[thirdparty/util-linux.git] / libblkid / src / evaluate.c

/*
 * evaluate.c - very high-level API to evaluate LABELs or UUIDs
 *
 * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
 *
 * This file may be redistributed under the terms of the
 * GNU Lesser General Public License.
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/types.h>
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include <stdint.h>
#include <stdarg.h>

#include "pathnames.h"
#include "canonicalize.h"

#include "blkidP.h"

/**
 * SECTION:evaluate
 * @title: Tags and Spec evaluation
 * @short_description: top-level API for LABEL and UUID evaluation.
 *
 * This API provides very simple and portable way how evaluate LABEL and UUID
 * tags.  The blkid_evaluate_tag() and blkid_evaluate_spec() work on 2.4 and
 * 2.6 systems and on systems with or without udev. Currently, the libblkid
 * library supports "udev" and "scan" methods. The "udev" method uses udev
 * /dev/disk/by-* symlinks and the "scan" method scans all block devices from
 * the /proc/partitions file. The evaluation could be controlled by the
 * /etc/blkid.conf config file. The default is to try "udev" and then "scan"
 * method.
 *
 * The blkid_evaluate_tag() also automatically informs udevd when an obsolete
 * /dev/disk/by-* symlink is detected.
 *
 * If you are not sure how translate LABEL or UUID to the device name use this
 * API.
 */

/* returns zero when the device has NAME=value (LABEL/UUID) */
static int verify_tag(const char *devname, const char *name, const char *value)
{
	blkid_probe pr;
	int fd = -1, rc = -1;
	size_t len;
	const char *data;
	int errsv = 0;

	pr = blkid_new_probe();
	if (!pr)
		return -1;

	blkid_probe_enable_superblocks(pr, TRUE);
	blkid_probe_set_superblocks_flags(pr,
			BLKID_SUBLKS_LABEL | BLKID_SUBLKS_UUID);

	fd = open(devname, O_RDONLY);
	if (fd < 0) {
		errsv = errno;
		goto done;
	}
	if (blkid_probe_set_device(pr, fd, 0, 0))
		goto done;
	rc = blkid_do_safeprobe(pr);
	if (rc)
		goto done;
	rc = blkid_probe_lookup_value(pr, name, &data, &len);
	if (!rc)
		rc = memcmp(value, data, len);
done:
	DBG(DEBUG_EVALUATE, printf("%s: %s verification %s\n",
			devname, name, rc == 0 ? "PASS" : "FAILED"));
	if (fd >= 0)
		close(fd);
	blkid_free_probe(pr);

	/* for non-root users we use unverified udev links */
	return errsv == EACCES ? 0 : rc;
}

/**
 * blkid_send_uevent:
 * @devname: absolute path to the device
 * @action: event string
 *
 * Returns: -1 in case of failure, or 0 on success.
 */
int blkid_send_uevent(const char *devname, const char *action)
{
	char uevent[PATH_MAX];
	struct stat st;
	FILE *f;
	int rc = -1;

	DBG(DEBUG_EVALUATE, printf("%s: uevent '%s' requested\n", devname, action));

	if (!devname || !action)
		return -1;
	if (stat(devname, &st) || !S_ISBLK(st.st_mode))
		return -1;

	snprintf(uevent, sizeof(uevent), "/sys/dev/block/%d:%d/uevent",
			major(st.st_rdev), minor(st.st_rdev));

	f = fopen(uevent, "w");
	if (f) {
		rc = 0;
		if (fputs(action, f) >= 0)
			rc = 0;
		fclose(f);
	}
	DBG(DEBUG_EVALUATE, printf("%s: send uevent %s\n",
			uevent, rc == 0 ? "SUCCES" : "FAILED"));
	return rc;
}

static char *evaluate_by_udev(const char *token, const char *value, int uevent)
{
	char dev[PATH_MAX];
	char *path = NULL;
	size_t len;
	struct stat st;

	DBG(DEBUG_EVALUATE,
	    printf("evaluating by udev %s=%s\n", token, value));

	if (!strcmp(token, "UUID"))
		strcpy(dev, _PATH_DEV_BYUUID "/");
	else if (!strcmp(token, "LABEL"))
		strcpy(dev, _PATH_DEV_BYLABEL "/");
	else {
		DBG(DEBUG_EVALUATE,
		    printf("unsupported token %s\n", token));
		return NULL;	/* unsupported tag */
	}

	len = strlen(dev);
	if (blkid_encode_string(value, &dev[len], sizeof(dev) - len) != 0)
		return NULL;

	DBG(DEBUG_EVALUATE,
	    printf("expected udev link: %s\n", dev));

	if (stat(dev, &st))
		goto failed;	/* link or device does not exist */

	if (!S_ISBLK(st.st_mode))
		return NULL;

	path = canonicalize_path(dev);
	if (!path)
		return NULL;

	if (verify_tag(path, token, value))
		goto failed;
	return path;

failed:
	DBG(DEBUG_EVALUATE, printf("failed to evaluate by udev\n"));

	if (uevent && path)
		blkid_send_uevent(path, "change");
	free(path);
	return NULL;
}

static char *evaluate_by_scan(const char *token, const char *value,
		blkid_cache *cache, struct blkid_config *conf)
{
	blkid_cache c = cache ? *cache : NULL;
	char *res;

	DBG(DEBUG_EVALUATE,
	    printf("evaluating by blkid scan %s=%s\n", token, value));

	if (!c) {
		char *cachefile = blkid_get_cache_filename(conf);
		blkid_get_cache(&c, cachefile);
		free(cachefile);
	}
	if (!c)
		return NULL;

	res = blkid_get_devname(c, token, value);

	if (cache)
		*cache = c;
	else
		blkid_put_cache(c);

	return res;
}

/**
 * blkid_evaluate_tag:
 * @token: token name (e.g "LABEL" or "UUID") or unparsed tag (e.g. "LABEL=foo")
 * @value: token data (e.g. "foo")
 * @cache: pointer to cache (or NULL when you don't want to re-use the cache)
 *
 * Returns: allocated string with a device name.
 */
char *blkid_evaluate_tag(const char *token, const char *value, blkid_cache *cache)
{
	struct blkid_config *conf = NULL;
	char *t = NULL, *v = NULL;
	char *ret = NULL;
	int i;

	if (!token)
		return NULL;

	if (!cache || !*cache)
		blkid_init_debug(0);

	DBG(DEBUG_EVALUATE,
	    printf("evaluating  %s%s%s\n", token, value ? "=" : "",
		   value ? value : ""));

	if (!value) {
		if (!strchr(token, '=')) {
			ret = blkid_strdup(token);
			goto out;
		}
		blkid_parse_tag_string(token, &t, &v);
		if (!t || !v)
			goto out;
		token = t;
		value = v;
	}

	conf = blkid_read_config(NULL);
	if (!conf)
		goto out;

	for (i = 0; i < conf->nevals; i++) {
		if (conf->eval[i] == BLKID_EVAL_UDEV)
			ret = evaluate_by_udev(token, value, conf->uevent);
		else if (conf->eval[i] == BLKID_EVAL_SCAN)
			ret = evaluate_by_scan(token, value, cache, conf);
		if (ret)
			break;
	}

	DBG(DEBUG_EVALUATE,
	    printf("%s=%s evaluated as %s\n", token, value, ret));
out:
	blkid_free_config(conf);
	free(t);
	free(v);
	return ret;
}

/**
 * blkid_evaluate_spec:
 * @spec: unparsed tag (e.g. "LABEL=foo") or path (e.g. /dev/dm-0)
 * @cache: pointer to cache (or NULL when you don't want to re-use the cache)
 *
 * All returned paths are canonicalized, device-mapper paths are converted
 * to the /dev/mapper/name format.
 *
 * Returns: allocated string with a device name.
 */
char *blkid_evaluate_spec(const char *spec, blkid_cache *cache)
{
	char *t = NULL, *v = NULL, *res;

	if (!spec)
		return NULL;

	if (strchr(spec, '=') &&
	    blkid_parse_tag_string(spec, &t, &v) != 0)	/* parse error */
		return NULL;

	if (v)
		res = blkid_evaluate_tag(t, v, cache);
	else
		res = canonicalize_path(spec);

	free(t);
	free(v);
	return res;
}


#ifdef TEST_PROGRAM
int main(int argc, char *argv[])
{
	blkid_cache cache = NULL;
	char *res;

	if (argc < 2) {
		fprintf(stderr, "usage: %s <tag> | <spec>\n", argv[0]);
		return EXIT_FAILURE;
	}

	blkid_init_debug(0);

	res = blkid_evaluate_spec(argv[1], &cache);
	if (res)
		printf("%s\n", res);
	if (cache)
		blkid_put_cache(cache);

	return res ? EXIT_SUCCESS : EXIT_FAILURE;
}
#endif
Commit	Line	Data
892a404c KZ	1	/*
	2	* evaluate.c - very high-level API to evaluate LABELs or UUIDs
	3	*
892a404c KZ	4	* Copyright (C) 2009 Karel Zak <kzak@redhat.com>
	5	*
	6	* This file may be redistributed under the terms of the
	7	* GNU Lesser General Public License.
	8	*/
892a404c KZ	9	#include <stdio.h>
	10	#include <string.h>
	11	#include <stdlib.h>
	12	#include <unistd.h>
	13	#include <fcntl.h>
	14	#include <ctype.h>
	15	#include <sys/types.h>
	16	#ifdef HAVE_SYS_STAT_H
	17	#include <sys/stat.h>
	18	#endif
892a404c KZ	19	#ifdef HAVE_ERRNO_H
	20	#include <errno.h>
	21	#endif
	22	#include <stdint.h>
892a404c KZ	23	#include <stdarg.h>
	24
	25	#include "pathnames.h"
	26	#include "canonicalize.h"
	27
892a404c KZ	28	#include "blkidP.h"
892a404c KZ	29
488e52be KZ	30	/**
488e52be KZ	31	* SECTION:evaluate
fd7c9e35	32	* @title: Tags and Spec evaluation
488e52be KZ	33	* @short_description: top-level API for LABEL and UUID evaluation.
	34	*
	35	* This API provides very simple and portable way how evaluate LABEL and UUID
fd7c9e35 KZ	36	* tags. The blkid_evaluate_tag() and blkid_evaluate_spec() work on 2.4 and
	37	* 2.6 systems and on systems with or without udev. Currently, the libblkid
	38	* library supports "udev" and "scan" methods. The "udev" method uses udev
	39	* /dev/disk/by-* symlinks and the "scan" method scans all block devices from
	40	* the /proc/partitions file. The evaluation could be controlled by the
	41	* /etc/blkid.conf config file. The default is to try "udev" and then "scan"
	42	* method.
488e52be KZ	43	*
	44	* The blkid_evaluate_tag() also automatically informs udevd when an obsolete
	45	* /dev/disk/by-* symlink is detected.
	46	*
	47	* If you are not sure how translate LABEL or UUID to the device name use this
	48	* API.
	49	*/
	50
892a404c KZ	51	/* returns zero when the device has NAME=value (LABEL/UUID) */
	52	static int verify_tag(const char devname, const char name, const char *value)
	53	{
	54	blkid_probe pr;
	55	int fd = -1, rc = -1;
	56	size_t len;
6d042d0d	57	const char *data;
e9799b6d	58	int errsv = 0;
892a404c KZ	59
	60	pr = blkid_new_probe();
	61	if (!pr)
	62	return -1;
	63
1b780848 KZ	64	blkid_probe_enable_superblocks(pr, TRUE);
	65	blkid_probe_set_superblocks_flags(pr,
	66	BLKID_SUBLKS_LABEL \| BLKID_SUBLKS_UUID);
892a404c KZ	67
892a404c KZ	68	fd = open(devname, O_RDONLY);
e9799b6d KZ	69	if (fd < 0) {
e9799b6d KZ	70	errsv = errno;
892a404c	71	goto done;
e9799b6d	72	}
892a404c KZ	73	if (blkid_probe_set_device(pr, fd, 0, 0))
	74	goto done;
	75	rc = blkid_do_safeprobe(pr);
	76	if (rc)
	77	goto done;
	78	rc = blkid_probe_lookup_value(pr, name, &data, &len);
	79	if (!rc)
	80	rc = memcmp(value, data, len);
	81	done:
	82	DBG(DEBUG_EVALUATE, printf("%s: %s verification %s\n",
	83	devname, name, rc == 0 ? "PASS" : "FAILED"));
	84	if (fd >= 0)
	85	close(fd);
	86	blkid_free_probe(pr);
e9799b6d KZ	87
	88	/* for non-root users we use unverified udev links */
	89	return errsv == EACCES ? 0 : rc;
892a404c KZ	90	}
	91
	92	/**
	93	* blkid_send_uevent:
	94	* @devname: absolute path to the device
fd7c9e35	95	* @action: event string
892a404c	96	*
488e52be	97	* Returns: -1 in case of failure, or 0 on success.
892a404c KZ	98	*/
	99	int blkid_send_uevent(const char devname, const char action)
	100	{
	101	char uevent[PATH_MAX];
	102	struct stat st;
	103	FILE *f;
	104	int rc = -1;
	105
	106	DBG(DEBUG_EVALUATE, printf("%s: uevent '%s' requested\n", devname, action));
	107
	108	if (!devname \|\| !action)
	109	return -1;
	110	if (stat(devname, &st) \|\| !S_ISBLK(st.st_mode))
	111	return -1;
	112
	113	snprintf(uevent, sizeof(uevent), "/sys/dev/block/%d:%d/uevent",
	114	major(st.st_rdev), minor(st.st_rdev));
	115
	116	f = fopen(uevent, "w");
	117	if (f) {
	118	rc = 0;
	119	if (fputs(action, f) >= 0)
	120	rc = 0;
	121	fclose(f);
	122	}
	123	DBG(DEBUG_EVALUATE, printf("%s: send uevent %s\n",
	124	uevent, rc == 0 ? "SUCCES" : "FAILED"));
	125	return rc;
	126	}
	127
	128	static char evaluate_by_udev(const char token, const char *value, int uevent)
	129	{
	130	char dev[PATH_MAX];
	131	char *path = NULL;
	132	size_t len;
	133	struct stat st;
	134
	135	DBG(DEBUG_EVALUATE,
	136	printf("evaluating by udev %s=%s\n", token, value));
	137
	138	if (!strcmp(token, "UUID"))
	139	strcpy(dev, _PATH_DEV_BYUUID "/");
	140	else if (!strcmp(token, "LABEL"))
	141	strcpy(dev, _PATH_DEV_BYLABEL "/");
	142	else {
	143	DBG(DEBUG_EVALUATE,
	144	printf("unsupported token %s\n", token));
	145	return NULL; /* unsupported tag */
	146	}
	147
	148	len = strlen(dev);
	149	if (blkid_encode_string(value, &dev[len], sizeof(dev) - len) != 0)
	150	return NULL;
	151
	152	DBG(DEBUG_EVALUATE,
	153	printf("expected udev link: %s\n", dev));
	154
	155	if (stat(dev, &st))
	156	goto failed; /* link or device does not exist */
	157
	158	if (!S_ISBLK(st.st_mode))
	159	return NULL;
	160
	161	path = canonicalize_path(dev);
162	if (!path)
163	return NULL;
164
165	if (verify_tag(path, token, value))
166	goto failed;
167	return path;
168
169	failed:
170	DBG(DEBUG_EVALUATE, printf("failed to evaluate by udev\n"));
171
172	if (uevent && path)
173	blkid_send_uevent(path, "change");
174	free(path);
175	return NULL;
176	}
177
178	static char evaluate_by_scan(const char token, const char *value,
bb5f2876	179	blkid_cache cache, struct blkid_config conf)
892a404c KZ	180	{
	181	blkid_cache c = cache ? *cache : NULL;
	182	char *res;
	183
	184	DBG(DEBUG_EVALUATE,
	185	printf("evaluating by blkid scan %s=%s\n", token, value));
	186
bb5f2876 KZ	187	if (!c) {
bb5f2876 KZ	188	char *cachefile = blkid_get_cache_filename(conf);
892a404c	189	blkid_get_cache(&c, cachefile);
bb5f2876 KZ	190	free(cachefile);
bb5f2876 KZ	191	}
892a404c KZ	192	if (!c)
	193	return NULL;
	194
	195	res = blkid_get_devname(c, token, value);
	196
	197	if (cache)
	198	*cache = c;
	199	else
	200	blkid_put_cache(c);
	201
	202	return res;
	203	}
	204
	205	/**
cee95a95	206	* blkid_evaluate_tag:
5298f728 KZ	207	* @token: token name (e.g "LABEL" or "UUID") or unparsed tag (e.g. "LABEL=foo")
5298f728 KZ	208	* @value: token data (e.g. "foo")
892a404c KZ	209	* @cache: pointer to cache (or NULL when you don't want to re-use the cache)
892a404c KZ	210	*
488e52be	211	* Returns: allocated string with a device name.
892a404c	212	*/
cee95a95	213	char blkid_evaluate_tag(const char token, const char value, blkid_cache cache)
892a404c KZ	214	{
	215	struct blkid_config *conf = NULL;
	216	char t = NULL, v = NULL;
	217	char *ret = NULL;
	218	int i;
	219
	220	if (!token)
	221	return NULL;
	222
	223	if (!cache \|\| !*cache)
7a458332	224	blkid_init_debug(0);
892a404c KZ	225
	226	DBG(DEBUG_EVALUATE,
	227	printf("evaluating %s%s%s\n", token, value ? "=" : "",
	228	value ? value : ""));
	229
	230	if (!value) {
	231	if (!strchr(token, '=')) {
	232	ret = blkid_strdup(token);
	233	goto out;
	234	}
	235	blkid_parse_tag_string(token, &t, &v);
	236	if (!t \|\| !v)
	237	goto out;
	238	token = t;
	239	value = v;
	240	}
	241
	242	conf = blkid_read_config(NULL);
	243	if (!conf)
	244	goto out;
	245
	246	for (i = 0; i < conf->nevals; i++) {
	247	if (conf->eval[i] == BLKID_EVAL_UDEV)
	248	ret = evaluate_by_udev(token, value, conf->uevent);
	249	else if (conf->eval[i] == BLKID_EVAL_SCAN)
bb5f2876	250	ret = evaluate_by_scan(token, value, cache, conf);
892a404c KZ	251	if (ret)
	252	break;
	253	}
	254
	255	DBG(DEBUG_EVALUATE,
	256	printf("%s=%s evaluated as %s\n", token, value, ret));
	257	out:
	258	blkid_free_config(conf);
	259	free(t);
	260	free(v);
	261	return ret;
	262	}
	263
5298f728 KZ	264	/**
	265	* blkid_evaluate_spec:
	266	* @spec: unparsed tag (e.g. "LABEL=foo") or path (e.g. /dev/dm-0)
	267	* @cache: pointer to cache (or NULL when you don't want to re-use the cache)
	268	*
	269	* All returned paths are canonicalized, device-mapper paths are converted
fd7c9e35	270	* to the /dev/mapper/name format.
5298f728 KZ	271	*
	272	* Returns: allocated string with a device name.
	273	*/
	274	char blkid_evaluate_spec(const char spec, blkid_cache *cache)
	275	{
	276	char t = NULL, v = NULL, *res;
	277
	278	if (!spec)
	279	return NULL;
	280
	281	if (strchr(spec, '=') &&
	282	blkid_parse_tag_string(spec, &t, &v) != 0) /* parse error */
	283	return NULL;
	284
	285	if (v)
	286	res = blkid_evaluate_tag(t, v, cache);
	287	else
	288	res = canonicalize_path(spec);
	289
	290	free(t);
	291	free(v);
	292	return res;
	293	}
	294
	295
892a404c KZ	296	#ifdef TEST_PROGRAM
	297	int main(int argc, char *argv[])
	298	{
	299	blkid_cache cache = NULL;
	300	char *res;
	301
5298f728 KZ	302	if (argc < 2) {
5298f728 KZ	303	fprintf(stderr, "usage: %s <tag> \| <spec>\n", argv[0]);
892a404c KZ	304	return EXIT_FAILURE;
	305	}
	306
7a458332	307	blkid_init_debug(0);
892a404c	308
5298f728	309	res = blkid_evaluate_spec(argv[1], &cache);
892a404c KZ	310	if (res)
	311	printf("%s\n", res);
	312	if (cache)
	313	blkid_put_cache(cache);
	314
	315	return res ? EXIT_SUCCESS : EXIT_FAILURE;
	316	}
	317	#endif