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![Stephan Müller](/assets/img/avatar_default.png)
After the generation of a local public key, SP800-56A rev 3 section 5.6.2.1.3 mandates a validation of that key with a full validation compliant to section 5.6.2.3.1. Only if the full validation passes, the key is allowed to be used. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
277 lines
5.4 KiB
C
277 lines
5.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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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 <salvatore.benedetto@intel.com>
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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/fips.h>
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#include <linux/mpi.h>
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struct dh_ctx {
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MPI p; /* Value is guaranteed to be set. */
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MPI q; /* Value is optional. */
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MPI g; /* Value is guaranteed to be set. */
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MPI xa; /* Value is guaranteed to be set. */
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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->q);
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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 (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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if (params->q && params->q_size) {
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ctx->q = mpi_read_raw_data(params->q, params->q_size);
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if (!ctx->q)
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return -EINVAL;
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}
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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, const void *buf,
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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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/*
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* SP800-56A public key verification:
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*
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* * If Q is provided as part of the domain paramenters, a full validation
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* according to SP800-56A section 5.6.2.3.1 is performed.
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*
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* * If Q is not provided, a partial validation according to SP800-56A section
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* 5.6.2.3.2 is performed.
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*/
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static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
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{
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if (unlikely(!ctx->p))
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return -EINVAL;
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/*
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* Step 1: Verify that 2 <= y <= p - 2.
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*
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* The upper limit check is actually y < p instead of y < p - 1
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* as the mpi_sub_ui function is yet missing.
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*/
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if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0)
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return -EINVAL;
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/* Step 2: Verify that 1 = y^q mod p */
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if (ctx->q) {
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MPI val = mpi_alloc(0);
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int ret;
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if (!val)
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return -ENOMEM;
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ret = mpi_powm(val, y, ctx->q, ctx->p);
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if (ret) {
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mpi_free(val);
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return ret;
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}
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ret = mpi_cmp_ui(val, 1);
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mpi_free(val);
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if (ret != 0)
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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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ret = dh_is_pubkey_valid(ctx, base);
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if (ret)
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goto err_free_base;
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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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if (fips_enabled) {
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/* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */
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if (req->src) {
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MPI pone;
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/* z <= 1 */
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if (mpi_cmp_ui(val, 1) < 1) {
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ret = -EBADMSG;
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goto err_free_base;
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}
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/* z == p - 1 */
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pone = mpi_alloc(0);
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if (!pone) {
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ret = -ENOMEM;
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goto err_free_base;
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}
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ret = mpi_sub_ui(pone, ctx->p, 1);
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if (!ret && !mpi_cmp(pone, val))
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ret = -EBADMSG;
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mpi_free(pone);
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if (ret)
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goto err_free_base;
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/* SP800-56A rev 3 5.6.2.1.3 key check */
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} else {
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if (dh_is_pubkey_valid(ctx, val)) {
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ret = -EAGAIN;
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goto err_free_val;
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}
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}
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}
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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 unsigned 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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subsys_initcall(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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