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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_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_mlen;
             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;
     #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;
             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
     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
     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
     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).  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 (1) should be used 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_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.  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 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

     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 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

                       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.

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

                       CRYPTO_F_REL           Must return data in the same

                       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.

     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
                       provides information about what type of cryptographic
                       operation should be done on the input buffer.  The
                       various fields are:

                       crd_iv          The field where IV should be provided
                                       when the CRD_F_IV_EXPLICIT flag is

                       crd_key         When the CRD_F_KEY_EXPLICIT flag is
                                       given, 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 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:

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

                                            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.

                                            For encryption algorithms, this
                                            bit is set when the IV is
                                            explicitly provided by the
                                            consumer in the crd_iv field.
                                            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).

                                            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.

                                            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

     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 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

     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
     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 two arguments are the driver and algorithm identifiers.  The next
     two arguments specify the largest possible operator 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,
     decrypt, 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 supported by the card.  crypto_unregister_all() will
     unregister all algorithms 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

     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
     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 an unrecoverable 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.

     In case of a temporary resource exhaustion, the process() routine may
     return ERESTART in which case the crypto services will requeue the
     request, mark the driver as ``blocked'', and stop submitting requests for
     processing.  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
     treating 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
     routine should be invoked.  In case of an unrecoverable 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 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
     failure, 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
     supported.  Note that 3DES is considered one algorithm (and not three
     instances of DES).  Thus, 3DES and DES could be mixed in the same

FreeBSD 11.0-PRERELEASE       September 19, 2007       FreeBSD 11.0-PRERELEASE


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