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);
int
crypto_freesession(
u_int64_t);
int
crypto_dispatch(
struct
cryptop *);
int
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 through the
crypto_done() routine. If the request was not
successful, an error code is set in the crp_etype
field. It is the responsibility of the callback routine to set the
appropriate spl(9) level.
-
-
- crp_etype
- 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 crp_sid 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
considerations).
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.
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(). 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 *);
int (*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). 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(),
crypto_newsession(),
and
crypto_freesession() 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() 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 failure, in the
crp_etype
field.
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
<
angelos@openbsd.org>.
Sam Leffler ported the crypto framework to
FreeBSD and made performance improvements.
Jonathan Stone
<
jonathan@NetBSD.org>
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.
A queue for completed operations should be implemented and processed at some
software
spl(9) level, to avoid
overall system latency issues, and potential kernel stack exhaustion while
processing a callback.
When SMP time comes, we will support use of a second processor (or more) as a
crypto device (this is actually AMP, but we need the same basic
support).