CRYPTO(9) BSD Kernel Manual CRYPTO(9)
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 en-
try 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 opera-
tions 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 mechan-
ism 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 call-
back 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 ses-
sion 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 algo-
rithms 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 algo-
rithm, 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 initiali-
zation. If no IV is explicitly passed (see below on de-
tails), 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 includ-
ing 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 re-
formatting 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 ap-
propriate 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 re-
quests. In this case, the request may be re-submitted im-
mediately. This mechanism is used by the framework to per-
form 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 re-
turned 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 pro-
vides information about what type of cryptographic opera-
tion 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 en-
crypting or where it can be found when decrypting (sub-
ject 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 per-
formed).
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 applica-
tions 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 pro-
vided by the consumer in the crd_iv
fields. Otherwise, for encryption
operations the IV is provided for by
the driver used to perform the opera-
tion, whereas for decryption opera-
tions it is pointed to by the
crd_inject field. This flag is typi-
cally used when the IV is calculated
"on the fly" by the consumer, and
does not precede the data (some
ipsec(4) configurations, and the en-
crypted swap are two such examples).
CRD_F_COMP For compression algorithms, this bit
is set when compression is required
(when not set, decompression is per-
formed).
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 use-
ful in protocols such as ipsec(4), where multiple cryp-
tographic 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 call-
back 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 parame-
ters.
krp_hid Identifier specifying which low-level driver is being
used.
krp_callback Callback called on completion of a keying operation.
DRIVER-SIDE API
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 iden-
tifier. The second argument is an array of CRYPTO_ALGORITHM_MAX + 1 ele-
ments, indicating which algorithms are supported. The last three argu-
ments are pointers to three driver-provided functions that the framework
may call to establish new cryptographic context with the driver, free al-
ready established context, and ask for a request to be processed (en-
crypt, 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 al-
gorithms 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 unre-
gistered 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 argu-
ment is identical to that of crypto_newsession().
The freesession() routine takes as argument the SID (which is the con-
catenation of the driver identifier and the driver-specific session iden-
tifier). 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 pro-
cessing. 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 com-
pleted, or an error is detected, the process() routine should invoke
crypto_done(). Session migration may be performed, as mentioned previous-
ly.
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 non-negative 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 sup-
ported. Note that 3DES is considered one algorithm (and not three in-
stances 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 sup-
port).
MirBSD #10-current April 21, 2000 6