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Code Issues Releases Wiki Activity

feat(storage): Support PIN and wipe code of unlimited length.

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This commit is contained in:
Andrew Kozlik 2020-08-13 18:51:11 +02:00 committed by Andrew Kozlik
parent 1cc719bf49
commit c68e91c12a
3 changed files with 333 additions and 124 deletions
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437
storage/storage.c
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@ -35,33 +35,47 @@
// The APP namespace which is reserved for storage related values. // The APP namespace which is reserved for storage related values.
#define APP_STORAGE 0x00 #define APP_STORAGE 0x00
// Norcow storage key of the PIN entry log and PIN success log. // Norcow storage keys.
// PIN entry log and PIN success log.
#define PIN_LOGS_KEY ((APP_STORAGE << 8) | 0x01) #define PIN_LOGS_KEY ((APP_STORAGE << 8) | 0x01)
// Norcow storage key of the combined salt, EDEK, ESAK and PIN verification code // Combined salt, EDEK, ESAK and PIN verification code entry.
// entry.
#define EDEK_PVC_KEY ((APP_STORAGE << 8) | 0x02) #define EDEK_PVC_KEY ((APP_STORAGE << 8) | 0x02)
// Norcow storage key of the PIN set flag. // PIN set flag.
#define PIN_NOT_SET_KEY ((APP_STORAGE << 8) | 0x03) #define PIN_NOT_SET_KEY ((APP_STORAGE << 8) | 0x03)
// Norcow storage key of the storage version. // Authenticated storage version.
// NOTE: This should equal the norcow version unless an upgrade is in progress.
#define VERSION_KEY ((APP_STORAGE << 8) | 0x04) #define VERSION_KEY ((APP_STORAGE << 8) | 0x04)
// Norcow storage key of the storage authentication tag. // Storage authentication tag.
#define STORAGE_TAG_KEY ((APP_STORAGE << 8) | 0x05) #define STORAGE_TAG_KEY ((APP_STORAGE << 8) | 0x05)
// Norcow storage key of the wipe code data. // Wipe code data. Introduced in storage version 2.
#define WIPE_CODE_DATA_KEY ((APP_STORAGE << 8) | 0x06) #define WIPE_CODE_DATA_KEY ((APP_STORAGE << 8) | 0x06)
// Norcow storage key of the storage upgrade flag. // Storage upgrade flag. Introduced in storage version 2.
#define STORAGE_UPGRADED_KEY ((APP_STORAGE << 8) | 0x07) #define STORAGE_UPGRADED_KEY ((APP_STORAGE << 8) | 0x07)
// The PIN value corresponding to an invalid PIN. // Unauthenticated storage version. Introduced in storage version 3.
#define PIN_INVALID 0 // NOTE: This should always equal the value in VERSION_KEY.
#define UNAUTH_VERSION_KEY ((APP_STORAGE << 8) | 0x08)
// The PIN value corresponding to an empty PIN. // The PIN value corresponding to an empty PIN.
#define PIN_EMPTY 1 const uint8_t *PIN_EMPTY = (const uint8_t *)"";
// The uint32 representation of an empty PIN, used prior to storage version 3.
const uint32_t V0_PIN_EMPTY = 1;
// Maximum number of PIN digits allowed prior to storage version 3.
#define V0_MAX_PIN_LEN 9
// Maximum length of the wipe code.
// Some limit should be imposed on the length, because the wipe code takes up
// storage space proportional to the length, as opposed to the PIN, which takes
// up constant storage space.
#define MAX_WIPE_CODE_LEN 50
// Maximum number of failed unlock attempts. // Maximum number of failed unlock attempts.
// NOTE: The PIN counter logic relies on this constant being less than or equal // NOTE: The PIN counter logic relies on this constant being less than or equal
@ -114,23 +128,20 @@
// The length of the ChaCha20 block in bytes. // The length of the ChaCha20 block in bytes.
#define CHACHA20_BLOCK_SIZE 64 #define CHACHA20_BLOCK_SIZE 64
// The length of the wipe code in bytes.
#define WIPE_CODE_SIZE (sizeof(uint32_t))
// The byte length of the salt used in checking the wipe code. // The byte length of the salt used in checking the wipe code.
#define WIPE_CODE_SALT_SIZE 8 #define WIPE_CODE_SALT_SIZE 8
// The byte length of the tag used in checking the wipe code. // The byte length of the tag used in checking the wipe code.
#define WIPE_CODE_TAG_SIZE 8 #define WIPE_CODE_TAG_SIZE 8
// The total length of the WIPE_CODE_DATA_KEY entry.
#define WIPE_CODE_DATA_SIZE \
(WIPE_CODE_SIZE + WIPE_CODE_SALT_SIZE + WIPE_CODE_TAG_SIZE)
// The value corresponding to an unconfigured wipe code. // The value corresponding to an unconfigured wipe code.
// NOTE: This is intentionally different from PIN_EMPTY so that we don't need // NOTE: This is intentionally different from an empty PIN so that we don't need
// special handling when both the PIN and wipe code are not set. // special handling when both the PIN and wipe code are not set.
#define WIPE_CODE_EMPTY 0 const uint8_t WIPE_CODE_EMPTY[] = {0, 0, 0, 0};
#define WIPE_CODE_EMPTY_LEN 4
// The uint32 representation of an empty wipe code used in storage version 2.
#define V2_WIPE_CODE_EMPTY 0
// The length of the counter tail in words. // The length of the counter tail in words.
#define COUNTER_TAIL_WORDS 2 #define COUNTER_TAIL_WORDS 2
@ -164,7 +175,10 @@ static void __handle_fault(const char *msg, const char *file, int line,
const char *func); const char *func);
#define handle_fault(msg) (__handle_fault(msg, __FILE__, __LINE__, __func__)) #define handle_fault(msg) (__handle_fault(msg, __FILE__, __LINE__, __func__))
static uint32_t pin_to_int(const uint8_t *pin, size_t pin_len);
static secbool storage_upgrade(void); static secbool storage_upgrade(void);
static secbool storage_upgrade_unlocked(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt);
static secbool storage_set_encrypted(const uint16_t key, const void *val, static secbool storage_set_encrypted(const uint16_t key, const void *val,
const uint16_t len); const uint16_t len);
static secbool storage_get_encrypted(const uint16_t key, void *val_dest, static secbool storage_get_encrypted(const uint16_t key, void *val_dest,
@ -359,29 +373,53 @@ static secbool auth_get(uint16_t key, const void **val, uint16_t *len) {
return sectrue; return sectrue;
} }
static secbool set_wipe_code(uint32_t wipe_code) { static secbool set_wipe_code(const uint8_t *wipe_code, size_t wipe_code_len) {
if (wipe_code == PIN_EMPTY) { if (wipe_code_len > MAX_WIPE_CODE_LEN ||
wipe_code_len > UINT16_MAX - WIPE_CODE_SALT_SIZE - WIPE_CODE_TAG_SIZE) {
return secfalse;
}
if (wipe_code_len == 0) {
// This is to avoid having to check pin != PIN_EMPTY when checking the wipe // This is to avoid having to check pin != PIN_EMPTY when checking the wipe
// code. // code.
wipe_code = WIPE_CODE_EMPTY; wipe_code = WIPE_CODE_EMPTY;
wipe_code_len = WIPE_CODE_EMPTY_LEN;
} }
// The format of the WIPE_CODE_DATA_KEY entry is: // The format of the WIPE_CODE_DATA_KEY entry is:
// wipe code (4 bytes), random salt (16 bytes), authentication tag (16 bytes) // wipe code (variable), random salt (16 bytes), authentication tag (16 bytes)
// NOTE: We allocate extra space for the HMAC computation. // NOTE: We allocate extra space for the HMAC result.
uint8_t wipe_code_data[WIPE_CODE_SIZE + WIPE_CODE_SALT_SIZE + uint8_t salt_and_tag[WIPE_CODE_SALT_SIZE + SHA256_DIGEST_LENGTH] = {0};
SHA256_DIGEST_LENGTH] = {0}; uint8_t *salt = salt_and_tag;
uint8_t *salt = wipe_code_data + WIPE_CODE_SIZE; uint8_t *tag = salt_and_tag + WIPE_CODE_SALT_SIZE;
uint8_t *tag = wipe_code_data + WIPE_CODE_SIZE + WIPE_CODE_SALT_SIZE;
memcpy(wipe_code_data, &wipe_code, sizeof(wipe_code));
memzero(&wipe_code, sizeof(wipe_code));
random_buffer(salt, WIPE_CODE_SALT_SIZE); random_buffer(salt, WIPE_CODE_SALT_SIZE);
hmac_sha256(salt, WIPE_CODE_SALT_SIZE, wipe_code_data, WIPE_CODE_SIZE, tag); hmac_sha256(salt, WIPE_CODE_SALT_SIZE, wipe_code, wipe_code_len, tag);
return norcow_set(WIPE_CODE_DATA_KEY, wipe_code_data, WIPE_CODE_DATA_SIZE);
// Preallocate the entry in the flash storage.
if (sectrue !=
norcow_set(WIPE_CODE_DATA_KEY, NULL,
wipe_code_len + WIPE_CODE_SALT_SIZE + WIPE_CODE_TAG_SIZE)) {
return secfalse;
}
// Write wipe code into the preallocated entry.
if (sectrue !=
norcow_update_bytes(WIPE_CODE_DATA_KEY, 0, wipe_code, wipe_code_len)) {
return secfalse;
}
// Write salt and tag into the preallocated entry.
if (sectrue !=
norcow_update_bytes(WIPE_CODE_DATA_KEY, wipe_code_len, salt_and_tag,
WIPE_CODE_SALT_SIZE + WIPE_CODE_TAG_SIZE)) {
return secfalse;
}
return sectrue;
} }
static secbool is_not_wipe_code(uint32_t pin) { static secbool is_not_wipe_code(const uint8_t *pin, size_t pin_len) {
uint8_t wipe_code[WIPE_CODE_SIZE] = {0};
uint8_t salt[WIPE_CODE_SALT_SIZE] = {0}; uint8_t salt[WIPE_CODE_SALT_SIZE] = {0};
uint8_t stored_tag[WIPE_CODE_TAG_SIZE] = {0}; uint8_t stored_tag[WIPE_CODE_TAG_SIZE] = {0};
uint8_t computed_tag1[SHA256_DIGEST_LENGTH] = {0}; uint8_t computed_tag1[SHA256_DIGEST_LENGTH] = {0};
@ -391,20 +429,20 @@ static secbool is_not_wipe_code(uint32_t pin) {
const void *wipe_code_data = NULL; const void *wipe_code_data = NULL;
uint16_t len = 0; uint16_t len = 0;
if (sectrue != norcow_get(WIPE_CODE_DATA_KEY, &wipe_code_data, &len) || if (sectrue != norcow_get(WIPE_CODE_DATA_KEY, &wipe_code_data, &len) ||
len != WIPE_CODE_DATA_SIZE) { len <= WIPE_CODE_SALT_SIZE + WIPE_CODE_TAG_SIZE) {
handle_fault("no wipe code"); handle_fault("no wipe code");
return secfalse; return secfalse;
} }
memcpy(wipe_code, wipe_code_data, sizeof(wipe_code)); const uint8_t *wipe_code = (const uint8_t *)wipe_code_data;
memcpy(salt, (uint8_t *)wipe_code_data + WIPE_CODE_SIZE, sizeof(salt)); size_t wipe_code_len = len - WIPE_CODE_SALT_SIZE - WIPE_CODE_TAG_SIZE;
memcpy(salt, (uint8_t *)wipe_code_data + wipe_code_len, sizeof(salt));
memcpy(stored_tag, memcpy(stored_tag,
(uint8_t *)wipe_code_data + WIPE_CODE_SIZE + WIPE_CODE_SALT_SIZE, (uint8_t *)wipe_code_data + wipe_code_len + WIPE_CODE_SALT_SIZE,
sizeof(stored_tag)); sizeof(stored_tag));
// Check integrity in case of flash read manipulation attack. // Check integrity in case of flash read manipulation attack.
hmac_sha256(salt, WIPE_CODE_SALT_SIZE, wipe_code, sizeof(wipe_code), hmac_sha256(salt, WIPE_CODE_SALT_SIZE, wipe_code, wipe_code_len,
computed_tag1); computed_tag1);
memzero(wipe_code, sizeof(wipe_code));
if (sectrue != secequal(stored_tag, computed_tag1, sizeof(stored_tag))) { if (sectrue != secequal(stored_tag, computed_tag1, sizeof(stored_tag))) {
handle_fault("wipe code tag"); handle_fault("wipe code tag");
return secfalse; return secfalse;
@ -412,20 +450,17 @@ static secbool is_not_wipe_code(uint32_t pin) {
// Prepare the authentication tag of the entered PIN. // Prepare the authentication tag of the entered PIN.
wait_random(); wait_random();
hmac_sha256(salt, WIPE_CODE_SALT_SIZE, (const uint8_t *)&pin, WIPE_CODE_SIZE, hmac_sha256(salt, WIPE_CODE_SALT_SIZE, pin, pin_len, computed_tag1);
computed_tag1);
// Recompute to check for fault injection attack. // Recompute to check for fault injection attack.
wait_random(); wait_random();
hmac_sha256(salt, WIPE_CODE_SALT_SIZE, (const uint8_t *)&pin, WIPE_CODE_SIZE, hmac_sha256(salt, WIPE_CODE_SALT_SIZE, pin, pin_len, computed_tag2);
computed_tag2);
memzero(salt, sizeof(salt)); memzero(salt, sizeof(salt));
if (sectrue != if (sectrue !=
secequal(computed_tag1, computed_tag2, sizeof(computed_tag1))) { secequal(computed_tag1, computed_tag2, sizeof(computed_tag1))) {
handle_fault("wipe code fault"); handle_fault("wipe code fault");
return secfalse; return secfalse;
} }
memzero(&pin, sizeof(pin));
// Compare wipe code with the entered PIN via the authentication tag. // Compare wipe code with the entered PIN via the authentication tag.
wait_random(); wait_random();
@ -436,14 +471,10 @@ static secbool is_not_wipe_code(uint32_t pin) {
return sectrue; return sectrue;
} }
static void derive_kek(uint32_t pin, const uint8_t *random_salt, static void derive_kek(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt, const uint8_t *random_salt, const uint8_t *ext_salt,
uint8_t kek[SHA256_DIGEST_LENGTH], uint8_t kek[SHA256_DIGEST_LENGTH],
uint8_t keiv[SHA256_DIGEST_LENGTH]) { uint8_t keiv[SHA256_DIGEST_LENGTH]) {
#if BYTE_ORDER == BIG_ENDIAN
REVERSE32(pin, pin);
#endif
uint8_t salt[HARDWARE_SALT_SIZE + RANDOM_SALT_SIZE + EXTERNAL_SALT_SIZE] = { uint8_t salt[HARDWARE_SALT_SIZE + RANDOM_SALT_SIZE + EXTERNAL_SALT_SIZE] = {
0}; 0};
size_t salt_len = 0; size_t salt_len = 0;
@ -465,8 +496,7 @@ static void derive_kek(uint32_t pin, const uint8_t *random_salt,
} }
PBKDF2_HMAC_SHA256_CTX ctx = {0}; PBKDF2_HMAC_SHA256_CTX ctx = {0};
pbkdf2_hmac_sha256_Init(&ctx, (const uint8_t *)&pin, sizeof(pin), salt, pbkdf2_hmac_sha256_Init(&ctx, pin, pin_len, salt, salt_len, 1);
salt_len, 1);
for (int i = 1; i <= 5; i++) { for (int i = 1; i <= 5; i++) {
pbkdf2_hmac_sha256_Update(&ctx, PIN_ITER_COUNT / 10); pbkdf2_hmac_sha256_Update(&ctx, PIN_ITER_COUNT / 10);
if (ui_callback && ui_message) { if (ui_callback && ui_message) {
@ -477,8 +507,7 @@ static void derive_kek(uint32_t pin, const uint8_t *random_salt,
} }
pbkdf2_hmac_sha256_Final(&ctx, kek); pbkdf2_hmac_sha256_Final(&ctx, kek);
pbkdf2_hmac_sha256_Init(&ctx, (const uint8_t *)&pin, sizeof(pin), salt, pbkdf2_hmac_sha256_Init(&ctx, pin, pin_len, salt, salt_len, 2);
salt_len, 2);
for (int i = 6; i <= 10; i++) { for (int i = 6; i <= 10; i++) {
pbkdf2_hmac_sha256_Update(&ctx, PIN_ITER_COUNT / 10); pbkdf2_hmac_sha256_Update(&ctx, PIN_ITER_COUNT / 10);
if (ui_callback && ui_message) { if (ui_callback && ui_message) {
@ -491,17 +520,11 @@ static void derive_kek(uint32_t pin, const uint8_t *random_salt,
ui_rem -= DERIVE_SECS; ui_rem -= DERIVE_SECS;
memzero(&ctx, sizeof(PBKDF2_HMAC_SHA256_CTX)); memzero(&ctx, sizeof(PBKDF2_HMAC_SHA256_CTX));
memzero(&pin, sizeof(pin));
memzero(&salt, sizeof(salt)); memzero(&salt, sizeof(salt));
} }
static secbool set_pin(uint32_t pin, const uint8_t *ext_salt) { static secbool set_pin(const uint8_t *pin, size_t pin_len,
// Fail if the PIN is the same as the wipe code. Ignore during upgrade. const uint8_t *ext_salt) {
if (norcow_active_version != 0 && sectrue != is_not_wipe_code(pin)) {
memzero(&pin, sizeof(pin));
return secfalse;
}
// Encrypt the cached keys using the new PIN and set the new PVC. // Encrypt the cached keys using the new PIN and set the new PVC.
uint8_t buffer[RANDOM_SALT_SIZE + KEYS_SIZE + POLY1305_TAG_SIZE] = {0}; uint8_t buffer[RANDOM_SALT_SIZE + KEYS_SIZE + POLY1305_TAG_SIZE] = {0};
uint8_t *rand_salt = buffer; uint8_t *rand_salt = buffer;
@ -512,7 +535,7 @@ static secbool set_pin(uint32_t pin, const uint8_t *ext_salt) {
uint8_t keiv[SHA256_DIGEST_LENGTH] = {0}; uint8_t keiv[SHA256_DIGEST_LENGTH] = {0};
chacha20poly1305_ctx ctx = {0}; chacha20poly1305_ctx ctx = {0};
random_buffer(rand_salt, RANDOM_SALT_SIZE); random_buffer(rand_salt, RANDOM_SALT_SIZE);
derive_kek(pin, rand_salt, ext_salt, kek, keiv); derive_kek(pin, pin_len, rand_salt, ext_salt, kek, keiv);
rfc7539_init(&ctx, kek, keiv); rfc7539_init(&ctx, kek, keiv);
memzero(kek, sizeof(kek)); memzero(kek, sizeof(kek));
memzero(keiv, sizeof(keiv)); memzero(keiv, sizeof(keiv));
@ -524,14 +547,13 @@ static secbool set_pin(uint32_t pin, const uint8_t *ext_salt) {
memzero(buffer, sizeof(buffer)); memzero(buffer, sizeof(buffer));
if (ret == sectrue) { if (ret == sectrue) {
if (pin == PIN_EMPTY) { if (pin_len == 0) {
ret = norcow_set(PIN_NOT_SET_KEY, &TRUE_BYTE, sizeof(TRUE_BYTE)); ret = norcow_set(PIN_NOT_SET_KEY, &TRUE_BYTE, sizeof(TRUE_BYTE));
} else { } else {
ret = norcow_set(PIN_NOT_SET_KEY, &FALSE_BYTE, sizeof(FALSE_BYTE)); ret = norcow_set(PIN_NOT_SET_KEY, &FALSE_BYTE, sizeof(FALSE_BYTE));
} }
} }
memzero(&pin, sizeof(pin));
return ret; return ret;
} }
@ -637,15 +659,18 @@ static void init_wiped_storage(void) {
ensure(auth_init(), "set_storage_auth_tag failed"); ensure(auth_init(), "set_storage_auth_tag failed");
ensure(storage_set_encrypted(VERSION_KEY, &version, sizeof(version)), ensure(storage_set_encrypted(VERSION_KEY, &version, sizeof(version)),
"set_storage_version failed"); "set_storage_version failed");
ensure(norcow_set(UNAUTH_VERSION_KEY, &version, sizeof(version)),
"set_unauth_storage_version failed");
ensure(norcow_set(STORAGE_UPGRADED_KEY, &FALSE_WORD, sizeof(FALSE_WORD)), ensure(norcow_set(STORAGE_UPGRADED_KEY, &FALSE_WORD, sizeof(FALSE_WORD)),
"set_storage_not_upgraded failed"); "set_storage_not_upgraded failed");
ensure(pin_logs_init(0), "init_pin_logs failed"); ensure(pin_logs_init(0), "init_pin_logs failed");
ensure(set_wipe_code(WIPE_CODE_EMPTY), "set_wipe_code failed"); ensure(set_wipe_code(WIPE_CODE_EMPTY, WIPE_CODE_EMPTY_LEN),
"set_wipe_code failed");
ui_total = DERIVE_SECS; ui_total = DERIVE_SECS;
ui_rem = ui_total; ui_rem = ui_total;
ui_message = PROCESSING_MSG; ui_message = PROCESSING_MSG;
ensure(set_pin(PIN_EMPTY, NULL), "init_pin failed"); ensure(set_pin(PIN_EMPTY, PIN_EMPTY_LEN, NULL), "init_pin failed");
} }
void storage_init(PIN_UI_WAIT_CALLBACK callback, const uint8_t *salt, void storage_init(PIN_UI_WAIT_CALLBACK callback, const uint8_t *salt,
@ -861,6 +886,18 @@ void storage_lock(void) {
memzero(authentication_sum, sizeof(authentication_sum)); memzero(authentication_sum, sizeof(authentication_sum));
} }
// Returns the storage version that was used to lock the storage.
static uint32_t get_lock_version(void) {
const void *val = NULL;
uint16_t len = 0;
if (sectrue != norcow_get(UNAUTH_VERSION_KEY, &val, &len) ||
len != sizeof(uint32_t)) {
handle_fault("no lock version");
}
return *(uint32_t *)val;
}
secbool check_storage_version(void) { secbool check_storage_version(void) {
uint32_t version = 0; uint32_t version = 0;
uint16_t len = 0; uint16_t len = 0;
@ -870,12 +907,19 @@ secbool check_storage_version(void) {
handle_fault("storage version check"); handle_fault("storage version check");
return secfalse; return secfalse;
} }
if (version != get_lock_version()) {
handle_fault("storage version check");
return secfalse;
}
const void *storage_upgraded = NULL; const void *storage_upgraded = NULL;
if (sectrue != norcow_get(STORAGE_UPGRADED_KEY, &storage_upgraded, &len) || if (sectrue != norcow_get(STORAGE_UPGRADED_KEY, &storage_upgraded, &len) ||
len != sizeof(TRUE_WORD)) { len != sizeof(TRUE_WORD)) {
handle_fault("storage version check"); handle_fault("storage version check");
return secfalse; return secfalse;
} }
if (version > norcow_active_version) { if (version > norcow_active_version) {
// Attack: Storage was downgraded. // Attack: Storage was downgraded.
storage_wipe(); storage_wipe();
@ -892,6 +936,8 @@ secbool check_storage_version(void) {
norcow_set(STORAGE_UPGRADED_KEY, &FALSE_WORD, sizeof(FALSE_WORD)); norcow_set(STORAGE_UPGRADED_KEY, &FALSE_WORD, sizeof(FALSE_WORD));
storage_set_encrypted(VERSION_KEY, &norcow_active_version, storage_set_encrypted(VERSION_KEY, &norcow_active_version,
sizeof(norcow_active_version)); sizeof(norcow_active_version));
norcow_set(UNAUTH_VERSION_KEY, &norcow_active_version,
sizeof(norcow_active_version));
} else { } else {
// Standard operation. The storage was neither upgraded nor downgraded. // Standard operation. The storage was neither upgraded nor downgraded.
if (*(const uint32_t *)storage_upgraded != FALSE_WORD) { if (*(const uint32_t *)storage_upgraded != FALSE_WORD) {
@ -939,23 +985,41 @@ static secbool decrypt_dek(const uint8_t *kek, const uint8_t *keiv) {
memcpy(cached_keys, keys, sizeof(keys)); memcpy(cached_keys, keys, sizeof(keys));
memzero(keys, sizeof(keys)); memzero(keys, sizeof(keys));
memzero(tag, sizeof(tag)); memzero(tag, sizeof(tag));
// Check that the authenticated version number matches the norcow version. return sectrue;
// NOTE: This also initializes the authentication_sum by calling
// storage_get_encrypted() which calls auth_get().
return check_storage_version();
} }
static secbool unlock(uint32_t pin, const uint8_t *ext_salt) { static void ensure_not_wipe_code(const uint8_t *pin, size_t pin_len) {
if (sectrue != initialized || pin == PIN_INVALID) { if (sectrue != is_not_wipe_code(pin, pin_len)) {
return secfalse; storage_wipe();
error_shutdown("You have entered the", "wipe code. All private",
"data has been erased.", NULL);
}
}
static secbool unlock(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt) {
const uint8_t *unlock_pin = pin;
size_t unlock_pin_len = pin_len;
// In case of an upgrade from version 1 or 2, encode the PIN to the old format
// and bump the total time of UI progress to account for the set_pin() call in
// storage_upgrade_unlocked().
uint32_t legacy_pin = 0;
if (get_lock_version() <= 2) {
ui_total += DERIVE_SECS;
ui_rem += DERIVE_SECS;
legacy_pin = pin_to_int(pin, pin_len);
unlock_pin = (const uint8_t *)&legacy_pin;
unlock_pin_len = sizeof(legacy_pin);
} }
storage_ensure_not_wipe_code(pin); // Now we can check for wipe code.
ensure_not_wipe_code(unlock_pin, unlock_pin_len);
// Get the pin failure counter // Get the pin failure counter
uint32_t ctr = 0; uint32_t ctr = 0;
if (sectrue != pin_get_fails(&ctr)) { if (sectrue != pin_get_fails(&ctr)) {
memzero(&pin, sizeof(pin)); memzero(&legacy_pin, sizeof(legacy_pin));
return secfalse; return secfalse;
} }
@ -981,6 +1045,7 @@ static secbool unlock(uint32_t pin, const uint8_t *ext_salt) {
progress = ((ui_total - ui_rem) * 10 + i) * 100 / ui_total; progress = ((ui_total - ui_rem) * 10 + i) * 100 / ui_total;
} }
if (sectrue == ui_callback(ui_rem, progress, ui_message)) { if (sectrue == ui_callback(ui_rem, progress, ui_message)) {
memzero(&legacy_pin, sizeof(legacy_pin));
return secfalse; return secfalse;
} }
} }
@ -995,14 +1060,15 @@ static secbool unlock(uint32_t pin, const uint8_t *ext_salt) {
if (sectrue != initialized || if (sectrue != initialized ||
sectrue != norcow_get(EDEK_PVC_KEY, &rand_salt, &len) || sectrue != norcow_get(EDEK_PVC_KEY, &rand_salt, &len) ||
len != RANDOM_SALT_SIZE + KEYS_SIZE + PVC_SIZE) { len != RANDOM_SALT_SIZE + KEYS_SIZE + PVC_SIZE) {
memzero(&pin, sizeof(pin)); memzero(&legacy_pin, sizeof(legacy_pin));
handle_fault("no EDEK"); handle_fault("no EDEK");
return secfalse; return secfalse;
} }
uint8_t kek[SHA256_DIGEST_LENGTH] = {0}; uint8_t kek[SHA256_DIGEST_LENGTH] = {0};
uint8_t keiv[SHA256_DIGEST_LENGTH] = {0}; uint8_t keiv[SHA256_DIGEST_LENGTH] = {0};
derive_kek(pin, (const uint8_t *)rand_salt, ext_salt, kek, keiv); derive_kek(unlock_pin, unlock_pin_len, (const uint8_t *)rand_salt, ext_salt,
memzero(&pin, sizeof(pin)); kek, keiv);
memzero(&legacy_pin, sizeof(legacy_pin));
// First, we increase PIN fail counter in storage, even before checking the // First, we increase PIN fail counter in storage, even before checking the
// PIN. If the PIN is correct, we reset the counter afterwards. If not, we // PIN. If the PIN is correct, we reset the counter afterwards. If not, we
@ -1032,16 +1098,31 @@ static secbool unlock(uint32_t pin, const uint8_t *ext_salt) {
memzero(kek, sizeof(kek)); memzero(kek, sizeof(kek));
memzero(keiv, sizeof(keiv)); memzero(keiv, sizeof(keiv));
// Check for storage upgrades that need to be performed after unlocking and
// check that the authenticated version number matches the unauthenticated
// version and norcow version.
// NOTE: This also initializes the authentication_sum by calling
// storage_get_encrypted() which calls auth_get().
if (sectrue != storage_upgrade_unlocked(pin, pin_len, ext_salt) ||
sectrue != check_storage_version()) {
return secfalse;
}
unlocked = sectrue; unlocked = sectrue;
// Finally set the counter to 0 to indicate success. // Finally set the counter to 0 to indicate success.
return pin_fails_reset(); return pin_fails_reset();
} }
secbool storage_unlock(uint32_t pin, const uint8_t *ext_salt) { secbool storage_unlock(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt) {
if (sectrue != initialized || pin == NULL) {
return secfalse;
}
ui_total = DERIVE_SECS; ui_total = DERIVE_SECS;
ui_rem = ui_total; ui_rem = ui_total;
if (pin == PIN_EMPTY) { if (pin_len == 0) {
if (ui_message == NULL) { if (ui_message == NULL) {
ui_message = STARTING_MSG; ui_message = STARTING_MSG;
} else { } else {
@ -1050,7 +1131,7 @@ secbool storage_unlock(uint32_t pin, const uint8_t *ext_salt) {
} else { } else {
ui_message = VERIFYING_PIN_MSG; ui_message = VERIFYING_PIN_MSG;
} }
return unlock(pin, ext_salt); return unlock(pin, pin_len, ext_salt);
} }
/* /*
@ -1317,34 +1398,43 @@ uint32_t storage_get_pin_rem(void) {
return PIN_MAX_TRIES - ctr; return PIN_MAX_TRIES - ctr;
} }
secbool storage_change_pin(uint32_t oldpin, uint32_t newpin, secbool storage_change_pin(const uint8_t *oldpin, size_t oldpin_len,
const uint8_t *newpin, size_t newpin_len,
const uint8_t *old_ext_salt, const uint8_t *old_ext_salt,
const uint8_t *new_ext_salt) { const uint8_t *new_ext_salt) {
if (sectrue != initialized || oldpin == PIN_INVALID || if (sectrue != initialized || oldpin == NULL || newpin == NULL) {
newpin == PIN_INVALID) {
return secfalse; return secfalse;
} }
ui_total = 2 * DERIVE_SECS; ui_total = 2 * DERIVE_SECS;
ui_rem = ui_total; ui_rem = ui_total;
ui_message = (oldpin != PIN_EMPTY && newpin == PIN_EMPTY) ? VERIFYING_PIN_MSG ui_message =
: PROCESSING_MSG; (oldpin_len != 0 && newpin_len == 0) ? VERIFYING_PIN_MSG : PROCESSING_MSG;
if (sectrue != unlock(oldpin, old_ext_salt)) { if (sectrue != unlock(oldpin, oldpin_len, old_ext_salt)) {
return secfalse; return secfalse;
} }
secbool ret = set_pin(newpin, new_ext_salt);
memzero(&oldpin, sizeof(oldpin)); // Fail if the new PIN is the same as the wipe code.
memzero(&newpin, sizeof(newpin)); if (sectrue != is_not_wipe_code(newpin, newpin_len)) {
return ret; return secfalse;
}
return set_pin(newpin, newpin_len, new_ext_salt);
} }
void storage_ensure_not_wipe_code(uint32_t pin) { void storage_ensure_not_wipe_code(const uint8_t *pin, size_t pin_len) {
if (sectrue != is_not_wipe_code(pin)) { // If we are unlocking the storage during upgrade from version 2 or lower,
storage_wipe(); // then encode the PIN to the old format.
error_shutdown("You have entered the", "wipe code. All private", uint32_t legacy_pin = 0;
"data has been erased.", NULL); if (get_lock_version() <= 2) {
legacy_pin = pin_to_int(pin, pin_len);
pin = (const uint8_t *)&legacy_pin;
pin_len = sizeof(legacy_pin);
} }
ensure_not_wipe_code(pin, pin_len);
memzero(&legacy_pin, sizeof(legacy_pin));
} }
secbool storage_has_wipe_code(void) { secbool storage_has_wipe_code(void) {
@ -1352,29 +1442,28 @@ secbool storage_has_wipe_code(void) {
return secfalse; return secfalse;
} }
return is_not_wipe_code(WIPE_CODE_EMPTY); return is_not_wipe_code(WIPE_CODE_EMPTY, WIPE_CODE_EMPTY_LEN);
} }
secbool storage_change_wipe_code(uint32_t pin, const uint8_t *ext_salt, secbool storage_change_wipe_code(const uint8_t *pin, size_t pin_len,
uint32_t wipe_code) { const uint8_t *ext_salt,
if (sectrue != initialized || (pin != PIN_EMPTY && pin == wipe_code) || const uint8_t *wipe_code,
pin == PIN_INVALID || wipe_code == PIN_INVALID) { size_t wipe_code_len) {
memzero(&pin, sizeof(pin)); if (sectrue != initialized || pin == NULL || wipe_code == NULL ||
memzero(&wipe_code, sizeof(wipe_code)); (pin_len != 0 && pin_len == wipe_code_len &&
memcmp(pin, wipe_code, pin_len) == 0)) {
return secfalse; return secfalse;
} }
ui_total = DERIVE_SECS; ui_total = DERIVE_SECS;
ui_rem = ui_total; ui_rem = ui_total;
ui_message = (pin != PIN_EMPTY && wipe_code == PIN_EMPTY) ? VERIFYING_PIN_MSG ui_message =
: PROCESSING_MSG; (pin_len != 0 && wipe_code_len == 0) ? VERIFYING_PIN_MSG : PROCESSING_MSG;
secbool ret = secfalse; secbool ret = secfalse;
if (sectrue == unlock(pin, ext_salt)) { if (sectrue == unlock(pin, pin_len, ext_salt)) {
ret = set_wipe_code(wipe_code); ret = set_wipe_code(wipe_code, wipe_code_len);
} }
memzero(&pin, sizeof(pin));
memzero(&wipe_code, sizeof(wipe_code));
return ret; return ret;
} }
@ -1450,7 +1539,59 @@ static secbool v0_pin_get_fails(uint32_t *ctr) {
return sectrue; return sectrue;
} }
// Legacy conversion of PIN to the uint32 scheme that was used prior to storage
// version 3.
static uint32_t pin_to_int(const uint8_t *pin, size_t pin_len) {
if (pin_len > V0_MAX_PIN_LEN) {
return 0;
}
uint32_t val = 1;
size_t i = 0;
for (i = 0; i < pin_len; ++i) {
if (pin[i] < '0' || pin[i] > '9') {
return 0;
}
val = 10 * val + pin[i] - '0';
}
return val;
}
// Legacy conversion of wipe code from the uint32 scheme that was used prior to
// storage version 3.
static char *int_to_wipe_code(uint32_t val) {
static char wipe_code[V0_MAX_PIN_LEN + 1] = {0};
size_t pos = sizeof(wipe_code) - 1;
wipe_code[pos] = '\0';
// Handle the special representation of an empty wipe code.
if (val == V2_WIPE_CODE_EMPTY) {
return &wipe_code[pos];
}
if (val == V0_PIN_EMPTY) {
return NULL;
}
// Convert a non-empty wipe code.
while (val != 1) {
if (pos == 0) {
return NULL;
}
pos--;
wipe_code[pos] = '0' + (val % 10);
val /= 10;
}
return &wipe_code[pos];
}
static secbool storage_upgrade(void) { static secbool storage_upgrade(void) {
// Storage version 0: plaintext norcow
// Storage version 1: encrypted norcow
// Storage version 2: adds 9 digit wipe code
// Storage version 3: adds variable length PIN and wipe code
const uint16_t V0_PIN_KEY = 0x0000; const uint16_t V0_PIN_KEY = 0x0000;
const uint16_t V0_PIN_FAIL_KEY = 0x0001; const uint16_t V0_PIN_FAIL_KEY = 0x0001;
uint16_t key = 0; uint16_t key = 0;
@ -1475,10 +1616,12 @@ static secbool storage_upgrade(void) {
ui_total = DERIVE_SECS; ui_total = DERIVE_SECS;
ui_rem = ui_total; ui_rem = ui_total;
ui_message = PROCESSING_MSG; ui_message = PROCESSING_MSG;
if (sectrue == norcow_get(V0_PIN_KEY, &val, &len)) { secbool found = norcow_get(V0_PIN_KEY, &val, &len);
set_pin(*(const uint32_t *)val, NULL); if (sectrue == found && *(const uint32_t *)val != V0_PIN_EMPTY) {
set_pin((const uint8_t *)val, len, NULL);
} else { } else {
set_pin(PIN_EMPTY, NULL); set_pin((const uint8_t *)&V0_PIN_EMPTY, sizeof(V0_PIN_EMPTY), NULL);
ret = norcow_set(PIN_NOT_SET_KEY, &TRUE_BYTE, sizeof(TRUE_BYTE));
} }
// Convert PIN failure counter. // Convert PIN failure counter.
@ -1516,17 +1659,75 @@ static secbool storage_upgrade(void) {
} }
} }
// Set wipe code.
if (norcow_active_version <= 1) { if (norcow_active_version <= 1) {
if (sectrue != set_wipe_code(WIPE_CODE_EMPTY)) { if (sectrue != set_wipe_code(WIPE_CODE_EMPTY, WIPE_CODE_EMPTY_LEN)) {
return secfalse; return secfalse;
} }
} }
if (sectrue != if (norcow_active_version <= 2) {
norcow_set(STORAGE_UPGRADED_KEY, &TRUE_WORD, sizeof(TRUE_WORD))) { // Set UNAUTH_VERSION_KEY, so that it matches VERSION_KEY.
return secfalse; uint32_t version = 1;
// The storage may have gone through an upgrade to version 2 without having
// been unlocked. We can tell by looking at STORAGE_UPGRADED_KEY.
if (sectrue == norcow_get(STORAGE_UPGRADED_KEY, &val, &len) &&
len == sizeof(FALSE_WORD) && *((uint32_t *)val) == FALSE_WORD) {
version = 2;
}
if (sectrue != norcow_set(UNAUTH_VERSION_KEY, &version, sizeof(version))) {
return secfalse;
}
} }
norcow_set(STORAGE_UPGRADED_KEY, &TRUE_WORD, sizeof(TRUE_WORD));
norcow_active_version = NORCOW_VERSION; norcow_active_version = NORCOW_VERSION;
return norcow_upgrade_finish(); return norcow_upgrade_finish();
} }
static secbool storage_upgrade_unlocked(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt) {
uint32_t version = 0;
uint16_t len = 0;
if (sectrue !=
storage_get_encrypted(VERSION_KEY, &version, sizeof(version), &len) ||
len != sizeof(version)) {
handle_fault("storage version check");
return secfalse;
}
secbool ret = sectrue;
if (version <= 2) {
// Upgrade EDEK_PVC_KEY from the old uint32 PIN scheme to the new
// variable-length PIN scheme.
if (sectrue != set_pin(pin, pin_len, ext_salt)) {
return secfalse;
}
}
if (version == 2) {
// Upgrade WIPE_CODE_DATA_KEY from the old uint32 scheme to the new
// variable-length scheme.
const void *wipe_code_data = NULL;
if (sectrue != norcow_get(WIPE_CODE_DATA_KEY, &wipe_code_data, &len) ||
len < sizeof(uint32_t)) {
handle_fault("no wipe code");
return secfalse;
}
char *wipe_code = int_to_wipe_code(*(uint32_t *)wipe_code_data);
if (wipe_code == NULL) {
handle_fault("invalid wipe code");
return secfalse;
}
size_t wipe_code_len = strnlen(wipe_code, V0_MAX_PIN_LEN);
ret = set_wipe_code((const uint8_t *)wipe_code, wipe_code_len);
memzero(wipe_code, wipe_code_len);
}
return ret;
}

18
storage/storage.h
View File

@ -37,6 +37,10 @@
// Mask for extracting the "real" app_id. // Mask for extracting the "real" app_id.
#define FLAGS_APPID 0x3F #define FLAGS_APPID 0x3F
// The PIN value corresponding to an empty PIN.
extern const uint8_t *PIN_EMPTY;
#define PIN_EMPTY_LEN 0
typedef secbool (*PIN_UI_WAIT_CALLBACK)(uint32_t wait, uint32_t progress, typedef secbool (*PIN_UI_WAIT_CALLBACK)(uint32_t wait, uint32_t progress,
const char *message); const char *message);
@ -45,17 +49,21 @@ void storage_init(PIN_UI_WAIT_CALLBACK callback, const uint8_t *salt,
void storage_wipe(void); void storage_wipe(void);
secbool storage_is_unlocked(void); secbool storage_is_unlocked(void);
void storage_lock(void); void storage_lock(void);
secbool storage_unlock(uint32_t pin, const uint8_t *ext_salt); secbool storage_unlock(const uint8_t *pin, size_t pin_len,
const uint8_t *ext_salt);
secbool storage_has_pin(void); secbool storage_has_pin(void);
secbool storage_pin_fails_increase(void); secbool storage_pin_fails_increase(void);
uint32_t storage_get_pin_rem(void); uint32_t storage_get_pin_rem(void);
secbool storage_change_pin(uint32_t oldpin, uint32_t newpin, secbool storage_change_pin(const uint8_t *oldpin, size_t oldpin_len,
const uint8_t *newpin, size_t newpin_len,
const uint8_t *old_ext_salt, const uint8_t *old_ext_salt,
const uint8_t *new_ext_salt); const uint8_t *new_ext_salt);
void storage_ensure_not_wipe_code(uint32_t pin); void storage_ensure_not_wipe_code(const uint8_t *pin, size_t pin_len);
secbool storage_has_wipe_code(void); secbool storage_has_wipe_code(void);
secbool storage_change_wipe_code(uint32_t pin, const uint8_t *ext_salt, secbool storage_change_wipe_code(const uint8_t *pin, size_t pin_len,
uint32_t wipe_code); const uint8_t *ext_salt,
const uint8_t *wipe_code,
size_t wipe_code_len);
secbool storage_has(const uint16_t key); secbool storage_has(const uint16_t key);
secbool storage_get(const uint16_t key, void *val, const uint16_t max_len, secbool storage_get(const uint16_t key, void *val, const uint16_t max_len,
uint16_t *len); uint16_t *len);

2
storage/tests/c/norcow_config.h
View File

@ -42,6 +42,6 @@
/* /*
* Current storage version. * Current storage version.
*/ */
#define NORCOW_VERSION ((uint32_t)0x00000002) #define NORCOW_VERSION ((uint32_t)0x00000003)
#endif #endif