diff options
Diffstat (limited to 'crypto/ecdh.c')
| -rw-r--r-- | crypto/ecdh.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/crypto/ecdh.c b/crypto/ecdh.c new file mode 100644 index 0000000..3de2898 --- /dev/null +++ b/crypto/ecdh.c @@ -0,0 +1,151 @@ +/* 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 Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, 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, 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"); |
