c034143269
- The linked list of cryptoini structures used in session
initialization is replaced with a new flat structure: struct
crypto_session_params. This session includes a new mode to define
how the other fields should be interpreted. Available modes
include:
- COMPRESS (for compression/decompression)
- CIPHER (for simply encryption/decryption)
- DIGEST (computing and verifying digests)
- AEAD (combined auth and encryption such as AES-GCM and AES-CCM)
- ETA (combined auth and encryption using encrypt-then-authenticate)
Additional modes could be added in the future (e.g. if we wanted to
support TLS MtE for AES-CBC in the kernel we could add a new mode
for that. TLS modes might also affect how AAD is interpreted, etc.)
The flat structure also includes the key lengths and algorithms as
before. However, code doesn't have to walk the linked list and
switch on the algorithm to determine which key is the auth key vs
encryption key. The 'csp_auth_*' fields are always used for auth
keys and settings and 'csp_cipher_*' for cipher. (Compression
algorithms are stored in csp_cipher_alg.)
- Drivers no longer register a list of supported algorithms. This
doesn't quite work when you factor in modes (e.g. a driver might
support both AES-CBC and SHA2-256-HMAC separately but not combined
for ETA). Instead, a new 'crypto_probesession' method has been
added to the kobj interface for symmteric crypto drivers. This
method returns a negative value on success (similar to how
device_probe works) and the crypto framework uses this value to pick
the "best" driver. There are three constants for hardware
(e.g. ccr), accelerated software (e.g. aesni), and plain software
(cryptosoft) that give preference in that order. One effect of this
is that if you request only hardware when creating a new session,
you will no longer get a session using accelerated software.
Another effect is that the default setting to disallow software
crypto via /dev/crypto now disables accelerated software.
Once a driver is chosen, 'crypto_newsession' is invoked as before.
- Crypto operations are now solely described by the flat 'cryptop'
structure. The linked list of descriptors has been removed.
A separate enum has been added to describe the type of data buffer
in use instead of using CRYPTO_F_* flags to make it easier to add
more types in the future if needed (e.g. wired userspace buffers for
zero-copy). It will also make it easier to re-introduce separate
input and output buffers (in-kernel TLS would benefit from this).
Try to make the flags related to IV handling less insane:
- CRYPTO_F_IV_SEPARATE means that the IV is stored in the 'crp_iv'
member of the operation structure. If this flag is not set, the
IV is stored in the data buffer at the 'crp_iv_start' offset.
- CRYPTO_F_IV_GENERATE means that a random IV should be generated
and stored into the data buffer. This cannot be used with
CRYPTO_F_IV_SEPARATE.
If a consumer wants to deal with explicit vs implicit IVs, etc. it
can always generate the IV however it needs and store partial IVs in
the buffer and the full IV/nonce in crp_iv and set
CRYPTO_F_IV_SEPARATE.
The layout of the buffer is now described via fields in cryptop.
crp_aad_start and crp_aad_length define the boundaries of any AAD.
Previously with GCM and CCM you defined an auth crd with this range,
but for ETA your auth crd had to span both the AAD and plaintext
(and they had to be adjacent).
crp_payload_start and crp_payload_length define the boundaries of
the plaintext/ciphertext. Modes that only do a single operation
(COMPRESS, CIPHER, DIGEST) should only use this region and leave the
AAD region empty.
If a digest is present (or should be generated), it's starting
location is marked by crp_digest_start.
Instead of using the CRD_F_ENCRYPT flag to determine the direction
of the operation, cryptop now includes an 'op' field defining the
operation to perform. For digests I've added a new VERIFY digest
mode which assumes a digest is present in the input and fails the
request with EBADMSG if it doesn't match the internally-computed
digest. GCM and CCM already assumed this, and the new AEAD mode
requires this for decryption. The new ETA mode now also requires
this for decryption, so IPsec and GELI no longer do their own
authentication verification. Simple DIGEST operations can also do
this, though there are no in-tree consumers.
To eventually support some refcounting to close races, the session
cookie is now passed to crypto_getop() and clients should no longer
set crp_sesssion directly.
- Assymteric crypto operation structures should be allocated via
crypto_getkreq() and freed via crypto_freekreq(). This permits the
crypto layer to track open asym requests and close races with a
driver trying to unregister while asym requests are in flight.
- crypto_copyback, crypto_copydata, crypto_apply, and
crypto_contiguous_subsegment now accept the 'crp' object as the
first parameter instead of individual members. This makes it easier
to deal with different buffer types in the future as well as
separate input and output buffers. It's also simpler for driver
writers to use.
- bus_dmamap_load_crp() loads a DMA mapping for a crypto buffer.
This understands the various types of buffers so that drivers that
use DMA do not have to be aware of different buffer types.
- Helper routines now exist to build an auth context for HMAC IPAD
and OPAD. This reduces some duplicated work among drivers.
- Key buffers are now treated as const throughout the framework and in
device drivers. However, session key buffers provided when a session
is created are expected to remain alive for the duration of the
session.
- GCM and CCM sessions now only specify a cipher algorithm and a cipher
key. The redundant auth information is not needed or used.
- For cryptosoft, split up the code a bit such that the 'process'
callback now invokes a function pointer in the session. This
function pointer is set based on the mode (in effect) though it
simplifies a few edge cases that would otherwise be in the switch in
'process'.
It does split up GCM vs CCM which I think is more readable even if there
is some duplication.
- I changed /dev/crypto to support GMAC requests using CRYPTO_AES_NIST_GMAC
as an auth algorithm and updated cryptocheck to work with it.
- Combined cipher and auth sessions via /dev/crypto now always use ETA
mode. The COP_F_CIPHER_FIRST flag is now a no-op that is ignored.
This was actually documented as being true in crypto(4) before, but
the code had not implemented this before I added the CIPHER_FIRST
flag.
- I have not yet updated /dev/crypto to be aware of explicit modes for
sessions. I will probably do that at some point in the future as well
as teach it about IV/nonce and tag lengths for AEAD so we can support
all of the NIST KAT tests for GCM and CCM.
- I've split up the exising crypto.9 manpage into several pages
of which many are written from scratch.
- I have converted all drivers and consumers in the tree and verified
that they compile, but I have not tested all of them. I have tested
the following drivers:
- cryptosoft
- aesni (AES only)
- blake2
- ccr
and the following consumers:
- cryptodev
- IPsec
- ktls_ocf
- GELI (lightly)
I have not tested the following:
- ccp
- aesni with sha
- hifn
- kgssapi_krb5
- ubsec
- padlock
- safe
- armv8_crypto (aarch64)
- glxsb (i386)
- sec (ppc)
- cesa (armv7)
- cryptocteon (mips64)
- nlmsec (mips64)
Discussed with: cem
Relnotes: yes
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D23677
420 lines
14 KiB
Groff
420 lines
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Groff
.\" Copyright (c) 2020, Chelsio Inc
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright notice,
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.\" this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" 3. Neither the name of the Chelsio Inc nor the names of its
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.\" contributors may be used to endorse or promote products derived from
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.\" this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" * Other names and brands may be claimed as the property of others.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 27, 2020
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.Dt CRYPTO_REQUEST 9
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.Os
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.Sh NAME
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.Nm crypto_request
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.Nd symmetric cryptographic operations
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.Sh SYNOPSIS
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.In opencrypto/cryptodev.h
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.Ft int
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.Fn crypto_dispatch "struct cryptop *crp"
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.Ft void
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.Fn crypto_freereq "struct cryptop *crp"
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.Ft "struct cryptop *"
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.Fn crypto_getreq "crypto_session_t cses" "int how"
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.Sh DESCRIPTION
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Each symmetric cryptographic operation in the kernel is described by
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an instance of
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.Vt struct cryptop
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and is associated with an active session.
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.Pp
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New requests are allocated by
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.Fn crypto_getreq .
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.Fa cses
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is a reference to an active session.
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.Fa how
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is passed to
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.Xr malloc 9
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and should be set to either
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.Dv M_NOWAIT
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or
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.Dv M_WAITOK .
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The caller should then set fields in the returned structure to describe
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request-specific parameters.
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Unused fields should be left as-is.
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.Pp
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.Fn crypto_dispatch
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passes a crypto request to the driver attached to the request's session.
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If there are errors in the request's fields, this function may return
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an error to the caller.
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If errors are encountered while servicing the request, they will instead
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be reported to the request's callback function
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.Pq Fa crp_callback
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via
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.Fa crp_etype .
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.Pp
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Note that a request's callback function may be invoked before
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.Fn crypto_dispatch
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returns.
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.Pp
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Once a request has signaled completion by invoking its callback function,
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it should be feed via
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.Fn crypto_freereq .
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.Pp
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Cryptographic operations include several fields to describe the request.
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.Ss Buffer Types
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Requests are associated with a single data buffer that is modified in place.
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The type of the data buffer and the buffer itself are described by the
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following fields:
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.Bl -tag -width crp_buf_type
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.It Fa crp_buf_type
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|
The type of the data buffer.
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The following types are supported:
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.Bl -tag -width CRYPTO_BUF_CONTIG
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.It Dv CRYPTO_BUF_CONTIG
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|
An array of bytes mapped into the kernel's address space.
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.It Dv CRYPTO_BUF_UIO
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|
A scatter/gather list of kernel buffers as described in
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.Xr uio 9 .
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.It Dv CRYPTO_BUF_MBUF
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|
A network memory buffer as described in
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.Xr mbuf 9 .
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.El
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.It Fa crp_buf
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A pointer to the start of a
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.Dv CRYPTO_BUF_CONTIG
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data buffer.
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.It Fa crp_ilen
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The length of a
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.Dv CRYPTO_BUF_CONTIG
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data buffer
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.It Fa crp_mbuf
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A pointer to a
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.Vt struct mbuf
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for
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.Dv CRYPTO_BUF_MBUF .
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.It Fa crp_uio
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A pointer to a
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.Vt struct uio
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for
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.Dv CRYPTO_BUF_UIO .
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.It Fa crp_olen
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Used with compression and decompression requests to describe the updated
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length of the payload region in the data buffer.
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.Pp
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If a compression request increases the size of the payload,
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then the data buffer is unmodified, the request completes successfully,
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and
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.Fa crp_olen
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is set to the size the compressed data would have used.
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Callers can compare this to the payload region length to determine if
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the compressed data was discarded.
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.El
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.Ss Request Regions
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Each request describes one or more regions in the data buffer using.
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Each region is described by an offset relative to the start of the
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data buffer and a length.
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The length of some regions is the same for all requests belonging to
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a session.
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Those lengths are set in the session parameters of the associated
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session.
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All requests must define a payload region.
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Other regions are only required for specific session modes.
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The following regions are defined:
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.Bl -column "Payload" "crp_payload_start" "crp_payload_length"
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.It Sy Region Ta Sy Start Ta Sy Length Ta Sy Description
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.It AAD Ta Fa crp_aad_start Ta Fa crp_aad_length Ta
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Additional Authenticated Data
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.It IV Ta Fa crp_iv_start Ta Fa csp_ivlen Ta
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Embedded IV or nonce
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.It Payload Ta Fa crp_payload_start Ta Fa crp_payload_length Ta
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Data to encrypt, decrypt, compress, or decompress
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.It Digest Ta Fa crp_digest_start Ta Fa csp_auth_mlen Ta
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Authentication digest, hash, or tag
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.El
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.Pp
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Requests are permitted to operate on only a subset of the data buffer.
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For example,
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requests from IPsec operate on network packets that include headers not
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used as either additional authentication data (AAD) or payload data.
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.Ss Request Operations
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All requests must specify the type of operation to perform in
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.Fa crp_op .
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Available operations depend on the session's mode.
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.Pp
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Compression requests support the following operations:
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.Bl -tag -width CRYPTO_OP_DECOMPRESS
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.It Dv CRYPTO_OP_COMPRESS
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Compress the data in the payload region of the data buffer.
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.It Dv CRYPTO_OP_DECOMPRESS
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Decompress the data in the payload region of the data buffer.
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.El
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.Pp
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Cipher requests support the following operations:
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.Bl -tag -width CRYPTO_OP_DECRYPT
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.It Dv CRYPTO_OP_ENCRYPT
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Encrypt the data in the payload region of the data buffer.
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.It Dv CRYPTO_OP_DECRYPT
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Decrypt the data in the payload region of the data buffer.
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.El
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.Pp
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Digest requests support the following operations:
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.Bl -tag -width CRYPTO_OP_COMPUTE_DIGEST
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.It Dv CRYPTO_OP_COMPUTE_DIGEST
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Calculate a digest over the payload region of the data buffer
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and store the result in the digest region.
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.It Dv CRYPTO_OP_VERIFY_DIGEST
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Calculate a digest over the payload region of the data buffer.
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Compare the calculated digest to the existing digest from the digest region.
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If the digests match,
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complete the request successfully.
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If the digests do not match,
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fail the request with
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.Er EBADMSG .
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.El
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.Pp
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AEAD and Encrypt-then-Authenticate requests support the following
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operations:
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.Bl -tag -width CRYPTO_OP
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.It Dv CRYPTO_OP_ENCRYPT | Dv CRYPTO_OP_COMPUTE_DIGEST
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Encrypt the data in the payload region of the data buffer.
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Calculate a digest over the AAD and payload regions and store the
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result in the data buffer.
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.It Dv CRYPTO_OP_DECRYPT | Dv CRYPTO_OP_VERIFY_DIGEST
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Calculate a digest over the AAD and payload regions of the data buffer.
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Compare the calculated digest to the existing digest from the digest region.
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If the digests match,
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decrypt the payload region.
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If the digests do not match,
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fail the request with
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.Er EBADMSG .
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.El
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.Ss Request IV and/or Nonce
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Some cryptographic operations require an IV or nonce as an input.
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An IV may be stored either in the IV region of the data buffer or in
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.Fa crp_iv .
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By default,
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the IV is assumed to be stored in the IV region.
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If the IV is stored in
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.Fa crp_iv ,
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.Dv CRYPTO_F_IV_SEPARATE
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should be set in
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.Fa crp_flags
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and
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.Fa crp_digest_start
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should be left as zero.
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.Pp
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An encryption request using an IV stored in the IV region may set
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.Dv CRYPTO_F_IV_GENERATE
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in
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.Fa crp_flags
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to request that the driver generate a random IV.
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Note that
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.Dv CRYPTO_F_IV_GENERATE
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cannot be used with decryption operations or in combination with
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.Dv CRYPTO_F_IV_SEPARATE .
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.Pp
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Requests that store part, but not all, of the IV in the data buffer should
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store the partial IV in the data buffer and pass the full IV separately in
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.Fa crp_iv .
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.Ss Request and Callback Scheduling
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The crypto framework provides multiple methods of scheduling the dispatch
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of requests to drivers along with the processing of driver callbacks.
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Requests use flags in
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.Fa crp_flags
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to select the desired scheduling methods.
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.Pp
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.Fn crypto_dispatch
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can pass the request to the session's driver via three different methods:
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.Bl -enum
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.It
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The request is queued to a taskqueue backed by a pool of worker threads.
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By default the pool is sized to provide one thread for each CPU.
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Worker threads dequeue requests and pass them to the driver
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asynchronously.
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.It
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The request is passed to the driver synchronously in the context of the
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thread invoking
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.Fn crypto_dispatch .
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.It
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The request is queued to a queue of pending requests.
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A single worker thread dequeues requests and passes them to the driver
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asynchronously.
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.El
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.Pp
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To select the first method (taskqueue backed by multiple threads),
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requests should set
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.Dv CRYPTO_F_ASYNC .
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To always use the third method (queue to single worker thread),
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requests should set
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.Dv CRYPTO_F_BATCH .
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If both flags are set,
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.Dv CRYPTO_F_ASYNC
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takes precedence.
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If neither flag is set,
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.Fn crypto_dispatch
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will first attempt the second method (invoke driver synchronously).
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If the driver is blocked,
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the request will be queued using the third method.
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One caveat is that the first method is only used for requests using software
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drivers which use host CPUs to process requests.
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Requests whose session is associated with a hardware driver will ignore
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.Dv CRYPTO_F_ASYNC
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and only use
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.Dv CRYPTO_F_BATCH
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to determine how requests should be scheduled.
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.Pp
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In addition to bypassing synchronous dispatch in
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.Fn crypto_dispatch ,
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.Dv CRYPTO_F_BATCH
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requests additional changes aimed at optimizing batches of requests to
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the same driver.
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When the worker thread processes a request with
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.Dv CRYPTO_F_BATCH ,
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it will search the pending request queue for any other requests for the same
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driver,
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including requests from different sessions.
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If any other requests are present,
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.Dv CRYPTO_HINT_MORE
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is passed to the driver's process method.
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Drivers may use this to batch completion interrupts.
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.Pp
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Callback function scheduling is simpler than request scheduling.
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Callbacks can either be invoked synchronously from
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.Fn crypto_done ,
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or they can be queued to a pool of worker threads.
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This pool of worker threads is also sized to provide one worker thread
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for each CPU by default.
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Note that a callback function invoked synchronously from
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.Fn crypto_done
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must follow the same restrictions placed on threaded interrupt handlers.
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.Pp
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By default,
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callbacks are invoked asynchronously by a worker thread.
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If
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.Dv CRYPTO_F_CBIMM
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is set,
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the callback is always invoked synchronously from
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.Fn crypto_done .
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If
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.Dv CRYPTO_F_CBIFSYNC
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is set,
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the callback is invoked synchronously if the request was processed by a
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software driver or asynchronously if the request was processed by a
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hardware driver.
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.Pp
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If a request was scheduled to the taskqueue via
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.Dv CRYPTO_F_ASYNC ,
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callbacks are always invoked asynchronously ignoring
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.Dv CRYPTO_F_CBIMM
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and
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.Dv CRYPTO_F_CBIFSYNC .
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In this case,
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.Dv CRYPTO_F_ASYNC_KEEPORDER
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may be set to ensure that callbacks for requests on a given session are
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invoked in the same order that requests were queued to the session via
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.Fn crypto_dispatch .
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This flag is used by IPsec to ensure that decrypted network packets are
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passed up the network stack in roughly the same order they were received.
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.Pp
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.Ss Other Request Fields
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In addition to the fields and flags enumerated above,
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.Vt struct cryptop
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includes the following:
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.Bl -tag -width crp_payload_length
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.It Fa crp_session
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A reference to the active session.
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This is set when the request is created by
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.Fn crypto_getreq
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and should not be modified.
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Drivers can use this to fetch driver-specific session state or
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session parameters.
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.It Fa crp_etype
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Error status.
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Either zero on success, or an error if a request fails.
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Set by drivers prior to completing a request via
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.Fn crypto_done .
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.It Fa crp_flags
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A bitmask of flags.
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The following flags are available in addition to flags discussed previously:
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.Bl -tag -width CRYPTO_F_DONE
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.It Dv CRYPTO_F_DONE
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Set by
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.Fa crypto_done
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before calling
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.Fa crp_callback .
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This flag is not very useful and will likely be removed in the future.
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It can only be safely checked from the callback routine at which point
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it is always set.
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.El
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.It Fa crp_cipher_key
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Pointer to a request-specific encryption key.
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If this value is not set,
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the request uses the session encryption key.
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.It Fa crp_auth_key
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Pointer to a request-specific authentication key.
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If this value is not set,
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the request uses the session authentication key.
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.It Fa crp_opaque
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An opaque pointer.
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This pointer permits users of the cryptographic framework to store
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information about a request to be used in the callback.
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.It Fa crp_callback
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Callback function.
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This must point to a callback function of type
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.Vt void (*)(struct cryptop *) .
|
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The callback function should inspect
|
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.Fa crp_etype
|
|
to determine the status of the completed operation.
|
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It should also arrange for the request to be freed via
|
|
.Fn crypto_freereq .
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.El
|
|
.Sh RETURN VALUES
|
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.Fn crypto_dispatch
|
|
returns an error if the request contained invalid fields,
|
|
or zero if the request was valid.
|
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.Fn crypto_getreq
|
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returns a pointer to a new request structure on success,
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or
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.Dv NULL
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on failure.
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.Dv NULL
|
|
can only be returned if
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.Dv M_NOWAIT
|
|
was passed in
|
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.Fa how .
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.Sh SEE ALSO
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.Xr ipsec 4 ,
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.Xr crypto 7 ,
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.Xr crypto 9 ,
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.Xr crypto_session 9 ,
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.Xr mbuf 9
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.Xr uio 9
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.Sh BUGS
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|
Not all drivers properly handle mixing session and per-request keys
|
|
within a single session.
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Consumers should either use a single key for a session specified in
|
|
the session parameters or always use per-request keys.
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