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Allow Devicekey::generate_root_of_trust() to define key size. #12823

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Merged
merged 1 commit into from
Apr 30, 2020
Merged

Allow Devicekey::generate_root_of_trust() to define key size. #12823

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12 changes: 8 additions & 4 deletions features/device_key/source/DeviceKey.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,7 @@ int DeviceKey::get_derived_key(uint32_t *ikey_buff, size_t ikey_size, const unsi
return DEVICEKEY_SUCCESS;
}

int DeviceKey::generate_root_of_trust()
int DeviceKey::generate_root_of_trust(size_t key_size)
{
int ret = DEVICEKEY_GENERATE_RANDOM_ERROR;
uint32_t key_buff[DEVICE_KEY_32BYTE / sizeof(uint32_t)];
Expand All @@ -255,12 +255,16 @@ int DeviceKey::generate_root_of_trust()
return DEVICEKEY_ALREADY_EXIST;
}

if (key_size != DEVICE_KEY_32BYTE && key_size != DEVICE_KEY_16BYTE) {
return DEVICEKEY_INVALID_KEY_SIZE;
}

#if defined(DEVICE_TRNG) || defined(MBEDTLS_ENTROPY_NV_SEED) || defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
mbedtls_entropy_context *entropy = new mbedtls_entropy_context;
mbedtls_entropy_init(entropy);
memset(key_buff, 0, actual_size);
memset(key_buff, 0, key_size);

ret = mbedtls_entropy_func(entropy, (unsigned char *)key_buff, actual_size);
ret = mbedtls_entropy_func(entropy, (unsigned char *)key_buff, key_size);
if (ret != MBED_SUCCESS) {
ret = DEVICEKEY_GENERATE_RANDOM_ERROR;
} else {
Expand All @@ -271,7 +275,7 @@ int DeviceKey::generate_root_of_trust()
delete entropy;

if (ret == DEVICEKEY_SUCCESS) {
ret = device_inject_root_of_trust(key_buff, actual_size);
ret = device_inject_root_of_trust(key_buff, key_size);
}
#endif

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13 changes: 8 additions & 5 deletions features/device_key/source/DeviceKey.h
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Expand Up @@ -110,12 +110,15 @@ class DeviceKey : private mbed::NonCopyable<DeviceKey> {
* Uses TRNG or various other entropy sources to generate random device key and
* inject it into device's KVStore. Device Key can only be generated once.
*
* \return DEVICEKEY_SUCCESS, when device key successfully generated and injected.
* \return DEVICEKEY_ALREADY_EXIST, if the key has already been written.
* \return DEVICEKEY_GENERATE_RANDOM_ERROR if this device does not contain entropy sources and cannot generate a key.
* \return error codes on other failures.
* @param key_size Size of key in bytes to generate. Must be 16 bytes or 32 bytes. Default is 16 bytes.
*
* @return DEVICEKEY_SUCCESS, when device key successfully generated and injected.
* @return DEVICEKEY_ALREADY_EXIST, if the key has already been written.
* @return DEVICEKEY_GENERATE_RANDOM_ERROR if this device does not contain entropy sources and cannot generate a key.
* @return DEVICEKEY_INVALID_KEY_SIZE if key_size is not 32 or 16 bytes.
* @return error codes on other failures.
*/
int generate_root_of_trust();
int generate_root_of_trust(size_t key_size = DEVICE_KEY_16BYTE);

private:
// Private constructor, as class is a singleton
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