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esp-idf/components/protocomm/src/security/security1.c
Piyush Shah 541cf16c9e protocomm security1: Restart security session if SESSION_STATE_CMD0 is received 
With the introduction of cookies to track a session, it is possible that the
clients restart the provisioning on the same session, specifically when a user
cancels a current provisioning attempt. This can result in an error as the state
on the device side and client side will go out of sync.

This has now been changed such that if SESSION_STATE_CMD0 is received on
an existing session, the state is reset and flow allowed to continue.
2021-01-13 04:34:10 +00:00

588 lines
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// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <esp_err.h>
#include <esp_log.h>
#include <mbedtls/aes.h>
#include <mbedtls/sha256.h>
#include <mbedtls/entropy.h>
#include <mbedtls/ctr_drbg.h>
#include <mbedtls/ecdh.h>
#include <mbedtls/error.h>
#include <mbedtls/ssl_internal.h>
#include <protocomm_security.h>
#include <protocomm_security1.h>
#include "session.pb-c.h"
#include "sec1.pb-c.h"
#include "constants.pb-c.h"
static const char* TAG = "security1";
#define PUBLIC_KEY_LEN 32
#define SZ_RANDOM 16
#define SESSION_STATE_CMD0 0 /* Session is not setup */
#define SESSION_STATE_CMD1 1 /* Session is not setup */
#define SESSION_STATE_DONE 2 /* Session setup successful */
typedef struct session {
/* Session data */
uint32_t id;
uint8_t state;
uint8_t device_pubkey[PUBLIC_KEY_LEN];
uint8_t client_pubkey[PUBLIC_KEY_LEN];
uint8_t sym_key[PUBLIC_KEY_LEN];
uint8_t rand[SZ_RANDOM];
/* mbedtls context data for AES */
mbedtls_aes_context ctx_aes;
unsigned char stb[16];
size_t nc_off;
} session_t;
static void flip_endian(uint8_t *data, size_t len)
{
uint8_t swp_buf;
for (int i = 0; i < len/2; i++) {
swp_buf = data[i];
data[i] = data[len - i - 1];
data[len - i - 1] = swp_buf;
}
}
static void hexdump(const char *msg, uint8_t *buf, int len)
{
ESP_LOGD(TAG, "%s:", msg);
ESP_LOG_BUFFER_HEX_LEVEL(TAG, buf, len, ESP_LOG_DEBUG);
}
static esp_err_t handle_session_command1(session_t *cur_session,
uint32_t session_id,
SessionData *req, SessionData *resp)
{
ESP_LOGD(TAG, "Request to handle setup1_command");
Sec1Payload *in = (Sec1Payload *) req->sec1;
uint8_t check_buf[PUBLIC_KEY_LEN];
int mbed_err;
if (cur_session->state != SESSION_STATE_CMD1) {
ESP_LOGE(TAG, "Invalid state of session %d (expected %d)", SESSION_STATE_CMD1, cur_session->state);
return ESP_ERR_INVALID_STATE;
}
/* Initialize crypto context */
mbedtls_aes_init(&cur_session->ctx_aes);
memset(cur_session->stb, 0, sizeof(cur_session->stb));
cur_session->nc_off = 0;
hexdump("Client verifier", in->sc1->client_verify_data.data,
in->sc1->client_verify_data.len);
mbed_err = mbedtls_aes_setkey_enc(&cur_session->ctx_aes, cur_session->sym_key,
sizeof(cur_session->sym_key)*8);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failure at mbedtls_aes_setkey_enc with error code : -0x%x", -mbed_err);
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_FAIL;
}
mbed_err = mbedtls_aes_crypt_ctr(&cur_session->ctx_aes,
PUBLIC_KEY_LEN, &cur_session->nc_off,
cur_session->rand, cur_session->stb,
in->sc1->client_verify_data.data, check_buf);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failure at mbedtls_aes_crypt_ctr with error code : -0x%x", -mbed_err);
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_FAIL;
}
hexdump("Dec Client verifier", check_buf, sizeof(check_buf));
/* constant time memcmp */
if (mbedtls_ssl_safer_memcmp(check_buf, cur_session->device_pubkey,
sizeof(cur_session->device_pubkey)) != 0) {
ESP_LOGE(TAG, "Key mismatch. Close connection");
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_FAIL;
}
Sec1Payload *out = (Sec1Payload *) malloc(sizeof(Sec1Payload));
SessionResp1 *out_resp = (SessionResp1 *) malloc(sizeof(SessionResp1));
if (!out || !out_resp) {
ESP_LOGE(TAG, "Error allocating memory for response1");
free(out);
free(out_resp);
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_ERR_NO_MEM;
}
sec1_payload__init(out);
session_resp1__init(out_resp);
out_resp->status = STATUS__Success;
uint8_t *outbuf = (uint8_t *) malloc(PUBLIC_KEY_LEN);
if (!outbuf) {
ESP_LOGE(TAG, "Error allocating ciphertext buffer");
free(out);
free(out_resp);
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_ERR_NO_MEM;
}
mbed_err = mbedtls_aes_crypt_ctr(&cur_session->ctx_aes,
PUBLIC_KEY_LEN, &cur_session->nc_off,
cur_session->rand, cur_session->stb,
cur_session->client_pubkey, outbuf);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failure at mbedtls_aes_crypt_ctr with error code : -0x%x", -mbed_err);
free(outbuf);
free(out);
free(out_resp);
mbedtls_aes_free(&cur_session->ctx_aes);
return ESP_FAIL;
}
out_resp->device_verify_data.data = outbuf;
out_resp->device_verify_data.len = PUBLIC_KEY_LEN;
hexdump("Device verify data", outbuf, PUBLIC_KEY_LEN);
out->msg = SEC1_MSG_TYPE__Session_Response1;
out->payload_case = SEC1_PAYLOAD__PAYLOAD_SR1;
out->sr1 = out_resp;
resp->proto_case = SESSION_DATA__PROTO_SEC1;
resp->sec1 = out;
cur_session->state = SESSION_STATE_DONE;
ESP_LOGD(TAG, "Secure session established successfully");
return ESP_OK;
}
static esp_err_t sec1_new_session(protocomm_security_handle_t handle, uint32_t session_id);
static esp_err_t handle_session_command0(session_t *cur_session,
uint32_t session_id,
SessionData *req, SessionData *resp,
const protocomm_security_pop_t *pop)
{
ESP_LOGD(TAG, "Request to handle setup0_command");
Sec1Payload *in = (Sec1Payload *) req->sec1;
esp_err_t ret;
int mbed_err;
if (cur_session->state != SESSION_STATE_CMD0) {
ESP_LOGW(TAG, "Invalid state of session %d (expected %d). Restarting session.",
SESSION_STATE_CMD0, cur_session->state);
sec1_new_session(cur_session, session_id);
}
if (in->sc0->client_pubkey.len != PUBLIC_KEY_LEN) {
ESP_LOGE(TAG, "Invalid public key length");
return ESP_ERR_INVALID_ARG;
}
mbedtls_ecdh_context *ctx_server = malloc(sizeof(mbedtls_ecdh_context));
mbedtls_entropy_context *entropy = malloc(sizeof(mbedtls_entropy_context));
mbedtls_ctr_drbg_context *ctr_drbg = malloc(sizeof(mbedtls_ctr_drbg_context));
if (!ctx_server || !entropy || !ctr_drbg) {
ESP_LOGE(TAG, "Failed to allocate memory for mbedtls context");
free(ctx_server);
free(entropy);
free(ctr_drbg);
return ESP_ERR_NO_MEM;
}
mbedtls_ecdh_init(ctx_server);
mbedtls_ctr_drbg_init(ctr_drbg);
mbedtls_entropy_init(entropy);
mbed_err = mbedtls_ctr_drbg_seed(ctr_drbg, mbedtls_entropy_func,
entropy, NULL, 0);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_ctr_drbg_seed with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
mbed_err = mbedtls_ecp_group_load(&ctx_server->grp, MBEDTLS_ECP_DP_CURVE25519);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_ecp_group_load with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
mbed_err = mbedtls_ecdh_gen_public(&ctx_server->grp, &ctx_server->d, &ctx_server->Q,
mbedtls_ctr_drbg_random, ctr_drbg);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_ecdh_gen_public with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
mbed_err = mbedtls_mpi_write_binary(&ctx_server->Q.X,
cur_session->device_pubkey,
PUBLIC_KEY_LEN);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_mpi_write_binary with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
flip_endian(cur_session->device_pubkey, PUBLIC_KEY_LEN);
memcpy(cur_session->client_pubkey, in->sc0->client_pubkey.data, PUBLIC_KEY_LEN);
uint8_t *dev_pubkey = cur_session->device_pubkey;
uint8_t *cli_pubkey = cur_session->client_pubkey;
hexdump("Device pubkey", dev_pubkey, PUBLIC_KEY_LEN);
hexdump("Client pubkey", cli_pubkey, PUBLIC_KEY_LEN);
mbed_err = mbedtls_mpi_lset(&ctx_server->Qp.Z, 1);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_mpi_lset with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
flip_endian(cur_session->client_pubkey, PUBLIC_KEY_LEN);
mbed_err = mbedtls_mpi_read_binary(&ctx_server->Qp.X, cli_pubkey, PUBLIC_KEY_LEN);
flip_endian(cur_session->client_pubkey, PUBLIC_KEY_LEN);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_mpi_read_binary with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
mbed_err = mbedtls_ecdh_compute_shared(&ctx_server->grp, &ctx_server->z, &ctx_server->Qp,
&ctx_server->d, mbedtls_ctr_drbg_random, ctr_drbg);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_ecdh_compute_shared with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
mbed_err = mbedtls_mpi_write_binary(&ctx_server->z, cur_session->sym_key, PUBLIC_KEY_LEN);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_mpi_write_binary with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
flip_endian(cur_session->sym_key, PUBLIC_KEY_LEN);
if (pop != NULL && pop->data != NULL && pop->len != 0) {
ESP_LOGD(TAG, "Adding proof of possession");
uint8_t sha_out[PUBLIC_KEY_LEN];
mbed_err = mbedtls_sha256_ret((const unsigned char *) pop->data, pop->len, sha_out, 0);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_sha256_ret with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
for (int i = 0; i < PUBLIC_KEY_LEN; i++) {
cur_session->sym_key[i] ^= sha_out[i];
}
}
hexdump("Shared key", cur_session->sym_key, PUBLIC_KEY_LEN);
mbed_err = mbedtls_ctr_drbg_random(ctr_drbg, cur_session->rand, SZ_RANDOM);
if (mbed_err != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_ctr_drbg_random with error code : -0x%x", -mbed_err);
ret = ESP_FAIL;
goto exit_cmd0;
}
hexdump("Device random", cur_session->rand, SZ_RANDOM);
Sec1Payload *out = (Sec1Payload *) malloc(sizeof(Sec1Payload));
SessionResp0 *out_resp = (SessionResp0 *) malloc(sizeof(SessionResp0));
if (!out || !out_resp) {
ESP_LOGE(TAG, "Error allocating memory for response0");
ret = ESP_ERR_NO_MEM;
free(out);
free(out_resp);
goto exit_cmd0;
}
sec1_payload__init(out);
session_resp0__init(out_resp);
out_resp->status = STATUS__Success;
out_resp->device_pubkey.data = dev_pubkey;
out_resp->device_pubkey.len = PUBLIC_KEY_LEN;
out_resp->device_random.data = (uint8_t *) cur_session->rand;
out_resp->device_random.len = SZ_RANDOM;
out->msg = SEC1_MSG_TYPE__Session_Response0;
out->payload_case = SEC1_PAYLOAD__PAYLOAD_SR0;
out->sr0 = out_resp;
resp->proto_case = SESSION_DATA__PROTO_SEC1;
resp->sec1 = out;
cur_session->state = SESSION_STATE_CMD1;
ESP_LOGD(TAG, "Session setup phase1 done");
ret = ESP_OK;
exit_cmd0:
mbedtls_ecdh_free(ctx_server);
free(ctx_server);
mbedtls_ctr_drbg_free(ctr_drbg);
free(ctr_drbg);
mbedtls_entropy_free(entropy);
free(entropy);
return ret;
}
static esp_err_t sec1_session_setup(session_t *cur_session,
uint32_t session_id,
SessionData *req, SessionData *resp,
const protocomm_security_pop_t *pop)
{
Sec1Payload *in = (Sec1Payload *) req->sec1;
esp_err_t ret;
if (!in) {
ESP_LOGE(TAG, "Empty session data");
return ESP_ERR_INVALID_ARG;
}
switch (in->msg) {
case SEC1_MSG_TYPE__Session_Command0:
ret = handle_session_command0(cur_session, session_id, req, resp, pop);
break;
case SEC1_MSG_TYPE__Session_Command1:
ret = handle_session_command1(cur_session, session_id, req, resp);
break;
default:
ESP_LOGE(TAG, "Invalid security message type");
ret = ESP_ERR_INVALID_ARG;
}
return ret;
}
static void sec1_session_setup_cleanup(session_t *cur_session, uint32_t session_id, SessionData *resp)
{
Sec1Payload *out = resp->sec1;
if (!out) {
return;
}
switch (out->msg) {
case SEC1_MSG_TYPE__Session_Response0:
{
SessionResp0 *out_resp0 = out->sr0;
if (out_resp0) {
free(out_resp0);
}
break;
}
case SEC1_MSG_TYPE__Session_Response1:
{
SessionResp1 *out_resp1 = out->sr1;
if (out_resp1) {
free(out_resp1->device_verify_data.data);
free(out_resp1);
}
break;
}
default:
break;
}
free(out);
return;
}
static esp_err_t sec1_close_session(protocomm_security_handle_t handle, uint32_t session_id)
{
session_t *cur_session = (session_t *) handle;
if (!cur_session) {
return ESP_ERR_INVALID_ARG;
}
if (!cur_session || cur_session->id != session_id) {
ESP_LOGE(TAG, "Attempt to close invalid session");
return ESP_ERR_INVALID_STATE;
}
if (cur_session->state == SESSION_STATE_DONE) {
/* Free AES context data */
mbedtls_aes_free(&cur_session->ctx_aes);
}
memset(cur_session, 0, sizeof(session_t));
cur_session->id = -1;
return ESP_OK;
}
static esp_err_t sec1_new_session(protocomm_security_handle_t handle, uint32_t session_id)
{
session_t *cur_session = (session_t *) handle;
if (!cur_session) {
return ESP_ERR_INVALID_ARG;
}
if (cur_session->id != -1) {
/* Only one session is allowed at a time */
ESP_LOGE(TAG, "Closing old session with id %u", cur_session->id);
sec1_close_session(cur_session, session_id);
}
cur_session->id = session_id;
return ESP_OK;
}
static esp_err_t sec1_init(protocomm_security_handle_t *handle)
{
if (!handle) {
return ESP_ERR_INVALID_ARG;
}
session_t *cur_session = (session_t *) calloc(1, sizeof(session_t));
if (!cur_session) {
ESP_LOGE(TAG, "Error allocating new session");
return ESP_ERR_NO_MEM;
}
cur_session->id = -1;
*handle = (protocomm_security_handle_t) cur_session;
return ESP_OK;
}
static esp_err_t sec1_cleanup(protocomm_security_handle_t handle)
{
session_t *cur_session = (session_t *) handle;
if (cur_session) {
sec1_close_session(handle, cur_session->id);
}
free(handle);
return ESP_OK;
}
static esp_err_t sec1_decrypt(protocomm_security_handle_t handle,
uint32_t session_id,
const uint8_t *inbuf, ssize_t inlen,
uint8_t *outbuf, ssize_t *outlen)
{
session_t *cur_session = (session_t *) handle;
if (!cur_session) {
return ESP_ERR_INVALID_ARG;
}
if (*outlen < inlen) {
return ESP_ERR_INVALID_ARG;
}
if (!cur_session || cur_session->id != session_id) {
ESP_LOGE(TAG, "Session with ID %d not found", session_id);
return ESP_ERR_INVALID_STATE;
}
if (cur_session->state != SESSION_STATE_DONE) {
ESP_LOGE(TAG, "Secure session not established");
return ESP_ERR_INVALID_STATE;
}
*outlen = inlen;
int ret = mbedtls_aes_crypt_ctr(&cur_session->ctx_aes, inlen, &cur_session->nc_off,
cur_session->rand, cur_session->stb, inbuf, outbuf);
if (ret != 0) {
ESP_LOGE(TAG, "Failed at mbedtls_aes_crypt_ctr with error code : %d", ret);
return ESP_FAIL;
}
return ESP_OK;
}
static esp_err_t sec1_req_handler(protocomm_security_handle_t handle,
const protocomm_security_pop_t *pop,
uint32_t session_id,
const uint8_t *inbuf, ssize_t inlen,
uint8_t **outbuf, ssize_t *outlen,
void *priv_data)
{
session_t *cur_session = (session_t *) handle;
if (!cur_session) {
ESP_LOGE(TAG, "Invalid session context data");
return ESP_ERR_INVALID_ARG;
}
if (session_id != cur_session->id) {
ESP_LOGE(TAG, "Invalid session ID : %d (expected %d)", session_id, cur_session->id);
return ESP_ERR_INVALID_STATE;
}
SessionData *req;
SessionData resp;
esp_err_t ret;
req = session_data__unpack(NULL, inlen, inbuf);
if (!req) {
ESP_LOGE(TAG, "Unable to unpack setup_req");
return ESP_ERR_INVALID_ARG;
}
if (req->sec_ver != protocomm_security1.ver) {
ESP_LOGE(TAG, "Security version mismatch. Closing connection");
session_data__free_unpacked(req, NULL);
return ESP_ERR_INVALID_ARG;
}
session_data__init(&resp);
ret = sec1_session_setup(cur_session, session_id, req, &resp, pop);
if (ret != ESP_OK) {
ESP_LOGE(TAG, "Session setup error %d", ret);
session_data__free_unpacked(req, NULL);
return ESP_FAIL;
}
resp.sec_ver = req->sec_ver;
session_data__free_unpacked(req, NULL);
*outlen = session_data__get_packed_size(&resp);
*outbuf = (uint8_t *) malloc(*outlen);
if (!*outbuf) {
ESP_LOGE(TAG, "System out of memory");
return ESP_ERR_NO_MEM;
}
session_data__pack(&resp, *outbuf);
sec1_session_setup_cleanup(cur_session, session_id, &resp);
return ESP_OK;
}
const protocomm_security_t protocomm_security1 = {
.ver = 1,
.init = sec1_init,
.cleanup = sec1_cleanup,
.new_transport_session = sec1_new_session,
.close_transport_session = sec1_close_session,
.security_req_handler = sec1_req_handler,
.encrypt = sec1_decrypt, /* Encrypt == decrypt for AES-CTR */
.decrypt = sec1_decrypt,
};
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