xref: /openbsd/share/man/man9/crypto.9 (revision 997a580e)
1.\"	$OpenBSD: crypto.9,v 1.20 2002/11/21 19:42:39 jason Exp $
2.\"
3.\" The author of this man page is Angelos D. Keromytis (angelos@cis.upenn.edu)
4.\"
5.\" Copyright (c) 2000, 2001 Angelos D. Keromytis
6.\"
7.\" Permission to use, copy, and modify this software with or without fee
8.\" is hereby granted, provided that this entire notice is included in
9.\" all source code copies of any software which is or includes a copy or
10.\" modification of this software.
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12.\" THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
13.\" IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
14.\" REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
15.\" MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
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17.\"
18.Dd April 21, 2000
19.Dt CRYPTO 9
20.Os
21.Sh NAME
22.Nm crypto
23.Nd API for cryptographic services in the kernel
24.Sh SYNOPSIS
25.Fd #include <crypto/cryptodev.h>
26.Ft int32_t
27.Fn crypto_get_driverid "u_int8_t"
28.Ft int
29.Fn crypto_register "u_int32_t" "int *" "int (*)(u_int32_t *, struct cryptoini *)" "int (*)(u_int64_t)" "int (*)(struct cryptop *)"
30.Ft int
31.Fn crypto_kregister "u_int32_t" "int *" "int (*)(struct cryptkop *)"
32.Ft int
33.Fn crypto_unregister "u_int32_t" "int"
34.Ft void
35.Fn crypto_done "struct cryptop *"
36.Ft void
37.Fn crypto_kdone "struct cryptkop *"
38.Ft int
39.Fn crypto_newsession "u_int64_t *" "struct cryptoini *" "int"
40.Ft int
41.Fn crypto_freesession "u_int64_t"
42.Ft int
43.Fn crypto_dispatch "struct cryptop *"
44.Ft int
45.Fn crypto_kdispatch "struct cryptkop *"
46.Ft struct cryptop *
47.Fn crypto_getreq "int"
48.Ft void
49.Fn crypto_freereq "void"
50.Bd -literal
51
52#define EALG_MAX_BLOCK_LEN      16
53
54struct cryptoini {
55	int                cri_alg;
56	int                cri_klen;
57	int                cri_rnd;
58	caddr_t            cri_key;
59	u_int8_t           cri_iv[EALG_MAX_BLOCK_LEN];
60	struct cryptoini  *cri_next;
61};
62
63struct cryptodesc {
64	int                crd_skip;
65	int                crd_len;
66	int                crd_inject;
67	int                crd_flags;
68	struct cryptoini   CRD_INI;
69	struct cryptodesc *crd_next;
70};
71
72struct cryptop {
73	u_int64_t          crp_sid;
74	int                crp_ilen;
75	int                crp_olen;
76	int                crp_alloctype;
77	int                crp_etype;
78	int                crp_flags;
79	caddr_t            crp_buf;
80	caddr_t            crp_opaque;
81	struct cryptodesc *crp_desc;
82	int              (*crp_callback) (struct cryptop *);
83	struct cryptop    *crp_next;
84	caddr_t            crp_mac;
85};
86
87struct crparam {
88        caddr_t         crp_p;
89        u_int           crp_nbits;
90};
91
92#define CRK_MAXPARAM    8
93
94struct cryptkop {
95        u_int              krp_op;         /* ie. CRK_MOD_EXP or other */
96        u_int              krp_status;     /* return status */
97        u_short            krp_iparams;    /* # of input parameters */
98        u_short            krp_oparams;    /* # of output parameters */
99        u_int              krp_pad1;
100        struct crparam     krp_param[CRK_MAXPARAM];
101        struct crparam     krp_kvp[CRK_MAXPARAM];
102
103        u_int32_t          krp_hid;
104        int               (*krp_callback)(struct cryptkop *);
105        struct cryptkop   *krp_next;
106};
107.Ed
108.br
109.Sh DESCRIPTION
110.Nm
111is a framework for drivers of cryptographic hardware to register with
112the kernel so
113.Dq consumers
114(other kernel subsystems, and eventually
115users through an appropriate device) are able to make use of it.
116Drivers register with the framework the algorithms they support,
117and provide entry points (functions) the framework may call to
118establish, use, and tear down sessions.
119Sessions are used to cache cryptographic information in a particular driver
120(or associated hardware), so initialization is not needed with every request.
121Consumers of cryptographic services pass a set of
122descriptors that instruct the framework (and the drivers registered
123with it) of the operations that should be applied on the data (more
124than one cryptographic operation can be requested).
125.Pp
126Keying operations are supported as well.
127Unlike the symmetric operators described above,
128these sessionless commands perform mathematical operations using
129input and output parameters.
130.Pp
131Since the consumers may not be associated with a process, drivers may
132not use
133.Xr tsleep 9 .
134The same holds for the framework.
135Thus, a callback mechanism is used
136to notify a consumer that a request has been completed (the
137callback is specified by the consumer on an per-request basis).
138The callback is invoked by the framework whether the request was
139successfully completed or not.
140An error indication is provided in the latter case.
141A specific error code,
142.Er EAGAIN ,
143is used to indicate that a session number has changed and that the
144request may be re-submitted immediately with the new session number.
145Errors are only returned to the invoking function if not
146enough information to call the callback is available (meaning, there
147was a fatal error in verifying the arguments).
148For session initialization and teardown there is no callback mechanism used.
149.br
150.Pp
151The
152.Fn crypto_newsession
153routine is called by consumers of cryptographic services (such as the
154.Xr ipsec 4
155stack) that wish to establish a new session with the framework.
156On success, the first argument will contain the Session Identifier (SID).
157The second argument contains all the necessary information for
158the driver to establish the session.
159The third argument indicates whether a
160hardware driver (1) should be used or not (0).
161The various fields in the
162.Fa cryptoini
163structure are:
164.Bl -tag -width foobarmoocow
165.It Fa cri_alg
166Contains an algorithm identifier.
167Currently supported algorithms are:
168.Bd -literal
169CRYPTO_DES_CBC
170CRYPTO_3DES_CBC
171CRYPTO_BLF_CBC
172CRYPTO_CAST_CBC
173CRYPTO_SKIPJACK_CBC
174CRYPTO_MD5_HMAC
175CRYPTO_SHA1_HMAC
176CRYPTO_RIPEMD160_HMAC
177CRYPTO_MD5_KPDK
178CRYPTO_SHA1_KPDK
179CRYPTO_AES_CBC
180CRYPTO_ARC4
181CRYPTO_MD5
182CRYPTO_SHA1
183.Ed
184.Pp
185.It Fa cri_klen
186Specifies the length of the key in bits, for variable-size key
187algorithms.
188.It Fa cri_rnd
189Specifies the number of rounds to be used with the algorithm, for
190variable-round algorithms.
191.It Fa cri_key
192Contains the key to be used with the algorithm.
193.It Fa cri_iv
194Contains an explicit initialization vector (IV), if it does not prefix
195the data.
196This field is ignored during initialization.
197If no IV is explicitly passed (see below on details), a random IV is used
198by the device driver processing the request.
199.It Fa cri_next
200Contains a pointer to another
201.Fa cryptoini
202structure.
203Multiple such structures may be linked to establish multi-algorithm sessions
204.Pf ( Xr ipsec 4
205is an example consumer of such a feature).
206.El
207.Pp
208The
209.Fa cryptoini
210structure and its contents will not be modified by the framework (or
211the drivers used).
212Subsequent requests for processing that use the
213SID returned will avoid the cost of re-initializing the hardware (in
214essence, SID acts as an index in the session cache of the driver).
215.Pp
216.Fn crypto_freesession
217is called with the SID returned by
218.Fn crypto_newsession
219to disestablish the session.
220.Pp
221.Fn crypto_dispatch
222is called to process a request.
223The various fields in the
224.Fa cryptop
225structure are:
226.Bl -tag -width crp_alloctype
227.It Fa crp_sid
228Contains the SID.
229.It Fa crp_ilen
230Indicates the total length in bytes of the buffer to be processed.
231.It Fa crp_olen
232On return, contains the total length of the result.
233For symmetric crypto operations, this will be the same as the input length.
234.It Fa crp_alloctype
235Indicates the type of buffer, as used in the kernel
236.Xr malloc 9
237routine.
238This will be used if the framework needs to allocate a new
239buffer for the result (or for re-formatting the input).
240.It Fa crp_callback
241This routine is invoked upon completion of the request, whether
242successful or not.
243It is invoked through the
244.Fn crypto_done
245routine.
246If the request was not successful, an error code is set in the
247.Fa crp_etype
248field.
249It is the responsibility of the callback routine to set the appropriate
250.Xr spl 9
251level.
252.It Fa crp_etype
253Contains the error type, if any errors were encountered, or zero if
254the request was successfully processed.
255If the
256.Er EAGAIN
257error code is returned, the SID has changed (and has been recorded in the
258.Fa crp_sid
259field).
260The consumer should record the new SID and use it in all subsequent requests.
261In this case, the request may be re-submitted immediately.
262This mechanism is used by the framework to perform
263session migration (move a session from one driver to another, because
264of availability, performance, or other considerations).
265.Pp
266Note that this field only makes sense when examined by
267the callback routine specified in
268.Fa crp_callback .
269Errors are returned to the invoker of
270.Fn crypto_process
271only when enough information is not present to call the callback
272routine (i.e., if the pointer passed is
273.Dv NULL
274or if no callback routine was specified).
275.It Fa crp_flags
276Is a bitmask of flags associated with this request.
277Currently defined flags are:
278.Bl -tag -width CRYPTO_F_IMBUF
279.It Dv CRYPTO_F_IMBUF
280The buffer pointed to by
281.Fa crp_buf
282is an mbuf chain.
283.El
284.Pp
285.It Fa crp_buf
286Points to the input buffer.
287On return (when the callback is invoked),
288it contains the result of the request.
289The input buffer may be an mbuf
290chain or a contiguous buffer (of a type identified by
291.Fa crp_alloctype ) ,
292depending on
293.Fa crp_flags .
294.It Fa crp_opaque
295This is passed through the crypto framework untouched and is
296intended for the invoking application's use.
297.It Fa crp_desc
298This is a linked list of descriptors.
299Each descriptor provides
300information about what type of cryptographic operation should be done
301on the input buffer.
302The various fields are:
303.Bl -tag -width=crd_inject
304.It Fa crd_skip
305The offset in the input buffer where processing should start.
306.It Fa crd_len
307How many bytes, after
308.Fa Fa crd_skip ,
309should be processed.
310.It Fa crd_inject
311Offset from the beginning of the buffer to insert any results.
312For encryption algorithms, this is where the initialization vector
313(IV) will be inserted when encrypting or where it can be found when
314decrypting (subject to
315.Fa Fa crd_flags ) .
316For MAC algorithms, this is where the result of the keyed hash will be
317inserted.
318.It Fa crd_flags
319The following flags are defined:
320.Bl -tag -width CRD_F_IV_EXPLICIT
321.It Dv CRD_F_ENCRYPT
322For encryption algorithms, this bit is set when encryption is required
323(when not set, decryption is performed).
324.It Dv CRD_F_IV_PRESENT
325For encryption algorithms, this bit is set when the IV already
326precedes the data, so the
327.Fa crd_inject
328value will be ignored and no IV will be written in the buffer.
329Otherwise, the IV used to encrypt the packet will be written
330at the location pointed to by
331.Fa crd_inject .
332The IV length is assumed to be equal to the blocksize of the
333encryption algorithm.
334Some applications that do special
335.Dq IV cooking ,
336such as the half-IV mode in
337.Xr ipsec 4 ,
338can use this flag to indicate that the IV should not be written on the packet.
339This flag is typically used in conjunction with the
340.Dv CRD_F_IV_EXPLICIT
341flag.
342.It Dv CRD_F_IV_EXPLICIT
343For encryption algorithms, this bit is set when the IV is explicitly
344provided by the consumer in the
345.Fa crd_iv
346fields.
347Otherwise, for encryption operations the IV is provided for by
348the driver used to perform the operation, whereas for decryption
349operations it is pointed to by the
350.Fa crd_inject
351field.
352This flag is typically used when the IV is calculated
353.Dq on the fly
354by the consumer, and does not precede the data (some
355.Xr ipsec 4
356configurations, and the encrypted swap are two such examples).
357.It Dv CRD_F_COMP
358For compression algorithms, this bit is set when compression is required (when
359not set, decompression is performed).
360.El
361.It Fa CRD_INI
362This
363.Fa cryptoini
364structure will not be modified by the framework or the device drivers.
365Since this information accompanies every cryptographic
366operation request, drivers may re-initialize state on-demand
367(typically an expensive operation).
368Furthermore, the cryptographic
369framework may re-route requests as a result of full queues or hardware
370failure, as described above.
371.It Fa crd_next
372Point to the next descriptor.
373Linked operations are useful in protocols such as
374.Xr ipsec 4 ,
375where multiple cryptographic transforms may be applied on the same
376block of data.
377.El
378.El
379.Pp
380.Fn crypto_getreq
381allocates a
382.Fa cryptop
383structure with a linked list of as many
384.Fa cryptodesc
385structures as were specified in the argument passed to it.
386.Pp
387.Fn crypto_freereq
388deallocates a structure
389.Fa cryptop
390and any
391.Fa cryptodesc
392structures linked to it.
393Note that it is the responsibility of the
394callback routine to do the necessary cleanups associated with the
395opaque field in the
396.Fa cryptop
397structure.
398.Pp
399.Fn crypto_kdispatch
400is called to perform a keying operation.
401The various fields in the
402.Fa crytokop
403structure are:
404.Bl -tag -width crp_alloctype
405.It Fa krp_op
406Operation code, such as CRK_MOD_EXP.
407.It Fa krp_status
408Return code.
409This errno-style variable indicates whether lower level reasons
410for operation failure.
411.It Fa krp_iparams
412Number if input parameters to the specified operation.
413Note that each operation has a (typically hardwired) number of such parameters.
414.It Fa krp_oparams
415Number if output parameters from the specified operation.
416Note that each operation has a (typically hardwired) number of such parameters.
417.It Fa krp_kvp
418An array of kernel memory blocks containing the parameters.
419.It Fa krp_hid
420Identifier specifying which low-level driver is being used.
421.It Fa krp_callback
422Callback called on completion of a keying operation.
423.El
424.Sh DRIVER-SIDE API
425The
426.Fn crypto_get_driverid ,
427.Fn crypto_register ,
428.Fn crypto_kregister ,
429.Fn crypto_unregister ,
430and
431.Fn crypto_done
432routines are used by drivers that provide support for cryptographic
433primitives to register and unregister with the kernel crypto services
434framework.
435Drivers must first use the
436.Fn crypto_get_driverid
437function to acquire a driver identifier, specifying the
438.Fa cc_flags
439as an argument (normally 0, but software-only drivers should specify
440.Dv CRYPTOCAP_F_SOFTWARE Ns ).
441For each algorithm the driver supports, it must then call
442.Fn crypto_register .
443The first argument is the driver identifier.
444The second argument is an array of
445.Dv CRYPTO_ALGORITHM_MAX + 1
446elements, indicating which algorithms are supported.
447The last three arguments are pointers to three
448driver-provided functions that the framework may call to establish new
449cryptographic context with the driver, free already established
450context, and ask for a request to be processed (encrypt, decrypt,
451etc.)
452.Fn crypto_unregister
453is called by drivers that wish to withdraw support for an algorithm.
454The two arguments are the driver and algorithm identifiers, respectively.
455Typically, drivers for
456.Xr pcmcia 4
457crypto cards that are being ejected will invoke this routine for all
458algorithms supported by the card.
459If called with
460.Dv CRYPTO_ALGORITHM_ALL ,
461all algorithms registered for a driver will be unregistered in one go
462and the driver will be disabled (no new sessions will be allocated on
463that driver, and any existing sessions will be migrated to other
464drivers).
465The same will be done if all algorithms associated with a driver are
466unregistered one by one.
467.Pp
468The calling convention for the three driver-supplied routines is:
469.Bd -literal
470int (*newsession) (u_int32_t *, struct cryptoini *);
471int (*freesession) (u_int64_t);
472int (*process) (struct cryptop *);
473int (*kprocess) (struct cryptkop *);
474.Ed
475.Pp
476On invocation, the first argument to
477.Fn newsession
478contains the driver identifier obtained via
479.Fn crypto_get_driverid .
480On successfully returning, it should contain a driver-specific session
481identifier.
482The second argument is identical to that of
483.Fn crypto_newsession .
484.Pp
485The
486.Fn freesession
487routine takes as argument the SID (which is the concatenation of the
488driver identifier and the driver-specific session identifier).
489It should clear any context associated with the session (clear hardware
490registers, memory, etc.).
491.Pp
492The
493.Fn process
494routine is invoked with a request to perform crypto processing.
495This routine must not block, but should queue the request and return
496immediately.
497Upon processing the request, the callback routine should be invoked.
498In case of error, the error indication must be placed in the
499.Fa crp_etype
500field of the
501.Fa cryptop
502structure.
503When the request is completed, or an error is detected, the
504.Fn process
505routine should invoked
506.Fn crypto_done .
507Session migration may be performed, as mentioned previously.
508.Pp
509The
510.Fn kprocess
511routine is invoked with a request to perform crypto key processing.
512This routine must not block, but should queue the request and return
513immediately.
514Upon processing the request, the callback routine should be invoked.
515In case of error, the error indication must be placed in the
516.Fa krp_status
517field of the
518.Fa cryptkop
519structure.
520When the request is completed, or an error is detected, the
521.Fn kprocess
522routine should invoked
523.Fn crypto_kdone .
524.Sh RETURN VALUES
525.Fn crypto_register ,
526.Fn crypto_kregister ,
527.Fn crypto_unregister ,
528.Fn crypto_newsession ,
529and
530.Fn crypto_freesession
531return 0 on success, or an error code on failure.
532.Fn crypto_get_driverid
533returns a non-negative value on error, and \-1 on failure.
534.Fn crypto_getreq
535returns a pointer to a
536.Fa cryptop
537structure and
538.Dv NULL
539on failure.
540.Fn crypto_dispatch
541returns
542.Er EINVAL
543is its argument or the callback function was
544.Dv NULL ,
545and 0 otherwise.
546The callback is provided with an error code in case of failure, in the
547.Fa crp_etype
548field.
549.Sh FILES
550.Bl -tag -width sys/crypto/crypto.c
551.It Pa sys/crypto/crypto.c
552most of the framework code
553.El
554.Sh SEE ALSO
555.Xr ipsec 4 ,
556.Xr pcmcia 4 ,
557.Xr malloc 9 ,
558.Xr tsleep 9
559.Sh HISTORY
560The cryptographic framework first appeared in
561.Ox 2.7
562and was written by Angelos D. Keromytis <angelos@openbsd.org>.
563.Sh BUGS
564The framework currently assumes that all the algorithms in a
565.Fn crypto_newsession
566operation must be available by the same driver.
567If that's not the case, session initialization will fail.
568.Pp
569The framework also needs a mechanism for determining which driver is
570best for a specific set of algorithms associated with a session.
571Some type of benchmarking is in order here.
572.Pp
573Multiple instances of the same algorithm in the same session are not
574supported.
575Note that 3DES is considered one algorithm (and not three
576instances of DES).
577Thus, 3DES and DES could be mixed in the same request.
578.Pp
579A queue for completed operations should be implemented and processed
580at some software
581.Xr spl 9
582level, to avoid overall system latency issues, and potential kernel
583stack exhaustion while processing a callback.
584.Pp
585When SMP time comes, we will support use of a second processor (or
586more) as a crypto device (this is actually AMP, but we need the same
587basic support).
588