Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
CRYPTO(9)		 BSD Kernel Developer's	Manual		     CRYPTO(9)

     crypto -- API for cryptographic services in the kernel

     #include <opencrypto/cryptodev.h>


     crypto_register(u_int32_t,	int, u_int16_t,	u_int32_t,
	 int (*)(void *, u_int32_t *, struct cryptoini *),
	 int (*)(void *, u_int64_t), int (*)(void *, struct cryptop *),
	 void *);

     crypto_kregister(u_int32_t, int, u_int32_t,
	 int (*)(void *, struct	cryptkop *), void *);

     crypto_unregister(u_int32_t, int);


     crypto_done(struct	cryptop	*);

     crypto_kdone(struct cryptkop *);

     crypto_newsession(u_int64_t *, struct cryptoini *,	int);


     crypto_dispatch(struct cryptop *);

     crypto_kdispatch(struct cryptkop *);

     crypto_unblock(u_int32_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_rnd;
	     caddr_t		cri_key;
	     u_int8_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;
	     struct cryptodesc *crd_next;

     struct cryptop {
	     TAILQ_ENTRY(cryptop) crp_next;
	     u_int64_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 */
	     u_int32_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 an 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_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.  On success, the first argument will contain the
     Session Identifier	(SID).	The second argument contains all the necessary
     information for the driver	to establish the session.  The third argument
     indicates whether a hardware driver (1) should be used or not (0).	 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_rnd   Specifies the number of rounds to be used with the algorithm,
	       for variable-round algorithms.

     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.
	       If no IV	is explicitly passed (see below	on details), a random
	       IV is used by the device	driver processing 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

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

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

		   crd_inject  Offset from the beginning of the	buffer to in-
			       sert any	results.  For encryption algorithms,
			       this is where the initialization	vector (IV)
			       will be inserted	when encrypting	or where it
			       can be found when decrypting (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:

			       CRD_F_ENCRYPT	  For encryption algorithms,
						  this bit is set when encryp-
						  tion is required (when not
						  set, decryption is per-

			       CRD_F_IV_PRESENT	  For encryption algorithms,
						  this bit is set when the IV
						  already precedes the data,
						  so the crd_inject value will
						  be ignored and no IV will be
						  written in the buffer.  Oth-
						  erwise, the IV used to en-
						  crypt	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 encryption algorithm.
						  Some applications 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	typi-
						  cally	used in	conjunction
						  with the CRD_F_IV_EXPLICIT

			       CRD_F_IV_EXPLICIT  For encryption algorithms,
						  this bit is set when the IV
						  is explicitly	provided by
						  the consumer in the cri_iv
						  fields.  Otherwise, for en-
						  cryption operations the IV
						  is provided for by the
						  driver used to perform the
						  operation, whereas for de-
						  cryption operations it is
						  pointed to by	the crd_inject
						  field.  This flag is typi-
						  cally	used when the IV is
						  calculated "on the fly" by
						  the consumer,	and does not
						  precede the data (some
						  ipsec(4) configurations, and
						  the encrypted	swap are two
						  such examples).

			       CRD_F_COMP	  For compression algorithms,
						  this bit is set when com-
						  pression is required (when
						  not set, decompression is

		   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) num-
		    ber	of such	parameters.

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

     krp_kvp	    An array of	kernel memory blocks containing	the parame-

     krp_hid	    Identifier specifying which	low-level driver is being

     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	cc_flags as an argument	(normally 0, but soft-
     ware-only drivers should specify CRYPTOCAP_F_SOFTWARE).  For each algo-
     rithm 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	operator length	(in bits, im-
     portant 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 es-
     tablished context,	and ask	for a request to be processed (encrypt,	de-
     crypt, etc.); and an opaque parameter to pass when	calling	each of	these
     routines.	crypto_unregister() is called by drivers that wish to withdraw
     support for an algorithm.	The two	arguments are the driver and algorithm
     identifiers, respectively.	 Typically, drivers for	PCMCIA crypto cards
     that are being ejected will invoke	this routine for all algorithms	sup-
     ported by the card.  crypto_unregister_all() will unregister all algo-
     rithms registered 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.

     The calling convention for	the three driver-supplied routines is:

     int (*newsession)(void *, u_int32_t *, struct cryptoini *);
     int (*freesession)(void *,	u_int64_t);
     int (*process)(void *, struct cryptop *);
     int (*kprocess)(void *, struct cryptkop *);

     On	invocation, the	first argument to all routines is an opaque data value
     supplied when the algorithm is registered with crypto_register().	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 crypto_newsession().

     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, but	should queue the request and
     return immediately.  Upon processing the request, the callback routine
     should be invoked.	 In case of an unrecoverable error, the	error indica-
     tion must be placed in the	crp_etype field	of the cryptop structure.
     When the request is completed, or an error	is detected, the process()
     routine should invoke crypto_done().  Session migration may be performed,
     as	mentioned previously.

     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

     ipsec(4), 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			       October 14, 2002				   BSD


Want to link to this manual page? Use this URL:

home | help