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/*
* Copyright (c) 2010-2011,2014 Apple Inc. All Rights Reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this
* file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_LICENSE_HEADER_END@
*/
#ifndef _SEC_CUSTOM_TRANSFORM_H__
#define _SEC_CUSTOM_TRANSFORM_H__
#include <Security/SecTransform.h>
// Blocks are required for custom transforms
#ifdef __BLOCKS__
CF_EXTERN_C_BEGIN
CF_ASSUME_NONNULL_BEGIN
CF_IMPLICIT_BRIDGING_ENABLED
/*!
@header
Custom transforms are an API that provides the ability to easily create new
transforms. The essential functions of a transform are created in a
collection of blocks. These blocks override the standard behavior of the
base transform; a custom transform with no overrides is a null transform
that merely passes through a data flow.
A new transform type is created when calling the SecTransformRegister
function which registers the name of the new transform and sets up its
overrides. The SecTransformCreate function creates a new instance of a
registered custom transform.
A sample custom transform is provided here, along with a basic test program.
This transform creates a Caesar cipher transform, one that simply adds a
value to every byte of the plaintext.
-----cut here-----
<pre>
@textblock
//
// CaesarXform.c
//
// Copyright (c) 2010-2011,2014 Apple Inc. All Rights Reserved.
//
//
#include <Security/SecCustomTransform.h>
#include <Security/SecTransform.h>
// This is the unique name for the custom transform type.
const CFStringRef kCaesarCipher = CFSTR("com.apple.caesarcipher");
// Name of the "key" attribute.
const CFStringRef kKeyAttributeName = CFSTR("key");
// Shortcut to return a CFError.
CFErrorRef invalid_input_error(void)
{
return CFErrorCreate(kCFAllocatorDefault, kSecTransformErrorDomain,
kSecTransformErrorInvalidInput, NULL);
}
// =========================================================================
// Implementation of the Transform instance
// =========================================================================
static SecTransformInstanceBlock CaesarImplementation(CFStringRef name,
SecTransformRef newTransform,
SecTransformImplementationRef ref)
{
SecTransformInstanceBlock instanceBlock =
^{
CFErrorRef result = NULL;
// Every time a new instance of this custom transform class is
// created, this block is called. This behavior means that any
// block variables created in this block act like instance
// variables for the new custom transform instance.
__block int _key = 0;
result = SecTransformSetAttributeAction(ref,
kSecTransformActionAttributeNotification,
kKeyAttributeName,
^(SecTransformAttributeRef name, CFTypeRef d)
{
CFNumberGetValue((CFNumberRef)d, kCFNumberIntType, &_key);
return d;
});
if (result)
return result;
// Create an override that will be called to process the input
// data into the output data
result = SecTransformSetDataAction(ref,
kSecTransformActionProcessData,
^(CFTypeRef d)
{
if (NULL == d) // End of stream?
return (CFTypeRef) NULL; // Just return a null.
char *dataPtr = (char *)CFDataGetBytePtr((CFDataRef)d);
CFIndex dataLength = CFDataGetLength((CFDataRef)d);
// Do the processing in memory. There are better ways to do
// this but for showing how custom transforms work this is fine.
char *buffer = (char *)malloc(dataLength);
if (NULL == buffer)
return (CFTypeRef) invalid_input_error(); // Return a CFErrorRef
// Do the work of the caesar cipher (Rot(n))
CFIndex i;
for (i = 0; i < dataLength; i++)
buffer[i] = dataPtr[i] + _key;
return (CFTypeRef)CFDataCreateWithBytesNoCopy(NULL, (UInt8 *)buffer,
dataLength, kCFAllocatorMalloc);
});
return result;
};
return Block_copy(instanceBlock);
}
SecTransformRef CaesarTransformCreate(CFIndex k, CFErrorRef* error)
{
SecTransformRef caesarCipher;
__block Boolean result = 1;
static dispatch_once_t registeredOK = 0;
dispatch_once(&registeredOK,
^{
result = SecTransformRegister(kCaesarCipher, &CaesarImplementation, error);
});
if (!result)
return NULL;
caesarCipher = SecTransformCreate(kCaesarCipher, error);
if (NULL != caesarCipher)
{
CFNumberRef keyNumber = CFNumberCreate(kCFAllocatorDefault,
kCFNumberIntType, &k);
SecTransformSetAttribute(caesarCipher, kKeyAttributeName,
keyNumber, error);
CFRelease(keyNumber);
}
return caesarCipher;
}
// The second function shows how to use custom transform defined in the
// previous function
// =========================================================================
// Use a custom ROT-N (caesar cipher) transform
// =========================================================================
CFDataRef TestCaesar(CFDataRef theData, int rotNumber)
{
CFDataRef result = NULL;
CFErrorRef error = NULL;
if (NULL == theData)
return result;
// Create an instance of the custom transform
SecTransformRef caesarCipher = CaesarTransformCreate(rotNumber, &error);
if (NULL == caesarCipher || NULL != error)
return result;
// Set the data to be transformed as the input to the custom transform
SecTransformSetAttribute(caesarCipher,
kSecTransformInputAttributeName, theData, &error);
if (NULL != error)
{
CFRelease(caesarCipher);
return result;
}
// Execute the transform synchronously
result = (CFDataRef)SecTransformExecute(caesarCipher, &error);
CFRelease(caesarCipher);
return result;
}
#include <CoreFoundation/CoreFoundation.h>
int main (int argc, const char *argv[])
{
CFDataRef testData, testResult;
UInt8 bytes[26];
int i;
// Create some test data, a string from A-Z
for (i = 0; i < sizeof(bytes); i++)
bytes[i] = 'A' + i;
testData = CFDataCreate(kCFAllocatorDefault, bytes, sizeof(bytes));
CFRetain(testData);
CFShow(testData);
// Encrypt the test data
testResult = TestCaesar(testData, 3);
CFShow(testResult);
CFRelease(testData);
CFRelease(testResult);
return 0;
}
@/textblock
</pre>
*/
/**************** Custom Transform attribute metadata ****************/
/*!
@enum Custom Transform Attribute Metadata
@discussion
Within a transform, each of its attributes is a collection of
"metadata attributes", of which name and current value are two. The
value is directly visible from outside; the other metadata
attributes direct the behavior of the transform and
its function within its group. Each attribute may be tailored by setting its metadata.
@const kSecTransformMetaAttributeValue
The actual value of the attribute. The attribute value has a default
value of NULL.
@const kSecTransformMetaAttributeName
The name of the attribute. Attribute name is read only and may
not be used with the SecTransformSetAttributeBlock block.
@const kSecTransformMetaAttributeRef
A direct reference to an attribute's value. This reference allows
for direct access to an attribute without having to look up the
attribute by name. If a transform commonly uses an attribute, using
a reference speeds up the use of that attribute. Attribute
references are not visible or valid from outside of the particular
transform instance.
@const kSecTransformMetaAttributeRequired
Specifies if an attribute must have a non NULL value set or have an
incoming connection before the transform starts to execute. This
metadata has a default value of true for the input attribute, but
false for all other attributes.
@const kSecTransformMetaAttributeRequiresOutboundConnection
Specifies if an attribute must have an outbound connection. This
metadata has a default value of true for the output attribute but is
false for all other attributes.
@const kSecTransformMetaAttributeDeferred
Determines if the AttributeSetNotification notification or the
ProcessData blocks are deferred until SecExecuteTransform is called.
This metadata value has a default value of true for the input
attribute but is false for all other attributes.
@const kSecTransformMetaAttributeStream
Specifies if the attribute should expect a series of values ending
with a NULL to specify the end of the data stream. This metadata has
a default value of true for the input and output attributes, but is
false for all other attributes.
@const kSecTransformMetaAttributeCanCycle
A Transform group is a directed graph which is typically acyclic.
Some transforms need to work with cycles. For example, a transform
that emits a header and trailer around the data of another transform
must create a cycle. If this metadata set to true, no error is
returned if a cycle is detected for this attribute.
@const kSecTransformMetaAttributeExternalize
Specifies if this attribute should be written out when creating the
external representation of this transform. This metadata has a
default value of true.
@const kSecTransformMetaAttributeHasOutboundConnections
This metadata value is true if the attribute has an outbound
connection. This metadata is read only.
@const kSecTransformMetaAttributeHasInboundConnection
This metadata value is true if the attribute has an inbound
connection. This metadata is read only.
*/
typedef CF_ENUM(CFIndex, SecTransformMetaAttributeType)
{
kSecTransformMetaAttributeValue,
kSecTransformMetaAttributeName,
kSecTransformMetaAttributeRef,
kSecTransformMetaAttributeRequired,
kSecTransformMetaAttributeRequiresOutboundConnection,
kSecTransformMetaAttributeDeferred,
kSecTransformMetaAttributeStream,
kSecTransformMetaAttributeCanCycle,
kSecTransformMetaAttributeExternalize,
kSecTransformMetaAttributeHasOutboundConnections,
kSecTransformMetaAttributeHasInboundConnection
};
/*!
@typedef SecTransformAttributeRef
@abstract A direct reference to an attribute. Using an attribute
reference speeds up using an attribute's value by removing
the need to look
it up by name.
*/
typedef CFTypeRef SecTransformAttributeRef;
/*!
@typedef SecTransformStringOrAttributeRef
@abstract This type signifies that either a CFStringRef or
a SecTransformAttributeRef may be used.
*/
typedef CFTypeRef SecTransformStringOrAttributeRef;
/*!
@typedef SecTransformActionBlock
@abstract A block that overrides the default behavior of a
custom transform.
@result If this block is used to overide the
kSecTransformActionExternalizeExtraData action then the
block should return a CFDictinaryRef of the custom
items to be exported. For all of other actions the
block should return NULL. If an error occurs for
any action, the block should return a CFErrorRef.
@discussion A SecTransformTransformActionBlock block is used to
override
the default behavior of a custom transform. This block is
associated with the SecTransformOverrideTransformAction
block.
The behaviors that can be overridden are:
kSecTransformActionCanExecute
Determine if the transform has all of the data
needed to run.
kSecTransformActionStartingExecution
Called just before running ProcessData.
kSecTransformActionFinalize
Called just before deleting the custom transform.
kSecTransformActionExternalizeExtraData
Called to allow for writing out custom data
to be exported.
Example:
<pre>
@textblock
SecTransformImplementationRef ref;
CFErrorRef error = NULL;
error = SecTransformSetTransformAction(ref, kSecTransformActionStartingExecution,
^{
// This is where the work to initialize any data needed
// before running
CFErrorRef result = DoMyInitialization();
return result;
});
SecTransformTransformActionBlock actionBlock =
^{
// This is where the work to clean up any existing data
// before running
CFErrorRef result = DoMyFinalization();
return result;
};
error = SecTransformSetTransformAction(ref, kSecTransformActionFinalize,
actionBlock);
@/textblock
</pre>
*/
typedef CFTypeRef __nullable (^SecTransformActionBlock)(void);
/*!
@typedef SecTransformAttributeActionBlock
@abstract A block used to override the default attribute handling
for when an attribute is set.
@param attribute The attribute whose default is being overridden or NULL
if this is a generic notification override
@param value Proposed new value for the attribute.
@result The new value of the attribute if successful. If an
error occurred then a CFErrorRef is returned. If a transform
needs to have a CFErrorRef as the value of an attribute,
then the CFErrorRef needs to be placed into a container such
as a CFArrayRef, CFDictionaryRef etc.
@discussion See the example program in this header for more details.
*/
typedef CFTypeRef __nullable (^SecTransformAttributeActionBlock)(
SecTransformAttributeRef attribute,
CFTypeRef value);
/*!
@typedef SecTransformDataBlock
@abstract A block used to override the default data handling
for a transform.
@param data The data to be processed. When this block is used
to to implement the kSecTransformActionProcessData action,
the data is the input data that is to be processed into the
output data. When this block is used to implement the
kSecTransformActionInternalizeExtraData action, the data is
a CFDictionaryRef that contains the data that needs to be
imported.
@result When this block is used to implment the
kSecTransformActionProcessData action, the value returned
is to be the data that will be passed to the output
attribute. If an error occured while processing the input
data then the block should return a CFErrorRef.
When this block is used to implement the
kSecTransformActionInternalizeExtraData action then this block
should return NULL or a CFErrorRef if an error occurred.
@discussion See the example program for more details.
*/
typedef CFTypeRef __nullable (^SecTransformDataBlock)(CFTypeRef data);
/*!
@typedef SecTransformInstanceBlock
@abstract This is the block that is returned from an
implementation of a CreateTransform function.
@result A CFErrorRef if an error occurred or NULL.
@discussion The instance block that is returned from the
developers CreateTransform function, defines
the behavior of a custom attribute. Please
see the example at the head of this file.
*/
typedef CFErrorRef __nullable (^SecTransformInstanceBlock)(void);
/*!
@typedef SecTransformImplementationRef
@abstract The SecTransformImplementationRef is a pointer to a block
that implements an instance of a transform.
*/
typedef const struct OpaqueSecTransformImplementation* SecTransformImplementationRef;
/*!
@function SecTransformSetAttributeAction
@abstract Be notified when a attribute is set. The supplied block is
called when the attribute is set. This can be done for a
specific named attribute or all attributes.
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param action The behavior to be set. This can be one of the following
actions:
kSecTransformActionAttributeNotification - add a block that
is called when an attribute is set. If the name is NULL,
then the supplied block is called for all set attributes
except for ones that have a specific block as a handler.
For example, if there is a handler for the attribute "foo"
and for all attributes, the "foo" handler is called when the
"foo" attribute is set, but all other attribute sets will
call the NULL handler.
The kSecTransformActionProcessData action is a special case
of a SecTransformSetAttributeAction action. If this is
called on the input attribute then it will overwrite any
kSecTransformActionProcessData that was set.
kSecTransformActionAttributeValidation Add a block that is
called to validate the input to an attribute.
@param attribute
The name of the attribute that will be handled. An attribute
reference may also be given here. A NULL name indicates that
the supplied action is for all attributes.
@param newAction
A SecTransformAttributeActionBlock which implements the
behavior.
@result A CFErrorRef if an error occured NULL otherwise.
@discussion This function may be called multiple times for either a
named attribute or for all attributes when the attribute
parameter is NULL. Each time the API is called it overwrites
what was there previously.
*/
CF_EXPORT __nullable
CFErrorRef SecTransformSetAttributeAction(SecTransformImplementationRef ref,
CFStringRef action,
SecTransformStringOrAttributeRef __nullable attribute,
SecTransformAttributeActionBlock newAction);
/*!
@function SecTransformSetDataAction
@abstract Change the way a custom transform will do data processing.
When the action parameter is kSecTransformActionProcessData
The newAction block will change the way that input data is
processed to become the output data. When the action
parameter is kSecTransformActionInternalizeExtraData it will
change the way a custom transform reads in data to be
imported into the transform.
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param action The action being overridden. This value should be one of the
following:
kSecTransformActionProcessData
Change the way that input data is processed into the
output data. The default behavior is to simply copy
the input data to the output attribute.
The kSecTransformActionProcessData action is really
a special case of a SecTransformSetAttributeAction
action. If you call this method with
kSecTransformActionProcessData it would overwrite
any kSecTransformActionAttributeNotification action
that was set proviously
kSecTransformActionInternalizeExtraData
Change the way that custom externalized data is
imported into the transform. The default behavior
is to do nothing.
@param newAction
A SecTransformDataBlock which implements the behavior.
If the action parameter is kSecTransformActionProcessData then
this block will be called to process the input data into the
output data.
if the action parameter is kSecTransformActionInternalizeExtraData then
this block will called to input custom data into the transform.
@result A CFErrorRef is an error occured NULL otherwise.
@discussion This API may be called multiple times. Each time the API is called
it overwrites what was there previously.
*/
CF_EXPORT __nullable
CFErrorRef SecTransformSetDataAction(SecTransformImplementationRef ref,
CFStringRef action,
SecTransformDataBlock newAction);
/*
@function SecTransformSetTransformAction
@abstract Change the way that transform deals with transform lifecycle
behaviors.
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform. It provides the neccessary context
for making the call to modify a custom transform.
@param action Defines what behavior will be changed. The possible values
are:
kSecTransformActionCanExecute
A CanExecute block is called before the transform
starts to execute. Returning NULL indicates that the
transform has all necessary parameters set up to be
able to execute. If there is a condition that
prevents this transform from executing, return a
CFError. The default behavior is to return NULL.
kSecTransformActionStartingExecution
A StartingExecution block is called as a transform
starts execution but before any input is delivered.
Transform-specific initialization can be performed
in this block.
kSecTransformActionFinalize
A Finalize block is called before a transform is
released. Any final cleanup can be performed in this
block.
kSecTransformActionExternalizeExtraData
An ExternalizeExtraData block is called before a
transform is externalized. If there is any extra
work that the transform needs to do (e.g. copy data
from local variables to attributes) it can be
performed in this block.
@param newAction
A SecTransformTransformActionBlock which implements the behavior.
@result A CFErrorRef if an error occured NULL otherwise.
*/
CF_EXPORT __nullable
CFErrorRef SecTransformSetTransformAction(SecTransformImplementationRef ref,
CFStringRef action,
SecTransformActionBlock newAction);
/*!
@function SecTranformCustomGetAttribute
@abstract Allow a custom transform to get an attribute value
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param attribute
The name or the attribute handle of the attribute whose
value is to be retrieved.
@param type The type of data to be retrieved for the attribute. See the
discussion on SecTransformMetaAttributeType for details.
@result The value of the attribute.
*/
CF_EXPORT __nullable
CFTypeRef SecTranformCustomGetAttribute(SecTransformImplementationRef ref,
SecTransformStringOrAttributeRef attribute,
SecTransformMetaAttributeType type) AVAILABLE_MAC_OS_X_VERSION_10_7_AND_LATER_BUT_DEPRECATED_IN_MAC_OS_X_VERSION_10_8;
/*!
@function SecTransformCustomGetAttribute
@abstract Allow a custom transform to get an attribute value
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param attribute
The name or the attribute handle of the attribute whose
value is to be retrieved.
@param type The type of data to be retrieved for the attribute. See the
discussion on SecTransformMetaAttributeType for details.
@result The value of the attribute.
*/
CF_EXPORT __nullable
CFTypeRef SecTransformCustomGetAttribute(SecTransformImplementationRef ref,
SecTransformStringOrAttributeRef attribute,
SecTransformMetaAttributeType type) __asm__("_SecTranformCustomGetAttribute");
/*!
@function SecTransformCustomSetAttribute
@abstract Allow a custom transform to set an attribute value
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param attribute
The name or the attribute handle of the attribute whose
value is to be set.
@param type The type of data to be retrieved for the attribute. See the
discussion on SecTransformMetaAttributeType for details.
@param value The new value for the attribute
@result A CFErrorRef if an error occured , NULL otherwise.
@discussion Unlike the SecTransformSetAttribute API this API can set
attribute values while a transform is executing. These
values are limited to the custom transform instance that
is bound to the ref parameter.
*/
CF_EXPORT __nullable
CFTypeRef SecTransformCustomSetAttribute(SecTransformImplementationRef ref,
SecTransformStringOrAttributeRef attribute,
SecTransformMetaAttributeType type,
CFTypeRef __nullable value);
/*!
@function SecTransformPushbackAttribute
@abstract Allows for putting a single value back for a specific
attribute. This will stop the flow of data into the
specified attribute until any attribute is changed for the
transform instance bound to the ref parameter.
@param ref A SecTransformImplementationRef that is bound to an instance
of a custom transform.
@param attribute
The name or the attribute handle of the attribute whose
value is to be pushed back.
@param value The value being pushed back.
@result A CFErrorRef if an error occured , NULL otherwise.
*/
CF_EXPORT __nullable
CFTypeRef SecTransformPushbackAttribute(SecTransformImplementationRef ref,
SecTransformStringOrAttributeRef attribute,
CFTypeRef value);
/*!
@typedef SecTransformCreateFP
@abstract A function pointer to a function that will create a
new instance of a custom transform.
@param name The name of the new custom transform. This name MUST be
unique.
@param newTransform
The newly created transform Ref.
@param ref A reference that is bound to an instance of a custom
transform.
@result A SecTransformInstanceBlock that is used to create a new
instance of a custom transform.
@discussion The CreateTransform function creates a new transform. The
SecTransformInstanceBlock that is returned from this
function provides the implementation of all of the overrides
necessary to create the custom transform. This returned
SecTransformInstanceBlock is also where the "instance"
variables for the custom transform may be defined. See the
example in the header section of this file for more detail.
*/
typedef SecTransformInstanceBlock __nonnull (*SecTransformCreateFP)(CFStringRef name,
SecTransformRef newTransform,
SecTransformImplementationRef ref);
/************** custom Transform transform override actions **************/
/*!
@constant kSecTransformActionCanExecute
Overrides the standard behavior that checks to see if all of the
required attributes either have been set or are connected to
another transform. When overriding the default behavior the
developer can decided what the necessary data is to have for a
transform to be considered 'ready to run'. Returning NULL means
that the transform is ready to be run. If the transform is NOT
ready to run then the override should return a CFErrorRef
stipulating the error.
*/
CF_EXPORT const CFStringRef kSecTransformActionCanExecute;
/*!
@constant kSecTransformActionStartingExecution
Overrides the standard behavior that occurs just before starting
execution of a custom transform. This is typically overridden
to allow for initialization. This is used with the
SecTransformOverrideTransformAction block.
*/
CF_EXPORT const CFStringRef kSecTransformActionStartingExecution;
/*!
@constant kSecTransformActionFinalize
Overrides the standard behavior that occurs just before deleting
a custom transform. This is typically overridden to allow for
memory clean up of a custom transform. This is used with the
SecTransformOverrideTransformAction block.
*/
CF_EXPORT const CFStringRef kSecTransformActionFinalize;
/*!
@constant kSecTransformActionExternalizeExtraData
Allows for adding to the data that is stored using an override
to the kSecTransformActionExternalizeExtraData block. The output
of this override is a dictionary that contains the custom
externalized data. A common use of this override is to write out
a version number of a custom transform.
*/
CF_EXPORT const CFStringRef kSecTransformActionExternalizeExtraData;
/*!
@constant kSecTransformActionProcessData
Overrides the standard data processing for an attribute. This is
almost exclusively used for processing the input attribute as
the return value of their block sets the output attribute. This
is used with the SecTransformOverrideAttributeAction block.
*/
CF_EXPORT const CFStringRef kSecTransformActionProcessData;
/*!
@constant kSecTransformActionInternalizeExtraData
Overrides the standard processing that occurs when externalized
data is used to create a transform. This is closely tied to the
kSecTransformActionExternalizeExtraData override. The 'normal'
attributes are read into the new transform and then this is
called to read in the items that were written out using
kSecTransformActionExternalizeExtraData override. A common use
of this override would be to read in the version number of the
externalized custom transform.
*/
CF_EXPORT const CFStringRef kSecTransformActionInternalizeExtraData;
/*!
@constant SecTransformActionAttributeNotification
Allows a block to be called when an attribute is set. This
allows for caching the value as a block variable in the instance
block or transmogrifying the data to be set. This action is
where a custom transform would be able to do processing outside
of processing input to output as process data does. One the
data has been processed the action block can call
SecTransformCustomSetAttribute to update and other attribute.
*/
CF_EXPORT const CFStringRef kSecTransformActionAttributeNotification;
/*!
@constant kSecTransformActionAttributeValidation
Allows a block to be called to validate the new value for an
attribute. The default is no validation and any CFTypeRef can
be used as the new value. The block should return NULL if the
value is ok to set on the attribute or a CFErrorRef otherwise.
*/
CF_EXPORT const CFStringRef kSecTransformActionAttributeValidation;
/*!
@function SecTransformRegister
@abstract Register a new custom transform so that it may be used to
process data
@param uniqueName
A unique name for this custom transform. It is recommended
that a reverse DNS name be used for the name of your custom
transform
@param createTransformFunction
A SecTransformCreateFP function pointer. The function must
return a SecTransformInstanceBlock block that block_copy has
been called on before returning the block. Failure to call
block_copy will cause undefined behavior.
@param error This pointer is set if an error occurred. This value
may be NULL if you do not want an error returned.
@result True if the custom transform was registered false otherwise
*/
CF_EXPORT
Boolean SecTransformRegister(CFStringRef uniqueName,
SecTransformCreateFP createTransformFunction,
CFErrorRef* error)
__OSX_AVAILABLE_STARTING(__MAC_10_7,__IPHONE_NA);
/*!
@function SecTransformCreate
@abstract Creates a transform computation object.
@param name The type of transform to create, must have been registered
by SecTransformRegister, or be a system pre-defined
transform type.
@param error A pointer to a CFErrorRef. This pointer is set if an error
occurred. This value may be NULL if you do not want an
error returned.
@result A pointer to a SecTransformRef object. This object must be
released with CFRelease when you are done with it. This
function returns NULL if an error occurred.
*/
CF_EXPORT __nullable
SecTransformRef SecTransformCreate(CFStringRef name, CFErrorRef *error)
__OSX_AVAILABLE_STARTING(__MAC_10_7,__IPHONE_NA);
/*!
@Function SecTransformNoData
@abstract Returns back A CFTypeRef from inside a processData
override that says that while no data is being returned
the transform is still active and awaiting data.
@result A 'special' value that allows that specifies that the
transform is still active and awaiting data.
@discussion The standard behavior for the ProcessData override is that
it will receive a CFDataRef and it processes that data and
returns a CFDataRef that contains the processed data. When
there is no more data to process the ProcessData override
block is called one last time with a NULL CFDataRef. The
ProcessData block should/must return the NULL CFDataRef to
complete the processing. This model does not work well for
some transforms. For example a digest transform needs to see
ALL of the data that is being digested before it can send
out the digest value.
If a ProcessData block has no data to return, it can return
SecTransformNoData(), which informs the transform system
that there is no data to pass on to the next transform.
*/
CF_EXPORT
CFTypeRef SecTransformNoData(void);
CF_IMPLICIT_BRIDGING_DISABLED
CF_ASSUME_NONNULL_END
CF_EXTERN_C_END
#endif // __BLOCKS__
#endif // _SEC_CUSTOM_TRANSFORM_H__