[sw/sca] Refactor and rename constants and params, cleanup some related code
Signed-off-by: Alphan Ulusoy <alphan@google.com>
diff --git a/sw/device/sca/aes_serial/aes_serial.c b/sw/device/sca/aes_serial/aes_serial.c
index a691056..c9d0366 100644
--- a/sw/device/sca/aes_serial/aes_serial.c
+++ b/sw/device/sca/aes_serial/aes_serial.c
@@ -25,14 +25,38 @@
static dif_rv_timer_t timer;
static dif_uart_t uart;
-// UART input maximum buffer sizes
-static const uint32_t kMaxInputLengthText = 128;
-static const uint32_t kMaxInputLengthBin = 64;
-
-// AES Configuration parameters. These values must match the test driving
-// side.
-static const uint32_t kAesBlockSize = 16;
-static const uint32_t kAesKeySize = 16;
+enum {
+ kAesKeySize = 16,
+ /**
+ * Number of cycles (at `kClockFreqCpuHz`) that Ibex should sleep to minimize
+ * noise during AES operations. Caution: This number should be chosen to
+ * provide enough time. Otherwise, Ibex might wake up while AES is still busy
+ * and disturb the capture. Currently, we use a start trigger delay of 40
+ * clock cycles and the scope captures 18 clock cycles at kClockFreqCpuHz (180
+ * samples). The latter number will likely increase as we improve the security
+ * hardening.
+ */
+ kIbexAesSleepCycles = 200,
+ /**
+ * GPIO capture trigger values.
+ */
+ kGpioCaptureTriggerHigh = 0x08200,
+ kGpioCaptureTriggerLow = 0x00000,
+ /**
+ * RV timer settings.
+ */
+ kRvTimerComparator = 0,
+ kRvTimerHart = kTopEarlgreyPlicTargetIbex0,
+ /**
+ * UART constants.
+ */
+ kUartMaxRxSizeText = 128,
+ kUartMaxRxSizeBin = 64,
+ /**
+ * Simple serial protocol version 1.1.
+ */
+ kSimpleSerialProtocolVersion = 1,
+};
// Simple serial status codes
typedef enum simple_serial_result {
@@ -40,23 +64,6 @@
kSimpleSerialError = 1
} simple_serial_result_t;
-// Simple serial protocol version 1.1
-static const uint32_t kSimpleSerialProtocolVersion = 1;
-
-// GPIO capture trigger values
-static const uint32_t kGpioCaptureTriggerHigh = 0x08200;
-static const uint32_t kGpioCaptureTriggerLow = 0x00000;
-
-// RV Timer settings
-static const uint32_t kHart = (uint32_t)kTopEarlgreyPlicTargetIbex0;
-static const uint32_t kComparator = 0;
-static const uint64_t kDeadline = 200; // 200 clock cycles at kClockFreqCpuHz
-// Caution: This number should be chosen to provide enough time. Otherwise,
-// Ibex might wake up while AES is still busy and disturb the capture.
-// Currently, we use a start trigger delay of 40 clock cycles and the scope
-// captures 18 clock cycles at kClockFreqCpuHz (180 samples). The latter number
-// will likely increase as we improve the security hardening.
-
// TODO: Remove once there is a CHECK version that does not require test
// library dependencies.
#define CHECK(condition, ...) \
@@ -143,17 +150,6 @@
}
/**
- * Return number of AES blocks from `plain_text_len`.
- */
-static size_t get_num_blocks(size_t plain_text_len) {
- size_t num_blocks = plain_text_len / kAesBlockSize;
- if ((plain_text_len - (num_blocks * kAesBlockSize)) > 0) {
- ++num_blocks;
- }
- return num_blocks;
-}
-
-/**
* Simple serial set AES key command.
*
* @param aes_cfg AES configuration object.
@@ -186,25 +182,24 @@
* Simple serial trigger AES encryption command.
*
* @param aes_cfg AES configuration object.
- * @param plain_text plain text to be encrypted.
- * @param plain_text_len plain text length.
+ * @param plaintext plain text to be encrypted.
+ * @param plaintext_len plain text length.
*
* @return kSimpleSerialOk on success, kSimpleSerialError otherwise.
*/
static simple_serial_result_t simple_serial_trigger_encryption(
- const uint8_t *plain_text, size_t plain_text_len) {
- if (plain_text_len > kMaxInputLengthBin) {
+ const uint8_t *plaintext, size_t plaintext_len) {
+ if (plaintext_len > kUartMaxRxSizeBin) {
return kSimpleSerialError;
}
- uint8_t cipher_text[64];
- size_t num_blocks = get_num_blocks(plain_text_len);
- if (num_blocks != 1) {
+ uint8_t ciphertext[64];
+ if (plaintext_len != kAesKeySize) {
return kSimpleSerialError;
}
// Provide input data to AES.
- aes_data_put_wait(plain_text);
+ aes_data_put_wait(plaintext);
// Arm capture trigger. The actual trigger signal used for capture is a
// combination (logical AND) of:
@@ -216,12 +211,13 @@
// Start timer to wake up Ibex after AES is done.
uint64_t current_time;
- SS_CHECK(dif_rv_timer_counter_read(&timer, kHart, ¤t_time) ==
+ SS_CHECK(dif_rv_timer_counter_read(&timer, kRvTimerHart, ¤t_time) ==
kDifRvTimerOk);
- SS_CHECK(dif_rv_timer_arm(&timer, kHart, kComparator,
- current_time + kDeadline) == kDifRvTimerOk);
+ SS_CHECK(dif_rv_timer_arm(&timer, kRvTimerHart, kRvTimerComparator,
+ current_time + kIbexAesSleepCycles) ==
+ kDifRvTimerOk);
SS_CHECK(dif_rv_timer_counter_set_enabled(
- &timer, kHart, kDifRvTimerEnabled) == kDifRvTimerOk);
+ &timer, kRvTimerHart, kDifRvTimerEnabled) == kDifRvTimerOk);
// Start AES operation (this triggers the capture) and go to sleep.
// Using the SecAesStartTriggerDelay hardware parameter, the AES unit is
@@ -234,9 +230,9 @@
SS_CHECK(dif_gpio_write_all(&gpio, kGpioCaptureTriggerLow) == kDifGpioOk);
// Retrieve output data from AES.
- aes_data_get_wait(cipher_text);
+ aes_data_get_wait(ciphertext);
- print_cmd_response('r', cipher_text, plain_text_len);
+ print_cmd_response('r', ciphertext, plaintext_len);
return kSimpleSerialOk;
}
@@ -251,7 +247,7 @@
const uint8_t *cmd, size_t cmd_len) {
// Data length is half the size of the hex encoded string.
const size_t data_len = cmd_len >> 1;
- if (data_len >= kMaxInputLengthBin) {
+ if (data_len >= kUartMaxRxSizeBin) {
return;
}
uint8_t data[64] = {0};
@@ -263,7 +259,7 @@
}
if (cmd[0] == 'v') {
- print_cmd_response('z', (const uint8_t *)&kSimpleSerialProtocolVersion,
+ print_cmd_response('z', (uint8_t[1]){kSimpleSerialProtocolVersion},
/*data_len=*/1);
return;
}
@@ -312,9 +308,9 @@
CHECK(dif_rv_timer_approximate_tick_params(kClockFreqPeripheralHz,
kClockFreqCpuHz, &tick_params) ==
kDifRvTimerApproximateTickParamsOk);
- CHECK(dif_rv_timer_set_tick_params(&timer, kHart, tick_params) ==
+ CHECK(dif_rv_timer_set_tick_params(&timer, kRvTimerHart, tick_params) ==
kDifRvTimerOk);
- CHECK(dif_rv_timer_irq_enable(&timer, kHart, kComparator,
+ CHECK(dif_rv_timer_irq_enable(&timer, kRvTimerHart, kRvTimerComparator,
kDifRvTimerEnabled) == kDifRvTimerOk);
dif_gpio_params_t gpio_params = {
@@ -351,18 +347,19 @@
// Going over the maxium buffer size will result in corrupting the input
// buffer. This is okay in this case since we control the script used
// to drive the UART input.
- pos = (pos + 1) % kMaxInputLengthText;
+ pos = (pos + 1) % kUartMaxRxSizeText;
}
}
}
void handler_irq_timer(void) {
bool irq_flag;
- CHECK(dif_rv_timer_irq_get(&timer, kHart, kComparator, &irq_flag) ==
- kDifRvTimerOk);
+ CHECK(dif_rv_timer_irq_get(&timer, kRvTimerHart, kRvTimerComparator,
+ &irq_flag) == kDifRvTimerOk);
CHECK(irq_flag, "Entered IRQ handler but the expected IRQ flag wasn't set!");
- CHECK(dif_rv_timer_counter_set_enabled(&timer, kHart, kDifRvTimerDisabled) ==
+ CHECK(dif_rv_timer_counter_set_enabled(&timer, kRvTimerHart,
+ kDifRvTimerDisabled) == kDifRvTimerOk);
+ CHECK(dif_rv_timer_irq_clear(&timer, kRvTimerHart, kRvTimerComparator) ==
kDifRvTimerOk);
- CHECK(dif_rv_timer_irq_clear(&timer, kHart, kComparator) == kDifRvTimerOk);
}
