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Integrated CRC checks and integrity error handling #26

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fdda564
Integrated CRC checks and integrity error handling
smallfoot47 Mar 12, 2025
0b4d96a
Check.h hotfix #1
smallfoot47 Mar 12, 2025
ed8f2df
checker.h hotfix #2
smallfoot47 Mar 12, 2025
a0333e6
decoder.c hotfix #1
smallfoot47 Mar 12, 2025
adf79cb
check.h hotfix #3
smallfoot47 Mar 12, 2025
74abc84
decoder.c hotfix #2
smallfoot47 Mar 12, 2025
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6 changes: 3 additions & 3 deletions decoder/inc/check.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@

/***** Classes *****/

CRC_RESULTS[CHANNELS];
uint32_t CRC_RESULTS[CHANNELS];

void CHECKER_INIT() {
MXC_CRC_Init();
Expand All @@ -44,11 +44,11 @@ const uint32_t CRC_COMPUTE(uint32_t* memory) {
}

void CHECKER_REMEMBER_CHANNEL(uint32_t* channel_location) {
m_crc_results[(memory / CHANNEL_SIZE) % CHANNELS] = CRC_COMPUTE(memory);
CRC_RESULTS[((uint32_t)channel_location / CHANNEL_SIZE) % CHANNELS] = CRC_COMPUTE(channel_location);
}

const bool CHECKER_VERIFY_CHANNEL(uint32_t* channel_location) {
return CRC_COMPUTE(memory) == m_crc_results[(memory / CHANNEL_SIZE) % CHANNELS];
return CRC_COMPUTE(channel_location) == CRC_RESULTS[((uint32_t)channel_location / CHANNEL_SIZE) % CHANNELS];
}

void CHECKER_END() {
Expand Down
97 changes: 59 additions & 38 deletions decoder/src/decoder.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
#include "simple_crypto.h"
#include "secrets.h"
#include "random_w.h"
#include "check.h"

/**********************************************************
******************* PRIMITIVE TYPES **********************
Expand Down Expand Up @@ -134,17 +135,28 @@ mxc_tmr_cfg_t tmr;
* @param channel The channel number to be checked.
* @return 1 if the the decoder is subscribed to the channel. 0 if not.
*/
int integrity_failure() {
STATUS_LED_RED();
print_error("Integrity failure!");
return -1;
}

int is_subscribed(channel_id_t channel, timestamp_t timestamp) {
// Check if this is an emergency broadcast message
if (channel == EMERGENCY_CHANNEL) {
return 1;
}
// Check if the decoder has has a subscription
for (int i = 0; i < MAX_CHANNEL_COUNT; i++) {
if (decoder_status.subscribed_channels[i].id == channel && decoder_status.subscribed_channels[i].active && timestamp >= decoder_status.subscribed_channels[i].start_timestamp && timestamp <= decoder_status.subscribed_channels[i].end_timestamp) {

if (channel == EMERGENCY_CHANNEL) {
return 1;
}
}
// Check if the decoder has has a subscription
for (int i = 0; i < MAX_CHANNEL_COUNT; i++) {
if (CHECKER_VERIFY_CHANNEL((uint32_t*)&decoder_status.subscribed_channels[i])) {
if (decoder_status.subscribed_channels[i].id == channel && decoder_status.subscribed_channels[i].active && timestamp >= decoder_status.subscribed_channels[i].start_timestamp && timestamp <= decoder_status.subscribed_channels[i].end_timestamp) {
return 1;
}
}
else
return integrity_failure();
}
return 0;
}

Expand Down Expand Up @@ -206,12 +218,15 @@ int list_channels() {
resp.n_channels = 0;

for (uint32_t i = 0; i < MAX_CHANNEL_COUNT; i++) {
if (decoder_status.subscribed_channels[i].active) {
resp.channel_info[resp.n_channels].channel = decoder_status.subscribed_channels[i].id;
resp.channel_info[resp.n_channels].start = decoder_status.subscribed_channels[i].start_timestamp;
resp.channel_info[resp.n_channels].end = decoder_status.subscribed_channels[i].end_timestamp;
resp.n_channels++;
}
if (CHECKER_VERIFY_CHANNEL((uint32_t*)&decoder_status.subscribed_channels[i])) {
if (decoder_status.subscribed_channels[i].active) {
resp.channel_info[resp.n_channels].channel = decoder_status.subscribed_channels[i].id;
resp.channel_info[resp.n_channels].start = decoder_status.subscribed_channels[i].start_timestamp;
resp.channel_info[resp.n_channels].end = decoder_status.subscribed_channels[i].end_timestamp;
resp.n_channels++;
}
} else
return integrity_failure();
}

len = sizeof(resp.n_channels) + (sizeof(channel_info_t) * resp.n_channels);
Expand All @@ -222,17 +237,6 @@ int list_channels() {
}


/** @brief Updates the channel subscription for a subset of channels.
*
* @param pkt_len The length of the incoming packet
* @param update A pointer to an array of channel_update structs,
* which contains the channel number, start, and end timestamps
* for each channel being updated.
*
* @note Take care to note that this system is little endian.
*
* @return 0 upon success. -1 if error.
*/
/** @brief Updates the channel subscription for a subset of channels.
*
* @param pkt_len The length of the incoming packet
Expand Down Expand Up @@ -311,16 +315,21 @@ int update_subscription(pkt_len_t pkt_len, encrypted_subscription_update_packet_
// Find the first empty slot in the subscription array
for (i = 0; i < MAX_CHANNEL_COUNT; i++) {
if (decoder_status.subscribed_channels[i].id == update->channel || !decoder_status.subscribed_channels[i].active) {
if (update->start_timestamp > update->end_timestamp) {
STATUS_LED_RED();
print_error("Failed to update subscription - end time is before start time. Please ensure your time is linearly increasing.\n");
return -1;
}
decoder_status.subscribed_channels[i].active = true;
decoder_status.subscribed_channels[i].id = update->channel;
decoder_status.subscribed_channels[i].start_timestamp = update->start_timestamp;
decoder_status.subscribed_channels[i].end_timestamp = update->end_timestamp;
break;
if (CHECKER_VERIFY_CHANNEL((uint32_t*)&decoder_status.subscribed_channels[i])) {
if (update->start_timestamp > update->end_timestamp) {
STATUS_LED_RED();
print_error("Failed to update subscription - end time is before start time. Please ensure your time is linearly increasing.\n");
return -1;
}
decoder_status.subscribed_channels[i].active = true;
decoder_status.subscribed_channels[i].id = update->channel;
decoder_status.subscribed_channels[i].start_timestamp = update->start_timestamp;
decoder_status.subscribed_channels[i].end_timestamp = update->end_timestamp;

CHECKER_REMEMBER_CHANNEL((uint32_t*)&decoder_status.subscribed_channels[i]);
break;
} else
return integrity_failure();
}
}

Expand Down Expand Up @@ -380,13 +389,16 @@ int decode(pkt_len_t pkt_len, frame_packet_t *new_frame) {
memcpy(aad + sizeof(channel), &timestamp, sizeof(timestamp));

print_debug("Checking subscription\n");
if (!is_subscribed(channel, timestamp)) {
int is_subbed = is_subscribed(channel, timestamp);
if (! is_subbed) {
STATUS_LED_RED();
sprintf(
output_buf,
"Receiving unsubscribed channel data or timestamp invalid. %u\n", channel);
print_error(output_buf);
return -1;
} else if (is_subbed < 0) {
return -1;
}

const uint8_t *decryption_key = get_channel_key(channel);
Expand Down Expand Up @@ -472,6 +484,10 @@ void init() {
// Write the starting channel subscriptions into flash.
memcpy(decoder_status.subscribed_channels, subscription, MAX_CHANNEL_COUNT*sizeof(channel_status_t));

for (int i = 0; i < MAX_CHANNEL_COUNT; i++){
CHECKER_REMEMBER_CHANNEL((uint32_t*)&decoder_status.subscribed_channels[i]);
}

flash_simple_erase_page(FLASH_STATUS_ADDR);
flash_simple_write(FLASH_STATUS_ADDR, &decoder_status, sizeof(flash_entry_t));
}
Expand Down Expand Up @@ -517,6 +533,7 @@ int main(void) {
// initialize the device
init();
TRNG_Initialize();
CHECKER_INIT();

print_debug("Decoder Booted!\n");

Expand All @@ -541,7 +558,8 @@ int main(void) {
// Handle list command
case LIST_MSG:
STATUS_LED_CYAN();
list_channels();
if (list_channels() < 0)
return -1;
break;

// Handle decode command
Expand All @@ -553,7 +571,8 @@ int main(void) {
// Handle subscribe command
case SUBSCRIBE_MSG:
STATUS_LED_YELLOW();
update_subscription(pkt_len, (encrypted_subscription_update_packet_t *)uart_buf);
if (update_subscription(pkt_len, (encrypted_subscription_update_packet_t *)uart_buf) < 0)
return -1;
break;

// Handle bad command
Expand All @@ -563,5 +582,7 @@ int main(void) {
print_error(output_buf);
break;
}
}
};

CHECKER_END();
}