diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 998b092b9a..d02f3ff847 100755
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -54,43 +54,206 @@ typedef enum {
/** The action was completed successfully. */
PSA_SUCCESS = 0,
/** The requested operation or a parameter is not supported
- by this implementation. */
+ * by this implementation.
+ *
+ * Implementations should return this error code when an enumeration
+ * parameter such as a key type, algorithm, etc. is not recognized.
+ * If a combination of parameters is recognized and identified as
+ * not valid, return #PSA_ERROR_INVALID_ARGUMENT instead. */
PSA_ERROR_NOT_SUPPORTED,
- /** The requested action is denied by a policy. */
+ /** The requested action is denied by a policy.
+ *
+ * Implementations should return this error code when the parameters
+ * are recognized as valid and supported, and a policy explicitly
+ * denies the requested operation.
+ *
+ * If a subset of the parameters of a function call identify a
+ * forbidden operation, and another subset of the parameters are
+ * not valid or not supported, it is unspecified whether the function
+ * returns #PSA_ERROR_NOT_PERMITTED, #PSA_ERROR_NOT_SUPPORTED or
+ * #PSA_ERROR_INVALID_ARGUMENT. */
PSA_ERROR_NOT_PERMITTED,
- /** An output buffer is too small. */
+ /** An output buffer is too small.
+ *
+ * Applications can call the `PSA_xxx_SIZE` macro listed in the function
+ * description to determine a sufficient buffer size.
+ *
+ * Implementations should preferably return this error code only
+ * in cases when performing the operation with a larger output
+ * buffer would succeed. However implementations may return this
+ * error if a function has invalid or unsupported parameters in addition
+ * to the parameters that determine the necessary output buffer size. */
PSA_ERROR_BUFFER_TOO_SMALL,
/** A slot is occupied, but must be empty to carry out the
- requested action. */
+ * requested action.
+ *
+ * If the slot number is invalid (i.e. the requested action could
+ * not be performed even after erasing the slot's content),
+ * implementations shall return #PSA_ERROR_INVALID_ARGUMENT instead. */
PSA_ERROR_OCCUPIED_SLOT,
/** A slot is empty, but must be occupied to carry out the
- requested action. */
+ * requested action.
+ *
+ * If the slot number is invalid (i.e. the requested action could
+ * not be performed even after creating appropriate content in the slot),
+ * implementations shall return #PSA_ERROR_INVALID_ARGUMENT instead. */
PSA_ERROR_EMPTY_SLOT,
- /** The requested action cannot be performed in the current state. */
+ /** The requested action cannot be performed in the current state.
+ *
+ * Multipart operations return this error when one of the
+ * functions is called out of sequence. Refer to the function
+ * descriptions for permitted sequencing of functions.
+ *
+ * Implementations shall not return this error code to indicate
+ * that a key slot is occupied when it needs to be free or vice versa,
+ * but shall return #PSA_ERROR_OCCUPIED_SLOT or #PSA_ERROR_EMPTY_SLOT
+ * as applicable. */
PSA_ERROR_BAD_STATE,
- /** The parameters passed to the function are invalid. */
+ /** The parameters passed to the function are invalid.
+ *
+ * Implementations may return this error any time a parameter or
+ * combination of parameters are recognized as invalid.
+ *
+ * Implementations shall not return this error code to indicate
+ * that a key slot is occupied when it needs to be free or vice versa,
+ * but shall return #PSA_ERROR_OCCUPIED_SLOT or #PSA_ERROR_EMPTY_SLOT
+ * as applicable. */
PSA_ERROR_INVALID_ARGUMENT,
- /** There is not enough runtime memory. */
+ /** There is not enough runtime memory.
+ *
+ * If the action is carried out across multiple security realms, this
+ * error can refer to available memory in any of the security realms. */
PSA_ERROR_INSUFFICIENT_MEMORY,
- /** There is not enough persistent storage. */
+ /** There is not enough persistent storage.
+ *
+ * Functions that modify the key storage return this error code if
+ * there is insufficient storage space on the host media. In addition,
+ * many functions that do not otherwise access storage may return this
+ * error code if the implementation requires a mandatory log entry for
+ * the requested action and the log storage space is full. */
PSA_ERROR_INSUFFICIENT_STORAGE,
- /** There was a communication failure inside the implementation. */
+ /** There was a communication failure inside the implementation.
+ *
+ * This can indicate a communication failure between the application
+ * and an external cryptoprocessor or between the cryptoprocessor and
+ * an external volatile or persistent memory. A communication failure
+ * may be transient or permanent depending on the cause.
+ *
+ * \warning If a function returns this error, it is undetermined
+ * whether the requested action has completed or not. Implementations
+ * should return #PSA_SUCCESS on successful completion whenver
+ * possible, however functions may return #PSA_ERROR_COMMUNICATION_FAILURE
+ * if the requested action was completed successfully in an external
+ * cryptoprocessor but there was a breakdown of communication before
+ * the cryptoprocessor could report the status to the application.
+ */
PSA_ERROR_COMMUNICATION_FAILURE,
- /** There was a storage failure that may have led to data loss. */
+ /** There was a storage failure that may have led to data loss.
+ *
+ * This error indicates that some persistent storage is corrupted.
+ * It should not be used for a corruption of volatile memory
+ * (use #PSA_ERROR_TAMPERING_DETECTED), for a communication error
+ * between the cryptoprocessor and its external storage (use
+ * #PSA_ERROR_COMMUNICATION_FAILURE), or when the storage is
+ * in a valid state but is full (use #PSA_ERROR_INSUFFICIENT_STORAGE).
+ *
+ * Note that a storage failure does not indicate that any data that was
+ * previously read is invalid. However this previously read data may no
+ * longer be readable from storage.
+ *
+ * When a storage failure occurs, it is no longer possible to ensure
+ * the global integrity of the keystore. Depending on the global
+ * integrity guarantees offered by the implementation, access to other
+ * data may or may not fail even if the data is still readable but
+ * its integrity canont be guaranteed.
+ *
+ * Implementations should only use this error code to report a
+ * permanent storage corruption. However application writers should
+ * keep in mind that transient errors while reading the storage may be
+ * reported using this error code. */
PSA_ERROR_STORAGE_FAILURE,
- /** A hardware failure was detected. */
+ /** A hardware failure was detected.
+ *
+ * A hardware failure may be transient or permanent depending on the
+ * cause. */
PSA_ERROR_HARDWARE_FAILURE,
- /** A tampering attempt was detected. */
+ /** A tampering attempt was detected.
+ *
+ * If an application receives this error code, there is no guarantee
+ * that previously accessed or computed data was correct and remains
+ * confidential. Applications should not perform any security function
+ * and should enter a safe failure state.
+ *
+ * Implementations may return this error code if they detect an invalid
+ * state that cannot happen during normal operation and that indicates
+ * that the implementation's security guarantees no longer hold. Depending
+ * on the implementation architecture and on its security and safety goals,
+ * the implementation may forcibly terminate the application.
+ *
+ * This error code is intended as a last resort when a security breach
+ * is detected and it is unsure whether the keystore data is still
+ * protected. Implementations shall only return this error code
+ * to report an alarm from a tampering detector, to indicate that
+ * the confidentiality of stored data can no longer be guaranteed,
+ * or to indicate that the integrity of previously returned data is now
+ * considered compromised. Implementations shall not use this error code
+ * to indicate a hardware failure that merely makes it impossible to
+ * perform the requested operation (use #PSA_ERROR_COMMUNICATION_FAILURE,
+ * #PSA_ERROR_STORAGE_FAILURE, #PSA_ERROR_HARDWARE_FAILURE,
+ * #PSA_ERROR_INSUFFICIENT_ENTROPY or other applicable error code
+ * instead).
+ *
+ * This error indicates an attack against the application. Implementations
+ * shall not return this error code as a consequence of the behavior of
+ * the application itself. */
PSA_ERROR_TAMPERING_DETECTED,
/** There is not enough entropy to generate random data needed
- for the requested action. */
+ * for the requested action.
+ *
+ * This error indicates a failure of a hardware random generator.
+ * Application writers should note that this error can be returned not
+ * only by functions whose purpose is to generate random data, such
+ * as key, IV or nonce generation, but also by functions that execute
+ * an algorithm with a randomized result, as well as functions that
+ * use randomization of intermediate computations as a countermeasure
+ * to certain attacks.
+ *
+ * Implementations should avoid returning this error after psa_crypto_init()
+ * has succeeded. Implementations should generate sufficient
+ * entropy during initialization and subsequently use a cryptographically
+ * secure pseudorandom generator (PRNG). However implementations may return
+ * this error at any time if a policy requires the PRNG to be reseeded
+ * during normal operation. */
PSA_ERROR_INSUFFICIENT_ENTROPY,
- /** The signature, MAC or hash is incorrect. */
+ /** The signature, MAC or hash is incorrect.
+ *
+ * Verification functions return this error if the verification
+ * calculations completed successfully, and the value to be verified
+ * was determined to be incorrect.
+ *
+ * If the value to verify has an invalid size, implementations may return
+ * either #PSA_ERROR_INVALID_ARGUMENT or #PSA_ERROR_INVALID_SIGNATURE. */
PSA_ERROR_INVALID_SIGNATURE,
- /** The decrypted padding is incorrect. */
+ /** The decrypted padding is incorrect.
+ *
+ * \warning In some protocols, when decrypting data, it is essential that
+ * the behavior of the application does not depend on whether the padding
+ * is correct, down to precise timing. Applications should prefer
+ * protocols that use authenticated encryption rather than plain
+ * encryption. If the application must perform a decryption of
+ * unauthenticated data, the application writer should take care not
+ * to reveal whether the padding is invalid.
+ *
+ * Implementations should strive to make valid and invalid padding
+ * as close as possible to indistinguishable to an external observer.
+ * In particular, the timing of a decryption operation should not
+ * depend on the validity of the padding. */
PSA_ERROR_INVALID_PADDING,
/** An error occurred that does not correspond to any defined
- failure cause. */
+ * failure cause.
+ *
+ * Implementations may use this error code if none of the other standard
+ * error codes are applicable. */
PSA_ERROR_UNKNOWN_ERROR,
} psa_status_t;
@@ -141,15 +304,47 @@ typedef uint32_t psa_key_type_t;
#define PSA_KEY_TYPE_VENDOR_FLAG ((psa_key_type_t)0x80000000)
#define PSA_KEY_TYPE_CATEGORY_MASK ((psa_key_type_t)0x7e000000)
+/** Raw data.
+ *
+ * A "key" of this type cannot be used for any cryptographic operation.
+ * Applications may use this type to store arbitrary data in the keystore. */
#define PSA_KEY_TYPE_RAW_DATA ((psa_key_type_t)0x02000000)
#define PSA_KEY_TYPE_CATEGORY_SYMMETRIC ((psa_key_type_t)0x04000000)
#define PSA_KEY_TYPE_CATEGORY_ASYMMETRIC ((psa_key_type_t)0x06000000)
#define PSA_KEY_TYPE_PAIR_FLAG ((psa_key_type_t)0x01000000)
+/** HMAC key.
+ *
+ * The key policy determines which underlying hash algorithm the key can be
+ * used for.
+ *
+ * HMAC keys should generally have the same size as the underlying hash.
+ * This size can be calculated with `PSA_HASH_SIZE(alg)` where
+ * `alg` is the HMAC algorithm or the underlying hash algorithm. */
#define PSA_KEY_TYPE_HMAC ((psa_key_type_t)0x02000001)
+/** Key for an cipher, AEAD or MAC algorithm based on the AES block cipher.
+ *
+ * The size of the key can be 16 bytes (AES-128), 24 bytes (AES-192) or
+ * 32 bytes (AES-256).
+ */
#define PSA_KEY_TYPE_AES ((psa_key_type_t)0x04000001)
+/** Key for a cipher or MAC algorithm based on DES or 3DES (Triple-DES).
+ *
+ * The size of the key can be 8 bytes (single DES), 16 bytes (2-key 3DES) or
+ * 24 bytes (3-key 3DES).
+ *
+ * Note that single DES and 2-key 3DES are weak and strongly
+ * deprecated and should only be used to decrypt legacy data. 3-key 3DES
+ * is weak and deprecated and should only be used in legacy protocols.
+ */
#define PSA_KEY_TYPE_DES ((psa_key_type_t)0x04000002)
+/** Key for an cipher, AEAD or MAC algorithm based on the
+ * Camellia block cipher. */
#define PSA_KEY_TYPE_CAMELLIA ((psa_key_type_t)0x04000003)
+/** Key for the RC4 stream cipher.
+ *
+ * Note that RC4 is weak and deprecated and should only be used in
+ * legacy protocols. */
#define PSA_KEY_TYPE_ARC4 ((psa_key_type_t)0x04000004)
/** RSA public key. */
@@ -207,8 +402,14 @@ typedef uint32_t psa_key_type_t;
* \param type A cipher key type (value of type #psa_key_type_t).
*
* \return The block size for a block cipher, or 1 for a stream cipher.
- * The return value is undefined if \c type does not identify
- * a cipher algorithm.
+ * The return value is undefined if \c type is not a supported
+ * cipher key type.
+ *
+ * \note It is possible to build stream cipher algorithms on top of a block
+ * cipher, for example CTR mode (#PSA_ALG_CTR).
+ * This macro only takes the key type into account, so it cannot be
+ * used to determine the size of the data that #psa_cipher_update()
+ * might buffer for future processing in general.
*
* \note This macro returns a compile-time constant if its argument is one.
*
@@ -289,7 +490,17 @@ typedef uint32_t psa_algorithm_t;
#define PSA_ALG_MAC_SUBCATEGORY_MASK ((psa_algorithm_t)0x00c00000)
#define PSA_ALG_HMAC_BASE ((psa_algorithm_t)0x02800000)
-#define PSA_ALG_HMAC(hash_alg) \
+/** Macro to build an HMAC algorithm.
+ *
+ * For example, `PSA_ALG_HMAC(PSA_ALG_SHA256)` is HMAC-SHA-256.
+ *
+ * \param alg A hash algorithm (\c PSA_ALG_XXX value such that
+ * #PSA_ALG_IS_HASH(alg) is true).
+ *
+ * \return The corresponding HMAC algorithm.
+ * \return Unspecified if \p alg is not a hash algorithm.
+ */
+#define PSA_ALG_HMAC(hash_alg) \
(PSA_ALG_HMAC_BASE | ((hash_alg) & PSA_ALG_HASH_MASK))
#define PSA_ALG_HMAC_HASH(hmac_alg) \
(PSA_ALG_CATEGORY_HASH | ((hmac_alg) & PSA_ALG_HASH_MASK))
@@ -368,13 +579,15 @@ typedef uint32_t psa_algorithm_t;
* \retval PSA_SUCCESS
* Success.
* \retval PSA_ERROR_NOT_SUPPORTED
- * The key type or key size is not supported.
+ * The key type or key size is not supported, either by the
+ * implementation in general or in this particular slot.
* \retval PSA_ERROR_INVALID_ARGUMENT
* The key slot is invalid,
* or the key data is not correctly formatted.
* \retval PSA_ERROR_OCCUPIED_SLOT
- There is already a key in the specified slot.
+ * There is already a key in the specified slot.
* \retval PSA_ERROR_INSUFFICIENT_MEMORY
+ * \retval PSA_ERROR_INSUFFICIENT_STORAGE
* \retval PSA_ERROR_COMMUNICATION_FAILURE
* \retval PSA_ERROR_HARDWARE_FAILURE
* \retval PSA_ERROR_TAMPERING_DETECTED
@@ -385,13 +598,37 @@ psa_status_t psa_import_key(psa_key_slot_t key,
size_t data_length);
/**
- * \brief Destroy a key.
+ * \brief Destroy a key and restore the slot to its default state.
+ *
+ * This function destroys the content of the key slot from both volatile
+ * memory and, if applicable, non-volatile storage. Implementations shall
+ * make a best effort to ensure that any previous content of the slot is
+ * unrecoverable.
+ *
+ * This function also erases any metadata such as policies. It returns the
+ * specified slot to its default state.
+ *
+ * \param key The key slot to erase.
*
* \retval PSA_SUCCESS
- * \retval PSA_ERROR_EMPTY_SLOT
+ * The slot's content, if any, has been erased.
+ * \retval PSA_ERROR_NOT_PERMITTED
+ * The slot holds content and cannot be erased because it is
+ * read-only, either due to a policy or due to physical restrictions.
+ * \retval PSA_ERROR_INVALID_ARGUMENT
+ * The specified slot number does not designate a valid slot.
* \retval PSA_ERROR_COMMUNICATION_FAILURE
- * \retval PSA_ERROR_HARDWARE_FAILURE
+ * There was an failure in communication with the cryptoprocessor.
+ * The key material may still be present in the cryptoprocessor.
+ * \retval PSA_ERROR_STORAGE_FAILURE
+ * The storage is corrupted. Implementations shall make a best effort
+ * to erase key material even in this stage, however applications
+ * should be aware that it may be impossible to guarantee that the
+ * key material is not recoverable in such cases.
* \retval PSA_ERROR_TAMPERING_DETECTED
+ * An unexpected condition which is not a storage corruption or
+ * a communication failure occurred. The cryptoprocessor may have
+ * been compromised.
*/
psa_status_t psa_destroy_key(psa_key_slot_t key);
@@ -668,30 +905,32 @@ typedef struct psa_hash_operation_s psa_hash_operation_t;
* This is also the hash size that psa_hash_verify() expects.
*
* \param alg A hash algorithm (\c PSA_ALG_XXX value such that
- * #PSA_ALG_IS_HASH(alg) is true).
+ * #PSA_ALG_IS_HASH(alg) is true), or an HMAC algorithm
+ * (`PSA_ALG_HMAC(hash_alg)` where `hash_alg` is a
+ * hash algorithm).
*
* \return The hash size for the specified hash algorithm.
* If the hash algorithm is not recognized, return 0.
* An implementation may return either 0 or the correct size
* for a hash algorithm that it recognizes, but does not support.
*/
-#define PSA_HASH_FINAL_SIZE(alg) \
- ( \
- (alg) == PSA_ALG_MD2 ? 16 : \
- (alg) == PSA_ALG_MD4 ? 16 : \
- (alg) == PSA_ALG_MD5 ? 16 : \
- (alg) == PSA_ALG_RIPEMD160 ? 20 : \
- (alg) == PSA_ALG_SHA_1 ? 20 : \
- (alg) == PSA_ALG_SHA_224 ? 28 : \
- (alg) == PSA_ALG_SHA_256 ? 32 : \
- (alg) == PSA_ALG_SHA_384 ? 48 : \
- (alg) == PSA_ALG_SHA_512 ? 64 : \
- (alg) == PSA_ALG_SHA_512_224 ? 28 : \
- (alg) == PSA_ALG_SHA_512_256 ? 32 : \
- (alg) == PSA_ALG_SHA3_224 ? 28 : \
- (alg) == PSA_ALG_SHA3_256 ? 32 : \
- (alg) == PSA_ALG_SHA3_384 ? 48 : \
- (alg) == PSA_ALG_SHA3_512 ? 64 : \
+#define PSA_HASH_SIZE(alg) \
+ ( \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_MD2 ? 16 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_MD4 ? 16 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_MD5 ? 16 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_RIPEMD160 ? 20 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_1 ? 20 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_224 ? 28 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_256 ? 32 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_384 ? 48 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_512 ? 64 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_512_224 ? 28 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA_512_256 ? 32 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA3_224 ? 28 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA3_256 ? 32 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA3_384 ? 48 : \
+ PSA_ALG_RSA_GET_HASH(alg) == PSA_ALG_SHA3_512 ? 64 : \
0)
/** Start a multipart hash operation.
@@ -776,7 +1015,7 @@ psa_status_t psa_hash_update(psa_hash_operation_t *operation,
* \param hash_size Size of the \c hash buffer in bytes.
* \param hash_length On success, the number of bytes
* that make up the hash value. This is always
- * #PSA_HASH_FINAL_SIZE(alg) where \c alg is the
+ * #PSA_HASH_SIZE(alg) where \c alg is the
* hash algorithm that is calculated.
*
* \retval PSA_SUCCESS
@@ -785,7 +1024,7 @@ psa_status_t psa_hash_update(psa_hash_operation_t *operation,
* The operation state is not valid (not started, or already completed).
* \retval PSA_ERROR_BUFFER_TOO_SMALL
* The size of the \c hash buffer is too small. You can determine a
- * sufficient buffer size by calling #PSA_HASH_FINAL_SIZE(alg)
+ * sufficient buffer size by calling #PSA_HASH_SIZE(alg)
* where \c alg is the hash algorithm that is calculated.
* \retval PSA_ERROR_INSUFFICIENT_MEMORY
* \retval PSA_ERROR_COMMUNICATION_FAILURE
@@ -881,7 +1120,7 @@ typedef struct psa_mac_operation_s psa_mac_operation_t;
* for a MAC algorithm that it recognizes, but does not support.
*/
#define PSA_MAC_FINAL_SIZE(key_type, key_bits, alg) \
- (PSA_ALG_IS_HMAC(alg) ? PSA_HASH_FINAL_SIZE(PSA_ALG_HMAC_HASH(alg)) : \
+ (PSA_ALG_IS_HMAC(alg) ? PSA_HASH_SIZE(PSA_ALG_HMAC_HASH(alg)) : \
PSA_ALG_IS_BLOCK_CIPHER_MAC(alg) ? PSA_BLOCK_CIPHER_BLOCK_SIZE(key_type) : \
0)
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index e4f2a8722a..18126f638d 100755
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -388,9 +388,11 @@ psa_status_t psa_destroy_key(psa_key_slot_t key)
return( PSA_ERROR_INVALID_ARGUMENT );
slot = &global_data.key_slots[key];
if( slot->type == PSA_KEY_TYPE_NONE )
- return( PSA_ERROR_EMPTY_SLOT );
-
- if( PSA_KEY_TYPE_IS_RAW_BYTES( slot->type ) )
+ {
+ /* No key material to clean, but do zeroize the slot below to wipe
+ * metadata such as policies. */
+ }
+ else if( PSA_KEY_TYPE_IS_RAW_BYTES( slot->type ) )
{
mbedtls_free( slot->data.raw.data );
}
@@ -816,7 +818,7 @@ psa_status_t psa_hash_finish( psa_hash_operation_t *operation,
size_t *hash_length )
{
int ret;
- size_t actual_hash_length = PSA_HASH_FINAL_SIZE( operation->alg );
+ size_t actual_hash_length = PSA_HASH_SIZE( operation->alg );
/* Fill the output buffer with something that isn't a valid hash
* (barring an attack on the hash and deliberately-crafted input),