OPENCRYPTO(9) FreeBSD Kernel Developer's Manual OPENCRYPTO(9)
NAME
opencrypto, crypto_get_driverid, crypto_register, crypto_kregister,
crypto_unregister, crypto_unregister_all, crypto_done, crypto_kdone,
crypto_newsession, crypto_freesession, crypto_dispatch, crypto_kdispatch,
crypto_getreq, crypto_freereq crypto_kgetreq, crypto_kfreereq - API for
cryptographic services in the kernel
SYNOPSIS
#include <opencrypto/cryptodev.h>
int32_t
crypto_get_driverid(u_int32_t);
int
crypto_register(u_int32_t, int, u_int16_t, u_int32_t,
int (*)(void *, u_int32_t *, struct cryptoini *),
int (*)(void *, u_int32_t *), int (*)(u_int64_t),
int (*)(struct cryptop *), void *);
int
crypto_kregister(u_int32_t, int, u_int32_t,
int (*)(void *, struct cryptkop *, int), void *);
int
crypto_unregister(u_int32_t, int);
int
crypto_unregister_all(u_int32_t);
void
crypto_done(struct cryptop *);
void
crypto_kdone(struct cryptkop *);
int
crypto_newsession(u_int64_t *, struct cryptoini *, int);
void
crypto_freesession(u_int64_t);
void
crypto_dispatch(struct cryptop *);
void
crypto_kdispatch(struct cryptkop *);
struct cryptop *
crypto_getreq(int);
void
crypto_freereq(struct cryptop *);
struct cryptop *
crypto_kgetreq(int, int);
void
crypto_kfreereq(struct cryptop *);
#define EALG_MAX_BLOCK_LEN 16
struct cryptoini {
int cri_alg;
int cri_klen;
int cri_rnd;
void *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;
void *crp_buf;
void *crp_opaque;
struct cryptodesc *crp_desc;
int (*crp_callback)(struct cryptop *);
void *crp_mac;
};
struct crparam {
void *crp_p;
u_int crp_nbits;
};
#define CRK_MAXPARAM 8
struct cryptkop {
TAILQ_ENTRY(cryptkop) krp_next;
u_int krp_op; /* i.e. 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]; /* kvm */
int (*krp_callback)(struct cryptkop *);
};
DESCRIPTION
opencrypto is a framework for drivers of cryptographic hardware to
register with the kernel so "consumers" (other kernel subsystems, and
eventually users through an appropriate device) are able to make use of
it. Drivers register 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 registered 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
operations using input and output parameters.
Since the consumers may not be associated with a process, drivers may not
use condition variables: condvar(9). The same holds for the framework.
Thus, a callback mechanism is used to notify a consumer that a request
has been completed (the callback is specified by the consumer on an per-
request basis). The callback is invoked by the framework whether the
request was successfully completed 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). No callback mechanism is used for session initialization and
teardown.
The crypto_newsession() routine is called by consumers of cryptographic
services (such as the ipsec(4) stack) that wish to establish a new
session 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 should be used (1) or not
(0). The various fields in the cryptoini structure are:
cri_alg Contains an algorithm identifier. Currently supported
algorithms are:
CRYPTO_DES_CBC
CRYPTO_3DES_CBC
CRYPTO_BLF_CBC
CRYPTO_CAST_CBC
CRYPTO_CAMELLIA_CBC
CRYPTO_SKIPJACK_CBC
CRYPTO_ARC4
CRYPTO_AES_CBC
CRYPTO_AES_CTR
CRYPTO_AES_GCM_16
CRYPTO_AES_GMAC
CRYPTO_AES_128_GMAC
CRYPTO_AES_192_GMAC
CRYPTO_AES_256_GMAC
CRYPTO_AES_XCBC_MAC_96
CRYPTO_MD5
CRYPTO_MD5_HMAC
CRYPTO_MD5_HMAC_96
CRYPTO_MD5_KPDK
CRYPTO_NULL_CBC
CRYPTO_NULL_HMAC
CRYPTO_SHA1
CRYPTO_SHA1_HMAC
CRYPTO_SHA1_HMAC_96
CRYPTO_SHA1_KPDK
CRYPTO_SHA2_256_HMAC
CRYPTO_SHA2_384_HMAC
CRYPTO_SHA2_512_HMAC
CRYPTO_RIPEMD160_HMAC
CRYPTO_RIPEMD160_HMAC_96
CRYPTO_DEFLATE_COMP
CRYPTO_DEFLATE_COMP_NOGROW
CRYPTO_GZIP_COMP
cri_klen Specifies the length of the key in bits, for variable-size
key algorithms.
cri_rnd Specifies the number of rounds to be used with the
algorithm, for variable-round algorithms.
cri_key Contains the key to be used with the algorithm.
cri_iv 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.
cri_next Contains a pointer to another cryptoini structure.
Multiple such structures may be linked to establish multi-
algorithm sessions (ipsec(4) is an example consumer of such
a feature).
The cryptoini 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).
crypto_freesession() is called with the SID returned by
crypto_newsession() to disestablish the session.
crypto_dispatch() is called to process a request. The various fields in
the cryptop structure are:
crp_sid Contains the SID.
crp_ilen Indicates the total length in bytes of the buffer to be
processed.
crp_olen On return, contains the length of the result, not including
crd_skip. For symmetric crypto operations, this will be
the same as the input length.
crp_alloctype
Indicates the type of buffer, as used in the kernel
malloc(9) routine. This will be used if the framework
needs to allocate a new buffer for the result (or for re-
formatting the input).
crp_callback This routine is invoked upon completion of the request,
whether successful or not. It is invoked by the driver
through the crypto_done() routine. If the request was not
successful, an error code is set in the crp_etype field.
crp_etype Contains the error type, if any errors were encountered, or
zero if the request was successfully processed.
Note that this field only makes sense when examined by the
callback routine specified in crp_callback. Errors are
returned to the invoker of crypto_process() only when
enough information is not present to call the callback
routine (i.e., if the pointer passed is NULL or if no
callback routine was specified).
crp_flags Is a bitmask of flags associated with this request.
Currently defined flags are:
CRYPTO_F_IMBUF The buffer pointed to by crp_buf is an mbuf
chain.
crp_buf 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
(of a type identified by crp_alloctype), depending on
crp_flags.
crp_opaque This is passed through the crypto framework untouched and
is intended for the invoking application's use.
crp_desc This is a linked list of descriptors. Each descriptor
provides information about what type of cryptographic
operation should be done on the input buffer. The various
fields are:
crd_skip The offset in the input buffer where processing
should start.
crd_len How many bytes, after crd_skip, should be
processed.
crd_inject 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
crd_flags). For MAC algorithms, this is where
the result of the keyed hash will be inserted.
crd_flags For adjusting general operation from userland,
the following flags are defined:
CRD_F_ENCRYPT For encryption algorithms,
this bit is set when
encryption is required (when
not set, decryption is
performed).
CRD_F_IV_PRESENT For encryption algorithms,
this bit is set when the IV
already precedes the data,
so the crd_inject value will
be ignored and no IV will be
written in the buffer.
Otherwise, the IV used to
encrypt the packet will be
written at the location
pointed to by crd_inject.
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
typically 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 crd_iv
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 crd_inject
field. This flag is
typically 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
compression is required
(when not set, decompression
is performed).
CRD_INI This cryptoini structure will not be modified
by the framework or the device drivers. Since
this information accompanies every
cryptographic operation request, drivers may
re-initialize 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.
crd_next Point to the next descriptor. Linked
operations are useful in protocols such as
ipsec(4), where multiple cryptographic
transforms may be applied on the same block of
data.
crypto_getreq() allocates a cryptop structure with a linked list of as
many cryptodesc structures as were specified in the argument passed to
it, which must be at least 1.
crypto_freereq() deallocates a structure cryptop and any cryptodesc
structures linked to it. Note that it is the responsibility of the
callback routine to do the necessary cleanups associated with the opaque
field in the cryptop structure.
crypto_kdispatch() is called to perform a keying operation. The various
fields in the crytokop structure are:
krp_op Operation code, such as CRK_MOD_EXP.
krp_status Return code. This errno-style variable indicates whether
there were lower level reasons for operation failure.
krp_iparams Number of input parameters to the specified operation.
Note that each operation has a (typically hardwired)
number of such parameters.
krp_oparams Number of output parameters from the specified operation.
Note that each operation has a (typically hardwired)
number of such parameters.
krp_kvp An array of kernel memory blocks containing the
parameters.
krp_hid Identifier specifying which low-level driver is being
used.
krp_callback Callback called on completion of a keying operation.
crypto_kgetreq() allocates a cryptkop structure. The first argument
means the same as crypto_getreq(), except it is currently limited to be
exactly 1. The second argument means flags passed to pool_get().
crypto_kfreereq() deallocates a structure cryptkop structure.
The following sysctl entries exist to adjust the behaviour of the system
from userland:
kern.usercrypto Allow (1) or forbid (0) userland access
to /dev/crypto.
kern.userasymcrypto Allow (1) or forbid (0) userland access
to do asymmetric crypto requests.
kern.cryptodevallowsoft Enable/disable access to hardware versus
software operations:
< 0 Force userlevel requests to use
software operations, always.
= 0 Use hardware if present, grant
userlevel requests for non-
accelerated operations (handling
the latter in software).
> 0 Allow user requests only for
operations which are hardware-
accelerated.
opencrypto.crypto_ret_q.maxlen Limit the length of queue(crypto_ret_q)
which mediates between crypto driver's
completion and calling cryptop callback.
When the queue exceeds this limit,
crypto_getreq() fails.
<= 0 means unlimited.
opencrypto.crypto_ret_kq.maxlen Limit the length of queue(crypto_ret_kq)
which mediates between crypto driver's
completion and calling cryptkop
callback. When the queue exceeds this
limit, crypto_kgetreq() fails.
<= 0 means unlimited.
The following sysctl entries exist to get statistics.
opencrypto.crypto_ret_q.len Current crypto_ret_q length.
opencrypto.crypto_ret_q.drops The count of crypto_getreq() failed as
overflow opencrypto.crypto_ret_q.maxlen.
opencrypto.crypto_ret_kq.len Current crypto_ret_kq length.
opencrypto.crypto_ret_kq.drops The count of crypto_kgetreq() failed as
overflow opencrypto.crypto_ret_kq.maxlen.
DRIVER-SIDE API
The crypto_get_driverid(), crypto_register(), crypto_kregister(),
crypto_unregister(), crypto_unregister_all(), and crypto_done() routines
are used by drivers that provide support for cryptographic primitives to
register and unregister with the kernel crypto services framework.
Drivers must first use the crypto_get_driverid() function to acquire a
driver identifier, specifying the flags as an argument (normally 0, but
software-only drivers should specify CRYPTOCAP_F_SOFTWARE). For each
algorithm the driver supports, it must then call crypto_register(). The
first argument is the driver identifier. The second argument is an array
of CRYPTO_ALGORITHM_MAX + 1 elements, indicating which algorithms are
supported. The last three arguments 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.)
crypto_unregister() is called by drivers that wish to withdraw support
for an algorithm. The two arguments are the driver and algorithm
identifiers, respectively. algorithms supported by the card. If all
algorithms associated with a driver are unregistered, the driver will be
disabled (no new sessions will be allocated on that driver, and any
existing sessions will be migrated to other drivers).
crypto_unregister_all() will unregister all registered algorithms,
disable the driver, and migrate existing sessions to other drivers.
The calling convention for the three driver-supplied routines is:
int (*newsession) (void *, u_int32_t *, struct cryptoini *);
void (*freesession) (void *, u_int64_t);
int (*process) (void *, struct cryptop *, int);
On invocation, the first argument to newsession() contains the driver
identifier obtained via crypto_get_driverid(). On successfully
returning, it should contain a driver-specific session identifier. The
second argument is identical to that of crypto_newsession().
The freesession() routine takes as argument the SID (which is the
concatenation of the driver identifier and the driver-specific session
identifier returned by newsession().) It should clear any context
associated with the session (clear hardware registers, memory, etc.).
The process() routine is invoked with a request to perform crypto
processing. 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 error, the error indication must
be placed in the crp_etype field of the cryptop structure. The hint
argument can be set to CRYPTO_HINT_MORE when there will be more request
right after this request. When the request is completed, or an error is
detected, the process() routine should invoke crypto_done(). Session
migration may be performed, as mentioned previously.
The kprocess() 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
routine should be invoked. In case of error, the error indication must
be placed in the krp_status field of the cryptkop structure. When the
request is completed, or an error is detected, the kprocess() routine
should invoke crypto_kdone().
RETURN VALUES
crypto_register(), crypto_kregister(), crypto_unregister(), and
crypto_newsession() return 0 on success, or an error code on failure.
crypto_get_driverid() returns a non-negative value on error, and -1 on
failure. crypto_getreq() returns a pointer to a cryptop structure and
NULL on failure. crypto_kgetreq() returns a pointer to a cryptkop
structure and NULL on failure. crypto_dispatch() arranges to invoke the
callback with an error code in the crp_etype field, or zero on success.
FILES
sys/opencrypto/crypto.c most of the framework code
sys/crypto crypto algorithm implementations
SEE ALSO
ipsec(4), pcmcia(4), condvar(9), malloc(9), pool(9)
Angelos D. Keromytis, Jason L. Wright, and Theo de Raadt, The Design of
the OpenBSD Cryptographic Framework, Usenix, 2003, June 2003.
HISTORY
The cryptographic framework first appeared in OpenBSD 2.7 and was written
by Angelos D. Keromytis <
[email protected]>.
Sam Leffler ported the crypto framework to FreeBSD and made performance
improvements.
Jonathan Stone <
[email protected]> ported the cryptoframe from FreeBSD
to NetBSD. opencrypto first appeared in NetBSD 2.0.
BUGS
The framework currently assumes that all the algorithms in a
crypto_newsession() operation must be available by the same driver. If
that's 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
supported. 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 14.1-RELEASE-p8 May 26, 2017 FreeBSD 14.1-RELEASE-p8