CRYPTO(9) FreeBSD Kernel Developer's Manual CRYPTO(9) NNAAMMEE ccrryyppttoo -- API for cryptographic services in the kernel SSYYNNOOPPSSIISS ##iinncclluuddee <<ooppeennccrryyppttoo//ccrryyppttooddeevv..hh>> _i_n_t_3_2___t ccrryyppttoo__ggeett__ddrriivveerriidd(_u___i_n_t_8___t); _i_n_t ccrryyppttoo__rreeggiisstteerr(_u___i_n_t_3_2___t, _i_n_t, _u___i_n_t_1_6___t, _u___i_n_t_3_2___t, _i_n_t (_*)(_v_o_i_d _*_, _u___i_n_t_3_2___t _*_, _s_t_r_u_c_t _c_r_y_p_t_o_i_n_i _*), _i_n_t (_*)(_v_o_i_d _*_, _u___i_n_t_6_4___t), _i_n_t (_*)(_v_o_i_d _*_, _s_t_r_u_c_t _c_r_y_p_t_o_p _*), _v_o_i_d _*); _i_n_t ccrryyppttoo__kkrreeggiisstteerr(_u___i_n_t_3_2___t, _i_n_t, _u___i_n_t_3_2___t, _i_n_t (_*)(_v_o_i_d _*_, _s_t_r_u_c_t _c_r_y_p_t_k_o_p _*), _v_o_i_d _*); _i_n_t ccrryyppttoo__uunnrreeggiisstteerr(_u___i_n_t_3_2___t, _i_n_t); _i_n_t ccrryyppttoo__uunnrreeggiisstteerr__aallll(_u___i_n_t_3_2___t); _v_o_i_d ccrryyppttoo__ddoonnee(_s_t_r_u_c_t _c_r_y_p_t_o_p _*); _v_o_i_d ccrryyppttoo__kkddoonnee(_s_t_r_u_c_t _c_r_y_p_t_k_o_p _*); _i_n_t ccrryyppttoo__nneewwsseessssiioonn(_u___i_n_t_6_4___t _*, _s_t_r_u_c_t _c_r_y_p_t_o_i_n_i _*, _i_n_t); _i_n_t ccrryyppttoo__ffrreeeesseessssiioonn(_u___i_n_t_6_4___t); _i_n_t ccrryyppttoo__ddiissppaattcchh(_s_t_r_u_c_t _c_r_y_p_t_o_p _*); _i_n_t ccrryyppttoo__kkddiissppaattcchh(_s_t_r_u_c_t _c_r_y_p_t_k_o_p _*); _i_n_t ccrryyppttoo__uunnbblloocckk(_u___i_n_t_3_2___t, _i_n_t); _s_t_r_u_c_t _c_r_y_p_t_o_p _* ccrryyppttoo__ggeettrreeqq(_i_n_t); _v_o_i_d ccrryyppttoo__ffrreeeerreeqq(_v_o_i_d); #define CRYPTO_SYMQ 0x1 #define CRYPTO_ASYMQ 0x2 #define EALG_MAX_BLOCK_LEN 16 struct cryptoini { int cri_alg; int cri_klen; int cri_rnd; caddr_t cri_key; u_int8_t cri_iv[EALG_MAX_BLOCK_LEN]; struct cryptoini *cri_next; }; struct cryptodesc { int crd_skip; int crd_len; int crd_inject; int crd_flags; struct cryptoini CRD_INI; struct cryptodesc *crd_next; }; struct cryptop { TAILQ_ENTRY(cryptop) crp_next; u_int64_t crp_sid; int crp_ilen; int crp_olen; int crp_etype; int crp_flags; caddr_t crp_buf; caddr_t crp_opaque; struct cryptodesc *crp_desc; int (*crp_callback) (struct cryptop *); caddr_t crp_mac; }; struct crparam { caddr_t crp_p; u_int crp_nbits; }; #define CRK_MAXPARAM 8 struct cryptkop { TAILQ_ENTRY(cryptkop) krp_next; u_int krp_op; /* ie. CRK_MOD_EXP or other */ u_int krp_status; /* return status */ u_short krp_iparams; /* # of input parameters */ u_short krp_oparams; /* # of output parameters */ u_int32_t krp_hid; struct crparam krp_param[CRK_MAXPARAM]; int (*krp_callback)(struct cryptkop *); }; DDEESSCCRRIIPPTTIIOONN ccrryyppttoo is a framework for drivers of cryptographic hardware to register with the kernel so ``consumers'' (other kernel subsystems, and users through the _/_d_e_v_/_c_r_y_p_t_o device) are able to make use of it. Drivers reg- ister with the framework the algorithms they support, and provide entry points (functions) the framework may call to establish, use, and tear down sessions. Sessions are used to cache cryptographic information in a particular driver (or associated hardware), so initialization is not needed with every request. Consumers of cryptographic services pass a set of descriptors that instruct the framework (and the drivers regis- tered with it) of the operations that should be applied on the data (more than one cryptographic operation can be requested). Keying operations are supported as well. Unlike the symmetric operators described above, these sessionless commands perform mathematical opera- tions using input and output parameters. Since the consumers may not be associated with a process, drivers may not sleep(9). The same holds for the framework. Thus, a callback mechanism is used to notify a consumer that a request has been completed (the call- back is specified by the consumer on an per-request basis). The callback is invoked by the framework whether the request was successfully com- pleted or not. An error indication is provided in the latter case. A specific error code, EAGAIN, is used to indicate that a session number has changed and that the request may be re-submitted immediately with the new session number. Errors are only returned to the invoking function if not enough information to call the callback is available (meaning, there was a fatal error in verifying the arguments). For session initializa- tion and teardown there is no callback mechanism used. The ccrryyppttoo__nneewwsseessssiioonn() routine is called by consumers of cryptographic services (such as the ipsec(4) stack) that wish to establish a new ses- sion with the framework. On success, the first argument will contain the Session Identifier (SID). The second argument contains all the necessary information for the driver to establish the session. The third argument indicates whether a hardware driver (1) should be used or not (0). The various fields in the _c_r_y_p_t_o_i_n_i structure are: _c_r_i___a_l_g Contains an algorithm identifier. Currently supported algo- rithms are: CRYPTO_DES_CBC CRYPTO_3DES_CBC CRYPTO_BLF_CBC CRYPTO_CAST_CBC CRYPTO_SKIPJACK_CBC CRYPTO_MD5_HMAC CRYPTO_SHA1_HMAC CRYPTO_RIPEMD160_HMAC CRYPTO_MD5_KPDK CRYPTO_SHA1_KPDK CRYPTO_AES_CBC CRYPTO_ARC4 CRYPTO_MD5 CRYPTO_SHA1 CRYPTO_SHA2_HMAC CRYPTO_NULL_HMAC CRYPTO_NULL_CBC _c_r_i___k_l_e_n Specifies the length of the key in bits, for variable-size key algorithms. _c_r_i___r_n_d Specifies the number of rounds to be used with the algorithm, for variable-round algorithms. _c_r_i___k_e_y Contains the key to be used with the algorithm. _c_r_i___i_v Contains an explicit initialization vector (IV), if it does not prefix the data. This field is ignored during initialization. If no IV is explicitly passed (see below on details), a random IV is used by the device driver processing the request. _c_r_i___n_e_x_t Contains a pointer to another _c_r_y_p_t_o_i_n_i structure. Multiple such structures may be linked to establish multi-algorithm ses- sions (ipsec(4) is an example consumer of such a feature). The _c_r_y_p_t_o_i_n_i structure and its contents will not be modified by the framework (or the drivers used). Subsequent requests for processing that use the SID returned will avoid the cost of re-initializing the hardware (in essence, SID acts as an index in the session cache of the driver). ccrryyppttoo__ffrreeeesseessssiioonn() is called with the SID returned by ccrryyppttoo__nneewwsseessssiioonn() to disestablish the session. ccrryyppttoo__ddiissppaattcchh() is called to process a request. The various fields in the _c_r_y_p_t_o_p structure are: _c_r_p___s_i_d Contains the SID. _c_r_p___i_l_e_n Indicates the total length in bytes of the buffer to be processed. _c_r_p___o_l_e_n On return, contains the total length of the result. For symmetric crypto operations, this will be the same as the input length. This will be used if the framework needs to allocate a new buffer for the result (or for re-formatting the input). _c_r_p___c_a_l_l_b_a_c_k This routine is invoked upon completion of the request, whether successful or not. It is invoked through the ccrryyppttoo__ddoonnee() routine. If the request was not successful, an error code is set in the _c_r_p___e_t_y_p_e field. It is the responsibility of the callback routine to set the appropri- ate spl(9) level. _c_r_p___e_t_y_p_e Contains the error type, if any errors were encountered, or zero if the request was successfully processed. If the EAGAIN error code is returned, the SID has changed (and has been recorded in the _c_r_p___s_i_d field). The consumer should record the new SID and use it in all subsequent requests. In this case, the request may be re-submitted immediately. This mechanism is used by the framework to perform session migration (move a session from one driver to another, because of availability, performance, or other considera- tions). Note that this field only makes sense when examined by the callback routine specified in _c_r_p___c_a_l_l_b_a_c_k. Errors are returned to the invoker of ccrryyppttoo__pprroocceessss() only when enough information is not present to call the callback rou- tine (i.e., if the pointer passed is NULL or if no callback routine was specified). _c_r_p___f_l_a_g_s Is a bitmask of flags associated with this request. Cur- rently defined flags are: CRYPTO_F_IMBUF The buffer pointed to by _c_r_p___b_u_f is an mbuf chain. _c_r_p___b_u_f Points to the input buffer. On return (when the callback is invoked), it contains the result of the request. The input buffer may be an mbuf chain or a contiguous buffer, depending on _c_r_p___f_l_a_g_s. _c_r_p___o_p_a_q_u_e This is passed through the crypto framework untouched and is intended for the invoking application's use. _c_r_p___d_e_s_c This is a linked list of descriptors. Each descriptor pro- vides information about what type of cryptographic opera- tion should be done on the input buffer. The various fields are: _c_r_d___s_k_i_p The offset in the input buffer where processing should start. _c_r_d___l_e_n How many bytes, after _c_r_d___s_k_i_p, should be pro- cessed. _c_r_d___i_n_j_e_c_t Offset from the beginning of the buffer to insert any results. For encryption algorithms, this is where the initialization vector (IV) will be inserted when encrypting or where it can be found when decrypting (subject to _c_r_d___f_l_a_g_s). For MAC algorithms, this is where the result of the keyed hash will be inserted. _c_r_d___f_l_a_g_s The following flags are defined: CRD_F_ENCRYPT For encryption algorithms, this bit is set when encryp- tion is required (when not set, decryption is per- formed). CRD_F_IV_PRESENT For encryption algorithms, this bit is set when the IV already precedes the data, so the _c_r_d___i_n_j_e_c_t value will be ignored and no IV will be written in the buffer. Oth- erwise, the IV used to encrypt the packet will be written at the location pointed to by _c_r_d___i_n_j_e_c_t. The IV length is assumed to be equal to the blocksize of the encryption algorithm. Some applications that do special ``IV cooking'', such as the half-IV mode in ipsec(4), can use this flag to indicate that the IV should not be written on the packet. This flag is typi- cally used in conjunction with the CRD_F_IV_EXPLICIT flag. CRD_F_IV_EXPLICIT For encryption algorithms, this bit is set when the IV is explicitly provided by the consumer in the _c_r_i___i_v fields. Otherwise, for encryption operations the IV is provided for by the driver used to perform the operation, whereas for decryption operations it is pointed to by the _c_r_d___i_n_j_e_c_t field. This flag is typi- cally used when the IV is calculated ``on the fly'' by the consumer, and does not precede the data (some ipsec(4) configurations, and the encrypted swap are two such examples). CRD_F_COMP For compression algorithms, this bit is set when com- pression is required (when not set, decompression is performed). _C_R_D___I_N_I This _c_r_y_p_t_o_i_n_i structure will not be modified by the framework or the device drivers. Since this information accompanies every crypto- graphic operation request, drivers may re-ini- tialize state on-demand (typically an expensive operation). Furthermore, the cryptographic framework may re-route requests as a result of full queues or hardware failure, as described above. _c_r_d___n_e_x_t Point to the next descriptor. Linked opera- tions are useful in protocols such as ipsec(4), where multiple cryptographic transforms may be applied on the same block of data. ccrryyppttoo__ggeettrreeqq() allocates a _c_r_y_p_t_o_p structure with a linked list of as many _c_r_y_p_t_o_d_e_s_c structures as were specified in the argument passed to it. ccrryyppttoo__ffrreeeerreeqq() deallocates a structure _c_r_y_p_t_o_p and any _c_r_y_p_t_o_d_e_s_c structures linked to it. Note that it is the responsibility of the call- back routine to do the necessary cleanups associated with the opaque field in the _c_r_y_p_t_o_p structure. ccrryyppttoo__kkddiissppaattcchh() is called to perform a keying operation. The various fields in the _c_r_y_p_t_k_o_p structure are: _k_r_p___o_p Operation code, such as CRK_MOD_EXP. _k_r_p___s_t_a_t_u_s Return code. This _e_r_r_n_o-style variable indicates whether lower level reasons for operation failure. _k_r_p___i_p_a_r_a_m_s Number if input parameters to the specified operation. Note that each operation has a (typically hardwired) num- ber of such parameters. _k_r_p___o_p_a_r_a_m_s Number if output parameters from the specified operation. Note that each operation has a (typically hardwired) num- ber of such parameters. _k_r_p___k_v_p An array of kernel memory blocks containing the parame- ters. _k_r_p___h_i_d Identifier specifying which low-level driver is being used. _k_r_p___c_a_l_l_b_a_c_k Callback called on completion of a keying operation. DDRRIIVVEERR--SSIIDDEE AAPPII The ccrryyppttoo__ggeett__ddrriivveerriidd(), ccrryyppttoo__rreeggiisstteerr(), ccrryyppttoo__kkrreeggiisstteerr(), ccrryyppttoo__uunnrreeggiisstteerr(), ccrryyppttoo__uunnbblloocckk(), and ccrryyppttoo__ddoonnee() routines are used by drivers that provide support for cryptographic primitives to reg- ister and unregister with the kernel crypto services framework. Drivers must first use the ccrryyppttoo__ggeett__ddrriivveerriidd() function to acquire a driver identifier, specifying the _c_c___f_l_a_g_s as an argument (normally 0, but soft- ware-only drivers should specify CRYPTOCAP_F_SOFTWARE). For each algo- rithm the driver supports, it must then call ccrryyppttoo__rreeggiisstteerr(). The first two arguments are the driver and algorithm identifiers. The next two arguments specify the largest possible operator length (in bits, important for public key operations) and flags for this algorithm. The last four arguments must be provided in the first call to ccrryyppttoo__rreeggiisstteerr() and are ignored in all subsequent calls. They are pointers to three driver-provided functions that the framework may call to establish new cryptographic context with the driver, free already established context, and ask for a request to be processed (encrypt, decrypt, etc.); and an opaque parameter to pass when calling each of these routines. ccrryyppttoo__uunnrreeggiisstteerr() is called by drivers that wish to withdraw support for an algorithm. The two arguments are the driver and algorithm identifiers, respectively. Typically, drivers for PCMCIA crypto cards that are being ejected will invoke this routine for all algorithms supported by the card. ccrryyppttoo__uunnrreeggiisstteerr__aallll() will unregis- ter all algorithms registered by a driver and the driver will be disabled (no new sessions will be allocated on that driver, and any existing ses- sions will be migrated to other drivers). The same will be done if all algorithms associated with a driver are unregistered one by one. The calling convention for the three driver-supplied routines is: _i_n_t (**nneewwsseessssiioonn)(_v_o_i_d _*, _u___i_n_t_3_2___t _*, _s_t_r_u_c_t _c_r_y_p_t_o_i_n_i _*); _i_n_t (**ffrreeeesseessssiioonn)(_v_o_i_d _*, _u___i_n_t_6_4___t); _i_n_t (**pprroocceessss)(_v_o_i_d _*, _s_t_r_u_c_t _c_r_y_p_t_o_p _*); _i_n_t (**kkpprroocceessss)(_v_o_i_d _*, _s_t_r_u_c_t _c_r_y_p_t_k_o_p _*); On invocation, the first argument to all routines is an opaque data value supplied when the algorithm is registered with ccrryyppttoo__rreeggiisstteerr(). The second argument to nneewwsseessssiioonn() contains the driver identifier obtained via ccrryyppttoo__ggeett__ddrriivveerriidd(). On successful return, it should contain a driver-specific session identifier. The third argument is identical to that of ccrryyppttoo__nneewwsseessssiioonn(). The ffrreeeesseessssiioonn() routine takes as arguments the opaque data value and the SID (which is the concatenation of the driver identifier and the driver-specific session identifier). It should clear any context associ- ated with the session (clear hardware registers, memory, etc.). The pprroocceessss() routine is invoked with a request to perform crypto pro- cessing. This routine must not block, but should queue the request and return immediately. Upon processing the request, the callback routine should be invoked. In case of an unrecoverable error, the error indica- tion must be placed in the _c_r_p___e_t_y_p_e field of the _c_r_y_p_t_o_p structure. When the request is completed, or an error is detected, the pprroocceessss() routine should invoke ccrryyppttoo__ddoonnee(). Session migration may be performed, as mentioned previously. In case of a temporary resource exhaustion, the pprroocceessss() routine may return ERESTART in which case the crypto services will requeue the request, mark the driver as ``blocked'', and stop submitting requests for processing. The driver is then responsible for notifying the crypto ser- vices when it is again able to process requests through the ccrryyppttoo__uunnbblloocckk() routine. This simple flow control mechanism should only be used for short-lived resource exhaustion as it causes operations to be queued in the crypto layer. Doing so is preferable to returning an error in such cases as it can cause network protocols to degrade performance by treating the failure much like a lost packet. The kkpprroocceessss() routine is invoked with a request to perform crypto key processing. This routine must not block, but should queue the request and return immediately. Upon processing the request, the callback rou- tine should be invoked. In case of an unrecoverable error, the error indication must be placed in the _k_r_p___s_t_a_t_u_s field of the _c_r_y_p_t_k_o_p struc- ture. When the request is completed, or an error is detected, the kkpprroocceessss() routine should invoked ccrryyppttoo__kkddoonnee(). RREETTUURRNN VVAALLUUEESS ccrryyppttoo__rreeggiisstteerr(), ccrryyppttoo__kkrreeggiisstteerr(), ccrryyppttoo__uunnrreeggiisstteerr(), ccrryyppttoo__nneewwsseessssiioonn(), ccrryyppttoo__ffrreeeesseessssiioonn(), and ccrryyppttoo__uunnbblloocckk() return 0 on success, or an error code on failure. ccrryyppttoo__ggeett__ddrriivveerriidd() returns a non-negative value on error, and -1 on failure. ccrryyppttoo__ggeettrreeqq() returns a pointer to a _c_r_y_p_t_o_p structure and NULL on failure. ccrryyppttoo__ddiissppaattcchh() returns EINVAL if its argument or the callback function was NULL, and 0 otherwise. The callback is provided with an error code in case of fail- ure, in the _c_r_p___e_t_y_p_e field. FFIILLEESS sys/opencrypto/crypto.c most of the framework code SSEEEE AALLSSOO ipsec(4), malloc(9), sleep(9) HHIISSTTOORRYY The cryptographic framework first appeared in OpenBSD 2.7 and was written by Angelos D. Keromytis <angelos@openbsd.org>. BBUUGGSS The framework currently assumes that all the algorithms in a ccrryyppttoo__nneewwsseessssiioonn() operation must be available by the same driver. If that is not the case, session initialization will fail. The framework also needs a mechanism for determining which driver is best for a specific set of algorithms associated with a session. Some type of benchmarking is in order here. Multiple instances of the same algorithm in the same session are not sup- ported. Note that 3DES is considered one algorithm (and not three instances of DES). Thus, 3DES and DES could be mixed in the same request. FreeBSD 6.0 October 14, 2002 FreeBSD 6.0