Crash_Override/OVMS3-idf
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

spi_flash_write_encrypted: Allow 16-byte aligned block writes

Browse source 
As each 32 byte write has two identical 16 byte AES blocks, it's
possible to write them separately.
This commit is contained in:
Angus Gratton 2017-01-04 17:53:15 +11:00 committed by Ivan Grokhotkov
parent 36ccdee6ec
commit adc590ff69
3 changed files with 140 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

54
components/spi_flash/flash_ops.c
View file

@ -90,7 +90,7 @@ size_t spi_flash_get_chip_size()
return g_rom_flashchip.chip_size;
}
SpiFlashOpResult IRAM_ATTR spi_flash_unlock()
static SpiFlashOpResult IRAM_ATTR spi_flash_unlock()
{
static bool unlocked = false;
if (!unlocked) {
@ -260,30 +260,58 @@ out:
esp_err_t IRAM_ATTR spi_flash_write_encrypted(size_t dest_addr, const void *src, size_t size)
{
if ((dest_addr % 32) != 0) {
const uint8_t *ssrc = (const uint8_t *)src;
if ((dest_addr % 16) != 0) {
return ESP_ERR_INVALID_ARG;
}
if ((size % 32) != 0) {
if ((size % 16) != 0) {
return ESP_ERR_INVALID_SIZE;
}
if ((uint32_t) src < 0x3ff00000) {
// if source address is in DROM, we won't be able to read it
// from within SPIWrite
// TODO: consider buffering source data using heap and writing it anyway?
return ESP_ERR_INVALID_ARG;
}
COUNTER_START();
spi_flash_disable_interrupts_caches_and_other_cpu();
SpiFlashOpResult rc;
rc = spi_flash_unlock();
spi_flash_enable_interrupts_caches_and_other_cpu();
if (rc == SPI_FLASH_RESULT_OK) {
/* SPI_Encrypt_Write encrypts data in RAM as it writes,
so copy to a temporary buffer - 32 bytes at a time.
Each call to SPI_Encrypt_Write takes a 32 byte "row" of
data to encrypt, and each row is two 16 byte AES blocks
that share a key (as derived from flash address).
*/
uint32_t encrypt_buf[32/sizeof(uint32_t)];
for (size_t i = 0; i < size; i += 32) {
memcpy(encrypt_buf, ((const uint8_t *)src) + i, 32);
rc = SPI_Encrypt_Write((uint32_t) dest_addr + i, encrypt_buf, 32);
uint8_t encrypt_buf[32] __attribute__((aligned(4)));
uint32_t row_size;
for (size_t i = 0; i < size; i += row_size) {
uint32_t row_addr = dest_addr + i;
if (i == 0 && (row_addr % 32) != 0) {
/* writing to second block of a 32 byte row */
row_size = 16;
row_addr -= 16;
/* copy to second block in buffer */
memcpy(encrypt_buf + 16, ssrc + i, 16);
/* decrypt the first block from flash, will reencrypt to same bytes */
spi_flash_read_encrypted(row_addr, encrypt_buf, 16);
}
else if (size - i == 16) {
/* 16 bytes left, is first block of a 32 byte row */
row_size = 16;
/* copy to first block in buffer */
memcpy(encrypt_buf, ssrc + i, 16);
/* decrypt the second block from flash, will reencrypt to same bytes */
spi_flash_read_encrypted(row_addr + 16, encrypt_buf + 16, 16);
}
else {
/* Writing a full 32 byte row (2 blocks) */
row_size = 32;
memcpy(encrypt_buf, ssrc + i, 32);
}
spi_flash_disable_interrupts_caches_and_other_cpu();
rc = SPI_Encrypt_Write(row_addr, (uint32_t *)encrypt_buf, 32);
spi_flash_enable_interrupts_caches_and_other_cpu();
if (rc != SPI_FLASH_RESULT_OK) {
break;
}

14
components/spi_flash/include/esp_spi_flash.h
View file

@ -92,14 +92,16 @@ esp_err_t spi_flash_write(size_t dest_addr, const void *src, size_t size);
*
* @note Flash encryption must be enabled for this function to work.
*
* @note Address in flash, dest, has to be 32-byte aligned.
* @note Destination flash address and length must be 16-byte
* aligned. Due to hardware limitations, this function is more
* efficient if both these arguments are 32-byte aligned. This is
* because the encryption engine natively deals with 32-byte rows of
* two AES blocks. Writing half a row (16 bytes) requires reading out
* the other 16 bytes and re-encrypting them back to the same value.
*
* @note If source address is in DROM, this function will return
* ESP_ERR_INVALID_ARG.
*
* @param dest_addr destination address in Flash. Must be a multiple of 32 bytes.
* @param dest_addr destination address in Flash. Must be a multiple of 16 bytes.
* @param src pointer to the source buffer.
* @param size length of data, in bytes. Must be a multiple of 32 bytes.
* @param size length of data, in bytes. Must be a multiple of 16 bytes.
*
* @return esp_err_t
*/

91
components/spi_flash/test/test_flash_encryption.c Normal file
View file

@ -0,0 +1,91 @@
#include <stdio.h>
#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <freertos/semphr.h>
#include <unity.h>
#include <esp_spi_flash.h>
#include <esp_attr.h>
#include <esp_flash_encrypt.h>
#include "test_config.h"
static void test_encrypted_write(size_t offset, const uint8_t *data, size_t length);
static void verify_erased_flash(size_t offset, size_t length);
TEST_CASE("test 16 byte encrypted writes", "[spi_flash]")
{
if (!esp_flash_encryption_enabled()) {
TEST_IGNORE_MESSAGE("flash encryption disabled, skipping spi_flash_write_encrypted() tests");
}
TEST_ASSERT_EQUAL_HEX(ESP_OK,
spi_flash_erase_sector(TEST_REGION_START / SPI_FLASH_SEC_SIZE));
uint8_t fortyeight_bytes[0x30]; // 0, 1, 2, 3, 4... 47
for(int i = 0; i < sizeof(fortyeight_bytes); i++) {
fortyeight_bytes[i] = i;
}
/* Verify unaligned start or length fails */
TEST_ASSERT_EQUAL_HEX(ESP_ERR_INVALID_ARG,
spi_flash_write_encrypted(TEST_REGION_START+1, fortyeight_bytes, 32));
TEST_ASSERT_EQUAL_HEX(ESP_ERR_INVALID_SIZE,
spi_flash_write_encrypted(TEST_REGION_START, fortyeight_bytes, 15));
/* ensure nothing happened to the flash yet */
verify_erased_flash(TEST_REGION_START, 0x20);
/* Write 32 byte block, this is the "normal" encrypted write */
test_encrypted_write(TEST_REGION_START, fortyeight_bytes, 0x20);
verify_erased_flash(TEST_REGION_START + 0x20, 0x20);
/* Slip in an unaligned spi_flash_read_encrypted() test */
uint8_t buf[0x10];
spi_flash_read_encrypted(TEST_REGION_START+0x10, buf, 0x10);
TEST_ASSERT_EQUAL_HEX8_ARRAY(fortyeight_bytes+0x10, buf, 16);
/* Write 16 bytes unaligned */
test_encrypted_write(TEST_REGION_START + 0x30, fortyeight_bytes, 0x10);
/* the 16 byte regions before and after the 16 bytes we just wrote should still be 0xFF */
verify_erased_flash(TEST_REGION_START + 0x20, 0x10);
verify_erased_flash(TEST_REGION_START + 0x40, 0x10);
/* Write 48 bytes starting at a 32-byte aligned offset */
test_encrypted_write(TEST_REGION_START + 0x40, fortyeight_bytes, 0x30);
/* 16 bytes after this write should still be 0xFF -unencrypted- */
verify_erased_flash(TEST_REGION_START + 0x70, 0x10);
/* Write 48 bytes starting at a 16-byte aligned offset */
test_encrypted_write(TEST_REGION_START + 0x90, fortyeight_bytes, 0x30);
/* 16 bytes after this write should still be 0xFF -unencrypted- */
verify_erased_flash(TEST_REGION_START + 0x120, 0x10);
}
static void test_encrypted_write(size_t offset, const uint8_t *data, size_t length)
{
uint8_t readback[length];
printf("encrypt %d bytes at 0x%x\n", length, offset);
TEST_ASSERT_EQUAL_HEX(ESP_OK,
spi_flash_write_encrypted(offset, data, length));
TEST_ASSERT_EQUAL_HEX(ESP_OK,
spi_flash_read_encrypted(offset, readback, length));
TEST_ASSERT_EQUAL_HEX8_ARRAY(data, readback, length);
}
static void verify_erased_flash(size_t offset, size_t length)
{
uint8_t readback[length];
printf("verify erased 0x%x - 0x%x\n", offset, offset + length);
TEST_ASSERT_EQUAL_HEX(ESP_OK,
spi_flash_read(offset, readback, length));
for (int i = 0; i < length; i++) {
char message[32];
sprintf(message, "unerased flash @ 0x%08x", offset + i);
TEST_ASSERT_EQUAL_HEX_MESSAGE(0xFF, readback[i], message);
}
}