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NAME

     crypto - API for cryptographic services in the kernel

SYNOPSIS

     #include <opencrypto/cryptodev.h>

     int32_t
     crypto_get_driverid(u_int8_t);

     int
     crypto_register(u_int32_t, int, u_int16_t, u_int32_t,
             int (*)(void *, u_int32_t *, struct cryptoini *),
             int (*)(void *, u_int64_t), int (*)(void *, struct cryptop *),
             void *);

     int
     crypto_kregister(u_int32_t, int, u_int32_t,
             int (*)(void *, struct cryptkop *), void *);

     int
     crypto_unregister(u_int32_t, int);

     int
     crypto_unregister_all(u_int32_t);

     void
     crypto_done(struct cryptop *);

     void
     crypto_kdone(struct cryptkop *);

     int
     crypto_newsession(u_int64_t *, struct cryptoini *, int);

     int
     crypto_freesession(u_int64_t);

     int
     crypto_dispatch(struct cryptop *);

     int
     crypto_kdispatch(struct cryptkop *);

     int
     crypto_unblock(u_int32_t, int);

     struct cryptop *
     crypto_getreq(int);

     void
     crypto_freereq(void);

     #define CRYPTO_SYMQ     0x1
     #define CRYPTO_ASYMQ    0x2

     #define EALG_MAX_BLOCK_LEN      16

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

     struct cryptodesc {
             int                crd_skip;
             int                crd_len;
             int                crd_inject;
             int                crd_flags;
             struct cryptoini   CRD_INI;
     #define crd_iv          CRD_INI.cri_iv
     #define crd_key         CRD_INI.cri_key
     #define crd_alg         CRD_INI.cri_alg
     #define crd_klen        CRD_INI.cri_klen
             struct cryptodesc *crd_next;
     };

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

     struct crparam {
             caddr_t         crp_p;
             u_int           crp_nbits;
     };

     #define CRK_MAXPARAM    8

     struct cryptkop {
             TAILQ_ENTRY(cryptkop) krp_next;
             u_int              krp_op;         /* ie. CRK_MOD_EXP or other */
             u_int              krp_status;     /* return status */
             u_short            krp_iparams;    /* # of input parameters */
             u_short            krp_oparams;    /* # of output parameters */
             u_int32_t          krp_hid;
             struct crparam     krp_param[CRK_MAXPARAM];
             int               (*krp_callback)(struct cryptkop *);
     };

DESCRIPTION

     crypto is a framework for drivers of cryptographic hardware to register
     with the kernel so “consumers” (other kernel subsystems, and users
     through the /dev/crypto device) are able to make use of it.  Drivers
     register with the framework the algorithms they support, and provide
     entry points (functions) the framework may call to establish, use, and
     tear down sessions.  Sessions are used to cache cryptographic information
     in a particular driver (or associated hardware), so initialization is not
     needed with every request.  Consumers of cryptographic services pass a
     set of descriptors that instruct the framework (and the drivers
     registered with it) of the operations that should be applied on the data
     (more than one cryptographic operation can be requested).

     Keying operations are supported as well.  Unlike the symmetric operators
     described above, these sessionless commands perform mathematical
     operations using input and output parameters.

     Since the consumers may not be associated with a process, drivers may not
     sleep(9).  The same holds for the framework.  Thus, a callback mechanism
     is used to notify a consumer that a request has been completed (the
     callback is specified by the consumer on an per-request basis).  The
     callback is invoked by the framework whether the request was successfully
     completed or not.  An error indication is provided in the latter case.  A
     specific error code, EAGAIN, is used to indicate that a session number
     has changed and that the request may be re-submitted immediately with the
     new session number.  Errors are only returned to the invoking function if
     not enough information to call the callback is available (meaning, there
     was a fatal error in verifying the arguments).  For session
     initialization and teardown there is no callback mechanism used.

     The crypto_newsession() routine is called by consumers of cryptographic
     services (such as the ipsec(4) stack) that wish to establish a new
     session with the framework.  On success, the first argument will contain
     the Session Identifier (SID).  The second argument contains all the
     necessary information for the driver to establish the session.  The third
     argument indicates whether a hardware driver (1) should be used or not
     (0).  The various fields in the cryptoini structure are:

     cri_alg   Contains an algorithm identifier.  Currently supported
               algorithms are:

               CRYPTO_AES_CBC
               CRYPTO_ARC4
               CRYPTO_BLF_CBC
               CRYPTO_CAMELLIA_CBC
               CRYPTO_CAST_CBC
               CRYPTO_DES_CBC
               CRYPTO_3DES_CBC
               CRYPTO_SKIPJACK_CBC
               CRYPTO_MD5
               CRYPTO_MD5_HMAC
               CRYPTO_MD5_KPDK
               CRYPTO_RIPEMD160_HMAC
               CRYPTO_SHA1
               CRYPTO_SHA1_HMAC
               CRYPTO_SHA1_KPDK
               CRYPTO_SHA2_256_HMAC
               CRYPTO_SHA2_384_HMAC
               CRYPTO_SHA2_512_HMAC
               CRYPTO_NULL_HMAC
               CRYPTO_NULL_CBC

     cri_klen  Specifies the length of the key in bits, for variable-size key
               algorithms.

     cri_mlen  Specifies how many bytes from the calculated hash should be
               copied back.  0 means entire hash.

     cri_key   Contains the key to be used with the algorithm.

     cri_iv    Contains an explicit initialization vector (IV), if it does not
               prefix the data.  This field is ignored during initialization.
               If no IV is explicitly passed (see below on details), a random
               IV is used by the device driver processing the request.

     cri_next  Contains a pointer to another cryptoini structure.  Multiple
               such structures may be linked to establish multi-algorithm
               sessions (ipsec(4) is an example consumer of such a feature).

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

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

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

     crp_sid       Contains the SID.

     crp_ilen      Indicates the total length in bytes of the buffer to be
                   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 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
                   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 are:

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

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

                   CRYPTO_F_REL       Must return data in the same place.

                   CRYPTO_F_BATCH     Batch operation if possible.

                   CRYPTO_F_CBIMM     Do callback immediately instead of doing
                                      it from a dedicated kernel thread.

                   CRYPTO_F_DONE      Operation completed.

                   CRYPTO_F_CBIFSYNC  Do callback immediately if operation is
                                      synchronous.

     crp_buf       Points to the input buffer.  On return (when the callback
                   is invoked), it contains the result of the request.  The
                   input buffer may be an mbuf chain or a contiguous buffer,
                   depending on crp_flags.

     crp_opaque    This is passed through the crypto framework untouched and
                   is intended for the invoking application’s use.

     crp_desc      This is a linked list of descriptors.  Each descriptor
                   provides information about what type of cryptographic
                   operation should be done on the input buffer.  The various
                   fields are:

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

                   crd_key     When the CRD_F_KEY_EXPLICIT flag is given, the
                               crd_key points to a buffer with encryption or
                               authentication key.

                   crd_alg     An algorithm to use.  Must be the same as the
                               one given at newsession time.

                   crd_klen    The crd_key key length.

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

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

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

                   crd_flags   The following flags are defined:

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

                               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 algorithm.  Some
                                    applications that do special “IV cooking”,
                                    such as the half-IV mode in ipsec(4), can
                                    use this flag to indicate that the IV
                                    should not be written on the packet.  This
                                    flag is typically used in conjunction with
                                    the CRD_F_IV_EXPLICIT flag.

                               CRD_F_IV_EXPLICIT
                                    For encryption algorithms, this bit is set
                                    when the IV is explicitly provided by the
                                    consumer in the crd_iv field.  Otherwise,
                                    for encryption operations the IV is
                                    provided for by the driver used to perform
                                    the operation, whereas for decryption
                                    operations it is pointed to by the
                                    crd_inject field.  This flag is typically
                                    used when the IV is calculated “on the
                                    fly” by the consumer, and does not precede
                                    the data (some ipsec(4) configurations,
                                    and the encrypted swap are two such
                                    examples).

                               CRD_F_KEY_EXPLICIT
                                    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.

                               CRD_F_COMP
                                    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.

DRIVER-SIDE API

     The crypto_get_driverid(), crypto_register(), crypto_kregister(),
     crypto_unregister(), crypto_unblock(), and crypto_done() routines are
     used by drivers that provide support for cryptographic primitives to
     register and unregister with the kernel crypto services framework.
     Drivers must first use the crypto_get_driverid() function to acquire a
     driver identifier, specifying the cc_flags as an argument (normally 0,
     but software-only drivers should specify CRYPTOCAP_F_SOFTWARE).  For each
     algorithm the driver supports, it must then call crypto_register().  The
     first two arguments are the driver and algorithm identifiers.  The next
     two arguments specify the largest possible operator length (in bits,
     important for public key operations) and flags for this algorithm.  The
     last four arguments must be provided in the first call to
     crypto_register() and are ignored in all subsequent calls.  They are
     pointers to three driver-provided functions that the framework may call
     to establish new cryptographic context with the driver, free already
     established context, and ask for a request to be processed (encrypt,
     decrypt, etc.); and an opaque parameter to pass when calling each of
     these routines.  crypto_unregister() is called by drivers that wish to
     withdraw support for an algorithm.  The two arguments are the driver and
     algorithm identifiers, respectively.  Typically, drivers for PCMCIA
     crypto cards that are being ejected will invoke this routine for all
     algorithms supported by the card.  crypto_unregister_all() will
     unregister all algorithms registered by a driver and the driver will be
     disabled (no new sessions will be allocated on that driver, and any
     existing sessions will be migrated to other drivers).  The same will be
     done if all algorithms associated with a driver are unregistered one by
     one.

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

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

     On invocation, the first argument to all routines is an opaque data value
     supplied when the algorithm is registered with crypto_register().  The
     second argument to newsession() contains the driver identifier obtained
     via crypto_get_driverid().  On successful return, it should contain a
     driver-specific session identifier.  The third argument is identical to
     that of crypto_newsession().

     The freesession() routine takes as arguments the opaque data value and
     the SID (which is the concatenation of the driver identifier and the
     driver-specific session identifier).  It should clear any context
     associated with the session (clear hardware registers, memory, etc.).

     The process() routine is invoked with a request to perform crypto
     processing.  This routine must not block, but should queue the request
     and return immediately.  Upon processing the request, the callback
     routine should be invoked.  In case of an unrecoverable error, the error
     indication must be placed in the crp_etype field of the cryptop
     structure.  When the request is completed, or an error is detected, the
     process() routine should invoke crypto_done().  Session migration may be
     performed, as mentioned previously.

     In case of a temporary resource exhaustion, the process() routine may
     return ERESTART in which case the crypto services will requeue the
     request, mark the driver as “blocked”, and stop submitting requests for
     processing.  The driver is then responsible for notifying the crypto
     services when it is again able to process requests through the
     crypto_unblock() routine.  This simple flow control mechanism should only
     be used for short-lived resource exhaustion as it causes operations to be
     queued in the crypto layer.  Doing so is preferable to returning an error
     in such cases as it can cause network protocols to degrade performance by
     treating the failure much like a lost packet.

     The kprocess() routine is invoked with a request to perform crypto key
     processing.  This routine must not block, but should queue the request
     and return immediately.  Upon processing the request, the callback
     routine should be invoked.  In case of an unrecoverable error, the error
     indication must be placed in the krp_status field of the cryptkop
     structure.  When the request is completed, or an error is detected, the
     kprocess() routine should invoked crypto_kdone().

RETURN VALUES

     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.

FILES

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

SEE ALSO

     ipsec(4), malloc(9), sleep(9)

HISTORY

     The cryptographic framework first appeared in OpenBSD 2.7 and was written
     by Angelos D. Keromytis 〈angelos@openbsd.org〉.

BUGS

     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
     request.