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CRYPTO(9)		     OpenBSD Kernel Manual		     CRYPTO(9)

NAME
     crypto - API for cryptographic services in the kernel

SYNOPSIS
     #include <crypto/cryptodev.h>

     int32_t
     crypto_get_driverid(u_int8_t);

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

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

     int
     crypto_unregister(u_int32_t, int);

     void
     crypto_done(struct cryptop *);

     void
     crypto_kdone(struct cryptkop *);

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

     int
     crypto_freesession(u_int64_t);

     int
     crypto_dispatch(struct cryptop *);

     int
     crypto_kdispatch(struct cryptkop *);

     struct cryptop *
     crypto_getreq(int);

     void
     crypto_freereq(struct cryptop *);

     #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 {
	     u_int64_t		crp_sid;
	     int		crp_ilen;
	     int		crp_olen;
	     int		crp_alloctype;
	     int		crp_etype;
	     int		crp_flags;
	     void	       *crp_buf;
	     void	       *crp_opaque;
	     struct cryptodesc *crp_desc;
	     int	      (*crp_callback)(struct cryptop *);
	     struct cryptop    *crp_next;
	     caddr_t		crp_mac;
     };

     struct crparam {
	     caddr_t	     crp_p;
	     u_int	     crp_nbits;
     };

     #define CRK_MAXPARAM    8

     struct cryptkop {
	     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];      /* kvm */
	     int	       (*krp_callback)(struct cryptkop *);
	     struct cryptkop   *krp_next;
     };

DESCRIPTION
     crypto 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.	 Consumers 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 parameters.

     Since the consumers may not be associated with a process, drivers may not
     use tsleep(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 a 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).  For session
     initialization 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
     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:

		   CRYPTO_DES_CBC
		   CRYPTO_3DES_CBC
		   CRYPTO_BLF_CBC
		   CRYPTO_CAST_CBC
		   CRYPTO_MD5_HMAC
		   CRYPTO_SHA1_HMAC
		   CRYPTO_RIPEMD160_HMAC
		   CRYPTO_MD5_KPDK
		   CRYPTO_SHA1_KPDK
		   CRYPTO_AES_CBC
		   CRYPTO_AES_CTR
		   CRYPTO_AES_XTS
		   CRYPTO_ARC4
		   CRYPTO_MD5
		   CRYPTO_SHA1

     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
		   processing the request.

		   In the case of the CRYPTO_AES_XTS transform, the IV should
		   be provided as a 64-bit block number in host byte order.

     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 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
		    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.

     crp_alloctype  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
		    responsibility 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 callback
		    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 are:

		    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 contains the result of the request.	 The
		    input buffer may be an mbuf chain or a struct uio
		    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
		    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	The following flags are defined:

				CRD_F_ENCRYPT	   For encryption algorithms,
						   this bit is set when
						   encryption is required
						   (when not set, decryption
						   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.	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
						   typically used in
						   conjunction with the
						   CRD_F_IV_EXPLICIT flag.

				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
						   encryption 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
				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
     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 cryptkop 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 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.

DRIVER-SIDE API
     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 cc_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 algorithm 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) (u_int32_t *, struct cryptoini *);
     int (*freesession) (u_int64_t);
     int (*process) (struct cryptop *);
     int (*kprocess) (struct cryptkop *);

     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.	 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 processing the request, the callback
     routine should be invoked.	 In case of error, the error indication 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().

RETURN VALUES
     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 field.

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

SEE ALSO
     ipsec(4), pcmcia(4), malloc(9), tsleep(9)

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

BUGS
     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 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
     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).

OpenBSD 4.9			October 6, 2010			   OpenBSD 4.9
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