path: root/share/man/man9/crypto.9

.\"	$OpenBSD: crypto.9,v 1.2 2000/04/28 05:51:40 angelos Exp $
.\"
.\" The author of this man page is Angelos D. Keromytis (angelos@cis.upenn.edu)
.\"
.\" Copyright (c) 2000 Angelos D. Keromytis
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.\" modification of this software.
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.Dd April 21, 2000
.Dt CRYPTO 9
.Os
.Sh NAME
.Nm crypto
.Nd API for cryptographic services in the kernel
.Sh SYNOPSIS
.Fd #include <crypto/crypto>
.Ft int32_t
.Fn crypto_get_driverid "void"
.Ft int
.Fn crypto_register "u_int32_t" "int" "int (*)(u_int32_t *, struct cryptoini *)" "int (*)(u_int64_t)" "int (*)(struct cryptop *)"
.Ft int
.Fn crypto_unregister "u_int32_t" "int"
.Ft int
.Fn crypto_newsession "u_int64_t *" "struct cryptoini *"
.Ft int
.Fn crypto_freesession "u_int64_t"
.Ft int
.Fn crypto_dispatch "struct cryptop *"
.Ft struct cryptop *
.Fn crypto_getreq "int"
.Ft void
.Fn crypto_freereq "void"
.Bd -literal

#define EALG_MAX_BLOCK_LEN      8

struct cryptoini
{
    int                cri_alg;
    int                cri_klen;
    int                cri_rnd;
    caddr_t            cri_key;
    u_int8_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;
    struct cryptodesc *crd_next;
};

struct cryptop
{
    u_int64_t          crp_sid;
    int                crp_ilen;
    int                crp_olen;
    int                crp_alloctype;
    int                crp_etype;
    int                crp_flags;
    caddr_t            crp_buf;
    caddr_t            crp_opaque1;
    caddr_t            crp_opaque2;
    caddr_t            crp_opaque3;
    caddr_t            crp_opaque4;
    struct cryptodesc *crp_desc;
    int              (*crp_callback) (struct cryptop *);
};
.Ed
.br
.Sh DESCRIPTION
.Nm
is a framework for drivers of cryptographic hardware to register with
the kernel so ``consumers'' (other kernel subsystems, and eventually
users through an appropriate 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
Since the consumers may not be associated with a process, drivers may
not use
.Xr tsleep 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 an 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,
.Va EAGAIN ,
is used to indicate that a session number has changed and that the
request may be re-submitted immediately with the new session
number. 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 there is no callback mechanism used.
.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. On
success, the first argument will contain the Session Identifier
(SID). The second argument contains all the necessary information for
the driver to establish the session. The various fields in the
.Va cryptoini
structure are:
.Bl -tag -width foobarmoocow 
.It cri_alg
Contains an algorithm identifier. Currently supported algorithms are:
.Bd -literal
CRYPTO_DES_CBC
CRYPTO_3DES_CBC
CRYPTO_BLF_CBC
CRYPTO_CAST_CBC
CRYPTO_SKIPJACK_CBC
CRYPTO_MD5_HMAC96
CRYPTO_SHA1_HMAC96
CRYPTO_RIPEMD160_HMAC96
CRYPTO_MD5_KPDK
CRYPTO_SHA1_KPDK
.Ed
.Br
.It cri_klen
Specifies the length of the key in bits, for variable-size key
algorithms.
.It cri_rnd
Specifies the number of rounds to be used with the algorithm, for
variable-round algorithms.
.It cri_key
Contains the key to be used with the algorithm.
.It cri_iv
Contains an explicit initialization vector (IV), if it does not prefix
the data. This field is ignored during initialization. If no IV is
explicitly passed (see below on details), a random IV is used by the
device driver processing the request.
.It cri_next
Contains a pointer to another
.Va cryptoini
structure. Multiple such structures may be linked, to establish
multi-algorithm sessions (
.Xr ipsec 4
is an example consumer of such a feature).
.El
.Pp
The
.Va cryptoini
structure and its contents will not be modified by the framework (or
the drivers used). Subsequent requests for processing that use the
SID returned will avoid the cost of re-initializing the hardware (in
essence, SID acts as an index in the session cache of the driver).
.Pp
.Fn crypto_freesession
is called with the SID returned by
.Fn crypto_newsession
to disestablish the session.
.Pp
.Fn crypto_dispatch
is called to process a request. The various fields in the
.Va cryptop
structure are:
.Bl -tag -width crp_alloctype
.It crp_sid
Contains the SID.
.It crp_ilen
Indicates the total length in bytes of the buffer to be processed.
.It crp_olen
On return, contains the total length of the result. For symmetric
crypto operations, this will be the same as the input length.
.It crp_alloctype
Indicates the type of buffer, as used in the kernel
.Xr malloc 9
routine. This will be used if the framework needs to allocate a new
buffer for the result (or for re-formatting the input).
.It crp_callback
This routine is invoked upon completion of the request, whether
successful or not. If the request was not successful, an error code is
set in the
.Va crp_etype
field.
.It crp_etype 
Contains the error type, if any errors were encountered, or zero if
the request was successfully processed. If the
.Va EAGAIN
error code is returned, the SID has changed (and has been recorded in
the
.Va crp_sid
field). The consumer should record the new SID 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
Note that this field only makes sense when examined by
the callback routine specified in
.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 crp_flags
Is a bitmask of flags associated with this request. Currently defined
flags are:
.Bl -tag -width CRYPTO_F_IMBUF
.It CRYPTO_F_IMBUF
The buffer pointed to by
.Va crp_buf
is an mbuf chain.
.El
.Br
.It crp_buf
Points to the input buffer. On return (when the callback is invoked),
it contains the result of the request. The input buffer may be an mbuf
chain or a contiguous buffer (of a type identified by
.Va crp_alloctype ),
depending on
.Va crp_flags .
.It crp_opaque1
.It crp_opaque2
.It crp_opaque3
.It crp_opaque4
These are passed through the crypto framework untouched and are
intended for the invoking application's use.
.It crp_desc
This is 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=crd_inject
.It crd_skip
The offset in the input buffer where processing should start.
.It crd_len
How many bytes, after
.Va crd_skip ,
should be processed.
.It crd_inject
Offset from the beginning of the buffer to insert any results. For
encryption algorithms, this is where the initialization vector
(IV) will be inserted when encrypting or where it can be found when
decrypting (subject to
.Va crd_flags ).
For MAC algorithms, this is where the result of the keyed hash will be
inserted.
.It crd_flags
The following flags are defined:
.Bl -tag -width=CRD_F_IV_EXPLICIT
.it CRD_F_ENCRYPT
For encryption algorithms, this bit is set when encryption is required
(when not set, decryption is performed).
.It CRD_F_IV_PRESENT
For encryption algorithms, this bit is set when the IV already
precedes the data, so the
.Va crd_inject
value will be ignored and no IV will be written in the
buffer. Otherwise, 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. Some applications that do special ``IV
cooking'', such as the half-IV mode in
.Xr ipsec 4 ,
can use this flag to indicate the the IV should not be written on the
packet. This flag is typically used in conjunction with the
.Va CRD_F_IV_EXPLICIT
flag.
.It CRD_F_IV_EXPLICIT
For encryption algorithms, this bit is set when the IV is explicitly
provided by the consumer in the
.Va crd_iv
fiels. Otherwise, for encryption operations the IV is provided for by
the driver used to perform the operation, whereas for decryption
operations it is pointed to by the
.Va crd_inject
field. This flag is typically used when the IV is calculated ``on the
fly'' by the consumer, and does not precede the data (some
.Xr ipsec 4
configurations, and the encrypted swap are two such examples).
.El
.It crd_alg
.It crd_klen
.It crd_rnd
.It crd_key
.It crd_iv
These have the exact same meaning as the corresponding fields in the
.Va cryptoini
structure. These fields 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 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
.Va cryptop
structure with a linked list of as many
.Va cryptodesc
structures as were specified in the argument passed to it.
.Pp
.Fn crypto_freereq
deallocates a structure
.Va cryptop
and any
.Va cryptodesc
structures linked to it. Note that it is the responsibility of the
callback routine to do the necessary cleanups associated with the
opaque fields in the
.Va cryptop
structure.
.Pp
.Sh DRIVER-SIDE API
The
.Fn crypto_get_driverid ,
.Fn crypto_register ,
and
.Fn crypto_unregister
routines are used by drivers that provide support for cryptographic
primitives to register and unregister with the kernel crypto services
framework. Drivers must first use the
.Fn crypto_get_driverid
function to acquire a driver identifier. For each algorithm the driver
supports, it must then call
.Fn crypto_register .
The first two arguments are the driver and algorithm identifiers. The
last three arguments must be provided in the first call to
.Fn crypto_register
and are ignored in all subsequent calls. They are pointers to three
driver-provided functions that the framework may call to establish new
cryptographic context with the driver, free already established
context, and ask for a request to be processed (encrypt, decrypt,
etc.)
.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
.Xr pcmcia 4
crypto cards that are being ejected will invoke this routine for all
algorithms supported by the card.
.Pp
The calling convention for the three driver-supplied routines is:
.Bd -literal
int (*newsession) (u_int32_t *, struct cryptoini *);
int (*freesession) (u_int64_t);
int (*process) (struct cryptop *);
.Ed
.Pp
On invocation, the first argument to
.Fn newsession
contains the driver identifier obtained via
.Fn crypto_get_driverid .
On successfully returning, it should contain a driver-specific session
identifier. The second argument is identical to that of
.Fn crypto_newsession .
.Pp
The
.Fn freesession
routine takes as argument the SID (which is the concatenation of the
driver identifier and the driver-specific session identifier). It
should clear any context associated with the session (clear hardware
registers, memory, etc.)
.Pp
The
.Fn process
routine is invoked with a request to perform crypto 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 error, the error indication must be
placed in the
.Va crp_etype
field of the
.Va cryptop
structure, and the callback routine invoked as well, to perform the
necessary cleanup or to re-issue the request. Session migration may be
performed, as mentioned previously.
.Pp
.Sh RETURN VALUES
.Fn crypto_register ,
.Fn crypto_unregister ,
.Fn crypto_newsession ,
and
.Fn crypto_freesession
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
.Va cryptop
structure and
.Dv NULL
on failure.
.Fn crypto_dispatch
returns
.Dv EINVAL
is 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.
.Br
.Sh CODE REFERENCES
Most of the framework code can be found in
.Pa sys/crypto/crypto.c
.Br
.Sh SEE ALSO
.Xr ipsec 4 ,
.Xr malloc 9 ,
.Xr pcmcia 4 ,
.Xr tsleep 9
.Br
.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's 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. Note that 3DES is considered one algorithm (and not three
instances of DES). Thus, 3DES and DES could be mixed in the same
request.
.Pp
A queue for completed operations should be implemented and processed
at some software
.Xr spl 9
level, to avoid overall system latency issues, and potential kernel
stack exhaustion while processing a callback.
.Pp
We need a userland device for exposing the framework to userland. This
will be particularly useful for public key operations in hardware.
.Pp
We have not experimented yet with public key operations hardware. The
framework should support this.
.Pp
When SMP time comes, we will support use of a second processor (or
more) as a crypto device (this is actually AMP, but we need the same
basic support).