man/man9/crypto.9

.\"	$OpenBSD: crypto.9,v 1.19 2002/07/16 06:31:57 angelos Exp $
.\"
.\" The author of this manual page is Angelos D. Keromytis (angelos@cis.upenn.edu)
.\"
.\" Copyright (c) 2000, 2001 Angelos D. Keromytis
.\"
.\" Permission to use, copy, and modify this software with or without fee
.\" is hereby granted, provided that this entire notice is included in
.\" all source code copies of any software which is or includes a copy or
.\" modification of this software.
.\"
.\" THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
.\" IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
.\" REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
.\" MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
.\" PURPOSE.
.\"
.\" $FreeBSD$
.\"
.Dd December 17, 2019
.Dt CRYPTO 9
.Os
.Sh NAME
.Nm crypto
.Nd API for cryptographic services in the kernel
.Sh SYNOPSIS
.In opencrypto/cryptodev.h
.Ft int32_t
.Fn crypto_get_driverid "device_t dev" "size_t session_size" "int flags"
.Ft int
.Fn crypto_register "uint32_t driverid" "int alg" "uint16_t maxoplen" "uint32_t flags"
.Ft int
.Fn crypto_kregister "uint32_t driverid" "int kalg" "uint32_t flags"
.Ft int
.Fn crypto_unregister "uint32_t driverid" "int alg"
.Ft int
.Fn crypto_unregister_all "uint32_t driverid"
.Ft void
.Fn crypto_done "struct cryptop *crp"
.Ft void
.Fn crypto_kdone "struct cryptkop *krp"
.Ft int
.Fn crypto_find_driver "const char *match"
.Ft int
.Fn crypto_newsession "crypto_session_t *cses" "struct cryptoini *cri" "int crid"
.Ft int
.Fn crypto_freesession "crypto_session_t cses"
.Ft int
.Fn crypto_dispatch "struct cryptop *crp"
.Ft int
.Fn crypto_kdispatch "struct cryptkop *krp"
.Ft int
.Fn crypto_unblock "uint32_t driverid" "int what"
.Ft "struct cryptop *"
.Fn crypto_getreq "int num"
.Ft void
.Fn crypto_freereq "struct cryptop *crp"
.Bd -literal
#define	CRYPTO_SYMQ	0x1
#define	CRYPTO_ASYMQ	0x2

#define EALG_MAX_BLOCK_LEN      16

struct cryptoini {
	int                cri_alg;
	int                cri_klen;
	int                cri_mlen;
	caddr_t            cri_key;
	uint8_t            cri_iv[EALG_MAX_BLOCK_LEN];
	struct cryptoini  *cri_next;
};

struct cryptodesc {
	int                crd_skip;
	int                crd_len;
	int                crd_inject;
	int                crd_flags;
	struct cryptoini   CRD_INI;
#define crd_iv          CRD_INI.cri_iv
#define crd_key         CRD_INI.cri_key
#define crd_alg         CRD_INI.cri_alg
#define crd_klen        CRD_INI.cri_klen
	struct cryptodesc *crd_next;
};

struct cryptop {
	TAILQ_ENTRY(cryptop) crp_next;
	crypto_session_t   crp_session;
	int                crp_ilen;
	int                crp_olen;
	int                crp_etype;
	int                crp_flags;
	caddr_t            crp_buf;
	caddr_t            crp_opaque;
	struct cryptodesc *crp_desc;
	int              (*crp_callback) (struct cryptop *);
	caddr_t            crp_mac;
};

struct crparam {
        caddr_t         crp_p;
        u_int           crp_nbits;
};

#define CRK_MAXPARAM    8

struct cryptkop {
        TAILQ_ENTRY(cryptkop) krp_next;
        u_int              krp_op;         /* ie. CRK_MOD_EXP or other */
        u_int              krp_status;     /* return status */
        u_short            krp_iparams;    /* # of input parameters */
        u_short            krp_oparams;    /* # of output parameters */
        uint32_t           krp_hid;
        struct crparam     krp_param[CRK_MAXPARAM];
        int               (*krp_callback)(struct cryptkop *);
};
.Ed
.Sh DESCRIPTION
.Nm
is a framework for drivers of cryptographic hardware to register with
the kernel so
.Dq consumers
(other kernel subsystems, and
users through the
.Pa /dev/crypto
device) are able to make use of it.
Drivers register with the framework the algorithms they support,
and provide entry points (functions) the framework may call to
establish, use, and tear down sessions.
Sessions are used to cache cryptographic information in a particular driver
(or associated hardware), so initialization is not needed with every request.
Consumers of cryptographic services pass a set of
descriptors that instruct the framework (and the drivers registered
with it) of the operations that should be applied on the data (more
than one cryptographic operation can be requested).
.Pp
Keying operations are supported as well.
Unlike the symmetric operators described above,
these sessionless commands perform mathematical operations using
input and output parameters.
.Pp
Since the consumers may not be associated with a process, drivers may
not
.Xr 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,
.Er 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.
.Pp
The
.Fn crypto_find_driver
returns the driver id of the device whose name matches
.Fa match .
.Fa 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.
.Pp
The
.Fn crypto_newsession
routine is called by consumers of cryptographic services (such as the
.Xr ipsec 4
stack) that wish to establish a new session with the framework.
The
.Fa cri
argument points to a
.Vt cryptoini
structure containing all the necessary information for
the driver to establish the session.
The
.Fa crid
argument is either a specific driver id or a bitmask of flags.
The flags are
.Dv CRYPTOCAP_F_HARDWARE ,
to select hardware devices,
or
.Dv 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
.Fa *cses .
The
.Vt cryptoini
structure pointed to by
.Fa cri
contains these fields:
.Bl -tag -width ".Va cri_next"
.It Va cri_alg
An algorithm identifier.
Currently supported algorithms are:
.Pp
.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact
.It Dv CRYPTO_AES_128_NIST_GMAC
.It Dv CRYPTO_AES_192_NIST_GMAC
.It Dv CRYPTO_AES_256_NIST_GMAC
.It Dv CRYPTO_AES_CBC
.It Dv CRYPTO_AES_CCM_16
.It Dv CRYPTO_AES_CCM_CBC_MAC
.It Dv CRYPTO_AES_ICM
.It Dv CRYPTO_AES_NIST_GCM_16
.It Dv CRYPTO_AES_NIST_GMAC
.It Dv CRYPTO_AES_XTS
.It Dv CRYPTO_ARC4
.It Dv CRYPTO_BLAKE2B
.It Dv CRYPTO_BLAKE2S
.It Dv CRYPTO_BLF_CBC
.It Dv CRYPTO_CAMELLIA_CBC
.It Dv CRYPTO_CAST_CBC
.It Dv CRYPTO_CHACHA20
.It Dv CRYPTO_DEFLATE_COMP
.It Dv CRYPTO_DES_CBC
.It Dv CRYPTO_3DES_CBC
.It Dv CRYPTO_MD5
.It Dv CRYPTO_MD5_HMAC
.It Dv CRYPTO_MD5_KPDK
.It Dv CRYPTO_NULL_HMAC
.It Dv CRYPTO_NULL_CBC
.It Dv CRYPTO_POLY1305
.It Dv CRYPTO_RIPEMD160
.It Dv CRYPTO_RIPEMD160_HMAC
.It Dv CRYPTO_SHA1
.It Dv CRYPTO_SHA1_HMAC
.It Dv CRYPTO_SHA1_KPDK
.It Dv CRYPTO_SHA2_224
.It Dv CRYPTO_SHA2_224_HMAC
.It Dv CRYPTO_SHA2_256
.It Dv CRYPTO_SHA2_256_HMAC
.It Dv CRYPTO_SHA2_384
.It Dv CRYPTO_SHA2_384_HMAC
.It Dv CRYPTO_SHA2_512
.It Dv CRYPTO_SHA2_512_HMAC
.It Dv CRYPTO_SKIPJACK_CBC
.El
.It Va cri_klen
For variable-size key algorithms, the length of the key in bits.
.It Va cri_mlen
If non-zero, truncate the calculated hash to this many bytes.
.It Va cri_key
The key to be used.
.It Va cri_iv
An explicit initialization vector if it does not prefix
the data.
This field is ignored during initialization
.Pq Nm crypto_newsession .
If no IV is explicitly passed (see below on details), a random IV is used
by the device driver processing the request.
.It Va cri_next
Pointer to another
.Vt cryptoini
structure.
This is used to establish dual-algorithm sessions, such as combining a
cipher with a MAC.
.El
.Pp
The
.Vt cryptoini
structure and its contents will not be modified or referenced by the
framework or any cryptographic drivers.
The memory associated with
.Fa cri
can be released once
.Fn crypto_newsession
returns.
.Pp
.Fn crypto_freesession
is called with the session handle returned by
.Fn crypto_newsession
to free the session.
.Pp
.Fn crypto_dispatch
is called to process a request.
The various fields in the
.Vt cryptop
structure are:
.Bl -tag -width ".Va crp_callback"
.It Va crp_session
The session handle.
.It Va crp_ilen
The total length in bytes of the buffer to be processed.
.It Va 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).
.It Va crp_callback
Callback routine invoked when a request is completed via
.Fn crypto_done .
The callback routine should inspect the
.Va crp_etype
to determine if the request was successfully completed.
.It Va crp_etype
The error type, if any errors were encountered, or zero if
the request was successfully processed.
If the
.Er EAGAIN
error code is returned, the session handle has changed (and has been recorded
in the
.Va 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).
.Pp
This field is only valid in the context of the callback routine specified by
.Va crp_callback .
Errors are returned to the invoker of
.Fn crypto_process
only when enough information is not present to call the callback
routine (i.e., if the pointer passed is
.Dv NULL
or if no callback routine was specified).
.It Va crp_flags
A bitmask of flags associated with this request.
Currently defined flags are:
.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC"
.It Dv CRYPTO_F_IMBUF
The buffer is an mbuf chain pointed to by
.Va crp_mbuf .
.It Dv CRYPTO_F_IOV
The buffer is a
.Vt uio
structure pointed to by
.Va crp_uio .
.It Dv CRYPTO_F_BATCH
Batch operation if possible.
.It Dv CRYPTO_F_CBIMM
Do callback immediately instead of doing it from a dedicated kernel thread.
.It Dv CRYPTO_F_DONE
Operation completed.
.It Dv CRYPTO_F_CBIFSYNC
Do callback immediately if operation is synchronous (that the driver
specified the
.Dv CRYPTOCAP_F_SYNC
flag).
.It Dv 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
.Dv CRYPTOCAP_F_SYNC
flag).
It aims to speed up processing by dispatching crypto operations
on different processors.
.It Dv CRYPTO_F_ASYNC_KEEPORDER
Dispatch callbacks in the same order they are posted.
Only relevant if the
.Dv CRYPTO_F_ASYNC
flag is set and if the operation is synchronous.
.El
.It Va crp_buf
Data buffer unless
.Dv CRYPTO_F_IMBUF
or
.Dv CRYPTO_F_IOV
is set in
.Va crp_flags .
The length in bytes is set in
.Va crp_ilen .
.It Va crp_mbuf
Data buffer mbuf chain when
.Dv CRYPTO_F_IMBUF
is set in
.Va crp_flags .
.It Va crp_uio
.Vt struct uio
data buffer when
.Dv CRYPTO_F_IOV
is set in
.Va crp_flags .
.It Va crp_opaque
Cookie passed through the crypto framework untouched.
It is
intended for the invoking application's use.
.It Va 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:
.Bl -tag -width ".Va crd_inject"
.It Va crd_iv
When the flag
.Dv CRD_F_IV_EXPLICIT
is set, this field contains the IV.
.It Va crd_key
When the
.Dv CRD_F_KEY_EXPLICIT
flag is set, the
.Va crd_key
points to a buffer with encryption or authentication key.
.It Va crd_alg
An algorithm to use.
Must be the same as the one given at newsession time.
.It Va crd_klen
The
.Va crd_key
key length.
.It Va crd_skip
The offset in the input buffer where processing should start.
.It Va crd_len
How many bytes, after
.Va crd_skip ,
should be processed.
.It Va crd_inject
The
.Va 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
.Va crd_flags ) .
For MAC algorithms, this is where the result of the keyed hash will be
inserted.
.It Va crd_flags
The following flags are defined:
.Bl -tag -width 3n
.It Dv CRD_F_ENCRYPT
For encryption algorithms, this bit is set when encryption is required
(when not set, decryption is performed).
.It Dv CRD_F_IV_PRESENT
.\" This flag name has nothing to do w/ it's behavior, fix the name.
For encryption, if this bit is not set the IV used to encrypt the packet
will be written at the location pointed to by
.Va 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
.Dq "IV cooking" ,
such as the half-IV mode in
.Xr 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
.Dv CRD_F_IV_EXPLICIT
flag.
.It Dv CRD_F_IV_EXPLICIT
This bit is set when the IV is explicitly
provided by the consumer in the
.Va 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
.Va crd_inject
field.
This flag is typically used when the IV is calculated
.Dq "on the fly"
by the consumer, and does not precede the data.
.It Dv 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
.Va crd_key
field for the given operation.
Otherwise, the key is taken at newsession time from the
.Va cri_key
field.
As calculating the key schedule may take a while, it is recommended that often
used keys are given their own session.
.It Dv CRD_F_COMP
For compression algorithms, this bit is set when compression is required (when
not set, decompression is performed).
.El
.It Va CRD_INI
This
.Vt 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.
.It Va crd_next
Point to the next descriptor.
Linked operations are useful in protocols such as
.Xr ipsec 4 ,
where multiple cryptographic transforms may be applied on the same
block of data.
.El
.El
.Pp
.Fn crypto_getreq
allocates a
.Vt cryptop
structure with a linked list of
.Fa num
.Vt cryptodesc
structures.
.Pp
.Fn crypto_freereq
deallocates a structure
.Vt cryptop
and any
.Vt 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
.Vt cryptop
structure.
.Pp
.Fn crypto_kdispatch
is called to perform a keying operation.
The various fields in the
.Vt cryptkop
structure are:
.Bl -tag -width ".Va krp_callback"
.It Va krp_op
Operation code, such as
.Dv CRK_MOD_EXP .
.It Va krp_status
Return code.
This
.Va errno Ns -style
variable indicates whether lower level reasons
for operation failure.
.It Va krp_iparams
Number of input parameters to the specified operation.
Note that each operation has a (typically hardwired) number of such parameters.
.It Va krp_oparams
Number of output parameters from the specified operation.
Note that each operation has a (typically hardwired) number of such parameters.
.It Va krp_kvp
An array of kernel memory blocks containing the parameters.
.It Va krp_hid
Identifier specifying which low-level driver is being used.
.It Va krp_callback
Callback called on completion of a keying operation.
.El
.Sh DRIVER-SIDE API
The
.Fn crypto_get_driverid ,
.Fn crypto_get_driver_session ,
.Fn crypto_register ,
.Fn crypto_kregister ,
.Fn crypto_unregister ,
.Fn crypto_unblock ,
and
.Fn crypto_done
routines are used by drivers that provide support for cryptographic
primitives to register and unregister with the kernel crypto services
framework.
.Pp
Drivers must first use the
.Fn crypto_get_driverid
function to acquire a driver identifier, specifying the
.Fa flags
as an argument.
One of
.Dv CRYPTOCAP_F_SOFTWARE
or
.Dv CRYPTOCAP_F_HARDWARE
must be specified.
The
.Dv CRYPTOCAP_F_SYNC
may also be specified, and should be specified if the driver does all of
it's operations synchronously.
Drivers must pass the size of their session structure as the second argument.
An appropriately sized memory will be allocated by the framework, zeroed, and
passed to the driver's
.Fn newsession
method.
.Pp
For each algorithm the driver supports, it must then call
.Fn crypto_register .
The first two arguments are the driver and algorithm identifiers.
The next two arguments specify the largest possible operator length (in bits,
important for public key operations) and flags for this algorithm.
.Pp
.Fn crypto_unregister
is called by drivers that wish to withdraw support for an algorithm.
The two arguments are the driver and algorithm identifiers, respectively.
Typically, drivers for
PCMCIA
crypto cards that are being ejected will invoke this routine for all
algorithms supported by the card.
.Fn crypto_unregister_all
will unregister all algorithms registered by a driver
and the driver will be disabled (no new sessions will be allocated on
that driver, and any existing sessions will be migrated to other
drivers).
The same will be done if all algorithms associated with a driver are
unregistered one by one.
After a call to
.Fn crypto_unregister_all
there will be no threads in either the newsession or freesession function
of the driver.
.Pp
The calling convention for the driver-supplied routines are:
.Pp
.Bl -item -compact
.It
.Ft int
.Fn \*[lp]*newsession\*[rp] "device_t" "crypto_session_t" "struct cryptoini *" ;
.It
.Ft void
.Fn \*[lp]*freesession\*[rp] "device_t" "crypto_session_t" ;
.It
.Ft int
.Fn \*[lp]*process\*[rp] "device_t" "struct cryptop *" "int" ;
.It
.Ft int
.Fn \*[lp]*kprocess\*[rp] "device_t" "struct cryptkop *" "int" ;
.El
.Pp
On invocation, the first argument to
all routines is the
.Fa device_t
that was provided to
.Fn crypto_get_driverid .
The second argument to
.Fn newsession
is the opaque session handle for the new session.
The third argument is identical to that of
.Fn crypto_newsession .
.Pp
Drivers obtain a pointer to their session memory by invoking
.Fn crypto_get_driver_session
on the opaque
.Vt crypto_session_t
handle.
.Pp
The
.Fn freesession
routine takes as arguments the opaque data value and the session handle.
It should clear any context associated with the session (clear hardware
registers, memory, etc.).
If no resources need to be released other than the contents of session memory,
the method is optional.
The
.Nm
framework will zero and release the allocated session memory (after running the
.Fn freesession
method, if one exists).
.Pp
The
.Fn process
routine is invoked with a request to perform crypto processing.
This routine must not block or sleep, but should queue the request and return
immediately or process the request to completion.
In case of an unrecoverable error, the error indication must be placed in the
.Va crp_etype
field of the
.Vt cryptop
structure.
When the request is completed, or an error is detected, the
.Fn process
routine must invoke
.Fn crypto_done .
Session migration may be performed, as mentioned previously.
.Pp
In case of a temporary resource exhaustion, the
.Fn process
routine may return
.Er ERESTART
in which case the crypto services will requeue the request, mark the driver
as
.Dq blocked ,
and stop submitting requests for processing.
The driver is then responsible for notifying the crypto services
when it is again able to process requests through the
.Fn crypto_unblock
routine.
This simple flow control mechanism should only be used for short-lived
resource exhaustion as it causes operations to be queued in the crypto
layer.
Doing so is preferable to returning an error in such cases as
it can cause network protocols to degrade performance by treating the
failure much like a lost packet.
.Pp
The
.Fn kprocess
routine is invoked with a request to perform crypto key processing.
This routine must not block, but should queue the request and return
immediately.
Upon processing the request, the callback routine should be invoked.
In case of an unrecoverable error, the error indication must be placed in the
.Va krp_status
field of the
.Vt cryptkop
structure.
When the request is completed, or an error is detected, the
.Fn kprocess
routine should invoked
.Fn crypto_kdone .
.Sh RETURN VALUES
.Fn crypto_register ,
.Fn crypto_kregister ,
.Fn crypto_unregister ,
.Fn crypto_newsession ,
.Fn crypto_freesession ,
and
.Fn crypto_unblock
return 0 on success, or an error code on failure.
.Fn crypto_get_driverid
returns a non-negative value on error, and \-1 on failure.
.Fn crypto_getreq
returns a pointer to a
.Vt cryptop
structure and
.Dv NULL
on failure.
.Fn crypto_dispatch
returns
.Er EINVAL
if its argument or the callback function was
.Dv NULL ,
and 0 otherwise.
The callback is provided with an error code in case of failure, in the
.Va crp_etype
field.
.Sh FILES
.Bl -tag -width ".Pa sys/opencrypto/crypto.c"
.It Pa sys/opencrypto/crypto.c
most of the framework code
.El
.Sh SEE ALSO
.Xr crypto 4 ,
.Xr ipsec 4 ,
.Xr crypto 7 ,
.Xr malloc 9 ,
.Xr sleep 9
.Sh HISTORY
The cryptographic framework first appeared in
.Ox 2.7
and was written by
.An Angelos D. Keromytis Aq Mt angelos@openbsd.org .
.Sh BUGS
The framework currently assumes that all the algorithms in a
.Fn crypto_newsession
operation must be available by the same driver.
If that is not the case, session initialization will fail.
.Pp
The framework also needs a mechanism for determining which driver is
best for a specific set of algorithms associated with a session.
Some type of benchmarking is in order here.
.Pp
Multiple instances of the same algorithm in the same session are not
supported.