diff options
Diffstat (limited to 'crypto/dh.c')
| -rw-r--r-- | crypto/dh.c | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/crypto/dh.c b/crypto/dh.c new file mode 100644 index 000000000..09a44de42 --- /dev/null +++ b/crypto/dh.c @@ -0,0 +1,243 @@ +/* Diffie-Hellman Key Agreement Method [RFC2631] + * + * Copyright (c) 2016, Intel Corporation + * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, 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; /* 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; + + 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); +} + +module_init(dh_init); +module_exit(dh_exit); +MODULE_ALIAS_CRYPTO("dh"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("DH generic algorithm"); |