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fae198935c
A subsequent commit will introduce "dh" wrapping templates of the form "ffdhe2048(dh)", "ffdhe3072(dh)" and so on in order to provide built-in support for the well-known safe-prime ffdhe group parameters specified in RFC 7919. Those templates' ->set_secret() will wrap the inner "dh" implementation's ->set_secret() and set the ->p and ->g group parameters as appropriate on the way inwards. More specifically, - A ffdheXYZ(dh) user would call crypto_dh_encode() on a struct dh instance having ->p == ->g == NULL as well as ->p_size == ->g_size == 0 and pass the resulting buffer to the outer ->set_secret(). - This outer ->set_secret() would then decode the struct dh via crypto_dh_decode_key(), set ->p, ->g, ->p_size as well as ->g_size as appropriate for the group in question and encode the struct dh again before passing it further down to the inner "dh"'s ->set_secret(). The problem is that crypto_dh_decode_key() implements some basic checks which would reject parameter sets with ->p_size == 0 and thus, the ffdheXYZ templates' ->set_secret() cannot use it as-is for decoding the passed buffer. As the inner "dh"'s ->set_secret() will eventually conduct said checks on the final parameter set anyway, the outer ->set_secret() really only needs the decoding functionality. Split out the pure struct dh decoding part from crypto_dh_decode_key() into the new __crypto_dh_decode_key(). __crypto_dh_decode_key() gets defined in crypto/dh_helper.c, but will have to get called from crypto/dh.c and thus, its declaration must be somehow made available to the latter. Strictly speaking, __crypto_dh_decode_key() is internal to the dh_generic module, yet it would be a bit over the top to introduce a new header like e.g. include/crypto/internal/dh.h containing just a single prototype. Add the __crypto_dh_decode_key() declaration to include/crypto/dh.h instead. Provide a proper kernel-doc annotation, even though __crypto_dh_decode_key() is purposedly not on the function list specified in Documentation/crypto/api-kpp.rst. Signed-off-by: Nicolai Stange <nstange@suse.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
120 lines
3.2 KiB
C
120 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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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/kernel.h>
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#include <linux/export.h>
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#include <linux/err.h>
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#include <linux/string.h>
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#include <crypto/dh.h>
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#include <crypto/kpp.h>
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#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
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static inline u8 *dh_pack_data(u8 *dst, u8 *end, const void *src, size_t size)
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{
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if (!dst || size > end - dst)
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return NULL;
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memcpy(dst, src, size);
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return dst + size;
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}
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static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
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{
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memcpy(dst, src, size);
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return src + size;
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}
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static inline unsigned int dh_data_size(const struct dh *p)
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{
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return p->key_size + p->p_size + p->g_size;
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}
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unsigned int crypto_dh_key_len(const struct dh *p)
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{
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return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
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}
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EXPORT_SYMBOL_GPL(crypto_dh_key_len);
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int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
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{
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u8 *ptr = buf;
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u8 * const end = ptr + len;
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struct kpp_secret secret = {
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.type = CRYPTO_KPP_SECRET_TYPE_DH,
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.len = len
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};
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if (unlikely(!len))
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return -EINVAL;
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ptr = dh_pack_data(ptr, end, &secret, sizeof(secret));
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ptr = dh_pack_data(ptr, end, ¶ms->key_size,
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sizeof(params->key_size));
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ptr = dh_pack_data(ptr, end, ¶ms->p_size, sizeof(params->p_size));
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ptr = dh_pack_data(ptr, end, ¶ms->g_size, sizeof(params->g_size));
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ptr = dh_pack_data(ptr, end, params->key, params->key_size);
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ptr = dh_pack_data(ptr, end, params->p, params->p_size);
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ptr = dh_pack_data(ptr, end, params->g, params->g_size);
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if (ptr != end)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
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int __crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
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{
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const u8 *ptr = buf;
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struct kpp_secret secret;
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if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
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return -EINVAL;
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ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
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if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
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return -EINVAL;
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ptr = dh_unpack_data(¶ms->key_size, ptr, sizeof(params->key_size));
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ptr = dh_unpack_data(¶ms->p_size, ptr, sizeof(params->p_size));
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ptr = dh_unpack_data(¶ms->g_size, ptr, sizeof(params->g_size));
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if (secret.len != crypto_dh_key_len(params))
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return -EINVAL;
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/* Don't allocate memory. Set pointers to data within
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* the given buffer
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*/
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params->key = (void *)ptr;
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params->p = (void *)(ptr + params->key_size);
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params->g = (void *)(ptr + params->key_size + params->p_size);
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return 0;
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}
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int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
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{
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int err;
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err = __crypto_dh_decode_key(buf, len, params);
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if (err)
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return err;
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/*
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* Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
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* some drivers assume otherwise.
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*/
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if (params->key_size > params->p_size ||
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params->g_size > params->p_size)
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return -EINVAL;
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/*
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* Don't permit 'p' to be 0. It's not a prime number, and it's subject
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* to corner cases such as 'mod 0' being undefined or
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* crypto_kpp_maxsize() returning 0.
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*/
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if (memchr_inv(params->p, 0, params->p_size) == NULL)
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return -EINVAL;
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return 0;
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}
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EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
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