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|
#include "hkdf.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <assert.h>
#include "axolotl_internal.h"
#define HASH_OUTPUT_SIZE 32
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
struct hkdf_context
{
axolotl_type_base base;
axolotl_context *global_context;
int iteration_start_offset;
};
int hkdf_create(hkdf_context **context, int message_version, axolotl_context *global_context)
{
assert(global_context);
*context = malloc(sizeof(hkdf_context));
if(!(*context)) {
return AX_ERR_NOMEM;
}
memset(*context, 0, sizeof(hkdf_context));
AXOLOTL_INIT(*context, hkdf_destroy);
(*context)->global_context = global_context;
if(message_version == 2) {
(*context)->iteration_start_offset = 0;
}
else if(message_version == 3) {
(*context)->iteration_start_offset = 1;
}
else {
free(*context);
return AX_ERR_INVAL;
}
return 0;
}
ssize_t hkdf_extract(hkdf_context *context,
uint8_t **output,
const uint8_t *salt, size_t salt_len,
const uint8_t *input_key_material, size_t input_key_material_len)
{
int result = 0;
axolotl_buffer *mac_buffer = 0;
uint8_t *mac = 0;
size_t mac_len = 0;
void *hmac_context;
assert(context);
result = axolotl_hmac_sha256_init(context->global_context,
&hmac_context, salt, salt_len);
if(result < 0) {
goto complete;
}
result = axolotl_hmac_sha256_update(context->global_context,
hmac_context, input_key_material, input_key_material_len);
if(result < 0) {
goto complete;
}
result = axolotl_hmac_sha256_final(context->global_context,
hmac_context, &mac_buffer);
if(result < 0) {
goto complete;
}
mac_len = axolotl_buffer_len(mac_buffer);
mac = malloc(mac_len);
if(!mac) {
result = AX_ERR_NOMEM;
goto complete;
}
memcpy(mac, axolotl_buffer_data(mac_buffer), mac_len);
complete:
axolotl_hmac_sha256_cleanup(context->global_context, hmac_context);
axolotl_buffer_free(mac_buffer);
if(result >= 0) {
*output = mac;
return (ssize_t)mac_len;
}
else {
return result;
}
}
ssize_t hkdf_expand(hkdf_context *context,
uint8_t **output,
const uint8_t *prk, size_t prk_len,
const uint8_t *info, size_t info_len,
size_t output_len)
{
int iterations = (int)ceil((double)output_len / (double)HASH_OUTPUT_SIZE);
size_t remaining_len = output_len;
axolotl_buffer *step_buffer = 0;
size_t step_size = 0;
uint8_t *result_buf = 0;
size_t result_buf_len = 0;
void *hmac_context = 0;
int result = 0;
uint8_t i;
assert(context);
for(i = context->iteration_start_offset; i < iterations + context->iteration_start_offset; i++) {
result = axolotl_hmac_sha256_init(context->global_context,
&hmac_context, prk, prk_len);
if(result < 0) {
goto complete;
}
if(step_buffer) {
result = axolotl_hmac_sha256_update(context->global_context,
hmac_context,
axolotl_buffer_data(step_buffer),
axolotl_buffer_len(step_buffer));
if(result < 0) {
goto complete;
}
axolotl_buffer_free(step_buffer);
step_buffer = 0;
}
if(info) {
result = axolotl_hmac_sha256_update(context->global_context,
hmac_context, info, info_len);
if(result < 0) {
goto complete;
}
}
result = axolotl_hmac_sha256_update(context->global_context,
hmac_context, &i, sizeof(uint8_t));
if(result < 0) {
goto complete;
}
result = axolotl_hmac_sha256_final(context->global_context,
hmac_context, &step_buffer);
if(result < 0) {
goto complete;
}
axolotl_hmac_sha256_cleanup(context->global_context, hmac_context);
hmac_context = 0;
step_size = MIN(remaining_len, axolotl_buffer_len(step_buffer));
if(!result_buf) {
result_buf = malloc(step_size);
if(!result_buf) {
result = AX_ERR_NOMEM;
goto complete;
}
memcpy(result_buf, axolotl_buffer_data(step_buffer), step_size);
result_buf_len = step_size;
}
else {
uint8_t *tmp_buf = realloc(result_buf, result_buf_len + step_size);
if(!tmp_buf) {
result = AX_ERR_NOMEM;
goto complete;
}
result_buf = tmp_buf;
memcpy(result_buf + result_buf_len, axolotl_buffer_data(step_buffer), step_size);
result_buf_len += step_size;
}
remaining_len -= step_size;
}
complete:
if(hmac_context) {
axolotl_hmac_sha256_cleanup(context->global_context, hmac_context);
}
axolotl_buffer_free(step_buffer);
if(result < 0) {
free(result_buf);
return result;
}
else {
*output = result_buf;
return (ssize_t)result_buf_len;
}
}
ssize_t hkdf_derive_secrets(hkdf_context *context,
uint8_t **output,
const uint8_t *input_key_material, size_t input_key_material_len,
const uint8_t *salt, size_t salt_len,
const uint8_t *info, size_t info_len,
size_t output_len)
{
ssize_t result = 0;
uint8_t *prk = 0;
ssize_t prk_len = 0;
assert(context);
prk_len = hkdf_extract(context, &prk, salt, salt_len, input_key_material, input_key_material_len);
if(prk_len < 0) {
axolotl_log(context->global_context, AX_LOG_ERROR, "hkdf_extract error: %d", prk_len);
return prk_len;
}
result = hkdf_expand(context, output, prk, (size_t)prk_len, info, info_len, output_len);
if(prk) {
free(prk);
}
return result;
}
int hkdf_compare(const hkdf_context *context1, const hkdf_context *context2)
{
if(context1 == context2) {
return 0;
}
else if(context1 == 0 && context2 != 0) {
return -1;
}
else if(context1 != 0 && context2 == 0) {
return 1;
}
else if(context1->iteration_start_offset < context2->iteration_start_offset) {
return -1;
}
else if(context1->iteration_start_offset > context2->iteration_start_offset) {
return 1;
}
else {
return 0;
}
}
void hkdf_destroy(axolotl_type_base *type)
{
hkdf_context *context = (hkdf_context *)type;
free(context);
}
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