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

NAME
     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 -- API for cryptographic services in the
     kernel

SYNOPSIS
     #include <opencrypto/cryptodev.h>

     int32_t
     crypto_get_driverid(u_int32_t);

     int
     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 *);

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

     struct cryptop *
     crypto_getreq(int);

     void
     crypto_freereq(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 *);
     };

DESCRIPTION
     opencrypto 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 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
     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
     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).  No callback mechanism is used for session initialization and
     teardown.

     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 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:

                   CRYPTO_DES_CBC
                   CRYPTO_3DES_CBC
                   CRYPTO_BLF_CBC
                   CRYPTO_CAST_CBC
                   CRYPTO_CAMELLIA_CBC
                   CRYPTO_SKIPJACK_CBC
                   CRYPTO_ARC4
                   CRYPTO_AES_CBC
                   CRYPTO_AES_CTR
                   CRYPTO_AES_GCM_16
                   CRYPTO_AES_GMAC
                   CRYPTO_AES_128_GMAC
                   CRYPTO_AES_192_GMAC
                   CRYPTO_AES_256_GMAC
                   CRYPTO_AES_XCBC_MAC_96
                   CRYPTO_MD5
                   CRYPTO_MD5_HMAC
                   CRYPTO_MD5_HMAC_96
                   CRYPTO_MD5_KPDK
                   CRYPTO_NULL_CBC
                   CRYPTO_NULL_HMAC
                   CRYPTO_SHA1
                   CRYPTO_SHA1_HMAC
                   CRYPTO_SHA1_HMAC_96
                   CRYPTO_SHA1_KPDK
                   CRYPTO_SHA2_256_HMAC
                   CRYPTO_SHA2_384_HMAC
                   CRYPTO_SHA2_512_HMAC
                   CRYPTO_RIPEMD160_HMAC
                   CRYPTO_RIPEMD160_HMAC_96
                   CRYPTO_DEFLATE_COMP
                   CRYPTO_DEFLATE_COMP_NOGROW
                   CRYPTO_GZIP_COMP

     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
                   algorithm, 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
                   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 length of the result, not including
                   crd_skip.  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
                   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
                   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.

     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
                   operation 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 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 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.  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 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
                                                      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_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 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)
                    number of such parameters.

     krp_oparams    Number of 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 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-accelerated operations
                                   (handling the latter in software).

                              > 0  Allow user requests only for operations
                                   which are hardware-accelerated.

DRIVER-SIDE API
     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.
     Drivers must first use the crypto_get_driverid() function to acquire a
     driver identifier, specifying the 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 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-
     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 arguments are the driver and algorithm
     identifiers, respectively.  algorithms supported by the card.  If all
     algorithms associated with a driver are unregistered, the driver will be
     disabled (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
     returning, 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
     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 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
     routine 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().

RETURN VALUES
     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_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

     sys/crypto               crypto algorithm implementations

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

     Angelos D. Keromytis, Jason L. Wright, and Theo de Raadt, The Design of
     the OpenBSD Cryptographic Framework, Usenix, 2003, June 2003.

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

     Sam Leffler ported the crypto framework to FreeBSD and made performance
     improvements.

     Jonathan Stone <jonathan@NetBSD.org> ported the cryptoframe from FreeBSD
     to NetBSD.  opencrypto first appeared in NetBSD 2.0.

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
     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.

     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
     support).

NetBSD 7.1.2                   December 30, 2013                  NetBSD 7.1.2