crypto - API for cryptographic services in the kernel
#include <crypto/cryptodev.h>
int32_t
crypto_get_driverid(u_int8_t);
int
crypto_register(u_int32_t, int *,
int (*)(u_int32_t *, struct cryptoini *), int
(*)(u_int64_t),
int (*)(struct cryptop *));
int
crypto_kregister(u_int32_t, int *, int (*)(struct cryptkop
*));
int
crypto_unregister(u_int32_t, int);
void
crypto_done(struct cryptop *);
void
crypto_kdone(struct cryptkop *);
int
crypto_newsession(u_int64_t *, struct cryptoini *, int);
int
crypto_freesession(u_int64_t);
int
crypto_dispatch(struct cryptop *);
int
crypto_kdispatch(struct cryptkop *);
struct cryptop *
crypto_getreq(int);
void
crypto_freereq(struct cryptop *);
#define EALG_MAX_BLOCK_LEN 16
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_opaque;
struct cryptodesc *crp_desc;
int (*crp_callback)(struct cryptop *);
struct cryptop *crp_next;
caddr_t crp_mac;
};
struct crparam {
caddr_t crp_p;
u_int crp_nbits;
};
#define CRK_MAXPARAM 8
struct cryptkop {
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 */
u_int32_t krp_hid;
struct crparam krp_param[CRK_MAXPARAM]; /*
kvm */
int (*krp_callback)(struct cryptkop
*);
struct cryptkop *krp_next;
};
crypto 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).
Keying operations are supported as well. Unlike the symmetric operators
described above, these sessionless commands perform mathematical operations
using input and output parameters.
Since the consumers may not be associated with a process,
drivers may not
use 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, 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.
The crypto_newsession() routine is called by consumers of
cryptographic
services (such as the 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
third argument
indicates whether a hardware driver should be used (1) or
not (0). The
various fields in the cryptoini structure are:
cri_alg Contains an algorithm identifier. Currently
supported algorithms
are:
CRYPTO_DES_CBC
CRYPTO_3DES_CBC
CRYPTO_BLF_CBC
CRYPTO_CAST_CBC
CRYPTO_SKIPJACK_CBC
CRYPTO_MD5_HMAC
CRYPTO_SHA1_HMAC
CRYPTO_RIPEMD160_HMAC
CRYPTO_MD5_KPDK
CRYPTO_SHA1_KPDK
CRYPTO_AES_CBC
CRYPTO_ARC4
CRYPTO_MD5
CRYPTO_SHA1
cri_klen Specifies the length of the key in bits, for
variable-size
key algorithms.
cri_rnd Specifies the number of rounds to be used with
the algorithm,
for variable-round algorithms.
cri_key Contains the key to be used with the algorithm.
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.
cri_next Contains a pointer to another cryptoini structure. Multiple
such structures may be linked to establish
multi-algorithm
sessions (ipsec(4) is an example consumer of such a
feature).
The 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).
crypto_freesession() is called with the SID returned by
crypto_newsession() to disestablish the session.
crypto_dispatch() is called to process a request. The various fields in
the cryptop structure are:
crp_sid Contains the SID.
crp_ilen Indicates the total length in bytes of the
buffer to be
processed.
crp_olen On return, contains the length of the result,
not including
crd_skip. For symmetric crypto operations, this will
be the same as the input length.
crp_alloctype Indicates the type of buffer, as used in the
kernel
malloc(9) routine. This will be used if the
framework
needs to allocate a new buffer for the result
(or for reformatting
the input).
crp_callback This routine is invoked upon completion of
the request,
whether successful or not. It is invoked
through the
crypto_done() routine. If the request was
not successful,
an error code is set in the crp_etype field.
It is the
responsibility of the callback routine to set
the appropriate
spl(9) level.
crp_etype Contains the error type, if any errors were
encountered,
or zero if the request was successfully processed. If the
EAGAIN error code is returned, the SID has
changed (and
has been recorded in the crp_sid field). The
consumer
should record the new SID and use it in all
subsequent requests.
In this case, the request may be resubmitted 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).
Note that this field only makes sense when
examined by the
callback routine specified in crp_callback.
Errors are
returned to the invoker of crypto_process()
only when
enough information is not present to call the
callback
routine (i.e., if the pointer passed is NULL
or if no
callback routine was specified).
crp_flags Is a bitmask of flags associated with this
request. Currently
defined flags are:
CRYPTO_F_IMBUF The buffer pointed to by
crp_buf is an
mbuf chain.
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 crp_alloctype), depending on
crp_flags.
crp_opaque This is passed through the crypto framework
untouched and
is intended for the invoking application's
use.
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:
crd_skip
The offset in the input buffer where processing should
start.
crd_len
How many bytes, after crd_skip, should be
processed.
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 crd_flags). For MAC algorithms,
this is where
the result of the keyed hash will be inserted.
crd_flags
The following flags are defined:
CRD_F_ENCRYPT For encryption algorithms, this bit
is set when encryption
is required
(when not set, decryption is performed).
CRD_F_IV_PRESENT For encryption algorithms, this bit
is set when the IV already precedes
the data, so the
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
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
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
CRD_F_IV_EXPLICIT
flag.
CRD_F_IV_EXPLICIT For encryption algorithms, this bit
is set when the IV is
explicitly provided
by the consumer in
the crd_iv
fields. 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
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
ipsec(4) configurations,
and the encrypted
swap are two
such examples).
CRD_F_COMP For compression algorithms, this bit
is set when compression
is required
(when not set, decompression is performed).
CRD_INI
This 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.
crd_next
Point to the next descriptor. Linked operations are
useful in protocols such as ipsec(4), where
multiple
cryptographic transforms may be applied on
the same
block of data.
crypto_getreq() allocates a cryptop structure with a linked
list of as
many cryptodesc structures as were specified in the argument
passed to
it.
crypto_freereq() deallocates a structure cryptop and any
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 cryptop structure.
crypto_kdispatch() is called to perform a keying operation.
The various
fields in the cryptkop structure are:
krp_op Operation code, such as CRK_MOD_EXP.
krp_status Return code. This errno-style variable indicates whether
there were lower level reasons for operation
failure.
krp_iparams Number of input parameters to the specified
operation.
Note that each operation has a (typically
hardwired) number
of such parameters.
krp_oparams Number of output parameters from the specified operation.
Note that each operation has a (typically
hardwired) number
of such parameters.
krp_kvp An array of kernel memory blocks containing
the parameters.
krp_hid Identifier specifying which low-level driver
is being
used.
krp_callback Callback called on completion of a keying operation.
The crypto_get_driverid(), crypto_register(),
crypto_kregister(),
crypto_unregister(), and crypto_done() 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
crypto_get_driverid() function to acquire a driver identifier, specifying
the cc_flags as an argument (normally 0, but software-only
drivers should
specify CRYPTOCAP_F_SOFTWARE). For each algorithm the driver supports,
it must then call crypto_register(). The first argument is
the driver
identifier. The second argument is an array of CRYPTO_ALGORITHM_MAX + 1
elements, indicating which algorithms are supported. The
last three arguments
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.) 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(4) crypto cards that are being ejected will invoke
this routine
for all algorithms supported by the card. If called with
CRYPTO_ALGORITHM_ALL, all algorithms registered for a driver
will be unregistered
in one go 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.
The calling convention for the three driver-supplied routines is:
int (*newsession) (u_int32_t *, struct cryptoini *);
int (*freesession) (u_int64_t);
int (*process) (struct cryptop *);
int (*kprocess) (struct cryptkop *);
On invocation, the first argument to newsession() contains
the driver
identifier obtained via crypto_get_driverid(). On successfully returning,
it should contain a driver-specific session identifier.
The second
argument is identical to that of crypto_newsession().
The 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.).
The 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 crp_etype field of the cryptop structure. When the
request is
completed, or an error is detected, the process() routine
should invoke
crypto_done(). Session migration may be performed, as mentioned previously.
The 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 error, the error indication must be
placed in the krp_status field of the cryptkop structure.
When the request
is completed, or an error is detected, the kprocess()
routine
should invoke crypto_kdone().
crypto_register(), crypto_kregister(), crypto_unregister(),
crypto_newsession(), and crypto_freesession() return 0 on
success, or an
error code on failure. crypto_get_driverid() returns a nonnegative value
on error, and -1 on failure. crypto_getreq() returns a
pointer to a
cryptop structure and NULL on failure. crypto_dispatch()
returns EINVAL
if its argument or the callback function was NULL, and 0
otherwise. The
callback is provided with an error code in case of failure,
in the
crp_etype field.
sys/crypto/crypto.c most of the framework code
ipsec(4), pcmcia(4), malloc(9), tsleep(9)
The cryptographic framework first appeared in OpenBSD 2.7
and was written
by Angelos D. Keromytis <angelos@openbsd.org>.
The framework currently assumes that all the algorithms in a
crypto_newsession() operation must be available by the same
driver. If
that's not the case, session initialization will fail.
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.
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.
A queue for completed operations should be implemented and
processed at
some software spl(9) level, to avoid overall system latency
issues, and
potential kernel stack exhaustion while processing a callback.
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).
OpenBSD 3.6 April 21, 2000
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