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![Ard Biesheuvel](/assets/img/avatar_default.png)
In preparation of adding support for the random number generator in Atmel atsha204a devices, refactor the existing atmel-ecc driver (which drives hardware that is closely related) so we can share the basic I2C and command queuing routines. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
422 lines
10 KiB
C
422 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Microchip / Atmel ECC (I2C) driver.
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*
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* Copyright (c) 2017, Microchip Technology Inc.
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* Author: Tudor Ambarus <tudor.ambarus@microchip.com>
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*/
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/errno.h>
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#include <linux/i2c.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/of_device.h>
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#include <linux/scatterlist.h>
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#include <linux/slab.h>
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#include <linux/workqueue.h>
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#include <crypto/internal/kpp.h>
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#include <crypto/ecdh.h>
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#include <crypto/kpp.h>
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#include "atmel-i2c.h"
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static struct atmel_ecc_driver_data driver_data;
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/**
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* atmel_ecdh_ctx - transformation context
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* @client : pointer to i2c client device
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* @fallback : used for unsupported curves or when user wants to use its own
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* private key.
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* @public_key : generated when calling set_secret(). It's the responsibility
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* of the user to not call set_secret() while
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* generate_public_key() or compute_shared_secret() are in flight.
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* @curve_id : elliptic curve id
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* @n_sz : size in bytes of the n prime
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* @do_fallback: true when the device doesn't support the curve or when the user
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* wants to use its own private key.
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*/
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struct atmel_ecdh_ctx {
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struct i2c_client *client;
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struct crypto_kpp *fallback;
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const u8 *public_key;
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unsigned int curve_id;
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size_t n_sz;
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bool do_fallback;
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};
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static void atmel_ecdh_done(struct atmel_i2c_work_data *work_data, void *areq,
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int status)
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{
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struct kpp_request *req = areq;
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struct atmel_ecdh_ctx *ctx = work_data->ctx;
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struct atmel_i2c_cmd *cmd = &work_data->cmd;
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size_t copied, n_sz;
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if (status)
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goto free_work_data;
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/* might want less than we've got */
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n_sz = min_t(size_t, ctx->n_sz, req->dst_len);
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/* copy the shared secret */
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copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, n_sz),
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&cmd->data[RSP_DATA_IDX], n_sz);
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if (copied != n_sz)
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status = -EINVAL;
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/* fall through */
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free_work_data:
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kzfree(work_data);
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kpp_request_complete(req, status);
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}
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static unsigned int atmel_ecdh_supported_curve(unsigned int curve_id)
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{
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if (curve_id == ECC_CURVE_NIST_P256)
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return ATMEL_ECC_NIST_P256_N_SIZE;
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return 0;
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}
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/*
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* A random private key is generated and stored in the device. The device
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* returns the pair public key.
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*/
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static int atmel_ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
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unsigned int len)
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{
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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struct atmel_i2c_cmd *cmd;
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void *public_key;
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struct ecdh params;
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int ret = -ENOMEM;
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/* free the old public key, if any */
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kfree(ctx->public_key);
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/* make sure you don't free the old public key twice */
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ctx->public_key = NULL;
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if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0) {
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dev_err(&ctx->client->dev, "crypto_ecdh_decode_key failed\n");
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return -EINVAL;
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}
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ctx->n_sz = atmel_ecdh_supported_curve(params.curve_id);
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if (!ctx->n_sz || params.key_size) {
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/* fallback to ecdh software implementation */
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ctx->do_fallback = true;
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return crypto_kpp_set_secret(ctx->fallback, buf, len);
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}
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cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
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if (!cmd)
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return -ENOMEM;
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/*
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* The device only supports NIST P256 ECC keys. The public key size will
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* always be the same. Use a macro for the key size to avoid unnecessary
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* computations.
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*/
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public_key = kmalloc(ATMEL_ECC_PUBKEY_SIZE, GFP_KERNEL);
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if (!public_key)
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goto free_cmd;
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ctx->do_fallback = false;
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ctx->curve_id = params.curve_id;
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atmel_i2c_init_genkey_cmd(cmd, DATA_SLOT_2);
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ret = atmel_i2c_send_receive(ctx->client, cmd);
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if (ret)
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goto free_public_key;
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/* save the public key */
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memcpy(public_key, &cmd->data[RSP_DATA_IDX], ATMEL_ECC_PUBKEY_SIZE);
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ctx->public_key = public_key;
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kfree(cmd);
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return 0;
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free_public_key:
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kfree(public_key);
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free_cmd:
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kfree(cmd);
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return ret;
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}
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static int atmel_ecdh_generate_public_key(struct kpp_request *req)
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{
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struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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size_t copied, nbytes;
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int ret = 0;
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if (ctx->do_fallback) {
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kpp_request_set_tfm(req, ctx->fallback);
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return crypto_kpp_generate_public_key(req);
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}
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if (!ctx->public_key)
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return -EINVAL;
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/* might want less than we've got */
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nbytes = min_t(size_t, ATMEL_ECC_PUBKEY_SIZE, req->dst_len);
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/* public key was saved at private key generation */
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copied = sg_copy_from_buffer(req->dst,
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sg_nents_for_len(req->dst, nbytes),
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ctx->public_key, nbytes);
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if (copied != nbytes)
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ret = -EINVAL;
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return ret;
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}
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static int atmel_ecdh_compute_shared_secret(struct kpp_request *req)
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{
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struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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struct atmel_i2c_work_data *work_data;
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gfp_t gfp;
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int ret;
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if (ctx->do_fallback) {
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kpp_request_set_tfm(req, ctx->fallback);
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return crypto_kpp_compute_shared_secret(req);
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}
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/* must have exactly two points to be on the curve */
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if (req->src_len != ATMEL_ECC_PUBKEY_SIZE)
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return -EINVAL;
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gfp = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ? GFP_KERNEL :
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GFP_ATOMIC;
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work_data = kmalloc(sizeof(*work_data), gfp);
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if (!work_data)
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return -ENOMEM;
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work_data->ctx = ctx;
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work_data->client = ctx->client;
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ret = atmel_i2c_init_ecdh_cmd(&work_data->cmd, req->src);
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if (ret)
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goto free_work_data;
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atmel_i2c_enqueue(work_data, atmel_ecdh_done, req);
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return -EINPROGRESS;
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free_work_data:
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kfree(work_data);
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return ret;
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}
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static struct i2c_client *atmel_ecc_i2c_client_alloc(void)
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{
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struct atmel_i2c_client_priv *i2c_priv, *min_i2c_priv = NULL;
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struct i2c_client *client = ERR_PTR(-ENODEV);
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int min_tfm_cnt = INT_MAX;
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int tfm_cnt;
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spin_lock(&driver_data.i2c_list_lock);
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if (list_empty(&driver_data.i2c_client_list)) {
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spin_unlock(&driver_data.i2c_list_lock);
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return ERR_PTR(-ENODEV);
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}
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list_for_each_entry(i2c_priv, &driver_data.i2c_client_list,
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i2c_client_list_node) {
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tfm_cnt = atomic_read(&i2c_priv->tfm_count);
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if (tfm_cnt < min_tfm_cnt) {
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min_tfm_cnt = tfm_cnt;
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min_i2c_priv = i2c_priv;
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}
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if (!min_tfm_cnt)
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break;
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}
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if (min_i2c_priv) {
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atomic_inc(&min_i2c_priv->tfm_count);
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client = min_i2c_priv->client;
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}
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spin_unlock(&driver_data.i2c_list_lock);
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return client;
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}
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static void atmel_ecc_i2c_client_free(struct i2c_client *client)
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{
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struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
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atomic_dec(&i2c_priv->tfm_count);
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}
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static int atmel_ecdh_init_tfm(struct crypto_kpp *tfm)
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{
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const char *alg = kpp_alg_name(tfm);
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struct crypto_kpp *fallback;
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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ctx->client = atmel_ecc_i2c_client_alloc();
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if (IS_ERR(ctx->client)) {
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pr_err("tfm - i2c_client binding failed\n");
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return PTR_ERR(ctx->client);
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}
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fallback = crypto_alloc_kpp(alg, 0, CRYPTO_ALG_NEED_FALLBACK);
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if (IS_ERR(fallback)) {
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dev_err(&ctx->client->dev, "Failed to allocate transformation for '%s': %ld\n",
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alg, PTR_ERR(fallback));
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return PTR_ERR(fallback);
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}
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crypto_kpp_set_flags(fallback, crypto_kpp_get_flags(tfm));
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ctx->fallback = fallback;
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return 0;
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}
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static void atmel_ecdh_exit_tfm(struct crypto_kpp *tfm)
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{
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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kfree(ctx->public_key);
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crypto_free_kpp(ctx->fallback);
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atmel_ecc_i2c_client_free(ctx->client);
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}
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static unsigned int atmel_ecdh_max_size(struct crypto_kpp *tfm)
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{
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struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
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if (ctx->fallback)
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return crypto_kpp_maxsize(ctx->fallback);
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/*
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* The device only supports NIST P256 ECC keys. The public key size will
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* always be the same. Use a macro for the key size to avoid unnecessary
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* computations.
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*/
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return ATMEL_ECC_PUBKEY_SIZE;
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}
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static struct kpp_alg atmel_ecdh = {
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.set_secret = atmel_ecdh_set_secret,
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.generate_public_key = atmel_ecdh_generate_public_key,
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.compute_shared_secret = atmel_ecdh_compute_shared_secret,
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.init = atmel_ecdh_init_tfm,
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.exit = atmel_ecdh_exit_tfm,
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.max_size = atmel_ecdh_max_size,
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.base = {
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.cra_flags = CRYPTO_ALG_NEED_FALLBACK,
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.cra_name = "ecdh",
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.cra_driver_name = "atmel-ecdh",
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.cra_priority = ATMEL_ECC_PRIORITY,
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.cra_module = THIS_MODULE,
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.cra_ctxsize = sizeof(struct atmel_ecdh_ctx),
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},
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};
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static int atmel_ecc_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct atmel_i2c_client_priv *i2c_priv;
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int ret;
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ret = atmel_i2c_probe(client, id);
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if (ret)
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return ret;
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i2c_priv = i2c_get_clientdata(client);
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spin_lock(&driver_data.i2c_list_lock);
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list_add_tail(&i2c_priv->i2c_client_list_node,
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&driver_data.i2c_client_list);
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spin_unlock(&driver_data.i2c_list_lock);
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ret = crypto_register_kpp(&atmel_ecdh);
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if (ret) {
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spin_lock(&driver_data.i2c_list_lock);
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list_del(&i2c_priv->i2c_client_list_node);
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spin_unlock(&driver_data.i2c_list_lock);
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dev_err(&client->dev, "%s alg registration failed\n",
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atmel_ecdh.base.cra_driver_name);
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} else {
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dev_info(&client->dev, "atmel ecc algorithms registered in /proc/crypto\n");
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}
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return ret;
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}
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static int atmel_ecc_remove(struct i2c_client *client)
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{
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struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client);
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/* Return EBUSY if i2c client already allocated. */
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if (atomic_read(&i2c_priv->tfm_count)) {
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dev_err(&client->dev, "Device is busy\n");
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return -EBUSY;
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}
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crypto_unregister_kpp(&atmel_ecdh);
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spin_lock(&driver_data.i2c_list_lock);
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list_del(&i2c_priv->i2c_client_list_node);
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spin_unlock(&driver_data.i2c_list_lock);
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return 0;
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}
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#ifdef CONFIG_OF
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static const struct of_device_id atmel_ecc_dt_ids[] = {
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{
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.compatible = "atmel,atecc508a",
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}, {
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/* sentinel */
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}
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};
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MODULE_DEVICE_TABLE(of, atmel_ecc_dt_ids);
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#endif
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static const struct i2c_device_id atmel_ecc_id[] = {
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{ "atecc508a", 0 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, atmel_ecc_id);
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static struct i2c_driver atmel_ecc_driver = {
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.driver = {
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.name = "atmel-ecc",
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.of_match_table = of_match_ptr(atmel_ecc_dt_ids),
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},
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.probe = atmel_ecc_probe,
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.remove = atmel_ecc_remove,
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.id_table = atmel_ecc_id,
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};
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static int __init atmel_ecc_init(void)
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{
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spin_lock_init(&driver_data.i2c_list_lock);
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INIT_LIST_HEAD(&driver_data.i2c_client_list);
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return i2c_add_driver(&atmel_ecc_driver);
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}
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static void __exit atmel_ecc_exit(void)
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{
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flush_scheduled_work();
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i2c_del_driver(&atmel_ecc_driver);
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}
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module_init(atmel_ecc_init);
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module_exit(atmel_ecc_exit);
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MODULE_AUTHOR("Tudor Ambarus <tudor.ambarus@microchip.com>");
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MODULE_DESCRIPTION("Microchip / Atmel ECC (I2C) driver");
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MODULE_LICENSE("GPL v2");
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