1.\" $OpenBSD: crypto.9,v 1.19 2002/07/16 06:31:57 angelos 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. 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 October 14, 2002 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_rnd; 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 struct cryptodesc *crd_next; 78}; 79 80struct cryptop { 81 TAILQ_ENTRY(cryptop) crp_next; 82 u_int64_t crp_sid; 83 int crp_ilen; 84 int crp_olen; 85 int crp_etype; 86 int crp_flags; 87 caddr_t crp_buf; 88 caddr_t crp_opaque; 89 struct cryptodesc *crp_desc; 90 int (*crp_callback) (struct cryptop *); 91 caddr_t crp_mac; 92}; 93 94struct crparam { 95 caddr_t crp_p; 96 u_int crp_nbits; 97}; 98 99#define CRK_MAXPARAM 8 100 101struct cryptkop { 102 TAILQ_ENTRY(cryptkop) krp_next; 103 u_int krp_op; /* ie. CRK_MOD_EXP or other */ 104 u_int krp_status; /* return status */ 105 u_short krp_iparams; /* # of input parameters */ 106 u_short krp_oparams; /* # of output parameters */ 107 u_int32_t krp_hid; 108 struct crparam krp_param[CRK_MAXPARAM]; 109 int (*krp_callback)(struct cryptkop *); 110}; 111.Ed 112.Sh DESCRIPTION 113.Nm 114is a framework for drivers of cryptographic hardware to register with 115the kernel so 116.Dq consumers 117(other kernel subsystems, and 118users through the 119.Pa /dev/crypto 120device) are able to make use of it. 121Drivers register with the framework the algorithms they support, 122and provide entry points (functions) the framework may call to 123establish, use, and tear down sessions. 124Sessions are used to cache cryptographic information in a particular driver 125(or associated hardware), so initialization is not needed with every request. 126Consumers of cryptographic services pass a set of 127descriptors that instruct the framework (and the drivers registered 128with it) of the operations that should be applied on the data (more 129than one cryptographic operation can be requested). 130.Pp 131Keying operations are supported as well. 132Unlike the symmetric operators described above, 133these sessionless commands perform mathematical operations using 134input and output parameters. 135.Pp 136Since the consumers may not be associated with a process, drivers may 137not 138.Xr sleep 9 . 139The same holds for the framework. 140Thus, a callback mechanism is used 141to notify a consumer that a request has been completed (the 142callback is specified by the consumer on an per-request basis). 143The callback is invoked by the framework whether the request was 144successfully completed or not. 145An error indication is provided in the latter case. 146A specific error code, 147.Er EAGAIN , 148is used to indicate that a session number has changed and that the 149request may be re-submitted immediately with the new session number. 150Errors are only returned to the invoking function if not 151enough information to call the callback is available (meaning, there 152was a fatal error in verifying the arguments). 153For session initialization and teardown there is no callback mechanism used. 154.Pp 155The 156.Fn crypto_newsession 157routine is called by consumers of cryptographic services (such as the 158.Xr ipsec 4 159stack) that wish to establish a new session with the framework. 160On success, the first argument will contain the Session Identifier (SID). 161The second argument contains all the necessary information for 162the driver to establish the session. 163The third argument indicates whether a 164hardware driver (1) should be used or not (0). 165The various fields in the 166.Vt cryptoini 167structure are: 168.Bl -tag -width ".Va cri_next" 169.It Va cri_alg 170Contains an algorithm identifier. 171Currently supported algorithms are: 172.Pp 173.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact 174.It Dv CRYPTO_DES_CBC 175.It Dv CRYPTO_3DES_CBC 176.It Dv CRYPTO_BLF_CBC 177.It Dv CRYPTO_CAST_CBC 178.It Dv CRYPTO_SKIPJACK_CBC 179.It Dv CRYPTO_MD5_HMAC 180.It Dv CRYPTO_SHA1_HMAC 181.It Dv CRYPTO_RIPEMD160_HMAC 182.It Dv CRYPTO_MD5_KPDK 183.It Dv CRYPTO_SHA1_KPDK 184.It Dv CRYPTO_AES_CBC 185.It Dv CRYPTO_ARC4 186.It Dv CRYPTO_MD5 187.It Dv CRYPTO_SHA1 188.It Dv CRYPTO_SHA2_HMAC 189.It Dv CRYPTO_NULL_HMAC 190.It Dv CRYPTO_NULL_CBC 191.El 192.It Va cri_klen 193Specifies the length of the key in bits, for variable-size key 194algorithms. 195.It Va cri_rnd 196Specifies the number of rounds to be used with the algorithm, for 197variable-round algorithms. 198.It Va cri_key 199Contains the key to be used with the algorithm. 200.It Va cri_iv 201Contains an explicit initialization vector (IV), if it does not prefix 202the data. 203This field is ignored during initialization. 204If no IV is explicitly passed (see below on details), a random IV is used 205by the device driver processing the request. 206.It Va cri_next 207Contains a pointer to another 208.Vt cryptoini 209structure. 210Multiple such structures may be linked to establish multi-algorithm sessions 211.Xr ( ipsec 4 212is an example consumer of such a feature). 213.El 214.Pp 215The 216.Vt cryptoini 217structure and its contents will not be modified by the framework (or 218the drivers used). 219Subsequent requests for processing that use the 220SID returned will avoid the cost of re-initializing the hardware (in 221essence, SID acts as an index in the session cache of the driver). 222.Pp 223.Fn crypto_freesession 224is called with the SID returned by 225.Fn crypto_newsession 226to disestablish the session. 227.Pp 228.Fn crypto_dispatch 229is called to process a request. 230The various fields in the 231.Vt cryptop 232structure are: 233.Bl -tag -width ".Va crp_callback" 234.It Va crp_sid 235Contains the SID. 236.It Va crp_ilen 237Indicates the total length in bytes of the buffer to be processed. 238.It Va crp_olen 239On return, contains the total length of the result. 240For symmetric crypto operations, this will be the same as the input length. 241This will be used if the framework needs to allocate a new 242buffer for the result (or for re-formatting the input). 243.It Va crp_callback 244This routine is invoked upon completion of the request, whether 245successful or not. 246It is invoked through the 247.Fn crypto_done 248routine. 249If the request was not successful, an error code is set in the 250.Va crp_etype 251field. 252It is the responsibility of the callback routine to set the appropriate 253.Xr spl 9 254level. 255.It Va crp_etype 256Contains the error type, if any errors were encountered, or zero if 257the request was successfully processed. 258If the 259.Er EAGAIN 260error code is returned, the SID has changed (and has been recorded in the 261.Va crp_sid 262field). 263The consumer should record the new SID and use it in all subsequent requests. 264In this case, the request may be re-submitted immediately. 265This mechanism is used by the framework to perform 266session migration (move a session from one driver to another, because 267of availability, performance, or other considerations). 268.Pp 269Note that this field only makes sense when examined by 270the callback routine specified in 271.Va crp_callback . 272Errors are returned to the invoker of 273.Fn crypto_process 274only when enough information is not present to call the callback 275routine (i.e., if the pointer passed is 276.Dv NULL 277or if no callback routine was specified). 278.It Va crp_flags 279Is a bitmask of flags associated with this request. 280Currently defined flags are: 281.Bl -tag -width ".Dv CRYPTO_F_IMBUF" 282.It Dv CRYPTO_F_IMBUF 283The buffer pointed to by 284.Va crp_buf 285is an mbuf chain. 286.El 287.It Va crp_buf 288Points to the input buffer. 289On return (when the callback is invoked), 290it contains the result of the request. 291The input buffer may be an mbuf 292chain or a contiguous buffer, 293depending on 294.Va crp_flags . 295.It Va crp_opaque 296This is passed through the crypto framework untouched and is 297intended for the invoking application's use. 298.It Va crp_desc 299This is a linked list of descriptors. 300Each descriptor provides 301information about what type of cryptographic operation should be done 302on the input buffer. 303The various fields are: 304.Bl -tag -width ".Va crd_inject" 305.It Va crd_skip 306The offset in the input buffer where processing should start. 307.It Va crd_len 308How many bytes, after 309.Va crd_skip , 310should be processed. 311.It Va crd_inject 312Offset from the beginning of the buffer to insert any results. 313For encryption algorithms, this is where the initialization vector 314(IV) will be inserted when encrypting or where it can be found when 315decrypting (subject to 316.Va crd_flags ) . 317For MAC algorithms, this is where the result of the keyed hash will be 318inserted. 319.It Va crd_flags 320The following flags are defined: 321.Bl -tag -width ".Dv CRD_F_IV_EXPLICIT" 322.It Dv CRD_F_ENCRYPT 323For encryption algorithms, this bit is set when encryption is required 324(when not set, decryption is performed). 325.It Dv CRD_F_IV_PRESENT 326For encryption algorithms, this bit is set when the IV already 327precedes the data, so the 328.Va crd_inject 329value will be ignored and no IV will be written in the buffer. 330Otherwise, the IV used to encrypt the packet will be written 331at the location pointed to by 332.Va crd_inject . 333The IV length is assumed to be equal to the blocksize of the 334encryption algorithm. 335Some applications that do special 336.Dq "IV cooking" , 337such as the half-IV mode in 338.Xr ipsec 4 , 339can use this flag to indicate that the IV should not be written on the packet. 340This flag is typically used in conjunction with the 341.Dv CRD_F_IV_EXPLICIT 342flag. 343.It Dv CRD_F_IV_EXPLICIT 344For encryption algorithms, this bit is set when the IV is explicitly 345provided by the consumer in the 346.Va cri_iv 347fields. 348Otherwise, for encryption operations the IV is provided for by 349the driver used to perform the operation, whereas for decryption 350operations it is pointed to by the 351.Va crd_inject 352field. 353This flag is typically used when the IV is calculated 354.Dq "on the fly" 355by the consumer, and does not precede the data (some 356.Xr ipsec 4 357configurations, and the encrypted swap are two such examples). 358.It Dv CRD_F_COMP 359For compression algorithms, this bit is set when compression is required (when 360not set, decompression is performed). 361.El 362.It Va CRD_INI 363This 364.Vt cryptoini 365structure will not be modified by the framework or the device drivers. 366Since this information accompanies every cryptographic 367operation request, drivers may re-initialize state on-demand 368(typically an expensive operation). 369Furthermore, the cryptographic 370framework may re-route requests as a result of full queues or hardware 371failure, as described above. 372.It Va crd_next 373Point to the next descriptor. 374Linked operations are useful in protocols such as 375.Xr ipsec 4 , 376where multiple cryptographic transforms may be applied on the same 377block of data. 378.El 379.El 380.Pp 381.Fn crypto_getreq 382allocates a 383.Vt cryptop 384structure with a linked list of as many 385.Vt cryptodesc 386structures as were specified in the argument passed to it. 387.Pp 388.Fn crypto_freereq 389deallocates a structure 390.Vt cryptop 391and any 392.Vt cryptodesc 393structures linked to it. 394Note that it is the responsibility of the 395callback routine to do the necessary cleanups associated with the 396opaque field in the 397.Vt cryptop 398structure. 399.Pp 400.Fn crypto_kdispatch 401is called to perform a keying operation. 402The various fields in the 403.Vt cryptkop 404structure are: 405.Bl -tag -width ".Va krp_callback' 406.It Va krp_op 407Operation code, such as 408.Dv CRK_MOD_EXP . 409.It Va krp_status 410Return code. 411This 412.Va errno Ns -style 413variable indicates whether lower level reasons 414for operation failure. 415.It Va krp_iparams 416Number if input parameters to the specified operation. 417Note that each operation has a (typically hardwired) number of such parameters. 418.It Va krp_oparams 419Number if output parameters from the specified operation. 420Note that each operation has a (typically hardwired) number of such parameters. 421.It Va krp_kvp 422An array of kernel memory blocks containing the parameters. 423.It Va krp_hid 424Identifier specifying which low-level driver is being used. 425.It Va krp_callback 426Callback called on completion of a keying operation. 427.El 428.Sh DRIVER-SIDE API 429The 430.Fn crypto_get_driverid , 431.Fn crypto_register , 432.Fn crypto_kregister , 433.Fn crypto_unregister , 434.Fn crypto_unblock , 435and 436.Fn crypto_done 437routines are used by drivers that provide support for cryptographic 438primitives to register and unregister with the kernel crypto services 439framework. 440Drivers must first use the 441.Fn crypto_get_driverid 442function to acquire a driver identifier, specifying the 443.Fa cc_flags 444as an argument (normally 0, but software-only drivers should specify 445.Dv CRYPTOCAP_F_SOFTWARE ) . 446For each algorithm the driver supports, it must then call 447.Fn crypto_register . 448The first two arguments are the driver and algorithm identifiers. 449The next two arguments specify the largest possible operator length (in bits, 450important for public key operations) and flags for this algorithm. 451The last four arguments must be provided in the first call to 452.Fn crypto_register 453and are ignored in all subsequent calls. 454They are pointers to three 455driver-provided functions that the framework may call to establish new 456cryptographic context with the driver, free already established 457context, and ask for a request to be processed (encrypt, decrypt, 458etc.); and an opaque parameter to pass when calling each of these routines. 459.Fn crypto_unregister 460is called by drivers that wish to withdraw support for an algorithm. 461The two arguments are the driver and algorithm identifiers, respectively. 462Typically, drivers for 463PCMCIA 464crypto cards that are being ejected will invoke this routine for all 465algorithms supported by the card. 466.Fn crypto_unregister_all 467will unregister all algorithms registered by a driver 468and the driver will be disabled (no new sessions will be allocated on 469that driver, and any existing sessions will be migrated to other 470drivers). 471The same will be done if all algorithms associated with a driver are 472unregistered one by one. 473.Pp 474The calling convention for the three driver-supplied routines is: 475.Pp 476.Bl -item -compact 477.It 478.Ft int 479.Fn \*[lp]*newsession\*[rp] "void *" "u_int32_t *" "struct cryptoini *" ; 480.It 481.Ft int 482.Fn \*[lp]*freesession\*[rp] "void *" "u_int64_t" ; 483.It 484.Ft int 485.Fn \*[lp]*process\*[rp] "void *" "struct cryptop *" ; 486.It 487.Ft int 488.Fn \*[lp]*kprocess\*[rp] "void *" "struct cryptkop *" ; 489.El 490.Pp 491On invocation, the first argument to 492all routines is an opaque data value supplied when the algorithm 493is registered with 494.Fn crypto_register . 495The second argument to 496.Fn newsession 497contains the driver identifier obtained via 498.Fn crypto_get_driverid . 499On successful return, it should contain a driver-specific session 500identifier. 501The third argument is identical to that of 502.Fn crypto_newsession . 503.Pp 504The 505.Fn freesession 506routine takes as arguments the opaque data value and the SID 507(which is the concatenation of the 508driver identifier and the driver-specific session identifier). 509It should clear any context associated with the session (clear hardware 510registers, memory, etc.). 511.Pp 512The 513.Fn process 514routine is invoked with a request to perform crypto processing. 515This routine must not block, but should queue the request and return 516immediately. 517Upon processing the request, the callback routine should be invoked. 518In case of an unrecoverable error, the error indication must be placed in the 519.Va crp_etype 520field of the 521.Vt cryptop 522structure. 523When the request is completed, or an error is detected, the 524.Fn process 525routine should invoke 526.Fn crypto_done . 527Session migration may be performed, as mentioned previously. 528.Pp 529In case of a temporary resource exhaustion, the 530.Fn process 531routine may return 532.Er ERESTART 533in which case the crypto services will requeue the request, mark the driver 534as 535.Dq blocked , 536and stop submitting requests for processing. 537The driver is then responsible for notifying the crypto services 538when it is again able to process requests through the 539.Fn crypto_unblock 540routine. 541This simple flow control mechanism should only be used for short-lived 542resource exhaustion as it causes operations to be queued in the crypto 543layer. 544Doing so is preferable to returning an error in such cases as 545it can cause network protocols to degrade performance by treating the 546failure much like a lost packet. 547.Pp 548The 549.Fn kprocess 550routine is invoked with a request to perform crypto key processing. 551This routine must not block, but should queue the request and return 552immediately. 553Upon processing the request, the callback routine should be invoked. 554In case of an unrecoverable error, the error indication must be placed in the 555.Va krp_status 556field of the 557.Vt cryptkop 558structure. 559When the request is completed, or an error is detected, the 560.Fn kprocess 561routine should invoked 562.Fn crypto_kdone . 563.Sh RETURN VALUES 564.Fn crypto_register , 565.Fn crypto_kregister , 566.Fn crypto_unregister , 567.Fn crypto_newsession , 568.Fn crypto_freesession , 569and 570.Fn crypto_unblock 571return 0 on success, or an error code on failure. 572.Fn crypto_get_driverid 573returns a non-negative value on error, and \-1 on failure. 574.Fn crypto_getreq 575returns a pointer to a 576.Vt cryptop 577structure and 578.Dv NULL 579on failure. 580.Fn crypto_dispatch 581returns 582.Er EINVAL 583if its argument or the callback function was 584.Dv NULL , 585and 0 otherwise. 586The callback is provided with an error code in case of failure, in the 587.Va crp_etype 588field. 589.Sh FILES 590.Bl -tag -width ".Pa sys/opencrypto/crypto.c" 591.It Pa sys/opencrypto/crypto.c 592most of the framework code 593.El 594.Sh SEE ALSO 595.Xr ipsec 4 , 596.Xr malloc 9 , 597.Xr sleep 9 598.Sh HISTORY 599The cryptographic framework first appeared in 600.Ox 2.7 601and was written by 602.An "Angelos D. Keromytis" Aq angelos@openbsd.org . 603.Sh BUGS 604The framework currently assumes that all the algorithms in a 605.Fn crypto_newsession 606operation must be available by the same driver. 607If that is not the case, session initialization will fail. 608.Pp 609The framework also needs a mechanism for determining which driver is 610best for a specific set of algorithms associated with a session. 611Some type of benchmarking is in order here. 612.Pp 613Multiple instances of the same algorithm in the same session are not 614supported. 615Note that 3DES is considered one algorithm (and not three 616instances of DES). 617Thus, 3DES and DES could be mixed in the same request. 618