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

     opencrypto, crypto_get_driverid, crypto_register, crypto_kregister,
     crypto_unregister, crypto_unregister_all, crypto_done, crypto_kdone,
     crypto_newsession, crypto_freesession, crypto_dispatch, crypto_kdispatch,
     crypto_getreq, crypto_freereq crypto_kgetreq, crypto_kfreereq -- 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_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 *);

     struct cryptop *
     crypto_kgetreq(int, int);

     crypto_kfreereq(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 regis-
     ter with the kernel so ``consumers'' (other kernel subsystems, and even-
     tually users through an appropriate device) are able to make use of it.
     Drivers register with the framework the algorithms they support, and pro-
     vide entry points (functions) the framework may call to establish, use,
     and tear down sessions.  Sessions are used to cache cryptographic infor-
     mation 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 opera-
     tions using input and output parameters.

     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 pro-
     vided 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 mechanism is used for session initialization and

     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 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 algo-
                   rithm, 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 initial-
                   ization.  If no IV is explicitly passed (see below on
                   details), a random IV is used by the device driver process-
                   ing the request.

     cri_next      Contains a pointer to another cryptoini structure.  Multi-
                   ple such structures may be linked to establish multi-algo-
                   rithm sessions (ipsec(4) is an example consumer of such a

     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 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
                   responsibility of the callback routine to set the appropri-
                   ate 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 considera-

                   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 rou-
                   tine (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.  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
                   (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 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
                               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 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
                                                  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 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 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 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 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 operation has a (typically hardwired) num-
                    ber of such parameters.

     krp_oparams    Number of 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.

     crypto_kgetreq() allocates a cryptkop structure.  The first argument
     means the same as crypto_getreq().  The second argument means flags
     passed to pool_get().

     crypto_kfreereq() deallocates a structure cryptkop structure.

     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 requests.

     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-acceler-
                                           ated operations (handling the lat-
                                           ter in software).

                                      > 0  Allow user requests only for opera-
                                           tions which are hardware-acceler-

     opencrypto.crypto_ret_q.maxlen   Limit the length of queue(crypto_ret_q)
                                      which mediates between crypto driver's
                                      completion and calling cryptop callback.
                                      When the queue exceeds this limit,
                                      crypto_getreq() fails.

                                      <= 0  means unlimited.

     opencrypto.crypto_ret_kq.maxlen  Limit the length of queue(crypto_ret_kq)
                                      which mediates between crypto driver's
                                      completion and calling cryptkop call-
                                      back.  When the queue exceeds this
                                      limit, crypto_kgetreq() fails.

                                      <= 0  means unlimited.

     The following sysctl entries exist to get statistics.

     opencrypto.crypto_ret_q.len     Current crypto_ret_q length.

     opencrypto.crypto_ret_q.drops   The count of crypto_getreq() failed as
                                     overflow opencrypto.crypto_ret_q.maxlen.

     opencrypto.crypto_ret_kq.len    Current crypto_ret_kq length.

     opencrypto.crypto_ret_kq.drops  The count of crypto_kgetreq() failed as
                                     overflow opencrypto.crypto_ret_kq.maxlen.

     The crypto_get_driverid(), crypto_register(), crypto_kregister(),
     crypto_unregister(), crypto_unregister_all(), and crypto_done() routines
     are used by drivers that provide support for cryptographic primitives to
     register and unregister with the kernel crypto services framework.  Driv-
     ers must first use the crypto_get_driverid() function to acquire a driver
     identifier, specifying the 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 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-pro-
     vided functions that the framework may call to establish new crypto-
     graphic 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 identi-
     fiers, respectively.  algorithms supported by the card.  If all algo-
     rithms associated with a driver are unregistered, the driver will be dis-
     abled (no new sessions will be allocated on that driver, and any existing
     sessions will be migrated to other drivers).  crypto_unregister_all()
     will unregister all registered algorithms, disable the driver, and
     migrate existing sessions to other drivers.

     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 return-
     ing, 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 con-
     catenation of the driver identifier and the driver-specific session iden-
     tifier).  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 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 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 processing the request, the callback rou-
     tine 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().

     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_kgetreq() returns a
     pointer to a cryptkop 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

     sys/crypto               crypto algorithm implementations

     ipsec(4), pcmcia(4), condvar(9), malloc(9), pool(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 <>.

     Sam Leffler ported the crypto framework to FreeBSD and made performance

     Jonathan Stone <> 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 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
     instances of DES).  Thus, 3DES and DES could be mixed in the same

     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 sup-

NetBSD 9.0                       May 26, 2017                       NetBSD 9.0

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