Re: comparison of the AF_ALG interface with the /dev/crypto

From: Nikos Mavrogiannopoulos <redacted>
Date: Sun, 28 Aug 2011 15:17:00 +0200

The benchmark idea was to test the speed of initialization, encryption
and deinitiation, as well as the encryption speed alone. These are the
most common use cases of the frameworks (i.e. how they would be used
by a cryptographic library).

Be sure to use splice() with AF_ALG for maximum performance.

For example, see the test program below.  You'll need to replace
"8192" with whatever the page size is on your cpu.

--------------------
#include <fcntl.h>
#include <openssl/aes.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <linux/types.h>

#define AF_ALG 38
#define SOL_ALG 279

#define SPLICE_F_GIFT	(0x08)	/* pages passed in are a gift */

struct sockaddr_alg {
	__u16	salg_family;
	__u8	salg_type[14];
	__u32	salg_feat;
	__u32	salg_mask;
	__u8	salg_name[64];
};

struct af_alg_iv {
	__u32	ivlen;
	__u8	iv[0];
};

/* Socket options */
#define ALG_SET_KEY			1
#define ALG_SET_IV			2
#define ALG_SET_OP			3

/* Operations */
#define ALG_OP_DECRYPT			0
#define ALG_OP_ENCRYPT			1

static char buf[8192] __attribute__((__aligned__(8192)));

static void crypt_ssl(const char *key, char *iv, int i)
{
	AES_KEY akey;

	AES_set_encrypt_key(key, 128, &akey);

	while (i--)
		AES_cbc_encrypt(buf, buf, 8192, &akey, iv, 1);
}

static void crypt_kernel(const char *key, char *oiv, int i)
{
	int opfd;
	int tfmfd;
	struct sockaddr_alg sa = {
		.salg_family = AF_ALG,
		.salg_type = "skcipher",
		.salg_name = "cbc(aes)"
	};
	struct msghdr msg = {};
	struct cmsghdr *cmsg;
	char cbuf[CMSG_SPACE(4) + CMSG_SPACE(20)] = {};
	struct aes_iv {
		__u32 len;
		__u8 iv[16];
	} *iv;
	struct iovec iov;
	int pipes[2];

	pipe(pipes);

	tfmfd = socket(AF_ALG, SOCK_SEQPACKET, 0);

	bind(tfmfd, (struct sockaddr *)&sa, sizeof(sa));

	setsockopt(tfmfd, SOL_ALG, ALG_SET_KEY, key, 16);

	opfd = accept(tfmfd, NULL, 0);

	msg.msg_control = cbuf;
	msg.msg_controllen = sizeof(cbuf);

	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_ALG;
	cmsg->cmsg_type = ALG_SET_OP;
	cmsg->cmsg_len = CMSG_LEN(4);
	*(__u32 *)CMSG_DATA(cmsg) = ALG_OP_ENCRYPT;

	cmsg = CMSG_NXTHDR(&msg, cmsg);
	cmsg->cmsg_level = SOL_ALG;
	cmsg->cmsg_type = ALG_SET_IV;
	cmsg->cmsg_len = CMSG_LEN(20);
	iv = (void *)CMSG_DATA(cmsg);
	iv->len = 16;
	memcpy(iv->iv, oiv, 16);

	iov.iov_base = buf;
	iov.iov_len = 8192;

	msg.msg_iovlen = 0;
	msg.msg_flags = MSG_MORE;

	while (i--) {
		sendmsg(opfd, &msg, 0);
		vmsplice(pipes[1], &iov, 1, SPLICE_F_GIFT);
		splice(pipes[0], NULL, opfd, NULL, 8192, 0);
		read(opfd, buf, 8192);
	}

	close(opfd);
	close(tfmfd);
	close(pipes[0]);
	close(pipes[1]);
}

int main(int argc, char **argv)
{
	int i;

	const char key[16] =
		"\x06\xa9\x21\x40\x36\xb8\xa1\x5b"
		"\x51\x2e\x03\xd5\x34\x12\x00\x06";
	char iv[16] = 
		"\x3d\xaf\xba\x42\x9d\x9e\xb4\x30"
		"\xb4\x22\xda\x80\x2c\x9f\xac\x41";
	
	memcpy(buf, "Single block msg", 16);

	if (argc > 1)
		crypt_ssl(key, iv, 1024 * 1024);
	else
		crypt_kernel(key, iv, 1024 * 1024);

	for (i = 0; i < 8192; i++) {
		printf("%02x", (unsigned char)buf[i]);
	}
	printf("\n");

	return 0;
}