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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2025-present Eclipse ThreadX Contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Crypto Component */
/** */
/** Diffie-Hellman (DH) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_CRYPTO_SOURCE_CODE
/* Include necessary system files. */
#include "nx_crypto_dh.h"
#ifndef NX_CRYPTO_SELF_TEST
/* The Diffie-Hellman group 2 modulus. */
/* Modulus, in byte stream, be */
/* ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f24117c4b1fe649286651ece65381ffffffffffffffff */
static const HN_UBASE _nx_dh_group_2_modulus[] =
{
HN_ULONG_TO_UBASE(0xFFFFFFFF), HN_ULONG_TO_UBASE(0xFFFFFFFF),
HN_ULONG_TO_UBASE(0xECE65381), HN_ULONG_TO_UBASE(0x49286651),
HN_ULONG_TO_UBASE(0x7C4B1FE6), HN_ULONG_TO_UBASE(0xAE9F2411),
HN_ULONG_TO_UBASE(0x5A899FA5), HN_ULONG_TO_UBASE(0xEE386BFB),
HN_ULONG_TO_UBASE(0xF406B7ED), HN_ULONG_TO_UBASE(0x0BFF5CB6),
HN_ULONG_TO_UBASE(0xA637ED6B), HN_ULONG_TO_UBASE(0xF44C42E9),
HN_ULONG_TO_UBASE(0x625E7EC6), HN_ULONG_TO_UBASE(0xE485B576),
HN_ULONG_TO_UBASE(0x6D51C245), HN_ULONG_TO_UBASE(0x4FE1356D),
HN_ULONG_TO_UBASE(0xF25F1437), HN_ULONG_TO_UBASE(0x302B0A6D),
HN_ULONG_TO_UBASE(0xCD3A431B), HN_ULONG_TO_UBASE(0xEF9519B3),
HN_ULONG_TO_UBASE(0x8E3404DD), HN_ULONG_TO_UBASE(0x514A0879),
HN_ULONG_TO_UBASE(0x3B139B22), HN_ULONG_TO_UBASE(0x020BBEA6),
HN_ULONG_TO_UBASE(0x8A67CC74), HN_ULONG_TO_UBASE(0x29024E08),
HN_ULONG_TO_UBASE(0x80DC1CD1), HN_ULONG_TO_UBASE(0xC4C6628B),
HN_ULONG_TO_UBASE(0x2168C234), HN_ULONG_TO_UBASE(0xC90FDAA2),
HN_ULONG_TO_UBASE(0xFFFFFFFF), HN_ULONG_TO_UBASE(0xFFFFFFFF)
};
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_crypto_dh_setup PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function sets up a Diffie-Hellman context by generating a */
/* local. */
/* */
/* Note: The scratch buffer must be able to hold a number of *bytes* */
/* at least equal to NX_CRYPTO_DIFFIE_HELLMAN_SCRATCH_SIZE. */
/* */
/* INPUT */
/* */
/* dh_ptr Diffie-Hellman context */
/* local_public_key Pointer to local public key */
/* local_public_key_len Local public key length */
/* dh_group_num Chosen DH group number */
/* scratch_buf_ptr Pointer to scratch buffer, */
/* which cannot be smaller */
/* than 6 times of the key */
/* size (in bytes). This */
/* scratch buffer can be */
/* reused after this function */
/* returns. */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_crypto_huge_number_adjust_size Adjust the size of a huge */
/* number to remove leading */
/* zeroes */
/* _nx_crypto_huge_number_mont_power_modulus */
/* Raise a huge number for */
/* montgomery reduction */
/* */
/* CALLED BY */
/* */
/* Application Code */
/* */
/**************************************************************************/
NX_CRYPTO_KEEP UINT _nx_crypto_dh_setup(NX_CRYPTO_DH *dh_ptr,
UCHAR *local_public_key_ptr,
UINT *local_public_key_len_ptr,
ULONG dh_group_num,
HN_UBASE *scratch_buf_ptr)
{
UINT i;
/* Actual huge numbers used in calculations */
NX_CRYPTO_HUGE_NUMBER modulus, public_key, private_key, generator;
HN_UBASE generator_value;
NX_CRYPTO_STATE_CHECK
/* Assign the desired key size based on the chosen Diffie-Hellman group. */
switch (dh_group_num)
{
case NX_CRYPTO_DH_GROUP_2:
dh_ptr -> nx_crypto_dh_key_size = NX_CRYPTO_DIFFIE_HELLMAN_GROUP_2_KEY_SIZE;
dh_ptr -> nx_crypto_dh_modulus = (HN_UBASE *)_nx_dh_group_2_modulus;
NX_CRYPTO_HUGE_NUMBER_INITIALIZE_DIGIT(&generator, &generator_value,
NX_CRYPTO_DH_GROUP_2_GENERATOR)
/* Setup the modulus value. */
modulus.nx_crypto_huge_number_data = dh_ptr -> nx_crypto_dh_modulus;
modulus.nx_crypto_huge_number_size = dh_ptr -> nx_crypto_dh_key_size >> HN_SIZE_SHIFT;
modulus.nx_crypto_huge_buffer_size = dh_ptr -> nx_crypto_dh_key_size;
modulus.nx_crypto_huge_number_is_negative = NX_CRYPTO_FALSE;
break;
default:
/* No supported group specified - error! */
return(NX_CRYPTO_NOT_SUCCESSFUL);
}
/* Local pointer for pointer arithmetic. The power-modulus operation does not require the scratch area
to be "clean". Therefore no need to zero out the buffer.
Public key buffer (and scratch). */
NX_CRYPTO_HUGE_NUMBER_INITIALIZE(&public_key, scratch_buf_ptr, dh_ptr -> nx_crypto_dh_key_size << 1);
/* Private key buffer - note that no scratch is required for the private key. */
private_key.nx_crypto_huge_number_data = dh_ptr -> nx_crypto_dh_private_key_buffer;
private_key.nx_crypto_huge_number_size = dh_ptr -> nx_crypto_dh_key_size >> HN_SIZE_SHIFT;
private_key.nx_crypto_huge_buffer_size = sizeof(dh_ptr -> nx_crypto_dh_private_key_buffer);
private_key.nx_crypto_huge_number_is_negative = NX_CRYPTO_FALSE;
/* Generate the private key. */
for (i = 0; i < private_key.nx_crypto_huge_number_size; i++)
{
/* Grab a random value - this may be more than one byte and we want to use
all the bytes in the value, so we do not simply copy the random_value
into the buffers. */
dh_ptr -> nx_crypto_dh_private_key_buffer[i] = (HN_UBASE)((HN_UBASE)(NX_CRYPTO_RAND()) & HN_MASK);
}
/* Finally, generate the public key from the private key, modulus, and the generator.
The actual calculation is "public_key = (generator**private_key) % modulus"
where the "**" denotes exponentiation. */
_nx_crypto_huge_number_mont_power_modulus(&generator, &private_key,
&modulus, &public_key, scratch_buf_ptr);
/* Copy the public key into the return buffer. */
_nx_crypto_huge_number_extract(&public_key, local_public_key_ptr,
dh_ptr -> nx_crypto_dh_key_size, local_public_key_len_ptr);
return(NX_CRYPTO_SUCCESS);
}
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_crypto_dh_compute_secret PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function computes the Diffie-Hellman shared secret using an */
/* existing Diffie-Hellman context and a public key received from a */
/* remote entity, usually as part of an IPSEC or SSL key exchange. */
/* */
/* Note: The scratch buffer must be able to hold a number of *bytes* */
/* at least equal to NX_CRYPTO_DIFFIE_HELLMAN_SCRATCH_SIZE. */
/* */
/* INPUT */
/* */
/* dh_ptr Diffie-Hellman context */
/* share_secret_key_ptr Shared secret buffer pointer */
/* share_secret_key_len_ptr Length of shared secret */
/* remote_public_key Pointer to remote public key */
/* remote_public_key_len Remote public key length */
/* scratch_buf_ptr Pointer to scratch buffer, */
/* which cannot be smaller */
/* than 8 times of the key */
/* size (in bytes). This */
/* scratch buffer can be */
/* reused after this function */
/* returns. */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_crypto_huge_number_extract Extract huge number */
/* _nx_crypto_huge_number_setup Setup huge number */
/* _nx_crypto_huge_number_mont_power_modulus */
/* Raise a huge number for */
/* montgomery reduction */
/* */
/* CALLED BY */
/* */
/* Application Code */
/* */
/**************************************************************************/
NX_CRYPTO_KEEP UINT _nx_crypto_dh_compute_secret(NX_CRYPTO_DH *dh_ptr,
UCHAR *share_secret_key_ptr,
ULONG *share_secret_key_len_ptr,
UCHAR *remote_public_key,
ULONG remote_public_key_len,
HN_UBASE *scratch_buf_ptr)
{
UINT key_size;
/* Actual huge numbers used in calculations */
NX_CRYPTO_HUGE_NUMBER modulus, public_key, private_key, shared_secret;
NX_CRYPTO_STATE_CHECK
/* Make sure the key size was assigned before we do anything else. Generally, this means
_nx_crypto_dh_setup was not called to set up the NX_DH structure prior to this call. */
if (0 == dh_ptr -> nx_crypto_dh_key_size)
{
return(NX_CRYPTO_NOT_SUCCESSFUL);
}
/* Make sure the remote public key is small enough to fit into the huge number buffer. */
if (remote_public_key_len > dh_ptr -> nx_crypto_dh_key_size)
{
return(NX_CRYPTO_NOT_SUCCESSFUL);
}
/* Figure out the sizes of our keys and buffers. We need 2X the key size for our buffer space. */
key_size = dh_ptr -> nx_crypto_dh_key_size;
NX_CRYPTO_HUGE_NUMBER_INITIALIZE(&public_key, scratch_buf_ptr, key_size);
NX_CRYPTO_HUGE_NUMBER_INITIALIZE(&shared_secret, scratch_buf_ptr, key_size << 1);
/* Copy the remote public key from the caller's buffer. */
_nx_crypto_huge_number_setup(&public_key, remote_public_key, remote_public_key_len);
/* Set up each of the buffers - point into the scratch buffer at increments of the DH buffer size. */
modulus.nx_crypto_huge_number_data = (HN_UBASE *)dh_ptr -> nx_crypto_dh_modulus;
modulus.nx_crypto_huge_number_size = key_size >> HN_SIZE_SHIFT;
modulus.nx_crypto_huge_buffer_size = key_size;
modulus.nx_crypto_huge_number_is_negative = NX_CRYPTO_FALSE;
/* Private key buffer - note that no scratch is required for the private key, but we set it in case
it is needed in the future. */
private_key.nx_crypto_huge_number_data = (HN_UBASE *)dh_ptr -> nx_crypto_dh_private_key_buffer;
private_key.nx_crypto_huge_number_size = key_size >> HN_SIZE_SHIFT;
private_key.nx_crypto_huge_buffer_size = key_size;
private_key.nx_crypto_huge_number_is_negative = NX_CRYPTO_FALSE;
/* Finally, generate shared secret from the remote public key, our generated private key, and the modulus, modulus.
The actual calculation is "shared_secret = (public_key**private_key) % modulus"
where the "**" denotes exponentiation. */
_nx_crypto_huge_number_mont_power_modulus(&public_key, &private_key, &modulus,
&shared_secret, scratch_buf_ptr);
/* Now we have a shared secret to return to the caller. Check to make sure the buffer is large enough to hold the public key. */
if (*share_secret_key_len_ptr < key_size)
{
return(NX_CRYPTO_NOT_SUCCESSFUL);
}
/* The public key size is simply the key size for this group. */
/* Copy the shared secret into the return buffer. */
_nx_crypto_huge_number_extract(&shared_secret, share_secret_key_ptr,
key_size, (UINT *)share_secret_key_len_ptr);
return(NX_CRYPTO_SUCCESS);
}
#endif
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