#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/syscall.h>

typedef int32_t key_serial_t;

#ifndef __i386__
#error Sorry, currently only works on i386
#endif

#ifndef __NR_add_key
#define __NR_add_key	286
#endif

/* special process keyring shortcut IDs */
#define KEY_SPEC_THREAD_KEYRING		-1
#define KEY_SPEC_PROCESS_KEYRING	-2
#define KEY_SPEC_SESSION_KEYRING	-3
#define KEY_SPEC_USER_KEYRING		-4
#define KEY_SPEC_USER_SESSION_KEYRING	-5
#define KEY_SPEC_GROUP_KEYRING		-6

static inline key_serial_t
add_key(const char *type, const char * description, const void *payload,
        size_t plen, key_serial_t ringid)
{
	syscall(__NR_add_key, type, description, payload, plen, ringid);
}

/*
 * Decode key from its hex representation
 */
static int crypt_decode_key(uint8_t *key, char *hex, unsigned int size)
{
	char buffer[3];
	char *endp;
	unsigned int i;

	buffer[2] = '\0';

	for(i = 0; i < size; i++) {
		buffer[0] = *hex++;
		buffer[1] = *hex++;

		key[i] = (uint8_t)strtoul(buffer, &endp, 16);

		if (endp != &buffer[2])
			return -EINVAL;
	}

	if (*hex != '\0')
		return -EINVAL;

	return 0;
}

int main(int argc, char **argv)
{
	unsigned int key_size;
	size_t buflen;
	void *buf, *p;
	long ret;
	uint8_t *key = NULL;

	if (argc != 4) {
		fprintf(stderr, "Syntax: %s key-name crypto-config hex-key\n",
		        argv[0]);
		return 1;
	}

	key_size = strlen(argv[3]) >> 1;
	if (key_size > 1024) {
		fprintf(stderr, "Invalid key size.\n");
		return 1;
	}

	if (!key_size && strcmp(argv[3], "-") != 0) {
		fprintf(stderr, "Key invalid.\n");
		return 1;
	}

	if (key_size) {
		key = malloc(key_size * sizeof(uint8_t));
		if (crypt_decode_key(key, argv[3], key_size) < 0) {
			fprintf(stderr, "Error decoding key.\n");
			return 1;
		}
	}

	buflen = strlen(argv[2]) + 1 + sizeof(uint16_t)
	         + key_size * sizeof(uint8_t);
	buf = malloc(buflen);
	strcpy(buf, argv[2]);
	p = buf + (strlen(buf) + 1);

	*(uint16_t *)p = key_size;
	p += sizeof(uint16_t);

	memcpy(p, key, key_size * sizeof(uint8_t));

	free(key);

	ret = add_key("dm-crypt", argv[1], buf, buflen, KEY_SPEC_USER_KEYRING);

	free(buf);

	if (ret < 0) {
		perror("add_key");
		return 1;
	}

	printf("new key id: %ld\n", ret);

	return 0;
}