NAME
crypto —
API for cryptographic services in the
kernel
SYNOPSIS
#include
<opencrypto/cryptodev.h>
DESCRIPTION
crypto is a framework for in-kernel cryptography. It
permits in-kernel consumers to encrypt and decrypt data and also enables
userland applications to use cryptographic hardware through the
/dev/crypto device.
crypto supports two modes of operation:
one mode for symmetric-keyed cryptographic requests and digest, and a second
mode for asymmetric-key requests and modular arithmetic.
Symmetric-Key Mode
Symmetric-key operations include encryption and decryption operations using block and stream ciphers as well as computation and verification of message authentication codes (MACs). In this mode, consumers allocate sessions to describe a transform as discussed in crypto_session(9). Consumers then allocate request objects to describe each transformation such as encrypting a network packet or decrypting a disk sector. Requests are described in crypto_request(9).
Device drivers are responsible for processing requests submitted by consumers. crypto_driver(9) describes the interfaces drivers use to register with the framework, helper routines the framework provides to faciliate request processing, and the interfaces drivers are required to provide.
Asymmetric-Key Mode
Assymteric-key operations do not use sessions. Instead, these operations perform individual mathematical operations using a set of input and output parameters. These operations are described in crypto_asym(9). Drivers that support asymmetric operations use additional interfaces described in crypto_asym(9) in addition to the base interfaces described in crypto_driver(9).
Callbacks
Since the consumers may not be associated with a process, drivers may not sleep(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 a per-request basis). The callback is invoked by the framework whether the request was successfully completed or not. Errors are reported to the callback function.
Session initialization does not use callbacks and returns errors synchronously.
Session Migration
For symmetric-key operations, a specific error code,
EAGAIN, is used to indicate that a session handle
has changed and that the request may be re-submitted immediately with the
new session. The consumer should update its saved copy of the session handle
to the value of crp_session so that future requests
use the new session.
Supported Algorithms
More details on some algorithms may be found in crypto(7). These algorithms are used for symmetric-mode operations. Asymmetric-mode operations support operations described in crypto_asym(9).
The following authentication algorithms are supported:
CRYPTO_AES_CCM_CBC_MACCRYPTO_AES_NIST_GMACCRYPTO_BLAKE2BCRYPTO_BLAKE2SCRYPTO_NULL_HMACCRYPTO_POLY1305CRYPTO_RIPEMD160CRYPTO_RIPEMD160_HMACCRYPTO_SHA1CRYPTO_SHA1_HMACCRYPTO_SHA2_224CRYPTO_SHA2_224_HMACCRYPTO_SHA2_256CRYPTO_SHA2_256_HMACCRYPTO_SHA2_384CRYPTO_SHA2_384_HMACCRYPTO_SHA2_512CRYPTO_SHA2_512_HMAC
The following encryption algorithms are supported:
The following authenticated encryption with additional data (AEAD) algorithms are supported:
The following compression algorithms are supported:
FILES
- sys/opencrypto/crypto.c
- most of the framework code
SEE ALSO
crypto(4), ipsec(4), crypto(7), crypto_asym(9), crypto_driver(9), crypto_request(9), crypto_session(9), sleep(9)
HISTORY
The cryptographic framework first appeared in OpenBSD 2.7 and was written by Angelos D. Keromytis <angelos@openbsd.org>.
BUGS
The framework 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.