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Key derivation: forbid output_key without input_key

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If none of the inputs to a key derivation is a
PSA_KEY_DERIVATION_INPUT_SECRET passed with
psa_key_derivation_input_key(), forbid
psa_key_derivation_output_key(). It usually doesn't make sense to
derive a key object if the secret isn't itself a proper key.
This commit is contained in:
Gilles Peskine
2019-09-24 18:21:06 +02:00
parent 1a2904c49a
commit 178c9aa966
5 changed files with 53 additions and 6 deletions
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8
include/psa/crypto.h
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@ -3527,6 +3527,11 @@ psa_status_t psa_key_derivation_output_bytes(
* In all cases, the data that is read is discarded from the operation.
* The operation's capacity is decreased by the number of bytes read.
*
* For algorithms that take an input step #PSA_KEY_DERIVATION_INPUT_SECRET,
* the input to that step must be provided with psa_key_derivation_input_key().
* Future versions of this specification may include additional restrictions
* on the derived key based on the attributes and strength of the secret key.
*
* \param[in] attributes The attributes for the new key.
* \param[in,out] operation The key derivation operation object to read from.
* \param[out] handle On success, a handle to the newly created key.
@ -3549,6 +3554,9 @@ psa_status_t psa_key_derivation_output_bytes(
* implementation in general or in this particular location.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* The provided key attributes are not valid for the operation.
* \retval #PSA_ERROR_NOT_PERMITTED
* The #PSA_KEY_DERIVATION_INPUT_SECRET input was not provided through
* a key.
* \retval #PSA_ERROR_BAD_STATE
* The operation state is not valid (it must be active and completed
* all required input steps).

3
include/psa/crypto_struct.h
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@ -255,6 +255,7 @@ typedef struct psa_tls12_prf_key_derivation_s
struct psa_key_derivation_s
{
psa_algorithm_t alg;
unsigned int can_output_key : 1;
size_t capacity;
union
{
@ -268,7 +269,7 @@ struct psa_key_derivation_s
};
/* This only zeroes out the first byte in the union, the rest is unspecified. */
#define PSA_KEY_DERIVATION_OPERATION_INIT {0, 0, {0}}
#define PSA_KEY_DERIVATION_OPERATION_INIT {0, 0, 0, {0}}
static inline struct psa_key_derivation_s psa_key_derivation_operation_init( void )
{
const struct psa_key_derivation_s v = PSA_KEY_DERIVATION_OPERATION_INIT;

6
include/psa/crypto_values.h
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@ -1622,7 +1622,11 @@
* (passed to psa_key_derivation_input_key())
* or the shared secret resulting from a key agreement
* (obtained via psa_key_derivation_key_agreement()).
* It can also be a direct input (passed to key_derivation_input_bytes()).
*
* The secret can also be a direct input (passed to
* key_derivation_input_bytes()). In this case, the derivation operation
* may not be used to derive keys: the operation will only allow
* psa_key_derivation_output_bytes(), not psa_key_derivation_output_key().
*/
#define PSA_KEY_DERIVATION_INPUT_SECRET ((psa_key_derivation_step_t)0x0101)