Add autodetection code for active dm device.

src/Makemodule.am

@@ -9,6 +9,7 @@ cryptsetup_SOURCES =		\
 	src/utils_tools.c	\
 	src/utils_password.c	\
 	src/utils_luks2.c	\
+	src/utils_blockdev.c	\
 	src/cryptsetup.c	\
 	src/cryptsetup.h
 

src/cryptsetup.h

@@ -114,6 +114,9 @@ int tools_write_json_file(struct crypt_device *cd, const char *file, const char
 int tools_detect_signatures(const char *device, int ignore_luks, size_t *count);
 int tools_wipe_all_signatures(const char *path);
 
+int tools_lookup_crypt_device(struct crypt_device *cd, const char *type,
+		const char *data_device_path, char *name, size_t name_length);
+
 /* Log */
 #define log_dbg(x...) clogger(NULL, CRYPT_LOG_DEBUG, __FILE__, __LINE__, x)
 #define log_std(x...) clogger(NULL, CRYPT_LOG_NORMAL, __FILE__, __LINE__, x)

src/utils_blockdev.c

@@ -0,0 +1,189 @@
+/*
+ * Linux block devices helpers
+ *
+ * Copyright (C) 2018-2019 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2018-2019 Ondrej Kozina
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "cryptsetup.h"
+#include <dirent.h>
+#ifdef HAVE_SYS_SYSMACROS_H
+# include <sys/sysmacros.h>     /* for major, minor */
+#endif
+#include <uuid/uuid.h>
+
+#define DM_UUID_LEN		129
+#define DM_BY_ID_PREFIX		"dm-uuid-"
+#define DM_BY_ID_PREFIX_LEN	8
+#define DM_UUID_PREFIX		"CRYPT-"
+#define DM_UUID_PREFIX_LEN	6
+#define UUID_LEN 37 /* 36 + \0, libuuid ... */
+
+static int dm_prepare_uuid(const char *type, const char *uuid, char *buf, size_t buflen)
+{
+	char *ptr, uuid2[UUID_LEN] = {0};
+	uuid_t uu;
+	unsigned i = 0;
+
+	/* Remove '-' chars */
+	if (uuid) {
+		if (uuid_parse(uuid, uu) < 0) {
+			log_dbg("Requested UUID %s has invalid format.", uuid);
+			return 0;
+		}
+
+		for (ptr = uuid2, i = 0; i < UUID_LEN; i++)
+			if (uuid[i] != '-') {
+				*ptr = uuid[i];
+				ptr++;
+			}
+	}
+
+	snprintf(buf, buflen, DM_UUID_PREFIX "%s%s%s%s",
+		type ?: "", type ? "-" : "",
+		uuid2[0] ? uuid2 : "", uuid2[0] ? "-" : "");
+
+	return 1;
+}
+
+/* return number of holders in general, if matched dm_uuid prefix it's returned via dm_name */
+/* negative value is error */
+static int lookup_holder_dm_name(const char *dm_uuid, size_t max_len, dev_t devno, char *dm_name, size_t dm_name_length)
+{
+	struct dirent *entry;
+	char dm_subpath[PATH_MAX], data_dev_dir[PATH_MAX], uuid[max_len];
+	ssize_t s;
+	struct stat st;
+	int dmfd, fd, len, r = 0; /* not found */
+	DIR *dir;
+
+	if (!dm_name || !dm_name_length)
+		return -EINVAL;
+
+	*dm_name = '\0';
+
+	len = snprintf(data_dev_dir, PATH_MAX, "/sys/dev/block/%u:%u/holders", major(devno), minor(devno));
+	if (len < 0 || len >= PATH_MAX)
+		return -EINVAL;
+
+	if (!(dir = opendir(data_dev_dir)))
+		/* map ENOTDIR to ENOENT we'll handle both errors same */
+		return errno == ENOTDIR ? -ENOENT : -errno;
+
+	while (r != 1 && (entry = readdir(dir))) {
+		if (entry->d_name[0] == '.' ||
+		    !strncmp(entry->d_name, "..", 2))
+			continue;
+
+		/* there's a holder */
+		r++;
+
+		/* we already have a dm_name, just count remaining holders */
+		if (*dm_name != '\0')
+			continue;
+
+		len = snprintf(dm_subpath, PATH_MAX, "%s/%s", entry->d_name, "dm");
+		if (len < 0 || len >= PATH_MAX) {
+			r = -EINVAL;
+			break;
+		}
+
+		/* looking for dm-X/dm directory, symlinks are fine */
+		dmfd = openat(dirfd(dir), dm_subpath, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+		if (dmfd < 0)
+			continue;
+
+		fd = openat(dmfd, "uuid", O_RDONLY | O_CLOEXEC);
+		if (fd < 0) {
+			close(dmfd);
+			continue;
+		}
+
+		if (fstat(fd, &st) || !S_ISREG(st.st_mode)) {
+			close(fd);
+			close(dmfd);
+			continue;
+		}
+
+		/* reads binary data */
+		s = read_buffer(fd, uuid, max_len - 1);
+		close(fd);
+		uuid[s > 0 ? s : 0] = '\0';
+		if (!strncmp(uuid, dm_uuid, strlen(dm_uuid)))
+			log_dbg("Found candidate device %s", entry->d_name);
+		else {
+			close(dmfd);
+			continue;
+		}
+
+		fd = openat(dmfd, "name", O_RDONLY | O_CLOEXEC);
+		if (fd < 0) {
+			close(dmfd);
+			continue;
+		}
+
+		if (fstat(fd, &st) || !S_ISREG(st.st_mode)) {
+			close(fd);
+			close(dmfd);
+			continue;
+		}
+
+		/* reads binary data */
+		s = read_buffer(fd, dm_name, dm_name_length - 1);
+		close(fd);
+		close(dmfd);
+		if (s > 1) {
+			dm_name[s-1] = '\0';
+			log_dbg("Found dm device %s", dm_name);
+		}
+	}
+
+	closedir(dir);
+
+	return r;
+}
+
+int tools_lookup_crypt_device(struct crypt_device *cd, const char *type,
+		const char *data_device_path, char *name, size_t name_length)
+{
+	int r;
+	char *c;
+	struct stat st;
+	char dev_uuid[DM_UUID_LEN + DM_BY_ID_PREFIX_LEN] = DM_BY_ID_PREFIX;
+
+	if (!dm_prepare_uuid(type, crypt_get_uuid(cd), dev_uuid + DM_BY_ID_PREFIX_LEN, DM_UUID_LEN))
+		return -EINVAL;
+
+	c = strrchr(dev_uuid, '-');
+	if (!c)
+		return -EINVAL;
+
+	/* cut of dm name */
+	*c = '\0';
+
+	log_dbg("Looking for any dm device with prefix: %s", dev_uuid);
+
+	if (stat(data_device_path, &st) < 0)
+		return -ENODEV;
+
+	if (!S_ISBLK(st.st_mode))
+		return -ENOTBLK;
+
+	r = lookup_holder_dm_name(dev_uuid + DM_BY_ID_PREFIX_LEN, DM_UUID_LEN,
+			st.st_rdev, name, name_length);
+	return r;
+}