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

     crypto -- API for cryptographic services in the kernel

     #include <opencrypto/cryptodev.h>

     crypto_get_driverid(device_t, int);

     crypto_register(uint32_t, int, uint16_t, uint32_t,
	 int (*)(void *, uint32_t *, struct cryptoini *),
	 int (*)(void *, uint64_t), int	(*)(void *, struct cryptop *),
	 void *);

     crypto_kregister(uint32_t,	int, uint32_t,
	 int (*)(void *, struct	cryptkop *), void *);

     crypto_unregister(uint32_t, int);


     crypto_done(struct	cryptop	*);

     crypto_kdone(struct cryptkop *);

     crypto_find_driver(const char *);

     crypto_newsession(uint64_t	*, struct cryptoini *, int);


     crypto_dispatch(struct cryptop *);

     crypto_kdispatch(struct cryptkop *);

     crypto_unblock(uint32_t, int);

     struct cryptop *


     #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;
	     uint64_t		crp_sid;
	     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 number
     has changed and that the request may be re-submitted immediately with the
     new session number.  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 initializa-
     tion and teardown there is	no callback mechanism used.

     The crypto_find_driver() function may be called to	return the specific id
     of	the provided name.  If the specified driver could not be found,	the
     returned id is -1.

     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 second argument contains all	the necessary
     information for the driver	to establish the session.  The third argument
     is	either a specific driver id, or	one or both of CRYPTOCAP_F_HARDWARE,
     to	select hardware	devices, or CRYPTOCAP_F_SOFTWARE, to select software
     devices.  If both are specified, a	hardware device	will be	returned be-
     fore a software device will be.  On success, the value pointed to by the
     first argument will be the	Session	IDentifier (SID).  The various fields
     in	the cryptoini structure	are:

     cri_alg   Contains	an algorithm identifier.  Currently supported algo-
	       rithms are:


     cri_klen  Specifies the length of the key in bits,	for variable-size key

     cri_mlen  Specifies how many bytes	from the calculated hash should	be
	       copied back.  0 means entire hash.

     cri_key   Contains	the key	to be used with	the algorithm.

     cri_iv    Contains	an explicit initialization vector (IV),	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  Contains	a pointer to another cryptoini structure.  Multiple
	       such structures may be linked to	establish multi-algorithm ses-
	       sions (ipsec(4) is an example consumer of such a	feature).

     The cryptoini structure and its contents will not be modified by the
     framework (or the drivers used).  Subsequent requests for processing that
     use the SID returned will avoid the cost of re-initializing the hardware
     (in essence, SID acts as an index in the session cache of the driver).

     crypto_freesession() is called with the SID returned by
     crypto_newsession() to disestablish the session.

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

     crp_sid	   Contains the	SID.

     crp_ilen	   Indicates the total length in bytes of the buffer to	be

     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  This	routine	is invoked upon	completion of the request,
		   whether successful or not.  It is invoked through the
		   crypto_done() routine.  If the request was not successful,
		   an error code is set	in the crp_etype field.	 It is the re-
		   sponsibility	of the callback	routine	to set the appropriate
		   spl(9) level.

     crp_etype	   Contains the	error type, if any errors were encountered, or
		   zero	if the request was successfully	processed.  If the
		   EAGAIN error	code is	returned, the SID has changed (and has
		   been	recorded in the	crp_sid	field).	 The consumer should
		   record the new SID and use it in all	subsequent requests.
		   In this case, the request may be re-submitted immediately.
		   This	mechanism is used by the framework to perform session
		   migration (move a session from one driver to	another, be-
		   cause of availability, performance, or other	considera-

		   Note	that this field	only makes sense when examined by the
		   callback routine specified in crp_callback.	Errors are re-
		   turned to the invoker of crypto_process() only when enough
		   information is not present to call the callback routine
		   (i.e., if the pointer passed	is NULL	or if no callback rou-
		   tine	was specified).

     crp_flags	   Is a	bitmask	of flags associated with this request.	Cur-
		   rently defined flags	are:

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

		   CRYPTO_F_IOV	      The buffer pointed to by crp_buf is an
				      uio structure.

		   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).

     crp_buf	   Points to the input buffer.	On return (when	the callback
		   is invoked),	it contains the	result of the request.	The
		   input buffer	may be an mbuf chain or	a contiguous buffer,
		   depending on	crp_flags.

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

     crp_desc	   This	is a linked list of descriptors.  Each descriptor pro-
		   vides information about what	type of	cryptographic opera-
		   tion	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 (some ipsec(4)
				    configurations, and	the encrypted swap are
				    two	such examples).

				    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 as
     many cryptodesc structures	as were	specified in the argument passed to

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

     krp_oparams   Number if 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_register(), crypto_kregister(),
     crypto_unregister(), crypto_unblock(), and	crypto_done() routines are
     used by drivers that provide support for cryptographic primitives to reg-
     ister 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.

     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.  The last four arguments must be provided in the first
     call to crypto_register() and are ignored in all subsequent calls.	 They
     are pointers to three driver-provided functions that the framework	may
     call to establish new cryptographic context with the driver, free already
     established context, and ask for a	request	to be processed	(encrypt, de-
     crypt, etc.); and an opaque parameter to pass when	calling	each of	these

     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 three driver-supplied routines are:

     int (*newsession)(device_t, uint32_t *, struct cryptoini *);
     int (*freesession)(device_t, uint64_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() contains the driver identifier obtained via
     crypto_get_driverid().  On	successful return, it should contain a driver-
     specific session identifier.  The third argument is identical to that of

     The freesession() routine takes as	arguments the opaque data value	and
     the SID (which is the concatenation of the	driver identifier and the
     driver-specific session identifier).  It should clear any context associ-
     ated with the session (clear hardware registers, memory, etc.).

     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-
     ported.  Note that	3DES is	considered one algorithm (and not three	in-
     stances of	DES).  Thus, 3DES and DES could	be mixed in the	same request.

BSD				 July 10, 2015				   BSD


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