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     crypto — API for cryptographic services in the kernel


     #include <opencrypto/cryptodev.h>

     crypto_get_driverid(device_t, size_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(crypto_session_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;
             crypto_session_t   crp_session;
             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

     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 handle has changed and that the request may
     be re-submitted immediately with the new session.  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 no
     callback mechanism is 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 opaque session handle.  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).

     crypto_freesession() is called with the session handle returned by crypto_newsession() to
     free the session.

     crypto_dispatch() is called to process a request.  The various fields in the cryptop
     structure are:

     crp_session   Contains the session handle.

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

     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
                   session handle has changed (and has been recorded in the crp_session field).
                   The consumer should record the new session handle 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

                   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).

                   CRYPTO_F_ASYNC     Try to do the crypto operation in a pool of workers if the
                                      operation is synchronous (that is, if the driver specified
                                      the CRYPTOCAP_F_SYNC flag).  It aims to speed up processing
                                      by dispatching crypto operations on different processors.

                                      Dispatch callbacks in the same order they are posted.  Only
                                      relevant if the CRYPTO_F_ASYNC flag is set and if the
                                      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      When the flag CRD_F_IV_EXPLICIT is set, this field contains the

                   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

                   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 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 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 parameters.

     krp_hid       Identifier specifying which low-level driver is being used.

     krp_callback  Callback called on completion of a keying operation.


     The crypto_get_driverid(), crypto_get_driver_session(), 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_SOFTWARE or CRYPTOCAP_F_HARDWARE
     must be specified.  The CRYPTOCAP_F_SYNC may also be specified, and should be specified if
     the driver does all of it's operations synchronously.  Drivers must pass the size of their
     session struct as the second argument.  An appropriately sized memory will be allocated by
     the framework, zeroed, and passed to the driver's newsession() method.

     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

     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 driver-supplied routines are:

     int (*newsession)(device_t, crypto_session_t, struct cryptoini *);
     void (*freesession)(device_t, crypto_session_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() is the opaque session handle for
     the new session.  The third argument is identical to that of crypto_newsession().

     Drivers obtain a pointer to their session memory by invoking crypto_get_driver_session() on
     the opaque crypto_session_t handle.

     The freesession() routine takes as arguments the opaque data value and the session handle.
     It should clear any context associated with the session (clear hardware registers, memory,
     etc.).  If no resources need to be released other than the contents of session memory, the
     method is optional.  The crypto framework will zero and release the allocated session memory
     (after running the freesession() method, if one exists).

     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 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


     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

     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.