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Pass the key creation method to drivers

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Pass the key creation method (import/generate/derive/copy) to the
driver methods to allocate or validate a slot number. This allows
drivers to enforce policies such as "this key slot can only be used
for keys generated inside the secure element".
This commit is contained in:
Gilles Peskine 2019-08-05 16:44:14 +02:00
parent df17914e01
commit e88c2c1338
5 changed files with 47 additions and 24 deletions
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46
include/psa/crypto_se_driver.h
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@ -810,25 +810,45 @@ typedef struct {
*/
/**@{*/
/** An enumeration indicating how a key is created.
*/
typedef enum
{
PSA_KEY_CREATION_IMPORT, /**< During psa_import_key() */
PSA_KEY_CREATION_GENERATE, /**< During psa_generate_key() */
PSA_KEY_CREATION_DERIVE, /**< During psa_key_derivation_output_key() */
PSA_KEY_CREATION_COPY, /**< During psa_copy_key() */
} psa_key_creation_method_t;
/** \brief A function that allocates a slot for a key.
*
* To create a key in a specific slot in a secure element, the core
* first calls this function to determine a valid slot number,
* then calls a function to create the key material in that slot.
* For example, in nominal conditions (that is, if no error occurs),
* the effect of a call to psa_import_key() with a lifetime that places
* the key in a secure element is the following:
* In nominal conditions (that is, if no error occurs),
* the effect of a call to a key creation function in the PSA Cryptography
* API with a lifetime that places the key in a secure element is the
* following:
* -# The core calls psa_drv_se_key_management_t::p_allocate
* (or in some implementations
* psa_drv_se_key_management_t::p_validate_slot_number). The driver
* selects (or validates) a suitable slot number given the key attributes
* and the state of the secure element.
* -# The core calls psa_drv_se_key_management_t::p_import to import
* the key material in the selected slot.
* -# The core calls a key creation function in the driver.
*
* Other key creation methods lead to similar sequences. For example, the
* sequence for psa_generate_key() is the same except that the second step
* is a call to psa_drv_se_key_management_t::p_generate.
* The key creation functions in the PSA Cryptography API are:
* - psa_import_key(), which causes
* a call to `p_allocate` with \p method = #PSA_KEY_CREATION_IMPORT
* then a call to psa_drv_se_key_management_t::p_import.
* - psa_generate_key(), which causes
* a call to `p_allocate` with \p method = #PSA_KEY_CREATION_GENERATE
* then a call to psa_drv_se_key_management_t::p_import.
* - psa_key_derivation_output_key(), which causes
* a call to `p_allocate` with \p method = #PSA_KEY_CREATION_DERIVE
* then a call to psa_drv_se_key_derivation_t::p_derive.
* - psa_copy_key(), which causes
* a call to `p_allocate` with \p method = #PSA_KEY_CREATION_COPY
* then a call to psa_drv_se_key_management_t::p_export.
*
* In case of errors, other behaviors are possible.
* - If the PSA Cryptography subsystem dies after the first step,
@ -852,6 +872,7 @@ typedef struct {
* \param[in,out] persistent_data A pointer to the persistent data
* that allows writing.
* \param[in] attributes Attributes of the key.
* \param method The way in which the key is being created.
* \param[out] key_slot Slot where the key will be stored.
* This must be a valid slot for a key of the
* chosen type. It must be unoccupied.
@ -867,6 +888,7 @@ typedef psa_status_t (*psa_drv_se_allocate_key_t)(
psa_drv_se_context_t *drv_context,
void *persistent_data,
const psa_key_attributes_t *attributes,
psa_key_creation_method_t method,
psa_key_slot_number_t *key_slot);
/** \brief A function that determines whether a slot number is valid
@ -884,9 +906,10 @@ typedef psa_status_t (*psa_drv_se_allocate_key_t)(
* sake of initial device provisioning or onboarding. Such a mechanism may
* be added to a future version of the PSA Cryptography API specification.
*
* \param[in,out] drv_context The driver context structure.
* \param[in] attributes Attributes of the key.
* \param[in] key_slot Slot where the key is to be stored.
* \param[in,out] drv_context The driver context structure.
* \param[in] attributes Attributes of the key.
* \param method The way in which the key is being created.
* \param[in] key_slot Slot where the key is to be stored.
*
* \retval #PSA_SUCCESS
* The given slot number is valid for a key with the given
@ -903,6 +926,7 @@ typedef psa_status_t (*psa_drv_se_allocate_key_t)(
typedef psa_status_t (*psa_drv_se_validate_slot_number_t)(
psa_drv_se_context_t *drv_context,
const psa_key_attributes_t *attributes,
psa_key_creation_method_t method,
psa_key_slot_number_t key_slot);
/** \brief A function that imports a key into a secure element in binary format