663 lines
21 KiB
Groff
663 lines
21 KiB
Groff
.\" $OpenBSD: crypto.9,v 1.19 2002/07/16 06:31:57 angelos Exp $
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.\"
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.\" The author of this manual page is Angelos D. Keromytis (angelos@cis.upenn.edu)
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.\"
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.\" Copyright (c) 2000, 2001 Angelos D. Keromytis
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.\"
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.\" Permission to use, copy, and modify this software with or without fee
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.\" is hereby granted, provided that this entire notice is included in
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.\" all source code copies of any software which is or includes a copy or
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.\" modification of this software.
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.\"
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.\" THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
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.\" IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
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.\" REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
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.\" MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
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.\" PURPOSE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 4, 2006
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.Dt CRYPTO 9
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.Os
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.Sh NAME
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.Nm crypto
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.Nd API for cryptographic services in the kernel
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.Sh SYNOPSIS
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.In opencrypto/cryptodev.h
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.Ft int32_t
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.Fn crypto_get_driverid u_int8_t
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.Ft int
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.Fn crypto_register u_int32_t int u_int16_t u_int32_t "int \*[lp]*\*[rp]\*[lp]void *, u_int32_t *, struct cryptoini *\*[rp]" "int \*[lp]*\*[rp]\*[lp]void *, u_int64_t\*[rp]" "int \*[lp]*\*[rp]\*[lp]void *, struct cryptop *\*[rp]" "void *"
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.Ft int
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.Fn crypto_kregister u_int32_t int u_int32_t "int \*[lp]*\*[rp]\*[lp]void *, struct cryptkop *\*[rp]" "void *"
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.Ft int
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.Fn crypto_unregister u_int32_t int
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.Ft int
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.Fn crypto_unregister_all u_int32_t
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.Ft void
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.Fn crypto_done "struct cryptop *"
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.Ft void
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.Fn crypto_kdone "struct cryptkop *"
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.Ft int
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.Fn crypto_newsession "u_int64_t *" "struct cryptoini *" int
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.Ft int
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.Fn crypto_freesession u_int64_t
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.Ft int
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.Fn crypto_dispatch "struct cryptop *"
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.Ft int
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.Fn crypto_kdispatch "struct cryptkop *"
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.Ft int
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.Fn crypto_unblock u_int32_t int
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.Ft "struct cryptop *"
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.Fn crypto_getreq int
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.Ft void
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.Fn crypto_freereq void
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.Bd -literal
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#define CRYPTO_SYMQ 0x1
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#define CRYPTO_ASYMQ 0x2
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#define EALG_MAX_BLOCK_LEN 16
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struct cryptoini {
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int cri_alg;
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int cri_klen;
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int cri_mlen;
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caddr_t cri_key;
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u_int8_t cri_iv[EALG_MAX_BLOCK_LEN];
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struct cryptoini *cri_next;
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};
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struct cryptodesc {
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int crd_skip;
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int crd_len;
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int crd_inject;
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int crd_flags;
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struct cryptoini CRD_INI;
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#define crd_iv CRD_INI.cri_iv
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#define crd_key CRD_INI.cri_key
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#define crd_alg CRD_INI.cri_alg
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#define crd_klen CRD_INI.cri_klen
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struct cryptodesc *crd_next;
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};
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struct cryptop {
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TAILQ_ENTRY(cryptop) crp_next;
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u_int64_t crp_sid;
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int crp_ilen;
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int crp_olen;
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int crp_etype;
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int crp_flags;
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caddr_t crp_buf;
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caddr_t crp_opaque;
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struct cryptodesc *crp_desc;
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int (*crp_callback) (struct cryptop *);
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caddr_t crp_mac;
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};
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struct crparam {
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caddr_t crp_p;
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u_int crp_nbits;
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};
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#define CRK_MAXPARAM 8
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struct cryptkop {
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TAILQ_ENTRY(cryptkop) krp_next;
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u_int krp_op; /* ie. CRK_MOD_EXP or other */
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u_int krp_status; /* return status */
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u_short krp_iparams; /* # of input parameters */
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u_short krp_oparams; /* # of output parameters */
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u_int32_t krp_hid;
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struct crparam krp_param[CRK_MAXPARAM];
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int (*krp_callback)(struct cryptkop *);
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};
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.Ed
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.Sh DESCRIPTION
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.Nm
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is a framework for drivers of cryptographic hardware to register with
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the kernel so
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.Dq consumers
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(other kernel subsystems, and
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users through the
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.Pa /dev/crypto
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device) are able to make use of it.
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Drivers register with the framework the algorithms they support,
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and provide entry points (functions) the framework may call to
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establish, use, and tear down sessions.
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Sessions are used to cache cryptographic information in a particular driver
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(or associated hardware), so initialization is not needed with every request.
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Consumers of cryptographic services pass a set of
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descriptors that instruct the framework (and the drivers registered
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with it) of the operations that should be applied on the data (more
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than one cryptographic operation can be requested).
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.Pp
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Keying operations are supported as well.
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Unlike the symmetric operators described above,
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these sessionless commands perform mathematical operations using
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input and output parameters.
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.Pp
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Since the consumers may not be associated with a process, drivers may
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not
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.Xr sleep 9 .
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The same holds for the framework.
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Thus, a callback mechanism is used
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to notify a consumer that a request has been completed (the
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callback is specified by the consumer on an per-request basis).
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The callback is invoked by the framework whether the request was
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successfully completed or not.
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An error indication is provided in the latter case.
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A specific error code,
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.Er EAGAIN ,
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is used to indicate that a session number has changed and that the
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request may be re-submitted immediately with the new session number.
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Errors are only returned to the invoking function if not
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enough information to call the callback is available (meaning, there
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was a fatal error in verifying the arguments).
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For session initialization and teardown there is no callback mechanism used.
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.Pp
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The
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.Fn crypto_newsession
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routine is called by consumers of cryptographic services (such as the
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.Xr ipsec 4
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stack) that wish to establish a new session with the framework.
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On success, the first argument will contain the Session Identifier (SID).
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The second argument contains all the necessary information for
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the driver to establish the session.
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The third argument indicates whether a
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hardware driver (1) should be used or not (0).
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The various fields in the
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.Vt cryptoini
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structure are:
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.Bl -tag -width ".Va cri_next"
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.It Va cri_alg
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Contains an algorithm identifier.
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Currently supported algorithms are:
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.Pp
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.Bl -tag -width ".Dv CRYPTO_RIPEMD160_HMAC" -compact
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.It Dv CRYPTO_DES_CBC
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.It Dv CRYPTO_3DES_CBC
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.It Dv CRYPTO_BLF_CBC
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.It Dv CRYPTO_CAST_CBC
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.It Dv CRYPTO_SKIPJACK_CBC
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.It Dv CRYPTO_MD5_HMAC
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.It Dv CRYPTO_SHA1_HMAC
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.It Dv CRYPTO_RIPEMD160_HMAC
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.It Dv CRYPTO_MD5_KPDK
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.It Dv CRYPTO_SHA1_KPDK
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.It Dv CRYPTO_AES_CBC
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.It Dv CRYPTO_ARC4
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.It Dv CRYPTO_MD5
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.It Dv CRYPTO_SHA1
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.It Dv CRYPTO_SHA2_256_HMAC
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.It Dv CRYPTO_SHA2_384_HMAC
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.It Dv CRYPTO_SHA2_512_HMAC
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.It Dv CRYPTO_NULL_HMAC
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.It Dv CRYPTO_NULL_CBC
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.El
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.It Va cri_klen
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Specifies the length of the key in bits, for variable-size key
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algorithms.
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.It Va cri_mlen
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Specifies how many bytes from the calculated hash should be copied back.
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0 means entire hash.
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.It Va cri_key
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Contains the key to be used with the algorithm.
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.It Va cri_iv
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Contains an explicit initialization vector (IV), if it does not prefix
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the data.
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This field is ignored during initialization.
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If no IV is explicitly passed (see below on details), a random IV is used
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by the device driver processing the request.
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.It Va cri_next
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Contains a pointer to another
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.Vt cryptoini
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structure.
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Multiple such structures may be linked to establish multi-algorithm sessions
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.Xr ( ipsec 4
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is an example consumer of such a feature).
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.El
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.Pp
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The
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.Vt cryptoini
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structure and its contents will not be modified by the framework (or
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the drivers used).
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Subsequent requests for processing that use the
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SID returned will avoid the cost of re-initializing the hardware (in
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essence, SID acts as an index in the session cache of the driver).
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.Pp
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.Fn crypto_freesession
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is called with the SID returned by
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.Fn crypto_newsession
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to disestablish the session.
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.Pp
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.Fn crypto_dispatch
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is called to process a request.
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The various fields in the
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.Vt cryptop
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structure are:
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.Bl -tag -width ".Va crp_callback"
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.It Va crp_sid
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Contains the SID.
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.It Va crp_ilen
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Indicates the total length in bytes of the buffer to be processed.
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.It Va crp_olen
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On return, contains the total length of the result.
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For symmetric crypto operations, this will be the same as the input length.
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This will be used if the framework needs to allocate a new
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buffer for the result (or for re-formatting the input).
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.It Va crp_callback
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This routine is invoked upon completion of the request, whether
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successful or not.
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It is invoked through the
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.Fn crypto_done
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routine.
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If the request was not successful, an error code is set in the
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.Va crp_etype
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field.
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It is the responsibility of the callback routine to set the appropriate
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.Xr spl 9
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level.
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.It Va crp_etype
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Contains the error type, if any errors were encountered, or zero if
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the request was successfully processed.
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If the
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.Er EAGAIN
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error code is returned, the SID has changed (and has been recorded in the
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.Va crp_sid
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field).
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The consumer should record the new SID and use it in all subsequent requests.
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In this case, the request may be re-submitted immediately.
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This mechanism is used by the framework to perform
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session migration (move a session from one driver to another, because
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of availability, performance, or other considerations).
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.Pp
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Note that this field only makes sense when examined by
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the callback routine specified in
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.Va crp_callback .
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Errors are returned to the invoker of
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.Fn crypto_process
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only when enough information is not present to call the callback
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routine (i.e., if the pointer passed is
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.Dv NULL
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or if no callback routine was specified).
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.It Va crp_flags
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Is a bitmask of flags associated with this request.
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Currently defined flags are:
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.Bl -tag -width ".Dv CRYPTO_F_CBIFSYNC"
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.It Dv CRYPTO_F_IMBUF
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The buffer pointed to by
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.Va crp_buf
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is an mbuf chain.
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.It Dv CRYPTO_F_IOV
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The buffer pointed to by
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.Va crp_buf
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is an uio structure.
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.It Dv CRYPTO_F_REL
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Must return data in the same place.
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.It Dv CRYPTO_F_BATCH
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Batch operation if possible.
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.It Dv CRYPTO_F_CBIMM
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Do callback immediatelly instead of doing it from a dedicated kernel thread.
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.It Dv CRYPTO_F_DONE
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Operation completed.
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.It Dv CRYPTO_F_CBIFSYNC
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Do callback immediatelly if operation is synchronous.
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.El
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.It Va crp_buf
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Points to the input buffer.
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On return (when the callback is invoked),
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it contains the result of the request.
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The input buffer may be an mbuf
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chain or a contiguous buffer,
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depending on
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.Va crp_flags .
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.It Va crp_opaque
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This is passed through the crypto framework untouched and is
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intended for the invoking application's use.
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.It Va crp_desc
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This is a linked list of descriptors.
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Each descriptor provides
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information about what type of cryptographic operation should be done
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on the input buffer.
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The various fields are:
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.Bl -tag -width ".Va crd_inject"
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.It Va crd_iv
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The field where IV should be provided when the
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.Dv CRD_F_IV_EXPLICIT
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flag is given.
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.It Va crd_key
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When the
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.Dv CRD_F_KEY_EXPLICIT
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flag is given, the
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.Va crd_key
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points to a buffer with encryption or authentication key.
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.It Va crd_alg
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An algorithm to use.
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Must be the same as the one given at newsession time.
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.It Va crd_klen
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The
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.Va crd_key
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key length.
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.It Va crd_skip
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The offset in the input buffer where processing should start.
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.It Va crd_len
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How many bytes, after
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.Va crd_skip ,
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should be processed.
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.It Va crd_inject
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Offset from the beginning of the buffer to insert any results.
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For encryption algorithms, this is where the initialization vector
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(IV) will be inserted when encrypting or where it can be found when
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decrypting (subject to
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.Va crd_flags ) .
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For MAC algorithms, this is where the result of the keyed hash will be
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inserted.
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.It Va crd_flags
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The following flags are defined:
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.Bl -tag -width ".Dv CRD"
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.It Dv CRD_F_ENCRYPT
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For encryption algorithms, this bit is set when encryption is required
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(when not set, decryption is performed).
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.It Dv CRD_F_IV_PRESENT
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For encryption algorithms, this bit is set when the IV already
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precedes the data, so the
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.Va crd_inject
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value will be ignored and no IV will be written in the buffer.
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Otherwise, the IV used to encrypt the packet will be written
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at the location pointed to by
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.Va crd_inject .
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The IV length is assumed to be equal to the blocksize of the
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encryption algorithm.
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Some applications that do special
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.Dq "IV cooking" ,
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such as the half-IV mode in
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.Xr ipsec 4 ,
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can use this flag to indicate that the IV should not be written on the packet.
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This flag is typically used in conjunction with the
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.Dv CRD_F_IV_EXPLICIT
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flag.
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.It Dv CRD_F_IV_EXPLICIT
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For encryption algorithms, this bit is set when the IV is explicitly
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provided by the consumer in the
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.Va crd_iv
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field.
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Otherwise, for encryption operations the IV is provided for by
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the driver used to perform the operation, whereas for decryption
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operations it is pointed to by the
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.Va crd_inject
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field.
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This flag is typically used when the IV is calculated
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.Dq "on the fly"
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by the consumer, and does not precede the data (some
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.Xr ipsec 4
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configurations, and the encrypted swap are two such examples).
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.It Dv CRD_F_KEY_EXPLICIT
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For encryption and authentication (MAC) algorithms, this bit is set when the key
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is explicitly provided by the consumer in the
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.Va crd_key
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field for the given operation.
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Otherwise, the key is taken at newsession time from the
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.Va cri_key
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field.
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.It Dv CRD_F_COMP
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For compression algorithms, this bit is set when compression is required (when
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not set, decompression is performed).
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.El
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.It Va CRD_INI
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This
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.Vt cryptoini
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structure will not be modified by the framework or the device drivers.
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Since this information accompanies every cryptographic
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operation request, drivers may re-initialize state on-demand
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(typically an expensive operation).
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Furthermore, the cryptographic
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framework may re-route requests as a result of full queues or hardware
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failure, as described above.
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.It Va crd_next
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Point to the next descriptor.
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Linked operations are useful in protocols such as
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.Xr ipsec 4 ,
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where multiple cryptographic transforms may be applied on the same
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block of data.
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.El
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.El
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.Pp
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.Fn crypto_getreq
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allocates a
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.Vt cryptop
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structure with a linked list of as many
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.Vt cryptodesc
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structures as were specified in the argument passed to it.
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.Pp
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.Fn crypto_freereq
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deallocates a structure
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.Vt cryptop
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and any
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.Vt cryptodesc
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structures linked to it.
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Note that it is the responsibility of the
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callback routine to do the necessary cleanups associated with the
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opaque field in the
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.Vt cryptop
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structure.
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.Pp
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.Fn crypto_kdispatch
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is called to perform a keying operation.
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The various fields in the
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.Vt cryptkop
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structure are:
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.Bl -tag -width ".Va krp_callback'
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.It Va krp_op
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Operation code, such as
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.Dv CRK_MOD_EXP .
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.It Va krp_status
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Return code.
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This
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.Va errno Ns -style
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variable indicates whether lower level reasons
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for operation failure.
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.It Va krp_iparams
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Number if input parameters to the specified operation.
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Note that each operation has a (typically hardwired) number of such parameters.
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.It Va krp_oparams
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Number if output parameters from the specified operation.
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Note that each operation has a (typically hardwired) number of such parameters.
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.It Va krp_kvp
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An array of kernel memory blocks containing the parameters.
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.It Va krp_hid
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Identifier specifying which low-level driver is being used.
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.It Va krp_callback
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Callback called on completion of a keying operation.
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.El
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.Sh DRIVER-SIDE API
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The
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.Fn crypto_get_driverid ,
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.Fn crypto_register ,
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.Fn crypto_kregister ,
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.Fn crypto_unregister ,
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.Fn crypto_unblock ,
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and
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.Fn crypto_done
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routines are used by drivers that provide support for cryptographic
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primitives to register and unregister with the kernel crypto services
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framework.
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Drivers must first use the
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.Fn crypto_get_driverid
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function to acquire a driver identifier, specifying the
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.Fa cc_flags
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as an argument (normally 0, but software-only drivers should specify
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.Dv CRYPTOCAP_F_SOFTWARE ) .
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For each algorithm the driver supports, it must then call
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.Fn crypto_register .
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The first two arguments are the driver and algorithm identifiers.
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The next two arguments specify the largest possible operator length (in bits,
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important for public key operations) and flags for this algorithm.
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The last four arguments must be provided in the first call to
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.Fn crypto_register
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|
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.
|
|
.Fn crypto_unregister
|
|
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.
|
|
.Fn crypto_unregister_all
|
|
will unregister all algorithms registered by a driver
|
|
and the driver will be disabled (no new sessions will be allocated on
|
|
that driver, and any existing sessions will be migrated to other
|
|
drivers).
|
|
The same will be done if all algorithms associated with a driver are
|
|
unregistered one by one.
|
|
.Pp
|
|
The calling convention for the three driver-supplied routines is:
|
|
.Pp
|
|
.Bl -item -compact
|
|
.It
|
|
.Ft int
|
|
.Fn \*[lp]*newsession\*[rp] "void *" "u_int32_t *" "struct cryptoini *" ;
|
|
.It
|
|
.Ft int
|
|
.Fn \*[lp]*freesession\*[rp] "void *" "u_int64_t" ;
|
|
.It
|
|
.Ft int
|
|
.Fn \*[lp]*process\*[rp] "void *" "struct cryptop *" ;
|
|
.It
|
|
.Ft int
|
|
.Fn \*[lp]*kprocess\*[rp] "void *" "struct cryptkop *" ;
|
|
.El
|
|
.Pp
|
|
On invocation, the first argument to
|
|
all routines is an opaque data value supplied when the algorithm
|
|
is registered with
|
|
.Fn crypto_register .
|
|
The second argument to
|
|
.Fn newsession
|
|
contains the driver identifier obtained via
|
|
.Fn crypto_get_driverid .
|
|
On successful return, it should contain a driver-specific session
|
|
identifier.
|
|
The third argument is identical to that of
|
|
.Fn crypto_newsession .
|
|
.Pp
|
|
The
|
|
.Fn freesession
|
|
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 associated with the session (clear hardware
|
|
registers, memory, etc.).
|
|
.Pp
|
|
The
|
|
.Fn 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 an unrecoverable error, the error indication must be placed in the
|
|
.Va crp_etype
|
|
field of the
|
|
.Vt cryptop
|
|
structure.
|
|
When the request is completed, or an error is detected, the
|
|
.Fn process
|
|
routine should invoke
|
|
.Fn crypto_done .
|
|
Session migration may be performed, as mentioned previously.
|
|
.Pp
|
|
In case of a temporary resource exhaustion, the
|
|
.Fn process
|
|
routine may return
|
|
.Er ERESTART
|
|
in which case the crypto services will requeue the request, mark the driver
|
|
as
|
|
.Dq blocked ,
|
|
and stop submitting requests for processing.
|
|
The driver is then responsible for notifying the crypto services
|
|
when it is again able to process requests through the
|
|
.Fn crypto_unblock
|
|
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.
|
|
.Pp
|
|
The
|
|
.Fn 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 an unrecoverable error, the error indication must be placed in the
|
|
.Va krp_status
|
|
field of the
|
|
.Vt cryptkop
|
|
structure.
|
|
When the request is completed, or an error is detected, the
|
|
.Fn kprocess
|
|
routine should invoked
|
|
.Fn crypto_kdone .
|
|
.Sh RETURN VALUES
|
|
.Fn crypto_register ,
|
|
.Fn crypto_kregister ,
|
|
.Fn crypto_unregister ,
|
|
.Fn crypto_newsession ,
|
|
.Fn crypto_freesession ,
|
|
and
|
|
.Fn crypto_unblock
|
|
return 0 on success, or an error code on failure.
|
|
.Fn crypto_get_driverid
|
|
returns a non-negative value on error, and \-1 on failure.
|
|
.Fn crypto_getreq
|
|
returns a pointer to a
|
|
.Vt cryptop
|
|
structure and
|
|
.Dv NULL
|
|
on failure.
|
|
.Fn crypto_dispatch
|
|
returns
|
|
.Er EINVAL
|
|
if its argument or the callback function was
|
|
.Dv NULL ,
|
|
and 0 otherwise.
|
|
The callback is provided with an error code in case of failure, in the
|
|
.Va crp_etype
|
|
field.
|
|
.Sh FILES
|
|
.Bl -tag -width ".Pa sys/opencrypto/crypto.c"
|
|
.It Pa sys/opencrypto/crypto.c
|
|
most of the framework code
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr ipsec 4 ,
|
|
.Xr malloc 9 ,
|
|
.Xr sleep 9
|
|
.Sh HISTORY
|
|
The cryptographic framework first appeared in
|
|
.Ox 2.7
|
|
and was written by
|
|
.An "Angelos D. Keromytis" Aq angelos@openbsd.org .
|
|
.Sh BUGS
|
|
The framework currently assumes that all the algorithms in a
|
|
.Fn crypto_newsession
|
|
operation must be available by the same driver.
|
|
If that is not the case, session initialization will fail.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
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.
|