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Salvatore Benedettoherbertx
Salvatore Benedetto
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herbertx
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crypto: dh - Add DH software implementation
* Implement MPI based Diffie-Hellman under kpp API * Test provided uses data generad by OpenSSL Signed-off-by: Salvatore Benedetto <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
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‎crypto/Kconfig

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@@ -111,6 +111,14 @@ config CRYPTO_RSA
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help
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Generic implementation of the RSA public key algorithm.
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config CRYPTO_DH
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tristate "Diffie-Hellman algorithm"
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select CRYPTO_KPP
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select MPILIB
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help
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Generic implementation of the Diffie-Hellman algorithm.
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config CRYPTO_MANAGER
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tristate "Cryptographic algorithm manager"
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select CRYPTO_MANAGER2

‎crypto/Makefile

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@@ -32,6 +32,10 @@ obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
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obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
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obj-$(CONFIG_CRYPTO_KPP2) += kpp.o
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dh_generic-y := dh.o
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dh_generic-y += dh_helper.o
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obj-$(CONFIG_CRYPTO_DH) += dh_generic.o
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$(obj)/rsapubkey-asn1.o: $(obj)/rsapubkey-asn1.c $(obj)/rsapubkey-asn1.h
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$(obj)/rsaprivkey-asn1.o: $(obj)/rsaprivkey-asn1.c $(obj)/rsaprivkey-asn1.h
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clean-files += rsapubkey-asn1.c rsapubkey-asn1.h

‎crypto/dh.c

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/* 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 <[email protected]>
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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 inline void dh_clear_params(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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ctx->p = NULL;
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ctx->g = NULL;
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}
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static void dh_free_ctx(struct dh_ctx *ctx)
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{
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dh_clear_params(ctx);
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mpi_free(ctx->xa);
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ctx->xa = NULL;
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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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mpi_free(ctx->p);
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return -EINVAL;
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}
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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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if (crypto_dh_decode_key(buf, len, &params) < 0)
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return -EINVAL;
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if (dh_set_params(ctx, &params) < 0)
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return -EINVAL;
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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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dh_clear_params(ctx);
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return -EINVAL;
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}
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return 0;
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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_free_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");

‎crypto/dh_helper.c

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@@ -0,0 +1,95 @@
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/*
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* Copyright (c) 2016, Intel Corporation
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* Authors: Salvatore Benedetto <[email protected]>
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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/kernel.h>
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#include <linux/export.h>
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#include <linux/err.h>
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#include <linux/string.h>
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#include <crypto/dh.h>
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#include <crypto/kpp.h>
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#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
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static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
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{
21+
memcpy(dst, src, size);
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return dst + size;
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}
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static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
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{
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memcpy(dst, src, size);
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return src + size;
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}
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static inline int dh_data_size(const struct dh *p)
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{
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return p->key_size + p->p_size + p->g_size;
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}
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int crypto_dh_key_len(const struct dh *p)
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{
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return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
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}
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EXPORT_SYMBOL_GPL(crypto_dh_key_len);
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int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
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{
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u8 *ptr = buf;
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struct kpp_secret secret = {
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.type = CRYPTO_KPP_SECRET_TYPE_DH,
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.len = len
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};
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if (unlikely(!buf))
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return -EINVAL;
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if (len != crypto_dh_key_len(params))
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return -EINVAL;
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ptr = dh_pack_data(ptr, &secret, sizeof(secret));
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ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
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ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
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ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
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ptr = dh_pack_data(ptr, params->key, params->key_size);
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ptr = dh_pack_data(ptr, params->p, params->p_size);
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dh_pack_data(ptr, params->g, params->g_size);
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return 0;
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}
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EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
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int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
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{
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const u8 *ptr = buf;
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struct kpp_secret secret;
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if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
74+
return -EINVAL;
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ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
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if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
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return -EINVAL;
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80+
ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
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ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
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ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
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if (secret.len != crypto_dh_key_len(params))
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return -EINVAL;
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/* Don't allocate memory. Set pointers to data within
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* the given buffer
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*/
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params->key = (void *)ptr;
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params->p = (void *)(ptr + params->key_size);
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params->g = (void *)(ptr + params->key_size + params->p_size);
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return 0;
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}
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EXPORT_SYMBOL_GPL(crypto_dh_decode_key);

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