path: root/share/man/man4/crypto.4

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.Dd October 6, 2021
.Dt CRYPTO 4
.Os
.Sh NAME
.Nm crypto ,
.Nm cryptodev
.Nd user-mode access to hardware-accelerated cryptography
.Sh SYNOPSIS
.Cd device crypto
.Cd device cryptodev
.Pp
.In sys/ioctl.h
.In sys/time.h
.In crypto/cryptodev.h
.Sh DESCRIPTION
The
.Nm
driver gives user-mode applications access to hardware-accelerated
cryptographic transforms as implemented by the
.Xr crypto 9
in-kernel interface.
.Pp
The
.Pa /dev/crypto
special device provides an
.Xr ioctl 2
based interface.
User-mode applications open the special device and
then issue
.Xr ioctl 2
calls on the descriptor.
User-mode access to
.Pa /dev/crypto
is controlled by the
.Ic kern.cryptodevallowsoft
.Xr sysctl 8
variable.
If this variable is zero,
then user-mode sessions are only permitted to use cryptography coprocessors.
.Sh THEORY OF OPERATION
Use of the device requires a basic series of steps:
.Bl -enum
.It
Open the
.Pa /dev/crypto
device.
.It
Create a session with
.Dv CIOCGSESSION
or
.Dv CIOCGSESSION2 .
Applications will require at least one symmetric session.
Since cipher and MAC keys are tied to sessions, many
applications will require more.
.It
Submit requests, synchronously with
.Dv CIOCCRYPT
or
.Dv CIOCCRYPTAEAD .
.It
Optionally destroy a session with
.Dv CIOCFSESSION .
.It
Close the
.Pa /dev/crypto
device.
This will automatically close any remaining sessions associated with the
file desriptor.
.El
.Sh SYMMETRIC-KEY OPERATION
.Nm cryptodev
provides a context-based API
to traditional symmetric-key encryption (or privacy) algorithms,
keyed and unkeyed one-way hash (HMAC and MAC) algorithms,
encrypt-then-authenticate (ETA) fused operations,
and authenticated encryption with additional data (AEAD) operations.
For ETA operations,
drivers perform both a privacy algorithm and an integrity-check
algorithm in a single pass over the data: either a fused
encrypt/HMAC-generate operation, or a fused HMAC-verify/decrypt operation.
Similarly, for AEAD operations,
drivers perform either an encrypt/MAC-generate operation
or a MAC-verify/decrypt operation.
.Pp
The algorithm(s) and key(s) to use are specified when a session is
created.
Individual requests are able to specify per-request initialization vectors
or nonces.
.Ss Algorithms
For a list of supported algorithms, see
.Xr crypto 7 .
.Ss IOCTL Request Descriptions
.\"
.Bl -tag -width CIOCGSESSION
.\"
.It Dv CIOCFINDDEV Fa struct crypt_find_op *fop
.Bd -literal
struct crypt_find_op {
    int     crid;       /* driver id + flags */
    char    name[32];   /* device/driver name */
};

.Ed
If
.Fa crid
is -1, then find the driver named
.Fa name
and return the id in
.Fa crid .
If
.Fa crid
is not -1, return the name of the driver with
.Fa crid
in
.Fa name .
In either case, if the driver is not found,
.Dv ENOENT
is returned.
.It Dv CIOCGSESSION Fa struct session_op *sessp
.Bd -literal
struct session_op {
    uint32_t cipher;	/* e.g. CRYPTO_AES_CBC */
    uint32_t mac;	/* e.g. CRYPTO_SHA2_256_HMAC */

    uint32_t keylen;	/* cipher key */
    const void *key;
    int mackeylen;	/* mac key */
    const void *mackey;

    uint32_t ses;	/* returns: ses # */
};

.Ed
Create a new cryptographic session on a file descriptor for the device;
that is, a persistent object specific to the chosen
privacy algorithm, integrity algorithm, and keys specified in
.Fa sessp .
The special value 0 for either privacy or integrity
is reserved to indicate that the indicated operation (privacy or integrity)
is not desired for this session.
ETA sessions specify both privacy and integrity algorithms.
AEAD sessions specify only a privacy algorithm.
.Pp
Multiple sessions may be bound to a single file descriptor.
The session ID returned in
.Fa sessp-\*[Gt]ses
is supplied as a required field in the operation structure
.Fa crypt_op
for future encryption or hashing requests.
.\" .Pp
.\" This implementation will never return a session ID of 0 for a successful
.\" creation of a session, which is a
.\" .Nx
.\" extension.
.Pp
For non-zero privacy algorithms, the privacy algorithm
must be specified in
.Fa sessp-\*[Gt]cipher ,
the key length in
.Fa sessp-\*[Gt]keylen ,
and the key value in the octets addressed by
.Fa sessp-\*[Gt]key .
.Pp
For keyed one-way hash algorithms, the one-way hash must be specified
in
.Fa sessp-\*[Gt]mac ,
the key length in
.Fa sessp-\*[Gt]mackey ,
and the key value in the octets addressed by
.Fa sessp-\*[Gt]mackeylen .
.\"
.Pp
Support for a specific combination of fused privacy and
integrity-check algorithms depends on whether the underlying
hardware supports that combination.
Not all combinations are supported
by all hardware, even if the hardware supports each operation as a
stand-alone non-fused operation.
.It Dv CIOCGSESSION2 Fa struct session2_op *sessp
.Bd -literal
struct session2_op {
    uint32_t cipher;	/* e.g. CRYPTO_AES_CBC */
    uint32_t mac;	/* e.g. CRYPTO_SHA2_256_HMAC */

    uint32_t keylen;	/* cipher key */
    const void *key;
    int mackeylen;	/* mac key */
    const void *mackey;

    uint32_t ses;	/* returns: ses # */
    int	crid;		/* driver id + flags (rw) */
    int ivlen;		/* length of nonce/IV */
    int maclen;		/* length of MAC/tag */
    int	pad[2];		/* for future expansion */
};

.Ed
This request is similar to CIOGSESSION but adds additional fields.
.Pp
.Fa sessp-\*[Gt]crid
requests either a specific crypto device or a class of devices (software vs
hardware).
.Pp
.Fa sessp-\*[Gt]ivlen
specifies the length of the IV or nonce supplied with each request.
If this field is set to zero, the default IV or nonce length is used.
.Pp
.Fa sessp-\*[Gt]maclen
specifies the length of the MAC or authentication tag supplied or computed by
each request.
If this field is set to zero, the full MAC is used.
.Pp
The
.Fa sessp-\*[Gt]pad
field must be initialized to zero.
.It Dv CIOCCRYPT Fa struct crypt_op *cr_op
.Bd -literal
struct crypt_op {
    uint32_t ses;
    uint16_t op;	/* e.g. COP_ENCRYPT */
    uint16_t flags;
    u_int len;
    const void *src;
    void *dst;
    void *mac;		/* must be large enough for result */
    const void *iv;
};

.Ed
Request an encryption/decryption (or hash) operation.
To encrypt, set
.Fa cr_op-\*[Gt]op
to
.Dv COP_ENCRYPT .
To decrypt, set
.Fa cr_op-\*[Gt]op
to
.Dv COP_DECRYPT .
The field
.Fa cr_op-\*[Gt]len
supplies the length of the input buffer; the fields
.Fa cr_op-\*[Gt]src ,
.Fa cr_op-\*[Gt]dst ,
.Fa cr_op-\*[Gt]mac ,
.Fa cr_op-\*[Gt]iv
supply the addresses of the input buffer, output buffer,
one-way hash, and initialization vector, respectively.
.Pp
If a session is using either fused encrypt-then-authenticate or
an AEAD algorithm,
decryption operations require the associated hash as an input.
If the hash is incorrect, the
operation will fail with
.Dv EBADMSG
and the output buffer will remain unchanged.
.It Dv CIOCCRYPTAEAD Fa struct crypt_aead *cr_aead
.Bd -literal
struct crypt_aead {
    uint32_t ses;
    uint16_t op;	/* e.g. COP_ENCRYPT */
    uint16_t flags;
    u_int len;
    u_int aadlen;
    u_int ivlen;
    const void *src;
    void *dst;
    const void *aad;	/* additional authenticated data */
    void *tag;		/* must fit for chosen TAG length */
    const void *iv;
};

.Ed
The
.Dv CIOCCRYPTAEAD
is similar to the
.Dv CIOCCRYPT
but provides additional data in
.Fa cr_aead-\*[Gt]aad
to include in the authentication mode.
.It Dv CIOCFSESSION Fa u_int32_t ses_id
Destroys the session identified by
.Fa ses_id .
.El
.Sh SEE ALSO
.Xr aesni 4 ,
.Xr hifn 4 ,
.Xr ipsec 4 ,
.Xr padlock 4 ,
.Xr safe 4 ,
.Xr crypto 7 ,
.Xr geli 8 ,
.Xr crypto 9
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 3.0 .
The
.Nm
driver was imported to
.Fx 5.0 .
.Sh BUGS
Error checking and reporting is weak.
.Pp
The values specified for symmetric-key key sizes to
.Dv CIOCGSESSION
must exactly match the values expected by
.Xr opencrypto 9 .
The output buffer and MAC buffers supplied to
.Dv CIOCCRYPT
must follow whether privacy or integrity algorithms were specified for
session: if you request a
.No non- Ns Dv NULL
algorithm, you must supply a suitably-sized buffer.