CRYPTO(4) FreeBSD Kernel Interfaces Manual CRYPTO(4)
NAME
crypto, cryptodev - user-mode access to hardware-accelerated cryptography
SYNOPSIS
device crypto
device cryptodev
#include <sys/ioctl.h>
#include <sys/time.h>
#include <crypto/cryptodev.h>
DESCRIPTION
The crypto driver gives user-mode applications access to hardware-
accelerated cryptographic transforms as implemented by the crypto(9) in-
kernel interface.
The /dev/crypto special device provides an ioctl(2) based interface.
User-mode applications open the special device and then issue ioctl(2)
calls on the descriptor. User-mode access to /dev/crypto is controlled
by the kern.cryptodevallowsoft sysctl(8) variable. If this variable is
zero, then user-mode sessions are only permitted to use cryptography
coprocessors.
THEORY OF OPERATION
Use of the device requires a basic series of steps:
1. Open the /dev/crypto device.
2. Create a session with CIOCGSESSION or CIOCGSESSION2. Applications
will require at least one symmetric session. Since cipher and MAC
keys are tied to sessions, many applications will require more.
3. Submit requests, synchronously with CIOCCRYPT or CIOCCRYPTAEAD.
4. Optionally destroy a session with CIOCFSESSION.
5. Close the /dev/crypto device. This will automatically close any
remaining sessions associated with the file descriptor.
SYMMETRIC-KEY OPERATION
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.
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.
Algorithms
For a list of supported algorithms, see crypto(7).
IOCTL Request Descriptions
CIOCFINDDEV struct crypt_find_op *fop
struct crypt_find_op {
int crid; /* driver id + flags */
char name[32]; /* device/driver name */
};
If crid is -1, then find the driver named name and return
the id in crid. If crid is not -1, return the name of the
driver with crid in name. In either case, if the driver is
not found, ENOENT is returned.
CIOCGSESSION struct session_op *sessp
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 # */
};
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 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.
Multiple sessions may be bound to a single file descriptor.
The session ID returned in sessp->ses is supplied as a
required field in the operation structure crypt_op for
future encryption or hashing requests.
For non-zero privacy algorithms, the privacy algorithm must
be specified in sessp->cipher, the key length in
sessp->keylen, and the key value in the octets addressed by
sessp->key.
For keyed one-way hash algorithms, the one-way hash must be
specified in sessp->mac, the key length in sessp->mackey,
and the key value in the octets addressed by
sessp->mackeylen.
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.
CIOCGSESSION2 struct session2_op *sessp
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 */
};
This request is similar to CIOGSESSION but adds additional
fields.
sessp->crid requests either a specific crypto device or a
class of devices (software vs hardware).
sessp->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.
sessp->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.
The sessp->pad field must be initialized to zero.
CIOCCRYPT struct crypt_op *cr_op
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;
};
Request an encryption/decryption (or hash) operation. To
encrypt, set cr_op->op to COP_ENCRYPT. To decrypt, set
cr_op->op to COP_DECRYPT. The field cr_op->len supplies
the length of the input buffer; the fields cr_op->src,
cr_op->dst, cr_op->mac, cr_op->iv supply the addresses of
the input buffer, output buffer, one-way hash, and
initialization vector, respectively.
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 EBADMSG and the
output buffer will remain unchanged.
CIOCCRYPTAEAD struct crypt_aead *cr_aead
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;
};
The CIOCCRYPTAEAD is similar to the CIOCCRYPT but provides
additional data in cr_aead->aad to include in the
authentication mode.
CIOCFSESSION u_int32_t ses_id
Destroys the session identified by ses_id.
SEE ALSO
aesni(4), armv8crypto(4), ccr(4), glxsb(4), hifn(4), ipsec(4),
padlock(4), qat(4), qat_c2xxx(4), safe(4), safexcel(4), crypto(7),
geli(8), crypto(9)
HISTORY
The crypto driver first appeared in OpenBSD 3.0. The crypto driver was
imported to FreeBSD 5.0.
BUGS
Error checking and reporting is weak.
The values specified for symmetric-key key sizes to CIOCGSESSION must
exactly match the values expected by opencrypto(9). The output buffer
and MAC buffers supplied to CIOCCRYPT must follow whether privacy or
integrity algorithms were specified for session: if you request a
non-NULL algorithm, you must supply a suitably-sized buffer.
FreeBSD 15.1-STABLE-HBSD May 17, 2026 CRYPTO(4)