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// SPDX-License-Identifier: MIT
/*
* This is an implementation of the HSS signature scheme from LMS
* This is designed to be full-featured
*
* Currently, this file consists of functions that don't have a better home
*/
#include <stdlib.h>
#include <string.h>
#include "common_defs.h"
#include "hss.h"
#include "hash.h"
#include "endian.h"
#include "hss_internal.h"
#include "hss_aux.h"
#include "hss_derive.h"
#include "config.h"
#include "lm_ots_common.h"
/*
* Allocate and load an ephemeral key
*/
struct hss_working_key *hss_load_private_key(
bool (*read_private_key)(unsigned char *private_key,
size_t len_private_key, void *context),
void *context,
size_t memory_target,
const unsigned char *aux_data, size_t len_aux_data,
struct hss_extra_info *info ) {
/* Step 1: determine the parameter set */
unsigned levels;
param_set_t lm[ MAX_HSS_LEVELS ];
param_set_t ots[ MAX_HSS_LEVELS ];
if (!hss_get_parameter_set( &levels, lm, ots, read_private_key, context)) {
/* Can't read private key, or private key invalid */
return 0;
}
/* Step 2: allocate the ephemeral key */
struct hss_working_key *w = allocate_working_key(levels, lm, ots,
memory_target, info);
if (!w) {
/* Memory allocation failure, most likely (we've already vetted */
/* the parameter sets) */
return 0;
}
/* Step 3: load the ephemeral key */
if (! hss_generate_working_key( read_private_key, context,
aux_data, len_aux_data, w, info )) {
/* About the only thing I can see failing here is perhaps */
/* attempting to reread the private key failed the second time; */
/* seems unlikely, but not impossible */
hss_free_working_key( w );
return 0;
}
/* Success! */
return w;
}
/*
* Internal function to generate the root seed and I value (based on the
* private seed). We do this (rather than select seed, I at random) so that
* we don't need to store it in our private key; we can recompute them
*/
bool hss_generate_root_seed_I_value(unsigned char *seed, unsigned char *I,
const unsigned char *master_seed) {
#if SECRET_METHOD == 2
/* In ACVP mode, we use the master seed as the source for both the */
/* root seed, and the root I value */
memcpy( seed, master_seed, SEED_LEN );
memcpy( I, master_seed + SEED_LEN, I_LEN );
#else
/*
* We use a two-level hashing scheme so that we end up using the master
* seed only twice throughout the system (once here, once to generate the
* aux hmac key)
*/
unsigned char hash_preimage[ TOPSEED_LEN ];
unsigned char hash_postimage[ MAX_HASH ];
memset( hash_preimage + TOPSEED_I, 0, I_LEN );
memset( hash_preimage + TOPSEED_Q, 0, 4 );
SET_D( hash_preimage + TOPSEED_D, D_TOPSEED );
hash_preimage[TOPSEED_WHICH] = 0x00;
memcpy( hash_preimage + TOPSEED_SEED, master_seed, SEED_LEN );
/* We use a fixed SHA256 hash; we don't care about interoperability */
/* so we don't need to worry about what parameter set the */
/* user specified */
#if I_LEN > 32 || SEED_LEN != 32
#error This logic needs to be reworked
#endif
union hash_context ctx;
hss_hash_ctx(hash_postimage, HASH_SHA256, &ctx, hash_preimage,
TOPSEED_LEN );
memcpy( hash_preimage + TOPSEED_SEED, hash_postimage, SEED_LEN );
/* Now compute the top level seed */
hash_preimage[TOPSEED_WHICH] = 0x01;
hss_hash_ctx(seed, HASH_SHA256, &ctx, hash_preimage, TOPSEED_LEN );
/* Now compute the top level I value */
hash_preimage[TOPSEED_WHICH] = 0x02;
hss_hash_ctx(hash_postimage, HASH_SHA256, &ctx, hash_preimage,
TOPSEED_LEN );
memcpy( I, hash_postimage, I_LEN );
hss_zeroize( hash_preimage, sizeof hash_preimage ); /* There's keying */
/* data here */
hss_zeroize( &ctx, sizeof ctx );
#endif
return true;
}
/*
* Internal function to generate the child I value (based on the parent's
* I value). While this needs to be determanistic (so that we can create the
* same I values between reboots), there's no requirement for interoperability.
* So we use a fixed SHA256; when we support a hash function other than SHA256,
* we needn't update this.
*/
bool hss_generate_child_seed_I_value( unsigned char *seed, unsigned char *I,
const unsigned char *parent_seed,
const unsigned char *parent_I,
merkle_index_t index,
param_set_t lm, param_set_t ots) {
struct seed_derive derive;
if (!hss_seed_derive_init( &derive, lm, ots, parent_I, parent_seed )) {
return false;
}
hss_seed_derive_set_q( &derive, index );
/* Compute the child seed value */
hss_seed_derive_set_j( &derive, SEED_CHILD_SEED );
hss_seed_derive( seed, &derive, true );
/* True sets the j value to SEED_CHILD_I */
/* Compute the child I value; with increment_j set to true in the */
/* above call, derive has been set to the SEED_CHILD_I position */
unsigned char postimage[ SEED_LEN ];
hss_seed_derive( postimage, &derive, false );
memcpy( I, postimage, I_LEN );
hss_seed_derive_done( &derive );
return true;
}
void hss_init_extra_info( struct hss_extra_info *p ) {
if (p) memset( p, 0, sizeof *p );
}
void hss_extra_info_set_threads( struct hss_extra_info *p, int num_threads ) {
if (p) p->num_threads = num_threads;
}
bool hss_extra_info_test_last_signature( struct hss_extra_info *p ) {
if (!p) return false;
return p->last_signature;
}
enum hss_error_code hss_extra_info_test_error_code( struct hss_extra_info *p ) {
if (!p) return hss_error_got_null;
return p->error_code;
}