185 lines
3.7 KiB
C
185 lines
3.7 KiB
C
/* Diffie-Hellman Key Agreement Method [RFC2631]
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*
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* Copyright (c) 2016, Intel Corporation
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* Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <crypto/internal/kpp.h>
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#include <crypto/kpp.h>
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#include <crypto/dh.h>
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#include <linux/mpi.h>
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struct dh_ctx {
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MPI p;
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MPI g;
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MPI xa;
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};
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static void dh_clear_ctx(struct dh_ctx *ctx)
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{
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mpi_free(ctx->p);
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mpi_free(ctx->g);
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mpi_free(ctx->xa);
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memset(ctx, 0, sizeof(*ctx));
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}
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/*
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* If base is g we compute the public key
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* ya = g^xa mod p; [RFC2631 sec 2.1.1]
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* else if base if the counterpart public key we compute the shared secret
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* ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
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*/
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static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
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{
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/* val = base^xa mod p */
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return mpi_powm(val, base, ctx->xa, ctx->p);
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}
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static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
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{
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return kpp_tfm_ctx(tfm);
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}
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static int dh_check_params_length(unsigned int p_len)
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{
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return (p_len < 1536) ? -EINVAL : 0;
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}
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static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
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{
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if (unlikely(!params->p || !params->g))
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return -EINVAL;
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if (dh_check_params_length(params->p_size << 3))
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return -EINVAL;
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ctx->p = mpi_read_raw_data(params->p, params->p_size);
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if (!ctx->p)
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return -EINVAL;
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ctx->g = mpi_read_raw_data(params->g, params->g_size);
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if (!ctx->g)
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return -EINVAL;
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return 0;
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}
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static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
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{
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struct dh_ctx *ctx = dh_get_ctx(tfm);
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struct dh params;
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/* Free the old MPI key if any */
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dh_clear_ctx(ctx);
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if (crypto_dh_decode_key(buf, len, ¶ms) < 0)
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goto err_clear_ctx;
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if (dh_set_params(ctx, ¶ms) < 0)
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goto err_clear_ctx;
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ctx->xa = mpi_read_raw_data(params.key, params.key_size);
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if (!ctx->xa)
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goto err_clear_ctx;
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return 0;
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err_clear_ctx:
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dh_clear_ctx(ctx);
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return -EINVAL;
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}
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static int dh_compute_value(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 dh_ctx *ctx = dh_get_ctx(tfm);
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MPI base, val = mpi_alloc(0);
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int ret = 0;
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int sign;
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if (!val)
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return -ENOMEM;
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if (unlikely(!ctx->xa)) {
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ret = -EINVAL;
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goto err_free_val;
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}
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if (req->src) {
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base = mpi_read_raw_from_sgl(req->src, req->src_len);
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if (!base) {
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ret = EINVAL;
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goto err_free_val;
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}
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} else {
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base = ctx->g;
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}
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ret = _compute_val(ctx, base, val);
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if (ret)
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goto err_free_base;
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ret = mpi_write_to_sgl(val, req->dst, req->dst_len, &sign);
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if (ret)
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goto err_free_base;
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if (sign < 0)
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ret = -EBADMSG;
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err_free_base:
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if (req->src)
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mpi_free(base);
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err_free_val:
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mpi_free(val);
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return ret;
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}
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static int dh_max_size(struct crypto_kpp *tfm)
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{
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struct dh_ctx *ctx = dh_get_ctx(tfm);
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return mpi_get_size(ctx->p);
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}
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static void dh_exit_tfm(struct crypto_kpp *tfm)
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{
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struct dh_ctx *ctx = dh_get_ctx(tfm);
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dh_clear_ctx(ctx);
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}
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static struct kpp_alg dh = {
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.set_secret = dh_set_secret,
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.generate_public_key = dh_compute_value,
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.compute_shared_secret = dh_compute_value,
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.max_size = dh_max_size,
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.exit = dh_exit_tfm,
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.base = {
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.cra_name = "dh",
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.cra_driver_name = "dh-generic",
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.cra_priority = 100,
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.cra_module = THIS_MODULE,
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.cra_ctxsize = sizeof(struct dh_ctx),
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},
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};
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static int dh_init(void)
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{
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return crypto_register_kpp(&dh);
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}
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static void dh_exit(void)
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{
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crypto_unregister_kpp(&dh);
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}
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module_init(dh_init);
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module_exit(dh_exit);
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MODULE_ALIAS_CRYPTO("dh");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("DH generic algorithm");
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