xref: /freebsd/share/man/man9/crypto_driver.9 (revision 29fe41ddd714bae92a09fd4098fad614945bedf5)

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.Dd April 20, 2020
.Dt CRYPTO_DRIVER 9
.Os
.Sh NAME
.Nm crypto_driver
.Nd interface for symmetric cryptographic drivers
.Sh SYNOPSIS
.In opencrypto/cryptodev.h
.Ft int
.Fo crypto_apply
.Fa "struct cryptop *crp"
.Fa "int off"
.Fa "int len"
.Fa "int (*f)(void *, void *, u_int)"
.Fa "void *arg"
.Fc
.Ft void *
.Fo crypto_contiguous_subsegment
.Fa "struct cryptop *crp"
.Fa "size_t skip"
.Fa "size_t len"
.Fc
.Ft void
.Fn crypto_copyback "struct cryptop *crp" "int off" "int size" "const void *src"
.Ft void
.Fn crypto_copydata "struct cryptop *crp" "int off" "int size" "void *dst"
.Ft void
.Fn crypto_done "struct cryptop *crp"
.Ft int32_t
.Fn crypto_get_driverid "device_t dev" "size_t session_size" "int flags"
.Ft void *
.Fn crypto_get_driver_session "crypto_session_t crypto_session"
.Ft void
.Fn crypto_read_iv "struct cryptop *crp" "void *iv"
.Ft int
.Fn crypto_unblock "uint32_t driverid" "int what"
.Ft int
.Fn crypto_unregister_all "uint32_t driverid"
.Ft int
.Fn CRYPTODEV_FREESESSION "device_t dev" "crypto_session_t crypto_session"
.Ft int
.Fo CRYPTODEV_NEWSESSION
.Fa "device_t dev"
.Fa "crypto_session_t crypto_session"
.Fa "const struct crypto_session_params *csp"
.Fc
.Ft int
.Fo CRYPTODEV_PROBESESSION
.Fa "device_t dev"
.Fa "const struct crypto_session_params *csp"
.Fc
.Ft int
.Fn CRYPTODEV_PROCESS "device_t dev" "struct cryptop *crp" "int flags"
.Ft void
.Fo hmac_init_ipad
.Fa "struct auth_hash *axf"
.Fa "const char *key"
.Fa "int klen"
.Fa "void *auth_ctx"
.Fc
.Ft void
.Fo hmac_init_opad
.Fa "struct auth_hash *axf"
.Fa "const char *key"
.Fa "int klen"
.Fa "void *auth_ctx"
.Fc
.Sh DESCRIPTION
Symmetric cryptographic drivers process cryptographic requests
submitted to sessions associated with the driver.
.Pp
Cryptographic drivers call
.Fn crypto_get_driverid
to register with the cryptographic framework.
.Fa dev
is the device used to service requests.
The
.Fn CRYPTODEV
methods are defined in the method table for the device driver attached to
.Fa dev .
.Fa session_size
specifies the size of a driver-specific per-session structure allocated by
the cryptographic framework.
.Fa flags
is a bitmask of properties about the driver.
Exactly one of
.Dv CRYPTOCAP_F_SOFTWARE
or
.Dv CRYPTOCAP_F_HARDWARE
must be specified.
.Dv CRYPTOCAP_F_SOFTWARE
should be used for drivers which process requests using host CPUs.
.Dv CRYPTOCAP_F_HARDWARE
should be used for drivers which process requests on separate co-processors.
.Dv CRYPTOCAP_F_SYNC
should be set for drivers which process requests synchronously in
.Fn CRYPTODEV_PROCESS .
.Fn crypto_get_driverid
returns an opaque driver id.
.Pp
.Fn crypto_unregister_all
unregisters a driver from the cryptographic framework.
If there are any pending operations or open sessions,
this function will sleep.
.Fa driverid
is the value returned by an earlier call to
.Fn crypto_get_driverid .
.Pp
When a new session is created by
.Fn crypto_newsession ,
.Fn CRYPTODEV_PROBESESSION
is invoked by the cryptographic framework on each active driver to
determine the best driver to use for the session.
This method should inspect the session parameters in
.Fa csp .
If a driver does not support requests described by
.Fa csp ,
this method should return an error value.
If the driver does support requests described by
.Fa csp ,
it should return a negative value.
The framework prefers drivers with the largest negative value,
similar to
.Xr DEVICE_PROBE 9 .
The following values are defined for non-error return values from this
method:
.Bl -tag -width "CRYPTODEV_PROBE_ACCEL_SOFTWARE"
.It Dv CRYPTODEV_PROBE_HARDWARE
The driver processes requests via a co-processor.
.It Dv CRYPTODEV_PROBE_ACCEL_SOFTWARE
The driver processes requests on the host CPU using optimized instructions
such as AES-NI.
.It Dv CRYPTODEV_PROBE_SOFTWARE
The driver processes requests on the host CPU.
.El
.Pp
This method should not sleep.
.Pp
Once the framework has chosen a driver for a session,
the framework invokes the
.Fn CRYPTODEV_NEWSESSION
method to initialize driver-specific session state.
Prior to calling this method,
the framework allocates a per-session driver-specific data structure.
This structure is initialized with zeroes,
and its size is set by the
.Fa session_size
passed to
.Fn crypto_get_driverid .
This method can retrieve a pointer to this data structure by passing
.Fa crypto_session
to
.Fn crypto_get_driver_session .
Session parameters are described in
.Fa csp .
.Pp
This method should not sleep.
.Pp
.Fn CRYPTODEV_FREESESSION
is invoked to release any driver-specific state when a session is
destroyed.
The per-session driver-specific data structure is explicitly zeroed
and freed by the framework after this method returns.
If a driver requires no additional tear-down steps, it can leave
this method undefined.
.Pp
This method should not sleep.
.Pp
.Fn CRYPTODEV_PROCESS
is invoked for each request submitted to an active session.
This method can either complete a request synchronously or
schedule it to be completed asynchronously,
but it must not sleep.
.Pp
If this method is not able to complete a request due to insufficient
resources such as a full command queue,
it can defer the request by returning
.Dv ERESTART .
The request will be queued by the framework and retried once the
driver releases pending requests via
.Fn crypto_unblock .
Any requests submitted to sessions belonging to the driver will also
be queued until
.Fn crypto_unblock
is called.
.Pp
If a driver encounters errors while processing a request,
it should report them via the
.Fa crp_etype
field of
.Fa crp
rather than returning an error directly.
.Pp
.Fa flags
may be set to
.Dv CRYPTO_HINT_MORE
if there are additional requests queued for this driver.
The driver can use this as a hint to batch completion interrupts.
Note that these additional requests may be from different sessions.
.Pp
.Fn crypto_get_driver_session
returns a pointer to the driver-specific per-session data structure
for the session
.Fa crypto_session .
This function can be used in the
.Fn CRYPTODEV_NEWSESSION ,
.Fn CRYPTODEV_PROCESS ,
and
.Fn CRYPTODEV_FREESESSION
callbacks.
.Pp
.Fn crypto_copydata
copies
.Fa size
bytes out of the data buffer for
.Fa crp
into a local buffer pointed to by
.Fa dst .
The bytes are read starting at an offset of
.Fa off
bytes in the request's data buffer.
.Pp
.Fn crypto_copyback
copies
.Fa size
bytes from the local buffer pointed to by
.Fa src
into the data buffer for
.Fa crp .
The bytes are written starting at an offset of
.Fa off
bytes in the request's data buffer.
.Pp
.Fn crypto_read_iv
copies the IV or nonce for
.Fa crp
into the the local buffer pointed to by
.Fa iv .
.Pp
A driver calls
.Fn crypto_done
to mark the request
.Fa crp
as completed.
Any errors should be set in
.Fa crp_etype
prior to calling this function.
.Pp
If a driver defers a request by returning
.Dv ERESTART
from
.Dv CRYPTO_PROCESS ,
the framework will queue all requests for the driver until the driver calls
.Fn crypto_unblock
to indicate that the temporary resource shortage has been relieved.
For example,
if a driver returns
.Dv ERESTART
due to a full command ring,
it would invoke
.Fn crypto_unblock
from a command completion interrupt that makes a command ring entry available.
.Fa driverid
is the value returned by
.Fn crypto_get_driverid .
.Fa what
indicates which types of requests the driver is able to handle again:
.Bl -tag -width "CRYPTO_ASYMQ"
.It Dv CRYPTO_SYMQ
indicates that the driver is able to handle symmetric requests passed to
.Fn CRYPTODEV_PROCESS .
.It Dv CRYPTO_ASYMQ
indicates that the driver is able to handle asymmetric requests passed to
.Fn CRYPTODEV_KPROCESS .
.El
.Pp
.Fn crypto_apply
is a helper routine that can be used to invoke a caller-supplied function
to a region of the data buffer for
.Fa crp .
The function
.Fa f
is called one or more times.
For each invocation,
the first argument to
.Fa f
is the value of
.Fa arg passed to
.Fn crypto_apply .
The second and third arguments to
.Fa f
are a pointer and length to a segment of the buffer mapped into the kernel.
The function is called enough times to cover the
.Fa len
bytes of the data buffer which starts at an offset
.Fa off .
If any invocation of
.Fa f
returns a non-zero value,
.Fn crypto_apply
immediately returns that value without invoking
.Fa f
on any remaining segments of the region,
otherwise
.Fn crypto_apply
returns the value from the final call to
.Fa f .
.Pp
.Fn crypto_contiguous_subsegment
attempts to locate a single, virtually-contiguous segment of the data buffer
for
.Fa crp .
The segment must be
.Fa len
bytes long and start at an offset of
.Fa skip
bytes.
If a segment is found,
a pointer to the start of the segment is returned.
Otherwise,
.Dv NULL
is returned.
.Pp
.Fn hmac_init_ipad
prepares an authentication context to generate the inner hash of an HMAC.
.Fa axf
is a software implementation of an authentication algorithm such as the
value returned by
.Fn crypto_auth_hash .
.Fa key
is a pointer to a HMAC key of
.Fa klen
bytes.
.Fa auth_ctx
points to a valid authentication context for the desired algorithm.
The function initializes the context with the supplied key.
.Pp
.Fn hmac_init_opad
is similar to
.Fn hmac_init_ipad
except that it prepares an authentication context to generate the
outer hash of an HMAC.
.Sh RETURN VALUES
.Fn crypto_apply
returns the return value from the caller-supplied callback function.
.Pp
.Fn crypto_contiguous_subsegment
returns a pointer to a contiguous segment or
.Dv NULL .
.Pp
.Fn crypto_get_driverid
returns a driver identifier on success or -1 on error.
.Pp
.Fn crypto_unblock ,
.Fn crypto_unregister_all ,
.Fn CRYPTODEV_FREESESSION ,
.Fn CRYPTODEV_NEWSESSION ,
and
.Fn CRYPTODEV_PROCESS
return zero on success or an error on failure.
.Pp
.Fn CRYPTODEV_PROBESESSION
returns a negative value on success or an error on failure.
.Sh SEE ALSO
.Xr crypto 7 ,
.Xr crypto 9 ,
.Xr crypto_request 9 ,
.Xr crypto_session 9