// SPDX-License-Identifier: GPL-2.0-or-later /* ECDH key-agreement protocol * * Copyright (c) 2016, Intel Corporation * Authors: Salvator Benedetto <salvatore.benedetto@intel.com> */ #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) 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); if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits, (const u64 *)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) { 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); } subsys_initcall(ecdh_init); module_exit(ecdh_exit); MODULE_ALIAS_CRYPTO("ecdh"); MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("ECDH generic algorithm");