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
