{
struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
atomic_dec(&i2c_priv->tfm_count);
}
static int atmel_ecdh_init_tfm(struct crypto_kpp *tfm)
{
const char *alg = kpp_alg_name(tfm);
struct crypto_kpp *fallback;
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
ctx->curve_id = ECC_CURVE_NIST_P256;
ctx->client = atmel_ecc_i2c_client_alloc();
if (IS_ERR(ctx->client)) {
pr_err("tfm - i2c_client binding failed\n");
return PTR_ERR(ctx->client);
}
fallback = crypto_alloc_kpp(alg, 0, CRYPTO_ALG_NEED_FALLBACK);
if (IS_ERR(fallback)) {
dev_err(&ctx->client->dev, "Failed to allocate transformation for '%s': %ld\n",
alg, PTR_ERR(fallback));
return PTR_ERR(fallback);
}
crypto_kpp_set_flags(fallback, crypto_kpp_get_flags(tfm));
ctx->fallback = fallback;
return 0;
}
static void atmel_ecdh_exit_tfm(struct crypto_kpp *tfm)
{
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
kfree(ctx->public_key);
crypto_free_kpp(ctx->fallback);
atmel_ecc_i2c_client_free(ctx->client);
}
static unsigned int atmel_ecdh_max_size(struct crypto_kpp *tfm)
{
struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
if (ctx->fallback)
return crypto_kpp_maxsize(ctx->fallback);
/*
* The device only supports NIST P256 ECC keys. The public key size will
* always be the same. Use a macro for the key size to avoid unnecessary
* computations.
*/
return ATMEL_ECC_PUBKEY_SIZE;
}
static struct kpp_alg atmel_ecdh_nist_p256 = {
.set_secret = atmel_ecdh_set_secret,
.generate_public_key = atmel_ecdh_generate_public_key,
.compute_shared_secret = atmel_ecdh_compute_shared_secret,
.init = atmel_ecdh_init_tfm,
.exit = atmel_ecdh_exit_tfm,
.max_size = atmel_ecdh_max_size,
.base = {
.cra_flags = CRYPTO_ALG_NEED_FALLBACK,
.cra_name = "ecdh-nist-p256",
.cra_driver_name = "atmel-ecdh",
.cra_priority = ATMEL_ECC_PRIORITY,
.cra_module = THIS_MODULE,
.cra_ctxsize = sizeof(struct atmel_ecdh_ctx),
},
};
static int atmel_ecc_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct atmel_i2c_client_priv *i2c_priv;
int ret;
ret = atmel_i2c_probe(client, id);
if (ret)
return ret;
i2c_priv = i2c_get_clientdata(client);
spin_lock(&driver_data.i2c_list_lock);
list_add_tail(&i2c_priv->i2c_client_list_node,
&driver_data.i2c_client_list);
spin_unlock(&driver_data.i2c_list_lock);
ret = crypto_register_kpp(&atmel_ecdh_nist_p256);
if (ret) {
spin_lock(&driver_data.i2c_list_lock);
list_del(&i2c_priv->i2c_client_list_node);
spin_unlock(&driver_data.i2c_list_lock);
dev_err(&client->dev, "%s alg registration failed\n",
atmel_ecdh_nist_p256.base.cra_driver_name);
} else {
dev_info(&client->dev, "atmel ecc algorithms registered in /proc/crypto\n");
}
return ret;
}
static int atmel_ecc_remove(struct i2c_client *client)
{
struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
/* Return EBUSY if i2c client already allocated. */
if (atomic_read(&i2c_priv->tfm_count)) {
dev_err(&client->dev, "Device is busy\n");
return -EBUSY;
}
crypto_unregister_kpp(&atmel_ecdh_nist_p256);
spin_lock(&driver_data.i2c_list_lock);
list_del(&i2c_priv->i2c_client_list_node);
spin_unlock(&driver_data.i2c_list_lock);
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id atmel_ecc_dt_ids[] = {
{
.compatible = "atmel,atecc508a",
}, {
/* sentinel */
}
};
MODULE_DEVICE_TABLE(of, atmel_ecc_dt_ids);
#endif
static const struct i2c_device_id atmel_ecc_id[] = {
{ "atecc508a", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, atmel_ecc_id);
static struct i2c_driver atmel_ecc_driver = {
.driver = {
.name = "atmel-ecc",
.of_match_table = of_match_ptr(atmel_ecc_dt_ids),
},
.probe = atmel_ecc_probe,
.remove = atmel_ecc_remove,
.id_table = atmel_ecc_id,
};
static int __init atmel_ecc_init(void)
{
spin_lock_init(&driver_data.i2c_list_lock);
INIT_LIST_HEAD(&driver_data.i2c_client_list);
return i2c_add_driver(&atmel_ecc_driver);
}
static void __exit atmel_ecc_exit(void)
{
flush_scheduled_work();
i2c_del_driver(&atmel_ecc_driver);
}
module_init(atmel_ecc_init);
module_exit(atmel_ecc_exit);
MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
MODULE_LICENSE("GPL v2");