Add a --root-becomes option to tar2sqfs and sqfs2tar

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

5 files changed, 194 insertions, 33 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f8a300..d82d8b8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Port to Windows using MinGW cross compilation toolchain.
 - Port to BSD systems.
 - Explicit argument invalid error code in `libsquashfs`.
+- A `--root-becomes` option to `tar2sqfs` and `sqfs2tar`.
 
 ### Changed
 - Return propper error code from `sqfs_get_xattr_prefix_id`.
diff --git a/doc/sqfs2tar.1 b/doc/sqfs2tar.1
index 7d91396..f42b266 100644
--- a/doc/sqfs2tar.1
+++ b/doc/sqfs2tar.1
@@ -11,6 +11,16 @@ archives. The resulting archive is written to stdout.
 .PP
 Possible options:
 .TP
+\fB\-\-root\-becomes\fR, \fB\-r\fR <dir>
+Prefix all paths in the tarball with the given directory name and add an
+entry for this directory that receives all meta data (permissions, ownership,
+extended attributes, et cetera) of the root inode.
+
+The special value \fB.\fR can be used since many tar archivers themselves pack
+the attributes of the root directory that way and naturally support this.
+
+If this option is not used, all meta data from the root inode IS LOST!
+.TP
 \fB\-\-subdir\fR, \fB\-d\fR <dir>
 Unpack the given sub directory instead of the filesystem root. Can be specified
 more than once to select multiple directories. If only one is specified, it
diff --git a/doc/tar2sqfs.1 b/doc/tar2sqfs.1
index c2c7f72..70f2006 100644
--- a/doc/tar2sqfs.1
+++ b/doc/tar2sqfs.1
@@ -14,6 +14,18 @@ SquashFS.
 .PP
 Possible options:
 .TP
+\fB\-\-root\-becomes\fR, \fB\-r\fR <dir>
+If set, only pack entries that are underneath the specified directory and the
+prefix is stripped. The meta data for the directory itself is copied to the
+root inode, i.e. the ownership, permissions, extended attributes (unless
+\f\-\-no\-xattr\R is set), and modification time
+(unless \fB\-\-no\-keep\-time\fR is set).
+
+If this option is not set, tar2sqfs implicitly treats \fB./\fR or absolute
+paths this way, i.e. if the archive contains an entry for \fB./\fR, it becomes
+the root node and the prefix is stripped from all paths (and similar for
+absolute paths and \fB/\fR).
+.TP
 \fB\-\-compressor\fR, \fB\-c\fR <name>
 Select the compressor to use.
 Run \fBtar2sqfs \-\-help\fR to get a list of all available compressors
diff --git a/tar/sqfs2tar.c b/tar/sqfs2tar.c
index 9a12a96..8cfad62 100644
--- a/tar/sqfs2tar.c
+++ b/tar/sqfs2tar.c
@@ -19,13 +19,14 @@
 static struct option long_opts[] = {
 	{ "subdir", required_argument, NULL, 'd' },
 	{ "keep-as-dir", no_argument, NULL, 'k' },
+	{ "root-becomes", required_argument, NULL, 'r' },
 	{ "no-skip", no_argument, NULL, 's' },
 	{ "no-xattr", no_argument, NULL, 'X' },
 	{ "help", no_argument, NULL, 'h' },
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "d:ksXhV";
+static const char *short_opts = "d:kr:sXhV";
 
 static const char *usagestr =
 "Usage: sqfs2tar [OPTIONS...] <sqfsfile>\n"
@@ -41,6 +42,14 @@ static const char *usagestr =
 "                            one is specified, it becomes the new root of\n"
 "                            node of the archive file system tree.\n"
 "\n"
+"  --root-becomes, -r <dir>  Turn the root inode into a directory with the\n"
+"                            specified name. Everything else will be stored\n"
+"                            inside this directory. The special value '.' is\n"
+"                            allowed to prefix all tar paths with './' and\n"
+"                            add an entry named '.' for the root inode.\n"
+"                            If this option isn't used, all meta data stored\n"
+"                            in the root inode IS LOST!\n"
+"\n"
 "  --keep-as-dir, -k         If --subdir is used only once, don't make the\n"
 "                            subdir the archive root, instead keep it as\n"
 "                            prefix for all unpacked files.\n"
@@ -68,6 +77,7 @@ static bool dont_skip = false;
 static bool keep_as_dir = false;
 static bool no_xattr = false;
 
+static char *root_becomes = NULL;
 static char **subdirs = NULL;
 static size_t num_subdirs = 0;
 static size_t max_subdirs = 0;
@@ -114,6 +124,26 @@ static void process_args(int argc, char **argv)
 
 			++num_subdirs;
 			break;
+		case 'r':
+			free(root_becomes);
+			root_becomes = strdup(optarg);
+			if (root_becomes == NULL)
+				goto fail_errno;
+
+			if (strcmp(root_becomes, "./") == 0)
+				root_becomes[1] = '\0';
+
+			if (strcmp(root_becomes, ".") == 0)
+				break;
+
+			if (canonicalize_name(root_becomes) != 0 ||
+			    strlen(root_becomes) == 0) {
+				fprintf(stderr,
+					"Invalid root directory '%s'.\n",
+					optarg);
+				goto fail_arg;
+			}
+			break;
 		case 'k':
 			keep_as_dir = true;
 			break;
@@ -165,6 +195,7 @@ out_success:
 out_exit:
 	for (idx = 0; idx < num_subdirs; ++idx)
 		free(subdirs[idx]);
+	free(root_becomes);
 	free(subdirs);
 	exit(ret);
 }
@@ -260,31 +291,62 @@ fail:
 static int write_tree_dfs(const sqfs_tree_node_t *n)
 {
 	tar_xattr_t *xattr = NULL, *xit;
-	char *name, *target;
+	char *name, *target, *temp;
 	struct stat sb;
+	size_t len;
 	int ret;
 
-	if (n->parent == NULL && S_ISDIR(n->inode->base.mode))
-		goto skip_hdr;
+	if (n->parent == NULL) {
+		if (root_becomes == NULL)
+			goto skip_hdr;
 
-	if (!is_filename_sane((const char *)n->name)) {
-		fprintf(stderr, "Found a file named '%s', skipping.\n",
-			n->name);
-		if (dont_skip) {
-			fputs("Not allowed to skip files, aborting!\n", stderr);
+		len = strlen(root_becomes);
+		name = malloc(len + 2);
+		if (name == NULL) {
+			perror("creating root directory");
 			return -1;
 		}
-		return 0;
-	}
 
-	name = sqfs_tree_node_get_path(n);
-	if (name == NULL) {
-		perror("resolving tree node path");
-		return -1;
-	}
+		memcpy(name, root_becomes, len);
+		name[len] = '/';
+		name[len + 1] = '\0';
+	} else {
+		if (!is_filename_sane((const char *)n->name)) {
+			fprintf(stderr, "Found a file named '%s', skipping.\n",
+				n->name);
+			if (dont_skip) {
+				fputs("Not allowed to skip files, aborting!\n",
+				      stderr);
+				return -1;
+			}
+			return 0;
+		}
 
-	if (canonicalize_name(name))
-		goto out_skip;
+		name = sqfs_tree_node_get_path(n);
+		if (name == NULL) {
+			perror("resolving tree node path");
+			return -1;
+		}
+
+		if (canonicalize_name(name))
+			goto out_skip;
+
+		if (root_becomes != NULL) {
+			len = strlen(root_becomes);
+			temp = realloc(name, strlen(name) + len + 2);
+
+			if (temp == NULL) {
+				perror("assembling tar entry filename");
+				free(name);
+				return -1;
+			}
+
+			name = temp;
+			memmove(name + len + 1, name, strlen(name) + 1);
+			memcpy(name, root_becomes, len);
+			name[len] = '/';
+		}
+	}
 
 	inode_stat(n, &sb);
 
@@ -565,5 +627,6 @@ out_dirs:
 	for (i = 0; i < num_subdirs; ++i)
 		free(subdirs[i]);
 	free(subdirs);
+	free(root_becomes);
 	return status;
 }
diff --git a/tar/tar2sqfs.c b/tar/tar2sqfs.c
index 56ae5dc..cc0ccfb 100644
--- a/tar/tar2sqfs.c
+++ b/tar/tar2sqfs.c
@@ -20,6 +20,7 @@
 #endif
 
 static struct option long_opts[] = {
+	{ "root-becomes", required_argument, NULL, 'r' },
 	{ "compressor", required_argument, NULL, 'c' },
 	{ "block-size", required_argument, NULL, 'b' },
 	{ "dev-block-size", required_argument, NULL, 'B' },
@@ -37,7 +38,7 @@ static struct option long_opts[] = {
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "c:b:B:d:X:j:Q:sxekfqhV";
+static const char *short_opts = "r:c:b:B:d:X:j:Q:sxekfqhV";
 
 static const char *usagestr =
 "Usage: tar2sqfs [OPTIONS...] <sqfsfile>\n"
@@ -47,6 +48,13 @@ static const char *usagestr =
 "\n"
 "Possible options:\n"
 "\n"
+"  --root-becomes, -r <dir>    The specified directory becomes the root.\n"
+"                              Only its children are packed into the image\n"
+"                              and its attributes (ownership, permissions,\n"
+"                              xattrs, ...) are stored in the root inode.\n"
+"                              If not set and a tarbal has an entry for './'\n"
+"                              or '/', it becomes the root instead.\n"
+"\n"
 "  --compressor, -c <name>     Select the compressor to use.\n"
 "                              A list of available compressors is below.\n"
 "  --comp-extra, -X <options>  A comma seperated list of extra options for\n"
@@ -93,6 +101,7 @@ static bool keep_time = true;
 static sqfs_writer_cfg_t cfg;
 static sqfs_writer_t sqfs;
 static FILE *input_file = NULL;
+static char *root_becomes = NULL;
 
 static void process_args(int argc, char **argv)
 {
@@ -156,6 +165,22 @@ static void process_args(int argc, char **argv)
 		case 'k':
 			keep_time = false;
 			break;
+		case 'r':
+			free(root_becomes);
+			root_becomes = strdup(optarg);
+			if (root_becomes == NULL) {
+				perror("copying root directory name");
+				exit(EXIT_FAILURE);
+			}
+
+			if (canonicalize_name(root_becomes) != 0 ||
+			    strlen(root_becomes) == 0) {
+				fprintf(stderr,
+					"Invalid root directory '%s'.\n",
+					optarg);
+				goto fail_arg;
+			}
+			break;
 		case 's':
 			dont_skip = true;
 			break;
@@ -273,7 +298,7 @@ static int write_file(tar_header_decoded_t *hdr, file_info_t *fi,
 			    filesize : hdr->record_size);
 }
 
-static int copy_xattr(tree_node_t *node, tar_header_decoded_t *hdr)
+static int copy_xattr(tree_node_t *node, const tar_header_decoded_t *hdr)
 {
 	tar_xattr_t *xattr;
 	int ret;
@@ -346,14 +371,39 @@ fail_errno:
 	return -1;
 }
 
+static int set_root_attribs(const tar_header_decoded_t *hdr)
+{
+	if (!S_ISDIR(hdr->sb.st_mode)) {
+		fprintf(stderr, "'%s' is not a directory!\n", hdr->name);
+		return -1;
+	}
+
+	sqfs.fs.root->uid = hdr->sb.st_uid;
+	sqfs.fs.root->gid = hdr->sb.st_gid;
+	sqfs.fs.root->mode = hdr->sb.st_mode;
+
+	if (keep_time)
+		sqfs.fs.root->mod_time = hdr->sb.st_mtime;
+
+	if (!cfg.no_xattr) {
+		if (copy_xattr(sqfs.fs.root, hdr))
+			return -1;
+	}
+
+	return 0;
+}
+
 static int process_tar_ball(void)
 {
+	bool skip, is_root, is_prefixed;
 	tar_header_decoded_t hdr;
 	sqfs_u64 offset, count;
 	sparse_map_t *m;
-	bool skip;
+	size_t rootlen;
 	int ret;
 
+	rootlen = root_becomes == NULL ? 0 : strlen(root_becomes);
+
 	for (;;) {
 		ret = read_header(input_file, &hdr);
 		if (ret > 0)
@@ -362,15 +412,8 @@ static int process_tar_ball(void)
 			return -1;
 
 		skip = false;
-
-		if (hdr.name != NULL && strcmp(hdr.name, "./") == 0 &&
-		    S_ISDIR(hdr.sb.st_mode)) {
-			/* XXX: tar entries might be prefixed with ./ which is
-			   stripped by cannonicalize_name, but the tar file may
-			   contain a directory entry named './' */
-			clear_header(&hdr);
-			continue;
-		}
+		is_root = false;
+		is_prefixed = true;
 
 		if (hdr.name == NULL || canonicalize_name(hdr.name) != 0) {
 			fprintf(stderr, "skipping '%s' (invalid name)\n",
@@ -378,9 +421,41 @@ static int process_tar_ball(void)
 			skip = true;
 		}
 
-		if (hdr.name[0] == '\0') {
-			fputs("skipping entry with empty name\n", stderr);
-			skip = true;
+		if (root_becomes != NULL) {
+			if (strncmp(hdr.name, root_becomes, rootlen) == 0) {
+				if (hdr.name[rootlen] == '\0') {
+					is_root = true;
+				} else if (hdr.name[rootlen] != '/') {
+					is_prefixed = false;
+				}
+			} else {
+				is_prefixed = false;
+			}
+
+			if (is_prefixed && !is_root) {
+				memmove(hdr.name, hdr.name + rootlen + 1,
+					strlen(hdr.name + rootlen + 1) + 1);
+			}
+
+			if (is_prefixed && hdr.name[0] == '\0') {
+				fputs("skipping entry with empty name\n",
+				      stderr);
+				skip = true;
+			}
+		} else if (hdr.name[0] == '\0') {
+			is_root = true;
+		}
+
+		if (!is_prefixed) {
+			clear_header(&hdr);
+			continue;
+		}
+
+		if (is_root) {
+			if (set_root_attribs(&hdr))
+				goto fail;
+			clear_header(&hdr);
+			continue;
 		}
 
 		if (!skip && hdr.unknown_record) {