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crypto: dh - Add DH software implementation
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* 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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Salvatore Benedetto authored and herbertx committed Jun 23, 2016
1 parent 4e5f2c4 commit 802c7f1
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8 changes: 8 additions & 0 deletions crypto/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,14 @@ config CRYPTO_RSA
help
Generic implementation of the RSA public key algorithm.

config CRYPTO_DH
tristate "Diffie-Hellman algorithm"
select CRYPTO_KPP
select MPILIB
help
Generic implementation of the Diffie-Hellman algorithm.


config CRYPTO_MANAGER
tristate "Cryptographic algorithm manager"
select CRYPTO_MANAGER2
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4 changes: 4 additions & 0 deletions crypto/Makefile
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Expand Up @@ -32,6 +32,10 @@ obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
obj-$(CONFIG_CRYPTO_KPP2) += kpp.o

dh_generic-y := dh.o
dh_generic-y += dh_helper.o
obj-$(CONFIG_CRYPTO_DH) += dh_generic.o

$(obj)/rsapubkey-asn1.o: $(obj)/rsapubkey-asn1.c $(obj)/rsapubkey-asn1.h
$(obj)/rsaprivkey-asn1.o: $(obj)/rsaprivkey-asn1.c $(obj)/rsaprivkey-asn1.h
clean-files += rsapubkey-asn1.c rsapubkey-asn1.h
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189 changes: 189 additions & 0 deletions crypto/dh.c
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@@ -0,0 +1,189 @@
/* Diffie-Hellman Key Agreement Method [RFC2631]
*
* Copyright (c) 2016, Intel Corporation
* Authors: Salvatore Benedetto <[email protected]>
*
* 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/dh.h>
#include <linux/mpi.h>

struct dh_ctx {
MPI p;
MPI g;
MPI xa;
};

static inline void dh_clear_params(struct dh_ctx *ctx)
{
mpi_free(ctx->p);
mpi_free(ctx->g);
ctx->p = NULL;
ctx->g = NULL;
}

static void dh_free_ctx(struct dh_ctx *ctx)
{
dh_clear_params(ctx);
mpi_free(ctx->xa);
ctx->xa = NULL;
}

/*
* If base is g we compute the public key
* ya = g^xa mod p; [RFC2631 sec 2.1.1]
* else if base if the counterpart public key we compute the shared secret
* ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
*/
static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
{
/* val = base^xa mod p */
return mpi_powm(val, base, ctx->xa, ctx->p);
}

static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
{
return kpp_tfm_ctx(tfm);
}

static int dh_check_params_length(unsigned int p_len)
{
return (p_len < 1536) ? -EINVAL : 0;
}

static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
{
if (unlikely(!params->p || !params->g))
return -EINVAL;

if (dh_check_params_length(params->p_size << 3))
return -EINVAL;

ctx->p = mpi_read_raw_data(params->p, params->p_size);
if (!ctx->p)
return -EINVAL;

ctx->g = mpi_read_raw_data(params->g, params->g_size);
if (!ctx->g) {
mpi_free(ctx->p);
return -EINVAL;
}

return 0;
}

static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
{
struct dh_ctx *ctx = dh_get_ctx(tfm);
struct dh params;

if (crypto_dh_decode_key(buf, len, &params) < 0)
return -EINVAL;

if (dh_set_params(ctx, &params) < 0)
return -EINVAL;

ctx->xa = mpi_read_raw_data(params.key, params.key_size);
if (!ctx->xa) {
dh_clear_params(ctx);
return -EINVAL;
}

return 0;
}

static int dh_compute_value(struct kpp_request *req)
{
struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
struct dh_ctx *ctx = dh_get_ctx(tfm);
MPI base, val = mpi_alloc(0);
int ret = 0;
int sign;

if (!val)
return -ENOMEM;

if (unlikely(!ctx->xa)) {
ret = -EINVAL;
goto err_free_val;
}

if (req->src) {
base = mpi_read_raw_from_sgl(req->src, req->src_len);
if (!base) {
ret = EINVAL;
goto err_free_val;
}
} else {
base = ctx->g;
}

ret = _compute_val(ctx, base, val);
if (ret)
goto err_free_base;

ret = mpi_write_to_sgl(val, req->dst, &req->dst_len, &sign);
if (ret)
goto err_free_base;

if (sign < 0)
ret = -EBADMSG;
err_free_base:
if (req->src)
mpi_free(base);
err_free_val:
mpi_free(val);
return ret;
}

static int dh_max_size(struct crypto_kpp *tfm)
{
struct dh_ctx *ctx = dh_get_ctx(tfm);

return mpi_get_size(ctx->p);
}

static void dh_exit_tfm(struct crypto_kpp *tfm)
{
struct dh_ctx *ctx = dh_get_ctx(tfm);

dh_free_ctx(ctx);
}

static struct kpp_alg dh = {
.set_secret = dh_set_secret,
.generate_public_key = dh_compute_value,
.compute_shared_secret = dh_compute_value,
.max_size = dh_max_size,
.exit = dh_exit_tfm,
.base = {
.cra_name = "dh",
.cra_driver_name = "dh-generic",
.cra_priority = 100,
.cra_module = THIS_MODULE,
.cra_ctxsize = sizeof(struct dh_ctx),
},
};

static int dh_init(void)
{
return crypto_register_kpp(&dh);
}

static void dh_exit(void)
{
crypto_unregister_kpp(&dh);
}

module_init(dh_init);
module_exit(dh_exit);
MODULE_ALIAS_CRYPTO("dh");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("DH generic algorithm");
95 changes: 95 additions & 0 deletions crypto/dh_helper.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,95 @@
/*
* Copyright (c) 2016, Intel Corporation
* Authors: Salvatore Benedetto <[email protected]>
*
* 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/kernel.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/string.h>
#include <crypto/dh.h>
#include <crypto/kpp.h>

#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))

static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
{
memcpy(dst, src, size);
return dst + size;
}

static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
{
memcpy(dst, src, size);
return src + size;
}

static inline int dh_data_size(const struct dh *p)
{
return p->key_size + p->p_size + p->g_size;
}

int crypto_dh_key_len(const struct dh *p)
{
return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
}
EXPORT_SYMBOL_GPL(crypto_dh_key_len);

int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
{
u8 *ptr = buf;
struct kpp_secret secret = {
.type = CRYPTO_KPP_SECRET_TYPE_DH,
.len = len
};

if (unlikely(!buf))
return -EINVAL;

if (len != crypto_dh_key_len(params))
return -EINVAL;

ptr = dh_pack_data(ptr, &secret, sizeof(secret));
ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
ptr = dh_pack_data(ptr, params->key, params->key_size);
ptr = dh_pack_data(ptr, params->p, params->p_size);
dh_pack_data(ptr, params->g, params->g_size);

return 0;
}
EXPORT_SYMBOL_GPL(crypto_dh_encode_key);

int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
{
const u8 *ptr = buf;
struct kpp_secret secret;

if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
return -EINVAL;

ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
return -EINVAL;

ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
if (secret.len != crypto_dh_key_len(params))
return -EINVAL;

/* Don't allocate memory. Set pointers to data within
* the given buffer
*/
params->key = (void *)ptr;
params->p = (void *)(ptr + params->key_size);
params->g = (void *)(ptr + params->key_size + params->p_size);

return 0;
}
EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
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