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, &params) < 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");