| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* Diffie-Hellman Key Agreement Method [RFC2631] |
| * |
| * Copyright (c) 2016, Intel Corporation |
| * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com> |
| */ |
| |
| #include <linux/module.h> |
| #include <crypto/internal/kpp.h> |
| #include <crypto/kpp.h> |
| #include <crypto/dh.h> |
| #include <linux/fips.h> |
| #include <linux/mpi.h> |
| |
| struct dh_ctx { |
| MPI p; /* Value is guaranteed to be set. */ |
| MPI q; /* Value is optional. */ |
| MPI g; /* Value is guaranteed to be set. */ |
| MPI xa; /* Value is guaranteed to be set. */ |
| }; |
| |
| static void dh_clear_ctx(struct dh_ctx *ctx) |
| { |
| mpi_free(ctx->p); |
| mpi_free(ctx->q); |
| mpi_free(ctx->g); |
| mpi_free(ctx->xa); |
| memset(ctx, 0, sizeof(*ctx)); |
| } |
| |
| /* |
| * 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 (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; |
| |
| if (params->q && params->q_size) { |
| ctx->q = mpi_read_raw_data(params->q, params->q_size); |
| if (!ctx->q) |
| return -EINVAL; |
| } |
| |
| ctx->g = mpi_read_raw_data(params->g, params->g_size); |
| if (!ctx->g) |
| return -EINVAL; |
| |
| return 0; |
| } |
| |
| static int dh_set_secret(struct crypto_kpp *tfm, const void *buf, |
| unsigned int len) |
| { |
| struct dh_ctx *ctx = dh_get_ctx(tfm); |
| struct dh params; |
| |
| /* Free the old MPI key if any */ |
| dh_clear_ctx(ctx); |
| |
| if (crypto_dh_decode_key(buf, len, ¶ms) < 0) |
| goto err_clear_ctx; |
| |
| if (dh_set_params(ctx, ¶ms) < 0) |
| goto err_clear_ctx; |
| |
| ctx->xa = mpi_read_raw_data(params.key, params.key_size); |
| if (!ctx->xa) |
| goto err_clear_ctx; |
| |
| return 0; |
| |
| err_clear_ctx: |
| dh_clear_ctx(ctx); |
| return -EINVAL; |
| } |
| |
| /* |
| * SP800-56A public key verification: |
| * |
| * * If Q is provided as part of the domain paramenters, a full validation |
| * according to SP800-56A section 5.6.2.3.1 is performed. |
| * |
| * * If Q is not provided, a partial validation according to SP800-56A section |
| * 5.6.2.3.2 is performed. |
| */ |
| static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y) |
| { |
| if (unlikely(!ctx->p)) |
| return -EINVAL; |
| |
| /* |
| * Step 1: Verify that 2 <= y <= p - 2. |
| * |
| * The upper limit check is actually y < p instead of y < p - 1 |
| * as the mpi_sub_ui function is yet missing. |
| */ |
| if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0) |
| return -EINVAL; |
| |
| /* Step 2: Verify that 1 = y^q mod p */ |
| if (ctx->q) { |
| MPI val = mpi_alloc(0); |
| int ret; |
| |
| if (!val) |
| return -ENOMEM; |
| |
| ret = mpi_powm(val, y, ctx->q, ctx->p); |
| |
| if (ret) { |
| mpi_free(val); |
| return ret; |
| } |
| |
| ret = mpi_cmp_ui(val, 1); |
| |
| mpi_free(val); |
| |
| if (ret != 0) |
| 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; |
| } |
| ret = dh_is_pubkey_valid(ctx, base); |
| if (ret) |
| goto err_free_base; |
| } else { |
| base = ctx->g; |
| } |
| |
| ret = _compute_val(ctx, base, val); |
| if (ret) |
| goto err_free_base; |
| |
| if (fips_enabled) { |
| /* SP800-56A rev3 5.7.1.1 check: Validation of shared secret */ |
| if (req->src) { |
| MPI pone; |
| |
| /* z <= 1 */ |
| if (mpi_cmp_ui(val, 1) < 1) { |
| ret = -EBADMSG; |
| goto err_free_base; |
| } |
| |
| /* z == p - 1 */ |
| pone = mpi_alloc(0); |
| |
| if (!pone) { |
| ret = -ENOMEM; |
| goto err_free_base; |
| } |
| |
| ret = mpi_sub_ui(pone, ctx->p, 1); |
| if (!ret && !mpi_cmp(pone, val)) |
| ret = -EBADMSG; |
| |
| mpi_free(pone); |
| |
| if (ret) |
| goto err_free_base; |
| |
| /* SP800-56A rev 3 5.6.2.1.3 key check */ |
| } else { |
| if (dh_is_pubkey_valid(ctx, val)) { |
| ret = -EAGAIN; |
| goto err_free_val; |
| } |
| } |
| } |
| |
| 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 unsigned 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_clear_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); |
| } |
| |
| subsys_initcall(dh_init); |
| module_exit(dh_exit); |
| MODULE_ALIAS_CRYPTO("dh"); |
| MODULE_LICENSE("GPL"); |
| MODULE_DESCRIPTION("DH generic algorithm"); |