linux/crypto/dh_helper.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright (c) 2016, Intel Corporation
   4 * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
   5 */
   6#include <linux/kernel.h>
   7#include <linux/export.h>
   8#include <linux/err.h>
   9#include <linux/string.h>
  10#include <crypto/dh.h>
  11#include <crypto/kpp.h>
  12
  13#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
  14
  15static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
  16{
  17        if (!dst || size > end - dst)
  18                return NULL;
  19        memcpy(dst, src, size);
  20        return dst + size;
  21}
  22
  23static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
  24{
  25        memcpy(dst, src, size);
  26        return src + size;
  27}
  28
  29static inline unsigned int dh_data_size(const struct dh *p)
  30{
  31        return p->key_size + p->p_size + p->q_size + p->g_size;
  32}
  33
  34unsigned int crypto_dh_key_len(const struct dh *p)
  35{
  36        return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
  37}
  38EXPORT_SYMBOL_GPL(crypto_dh_key_len);
  39
  40int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
  41{
  42        u8 *ptr = buf;
  43        u8 * const end = ptr + len;
  44        struct kpp_secret secret = {
  45                .type = CRYPTO_KPP_SECRET_TYPE_DH,
  46                .len = len
  47        };
  48
  49        if (unlikely(!len))
  50                return -EINVAL;
  51
  52        ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
  53        ptr = dh_pack_data(ptr, end, &params->key_size,
  54                           sizeof(params->key_size));
  55        ptr = dh_pack_data(ptr, end, &params->p_size, sizeof(params->p_size));
  56        ptr = dh_pack_data(ptr, end, &params->q_size, sizeof(params->q_size));
  57        ptr = dh_pack_data(ptr, end, &params->g_size, sizeof(params->g_size));
  58        ptr = dh_pack_data(ptr, end, params->key, params->key_size);
  59        ptr = dh_pack_data(ptr, end, params->p, params->p_size);
  60        ptr = dh_pack_data(ptr, end, params->q, params->q_size);
  61        ptr = dh_pack_data(ptr, end, params->g, params->g_size);
  62        if (ptr != end)
  63                return -EINVAL;
  64        return 0;
  65}
  66EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
  67
  68int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
  69{
  70        const u8 *ptr = buf;
  71        struct kpp_secret secret;
  72
  73        if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
  74                return -EINVAL;
  75
  76        ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
  77        if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
  78                return -EINVAL;
  79
  80        ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
  81        ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
  82        ptr = dh_unpack_data(&params->q_size, ptr, sizeof(params->q_size));
  83        ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
  84        if (secret.len != crypto_dh_key_len(params))
  85                return -EINVAL;
  86
  87        /*
  88         * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
  89         * some drivers assume otherwise.
  90         */
  91        if (params->key_size > params->p_size ||
  92            params->g_size > params->p_size || params->q_size > params->p_size)
  93                return -EINVAL;
  94
  95        /* Don't allocate memory. Set pointers to data within
  96         * the given buffer
  97         */
  98        params->key = (void *)ptr;
  99        params->p = (void *)(ptr + params->key_size);
 100        params->q = (void *)(ptr + params->key_size + params->p_size);
 101        params->g = (void *)(ptr + params->key_size + params->p_size +
 102                             params->q_size);
 103
 104        /*
 105         * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
 106         * to corner cases such as 'mod 0' being undefined or
 107         * crypto_kpp_maxsize() returning 0.
 108         */
 109        if (memchr_inv(params->p, 0, params->p_size) == NULL)
 110                return -EINVAL;
 111
 112        /* It is permissible to not provide Q. */
 113        if (params->q_size == 0)
 114                params->q = NULL;
 115
 116        return 0;
 117}
 118EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
 119
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