ddcef18974
- 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
179 lines
5.4 KiB
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179 lines
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.\" 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_ASYM 9
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.Os
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.Sh NAME
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.Nm crypto_asym
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.Nd asymmetric 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_kdispatch "struct cryptkop *krp"
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.Ft void
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.Fn crypto_kdone "struct cryptkop *krp"
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.Ft int
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.Fn crypto_kregister "uint32_t driverid" "int kalg" "uint32_t flags"
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.Ft int
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.Fn CRYPTODEV_KPROCESS "device_t dev" "struct cryptop *krp" "int flags"
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.Sh DESCRIPTION
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The in-kernel cryptographic kernel framework supports asymmetric
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requests (keying requests) in addition to symmetric operations.
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There are currently no in-kernel users of these requests,
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but applications can make requests of hardware drivers via the
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.Pa /dev/crypto
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device .
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.Pp
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Some APIs are shared with the framework's symmetric request support.
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This manual describes the APIs and data structures unique to
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asymmetric requests.
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.Pp
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.Ss Request Objects
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A request is described by a
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.Vt struct cryptkop
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containing the following fields:
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.Bl -tag -width "krp_callback"
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.It Fa krp_op
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Operation to perform.
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Available operations include
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.Dv CRK_MOD_EXP ,
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.Dv CRK_MOD_EXP_CRT ,
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.Dv CRK_DSA_SIGN ,
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.Dv CRK_DSA_VERIFY ,
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and
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.Dv CRK_DH_COMPUTE_KEY .
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.It Fa krp_status
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Error status.
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Either zero on success,
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or an error if an operation fails.
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Set by drivers prior to completing a request via
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.Fn crypto_kdone .
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.It Fa krp_iparams
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Count of input parameters.
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.It Fa krp_oparams
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Count of output parameters.
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.It Fa krp_crid
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Requested device.
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.It Fa krp_hid
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Device used to complete the request.
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.It Fa krp_param
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Array of parameters.
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The array contains the input parameters first followed by the output
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parameters.
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Each parameter is stored as a bignum.
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Each bignum is described by a
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.Vt struct crparam
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containing the following fields:
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.Bl -tag -width "crp_nbits"
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.It Fa crp_p
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Pointer to array of packed bytes.
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.It Fa crp_nbits
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Size of bignum in bits.
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.El
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.It Fa krp_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 cryptkop *) .
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The callback function should inspect
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.Fa krp_status
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to determine the status of the completed operation.
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.El
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.Pp
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New requests should be initialized to zero before setting fields to
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appropriate values.
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Once the request has been populated,
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it should be passed to
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.Fn crypto_kdispatch .
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.Pp
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.Fn crypto_kdispatch
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will choose a device driver to perform the operation described by
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.Fa krp
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and invoke that driver's
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.Fn CRYPTO_KPROCESS
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method.
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.Ss Driver API
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Drivers register support for asymmetric operations by calling
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.Fn crypto_kregister
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for each supported algorithm.
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.Fa driverid
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should be the value returned by an earlier call to
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.Fn crypto_get_driverid .
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.Fa kalg
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should list one of the operations that can be set in
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.Fa krp_op .
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.Fa flags
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is a bitmask of zero or more of the following values:
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.Bl -tag -width "CRYPTO_ALG_FLAG_RNG_ENABLE"
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.It Dv CRYPTO_ALG_FLAG_RNG_ENABLE
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Device has a hardware RNG for DH/DSA.
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.It Dv CRYPTO_ALG_FLAG_DSA_SHA
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Device can compute a SHA digest of a message.
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.El
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.Pp
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Drivers unregister with the framework via
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.Fn crypto_unregister_all .
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.Pp
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Similar to
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.Fn CRYPTO_PROCESS ,
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.Fn CRYPTO_KPROCESS
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should complete the request or schedule it for asynchronous
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completion.
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If this method is not able to complete a request due to insufficient
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resources,
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it can defer the request (and future asymmetric requests) by returning
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.Dv ERESTART .
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Once resources are available,
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the driver should invoke
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.Fn crypto_unblock
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with
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.Dv CRYPTO_ASYMQ
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to resume processing of asymmetric requests.
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.Pp
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Once a request is completed,
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the driver should set
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.Fa krp_status
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and then call
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.Fn crypto_kdone .
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.Sh RETURN VALUES
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.Fn crypto_kdispatch ,
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.Fn crypto_kregister ,
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and
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.Fn CRYPTODEV_KPROCESS
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return zero on success or an error on failure.
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.Sh SEE ALSO
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.Xr crypto 7 ,
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.Xr crypto 9 ,
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.Xr crypto_driver 9 ,
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.Xr crypto_request 9 ,
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.Xr crypto_session 9
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