Map TCRYPT system encryption through partition.

Kernel doesn't allow mapping through whle device if some
other partition an the device is used.

So first try to find partition device which match
system encryption (== TCRYPT partition system encryption)
and use that.

lib/internal.h

@@ -94,6 +94,7 @@ int crypt_confirm(struct crypt_device *cd, const char *msg);
 char *crypt_lookup_dev(const char *dev_id);
 int crypt_dev_is_rotational(int major, int minor);
 int crypt_dev_is_partition(const char *dev_path);
+char *crypt_get_partition_device(const char *dev_path, uint64_t offset, uint64_t size);
 
 ssize_t write_blockwise(int fd, int bsize, void *buf, size_t count);
 ssize_t read_blockwise(int fd, int bsize, void *_buf, size_t count);

lib/tcrypt/tcrypt.c

@@ -641,7 +641,8 @@ int TCRYPT_activate(struct crypt_device *cd,
 		     uint32_t flags)
 {
 	char cipher[MAX_CIPHER_LEN], dm_name[PATH_MAX], dm_dev_name[PATH_MAX];
-	struct device *device = NULL;
+	char *part_path;
+	struct device *device = NULL, *part_device = NULL;
 	unsigned int i;
 	int r;
 	struct tcrypt_algs *algs;
@@ -693,6 +694,18 @@ int TCRYPT_activate(struct crypt_device *cd,
 	else
 		device_check = DEV_EXCL;
 
+	if ((params->flags & CRYPT_TCRYPT_SYSTEM_HEADER) &&
+		(part_path = crypt_get_partition_device(device_path(dmd.data_device),
+				 dmd.u.crypt.offset, dmd.size))) {
+		if (!device_alloc(&part_device, part_path)) {
+			log_verbose(cd, _("Activating TCRYPT system encryption for partition %s.\n"),
+				    part_path);
+			dmd.data_device = part_device;
+			dmd.u.crypt.offset = 0;
+		}
+		free(part_path);
+	}
+
 	r = device_block_adjust(cd, dmd.data_device, device_check,
 				dmd.u.crypt.offset, &dmd.size, &dmd.flags);
 	if (r)
@@ -744,6 +757,7 @@ int TCRYPT_activate(struct crypt_device *cd,
 		r = -ENOTSUP;
 	}
 
+	device_free(part_device);
 	crypt_free_volume_key(dmd.u.crypt.vk);
 	return r;
 }

lib/utils_devpath.c

@@ -170,16 +170,12 @@ char *crypt_lookup_dev(const char *dev_id)
 	return devpath;
 }
 
-static int _sysfs_get_uint64(int major, int minor, uint64_t *value, const char *attr)
+static int _read_uint64(const char *sysfs_path, uint64_t *value)
 {
-	char path[PATH_MAX], tmp[64] = {0};
+	char tmp[64] = {0};
 	int fd, r;
 
-	if (snprintf(path, sizeof(path), "/sys/dev/block/%d:%d/%s",
-		     major, minor, attr) < 0)
-		return 0;
-
-	if ((fd = open(path, O_RDONLY)) < 0)
+	if ((fd = open(sysfs_path, O_RDONLY)) < 0)
 		return 0;
 	r = read(fd, tmp, sizeof(tmp));
 	close(fd);
@@ -193,6 +189,28 @@ static int _sysfs_get_uint64(int major, int minor, uint64_t *value, const char *
 	return 1;
 }
 
+static int _sysfs_get_uint64(int major, int minor, uint64_t *value, const char *attr)
+{
+	char path[PATH_MAX];
+
+	if (snprintf(path, sizeof(path), "/sys/dev/block/%d:%d/%s",
+		     major, minor, attr) < 0)
+		return 0;
+
+	return _read_uint64(path, value);
+}
+
+static int _path_get_uint64(const char *sysfs_path, uint64_t *value, const char *attr)
+{
+	char path[PATH_MAX];
+
+	if (snprintf(path, sizeof(path), "%s/%s",
+		     sysfs_path, attr) < 0)
+		return 0;
+
+	return _read_uint64(path, value);
+}
+
 int crypt_dev_is_rotational(int major, int minor)
 {
 	uint64_t val;
@@ -220,3 +238,73 @@ int crypt_dev_is_partition(const char *dev_path)
 
 	return val ? 1 : 0;
 }
+
+/* Try to find partition which match offset and size on top level device */
+char *crypt_get_partition_device(const char *dev_path, uint64_t offset, uint64_t size)
+{
+	char link[PATH_MAX], path[PATH_MAX], part_path[PATH_MAX], *devname;
+	char *result = NULL;
+	struct stat st;
+	size_t devname_len;
+	ssize_t len;
+	struct dirent *entry;
+	DIR *dir;
+	uint64_t part_offset, part_size;
+
+	if (stat(dev_path, &st) < 0)
+		return NULL;
+
+	if (!S_ISBLK(st.st_mode))
+		return NULL;
+
+	if (snprintf(path, sizeof(path), "/sys/dev/block/%d:%d",
+		major(st.st_rdev), minor(st.st_rdev)) < 0)
+		return NULL;
+
+	len = readlink(path, link, sizeof(link) - 1);
+	if (len < 0)
+		return NULL;
+
+	/* Get top level disk name for sysfs search */
+	link[len] = '\0';
+	devname = strrchr(link, '/');
+	if (!devname)
+		return NULL;
+	devname++;
+
+	/* DM devices do not use kernel partitions. */
+	if (dm_is_dm_kernel_name(devname))
+		return NULL;
+
+	dir = opendir(path);
+	if (!dir)
+		return NULL;
+
+	devname_len = strlen(devname);
+	while((entry = readdir(dir))) {
+		if (strncmp(entry->d_name, devname, devname_len))
+			continue;
+
+		if (snprintf(part_path, sizeof(part_path), "%s/%s",
+		    path, entry->d_name) < 0)
+			continue;
+
+		if (stat(part_path, &st) < 0)
+			continue;
+
+		if (S_ISDIR(st.st_mode)) {
+			if (!_path_get_uint64(part_path, &part_offset, "start") ||
+			    !_path_get_uint64(part_path, &part_size, "size"))
+				continue;
+			if (part_offset == offset && part_size == size &&
+			    snprintf(part_path, sizeof(part_path), "/dev/%s",
+				     entry->d_name) > 0) {
+				result = strdup(part_path);
+				break;
+			}
+		}
+	}
+	closedir(dir);
+
+	return result;
+}