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CRYPTO(9)	       FreeBSD Kernel Developer's Manual	     CRYPTO(9)

     crypto -- API for cryptographic services in the kernel

     #include <opencrypto/cryptodev.h>

     crypto_get_driverid(device_t dev, size_t session_size, int	flags);

     crypto_register(uint32_t driverid,	int alg, uint16_t maxoplen,
	 uint32_t flags);

     crypto_kregister(uint32_t driverid, int kalg, uint32_t flags);

     crypto_unregister(uint32_t	driverid, int alg);

     crypto_unregister_all(uint32_t driverid);

     crypto_done(struct	cryptop	*crp);

     crypto_kdone(struct cryptkop *krp);

     crypto_find_driver(const char *match);

     crypto_newsession(crypto_session_t	*cses, struct cryptoini	*cri,
	 int crid);

     crypto_freesession(crypto_session_t cses);

     crypto_dispatch(struct cryptop *crp);

     crypto_kdispatch(struct cryptkop *krp);

     crypto_unblock(uint32_t driverid, int what);

     struct cryptop *
     crypto_getreq(int num);

     crypto_freereq(struct cryptop *crp);

     #define CRYPTO_SYMQ     0x1
     #define CRYPTO_ASYMQ    0x2

     #define EALG_MAX_BLOCK_LEN	     16

     struct cryptoini {
	     int		cri_alg;
	     int		cri_klen;
	     int		cri_mlen;
	     caddr_t		cri_key;
	     uint8_t		cri_iv[EALG_MAX_BLOCK_LEN];
	     struct cryptoini  *cri_next;

     struct cryptodesc {
	     int		crd_skip;
	     int		crd_len;
	     int		crd_inject;
	     int		crd_flags;
	     struct cryptoini	CRD_INI;
     #define crd_iv	     CRD_INI.cri_iv
     #define crd_key	     CRD_INI.cri_key
     #define crd_alg	     CRD_INI.cri_alg
     #define crd_klen	     CRD_INI.cri_klen
	     struct cryptodesc *crd_next;

     struct cryptop {
	     TAILQ_ENTRY(cryptop) crp_next;
	     crypto_session_t	crp_session;
	     int		crp_ilen;
	     int		crp_olen;
	     int		crp_etype;
	     int		crp_flags;
	     caddr_t		crp_buf;
	     caddr_t		crp_opaque;
	     struct cryptodesc *crp_desc;
	     int	      (*crp_callback) (struct cryptop *);
	     caddr_t		crp_mac;

     struct crparam {
	     caddr_t	     crp_p;
	     u_int	     crp_nbits;

     #define CRK_MAXPARAM    8

     struct cryptkop {
	     TAILQ_ENTRY(cryptkop) krp_next;
	     u_int		krp_op;		/* ie. CRK_MOD_EXP or other */
	     u_int		krp_status;	/* return status */
	     u_short		krp_iparams;	/* # of	input parameters */
	     u_short		krp_oparams;	/* # of	output parameters */
	     uint32_t		krp_hid;
	     struct crparam	krp_param[CRK_MAXPARAM];
	     int	       (*krp_callback)(struct cryptkop *);

     crypto is a framework for drivers of cryptographic	hardware to register
     with the kernel so	"consumers" (other kernel subsystems, and users
     through the /dev/crypto device) are able to make use of it.  Drivers reg-
     ister with	the framework the algorithms they support, and provide entry
     points (functions)	the framework may call to establish, use, and tear
     down sessions.  Sessions are used to cache	cryptographic information in a
     particular	driver (or associated hardware), so initialization is not
     needed with every request.	 Consumers of cryptographic services pass a
     set of descriptors	that instruct the framework (and the drivers regis-
     tered with	it) of the operations that should be applied on	the data (more
     than one cryptographic operation can be requested).

     Keying operations are supported as	well.  Unlike the symmetric operators
     described above, these sessionless	commands perform mathematical opera-
     tions using input and output parameters.

     Since the consumers may not be associated with a process, drivers may not
     sleep(9).	The same holds for the framework.  Thus, a callback mechanism
     is	used to	notify a consumer that a request has been completed (the call-
     back is specified by the consumer on a per-request	basis).	 The callback
     is	invoked	by the framework whether the request was successfully com-
     pleted or not.  An	error indication is provided in	the latter case.  A
     specific error code, EAGAIN, is used to indicate that a session handle
     has changed and that the request may be re-submitted immediately with the
     new session.  Errors are only returned to the invoking function if	not
     enough information	to call	the callback is	available (meaning, there was
     a fatal error in verifying	the arguments).	 For session initialization
     and teardown no callback mechanism	is used.

     The crypto_find_driver() returns the driver id of the device whose	name
     matches match.  match can either be the exact name	of a device including
     the unit or the driver name without a unit.  In the latter	case, the id
     of	the first device with the matching driver name is returned.  If	no
     matching device is	found, the value -1 is returned.

     The crypto_newsession() routine is	called by consumers of cryptographic
     services (such as the ipsec(4) stack) that	wish to	establish a new	ses-
     sion with the framework.  The cri argument	points to a cryptoini struc-
     ture containing all the necessary information for the driver to establish
     the session.  The crid argument is	either a specific driver id or a bit-
     mask of flags.  The flags are CRYPTOCAP_F_HARDWARE, to select hardware
     devices, or CRYPTOCAP_F_SOFTWARE, to select software devices.  If both
     are specified, hardware devices are preferred over	software devices.  On
     success, the opaque session handle	of the new session will	be stored in
     *cses.  The cryptoini structure pointed to	by cri contains	these fields:

     cri_alg   An algorithm identifier.	 Currently supported algorithms	are:


     cri_klen  For variable-size key algorithms, the length of the key in

     cri_mlen  If non-zero, truncate the calculated hash to this many bytes.

     cri_key   The key to be used.

     cri_iv    An explicit initialization vector if it does not	prefix the
	       data.  This field is ignored during initialization
	       (crypto_newsession).  If	no IV is explicitly passed (see	below
	       on details), a random IV	is used	by the device driver process-
	       ing the request.

     cri_next  Pointer to another cryptoini structure.	This is	used to	estab-
	       lish dual-algorithm sessions, such as combining a cipher	with a

     The cryptoini structure and its contents will not be modified or refer-
     enced by the framework or any cryptographic drivers.  The memory associ-
     ated with cri can be released once	crypto_newsession() returns.

     crypto_freesession() is called with the session handle returned by
     crypto_newsession() to free the session.

     crypto_dispatch() is called to process a request.	The various fields in
     the cryptop structure are:

     crp_session   The session handle.

     crp_ilen	   The total length in bytes of	the buffer to be processed.

     crp_olen	   On return, contains the total length	of the result.	For
		   symmetric crypto operations,	this will be the same as the
		   input length.  This will be used if the framework needs to
		   allocate a new buffer for the result	(or for	re-formatting
		   the input).

     crp_callback  Callback routine invoked when a request is completed	via
		   crypto_done().  The callback	routine	should inspect the
		   crp_etype to	determine if the request was successfully com-

     crp_etype	   The error type, if any errors were encountered, or zero if
		   the request was successfully	processed.  If the EAGAIN er-
		   ror code is returned, the session handle has	changed	(and
		   has been recorded in	the crp_session	field).	 The consumer
		   should record the new session handle	and use	it in all sub-
		   sequent requests.  In this case, the	request	may be re-sub-
		   mitted immediately.	This mechanism is used by the frame-
		   work	to perform session migration (move a session from one
		   driver to another, because of availability, performance, or
		   other considerations).

		   This	field is only valid in the context of the callback
		   routine specified by	crp_callback.  Errors are returned to
		   the invoker of crypto_process() only	when enough informa-
		   tion	is not present to call the callback routine (i.e., if
		   the pointer passed is NULL or if no callback	routine	was

     crp_flags	   A bitmask of	flags associated with this request.  Currently
		   defined flags are:

		   CRYPTO_F_IMBUF     The buffer is an mbuf chain pointed to
				      by crp_mbuf.

		   CRYPTO_F_IOV	      The buffer is a uio structure pointed to
				      by crp_uio.

		   CRYPTO_F_BATCH     Batch operation if possible.

		   CRYPTO_F_CBIMM     Do callback immediately instead of doing
				      it from a	dedicated kernel thread.

		   CRYPTO_F_DONE      Operation	completed.

		   CRYPTO_F_CBIFSYNC  Do callback immediately if operation is
				      synchronous (that	the driver specified
				      the CRYPTOCAP_F_SYNC flag).

		   CRYPTO_F_ASYNC     Try to do	the crypto operation in	a pool
				      of workers if the	operation is synchro-
				      nous (that is, if	the driver specified
				      the CRYPTOCAP_F_SYNC flag).  It aims to
				      speed up processing by dispatching
				      crypto operations	on different proces-

				      Dispatch callbacks in the	same order
				      they are posted.	Only relevant if the
				      CRYPTO_F_ASYNC flag is set and if	the
				      operation	is synchronous.

     crp_buf	   Data	buffer unless CRYPTO_F_IMBUF or	CRYPTO_F_IOV is	set in
		   crp_flags.  The length in bytes is set in crp_ilen.

     crp_mbuf	   Data	buffer mbuf chain when CRYPTO_F_IMBUF is set in

     crp_uio	   struct uio data buffer when CRYPTO_F_IOV is set in

     crp_opaque	   Cookie passed through the crypto framework untouched.  It
		   is intended for the invoking	application's use.

     crp_desc	   A linked list of descriptors.  Each descriptor provides in-
		   formation about what	type of	cryptographic operation	should
		   be done on the input	buffer.	 The various fields are:

		   crd_iv      When the	flag CRD_F_IV_EXPLICIT is set, this
			       field contains the IV.

		   crd_key     When the	CRD_F_KEY_EXPLICIT flag	is set,	the
			       crd_key points to a buffer with encryption or
			       authentication key.

		   crd_alg     An algorithm to use.  Must be the same as the
			       one given at newsession time.

		   crd_klen    The crd_key key length.

		   crd_skip    The offset in the input buffer where processing
			       should start.

		   crd_len     How many	bytes, after crd_skip, should be pro-

		   crd_inject  The crd_inject field specifies an offset	in
			       bytes from the beginning	of the buffer.	For
			       encryption algorithms, this may be where	the IV
			       will be inserted	when encrypting	or where the
			       IV may be found for decryption (subject to
			       crd_flags).  For	MAC algorithms,	this is	where
			       the result of the keyed hash will be inserted.

		   crd_flags   The following flags are defined:

				    For	encryption algorithms, this bit	is set
				    when encryption is required	(when not set,
				    decryption is performed).

				    For	encryption, if this bit	is not set the
				    IV used to encrypt the packet will be
				    written at the location pointed to by
				    crd_inject.	 The IV	length is assumed to
				    be equal to	the blocksize of the encryp-
				    tion algorithm.  For encryption, if	this
				    bit	is set,	nothing	is done.  For decryp-
				    tion, this flag has	no meaning.  Applica-
				    tions that do special "IV cooking",	such
				    as the half-IV mode	in ipsec(4), can use
				    this flag to indicate that the IV should
				    not	be written on the packet.  This	flag
				    is typically used in conjunction with the
				    CRD_F_IV_EXPLICIT flag.

				    This bit is	set when the IV	is explicitly
				    provided by	the consumer in	the crd_iv
				    field.  Otherwise, for encryption opera-
				    tions the IV is provided for by the	driver
				    used to perform the	operation, whereas for
				    decryption operations the offset of	the IV
				    is provided	by the crd_inject field.  This
				    flag is typically used when	the IV is cal-
				    culated "on	the fly" by the	consumer, and
				    does not precede the data.

				    For	encryption and authentication (MAC)
				    algorithms,	this bit is set	when the key
				    is explicitly provided by the consumer in
				    the	crd_key	field for the given operation.
				    Otherwise, the key is taken	at newsession
				    time from the cri_key field.  As calculat-
				    ing	the key	schedule may take a while, it
				    is recommended that	often used keys	are
				    given their	own session.

				    For	compression algorithms,	this bit is
				    set	when compression is required (when not
				    set, decompression is performed).

		   CRD_INI     This cryptoini structure	will not be modified
			       by the framework	or the device drivers.	Since
			       this information	accompanies every crypto-
			       graphic operation request, drivers may re-ini-
			       tialize state on-demand (typically an expensive
			       operation).  Furthermore, the cryptographic
			       framework may re-route requests as a result of
			       full queues or hardware failure,	as described

		   crd_next    Point to	the next descriptor.  Linked opera-
			       tions are useful	in protocols such as ipsec(4),
			       where multiple cryptographic transforms may be
			       applied on the same block of data.

     crypto_getreq() allocates a cryptop structure with	a linked list of num
     cryptodesc	structures.

     crypto_freereq() deallocates a structure cryptop and any cryptodesc
     structures	linked to it.  Note that it is the responsibility of the call-
     back routine to do	the necessary cleanups associated with the opaque
     field in the cryptop structure.

     crypto_kdispatch()	is called to perform a keying operation.  The various
     fields in the cryptkop structure are:

     krp_op	   Operation code, such	as CRK_MOD_EXP.

     krp_status	   Return code.	 This errno-style variable indicates whether
		   lower level reasons for operation failure.

     krp_iparams   Number of input parameters to the specified operation.
		   Note	that each operation has	a (typically hardwired)	number
		   of such parameters.

     krp_oparams   Number of output parameters from the	specified operation.
		   Note	that each operation has	a (typically hardwired)	number
		   of such parameters.

     krp_kvp	   An array of kernel memory blocks containing the parameters.

     krp_hid	   Identifier specifying which low-level driver	is being used.

     krp_callback  Callback called on completion of a keying operation.

     The crypto_get_driverid(),	crypto_get_driver_session(),
     crypto_register(),	crypto_kregister(), crypto_unregister(),
     crypto_unblock(), and crypto_done() routines are used by drivers that
     provide support for cryptographic primitives to register and unregister
     with the kernel crypto services framework.

     Drivers must first	use the	crypto_get_driverid() function to acquire a
     driver identifier,	specifying the flags as	an argument.  One of
     CRYPTOCAP_F_SYNC may also be specified, and should	be specified if	the
     driver does all of	it's operations	synchronously.	Drivers	must pass the
     size of their session structure as	the second argument.  An appropriately
     sized memory will be allocated by the framework, zeroed, and passed to
     the driver's newsession() method.

     For each algorithm	the driver supports, it	must then call
     crypto_register().	 The first two arguments are the driver	and algorithm
     identifiers.  The next two	arguments specify the largest possible opera-
     tor length	(in bits, important for	public key operations) and flags for
     this algorithm.

     crypto_unregister() is called by drivers that wish	to withdraw support
     for an algorithm.	The two	arguments are the driver and algorithm identi-
     fiers, respectively.  Typically, drivers for PCMCIA crypto	cards that are
     being ejected will	invoke this routine for	all algorithms supported by
     the card.	crypto_unregister_all()	will unregister	all algorithms regis-
     tered by a	driver and the driver will be disabled (no new sessions	will
     be	allocated on that driver, and any existing sessions will be migrated
     to	other drivers).	 The same will be done if all algorithms associated
     with a driver are unregistered one	by one.	 After a call to
     crypto_unregister_all() there will	be no threads in either	the newsession
     or	freesession function of	the driver.

     The calling convention for	the driver-supplied routines are:

     int (*newsession)(device_t, crypto_session_t, struct cryptoini *);
     void (*freesession)(device_t, crypto_session_t);
     int (*process)(device_t, struct cryptop *,	int);
     int (*kprocess)(device_t, struct cryptkop *, int);

     On	invocation, the	first argument to all routines is the device_t that
     was provided to crypto_get_driverid().  The second	argument to
     newsession() is the opaque	session	handle for the new session.  The third
     argument is identical to that of crypto_newsession().

     Drivers obtain a pointer to their session memory by invoking
     crypto_get_driver_session() on the	opaque crypto_session_t	handle.

     The freesession() routine takes as	arguments the opaque data value	and
     the session handle.  It should clear any context associated with the ses-
     sion (clear hardware registers, memory, etc.).  If	no resources need to
     be	released other than the	contents of session memory, the	method is op-
     tional.  The crypto framework will	zero and release the allocated session
     memory (after running the freesession() method, if	one exists).

     The process() routine is invoked with a request to	perform	crypto pro-
     cessing.  This routine must not block or sleep, but should	queue the re-
     quest and return immediately or process the request to completion.	 In
     case of an	unrecoverable error, the error indication must be placed in
     the crp_etype field of the	cryptop	structure.  When the request is	com-
     pleted, or	an error is detected, the process() routine must invoke
     crypto_done().  Session migration may be performed, as mentioned previ-

     In	case of	a temporary resource exhaustion, the process() routine may re-
     turn ERESTART in which case the crypto services will requeue the request,
     mark the driver as	"blocked", and stop submitting requests	for process-
     ing.  The driver is then responsible for notifying	the crypto services
     when it is	again able to process requests through the crypto_unblock()
     routine.  This simple flow	control	mechanism should only be used for
     short-lived resource exhaustion as	it causes operations to	be queued in
     the crypto	layer.	Doing so is preferable to returning an error in	such
     cases as it can cause network protocols to	degrade	performance by treat-
     ing the failure much like a lost packet.

     The kprocess() routine is invoked with a request to perform crypto	key
     processing.  This routine must not	block, but should queue	the request
     and return	immediately.  Upon processing the request, the callback	rou-
     tine should be invoked.  In case of an unrecoverable error, the error in-
     dication must be placed in	the krp_status field of	the cryptkop struc-
     ture.  When the request is	completed, or an error is detected, the
     kprocess()	routine	should invoked crypto_kdone().

     crypto_register(),	crypto_kregister(), crypto_unregister(),
     crypto_newsession(), crypto_freesession(),	and crypto_unblock() return 0
     on	success, or an error code on failure.  crypto_get_driverid() returns a
     non-negative value	on error, and -1 on failure.  crypto_getreq() returns
     a pointer to a cryptop structure and NULL on failure.  crypto_dispatch()
     returns EINVAL if its argument or the callback function was NULL, and 0
     otherwise.	 The callback is provided with an error	code in	case of	fail-
     ure, in the crp_etype field.

     sys/opencrypto/crypto.c  most of the framework code

     crypto(4),	ipsec(4), crypto(7), malloc(9),	sleep(9)

     The cryptographic framework first appeared	in OpenBSD 2.7 and was written
     by	Angelos	D. Keromytis <>.

     The framework currently assumes that all the algorithms in	a
     crypto_newsession() operation must	be available by	the same driver.  If
     that is not the case, session initialization will fail.

     The framework also	needs a	mechanism for determining which	driver is best
     for a specific set	of algorithms associated with a	session.  Some type of
     benchmarking is in	order here.

     Multiple instances	of the same algorithm in the same session are not sup-

FreeBSD	13.0		       December	17, 2019		  FreeBSD 13.0


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