1.\" $OpenBSD: crypto.9,v 1.19 2002/07/16 06:31:57 angelos Exp $ 2.\" 3.\" The author of this manual 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. 11.\" 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 16.\" PURPOSE. 17.\" 18.\" $FreeBSD: src/share/man/man9/crypto.9,v 1.14 2007/09/19 16:28:46 brueffer Exp $ 19.\" 20.Dd August 21, 2010 21.Dt CRYPTO 9 22.Os 23.Sh NAME 24.Nm crypto 25.Nd API for cryptographic services in the kernel 26.Sh SYNOPSIS 27.In opencrypto/cryptodev.h 28.Ft int32_t 29.Fn crypto_get_driverid "device_t dev" "int flags" 30.Ft int 31.Fn crypto_find_driver "const char *match" 32.Ft device_t 33.Fn crypto_find_device_byhid "int hid" 34.Ft int 35.Fn crypto_getcaps "int hid" 36.Ft int 37.Fn crypto_register "u_int32_t driverid" "int alg" "u_int16_t maxoplen" "u_int32_t flags" 38.Ft int 39.Fn crypto_kregister "u_int32_t driverid" "int kalg" "u_int32_t flags" 40.Ft int 41.Fn crypto_unregister "u_int32_t driverid" "int alg" 42.Ft int 43.Fn crypto_unregister_all "u_int32_t driverid" 44.Ft void 45.Fn crypto_done "struct cryptop *crp" 46.Ft void 47.Fn crypto_kdone "struct cryptkop *krp" 48.Ft int 49.Fn crypto_newsession "u_int64_t *sid" "struct cryptoini *cri" "int crid" 50.Ft int 51.Fn crypto_freesession "u_int64_t sid" 52.Ft int 53.Fn crypto_dispatch "struct cryptop *crp" 54.Ft int 55.Fn crypto_kdispatch "struct cryptkop *krp" 56.Ft int 57.Fn crypto_unblock "u_int32_t driverid" "int what" 58.Ft "struct cryptop *" 59.Fn crypto_getreq "int num" 60.Ft void 61.Fn crypto_freereq "struct cryptop *crp" 62.Bd -literal 63#define CRYPTO_SYMQ 0x1 64#define CRYPTO_ASYMQ 0x2 65 66#define EALG_MAX_BLOCK_LEN 16 67 68struct cryptoini { 69 int cri_alg; 70 int cri_klen; 71 int cri_mlen; 72 caddr_t cri_key; 73 u_int8_t cri_iv[EALG_MAX_BLOCK_LEN]; 74 struct cryptoini *cri_next; 75}; 76 77struct cryptodesc { 78 int crd_skip; 79 int crd_len; 80 int crd_inject; 81 int crd_flags; 82 struct cryptoini CRD_INI; 83#define crd_iv CRD_INI.cri_iv 84#define crd_key CRD_INI.cri_key 85#define crd_alg CRD_INI.cri_alg 86#define crd_klen CRD_INI.cri_klen 87 struct cryptodesc *crd_next; 88}; 89 90struct cryptop { 91 TAILQ_ENTRY(cryptop) crp_next; 92 u_int64_t crp_sid; 93 int crp_ilen; 94 int crp_olen; 95 int crp_etype; 96 int crp_flags; 97 caddr_t crp_buf; 98 caddr_t crp_opaque; 99 struct cryptodesc *crp_desc; 100 int (*crp_callback) (struct cryptop *); 101 caddr_t crp_mac; 102}; 103 104struct crparam { 105 caddr_t crp_p; 106 u_int crp_nbits; 107}; 108 109#define CRK_MAXPARAM 8 110 111struct cryptkop { 112 TAILQ_ENTRY(cryptkop) krp_next; 113 u_int krp_op; /* ie. CRK_MOD_EXP or other */ 114 u_int krp_status; /* return status */ 115 u_short krp_iparams; /* # of input parameters */ 116 u_short krp_oparams; /* # of output parameters */ 117 u_int32_t krp_hid; 118 struct crparam krp_param[CRK_MAXPARAM]; 119 int (*krp_callback)(struct cryptkop *); 120}; 121.Ed 122.Sh DESCRIPTION 123.Nm 124is a framework for drivers of cryptographic hardware to register with 125the kernel so 126.Dq consumers 127(other kernel subsystems, and 128users through the 129.Pa /dev/crypto 130device) are able to make use of it. 131Drivers register with the framework the algorithms they support, 132and provide entry points (functions) the framework may call to 133establish, use, and tear down sessions. 134Sessions are used to cache cryptographic information in a particular driver 135(or associated hardware), so initialization is not needed with every request. 136Consumers of cryptographic services pass a set of 137descriptors that instruct the framework (and the drivers registered 138with it) of the operations that should be applied on the data (more 139than one cryptographic operation can be requested). 140.Pp 141Keying operations are supported as well. 142Unlike the symmetric operators described above, 143these sessionless commands perform mathematical operations using 144input and output parameters. 145.Pp 146Since the consumers may not be associated with a process, drivers may 147not 148.Xr sleep 9 . 149The same holds for the framework. 150Thus, a callback mechanism is used 151to notify a consumer that a request has been completed (the 152callback is specified by the consumer on an per-request basis). 153The callback is invoked by the framework whether the request was 154successfully completed or not. 155An error indication is provided in the latter case. 156A specific error code, 157.Er EAGAIN , 158is used to indicate that a session number has changed and that the 159request may be re-submitted immediately with the new session number. 160Errors are only returned to the invoking function if not 161enough information to call the callback is available (meaning, there 162was a fatal error in verifying the arguments). 163For session initialization and teardown there is no callback mechanism used. 164.Pp 165The 166.Fn crypto_newsession 167routine is called by consumers of cryptographic services (such as the 168.Xr ipsec 4 169stack) that wish to establish a new session with the framework. 170On success, the first argument will contain the Session Identifier (SID). 171The second argument contains all the necessary information for 172the driver to establish the session. 173The third argument indicates whether a 174hardware driver (1) should be used or not (0). 175The various fields in the 176.Vt cryptoini 177structure are: 178.Bl -tag -width ".Va cri_next" 179.It Va cri_alg 180Contains an algorithm identifier. 181Currently supported algorithms are: 182.Pp 183.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact 184.It Dv CRYPTO_AES_CBC 185.It Dv CRYPTO_AES_XTS 186.It Dv CRYPTO_AES_CTR 187.It Dv CRYPTO_ARC4 188.It Dv CRYPTO_BLF_CBC 189.It Dv CRYPTO_CAMELLIA_CBC 190.It Dv CRYPTO_CAST_CBC 191.It Dv CRYPTO_DES_CBC 192.It Dv CRYPTO_3DES_CBC 193.It Dv CRYPTO_SKIPJACK_CBC 194.It Dv CRYPTO_MD5 195.It Dv CRYPTO_MD5_HMAC 196.It Dv CRYPTO_MD5_KPDK 197.It Dv CRYPTO_RIPEMD160_HMAC 198.It Dv CRYPTO_SHA1 199.It Dv CRYPTO_SHA1_HMAC 200.It Dv CRYPTO_SHA1_KPDK 201.It Dv CRYPTO_SHA2_256_HMAC 202.It Dv CRYPTO_SHA2_384_HMAC 203.It Dv CRYPTO_SHA2_512_HMAC 204.It Dv CRYPTO_NULL_HMAC 205.It Dv CRYPTO_NULL_CBC 206.El 207.It Va cri_klen 208Specifies the length of the key in bits, for variable-size key 209algorithms. 210.It Va cri_mlen 211Specifies how many bytes from the calculated hash should be copied back. 2120 means entire hash. 213.It Va cri_key 214Contains the key to be used with the algorithm. 215.It Va cri_iv 216Contains an explicit initialization vector (IV), if it does not prefix 217the data. 218This field is ignored during initialization. 219If no IV is explicitly passed (see below on details), a random IV is used 220by the device driver processing the request. 221.It Va cri_next 222Contains a pointer to another 223.Vt cryptoini 224structure. 225Multiple such structures may be linked to establish multi-algorithm sessions 226.Xr ( ipsec 4 227is an example consumer of such a feature). 228.El 229.Pp 230The 231.Vt cryptoini 232structure and its contents will not be modified by the framework (or 233the drivers used). 234Subsequent requests for processing that use the 235SID returned will avoid the cost of re-initializing the hardware (in 236essence, SID acts as an index in the session cache of the driver). 237.Pp 238.Fn crypto_freesession 239is called with the SID returned by 240.Fn crypto_newsession 241to disestablish the session. 242.Pp 243.Fn crypto_dispatch 244is called to process a request. 245The various fields in the 246.Vt cryptop 247structure are: 248.Bl -tag -width ".Va crp_callback" 249.It Va crp_sid 250Contains the SID. 251.It Va crp_ilen 252Indicates the total length in bytes of the buffer to be processed. 253.It Va crp_olen 254On return, contains the total length of the result. 255For symmetric crypto operations, this will be the same as the input length. 256This will be used if the framework needs to allocate a new 257buffer for the result (or for re-formatting the input). 258.It Va crp_callback 259This routine is invoked upon completion of the request, whether 260successful or not. 261It is invoked through the 262.Fn crypto_done 263routine. 264If the request was not successful, an error code is set in the 265.Va crp_etype 266field. 267It is the responsibility of the callback routine to enter a critical 268section. 269.It Va crp_etype 270Contains the error type, if any errors were encountered, or zero if 271the request was successfully processed. 272If the 273.Er EAGAIN 274error code is returned, the SID has changed (and has been recorded in the 275.Va crp_sid 276field). 277The consumer should record the new SID and use it in all subsequent requests. 278In this case, the request may be re-submitted immediately. 279This mechanism is used by the framework to perform 280session migration (move a session from one driver to another, because 281of availability, performance, or other considerations). 282.Pp 283Note that this field only makes sense when examined by 284the callback routine specified in 285.Va crp_callback . 286Errors are returned to the invoker of 287.Fn crypto_process 288only when enough information is not present to call the callback 289routine (i.e., if the pointer passed is 290.Dv NULL 291or if no callback routine was specified). 292.It Va crp_flags 293Is a bitmask of flags associated with this request. 294Currently defined flags are: 295.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC" 296.It Dv CRYPTO_F_IMBUF 297The buffer pointed to by 298.Va crp_buf 299is an mbuf chain. 300.It Dv CRYPTO_F_IOV 301The buffer pointed to by 302.Va crp_buf 303is an 304.Vt uio 305structure. 306.It Dv CRYPTO_F_REL 307Must return data in the same place. 308.It Dv CRYPTO_F_BATCH 309Batch operation if possible. 310.It Dv CRYPTO_F_CBIMM 311Do callback immediately instead of doing it from a dedicated kernel thread. 312.It Dv CRYPTO_F_DONE 313Operation completed. 314.It Dv CRYPTO_F_CBIFSYNC 315Do callback immediately if operation is synchronous. 316.El 317.It Va crp_buf 318Points to the input buffer. 319On return (when the callback is invoked), 320it contains the result of the request. 321The input buffer may be an mbuf 322chain or a contiguous buffer, 323depending on 324.Va crp_flags . 325.It Va crp_opaque 326This is passed through the crypto framework untouched and is 327intended for the invoking application's use. 328.It Va crp_desc 329This is a linked list of descriptors. 330Each descriptor provides 331information about what type of cryptographic operation should be done 332on the input buffer. 333The various fields are: 334.Bl -tag -width ".Va crd_inject" 335.It Va crd_iv 336The field where IV should be provided when the 337.Dv CRD_F_IV_EXPLICIT 338flag is given. 339.It Va crd_key 340When the 341.Dv CRD_F_KEY_EXPLICIT 342flag is given, the 343.Va crd_key 344points to a buffer with encryption or authentication key. 345.It Va crd_alg 346An algorithm to use. 347Must be the same as the one given at newsession time. 348.It Va crd_klen 349The 350.Va crd_key 351key length. 352.It Va crd_skip 353The offset in the input buffer where processing should start. 354.It Va crd_len 355How many bytes, after 356.Va crd_skip , 357should be processed. 358.It Va crd_inject 359Offset from the beginning of the buffer to insert any results. 360For encryption algorithms, this is where the initialization vector 361(IV) will be inserted when encrypting or where it can be found when 362decrypting (subject to 363.Va crd_flags ) . 364For MAC algorithms, this is where the result of the keyed hash will be 365inserted. 366.It Va crd_flags 367The following flags are defined: 368.Bl -tag -width 3n 369.It Dv CRD_F_ENCRYPT 370For encryption algorithms, this bit is set when encryption is required 371(when not set, decryption is performed). 372.It Dv CRD_F_IV_PRESENT 373For encryption algorithms, this bit is set when the IV already 374precedes the data, so the 375.Va crd_inject 376value will be ignored and no IV will be written in the buffer. 377Otherwise, the IV used to encrypt the packet will be written 378at the location pointed to by 379.Va crd_inject . 380The IV length is assumed to be equal to the blocksize of the 381encryption algorithm. 382Some applications that do special 383.Dq "IV cooking" , 384such as the half-IV mode in 385.Xr ipsec 4 , 386can use this flag to indicate that the IV should not be written on the packet. 387This flag is typically used in conjunction with the 388.Dv CRD_F_IV_EXPLICIT 389flag. 390.It Dv CRD_F_IV_EXPLICIT 391For encryption algorithms, this bit is set when the IV is explicitly 392provided by the consumer in the 393.Va crd_iv 394field. 395Otherwise, for encryption operations the IV is provided for by 396the driver used to perform the operation, whereas for decryption 397operations it is pointed to by the 398.Va crd_inject 399field. 400This flag is typically used when the IV is calculated 401.Dq "on the fly" 402by the consumer, and does not precede the data (some 403.Xr ipsec 4 404configurations, and the encrypted swap are two such examples). 405.It Dv CRD_F_KEY_EXPLICIT 406For encryption and authentication (MAC) algorithms, this bit is set when the key 407is explicitly provided by the consumer in the 408.Va crd_key 409field for the given operation. 410Otherwise, the key is taken at newsession time from the 411.Va cri_key 412field. 413.It Dv CRD_F_COMP 414For compression algorithms, this bit is set when compression is required (when 415not set, decompression is performed). 416.El 417.It Va CRD_INI 418This 419.Vt cryptoini 420structure will not be modified by the framework or the device drivers. 421Since this information accompanies every cryptographic 422operation request, drivers may re-initialize state on-demand 423(typically an expensive operation). 424Furthermore, the cryptographic 425framework may re-route requests as a result of full queues or hardware 426failure, as described above. 427.It Va crd_next 428Point to the next descriptor. 429Linked operations are useful in protocols such as 430.Xr ipsec 4 , 431where multiple cryptographic transforms may be applied on the same 432block of data. 433.El 434.El 435.Pp 436.Fn crypto_getreq 437allocates a 438.Vt cryptop 439structure with a linked list of as many 440.Vt cryptodesc 441structures as were specified in the argument passed to it. 442.Pp 443.Fn crypto_freereq 444deallocates a structure 445.Vt cryptop 446and any 447.Vt cryptodesc 448structures linked to it. 449Note that it is the responsibility of the 450callback routine to do the necessary cleanups associated with the 451opaque field in the 452.Vt cryptop 453structure. 454.Pp 455.Fn crypto_kdispatch 456is called to perform a keying operation. 457The various fields in the 458.Vt cryptkop 459structure are: 460.Bl -tag -width ".Va krp_callback" 461.It Va krp_op 462Operation code, such as 463.Dv CRK_MOD_EXP . 464.It Va krp_status 465Return code. 466This 467.Va errno Ns -style 468variable indicates whether lower level reasons 469for operation failure. 470.It Va krp_iparams 471Number if input parameters to the specified operation. 472Note that each operation has a (typically hardwired) number of such parameters. 473.It Va krp_oparams 474Number if output parameters from the specified operation. 475Note that each operation has a (typically hardwired) number of such parameters. 476.It Va krp_kvp 477An array of kernel memory blocks containing the parameters. 478.It Va krp_hid 479Identifier specifying which low-level driver is being used. 480.It Va krp_callback 481Callback called on completion of a keying operation. 482.El 483.Sh DRIVER-SIDE API 484The 485.Fn crypto_get_driverid , 486.Fn crypto_register , 487.Fn crypto_kregister , 488.Fn crypto_unregister , 489.Fn crypto_unblock , 490and 491.Fn crypto_done 492routines are used by drivers that provide support for cryptographic 493primitives to register and unregister with the kernel crypto services 494framework. 495Drivers must first use the 496.Fn crypto_get_driverid 497function to acquire a driver identifier, specifying the 498.Fa cc_flags 499as an argument (normally 0, but software-only drivers should specify 500.Dv CRYPTOCAP_F_SOFTWARE ) . 501For each algorithm the driver supports, it must then call 502.Fn crypto_register . 503The first two arguments are the driver and algorithm identifiers. 504The next two arguments specify the largest possible operator length (in bits, 505important for public key operations) and flags for this algorithm. 506The last four arguments must be provided in the first call to 507.Fn crypto_register 508and are ignored in all subsequent calls. 509They are pointers to three 510driver-provided functions that the framework may call to establish new 511cryptographic context with the driver, free already established 512context, and ask for a request to be processed (encrypt, decrypt, 513etc.); and an opaque parameter to pass when calling each of these routines. 514.Fn crypto_unregister 515is called by drivers that wish to withdraw support for an algorithm. 516The two arguments are the driver and algorithm identifiers, respectively. 517Typically, drivers for 518PCMCIA 519crypto cards that are being ejected will invoke this routine for all 520algorithms supported by the card. 521.Fn crypto_unregister_all 522will unregister all algorithms registered by a driver 523and the driver will be disabled (no new sessions will be allocated on 524that driver, and any existing sessions will be migrated to other 525drivers). 526The same will be done if all algorithms associated with a driver are 527unregistered one by one. 528.Pp 529The calling convention for the three driver-supplied routines is: 530.Pp 531.Bl -item -compact 532.It 533.Ft int 534.Fn \*[lp]*newsession\*[rp] "void *" "u_int32_t *" "struct cryptoini *" ; 535.It 536.Ft int 537.Fn \*[lp]*freesession\*[rp] "void *" "u_int64_t" ; 538.It 539.Ft int 540.Fn \*[lp]*process\*[rp] "void *" "struct cryptop *" ; 541.It 542.Ft int 543.Fn \*[lp]*kprocess\*[rp] "void *" "struct cryptkop *" ; 544.El 545.Pp 546On invocation, the first argument to 547all routines is an opaque data value supplied when the algorithm 548is registered with 549.Fn crypto_register . 550The second argument to 551.Fn newsession 552contains the driver identifier obtained via 553.Fn crypto_get_driverid . 554On successful return, it should contain a driver-specific session 555identifier. 556The third argument is identical to that of 557.Fn crypto_newsession . 558.Pp 559The 560.Fn freesession 561routine takes as arguments the opaque data value and the SID 562(which is the concatenation of the 563driver identifier and the driver-specific session identifier). 564It should clear any context associated with the session (clear hardware 565registers, memory, etc.). 566.Pp 567The 568.Fn process 569routine is invoked with a request to perform crypto processing. 570This routine must not block, but should queue the request and return 571immediately. 572Upon processing the request, the callback routine should be invoked. 573In case of an unrecoverable error, the error indication must be placed in the 574.Va crp_etype 575field of the 576.Vt cryptop 577structure. 578When the request is completed, or an error is detected, the 579.Fn process 580routine should invoke 581.Fn crypto_done . 582Session migration may be performed, as mentioned previously. 583.Pp 584In case of a temporary resource exhaustion, the 585.Fn process 586routine may return 587.Er ERESTART 588in which case the crypto services will requeue the request, mark the driver 589as 590.Dq blocked , 591and stop submitting requests for processing. 592The driver is then responsible for notifying the crypto services 593when it is again able to process requests through the 594.Fn crypto_unblock 595routine. 596This simple flow control mechanism should only be used for short-lived 597resource exhaustion as it causes operations to be queued in the crypto 598layer. 599Doing so is preferable to returning an error in such cases as 600it can cause network protocols to degrade performance by treating the 601failure much like a lost packet. 602.Pp 603The 604.Fn kprocess 605routine is invoked with a request to perform crypto key processing. 606This routine must not block, but should queue the request and return 607immediately. 608Upon processing the request, the callback routine should be invoked. 609In case of an unrecoverable error, the error indication must be placed in the 610.Va krp_status 611field of the 612.Vt cryptkop 613structure. 614When the request is completed, or an error is detected, the 615.Fn kprocess 616routine should invoked 617.Fn crypto_kdone . 618.Sh RETURN VALUES 619.Fn crypto_register , 620.Fn crypto_kregister , 621.Fn crypto_unregister , 622.Fn crypto_newsession , 623.Fn crypto_freesession , 624and 625.Fn crypto_unblock 626return 0 on success, or an error code on failure. 627.Fn crypto_get_driverid 628returns a non-negative value on error, and \-1 on failure. 629.Fn crypto_getreq 630returns a pointer to a 631.Vt cryptop 632structure and 633.Dv NULL 634on failure. 635.Fn crypto_dispatch 636returns 637.Er EINVAL 638if its argument or the callback function was 639.Dv NULL , 640and 0 otherwise. 641The callback is provided with an error code in case of failure, in the 642.Va crp_etype 643field. 644.Sh FILES 645.Bl -tag -width ".Pa sys/opencrypto/crypto.c" 646.It Pa sys/opencrypto/crypto.c 647most of the framework code 648.El 649.Sh SEE ALSO 650.Xr ipsec 4 , 651.Xr kmalloc 9 , 652.Xr sleep 9 653.Sh HISTORY 654The cryptographic framework first appeared in 655.Ox 2.7 656and was written by 657.An "Angelos D. Keromytis" Aq angelos@openbsd.org . 658.Sh BUGS 659The framework currently assumes that all the algorithms in a 660.Fn crypto_newsession 661operation must be available by the same driver. 662If that is not the case, session initialization will fail. 663.Pp 664The framework also needs a mechanism for determining which driver is 665best for a specific set of algorithms associated with a session. 666Some type of benchmarking is in order here. 667.Pp 668Multiple instances of the same algorithm in the same session are not 669supported. 670Note that 3DES is considered one algorithm (and not three 671instances of DES). 672Thus, 3DES and DES could be mixed in the same request. 673