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.\" $FreeBSD$ 19.\" 20.Dd September 19, 2007 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 u_int8_t 30.Ft int 31.Fn crypto_register u_int32_t int u_int16_t u_int32_t "int \*[lp]*\*[rp]\*[lp]void *, u_int32_t *, struct cryptoini *\*[rp]" "int \*[lp]*\*[rp]\*[lp]void *, u_int64_t\*[rp]" "int \*[lp]*\*[rp]\*[lp]void *, struct cryptop *\*[rp]" "void *" 32.Ft int 33.Fn crypto_kregister u_int32_t int u_int32_t "int \*[lp]*\*[rp]\*[lp]void *, struct cryptkop *\*[rp]" "void *" 34.Ft int 35.Fn crypto_unregister u_int32_t int 36.Ft int 37.Fn crypto_unregister_all u_int32_t 38.Ft void 39.Fn crypto_done "struct cryptop *" 40.Ft void 41.Fn crypto_kdone "struct cryptkop *" 42.Ft int 43.Fn crypto_newsession "u_int64_t *" "struct cryptoini *" int 44.Ft int 45.Fn crypto_freesession u_int64_t 46.Ft int 47.Fn crypto_dispatch "struct cryptop *" 48.Ft int 49.Fn crypto_kdispatch "struct cryptkop *" 50.Ft int 51.Fn crypto_unblock u_int32_t int 52.Ft "struct cryptop *" 53.Fn crypto_getreq int 54.Ft void 55.Fn crypto_freereq void 56.Bd -literal 57#define CRYPTO_SYMQ 0x1 58#define CRYPTO_ASYMQ 0x2 59 60#define EALG_MAX_BLOCK_LEN 16 61 62struct cryptoini { 63 int cri_alg; 64 int cri_klen; 65 int cri_mlen; 66 caddr_t cri_key; 67 u_int8_t cri_iv[EALG_MAX_BLOCK_LEN]; 68 struct cryptoini *cri_next; 69}; 70 71struct cryptodesc { 72 int crd_skip; 73 int crd_len; 74 int crd_inject; 75 int crd_flags; 76 struct cryptoini CRD_INI; 77#define crd_iv CRD_INI.cri_iv 78#define crd_key CRD_INI.cri_key 79#define crd_alg CRD_INI.cri_alg 80#define crd_klen CRD_INI.cri_klen 81 struct cryptodesc *crd_next; 82}; 83 84struct cryptop { 85 TAILQ_ENTRY(cryptop) crp_next; 86 u_int64_t crp_sid; 87 int crp_ilen; 88 int crp_olen; 89 int crp_etype; 90 int crp_flags; 91 caddr_t crp_buf; 92 caddr_t crp_opaque; 93 struct cryptodesc *crp_desc; 94 int (*crp_callback) (struct cryptop *); 95 caddr_t crp_mac; 96}; 97 98struct crparam { 99 caddr_t crp_p; 100 u_int crp_nbits; 101}; 102 103#define CRK_MAXPARAM 8 104 105struct cryptkop { 106 TAILQ_ENTRY(cryptkop) krp_next; 107 u_int krp_op; /* ie. CRK_MOD_EXP or other */ 108 u_int krp_status; /* return status */ 109 u_short krp_iparams; /* # of input parameters */ 110 u_short krp_oparams; /* # of output parameters */ 111 u_int32_t krp_hid; 112 struct crparam krp_param[CRK_MAXPARAM]; 113 int (*krp_callback)(struct cryptkop *); 114}; 115.Ed 116.Sh DESCRIPTION 117.Nm 118is a framework for drivers of cryptographic hardware to register with 119the kernel so 120.Dq consumers 121(other kernel subsystems, and 122users through the 123.Pa /dev/crypto 124device) are able to make use of it. 125Drivers register with the framework the algorithms they support, 126and provide entry points (functions) the framework may call to 127establish, use, and tear down sessions. 128Sessions are used to cache cryptographic information in a particular driver 129(or associated hardware), so initialization is not needed with every request. 130Consumers of cryptographic services pass a set of 131descriptors that instruct the framework (and the drivers registered 132with it) of the operations that should be applied on the data (more 133than one cryptographic operation can be requested). 134.Pp 135Keying operations are supported as well. 136Unlike the symmetric operators described above, 137these sessionless commands perform mathematical operations using 138input and output parameters. 139.Pp 140Since the consumers may not be associated with a process, drivers may 141not 142.Xr sleep 9 . 143The same holds for the framework. 144Thus, a callback mechanism is used 145to notify a consumer that a request has been completed (the 146callback is specified by the consumer on a per-request basis). 147The callback is invoked by the framework whether the request was 148successfully completed or not. 149An error indication is provided in the latter case. 150A specific error code, 151.Er EAGAIN , 152is used to indicate that a session number has changed and that the 153request may be re-submitted immediately with the new session number. 154Errors are only returned to the invoking function if not 155enough information to call the callback is available (meaning, there 156was a fatal error in verifying the arguments). 157For session initialization and teardown there is no callback mechanism used. 158.Pp 159The 160.Fn crypto_newsession 161routine is called by consumers of cryptographic services (such as the 162.Xr ipsec 4 163stack) that wish to establish a new session with the framework. 164On success, the first argument will contain the Session Identifier (SID). 165The second argument contains all the necessary information for 166the driver to establish the session. 167The third argument indicates whether a 168hardware driver (1) should be used or not (0). 169The various fields in the 170.Vt cryptoini 171structure are: 172.Bl -tag -width ".Va cri_next" 173.It Va cri_alg 174Contains an algorithm identifier. 175Currently supported algorithms are: 176.Pp 177.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact 178.It Dv CRYPTO_AES_CBC 179.It Dv CRYPTO_ARC4 180.It Dv CRYPTO_BLF_CBC 181.It Dv CRYPTO_CAMELLIA_CBC 182.It Dv CRYPTO_CAST_CBC 183.It Dv CRYPTO_DES_CBC 184.It Dv CRYPTO_3DES_CBC 185.It Dv CRYPTO_SKIPJACK_CBC 186.It Dv CRYPTO_MD5 187.It Dv CRYPTO_MD5_HMAC 188.It Dv CRYPTO_MD5_KPDK 189.It Dv CRYPTO_RIPEMD160_HMAC 190.It Dv CRYPTO_SHA1 191.It Dv CRYPTO_SHA1_HMAC 192.It Dv CRYPTO_SHA1_KPDK 193.It Dv CRYPTO_SHA2_256_HMAC 194.It Dv CRYPTO_SHA2_384_HMAC 195.It Dv CRYPTO_SHA2_512_HMAC 196.It Dv CRYPTO_NULL_HMAC 197.It Dv CRYPTO_NULL_CBC 198.El 199.It Va cri_klen 200Specifies the length of the key in bits, for variable-size key 201algorithms. 202.It Va cri_mlen 203Specifies how many bytes from the calculated hash should be copied back. 2040 means entire hash. 205.It Va cri_key 206Contains the key to be used with the algorithm. 207.It Va cri_iv 208Contains an explicit initialization vector (IV), if it does not prefix 209the data. 210This field is ignored during initialization. 211If no IV is explicitly passed (see below on details), a random IV is used 212by the device driver processing the request. 213.It Va cri_next 214Contains a pointer to another 215.Vt cryptoini 216structure. 217Multiple such structures may be linked to establish multi-algorithm sessions 218.Xr ( ipsec 4 219is an example consumer of such a feature). 220.El 221.Pp 222The 223.Vt cryptoini 224structure and its contents will not be modified by the framework (or 225the drivers used). 226Subsequent requests for processing that use the 227SID returned will avoid the cost of re-initializing the hardware (in 228essence, SID acts as an index in the session cache of the driver). 229.Pp 230.Fn crypto_freesession 231is called with the SID returned by 232.Fn crypto_newsession 233to disestablish the session. 234.Pp 235.Fn crypto_dispatch 236is called to process a request. 237The various fields in the 238.Vt cryptop 239structure are: 240.Bl -tag -width ".Va crp_callback" 241.It Va crp_sid 242Contains the SID. 243.It Va crp_ilen 244Indicates the total length in bytes of the buffer to be processed. 245.It Va crp_olen 246On return, contains the total length of the result. 247For symmetric crypto operations, this will be the same as the input length. 248This will be used if the framework needs to allocate a new 249buffer for the result (or for re-formatting the input). 250.It Va crp_callback 251This routine is invoked upon completion of the request, whether 252successful or not. 253It is invoked through the 254.Fn crypto_done 255routine. 256If the request was not successful, an error code is set in the 257.Va crp_etype 258field. 259It is the responsibility of the callback routine to set the appropriate 260.Xr spl 9 261level. 262.It Va crp_etype 263Contains the error type, if any errors were encountered, or zero if 264the request was successfully processed. 265If the 266.Er EAGAIN 267error code is returned, the SID has changed (and has been recorded in the 268.Va crp_sid 269field). 270The consumer should record the new SID and use it in all subsequent requests. 271In this case, the request may be re-submitted immediately. 272This mechanism is used by the framework to perform 273session migration (move a session from one driver to another, because 274of availability, performance, or other considerations). 275.Pp 276Note that this field only makes sense when examined by 277the callback routine specified in 278.Va crp_callback . 279Errors are returned to the invoker of 280.Fn crypto_process 281only when enough information is not present to call the callback 282routine (i.e., if the pointer passed is 283.Dv NULL 284or if no callback routine was specified). 285.It Va crp_flags 286Is a bitmask of flags associated with this request. 287Currently defined flags are: 288.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC" 289.It Dv CRYPTO_F_IMBUF 290The buffer pointed to by 291.Va crp_buf 292is an mbuf chain. 293.It Dv CRYPTO_F_IOV 294The buffer pointed to by 295.Va crp_buf 296is an 297.Vt uio 298structure. 299.It Dv CRYPTO_F_REL 300Must return data in the same place. 301.It Dv CRYPTO_F_BATCH 302Batch operation if possible. 303.It Dv CRYPTO_F_CBIMM 304Do callback immediately instead of doing it from a dedicated kernel thread. 305.It Dv CRYPTO_F_DONE 306Operation completed. 307.It Dv CRYPTO_F_CBIFSYNC 308Do callback immediately if operation is synchronous. 309.El 310.It Va crp_buf 311Points to the input buffer. 312On return (when the callback is invoked), 313it contains the result of the request. 314The input buffer may be an mbuf 315chain or a contiguous buffer, 316depending on 317.Va crp_flags . 318.It Va crp_opaque 319This is passed through the crypto framework untouched and is 320intended for the invoking application's use. 321.It Va crp_desc 322This is a linked list of descriptors. 323Each descriptor provides 324information about what type of cryptographic operation should be done 325on the input buffer. 326The various fields are: 327.Bl -tag -width ".Va crd_inject" 328.It Va crd_iv 329The field where IV should be provided when the 330.Dv CRD_F_IV_EXPLICIT 331flag is given. 332.It Va crd_key 333When the 334.Dv CRD_F_KEY_EXPLICIT 335flag is given, the 336.Va crd_key 337points to a buffer with encryption or authentication key. 338.It Va crd_alg 339An algorithm to use. 340Must be the same as the one given at newsession time. 341.It Va crd_klen 342The 343.Va crd_key 344key length. 345.It Va crd_skip 346The offset in the input buffer where processing should start. 347.It Va crd_len 348How many bytes, after 349.Va crd_skip , 350should be processed. 351.It Va crd_inject 352Offset from the beginning of the buffer to insert any results. 353For encryption algorithms, this is where the initialization vector 354(IV) will be inserted when encrypting or where it can be found when 355decrypting (subject to 356.Va crd_flags ) . 357For MAC algorithms, this is where the result of the keyed hash will be 358inserted. 359.It Va crd_flags 360The following flags are defined: 361.Bl -tag -width 3n 362.It Dv CRD_F_ENCRYPT 363For encryption algorithms, this bit is set when encryption is required 364(when not set, decryption is performed). 365.It Dv CRD_F_IV_PRESENT 366For encryption algorithms, this bit is set when the IV already 367precedes the data, so the 368.Va crd_inject 369value will be ignored and no IV will be written in the buffer. 370Otherwise, the IV used to encrypt the packet will be written 371at the location pointed to by 372.Va crd_inject . 373The IV length is assumed to be equal to the blocksize of the 374encryption algorithm. 375Some applications that do special 376.Dq "IV cooking" , 377such as the half-IV mode in 378.Xr ipsec 4 , 379can use this flag to indicate that the IV should not be written on the packet. 380This flag is typically used in conjunction with the 381.Dv CRD_F_IV_EXPLICIT 382flag. 383.It Dv CRD_F_IV_EXPLICIT 384For encryption algorithms, this bit is set when the IV is explicitly 385provided by the consumer in the 386.Va crd_iv 387field. 388Otherwise, for encryption operations the IV is provided for by 389the driver used to perform the operation, whereas for decryption 390operations it is pointed to by the 391.Va crd_inject 392field. 393This flag is typically used when the IV is calculated 394.Dq "on the fly" 395by the consumer, and does not precede the data (some 396.Xr ipsec 4 397configurations, and the encrypted swap are two such examples). 398.It Dv CRD_F_KEY_EXPLICIT 399For encryption and authentication (MAC) algorithms, this bit is set when the key 400is explicitly provided by the consumer in the 401.Va crd_key 402field for the given operation. 403Otherwise, the key is taken at newsession time from the 404.Va cri_key 405field. 406.It Dv CRD_F_COMP 407For compression algorithms, this bit is set when compression is required (when 408not set, decompression is performed). 409.El 410.It Va CRD_INI 411This 412.Vt cryptoini 413structure will not be modified by the framework or the device drivers. 414Since this information accompanies every cryptographic 415operation request, drivers may re-initialize state on-demand 416(typically an expensive operation). 417Furthermore, the cryptographic 418framework may re-route requests as a result of full queues or hardware 419failure, as described above. 420.It Va crd_next 421Point to the next descriptor. 422Linked operations are useful in protocols such as 423.Xr ipsec 4 , 424where multiple cryptographic transforms may be applied on the same 425block of data. 426.El 427.El 428.Pp 429.Fn crypto_getreq 430allocates a 431.Vt cryptop 432structure with a linked list of as many 433.Vt cryptodesc 434structures as were specified in the argument passed to it. 435.Pp 436.Fn crypto_freereq 437deallocates a structure 438.Vt cryptop 439and any 440.Vt cryptodesc 441structures linked to it. 442Note that it is the responsibility of the 443callback routine to do the necessary cleanups associated with the 444opaque field in the 445.Vt cryptop 446structure. 447.Pp 448.Fn crypto_kdispatch 449is called to perform a keying operation. 450The various fields in the 451.Vt cryptkop 452structure are: 453.Bl -tag -width ".Va krp_callback' 454.It Va krp_op 455Operation code, such as 456.Dv CRK_MOD_EXP . 457.It Va krp_status 458Return code. 459This 460.Va errno Ns -style 461variable indicates whether lower level reasons 462for operation failure. 463.It Va krp_iparams 464Number if input parameters to the specified operation. 465Note that each operation has a (typically hardwired) number of such parameters. 466.It Va krp_oparams 467Number if output parameters from the specified operation. 468Note that each operation has a (typically hardwired) number of such parameters. 469.It Va krp_kvp 470An array of kernel memory blocks containing the parameters. 471.It Va krp_hid 472Identifier specifying which low-level driver is being used. 473.It Va krp_callback 474Callback called on completion of a keying operation. 475.El 476.Sh DRIVER-SIDE API 477The 478.Fn crypto_get_driverid , 479.Fn crypto_register , 480.Fn crypto_kregister , 481.Fn crypto_unregister , 482.Fn crypto_unblock , 483and 484.Fn crypto_done 485routines are used by drivers that provide support for cryptographic 486primitives to register and unregister with the kernel crypto services 487framework. 488Drivers must first use the 489.Fn crypto_get_driverid 490function to acquire a driver identifier, specifying the 491.Fa cc_flags 492as an argument (normally 0, but software-only drivers should specify 493.Dv CRYPTOCAP_F_SOFTWARE ) . 494For each algorithm the driver supports, it must then call 495.Fn crypto_register . 496The first two arguments are the driver and algorithm identifiers. 497The next two arguments specify the largest possible operator length (in bits, 498important for public key operations) and flags for this algorithm. 499The last four arguments must be provided in the first call to 500.Fn crypto_register 501and are ignored in all subsequent calls. 502They are pointers to three 503driver-provided functions that the framework may call to establish new 504cryptographic context with the driver, free already established 505context, and ask for a request to be processed (encrypt, decrypt, 506etc.); and an opaque parameter to pass when calling each of these routines. 507.Fn crypto_unregister 508is called by drivers that wish to withdraw support for an algorithm. 509The two arguments are the driver and algorithm identifiers, respectively. 510Typically, drivers for 511PCMCIA 512crypto cards that are being ejected will invoke this routine for all 513algorithms supported by the card. 514.Fn crypto_unregister_all 515will unregister all algorithms registered by a driver 516and the driver will be disabled (no new sessions will be allocated on 517that driver, and any existing sessions will be migrated to other 518drivers). 519The same will be done if all algorithms associated with a driver are 520unregistered one by one. 521.Pp 522The calling convention for the three driver-supplied routines is: 523.Pp 524.Bl -item -compact 525.It 526.Ft int 527.Fn \*[lp]*newsession\*[rp] "void *" "u_int32_t *" "struct cryptoini *" ; 528.It 529.Ft int 530.Fn \*[lp]*freesession\*[rp] "void *" "u_int64_t" ; 531.It 532.Ft int 533.Fn \*[lp]*process\*[rp] "void *" "struct cryptop *" ; 534.It 535.Ft int 536.Fn \*[lp]*kprocess\*[rp] "void *" "struct cryptkop *" ; 537.El 538.Pp 539On invocation, the first argument to 540all routines is an opaque data value supplied when the algorithm 541is registered with 542.Fn crypto_register . 543The second argument to 544.Fn newsession 545contains the driver identifier obtained via 546.Fn crypto_get_driverid . 547On successful return, it should contain a driver-specific session 548identifier. 549The third argument is identical to that of 550.Fn crypto_newsession . 551.Pp 552The 553.Fn freesession 554routine takes as arguments the opaque data value and the SID 555(which is the concatenation of the 556driver identifier and the driver-specific session identifier). 557It should clear any context associated with the session (clear hardware 558registers, memory, etc.). 559.Pp 560The 561.Fn process 562routine is invoked with a request to perform crypto processing. 563This routine must not block, but should queue the request and return 564immediately. 565Upon processing the request, the callback routine should be invoked. 566In case of an unrecoverable error, the error indication must be placed in the 567.Va crp_etype 568field of the 569.Vt cryptop 570structure. 571When the request is completed, or an error is detected, the 572.Fn process 573routine should invoke 574.Fn crypto_done . 575Session migration may be performed, as mentioned previously. 576.Pp 577In case of a temporary resource exhaustion, the 578.Fn process 579routine may return 580.Er ERESTART 581in which case the crypto services will requeue the request, mark the driver 582as 583.Dq blocked , 584and stop submitting requests for processing. 585The driver is then responsible for notifying the crypto services 586when it is again able to process requests through the 587.Fn crypto_unblock 588routine. 589This simple flow control mechanism should only be used for short-lived 590resource exhaustion as it causes operations to be queued in the crypto 591layer. 592Doing so is preferable to returning an error in such cases as 593it can cause network protocols to degrade performance by treating the 594failure much like a lost packet. 595.Pp 596The 597.Fn kprocess 598routine is invoked with a request to perform crypto key processing. 599This routine must not block, but should queue the request and return 600immediately. 601Upon processing the request, the callback routine should be invoked. 602In case of an unrecoverable error, the error indication must be placed in the 603.Va krp_status 604field of the 605.Vt cryptkop 606structure. 607When the request is completed, or an error is detected, the 608.Fn kprocess 609routine should invoked 610.Fn crypto_kdone . 611.Sh RETURN VALUES 612.Fn crypto_register , 613.Fn crypto_kregister , 614.Fn crypto_unregister , 615.Fn crypto_newsession , 616.Fn crypto_freesession , 617and 618.Fn crypto_unblock 619return 0 on success, or an error code on failure. 620.Fn crypto_get_driverid 621returns a non-negative value on error, and \-1 on failure. 622.Fn crypto_getreq 623returns a pointer to a 624.Vt cryptop 625structure and 626.Dv NULL 627on failure. 628.Fn crypto_dispatch 629returns 630.Er EINVAL 631if its argument or the callback function was 632.Dv NULL , 633and 0 otherwise. 634The callback is provided with an error code in case of failure, in the 635.Va crp_etype 636field. 637.Sh FILES 638.Bl -tag -width ".Pa sys/opencrypto/crypto.c" 639.It Pa sys/opencrypto/crypto.c 640most of the framework code 641.El 642.Sh SEE ALSO 643.Xr ipsec 4 , 644.Xr malloc 9 , 645.Xr sleep 9 646.Sh HISTORY 647The cryptographic framework first appeared in 648.Ox 2.7 649and was written by 650.An "Angelos D. Keromytis" Aq angelos@openbsd.org . 651.Sh BUGS 652The framework currently assumes that all the algorithms in a 653.Fn crypto_newsession 654operation must be available by the same driver. 655If that is not the case, session initialization will fail. 656.Pp 657The framework also needs a mechanism for determining which driver is 658best for a specific set of algorithms associated with a session. 659Some type of benchmarking is in order here. 660.Pp 661Multiple instances of the same algorithm in the same session are not 662supported. 663Note that 3DES is considered one algorithm (and not three 664instances of DES). 665Thus, 3DES and DES could be mixed in the same request. 666