diff options
Diffstat (limited to 'crypto/ecdh.c')
| -rw-r--r-- | crypto/ecdh.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/crypto/ecdh.c b/crypto/ecdh.c new file mode 100644 index 000000000..34605509b --- /dev/null +++ b/crypto/ecdh.c @@ -0,0 +1,175 @@ +/* ECDH key-agreement protocol + * + * Copyright (c) 2016, Intel Corporation + * Authors: Salvator Benedetto <salvatore.benedetto@intel.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/module.h> +#include <crypto/internal/kpp.h> +#include <crypto/kpp.h> +#include <crypto/ecdh.h> +#include <linux/scatterlist.h> +#include "ecc.h" + +struct ecdh_ctx { + unsigned int curve_id; + unsigned int ndigits; + u64 private_key[ECC_MAX_DIGITS]; +}; + +static inline struct ecdh_ctx *ecdh_get_ctx(struct crypto_kpp *tfm) +{ + return kpp_tfm_ctx(tfm); +} + +static unsigned int ecdh_supported_curve(unsigned int curve_id) +{ + switch (curve_id) { + case ECC_CURVE_NIST_P192: return ECC_CURVE_NIST_P192_DIGITS; + case ECC_CURVE_NIST_P256: return ECC_CURVE_NIST_P256_DIGITS; + default: return 0; + } +} + +static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf, + unsigned int len) +{ + struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); + struct ecdh params; + unsigned int ndigits; + + if (crypto_ecdh_decode_key(buf, len, ¶ms) < 0 || + params.key_size > sizeof(ctx->private_key)) + return -EINVAL; + + ndigits = ecdh_supported_curve(params.curve_id); + if (!ndigits) + return -EINVAL; + + ctx->curve_id = params.curve_id; + ctx->ndigits = ndigits; + + if (!params.key || !params.key_size) + return ecc_gen_privkey(ctx->curve_id, ctx->ndigits, + ctx->private_key); + + memcpy(ctx->private_key, params.key, params.key_size); + + if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, + ctx->private_key, params.key_size) < 0) { + memzero_explicit(ctx->private_key, params.key_size); + return -EINVAL; + } + return 0; +} + +static int ecdh_compute_value(struct kpp_request *req) +{ + struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); + struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); + u64 *public_key; + u64 *shared_secret = NULL; + void *buf; + size_t copied, nbytes, public_key_sz; + int ret = -ENOMEM; + + nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; + /* Public part is a point thus it has both coordinates */ + public_key_sz = 2 * nbytes; + + public_key = kmalloc(public_key_sz, GFP_KERNEL); + if (!public_key) + return -ENOMEM; + + if (req->src) { + shared_secret = kmalloc(nbytes, GFP_KERNEL); + if (!shared_secret) + goto free_pubkey; + + /* from here on it's invalid parameters */ + ret = -EINVAL; + + /* must have exactly two points to be on the curve */ + if (public_key_sz != req->src_len) + goto free_all; + + copied = sg_copy_to_buffer(req->src, + sg_nents_for_len(req->src, + public_key_sz), + public_key, public_key_sz); + if (copied != public_key_sz) + goto free_all; + + ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, + ctx->private_key, public_key, + shared_secret); + + buf = shared_secret; + } else { + ret = ecc_make_pub_key(ctx->curve_id, ctx->ndigits, + ctx->private_key, public_key); + buf = public_key; + nbytes = public_key_sz; + } + + if (ret < 0) + goto free_all; + + /* might want less than we've got */ + nbytes = min_t(size_t, nbytes, req->dst_len); + copied = sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, + nbytes), + buf, nbytes); + if (copied != nbytes) + ret = -EINVAL; + + /* fall through */ +free_all: + kzfree(shared_secret); +free_pubkey: + kfree(public_key); + return ret; +} + +static unsigned int ecdh_max_size(struct crypto_kpp *tfm) +{ + struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); + + /* Public key is made of two coordinates, add one to the left shift */ + return ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1); +} + +static struct kpp_alg ecdh = { + .set_secret = ecdh_set_secret, + .generate_public_key = ecdh_compute_value, + .compute_shared_secret = ecdh_compute_value, + .max_size = ecdh_max_size, + .base = { + .cra_name = "ecdh", + .cra_driver_name = "ecdh-generic", + .cra_priority = 100, + .cra_module = THIS_MODULE, + .cra_ctxsize = sizeof(struct ecdh_ctx), + }, +}; + +static int ecdh_init(void) +{ + return crypto_register_kpp(&ecdh); +} + +static void ecdh_exit(void) +{ + crypto_unregister_kpp(&ecdh); +} + +module_init(ecdh_init); +module_exit(ecdh_exit); +MODULE_ALIAS_CRYPTO("ecdh"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("ECDH generic algorithm"); |