## Modules

Modules — Module loading and initializing

## Functions

CK_FUNCTION_LIST ** | p11_kit_modules_load_and_initialize ()
void | p11_kit_modules_finalize_and_release ()
CK_FUNCTION_LIST ** | p11_kit_modules_load ()
CK_RV | p11_kit_modules_initialize ()
CK_RV | p11_kit_modules_finalize ()
void | p11_kit_modules_release ()
CK_FUNCTION_LIST * | p11_kit_module_load ()
CK_RV | p11_kit_module_initialize ()
CK_RV | p11_kit_module_finalize ()
void | p11_kit_module_release ()
CK_FUNCTION_LIST * | p11_kit_module_for_name ()
char * | p11_kit_module_get_name ()
int | p11_kit_module_get_flags ()
char * | p11_kit_config_option ()

## Types and Values

#define | P11_KIT_MODULE_CRITICAL
#define | P11_KIT_MODULE_UNMANAGED

## Description

PKCS#11 modules are used by crypto libraries and applications to access crypto objects (like keys and certificates) and to perform crypto operations.

In order for applications to behave consistently with regard to the user's installed PKCS#11 modules, each module must be configured so that applications or libraries know that they should load it.

When multiple consumers of a module (such as libraries or applications) are in the same process, coordination of the initialization and finalization of PKCS#11 modules is required. To do this modules are managed by p11-kit. This means that various unsafe methods are coordinated between callers. Unmanaged modules are simply the raw PKCS#11 module pointers without p11-kit getting in the way. It is highly recommended that the default managed behavior is used.

The functions here provide support for initializing configured modules. The `p11_kit_modules_load()` function should be used to load and initialize the configured modules. When done, the `p11_kit_modules_release()` function should be used to release those modules and associated resources.

In addition `p11_kit_config_option()` can be used to access other parts of the module configuration.

If a consumer wishes to load an arbitrary PKCS#11 module that's not configured use `p11_kit_module_load()` to do so. And use `p11_kit_module_release()` to later release it.

Modules are represented by a pointer to their `CK_FUNCTION_LIST` entry points.

## Functions

### p11_kit_modules_load_and_initialize ()

    CK_FUNCTION_LIST **
    p11_kit_modules_load_and_initialize (int flags);

Load and initialize configured modules.

If a critical module fails to load or initialize then the function will return `NULL`. Non-critical modules will be skipped and not included in the returned module list.

Use `p11_kit_modules_finalize_and_release()` when you're done with the modules returned by this function.

#### Parameters

flags | flags to use to load the modules |

#### Returns

a `NULL` terminated list of modules, or `NULL` on failure

### p11_kit_modules_finalize_and_release ()

    void
    p11_kit_modules_finalize_and_release (CK_FUNCTION_LIST **modules);

Finalize and then release the a set of loaded PKCS#11 modules.

The modules may be either managed or unmanaged. The array containing the module pointers is also freed by this function.

Modules are released even if their finalization returns an error code. Managed modules will not be actually finalized or released until all callers using them have done so.

For managed modules the `C_Finalize` function is overridden so that multiple callers can finalize the same modules. In addition for managed modules multiple callers can finalize from different threads, and still guarantee consistent thread-safe behavior.

For unmanaged modules if multiple callers try to finalize a module, then one of the calls will return `CKR_CRYPTOKI_NOT_INITIALIZED` according to the PKCS#11 specification. In addition there are no guarantees that thread-safe behavior will occur if multiple callers initialize from different threads.

#### Parameters

modules | the modules to release |

### p11_kit_modules_load ()

    CK_FUNCTION_LIST **
    p11_kit_modules_load (const char *reserved,
                          int flags);

Load the configured PKCS#11 modules.

If `flags` contains the `P11_KIT_MODULE_UNMANAGED` flag, then the modules will be not be loaded in 'managed' mode regardless of its configuration. This is not recommended for general usage.

If `flags` contains the `P11_KIT_MODULE_CRITICAL` flag then the modules will all be treated as 'critical', regardless of the module configuration. This means that a failure to load any module will cause this funtion to fail.

For unmanaged modules there is no guarantee to the state of the modules. Other callers may be using the modules. Using unmanaged modules haphazardly is not recommended for this reason. Some modules (such as those configured with RPC) cannot be loaded in unmanaged mode, and will be skipped.

Use `p11_kit_modules_release()` to release the modules returned by this function.

If this function fails, then an error message will be available via the `p11_kit_message()` function.

#### Parameters

reserved | set to `NULL` |
flags | flags to use to load the module |

#### Returns

a null terminated list of modules represented as PKCS#11 function lists, or `NULL` on failure

### p11_kit_modules_initialize ()

    CK_RV
    p11_kit_modules_initialize (CK_FUNCTION_LIST **modules,
                                p11_kit_destroyer failure_callback);

Initialize all the modules in the `modules` list by calling their `C_Initialize` function.

For managed modules the `C_Initialize` function is overridden so that multiple callers can initialize the same modules. In addition for managed modules multiple callers can initialize from different threads, and still guarantee consistent thread-safe behavior.

For unmanaged modules if multiple callers try to initialize a module, then one of the calls will return `CKR_CRYPTOKI_ALREADY_INITIALIZED` according to the PKCS#11 specification. In addition there are no guarantees that thread-safe behavior will occur if multiple callers initialize from different threads.

When a module fails to initialize it is removed from the `modules` list. If the `failure_callback` is not `NULL` then it is called with the modules that fail to initialize. For example, you may pass `p11_kit_module_release()` as a `failure_callback` if the `modules` list was loaded wit `p11_kit_modules_load()`.

The return value will return the failure code of the last critical module that failed to initialize. Non-critical module failures do not affect the return value. If no critical modules failed to initialize then the return value will be `CKR_OK`.

When modules are removed, the list will be `NULL` terminated at the appropriate place so it can continue to be used as a modules list.

This function does not accept a `CK_C_INITIALIZE_ARGS` argument. Custom initialization arguments cannot be supported when multiple consumers load the same module.

#### Parameters

modules | a `NULL` terminated list of modules |
failure_callback | called with modules that fail to initialize |

#### Returns

`CKR_OK` or the failure code of the last critical module that failed to initialize.

### p11_kit_modules_finalize ()

    CK_RV
    p11_kit_modules_finalize (CK_FUNCTION_LIST **modules);

Finalize each module in the `modules` list by calling its `C_Finalize` function. Regardless of failures, all `modules` will have their `C_Finalize` function called.

If a module returns a failure from its `C_Finalize` method it will be returned. If multiple modules fail, the last failure will be returned.

For managed modules the `C_Finalize` function is overridden so that multiple callers can finalize the same modules. In addition for managed modules multiple callers can finalize from different threads, and still guarantee consistent thread-safe behavior.

For unmanaged modules if multiple callers try to finalize a module, then one of the calls will return `CKR_CRYPTOKI_NOT_INITIALIZED` according to the PKCS#11 specification. In addition there are no guarantees that thread-safe behavior will occur if multiple callers finalize from different threads.

#### Parameters

modules | a `NULL` terminated list of modules |

#### Returns

`CKR_OK` or the failure code of the last module that failed to finalize

### p11_kit_modules_release ()

    void
    p11_kit_modules_release (CK_FUNCTION_LIST **modules);

Release the a set of loaded PKCS#11 modules.

The modules may be either managed or unmanaged. The array containing the module pointers is also freed by this function.

Managed modules will not be actually released until all callers using them have done so. If the modules were initialized, they should have been finalized first.

#### Parameters

modules | the modules to release |

### p11_kit_module_load ()

    CK_FUNCTION_LIST *
    p11_kit_module_load (const char *module_path,
                         int flags);

Load an arbitrary PKCS#11 module from a dynamic library file, and initialize it. Normally using the `p11_kit_modules_load()` function is preferred.

Using this function to load modules allows coordination between multiple callers of the same module in a single process. If `flags` contains the `P11_KIT_MODULE_UNMANAGED` flag, then the modules will be not be loaded in 'managed' mode and not be coordinated. This is not recommended for general usage.

Subsequent calls to this function for the same module will result in an initialization count being incremented for the module. It is safe (although usually unnecessary) to use this function on registered modules.

The module should be released with `p11_kit_module_release()`.

If this function fails, then an error message will be available via the `p11_kit_message()` function.

#### Parameters

module_path | full file path of module library |
flags | flags to use when loading the module |

#### Returns

the loaded module PKCS#11 functions or `NULL` on failure

### p11_kit_module_initialize ()

    CK_RV
    p11_kit_module_initialize (CK_FUNCTION_LIST *module);

Initialize a PKCS#11 module by calling its `C_Initialize` function.

For managed modules the `C_Initialize` function is overridden so that multiple callers can initialize the same modules. In addition for managed modules multiple callers can initialize from different threads, and still guarantee consistent thread-safe behavior.

For unmanaged modules if multiple callers try to initialize a module, then one of the calls will return `CKR_CRYPTOKI_ALREADY_INITIALIZED` according to the PKCS#11 specification. In addition there are no guarantees that thread-safe behavior will occur if multiple callers initialize from different threads.

This function does not accept a `CK_C_INITIALIZE_ARGS` argument. Custom initialization arguments cannot be supported when multiple consumers load the same module.

#### Parameters

module | the module to initialize |

#### Returns

`CKR_OK` or a failure code

### p11_kit_module_finalize ()

    CK_RV
    p11_kit_module_finalize (CK_FUNCTION_LIST *module);

Finalize a PKCS#11 module by calling its `C_Finalize` function.

For managed modules the `C_Finalize` function is overridden so that multiple callers can finalize the same modules. In addition for managed modules multiple callers can finalize from different threads, and still guarantee consistent thread-safe behavior.

For unmanaged modules if multiple callers try to finalize a module, then one of the calls will return `CKR_CRYPTOKI_NOT_INITIALIZED` according to the PKCS#11 specification. In addition there are no guarantees that thread-safe behavior will occur if multiple callers finalize from different threads.

#### Parameters

module | the module to finalize |

#### Returns

`CKR_OK` or a failure code

### p11_kit_module_release ()

    void
    p11_kit_module_release (CK_FUNCTION_LIST *module);

Release the a loaded PKCS#11 modules.

The module may be either managed or unmanaged. The `C_Finalize` function will be called if no other callers are using this module.

#### Parameters

module | the module to release |

### p11_kit_module_for_name ()

    CK_FUNCTION_LIST *
    p11_kit_module_for_name (CK_FUNCTION_LIST **modules,
                             const char *name);

Look through the list of `modules` and return the module whose `name` matches.

Only configured modules have names. Configured modules are loaded by `p11_kit_modules_load()`. The module passed to this function can be either managed or unmanaged.

The return value is not copied or duplicated in anyway. It is still 'owned' by the `modules` list.

#### Parameters

modules | a list of modules to look through |
name | the name of the module to find |

#### Returns

the module which matches the name, or `NULL` if no match.

### p11_kit_module_get_name ()

    char *
    p11_kit_module_get_name (CK_FUNCTION_LIST *module);

Get the configured name of the PKCS#11 module.

Configured modules are loaded by `p11_kit_modules_load()`. The module passed to this function can be either managed or unmanaged. Non configured modules will return `NULL`.

Use `free()` to release the return value when you're done with it.

#### Parameters

module | pointer to a loaded module |

#### Returns

a newly allocated string containing the module name, or

`NULL` if the module is not a configured module

### p11_kit_module_get_flags ()

    int
    p11_kit_module_get_flags (CK_FUNCTION_LIST *module);

Get the flags for this module.

The `P11_KIT_MODULE_UNMANAGED` flag will be set if the module is not managed by p11-kit. It is a raw PKCS#11 module function list.

The `P11_KIT_MODULE_CRITICAL` flag will be set if the module is configured to be critical, and not be skipped over if it fails to initialize or load. This flag is also set for modules that are not configured, but have been loaded in another fashion.

#### Parameters

module | the module |

#### Returns

the flags for the module

### p11_kit_config_option ()

    char *
    p11_kit_config_option (CK_FUNCTION_LIST *module,
                           const char *option);

Retrieve the value for a configured option.

If `module` is `NULL`, then the global option with the given name will be retrieved. Otherwise `module` should point to a configured loaded module. If no such `option` or configured `module` exists, then `NULL` will be returned.

Use `free()` to release the returned value.

#### Parameters

module | the module to retrieve the option for, or `NULL` for global options |
option | the option to retrieve |

#### Returns

the option value or `NULL`

## Types and Values

### P11_KIT_MODULE_CRITICAL

    #define P11_KIT_MODULE_CRITICAL 1

Flag to load a module in 'critical' mode. Failure to load a critical module will prevent all other modules from loading. A failure when loading a non-critical module skips that module.

### P11_KIT_MODULE_UNMANAGED

    #define P11_KIT_MODULE_UNMANAGED 1

Module is loaded in non 'managed' mode. This is not recommended, disables many features, and prevents coordination between multiple callers of the same module.