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NetBSD 6.1.5 - man page for crypto_freesession (netbsd section 9)

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

     opencrypto, crypto_get_driverid, crypto_register, crypto_kregister, crypto_unregister,
     crypto_done, crypto_kdone, crypto_newsession, crypto_freesession, crypto_dispatch,
     crypto_kdispatch, crypto_getreq, crypto_freereq -- API for cryptographic services in the

     #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_int32_t *),
	 int (*)(u_int64_t), int (*)(struct cryptop *), void *);

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

     struct cryptop *

     crypto_freereq(struct cryptop *);

     #define EALG_MAX_BLOCK_LEN      16

     struct cryptoini {
	     int		cri_alg;
	     int		cri_klen;
	     int		cri_rnd;
	     void	     *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;
	     void	     *crp_buf;
	     void	     *crp_opaque;
	     struct cryptodesc *crp_desc;
	     int	      (*crp_callback)(struct cryptop *);
	     void	     *crp_mac;

     struct crparam {
	     void	  *crp_p;
	     u_int	     crp_nbits;

     #define CRK_MAXPARAM    8

     struct cryptkop {
	     TAILQ_ENTRY(cryptkop) krp_next;
	     u_int		krp_op; 	/* i.e. 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];       /* kvm */
	     int	       (*krp_callback)(struct cryptkop *);

     opencrypto is a framework for drivers of cryptographic hardware to register with the kernel
     so ``consumers'' (other kernel subsystems, and eventually users through an appropriate
     device) are able to make use of it.  Drivers register 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.  Con-
     sumers of cryptographic services pass a set of descriptors that instruct the framework (and
     the drivers registered 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 operations using input and output parame-

     Since the consumers may not be associated with a process, drivers may not use condition
     variables: condvar(9).  The same holds for the framework.	Thus, a callback mechanism is
     used to notify a consumer that a request has been completed (the callback is specified by
     the consumer on an per-request basis).  The callback is invoked by the framework whether the
     request was successfully completed 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).  No callback mecha-
     nism is used for session initialization and teardown.

     The crypto_newsession() routine is called by consumers of cryptographic services (such as
     the ipsec(4) stack) that wish to establish a new session 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 should be used (1) or not (0).  The various fields in
     the cryptoini structure are:

     cri_alg	   Contains an algorithm identifier.  Currently supported algorithms are:


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

     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 pro-
		   cessing the request.

     cri_next	   Contains a pointer to another cryptoini structure.  Multiple such structures
		   may be linked to establish multi-algorithm sessions (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 driv-
     ers 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 struc-
     ture are:

     crp_sid	   Contains the SID.

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

     crp_olen	   On return, contains the length of the result, not including crd_skip.  For
		   symmetric crypto operations, this will be the same as the input length.

		   Indicates the type of buffer, as used in the kernel malloc(9) routine.  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 responsi-
		   bility 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, because of availability, performance, or other considerations).

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

     crp_flags	   Is a bitmask of flags associated with this request.	Currently defined flags

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

     crp_buf	   Points to the input buffer.	On return (when the callback is invoked), it con-
		   tains the result of the request.  The input buffer may be an mbuf chain or a
		   contiguous buffer (of a type identified by crp_alloctype), depending on

     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 provides information
		   about what type of cryptographic operation 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 processed.

		   crd_inject  Offset from the beginning of the buffer to insert 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   For adjusting general operation from userland, the following flags
			       are defined:

			       CRD_F_ENCRYPT	  For encryption algorithms, this bit is set when
						  encryption is required (when not set, decryp-
						  tion is performed).

			       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.  Otherwise, the IV
						  used to encrypt the packet will be written at
						  the location pointed to by crd_inject.  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 typically
						  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 crd_iv fields.  Otherwise, for encryp-
						  tion operations the IV is provided for by the
						  driver used to perform the operation, whereas
						  for decryption operations it is pointed to by
						  the crd_inject field.  This flag is typically
						  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 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
			       cryptographic operation request, drivers may re-initialize 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 above.

		   crd_next    Point to the next descriptor.  Linked operations are useful in
			       protocols such as ipsec(4), where multiple cryptographic trans-
			       forms 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 it.

     crypto_freereq() deallocates a structure cryptop and any cryptodesc structures linked to it.
     Note that it is the responsibility of the callback 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
     crytokop structure are:

     krp_op	    Operation code, such as CRK_MOD_EXP.

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

     krp_iparams    Number of input parameters to the specified operation.  Note that each opera-
		    tion 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 following sysctl entries exist to adjust the behaviour of the system from userland:

     kern.usercrypto	      Allow (1) or forbid (0) userland access to /dev/crypto.

     kern.userasymcrypto      Allow (1) or forbid (0) userland access to do asymmetric crypto

     kern.cryptodevallowsoft  Enable/disable access to hardware versus software operations:

			      < 0  Force userlevel requests to use software operations, always.

			      = 0  Use hardware if present, grant userlevel requests for non-
				   accelerated operations (handling the latter in software).

			      > 0  Allow user requests only for operations which are hardware-

     The crypto_get_driverid(), crypto_register(), crypto_kregister(), crypto_unregister(), 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 (normally 0, but software-only drivers should specify CRYPTOCAP_F_SOFTWARE).
     For each algorithm the driver supports, it must then call crypto_register().  The first
     argument is the driver identifier.  The second argument is an array of CRYPTO_ALGORITHM_MAX
     + 1 elements, indicating which algorithms are supported.  The last three arguments 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, decrypt, etc.)  crypto_unregister() is called by drivers
     that wish to withdraw support for an algorithm.  The two arguments are the driver and algo-
     rithm identifiers, respectively.  Typically, drivers for pcmcia(4) crypto cards that are
     being ejected will invoke this routine for all algorithms supported by the card.  If called
     with CRYPTO_ALGORITHM_ALL, all algorithms registered for a driver will be unregistered in
     one go 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);

     On invocation, the first argument to newsession() contains the driver identifier obtained
     via crypto_get_driverid().  On successfully returning, it should contain a driver-specific
     session identifier.  The second argument is identical to that of crypto_newsession().

     The freesession() routine takes as argument the SID (which is the concatenation of the
     driver identifier and the driver-specific session identifier).  It should clear any context
     associated with the session (clear hardware registers, memory, etc.).

     The process() routine is invoked with a request to perform crypto processing.  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 error, the error indication
     must be placed in the crp_etype field of the cryptop structure.  The hint argument can be
     set to CRYPTO_HINT_MORE when there will be more request right after this request.	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.

     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 process-
     ing the request, the callback routine should be invoked.  In case of error, the error indi-
     cation must be placed in the krp_status field of the cryptkop structure.  When the request
     is completed, or an error is detected, the kprocess() routine should invoke crypto_kdone().

     crypto_register(), crypto_kregister(), crypto_unregister(), crypto_newsession(), and
     crypto_freesession() 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 failure, in the crp_etype

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

     sys/crypto 	      crypto algorithm implementations

     ipsec(4), pcmcia(4), condvar(9), malloc(9)

     Angelos D. Keromytis, Jason L. Wright, and Theo de Raadt, The Design of the OpenBSD
     Cryptographic Framework, Usenix, 2003, June 2003.

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

     Sam Leffler ported the crypto framework to FreeBSD and made performance improvements.

     Jonathan Stone <jonathan@NetBSD.org> ported the cryptoframe from FreeBSD to NetBSD.
     opencrypto first appeared in NetBSD 2.0.

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

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

     A queue for completed operations should be implemented and processed at some software spl(9)
     level, to avoid overall system latency issues, and potential kernel stack exhaustion while
     processing a callback.

     When SMP time comes, we will support use of a second processor (or more) as a crypto device
     (this is actually AMP, but we need the same basic support).

BSD					September 17, 2011				      BSD

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