diff options
Diffstat (limited to '')
| -rw-r--r-- | drivers/crypto/atmel-ecc.c | 415 |
1 files changed, 415 insertions, 0 deletions
diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c new file mode 100644 index 0000000000..590ea984c6 --- /dev/null +++ b/drivers/crypto/atmel-ecc.c @@ -0,0 +1,415 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Microchip / Atmel ECC (I2C) driver. + * + * Copyright (c) 2017, Microchip Technology Inc. + * Author: Tudor Ambarus + */ + +#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.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) +{ + struct atmel_i2c_client_priv *i2c_priv; + int ret; + + ret = atmel_i2c_probe(client); + 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 void 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)) { + /* + * After we return here, the memory backing the device is freed. + * That happens no matter what the return value of this function + * is because in the Linux device model there is no error + * handling for unbinding a driver. + * If there is still some action pending, it probably involves + * accessing the freed memory. + */ + dev_emerg(&client->dev, "Device is busy, expect memory corruption.\n"); + return; + } + + 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); +} + +#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) +{ + atmel_i2c_flush_queue(); + i2c_del_driver(&atmel_ecc_driver); +} + +module_init(atmel_ecc_init); +module_exit(atmel_ecc_exit); + +MODULE_AUTHOR("Tudor Ambarus"); +MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver"); +MODULE_LICENSE("GPL v2"); |