Skip to content

Commit

Permalink
feat(hw/misc): Add support for XTS-AES 256 bit keys for ESP32-S3
Browse files Browse the repository at this point in the history
  • Loading branch information
@Harshal5
Harshal5 committed Aug 14, 2024
1 parent 16fed7d commit 879e8ca
Showing 1 changed file with 80 additions and 28 deletions.
108 changes: 80 additions & 28 deletions hw/misc/esp32s3_xts_aes.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,14 @@
#define XTS_AES_WARNING 0
#define XTS_AES_DEBUG 0

#define EFUSE_KEY_PURPOSE_XTS_AES_128_KEY 4
#define XTS_AES_KEY_SIZE 32
#define ESP32S3_XTS_AES_DATA_UNIT_SIZE 128
#define ESP32S3_XTS_AES_TWEAK_VALUE 0x3FFFFF80
#define EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_1 2
#define EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_2 3
#define EFUSE_KEY_PURPOSE_XTS_AES_128_KEY 4

#define XTS_AES_KEY_SIZE_128 32
#define XTS_AES_KEY_SIZE_256 64
#define ESP32S3_XTS_AES_DATA_UNIT_SIZE 128
#define ESP32S3_XTS_AES_TWEAK_VALUE 0x3FFFFF80

struct xts_aes_keys_ctx {
AES_KEY enc;
Expand Down Expand Up @@ -82,22 +86,53 @@ static uint32_t esp32s3_xts_aes_get_linesize(ESP32S3XtsAesState *s)
}
}

static void esp32s3_xts_aes_get_key(ESP32S3XtsAesState *s, uint8_t *key)
static uint32_t esp32s3_xts_aes_get_key_size(ESP32S3XtsAesState *s)
{
for (int i = EFUSE_BLOCK_KEY0; i < EFUSE_BLOCK_KEY6; i++) {
if (esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_128_KEY) {
esp32c3_efuse_get_key(s->efuse, i, key);
// flash encryption key is stored in reverse byte order in the efuse block, correct it
uint8_t temp;
for (int j = 0; j < XTS_AES_KEY_SIZE / 2; j++) {
temp = key[j];
key[j] = key[XTS_AES_KEY_SIZE - j - 1];
key[XTS_AES_KEY_SIZE - j - 1] = temp;
if (esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_1
|| esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_2) {
return XTS_AES_KEY_SIZE_256;
}
}
// A key of 128 bits seem to be present
return XTS_AES_KEY_SIZE_128;
}

static void reverse_xts_aes_key(uint8_t *key)
{
uint8_t temp;
for (int j = 0; j < XTS_AES_KEY_SIZE_128 / 2; j++) {
temp = key[j];
key[j] = key[XTS_AES_KEY_SIZE_128 - j - 1];
key[XTS_AES_KEY_SIZE_128 - j - 1] = temp;
}
}

static void esp32s3_xts_aes_get_key(ESP32S3XtsAesState *s, uint8_t *key, uint32_t key_size)
{
memset(key, 0, key_size);

if (key_size == XTS_AES_KEY_SIZE_128) {
for (int i = EFUSE_BLOCK_KEY0; i < EFUSE_BLOCK_KEY6; i++) {
if (esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_128_KEY) {
esp32c3_efuse_get_key(s->efuse, i, key);
// flash encryption key is stored in reverse byte order in the efuse block, correct it
reverse_xts_aes_key(key);
return;
}
}
} else {
// key_size == XTS_AES_KEY_SIZE_256
for (int i = EFUSE_BLOCK_KEY0; i < EFUSE_BLOCK_KEY6; i++) {
if (esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_1) {
esp32c3_efuse_get_key(s->efuse, i, key);
reverse_xts_aes_key(key);
} else if (esp32c3_efuse_get_key_purpose(s->efuse, i) == EFUSE_KEY_PURPOSE_XTS_AES_256_KEY_2) {
esp32c3_efuse_get_key(s->efuse, i, key + XTS_AES_KEY_SIZE_128);
reverse_xts_aes_key(key + XTS_AES_KEY_SIZE_128);
}
return;
}
}
memset(key, 0, XTS_AES_KEY_SIZE);
}

static void esp32s3_xts_aes_read_ciphertext(ESP32S3XtsAesState *s, uint32_t* spi_data_regs, uint32_t* spi_data_size, uint32_t* spi_addr, uint32_t* spi_addr_size)
Expand All @@ -111,7 +146,6 @@ static void esp32s3_xts_aes_read_ciphertext(ESP32S3XtsAesState *s, uint32_t* spi

static void esp32s3_xts_aes_encrypt(ESP32S3XtsAesState *s)
{
uint8_t efuse_key[XTS_AES_KEY_SIZE];
uint8_t tweak[16];
uint32_t linesize = esp32s3_xts_aes_get_linesize(s);

Expand All @@ -123,15 +157,24 @@ static void esp32s3_xts_aes_encrypt(ESP32S3XtsAesState *s)
*((uint32_t *) tweak) = cpu_to_le32((s->physical_addr & ESP32S3_XTS_AES_TWEAK_VALUE) + (s->destination << 30));
memset(tweak + 4, 0, 12);

esp32s3_xts_aes_get_key(s, efuse_key);
uint32_t efuse_key_size = esp32s3_xts_aes_get_key_size(s);

uint8_t *efuse_key = g_malloc(efuse_key_size * sizeof(uint8_t));

if (efuse_key == NULL) {
error_report("[XTS-AES] Memory allocation for the efuse key failed");
return;
}

esp32s3_xts_aes_get_key(s, efuse_key, efuse_key_size);

struct xts_aes_keys_ctx aesdata = {};
struct xts_aes_keys_ctx aestweak = {};

AES_set_encrypt_key(efuse_key, XTS_AES_KEY_SIZE / 2 * 8, &aesdata.enc);
AES_set_decrypt_key(efuse_key, XTS_AES_KEY_SIZE / 2 * 8, &aesdata.dec);
AES_set_encrypt_key(efuse_key + XTS_AES_KEY_SIZE / 2, XTS_AES_KEY_SIZE / 2 * 8, &aestweak.enc);
AES_set_decrypt_key(efuse_key + XTS_AES_KEY_SIZE / 2, XTS_AES_KEY_SIZE / 2 * 8, &aestweak.dec);
AES_set_encrypt_key(efuse_key, efuse_key_size / 2 * 8, &aesdata.enc);
AES_set_decrypt_key(efuse_key, efuse_key_size / 2 * 8, &aesdata.dec);
AES_set_encrypt_key(efuse_key + efuse_key_size / 2, efuse_key_size / 2 * 8, &aestweak.enc);
AES_set_decrypt_key(efuse_key + efuse_key_size / 2, efuse_key_size / 2 * 8, &aestweak.dec);

memset(input_plaintext, 0, ESP32S3_XTS_AES_DATA_UNIT_SIZE);

Expand All @@ -154,22 +197,30 @@ static void esp32s3_xts_aes_encrypt(ESP32S3XtsAesState *s)

memset(s->ciphertext, 0, ESP32S3_XTS_AES_PLAIN_REG_CNT * sizeof(uint32_t));
memcpy(s->ciphertext, output_ciphertext + pad_left, linesize);
g_free(efuse_key);
}

static void esp32s3_xts_aes_decrypt(ESP32S3XtsAesState *s, uint32_t physical_address, uint8_t *data, uint32_t size)
{
uint8_t tweak[16];
struct xts_aes_keys_ctx aesdata = {};
struct xts_aes_keys_ctx aestweak = {};

uint8_t efuse_key[XTS_AES_KEY_SIZE];
uint8_t tweak[16];
uint32_t efuse_key_size = esp32s3_xts_aes_get_key_size(s);

uint8_t *efuse_key = g_malloc(efuse_key_size * sizeof(uint8_t));

if (efuse_key == NULL) {
error_report("[XTS-AES] Memory allocation for the efuse key failed");
return;
}

esp32s3_xts_aes_get_key(s, efuse_key);
esp32s3_xts_aes_get_key(s, efuse_key, efuse_key_size);

AES_set_encrypt_key(efuse_key, XTS_AES_KEY_SIZE / 2 * 8, &aesdata.enc);
AES_set_decrypt_key(efuse_key, XTS_AES_KEY_SIZE / 2 * 8, &aesdata.dec);
AES_set_encrypt_key(efuse_key + XTS_AES_KEY_SIZE / 2, XTS_AES_KEY_SIZE / 2 * 8, &aestweak.enc);
AES_set_decrypt_key(efuse_key + XTS_AES_KEY_SIZE / 2, XTS_AES_KEY_SIZE / 2 * 8, &aestweak.dec);
AES_set_encrypt_key(efuse_key, efuse_key_size / 2 * 8, &aesdata.enc);
AES_set_decrypt_key(efuse_key, efuse_key_size / 2 * 8, &aesdata.dec);
AES_set_encrypt_key(efuse_key + efuse_key_size / 2, efuse_key_size / 2 * 8, &aestweak.enc);
AES_set_decrypt_key(efuse_key + efuse_key_size / 2, efuse_key_size / 2 * 8, &aestweak.dec);

uint8_t input_ciphertext[ESP32S3_XTS_AES_DATA_UNIT_SIZE];
uint8_t input_ciphertext_reversed[ESP32S3_XTS_AES_DATA_UNIT_SIZE];
Expand All @@ -196,6 +247,7 @@ static void esp32s3_xts_aes_decrypt(ESP32S3XtsAesState *s, uint32_t physical_add

memcpy(data + i, output_plaintext, ESP32S3_XTS_AES_DATA_UNIT_SIZE);
}
g_free(efuse_key);
}

static uint64_t esp32s3_xts_aes_read(void *opaque, hwaddr addr, unsigned int size)
Expand Down

0 comments on commit 879e8ca

Please sign in to comment.