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 sys/malloc.h 28.In sys/time.h 29.In opencrypto/cryptodev.h 30.Ft int32_t 31.Fn crypto_get_driverid "device_t dev" "int flags" 32.Ft int 33.Fn crypto_find_driver "const char *match" 34.Ft device_t 35.Fn crypto_find_device_byhid "int hid" 36.Ft int 37.Fn crypto_getcaps "int hid" 38.Ft int 39.Fn crypto_register "u_int32_t driverid" "int alg" "u_int16_t maxoplen" "u_int32_t flags" 40.Ft int 41.Fn crypto_kregister "u_int32_t driverid" "int kalg" "u_int32_t flags" 42.Ft int 43.Fn crypto_unregister "u_int32_t driverid" "int alg" 44.Ft int 45.Fn crypto_unregister_all "u_int32_t driverid" 46.Ft void 47.Fn crypto_done "struct cryptop *crp" 48.Ft void 49.Fn crypto_kdone "struct cryptkop *krp" 50.Ft int 51.Fn crypto_newsession "u_int64_t *sid" "struct cryptoini *cri" "int crid" 52.Ft int 53.Fn crypto_freesession "u_int64_t sid" 54.Ft int 55.Fn crypto_dispatch "struct cryptop *crp" 56.Ft int 57.Fn crypto_kdispatch "struct cryptkop *krp" 58.Ft int 59.Fn crypto_unblock "u_int32_t driverid" "int what" 60.Ft "struct cryptop *" 61.Fn crypto_getreq "int num" 62.Ft void 63.Fn crypto_freereq "struct cryptop *crp" 64.Bd -literal 65#define CRYPTO_SYMQ 0x1 66#define CRYPTO_ASYMQ 0x2 67 68#define EALG_MAX_BLOCK_LEN 16 69 70struct cryptoini { 71 int cri_alg; 72 int cri_klen; 73 int cri_mlen; 74 caddr_t cri_key; 75 u_int8_t cri_iv[EALG_MAX_BLOCK_LEN]; 76 struct cryptoini *cri_next; 77}; 78 79struct cryptodesc { 80 int crd_skip; 81 int crd_len; 82 int crd_inject; 83 int crd_flags; 84 struct cryptoini CRD_INI; 85#define crd_iv CRD_INI.cri_iv 86#define crd_key CRD_INI.cri_key 87#define crd_alg CRD_INI.cri_alg 88#define crd_klen CRD_INI.cri_klen 89 struct cryptodesc *crd_next; 90}; 91 92struct cryptop { 93 TAILQ_ENTRY(cryptop) crp_next; 94 u_int64_t crp_sid; 95 int crp_ilen; 96 int crp_olen; 97 int crp_etype; 98 int crp_flags; 99 caddr_t crp_buf; 100 caddr_t crp_opaque; 101 struct cryptodesc *crp_desc; 102 int (*crp_callback) (struct cryptop *); 103 caddr_t crp_mac; 104}; 105 106struct crparam { 107 caddr_t crp_p; 108 u_int crp_nbits; 109}; 110 111#define CRK_MAXPARAM 8 112 113struct cryptkop { 114 TAILQ_ENTRY(cryptkop) krp_next; 115 u_int krp_op; /* ie. CRK_MOD_EXP or other */ 116 u_int krp_status; /* return status */ 117 u_short krp_iparams; /* # of input parameters */ 118 u_short krp_oparams; /* # of output parameters */ 119 u_int32_t krp_hid; 120 struct crparam krp_param[CRK_MAXPARAM]; 121 int (*krp_callback)(struct cryptkop *); 122}; 123.Ed 124.Sh DESCRIPTION 125.Nm 126is a framework for drivers of cryptographic hardware to register with 127the kernel so 128.Dq consumers 129(other kernel subsystems, and 130users through the 131.Pa /dev/crypto 132device) are able to make use of it. 133Drivers register with the framework the algorithms they support, 134and provide entry points (functions) the framework may call to 135establish, use, and tear down sessions. 136Sessions are used to cache cryptographic information in a particular driver 137(or associated hardware), so initialization is not needed with every request. 138Consumers of cryptographic services pass a set of 139descriptors that instruct the framework (and the drivers registered 140with it) of the operations that should be applied on the data (more 141than one cryptographic operation can be requested). 142.Pp 143Keying operations are supported as well. 144Unlike the symmetric operators described above, 145these sessionless commands perform mathematical operations using 146input and output parameters. 147.Pp 148Since the consumers may not be associated with a process, drivers may 149not 150.Xr sleep 9 . 151The same holds for the framework. 152Thus, a callback mechanism is used 153to notify a consumer that a request has been completed (the 154callback is specified by the consumer on an per-request basis). 155The callback is invoked by the framework whether the request was 156successfully completed or not. 157An error indication is provided in the latter case. 158A specific error code, 159.Er EAGAIN , 160is used to indicate that a session number has changed and that the 161request may be re-submitted immediately with the new session number. 162Errors are only returned to the invoking function if not 163enough information to call the callback is available (meaning, there 164was a fatal error in verifying the arguments). 165For session initialization and teardown there is no callback mechanism used. 166.Pp 167The 168.Fn crypto_newsession 169routine is called by consumers of cryptographic services (such as the 170.Xr ipsec 4 171stack) that wish to establish a new session with the framework. 172On success, the first argument will contain the Session Identifier (SID). 173The second argument contains all the necessary information for 174the driver to establish the session. 175The third argument indicates whether a 176hardware driver (1) should be used or not (0). 177The various fields in the 178.Vt cryptoini 179structure are: 180.Bl -tag -width ".Va cri_next" 181.It Va cri_alg 182Contains an algorithm identifier. 183Currently supported algorithms are: 184.Pp 185.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact 186.It Dv CRYPTO_AES_CBC 187.It Dv CRYPTO_AES_XTS 188.It Dv CRYPTO_AES_CTR 189.It Dv CRYPTO_AES_GCM 190.It Dv CRYPTO_AES_GMAC 191.It Dv CRYPTO_AES_128_GMAC 192.It Dv CRYPTO_AES_192_GMAC 193.It Dv CRYPTO_AES_256_GMAC 194.It Dv CRYPTO_TWOFISH_CBC 195.It Dv CRYPTO_TWOFISH_XTS 196.It Dv CRYPTO_SERPENT_CBC 197.It Dv CRYPTO_SERPENT_XTS 198.It Dv CRYPTO_ARC4 199.It Dv CRYPTO_BLF_CBC 200.It Dv CRYPTO_CAMELLIA_CBC 201.It Dv CRYPTO_CAST_CBC 202.It Dv CRYPTO_DES_CBC 203.It Dv CRYPTO_3DES_CBC 204.It Dv CRYPTO_SKIPJACK_CBC 205.It Dv CRYPTO_MD5 206.It Dv CRYPTO_MD5_HMAC 207.It Dv CRYPTO_MD5_KPDK 208.It Dv CRYPTO_RIPEMD160_HMAC 209.It Dv CRYPTO_SHA1 210.It Dv CRYPTO_SHA1_HMAC 211.It Dv CRYPTO_SHA1_KPDK 212.It Dv CRYPTO_SHA2_256_HMAC 213.It Dv CRYPTO_SHA2_384_HMAC 214.It Dv CRYPTO_SHA2_512_HMAC 215.It Dv CRYPTO_NULL_HMAC 216.It Dv CRYPTO_NULL_CBC 217.El 218.It Va cri_klen 219Specifies the length of the key in bits, for variable-size key 220algorithms. 221.It Va cri_mlen 222Specifies how many bytes from the calculated hash should be copied back. 2230 means entire hash. 224.It Va cri_key 225Contains the key to be used with the algorithm. 226.It Va cri_iv 227Contains an explicit initialization vector (IV), if it does not prefix 228the data. 229This field is ignored during initialization. 230If no IV is explicitly passed (see below on details), a random IV is used 231by the device driver processing the request. 232.It Va cri_next 233Contains a pointer to another 234.Vt cryptoini 235structure. 236Multiple such structures may be linked to establish multi-algorithm sessions 237.Xr ( ipsec 4 238is an example consumer of such a feature). 239.El 240.Pp 241The 242.Vt cryptoini 243structure and its contents will not be modified by the framework (or 244the drivers used). 245Subsequent requests for processing that use the 246SID returned will avoid the cost of re-initializing the hardware (in 247essence, SID acts as an index in the session cache of the driver). 248.Pp 249.Fn crypto_freesession 250is called with the SID returned by 251.Fn crypto_newsession 252to disestablish the session. 253.Pp 254.Fn crypto_dispatch 255is called to process a request. 256The various fields in the 257.Vt cryptop 258structure are: 259.Bl -tag -width ".Va crp_callback" 260.It Va crp_sid 261Contains the SID. 262.It Va crp_ilen 263Indicates the total length in bytes of the buffer to be processed. 264.It Va crp_olen 265On return, contains the total length of the result. 266For symmetric crypto operations, this will be the same as the input length. 267This will be used if the framework needs to allocate a new 268buffer for the result (or for re-formatting the input). 269.It Va crp_callback 270This routine is invoked upon completion of the request, whether 271successful or not. 272It is invoked through the 273.Fn crypto_done 274routine. 275If the request was not successful, an error code is set in the 276.Va crp_etype 277field. 278It is the responsibility of the callback routine to enter a critical 279section. 280.It Va crp_etype 281Contains the error type, if any errors were encountered, or zero if 282the request was successfully processed. 283If the 284.Er EAGAIN 285error code is returned, the SID has changed (and has been recorded in the 286.Va crp_sid 287field). 288The consumer should record the new SID and use it in all subsequent requests. 289In this case, the request may be re-submitted immediately. 290This mechanism is used by the framework to perform 291session migration (move a session from one driver to another, because 292of availability, performance, or other considerations). 293.Pp 294Note that this field only makes sense when examined by 295the callback routine specified in 296.Va crp_callback . 297Errors are returned to the invoker of 298.Fn crypto_process 299only when enough information is not present to call the callback 300routine (i.e., if the pointer passed is 301.Dv NULL 302or if no callback routine was specified). 303.It Va crp_flags 304Is a bitmask of flags associated with this request. 305Currently defined flags are: 306.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC" 307.It Dv CRYPTO_F_IMBUF 308The buffer pointed to by 309.Va crp_buf 310is an mbuf chain. 311.It Dv CRYPTO_F_IOV 312The buffer pointed to by 313.Va crp_buf 314is an 315.Vt uio 316structure. 317.It Dv CRYPTO_F_REL 318Must return data in the same place. 319.It Dv CRYPTO_F_BATCH 320Batch operation if possible. 321.It Dv CRYPTO_F_CBIMM 322Do callback immediately instead of doing it from a dedicated kernel thread. 323.It Dv CRYPTO_F_DONE 324Operation completed. 325.It Dv CRYPTO_F_CBIFSYNC 326Do callback immediately if operation is synchronous. 327.El 328.It Va crp_buf 329Points to the input buffer. 330On return (when the callback is invoked), 331it contains the result of the request. 332The input buffer may be an mbuf 333chain or a contiguous buffer, 334depending on 335.Va crp_flags . 336.It Va crp_opaque 337This is passed through the crypto framework untouched and is 338intended for the invoking application's use. 339.It Va crp_desc 340This is a linked list of descriptors. 341Each descriptor provides 342information about what type of cryptographic operation should be done 343on the input buffer. 344The various fields are: 345.Bl -tag -width ".Va crd_inject" 346.It Va crd_iv 347The field where IV should be provided when the 348.Dv CRD_F_IV_EXPLICIT 349flag is given. 350.It Va crd_key 351When the 352.Dv CRD_F_KEY_EXPLICIT 353flag is given, the 354.Va crd_key 355points to a buffer with encryption or authentication key. 356.It Va crd_alg 357An algorithm to use. 358Must be the same as the one given at newsession time. 359.It Va crd_klen 360The 361.Va crd_key 362key length. 363.It Va crd_skip 364The offset in the input buffer where processing should start. 365.It Va crd_len 366How many bytes, after 367.Va crd_skip , 368should be processed. 369.It Va crd_inject 370Offset from the beginning of the buffer to insert any results. 371For encryption algorithms, this is where the initialization vector 372(IV) will be inserted when encrypting or where it can be found when 373decrypting (subject to 374.Va crd_flags ) . 375For MAC algorithms, this is where the result of the keyed hash will be 376inserted. 377.It Va crd_flags 378The following flags are defined: 379.Bl -tag -width 3n 380.It Dv CRD_F_ENCRYPT 381For encryption algorithms, this bit is set when encryption is required 382(when not set, decryption is performed). 383.It Dv CRD_F_IV_PRESENT 384For encryption algorithms, this bit is set when the IV already 385precedes the data, so the 386.Va crd_inject 387value will be ignored and no IV will be written in the buffer. 388Otherwise, the IV used to encrypt the packet will be written 389at the location pointed to by 390.Va crd_inject . 391The IV length is assumed to be equal to the blocksize of the 392encryption algorithm. 393Some applications that do special 394.Dq "IV cooking" , 395such as the half-IV mode in 396.Xr ipsec 4 , 397can use this flag to indicate that the IV should not be written on the packet. 398This flag is typically used in conjunction with the 399.Dv CRD_F_IV_EXPLICIT 400flag. 401.It Dv CRD_F_IV_EXPLICIT 402For encryption algorithms, this bit is set when the IV is explicitly 403provided by the consumer in the 404.Va crd_iv 405field. 406Otherwise, for encryption operations the IV is provided for by 407the driver used to perform the operation, whereas for decryption 408operations it is pointed to by the 409.Va crd_inject 410field. 411This flag is typically used when the IV is calculated 412.Dq "on the fly" 413by the consumer, and does not precede the data (some 414.Xr ipsec 4 415configurations, and the encrypted swap are two such examples). 416.It Dv CRD_F_KEY_EXPLICIT 417For encryption and authentication (MAC) algorithms, this bit is set when the key 418is explicitly provided by the consumer in the 419.Va crd_key 420field for the given operation. 421Otherwise, the key is taken at newsession time from the 422.Va cri_key 423field. 424.It Dv CRD_F_COMP 425For compression algorithms, this bit is set when compression is required (when 426not set, decompression is performed). 427.El 428.It Va CRD_INI 429This 430.Vt cryptoini 431structure will not be modified by the framework or the device drivers. 432Since this information accompanies every cryptographic 433operation request, drivers may re-initialize state on-demand 434(typically an expensive operation). 435Furthermore, the cryptographic 436framework may re-route requests as a result of full queues or hardware 437failure, as described above. 438.It Va crd_next 439Point to the next descriptor. 440Linked operations are useful in protocols such as 441.Xr ipsec 4 , 442where multiple cryptographic transforms may be applied on the same 443block of data. 444.El 445.El 446.Pp 447.Fn crypto_getreq 448allocates a 449.Vt cryptop 450structure with a linked list of as many 451.Vt cryptodesc 452structures as were specified in the argument passed to it. 453.Pp 454.Fn crypto_freereq 455deallocates a structure 456.Vt cryptop 457and any 458.Vt cryptodesc 459structures linked to it. 460Note that it is the responsibility of the 461callback routine to do the necessary cleanups associated with the 462opaque field in the 463.Vt cryptop 464structure. 465.Pp 466.Fn crypto_kdispatch 467is called to perform a keying operation. 468The various fields in the 469.Vt cryptkop 470structure are: 471.Bl -tag -width ".Va krp_callback" 472.It Va krp_op 473Operation code, such as 474.Dv CRK_MOD_EXP . 475.It Va krp_status 476Return code. 477This 478.Va errno Ns -style 479variable indicates whether lower level reasons 480for operation failure. 481.It Va krp_iparams 482Number if input parameters to the specified operation. 483Note that each operation has a (typically hardwired) number of such parameters. 484.It Va krp_oparams 485Number if output parameters from the specified operation. 486Note that each operation has a (typically hardwired) number of such parameters. 487.It Va krp_kvp 488An array of kernel memory blocks containing the parameters. 489.It Va krp_hid 490Identifier specifying which low-level driver is being used. 491.It Va krp_callback 492Callback called on completion of a keying operation. 493.El 494.Sh DRIVER-SIDE API 495The 496.Fn crypto_get_driverid , 497.Fn crypto_register , 498.Fn crypto_kregister , 499.Fn crypto_unregister , 500.Fn crypto_unblock , 501and 502.Fn crypto_done 503routines are used by drivers that provide support for cryptographic 504primitives to register and unregister with the kernel crypto services 505framework. 506Drivers must first use the 507.Fn crypto_get_driverid 508function to acquire a driver identifier, specifying the 509.Fa cc_flags 510as an argument (normally 0, but software-only drivers should specify 511.Dv CRYPTOCAP_F_SOFTWARE ) . 512For each algorithm the driver supports, it must then call 513.Fn crypto_register . 514The first two arguments are the driver and algorithm identifiers. 515The next two arguments specify the largest possible operator length (in bits, 516important for public key operations) and flags for this algorithm. 517The last four arguments must be provided in the first call to 518.Fn crypto_register 519and are ignored in all subsequent calls. 520They are pointers to three 521driver-provided functions that the framework may call to establish new 522cryptographic context with the driver, free already established 523context, and ask for a request to be processed (encrypt, decrypt, 524etc.); and an opaque parameter to pass when calling each of these routines. 525.Fn crypto_unregister 526is called by drivers that wish to withdraw support for an algorithm. 527The two arguments are the driver and algorithm identifiers, respectively. 528Typically, drivers for 529PCMCIA 530crypto cards that are being ejected will invoke this routine for all 531algorithms supported by the card. 532.Fn crypto_unregister_all 533will unregister all algorithms registered by a driver 534and the driver will be disabled (no new sessions will be allocated on 535that driver, and any existing sessions will be migrated to other 536drivers). 537The same will be done if all algorithms associated with a driver are 538unregistered one by one. 539.Pp 540The calling convention for the three driver-supplied routines is: 541.Pp 542.Bl -item -compact 543.It 544.Ft int 545.Fn (*newsession) "void *" "u_int32_t *" "struct cryptoini *" ; 546.It 547.Ft int 548.Fn (*freesession) "void *" "u_int64_t" ; 549.It 550.Ft int 551.Fn (*process) "void *" "struct cryptop *" ; 552.It 553.Ft int 554.Fn (*kprocess) "void *" "struct cryptkop *" ; 555.El 556.Pp 557On invocation, the first argument to 558all routines is an opaque data value supplied when the algorithm 559is registered with 560.Fn crypto_register . 561The second argument to 562.Fn newsession 563contains the driver identifier obtained via 564.Fn crypto_get_driverid . 565On successful return, it should contain a driver-specific session 566identifier. 567The third argument is identical to that of 568.Fn crypto_newsession . 569.Pp 570The 571.Fn freesession 572routine takes as arguments the opaque data value and the SID 573(which is the concatenation of the 574driver identifier and the driver-specific session identifier). 575It should clear any context associated with the session (clear hardware 576registers, memory, etc.). 577.Pp 578The 579.Fn process 580routine is invoked with a request to perform crypto processing. 581This routine must not block, but should queue the request and return 582immediately. 583Upon processing the request, the callback routine should be invoked. 584In case of an unrecoverable error, the error indication must be placed in the 585.Va crp_etype 586field of the 587.Vt cryptop 588structure. 589When the request is completed, or an error is detected, the 590.Fn process 591routine should invoke 592.Fn crypto_done . 593Session migration may be performed, as mentioned previously. 594.Pp 595In case of a temporary resource exhaustion, the 596.Fn process 597routine may return 598.Er ERESTART 599in which case the crypto services will requeue the request, mark the driver 600as 601.Dq blocked , 602and stop submitting requests for processing. 603The driver is then responsible for notifying the crypto services 604when it is again able to process requests through the 605.Fn crypto_unblock 606routine. 607This simple flow control mechanism should only be used for short-lived 608resource exhaustion as it causes operations to be queued in the crypto 609layer. 610Doing so is preferable to returning an error in such cases as 611it can cause network protocols to degrade performance by treating the 612failure much like a lost packet. 613.Pp 614The 615.Fn kprocess 616routine is invoked with a request to perform crypto key processing. 617This routine must not block, but should queue the request and return 618immediately. 619Upon processing the request, the callback routine should be invoked. 620In case of an unrecoverable error, the error indication must be placed in the 621.Va krp_status 622field of the 623.Vt cryptkop 624structure. 625When the request is completed, or an error is detected, the 626.Fn kprocess 627routine should invoked 628.Fn crypto_kdone . 629.Sh RETURN VALUES 630.Fn crypto_register , 631.Fn crypto_kregister , 632.Fn crypto_unregister , 633.Fn crypto_newsession , 634.Fn crypto_freesession , 635and 636.Fn crypto_unblock 637return 0 on success, or an error code on failure. 638.Fn crypto_get_driverid 639returns a non-negative value on error, and \-1 on failure. 640.Fn crypto_getreq 641returns a pointer to a 642.Vt cryptop 643structure and 644.Dv NULL 645on failure. 646.Fn crypto_dispatch 647returns 648.Er EINVAL 649if its argument or the callback function was 650.Dv NULL , 651and 0 otherwise. 652The callback is provided with an error code in case of failure, in the 653.Va crp_etype 654field. 655.Sh FILES 656.Bl -tag -width ".Pa sys/opencrypto/crypto.c" 657.It Pa sys/opencrypto/crypto.c 658most of the framework code 659.El 660.Sh SEE ALSO 661.Xr ipsec 4 , 662.Xr kmalloc 9 , 663.Xr sleep 9 664.Sh HISTORY 665The cryptographic framework first appeared in 666.Ox 2.7 667and was written by 668.An Angelos D. Keromytis Aq Mt angelos@openbsd.org . 669.Sh BUGS 670The framework currently assumes that all the algorithms in a 671.Fn crypto_newsession 672operation must be available by the same driver. 673If that is not the case, session initialization will fail. 674.Pp 675The framework also needs a mechanism for determining which driver is 676best for a specific set of algorithms associated with a session. 677Some type of benchmarking is in order here. 678.Pp 679Multiple instances of the same algorithm in the same session are not 680supported. 681Note that 3DES is considered one algorithm (and not three 682instances of DES). 683Thus, 3DES and DES could be mixed in the same request. 684