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![Herbert Xu](/assets/img/avatar_default.png)
Every implementation of RSA that we have naturally generates output with leading zeroes. The one and only user of RSA, pkcs1pad wants to have those leading zeroes in place, in fact because they are currently absent it has to write those zeroes itself. So we shouldn't be stripping leading zeroes in the first place. In fact this patch makes rsa-generic produce output with fixed length so that pkcs1pad does not need to do any extra work. This patch also changes DH to use the new interface. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
189 lines
3.7 KiB
C
189 lines
3.7 KiB
C
/* 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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* 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, ¶ms) < 0)
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return -EINVAL;
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if (dh_set_params(ctx, ¶ms) < 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");
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