Manual Pages  — CRYPTO

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() returns the driver id of the device whose name matches match. match can either be the exact name of a device including the unit or the driver name without a unit. In the latter case, the id of the first device with the matching driver name is returned. If no matching device is found, the value -1 is returned.

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 cri argument points to a cryptoini structure containing all the necessary information for the driver to establish the session. The crid argument is either a specific driver id or a bitmask of flags. The flags are CRYPTOCAP_F_HARDWARE, to select hardware devices, or CRYPTOCAP_F_SOFTWARE, to select software devices. If both are specified, hardware devices are preferred over software devices. On success, the opaque session handle of the new session will be stored in *cses. The cryptoini structure pointed to by cri contains these fields:

cri_alg
	An algorithm identifier. Currently supported algorithms are:

CRYPTO_AES_128_NIST_GMAC CRYPTO_AES_192_NIST_GMAC CRYPTO_AES_256_NIST_GMAC CRYPTO_AES_CBC CRYPTO_AES_CCM_16 CRYPTO_AES_CCM_CBC_MAC CRYPTO_AES_ICM CRYPTO_AES_NIST_GCM_16 CRYPTO_AES_NIST_GMAC CRYPTO_AES_XTS CRYPTO_ARC4 CRYPTO_BLAKE2B CRYPTO_BLAKE2S CRYPTO_BLF_CBC CRYPTO_CAMELLIA_CBC CRYPTO_CAST_CBC CRYPTO_CHACHA20 CRYPTO_DEFLATE_COMP CRYPTO_DES_CBC CRYPTO_3DES_CBC CRYPTO_MD5 CRYPTO_MD5_HMAC CRYPTO_MD5_KPDK CRYPTO_NULL_HMAC CRYPTO_NULL_CBC CRYPTO_POLY1305 CRYPTO_RIPEMD160 CRYPTO_RIPEMD160_HMAC CRYPTO_SHA1 CRYPTO_SHA1_HMAC CRYPTO_SHA1_KPDK CRYPTO_SHA2_224 CRYPTO_SHA2_224_HMAC CRYPTO_SHA2_256 CRYPTO_SHA2_256_HMAC CRYPTO_SHA2_384 CRYPTO_SHA2_384_HMAC CRYPTO_SHA2_512 CRYPTO_SHA2_512_HMAC CRYPTO_SKIPJACK_CBC

cri_klen
	For variable-size key algorithms, the length of the key in bits.
cri_mlen
	If non-zero, truncate the calculated hash to this many bytes.
cri_key
	The key to be used.
cri_iv
	An explicit initialization vector 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
	Pointer to another cryptoini structure. This is used to establish dual-algorithm sessions, such as combining a cipher with a MAC.

The cryptoini structure and its contents will not be modified or referenced by the framework or any cryptographic drivers. The memory associated with cri can be released once crypto_newsession() returns.

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
	The session handle.
crp_ilen
	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
	Callback routine invoked when a request is completed via crypto_done(). The callback routine should inspect the crp_etype to determine if the request was successfully completed.
crp_etype
	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). This field is only valid in the context of the callback routine specified by 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
	A bitmask of flags associated with this request. Currently defined flags are:

CRYPTO_F_IMBUF	The buffer is an mbuf chain pointed to by crp_mbuf.
CRYPTO_F_IOV	The buffer is a uio structure pointed to by crp_uio.
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.
CRYPTO_F_ASYNC_KEEPORDER
	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
	Data buffer unless CRYPTO_F_IMBUF or CRYPTO_F_IOV is set in crp_flags. The length in bytes is set in crp_ilen.
crp_mbuf
	Data buffer mbuf chain when CRYPTO_F_IMBUF is set in crp_flags.
crp_uio
	struct uio data buffer when CRYPTO_F_IOV is set in crp_flags.
crp_opaque
	Cookie passed through the crypto framework untouched. It is intended for the invoking application's use.
crp_desc
	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 IV.
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 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, 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.
CRD_F_IV_EXPLICIT
	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.
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. As calculating the key schedule may take a while, it is recommended that often used keys are given their own session.
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 num cryptodesc structures.

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 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.