/* 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]; u64 public_key[2 * ECC_MAX_DIGITS]; u64 shared_secret[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 3; case ECC_CURVE_NIST_P256: return 4; 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) return -EINVAL; ndigits = ecdh_supported_curve(params.curve_id); if (!ndigits) return -EINVAL; ctx->curve_id = params.curve_id; ctx->ndigits = ndigits; if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, (const u8 *)params.key, params.key_size) < 0) return -EINVAL; memcpy(ctx->private_key, params.key, params.key_size); return 0; } static int ecdh_compute_value(struct kpp_request *req) { int ret = 0; struct crypto_kpp *tfm = crypto_kpp_reqtfm(req); struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); size_t copied, nbytes; void *buf; nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; if (req->src) { copied = sg_copy_to_buffer(req->src, 1, ctx->public_key, 2 * nbytes); if (copied != 2 * nbytes) return -EINVAL; ret = crypto_ecdh_shared_secret(ctx->curve_id, ctx->ndigits, (const u8 *)ctx->private_key, nbytes, (const u8 *)ctx->public_key, 2 * nbytes, (u8 *)ctx->shared_secret, nbytes); buf = ctx->shared_secret; } else { ret = ecdh_make_pub_key(ctx->curve_id, ctx->ndigits, (const u8 *)ctx->private_key, nbytes, (u8 *)ctx->public_key, sizeof(ctx->public_key)); buf = ctx->public_key; /* Public part is a point thus it has both coordinates */ nbytes *= 2; } if (ret < 0) return ret; copied = sg_copy_from_buffer(req->dst, 1, buf, nbytes); if (copied != nbytes) return -EINVAL; return ret; } static int ecdh_max_size(struct crypto_kpp *tfm) { struct ecdh_ctx *ctx = ecdh_get_ctx(tfm); int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT; /* Public key is made of two coordinates */ return 2 * nbytes; } static void no_exit_tfm(struct crypto_kpp *tfm) { return; } 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, .exit = no_exit_tfm, .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");