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.Dd August 12, 2020 .Dt CRYPTO_REQUEST 9 .Os .Sh NAME .Nm crypto_request .Nd symmetric cryptographic operations .Sh SYNOPSIS n opencrypto/cryptodev.h .Ft int .Fn crypto_dispatch "struct cryptop *crp" .Ft void .Fn crypto_destroyreq "struct cryptop *crp" .Ft void .Fn crypto_freereq "struct cryptop *crp" .Ft "struct cryptop *" .Fn crypto_getreq "crypto_session_t cses" "int how" .Ft void .Fn crypto_initreq "crypto_session_t cses" "int how" .Ft void .Fn crypto_use_buf "struct cryptop *crp" "void *buf" "int len" .Ft void .Fn crypto_use_mbuf "struct cryptop *crp" "struct mbuf *m" .Ft void .Fn crypto_use_uio "struct cryptop *crp" "struct uio *uio" .Ft void .Fn crypto_use_vmpage "struct cryptop *crp" "vm_page_t *pages" "int len" "int offset" .Ft void .Fn crypto_use_output_buf "struct cryptop *crp" "void *buf" "int len" .Ft void .Fn crypto_use_output_mbuf "struct cryptop *crp" "struct mbuf *m" .Ft void .Fn crypto_use_output_uio "struct cryptop *crp" "struct uio *uio" .Ft void .Fn crypto_use_output_vmpage "struct cryptop *crp" "vm_page_t *pages" "int len" "int offset" .Sh DESCRIPTION Each symmetric cryptographic operation in the kernel is described by an instance of .Vt struct cryptop and is associated with an active session.
p Requests can either be allocated dynamically or use caller-supplied storage. Dynamically allocated requests should be allocated by .Fn crypto_getreq and freed by .Fn crypto_freereq once the request has completed. Requests using caller-supplied storage should be initialized by .Fn crypto_initreq at the start of each operation and destroyed by .Fn crypto_destroyreq once the request has completed.
p For both .Fn crypto_getreq and .Fn crypto_initreq , .Fa cses is a reference to an active session. For .Fn crypto_getreq , .Fa how is passed to .Xr malloc 9 and should be set to either .Dv M_NOWAIT or .Dv M_WAITOK .
p Once a request has been initialized, the caller should set fields in the structure to describe request-specific parameters. Unused fields should be left as-is.
p .Fn crypto_dispatch passes a crypto request to the driver attached to the request's session. If there are errors in the request's fields, this function may return an error to the caller. If errors are encountered while servicing the request, they will instead be reported to the request's callback function
q Fa crp_callback via .Fa crp_etype .
p Note that a request's callback function may be invoked before .Fn crypto_dispatch returns.
p Once a request has signaled completion by invoking its callback function, it should be freed via .Fn crypto_destroyreq or .Fn crypto_freereq .
p Cryptographic operations include several fields to describe the request. .Ss Request Buffers Requests can either specify a single data buffer that is modified in place
o .Fa crp_buf
c or separate input
o .Fa crp_buf
c and output
o .Fa crp_obuf
c buffers. Note that separate input and output buffers are not supported for compression mode requests.
p All requests must have a valid .Fa crp_buf initialized by one of the following functions: l -tag -width "Fn crypto_use_vmpage" t Fn crypto_use_buf Uses an array of .Fa len bytes pointed to by .Fa buf as the data buffer. t Fn crypto_use_mbuf Uses the network memory buffer .Fa m as the data buffer. t Fn crypto_use_uio Uses the scatter/gather list .Fa uio as the data buffer. t Fn crypto_use_vmpage Uses the array of .Vt vm_page_t structures as the data buffer. .El
p One of the following functions should be used to initialize .Fa crp_obuf for requests that use separate input and output buffers: l -tag -width "Fn crypto_use_output_vmpage" t Fn crypto_use_output_buf Uses an array of .Fa len bytes pointed to by .Fa buf as the output buffer. t Fn crypto_use_output_mbuf Uses the network memory buffer .Fa m as the output buffer. t Fn crypto_use_output_uio Uses the scatter/gather list .Fa uio as the output buffer. t Fn crypto_use_output_vmpage Uses the array of .Vt vm_page_t structures as the output buffer. .El .Ss Request Regions Each request describes one or more regions in the data buffers. Each region is described by an offset relative to the start of a data buffer and a length. The length of some regions is the same for all requests belonging to a session. Those lengths are set in the session parameters of the associated session. All requests must define a payload region. Other regions are only required for specific session modes.
p For requests with separate input and output data buffers, the AAD, IV, and payload regions are always defined as regions in the input buffer, and a separate payload output region is defined to hold the output of encryption or decryption in the output buffer. The digest region describes a region in the input data buffer for requests that verify an existing digest. For requests that compute a digest, the digest region describes a region in the output data buffer. Note that the only data written to the output buffer is the encryption or decryption result and any computed digest. AAD and IV regions are not copied from the input buffer into the output buffer but are only used as inputs.
p The following regions are defined: l -column "Payload Output" "Input/Output" t Sy Region Ta Sy Buffer Ta Sy Description t AAD Ta Input Ta Embedded Additional Authenticated Data t IV Ta Input Ta Embedded IV or nonce t Payload Ta Input Ta Data to encrypt, decrypt, compress, or decompress t Payload Output Ta Output Ta Encrypted or decrypted data t Digest Ta Input/Output Ta Authentication digest, hash, or tag .El l -column "Payload Output" ".Fa crp_payload_output_start" t Sy Region Ta Sy Start Ta Sy Length t AAD Ta Fa crp_aad_start Ta Fa crp_aad_length t IV Ta Fa crp_iv_start Ta Fa csp_ivlen t Payload Ta Fa crp_payload_start Ta Fa crp_payload_length t Payload Output Ta Fa crp_payload_output_start Ta Fa crp_payload_length t Digest Ta Fa crp_digest_start Ta Fa csp_auth_mlen .El
p Requests are permitted to operate on only a subset of the data buffer. For example, requests from IPsec operate on network packets that include headers not used as either additional authentication data (AAD) or payload data. .Ss Request Operations All requests must specify the type of operation to perform in .Fa crp_op . Available operations depend on the session's mode.
p Compression requests support the following operations: l -tag -width CRYPTO_OP_DECOMPRESS t Dv CRYPTO_OP_COMPRESS Compress the data in the payload region of the data buffer. t Dv CRYPTO_OP_DECOMPRESS Decompress the data in the payload region of the data buffer. .El
p Cipher requests support the following operations: l -tag -width CRYPTO_OP_DECRYPT t Dv CRYPTO_OP_ENCRYPT Encrypt the data in the payload region of the data buffer. t Dv CRYPTO_OP_DECRYPT Decrypt the data in the payload region of the data buffer. .El
p Digest requests support the following operations: l -tag -width CRYPTO_OP_COMPUTE_DIGEST t Dv CRYPTO_OP_COMPUTE_DIGEST Calculate a digest over the payload region of the data buffer and store the result in the digest region. t Dv CRYPTO_OP_VERIFY_DIGEST Calculate a digest over the payload region of the data buffer. Compare the calculated digest to the existing digest from the digest region. If the digests match, complete the request successfully. If the digests do not match, fail the request with .Er EBADMSG . .El
p AEAD and Encrypt-then-Authenticate requests support the following operations: l -tag -width CRYPTO_OP t Dv CRYPTO_OP_ENCRYPT | Dv CRYPTO_OP_COMPUTE_DIGEST Encrypt the data in the payload region of the data buffer. Calculate a digest over the AAD and payload regions and store the result in the data buffer. t Dv CRYPTO_OP_DECRYPT | Dv CRYPTO_OP_VERIFY_DIGEST Calculate a digest over the AAD and payload regions of the data buffer. Compare the calculated digest to the existing digest from the digest region. If the digests match, decrypt the payload region. If the digests do not match, fail the request with .Er EBADMSG . .El .Ss Request AAD AEAD and Encrypt-then-Authenticate requests may optionally include Additional Authenticated Data. AAD may either be supplied in the AAD region of the input buffer or as a single buffer pointed to by .Fa crp_aad . In either case, .Fa crp_aad_length always indicates the amount of AAD in bytes. .Ss Request ESN IPsec requests may optionally include Extended Sequence Numbers (ESN). ESN may either be supplied in .Fa crp_esn or as part of the AAD pointed to by .Fa crp_aad .
p If the ESN is stored in .Fa crp_esn , .Dv CSP_F_ESN should be set in .Fa csp_flags . This use case is dedicated for encrypt and authenticate mode, since the high-order 32 bits of the sequence number are appended after the Next Header (RFC 4303).
p AEAD modes supply the ESN in a separate AAD buffer (see e.g. RFC 4106, Chapter 5 AAD Construction). .Ss Request IV and/or Nonce Some cryptographic operations require an IV or nonce as an input. An IV may be stored either in the IV region of the data buffer or in .Fa crp_iv . By default, the IV is assumed to be stored in the IV region. If the IV is stored in .Fa crp_iv , .Dv CRYPTO_F_IV_SEPARATE should be set in .Fa crp_flags and .Fa crp_iv_start should be left as zero.
p Requests that store part, but not all, of the IV in the data buffer should store the partial IV in the data buffer and pass the full IV separately in .Fa crp_iv . .Ss Request and Callback Scheduling The crypto framework provides multiple methods of scheduling the dispatch of requests to drivers along with the processing of driver callbacks. Requests use flags in .Fa crp_flags to select the desired scheduling methods.
p .Fn crypto_dispatch can pass the request to the session's driver via three different methods: l -enum t The request is queued to a taskqueue backed by a pool of worker threads. By default the pool is sized to provide one thread for each CPU. Worker threads dequeue requests and pass them to the driver asynchronously. t The request is passed to the driver synchronously in the context of the thread invoking .Fn crypto_dispatch . t The request is queued to a queue of pending requests. A single worker thread dequeues requests and passes them to the driver asynchronously. .El
p To select the first method (taskqueue backed by multiple threads), requests should set .Dv CRYPTO_F_ASYNC . To always use the third method (queue to single worker thread), requests should set .Dv CRYPTO_F_BATCH . If both flags are set, .Dv CRYPTO_F_ASYNC takes precedence. If neither flag is set, .Fn crypto_dispatch will first attempt the second method (invoke driver synchronously). If the driver is blocked, the request will be queued using the third method. One caveat is that the first method is only used for requests using software drivers which use host CPUs to process requests. Requests whose session is associated with a hardware driver will ignore .Dv CRYPTO_F_ASYNC and only use .Dv CRYPTO_F_BATCH to determine how requests should be scheduled.
p In addition to bypassing synchronous dispatch in .Fn crypto_dispatch , .Dv CRYPTO_F_BATCH requests additional changes aimed at optimizing batches of requests to the same driver. When the worker thread processes a request with .Dv CRYPTO_F_BATCH , it will search the pending request queue for any other requests for the same driver, including requests from different sessions. If any other requests are present, .Dv CRYPTO_HINT_MORE is passed to the driver's process method. Drivers may use this to batch completion interrupts.
p Callback function scheduling is simpler than request scheduling. Callbacks can either be invoked synchronously from .Fn crypto_done , or they can be queued to a pool of worker threads. This pool of worker threads is also sized to provide one worker thread for each CPU by default. Note that a callback function invoked synchronously from .Fn crypto_done must follow the same restrictions placed on threaded interrupt handlers.
p By default, callbacks are invoked asynchronously by a worker thread. If .Dv CRYPTO_F_CBIMM is set, the callback is always invoked synchronously from .Fn crypto_done . If .Dv CRYPTO_F_CBIFSYNC is set, the callback is invoked synchronously if the request was processed by a software driver or asynchronously if the request was processed by a hardware driver.
p If a request was scheduled to the taskqueue via .Dv CRYPTO_F_ASYNC , callbacks are always invoked asynchronously ignoring .Dv CRYPTO_F_CBIMM and .Dv CRYPTO_F_CBIFSYNC . In this case, .Dv CRYPTO_F_ASYNC_KEEPORDER may be set to ensure that callbacks for requests on a given session are invoked in the same order that requests were queued to the session via .Fn crypto_dispatch . This flag is used by IPsec to ensure that decrypted network packets are passed up the network stack in roughly the same order they were received.
p .Ss Other Request Fields In addition to the fields and flags enumerated above, .Vt struct cryptop includes the following: l -tag -width crp_payload_length t Fa crp_session A reference to the active session. This is set when the request is created by .Fn crypto_getreq and should not be modified. Drivers can use this to fetch driver-specific session state or session parameters. t Fa crp_etype Error status. Either zero on success, or an error if a request fails. Set by drivers prior to completing a request via .Fn crypto_done . t Fa crp_flags A bitmask of flags. The following flags are available in addition to flags discussed previously: l -tag -width CRYPTO_F_DONE t Dv CRYPTO_F_DONE Set by .Fa crypto_done before calling .Fa crp_callback . This flag is not very useful and will likely be removed in the future. It can only be safely checked from the callback routine at which point it is always set. .El t Fa crp_cipher_key Pointer to a request-specific encryption key. If this value is not set, the request uses the session encryption key. t Fa crp_auth_key Pointer to a request-specific authentication key. If this value is not set, the request uses the session authentication key. t Fa crp_opaque An opaque pointer. This pointer permits users of the cryptographic framework to store information about a request to be used in the callback. t Fa crp_callback Callback function. This must point to a callback function of type .Vt void (*)(struct cryptop *) . The callback function should inspect .Fa crp_etype to determine the status of the completed operation. It should also arrange for the request to be freed via .Fn crypto_freereq . t Fa crp_olen Used with compression and decompression requests to describe the updated length of the payload region in the data buffer.
p If a compression request increases the size of the payload, then the data buffer is unmodified, the request completes successfully, and .Fa crp_olen is set to the size the compressed data would have used. Callers can compare this to the payload region length to determine if the compressed data was discarded. .El .Sh RETURN VALUES .Fn crypto_dispatch returns an error if the request contained invalid fields, or zero if the request was valid. .Fn crypto_getreq returns a pointer to a new request structure on success, or .Dv NULL on failure. .Dv NULL can only be returned if .Dv M_NOWAIT was passed in .Fa how . .Sh SEE ALSO .Xr ipsec 4 , .Xr crypto 7 , .Xr crypto 9 , .Xr crypto_session 9 , .Xr mbuf 9 .Xr uio 9 .Sh BUGS Not all drivers properly handle mixing session and per-request keys within a single session. Consumers should either use a single key for a session specified in the session parameters or always use per-request keys.