CRYPTO(9)                    OpenBSD Kernel Manual                   CRYPTO(9)

NAME
     crypto - API for cryptographic services in the kernel

SYNOPSIS
     #include <crypto/crypto>

     int32_t
     crypto_get_driverid(void);

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

     int
     crypto_unregister(u_int32_t, int);

     void
     crypto_done(struct cryptop *);

     int
     crypto_newsession(u_int64_t *, struct cryptoini *);

     int
     crypto_freesession(u_int64_t);

     int
     crypto_dispatch(struct cryptop *);

     struct cryptop *
     crypto_getreq(int);

     void
     crypto_freereq(void);

     #define EALG_MAX_BLOCK_LEN      8

     struct cryptoini
     {
         int                cri_alg;
         int                cri_klen;
         int                cri_rnd;
         caddr_t            cri_key;
         u_int8_t           cri_iv[EALG_MAX_BLOCK_LEN];
         struct cryptoini  *cri_next;
     };

     struct cryptodesc
     {
         int                crd_skip;
         int                crd_len;
         int                crd_inject;
         int                crd_flags;
         struct cryptoini   CRD_INI;
         struct cryptodesc *crd_next;
     };

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

DESCRIPTION
     crypto is a framework for drivers of cryptographic hardware to register
     with the kernel so ``consumers'' (other kernel subsystems, and eventually
     users through an appropriate device) are able to make use of it.  Drivers
     register with the framework the algorithms they support, and provide en-
     try 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 regis-
     tered with it) of the operations that should be applied on the data (more
     than one cryptographic operation can be requested).

     Since the consumers may not be associated with a process, drivers may not
     use tsleep(9). The same holds for the framework.  Thus, a callback mecha-
     nism 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 initializa-
     tion 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 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 various fields
     in the cryptoini structure are:

     cri_alg       Contains an algorithm identifier.  Currently supported al-
                   gorithms are:

                   CRYPTO_DES_CBC
                   CRYPTO_3DES_CBC
                   CRYPTO_BLF_CBC
                   CRYPTO_CAST_CBC
                   CRYPTO_SKIPJACK_CBC
                   CRYPTO_MD5_HMAC96
                   CRYPTO_SHA1_HMAC96
                   CRYPTO_RIPEMD160_HMAC96
                   CRYPTO_MD5_KPDK
                   CRYPTO_SHA1_KPDK

     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 de-
                   tails), a random IV is used by the device driver processing

                   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
                   feature).

     The cryptoini structure and its contents will not be modified by the
     framework (or the drivers used).  Subsequent requests for processing that
     use the SID returned will avoid the cost of re-initializing the hardware
     (in essence, SID acts as an index in the session cache of the driver).

     crypto_freesession() is called with the SID returned by
     crypto_newsession() to disestablish the session.

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

     crp_sid        Contains the SID.

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

     crp_olen       On return, contains the total length of the result.  For
                    symmetric crypto operations, this will be the same as the
                    input length.

     crp_alloctype  Indicates the type of buffer, as used in the kernel mal-
                    loc(9) routine.  This will be used if the framework needs
                    to allocate a new buffer for the result (or for re-format-
                    ting 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 appro-
                    priate 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 re-
                    quests.  In this case, the request may be re-submitted im-
                    mediately.  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 re-
                    turned 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.  Cur-
                    rently defined flags are:

                    CRYPTO_F_IMBUF  The buffer pointed to by crp_buf is an
                                    mbuf chain.




     crp_buf        Points to the input buffer.  On return (when the callback
                    is invoked), it contains the result of the request.  The
                    input buffer may be an mbuf chain or a contiguous buffer
                    (of a type identified by crp_alloctype), 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 op-
                    eration should be done on the input buffer.  The various
                    fields are:

                    crd_skip
                      The offset in the input buffer where processing should
                      start.

                    crd_len
                      How many bytes, after crd_skip, should be processed.

                    crd_inject
                      Offset from the beginning of the buffer to insert any
                      results.  For encryption algorithms, this is where the
                      initialization vector (IV) will be inserted when en-
                      crypting or where it can be found when decrypting (sub-
                      ject to crd_flags). For MAC algorithms, this is where
                      the result of the keyed hash will be inserted.

                    crd_flags
                      The following flags are defined:

                      CRD_F_ENCRYPT      For encryption algorithms, this bit
                                         is set when encryption is required
                                         (when not set, decryption is per-
                                         formed).

                      CRD_F_IV_PRESENT   For encryption algorithms, this bit
                                         is set when the IV already precedes
                                         the data, so the crd_inject value
                                         will be ignored and no IV will be
                                         written in the buffer.  Otherwise,
                                         the IV used to encrypt the packet
                                         will be written at the location
                                         pointed to by crd_inject. The IV
                                         length is assumed to be equal to the
                                         blocksize of the encryption algo-
                                         rithm.  Some applications that do
                                         special ``IV cooking'', such as the
                                         half-IV mode in ipsec(4), can use
                                         this flag to indicate the the IV
                                         should not be written on the packet.
                                         This flag is typically used in con-
                                         junction with the CRD_F_IV_EXPLICIT
                                         flag.

                      CRD_F_IV_EXPLICIT  For encryption algorithms, this bit
                                         is set when the IV is explicitly pro-
                                         vided by the consumer in the crd_iv
                                         fields.  Otherwise, for encryption
                                         operations the IV is provided for by
                                         the driver used to perform the opera-
                                         tion, whereas for decryption opera-
                                         tions 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 en-
                                         crypted swap are two such examples).

                    crd_alg, crd_klen, crd_rnd, crd_key, crd_iv
                      These have the exact same meaning as the corresponding
                      fields in the cryptoini structure.  These fields 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 call-
     back routine to do the necessary cleanups associated with the opaque
     field in the cryptop structure.

DRIVER-SIDE API
     The crypto_get_driverid(), crypto_register(), crypto_unregister(), and
     crypto_done() routines are used by drivers that provide support for cryp-
     tographic 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.  For each algorithm the driver
     supports, it must then call crypto_register().  The first two arguments
     are the driver and algorithm identifiers.  The last three 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.)  crypto_unregister() is called by
     drivers that wish to withdraw support for an algorithm.  The two argu-
     ments are the driver and algorithm identifiers, respectively.  Typically,
     drivers for pcmcia(4) crypto cards that are being ejected will invoke
     this routine for all algorithms supported by the card.

     The calling convention for the three driver-supplied routines is:

     int (*newsession) (u_int32_t *, struct cryptoini *);
     int (*freesession) (u_int64_t);
     int (*process) (struct cryptop *);

     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.  When the request is
     completed, or an error is detected, the process() routine should invoked
     crypto_done().  Session migration may be performed, as mentioned previ-
     ously.

RETURN VALUES
     crypto_register(), crypto_unregister(), crypto_newsession(), and
     crypto_freesession() return 0 on success, or an error code on failure.
     crypto_get_driverid() returns a non-negative value on error, and -1 on
     failure.  crypto_getreq() returns a pointer to a cryptop structure and
     NULL on failure.  crypto_dispatch() returns EINVAL is its argument or the
     callback function was NULL, and 0 otherwise.  The callback is provided
     with an error code in case of failure, in the crp_etype field.

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

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

BUGS
     The framework currently assumes that all the algorithms in a
     crypto_newsession() operation must be available by the same driver.  If
     that's not the case, session initialization will fail.

     The framework also needs a mechanism for determining which driver is best
     for a specific set of algorithms associated with a session.  Some type of
     benchmarking is in order here.

     Multiple instances of the same algorithm in the same session are not sup-
     ported.  Note that 3DES is considered one algorithm (and not three in-
     stances of DES).  Thus, 3DES and DES could be mixed in the same request.

     A queue for completed operations should be implemented and processed at
     some software spl(9) level, to avoid overall system latency issues, and
     potential kernel stack exhaustion while processing a callback.

     We need a userland device for exposing the framework to userland.  This
     will be particularly useful for public key operations in hardware.

     We have not experimented yet with public key operations hardware.  The
     framework should support this.

     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-
     port).

OpenBSD 2.8                     April 21, 2000                               6
