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 June 4, 2006 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 an 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_DES_CBC 179.It Dv CRYPTO_3DES_CBC 180.It Dv CRYPTO_BLF_CBC 181.It Dv CRYPTO_CAST_CBC 182.It Dv CRYPTO_SKIPJACK_CBC 183.It Dv CRYPTO_MD5_HMAC 184.It Dv CRYPTO_SHA1_HMAC 185.It Dv CRYPTO_RIPEMD160_HMAC 186.It Dv CRYPTO_MD5_KPDK 187.It Dv CRYPTO_SHA1_KPDK 188.It Dv CRYPTO_AES_CBC 189.It Dv CRYPTO_ARC4 190.It Dv CRYPTO_MD5 191.It Dv CRYPTO_SHA1 192.It Dv CRYPTO_SHA2_256_HMAC 193.It Dv CRYPTO_SHA2_384_HMAC 194.It Dv CRYPTO_SHA2_512_HMAC 195.It Dv CRYPTO_NULL_HMAC 196.It Dv CRYPTO_NULL_CBC 197.El 198.It Va cri_klen 199Specifies the length of the key in bits, for variable-size key 200algorithms. 201.It Va cri_mlen 202Specifies how many bytes from the calculated hash should be copied back. 2030 means entire hash. 204.It Va cri_key 205Contains the key to be used with the algorithm. 206.It Va cri_iv 207Contains an explicit initialization vector (IV), if it does not prefix 208the data. 209This field is ignored during initialization. 210If no IV is explicitly passed (see below on details), a random IV is used 211by the device driver processing the request. 212.It Va cri_next 213Contains a pointer to another 214.Vt cryptoini 215structure. 216Multiple such structures may be linked to establish multi-algorithm sessions 217.Xr ( ipsec 4 218is an example consumer of such a feature). 219.El 220.Pp 221The 222.Vt cryptoini 223structure and its contents will not be modified by the framework (or 224the drivers used). 225Subsequent requests for processing that use the 226SID returned will avoid the cost of re-initializing the hardware (in 227essence, SID acts as an index in the session cache of the driver). 228.Pp 229.Fn crypto_freesession 230is called with the SID returned by 231.Fn crypto_newsession 232to disestablish the session. 233.Pp 234.Fn crypto_dispatch 235is called to process a request. 236The various fields in the 237.Vt cryptop 238structure are: 239.Bl -tag -width ".Va crp_callback" 240.It Va crp_sid 241Contains the SID. 242.It Va crp_ilen 243Indicates the total length in bytes of the buffer to be processed. 244.It Va crp_olen 245On return, contains the total length of the result. 246For symmetric crypto operations, this will be the same as the input length. 247This will be used if the framework needs to allocate a new 248buffer for the result (or for re-formatting the input). 249.It Va crp_callback 250This routine is invoked upon completion of the request, whether 251successful or not. 252It is invoked through the 253.Fn crypto_done 254routine. 255If the request was not successful, an error code is set in the 256.Va crp_etype 257field. 258It is the responsibility of the callback routine to set the appropriate 259.Xr spl 9 260level. 261.It Va crp_etype 262Contains the error type, if any errors were encountered, or zero if 263the request was successfully processed. 264If the 265.Er EAGAIN 266error code is returned, the SID has changed (and has been recorded in the 267.Va crp_sid 268field). 269The consumer should record the new SID and use it in all subsequent requests. 270In this case, the request may be re-submitted immediately. 271This mechanism is used by the framework to perform 272session migration (move a session from one driver to another, because 273of availability, performance, or other considerations). 274.Pp 275Note that this field only makes sense when examined by 276the callback routine specified in 277.Va crp_callback . 278Errors are returned to the invoker of 279.Fn crypto_process 280only when enough information is not present to call the callback 281routine (i.e., if the pointer passed is 282.Dv NULL 283or if no callback routine was specified). 284.It Va crp_flags 285Is a bitmask of flags associated with this request. 286Currently defined flags are: 287.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC" 288.It Dv CRYPTO_F_IMBUF 289The buffer pointed to by 290.Va crp_buf 291is an mbuf chain. 292.It Dv CRYPTO_F_IOV 293The buffer pointed to by 294.Va crp_buf 295is an 296.Vt uio 297structure. 298.It Dv CRYPTO_F_REL 299Must return data in the same place. 300.It Dv CRYPTO_F_BATCH 301Batch operation if possible. 302.It Dv CRYPTO_F_CBIMM 303Do callback immediately instead of doing it from a dedicated kernel thread. 304.It Dv CRYPTO_F_DONE 305Operation completed. 306.It Dv CRYPTO_F_CBIFSYNC 307Do callback immediately if operation is synchronous. 308.El 309.It Va crp_buf 310Points to the input buffer. 311On return (when the callback is invoked), 312it contains the result of the request. 313The input buffer may be an mbuf 314chain or a contiguous buffer, 315depending on 316.Va crp_flags . 317.It Va crp_opaque 318This is passed through the crypto framework untouched and is 319intended for the invoking application's use. 320.It Va crp_desc 321This is a linked list of descriptors. 322Each descriptor provides 323information about what type of cryptographic operation should be done 324on the input buffer. 325The various fields are: 326.Bl -tag -width ".Va crd_inject" 327.It Va crd_iv 328The field where IV should be provided when the 329.Dv CRD_F_IV_EXPLICIT 330flag is given. 331.It Va crd_key 332When the 333.Dv CRD_F_KEY_EXPLICIT 334flag is given, the 335.Va crd_key 336points to a buffer with encryption or authentication key. 337.It Va crd_alg 338An algorithm to use. 339Must be the same as the one given at newsession time. 340.It Va crd_klen 341The 342.Va crd_key 343key length. 344.It Va crd_skip 345The offset in the input buffer where processing should start. 346.It Va crd_len 347How many bytes, after 348.Va crd_skip , 349should be processed. 350.It Va crd_inject 351Offset from the beginning of the buffer to insert any results. 352For encryption algorithms, this is where the initialization vector 353(IV) will be inserted when encrypting or where it can be found when 354decrypting (subject to 355.Va crd_flags ) . 356For MAC algorithms, this is where the result of the keyed hash will be 357inserted. 358.It Va crd_flags 359The following flags are defined: 360.Bl -tag -width 3n 361.It Dv CRD_F_ENCRYPT 362For encryption algorithms, this bit is set when encryption is required 363(when not set, decryption is performed). 364.It Dv CRD_F_IV_PRESENT 365For encryption algorithms, this bit is set when the IV already 366precedes the data, so the 367.Va crd_inject 368value will be ignored and no IV will be written in the buffer. 369Otherwise, the IV used to encrypt the packet will be written 370at the location pointed to by 371.Va crd_inject . 372The IV length is assumed to be equal to the blocksize of the 373encryption algorithm. 374Some applications that do special 375.Dq "IV cooking" , 376such as the half-IV mode in 377.Xr ipsec 4 , 378can use this flag to indicate that the IV should not be written on the packet. 379This flag is typically used in conjunction with the 380.Dv CRD_F_IV_EXPLICIT 381flag. 382.It Dv CRD_F_IV_EXPLICIT 383For encryption algorithms, this bit is set when the IV is explicitly 384provided by the consumer in the 385.Va crd_iv 386field. 387Otherwise, for encryption operations the IV is provided for by 388the driver used to perform the operation, whereas for decryption 389operations it is pointed to by the 390.Va crd_inject 391field. 392This flag is typically used when the IV is calculated 393.Dq "on the fly" 394by the consumer, and does not precede the data (some 395.Xr ipsec 4 396configurations, and the encrypted swap are two such examples). 397.It Dv CRD_F_KEY_EXPLICIT 398For encryption and authentication (MAC) algorithms, this bit is set when the key 399is explicitly provided by the consumer in the 400.Va crd_key 401field for the given operation. 402Otherwise, the key is taken at newsession time from the 403.Va cri_key 404field. 405.It Dv CRD_F_COMP 406For compression algorithms, this bit is set when compression is required (when 407not set, decompression is performed). 408.El 409.It Va CRD_INI 410This 411.Vt cryptoini 412structure will not be modified by the framework or the device drivers. 413Since this information accompanies every cryptographic 414operation request, drivers may re-initialize state on-demand 415(typically an expensive operation). 416Furthermore, the cryptographic 417framework may re-route requests as a result of full queues or hardware 418failure, as described above. 419.It Va crd_next 420Point to the next descriptor. 421Linked operations are useful in protocols such as 422.Xr ipsec 4 , 423where multiple cryptographic transforms may be applied on the same 424block of data. 425.El 426.El 427.Pp 428.Fn crypto_getreq 429allocates a 430.Vt cryptop 431structure with a linked list of as many 432.Vt cryptodesc 433structures as were specified in the argument passed to it. 434.Pp 435.Fn crypto_freereq 436deallocates a structure 437.Vt cryptop 438and any 439.Vt cryptodesc 440structures linked to it. 441Note that it is the responsibility of the 442callback routine to do the necessary cleanups associated with the 443opaque field in the 444.Vt cryptop 445structure. 446.Pp 447.Fn crypto_kdispatch 448is called to perform a keying operation. 449The various fields in the 450.Vt cryptkop 451structure are: 452.Bl -tag -width ".Va krp_callback' 453.It Va krp_op 454Operation code, such as 455.Dv CRK_MOD_EXP . 456.It Va krp_status 457Return code. 458This 459.Va errno Ns -style 460variable indicates whether lower level reasons 461for operation failure. 462.It Va krp_iparams 463Number if input parameters to the specified operation. 464Note that each operation has a (typically hardwired) number of such parameters. 465.It Va krp_oparams 466Number if output parameters from the specified operation. 467Note that each operation has a (typically hardwired) number of such parameters. 468.It Va krp_kvp 469An array of kernel memory blocks containing the parameters. 470.It Va krp_hid 471Identifier specifying which low-level driver is being used. 472.It Va krp_callback 473Callback called on completion of a keying operation. 474.El 475.Sh DRIVER-SIDE API 476The 477.Fn crypto_get_driverid , 478.Fn crypto_register , 479.Fn crypto_kregister , 480.Fn crypto_unregister , 481.Fn crypto_unblock , 482and 483.Fn crypto_done 484routines are used by drivers that provide support for cryptographic 485primitives to register and unregister with the kernel crypto services 486framework. 487Drivers must first use the 488.Fn crypto_get_driverid 489function to acquire a driver identifier, specifying the 490.Fa cc_flags 491as an argument (normally 0, but software-only drivers should specify 492.Dv CRYPTOCAP_F_SOFTWARE ) . 493For each algorithm the driver supports, it must then call 494.Fn crypto_register . 495The first two arguments are the driver and algorithm identifiers. 496The next two arguments specify the largest possible operator length (in bits, 497important for public key operations) and flags for this algorithm. 498The last four arguments must be provided in the first call to 499.Fn crypto_register 500and are ignored in all subsequent calls. 501They are pointers to three 502driver-provided functions that the framework may call to establish new 503cryptographic context with the driver, free already established 504context, and ask for a request to be processed (encrypt, decrypt, 505etc.); and an opaque parameter to pass when calling each of these routines. 506.Fn crypto_unregister 507is called by drivers that wish to withdraw support for an algorithm. 508The two arguments are the driver and algorithm identifiers, respectively. 509Typically, drivers for 510PCMCIA 511crypto cards that are being ejected will invoke this routine for all 512algorithms supported by the card. 513.Fn crypto_unregister_all 514will unregister all algorithms registered by a driver 515and the driver will be disabled (no new sessions will be allocated on 516that driver, and any existing sessions will be migrated to other 517drivers). 518The same will be done if all algorithms associated with a driver are 519unregistered one by one. 520.Pp 521The calling convention for the three driver-supplied routines is: 522.Pp 523.Bl -item -compact 524.It 525.Ft int 526.Fn \*[lp]*newsession\*[rp] "void *" "u_int32_t *" "struct cryptoini *" ; 527.It 528.Ft int 529.Fn \*[lp]*freesession\*[rp] "void *" "u_int64_t" ; 530.It 531.Ft int 532.Fn \*[lp]*process\*[rp] "void *" "struct cryptop *" ; 533.It 534.Ft int 535.Fn \*[lp]*kprocess\*[rp] "void *" "struct cryptkop *" ; 536.El 537.Pp 538On invocation, the first argument to 539all routines is an opaque data value supplied when the algorithm 540is registered with 541.Fn crypto_register . 542The second argument to 543.Fn newsession 544contains the driver identifier obtained via 545.Fn crypto_get_driverid . 546On successful return, it should contain a driver-specific session 547identifier. 548The third argument is identical to that of 549.Fn crypto_newsession . 550.Pp 551The 552.Fn freesession 553routine takes as arguments the opaque data value and the SID 554(which is the concatenation of the 555driver identifier and the driver-specific session identifier). 556It should clear any context associated with the session (clear hardware 557registers, memory, etc.). 558.Pp 559The 560.Fn process 561routine is invoked with a request to perform crypto processing. 562This routine must not block, but should queue the request and return 563immediately. 564Upon processing the request, the callback routine should be invoked. 565In case of an unrecoverable error, the error indication must be placed in the 566.Va crp_etype 567field of the 568.Vt cryptop 569structure. 570When the request is completed, or an error is detected, the 571.Fn process 572routine should invoke 573.Fn crypto_done . 574Session migration may be performed, as mentioned previously. 575.Pp 576In case of a temporary resource exhaustion, the 577.Fn process 578routine may return 579.Er ERESTART 580in which case the crypto services will requeue the request, mark the driver 581as 582.Dq blocked , 583and stop submitting requests for processing. 584The driver is then responsible for notifying the crypto services 585when it is again able to process requests through the 586.Fn crypto_unblock 587routine. 588This simple flow control mechanism should only be used for short-lived 589resource exhaustion as it causes operations to be queued in the crypto 590layer. 591Doing so is preferable to returning an error in such cases as 592it can cause network protocols to degrade performance by treating the 593failure much like a lost packet. 594.Pp 595The 596.Fn kprocess 597routine is invoked with a request to perform crypto key processing. 598This routine must not block, but should queue the request and return 599immediately. 600Upon processing the request, the callback routine should be invoked. 601In case of an unrecoverable error, the error indication must be placed in the 602.Va krp_status 603field of the 604.Vt cryptkop 605structure. 606When the request is completed, or an error is detected, the 607.Fn kprocess 608routine should invoked 609.Fn crypto_kdone . 610.Sh RETURN VALUES 611.Fn crypto_register , 612.Fn crypto_kregister , 613.Fn crypto_unregister , 614.Fn crypto_newsession , 615.Fn crypto_freesession , 616and 617.Fn crypto_unblock 618return 0 on success, or an error code on failure. 619.Fn crypto_get_driverid 620returns a non-negative value on error, and \-1 on failure. 621.Fn crypto_getreq 622returns a pointer to a 623.Vt cryptop 624structure and 625.Dv NULL 626on failure. 627.Fn crypto_dispatch 628returns 629.Er EINVAL 630if its argument or the callback function was 631.Dv NULL , 632and 0 otherwise. 633The callback is provided with an error code in case of failure, in the 634.Va crp_etype 635field. 636.Sh FILES 637.Bl -tag -width ".Pa sys/opencrypto/crypto.c" 638.It Pa sys/opencrypto/crypto.c 639most of the framework code 640.El 641.Sh SEE ALSO 642.Xr ipsec 4 , 643.Xr malloc 9 , 644.Xr sleep 9 645.Sh HISTORY 646The cryptographic framework first appeared in 647.Ox 2.7 648and was written by 649.An "Angelos D. Keromytis" Aq angelos@openbsd.org . 650.Sh BUGS 651The framework currently assumes that all the algorithms in a 652.Fn crypto_newsession 653operation must be available by the same driver. 654If that is not the case, session initialization will fail. 655.Pp 656The framework also needs a mechanism for determining which driver is 657best for a specific set of algorithms associated with a session. 658Some type of benchmarking is in order here. 659.Pp 660Multiple instances of the same algorithm in the same session are not 661supported. 662Note that 3DES is considered one algorithm (and not three 663instances of DES). 664Thus, 3DES and DES could be mixed in the same request. 665