losetup.c

/* Originally from Ted's losetup.c */

#define LOOPMAJOR	7

/*
 * losetup.c - setup and control loop devices
 */

/* We want __u64 to be unsigned long long */
#define __SANE_USERSPACE_TYPES__

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/sysmacros.h>
#include <stdarg.h>
#include <linux/loop.h>

extern int verbose;
extern char *progname;
extern char *xstrdup (const char *s);	/* not: #include "sundries.h" */
extern void error (const char *fmt, ...);	/* idem */

/* caller guarantees n > 0 */
void xstrncpy(char *dest, const char *src, size_t n)
{
	strncpy(dest, src, n-1);
	dest[n-1] = 0;
}


static int show_loop(char *device)
{
	struct loop_info64 loopinfo64;
	int fd, errsv;

	if ((fd = open(device, O_RDONLY)) < 0) {
		int errsv = errno;
		fprintf(stderr, "loop: can't open device %s: %s\n",
			device, strerror (errsv));
		return 2;
	}

	if (ioctl(fd, LOOP_GET_STATUS64, &loopinfo64) == 0) {

		loopinfo64.lo_file_name[LO_NAME_SIZE-2] = '*';
		loopinfo64.lo_file_name[LO_NAME_SIZE-1] = 0;
		loopinfo64.lo_crypt_name[LO_NAME_SIZE-1] = 0;

		printf("%s: [%04llx]:%llu (%s)",
		       device, loopinfo64.lo_device, loopinfo64.lo_inode,
		       loopinfo64.lo_file_name);

		if (loopinfo64.lo_offset)
			printf(", offset %lld", loopinfo64.lo_offset);

		if (loopinfo64.lo_sizelimit)
			printf(", sizelimit %lld", loopinfo64.lo_sizelimit);

		if (loopinfo64.lo_encrypt_type ||
		    loopinfo64.lo_crypt_name[0]) {
			const char *e = (const char *)loopinfo64.lo_crypt_name;

			if (*e == 0 && loopinfo64.lo_encrypt_type == 1)
				e = "XOR";
			printf(", encryption %s (type %d)",
			       e, loopinfo64.lo_encrypt_type);
		}
		printf("\n");
		close (fd);
		return 0;
	}

	errsv = errno;
	fprintf(stderr, "loop: can't get info on device %s: %s\n",
		device, strerror (errsv));
	close (fd);
	return 1;
}

int
is_loop_device (const char *device) {
	struct stat statbuf;

	return (stat(device, &statbuf) == 0 &&
		S_ISBLK(statbuf.st_mode) &&
		major(statbuf.st_rdev) == LOOPMAJOR);
}

#define SIZE(a) (sizeof(a)/sizeof(a[0]))

char * find_unused_loop_device (void)
{
	char dev[20];
	int fd, rc;

	fd = open("/dev/loop-control", O_RDWR);
	if (fd < 0) {
		error("%s: could not open /dev/loop-control. Maybe this kernel "
		      "does not know\n"
		      "       about the loop device? (If so, recompile or "
		      "`modprobe loop'.)", progname);
		return NULL;
	}
	rc = ioctl(fd, LOOP_CTL_GET_FREE, 0);
	close(fd);
	if (rc < 0) {
		error("%s: could not find any free loop device", progname);
		return NULL;
	}

	sprintf(dev, "/dev/loop%d", rc);
	return xstrdup(dev);
}

/*
 * A function to read the passphrase either from the terminal or from
 * an open file descriptor.
 */
static char * xgetpass(int pfd, const char *prompt)
{
	char *pass;
	int buflen, i;
	/* klibc-tools-standalone */
	(void)prompt;

	pass = NULL;
	buflen = 0;
	for (i=0; ; i++) {
		if (i >= buflen-1) {
				/* we're running out of space in the buffer.
				 * Make it bigger: */
			char *tmppass = pass;
			buflen += 128;
			pass = realloc(tmppass, buflen);
			if (pass == NULL) {
				/* realloc failed. Stop reading. */
				error("Out of memory while reading passphrase");
				pass = tmppass; /* the old buffer hasn't changed */
				break;
			}
		}
		if (read(pfd, pass+i, 1) != 1 ||
		    pass[i] == '\n' || pass[i] == 0)
			break;
	}

	if (pass == NULL)
		return "";

	pass[i] = 0;
	return pass;
}

static int digits_only(const char *s)
{
	while (*s)
		if (!isdigit(*s++))
			return 0;
	return 1;
}

int set_loop(const char *device, const char *file, unsigned long long offset,
	 const char *encryption, int pfd, int *loopro) {
	struct loop_info64 loopinfo64;
	int fd, ffd, mode, i;
	char *pass;

	mode = (*loopro ? O_RDONLY : O_RDWR);
	if ((ffd = open(file, mode)) < 0) {
		if (!*loopro && errno == EROFS)
			ffd = open(file, mode = O_RDONLY);
		if (ffd < 0) {
			perror(file);
			return 1;
		}
	}
	if ((fd = open(device, mode)) < 0) {
		perror (device);
		return 1;
	}
	*loopro = (mode == O_RDONLY);

	memset(&loopinfo64, 0, sizeof(loopinfo64));

	xstrncpy((char *)loopinfo64.lo_file_name, file, LO_NAME_SIZE);

	if (encryption && *encryption) {
		if (digits_only(encryption)) {
			loopinfo64.lo_encrypt_type = atoi(encryption);
		} else {
			loopinfo64.lo_encrypt_type = LO_CRYPT_CRYPTOAPI;
			snprintf((char *)loopinfo64.lo_crypt_name, LO_NAME_SIZE,
				 "%s", encryption);
		}
	}

	loopinfo64.lo_offset = offset;


	switch (loopinfo64.lo_encrypt_type) {
	case LO_CRYPT_NONE:
		loopinfo64.lo_encrypt_key_size = 0;
		break;
	case LO_CRYPT_XOR:
		pass = xgetpass(pfd, "Password: ");
		goto gotpass;
	default:
		pass = xgetpass(pfd, "Password: ");
	gotpass:
		memset(loopinfo64.lo_encrypt_key, 0, LO_KEY_SIZE);
		xstrncpy((char *)loopinfo64.lo_encrypt_key, pass, LO_KEY_SIZE);
		memset(pass, 0, strlen(pass));
		loopinfo64.lo_encrypt_key_size = LO_KEY_SIZE;
	}

	if (ioctl(fd, LOOP_SET_FD, (void *)(size_t)ffd) < 0) {
		perror("ioctl: LOOP_SET_FD");
		return 1;
	}
	close (ffd);

	i = ioctl(fd, LOOP_SET_STATUS64, &loopinfo64);
	if (i)
		perror("ioctl: LOOP_SET_STATUS64");
	memset(&loopinfo64, 0, sizeof(loopinfo64));

	if (i) {
		ioctl (fd, LOOP_CLR_FD, 0);
		close (fd);
		return 1;
	}
	close (fd);

	if (verbose > 1)
		printf("set_loop(%s,%s,%llu): success\n",
		       device, file, offset);
	return 0;
}

int del_loop (const char *device)
{
	int fd;

	if ((fd = open (device, O_RDONLY)) < 0) {
		int errsv = errno;
		fprintf(stderr, "loop: can't delete device %s: %s\n",
			device, strerror (errsv));
		return 1;
	}
	if (ioctl (fd, LOOP_CLR_FD, 0) < 0) {
		perror ("ioctl: LOOP_CLR_FD");
		close (fd);
		return 1;
	}
	close (fd);
	if (verbose > 1)
		printf("del_loop(%s): success\n", device);
	return 0;
}


int verbose = 0;
char *progname;

static void usage(FILE *f)
{
	fprintf(f, "usage:\n\
  %s loop_device                                       # give info\n\
  %s -d loop_device                                    # delete\n\
  %s -f                                                # find unused\n\
  %s -h                                                # this help\n\
  %s [-e encryption] [-o offset] {-f|loop_device} file # setup\n",
		progname, progname, progname, progname, progname);
	exit(f == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}

char * xstrdup (const char *s) {
	char *t;

	if (s == NULL)
		return NULL;

	t = strdup (s);

	if (t == NULL) {
		fprintf(stderr, "not enough memory");
		exit(1);
	}

	return t;
}

void error (const char *fmt, ...)
{
	va_list args;

	va_start (args, fmt);
	vfprintf (stderr, fmt, args);
	va_end (args);
	fprintf (stderr, "\n");
}

int main(int argc, char **argv)
{
	char *p, *offset, *encryption, *passfd, *device, *file;
	int delete, find, c;
	int res = 0;
	int ro = 0;
	int pfd = -1;
	unsigned long long off;


	delete = find = 0;
	off = 0;
	offset = encryption = passfd = NULL;

	progname = argv[0];
	if ((p = strrchr(progname, '/')) != NULL)
		progname = p+1;

	while ((c = getopt(argc, argv, "de:E:fho:p:v")) != -1) {
		switch (c) {
		case 'd':
			delete = 1;
			break;
		case 'E':
		case 'e':
			encryption = optarg;
			break;
		case 'f':
			find = 1;
			break;
		case 'h':
			usage(stdout);
			break;
		case 'o':
			offset = optarg;
			break;
		case 'p':
			passfd = optarg;
			break;
		case 'v':
			verbose = 1;
			break;
		default:
			usage(stderr);
		}
	}

	if (argc == 1) {
		usage(stderr);
	} else if (delete) {
		if (argc != optind+1 || encryption || offset || find)
			usage(stderr);
	} else if (find) {
		if (argc < optind || argc > optind+1)
			usage(stderr);
	} else {
		if (argc < optind+1 || argc > optind+2)
			usage(stderr);
	}

	if (find) {
		device = find_unused_loop_device();
		if (device == NULL)
			return -1;
		if (verbose)
			printf("Loop device is %s\n", device);
		if (argc == optind) {
			printf("%s\n", device);
			return 0;
		}
		file = argv[optind];
	} else {
		device = argv[optind];
		if (argc == optind+1)
			file = NULL;
		else
			file = argv[optind+1];
	}

	if (delete)
		res = del_loop(device);
	else if (file == NULL)
		res = show_loop(device);
	else {
		if (offset && sscanf(offset, "%llu", &off) != 1)
			usage(stderr);
		if (passfd && sscanf(passfd, "%d", &pfd) != 1)
			usage(stderr);
		res = set_loop(device, file, off, encryption, pfd, &ro);
	}
	return res;
}