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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_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
     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 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_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
     session 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 before 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
                   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 (crypto_newsession).  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_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
                       provides information about what type of cryptographic
                       operation 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 processed.

                       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
                                            encryption algorithm.  For
                                            encryption, if this bit is set,
                                            nothing is done.  For decryption,
                                            this flag has no meaning.
                                            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.

                                            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 the offset of the IV is
                                            provided 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

                                            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 calculating 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 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 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
     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 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
     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 or sleep, but should queue the
     request 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
     completed, or an error is detected, the process() routine must invoke
     crypto_done().  Session migration may be performed, as mentioned

     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

     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
     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          July 10, 2015         FreeBSD 11.0-PRERELEASE


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