rdsquashfs: add ability to unpack only a sub tree of the file system

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

2 files changed, 107 insertions, 84 deletions

diff --git a/unpack/rdsquashfs.c b/unpack/rdsquashfs.c
index ec14e0e..4b3a573 100644
--- a/unpack/rdsquashfs.c
+++ b/unpack/rdsquashfs.c
@@ -12,6 +12,7 @@ static struct option long_opts[] = {
 	{ "list", required_argument, NULL, 'l' },
 	{ "cat", required_argument, NULL, 'c' },
 	{ "unpack-root", required_argument, NULL, 'u' },
+	{ "unpack-path", required_argument, NULL, 'p' },
 	{ "no-dev", no_argument, NULL, 'D' },
 	{ "no-sock", no_argument, NULL, 'S' },
 	{ "no-fifo", no_argument, NULL, 'F' },
@@ -23,7 +24,7 @@ static struct option long_opts[] = {
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "l:c:u:DSFLCOEhV";
+static const char *short_opts = "l:c:u:p:DSFLCOEhV";
 
 static const char *help_string =
 "Usage: %s [OPTIONS] <squashfs-file>\n"
@@ -37,6 +38,8 @@ static const char *help_string =
 "                        image, dump its contents to stdout.\n"
 "  --unpack-root <path>  Unpack the contents of the filesystem into the\n"
 "                        specified path.\n"
+"  --unpack-path <path>  If specified, unpack this sub directory from the\n"
+"                        image instead of the filesystem root.\n"
 "  --no-dev, -D          Do not unpack device special files.\n"
 "  --no-sock, -S         Do not unpack socket files.\n"
 "  --no-fifo, -F         Do not unpack named pipes.\n"
@@ -157,6 +160,9 @@ int main(int argc, char **argv)
 			op = OP_UNPACK;
 			unpack_root = optarg;
 			break;
+		case 'p':
+			cmdpath = get_path(cmdpath, optarg);
+			break;
 		case 'h':
 			printf(help_string, __progname);
 			status = EXIT_SUCCESS;
@@ -255,6 +261,16 @@ int main(int argc, char **argv)
 		}
 		break;
 	case OP_UNPACK:
+		if (cmdpath == NULL) {
+			n = fs.root;
+		} else {
+			n = find_node(fs.root, cmdpath);
+			if (n == NULL) {
+				perror(cmdpath);
+				goto out_fs;
+			}
+		}
+
 		if (super.fragment_entry_count > 0 &&
 		    super.fragment_table_start < super.bytes_used &&
 		    !(super.flags & SQFS_FLAG_NO_FRAGMENTS)) {
@@ -263,7 +279,7 @@ int main(int argc, char **argv)
 				goto out_fs;
 		}
 
-		if (restore_fstree(unpack_root, fs.root, cmp, super.block_size,
+		if (restore_fstree(unpack_root, n, cmp, super.block_size,
 				   frag, fd, unpack_flags)) {
 			goto out_fs;
 		}
diff --git a/unpack/restore_fstree.c b/unpack/restore_fstree.c
index 5a20c5f..270b25a 100644
--- a/unpack/restore_fstree.c
+++ b/unpack/restore_fstree.c
@@ -1,103 +1,99 @@
 /* SPDX-License-Identifier: GPL-3.0-or-later */
 #include "rdsquashfs.h"
 
-static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
-			     size_t block_size, frag_reader_t *frag,
-			     int sqfsfd, int flags)
+static int create_node(int dirfd, tree_node_t *n, compressor_t *cmp,
+		       size_t block_size, frag_reader_t *frag,
+		       int sqfsfd, int flags)
 {
 	int fd;
 
-	for (n = n->data.dir->children; n != NULL; n = n->next) {
-		switch (n->mode & S_IFMT) {
-		case S_IFDIR:
-			if (mkdirat(dirfd, n->name, 0755) &&
-			    errno != EEXIST) {
-				fprintf(stderr, "mkdir %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
+	switch (n->mode & S_IFMT) {
+	case S_IFDIR:
+		if (mkdirat(dirfd, n->name, 0755) && errno != EEXIST) {
+			fprintf(stderr, "mkdir %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
 
-			fd = openat(dirfd, n->name, O_RDONLY | O_DIRECTORY);
-			if (fd < 0) {
-				fprintf(stderr, "open dir %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
+		fd = openat(dirfd, n->name, O_RDONLY | O_DIRECTORY);
+		if (fd < 0) {
+			fprintf(stderr, "open dir %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
 
-			if (restore_directory(fd, n, cmp, block_size,
-					      frag, sqfsfd, flags)) {
+		for (n = n->data.dir->children; n != NULL; n = n->next) {
+			if (create_node(fd, n, cmp, block_size, frag, sqfsfd,
+					flags)) {
 				close(fd);
 				return -1;
 			}
+		}
 
-			close(fd);
-			break;
-		case S_IFLNK:
-			if (symlinkat(n->data.slink_target, dirfd, n->name)) {
-				fprintf(stderr, "ln -s %s %s: %s\n",
-					n->data.slink_target, n->name,
-					strerror(errno));
-				return -1;
-			}
-			break;
-		case S_IFSOCK:
-		case S_IFIFO:
-			if (mknodat(dirfd, n->name,
-				    (n->mode & S_IFMT) | 0700, 0)) {
-				fprintf(stderr, "creating %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
-			break;
-		case S_IFBLK:
-		case S_IFCHR:
-			if (mknodat(dirfd, n->name, (n->mode & S_IFMT),
-				    n->data.devno)) {
-				fprintf(stderr, "creating device %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
-			break;
-		case S_IFREG:
-			fd = openat(dirfd, n->name,
-				    O_WRONLY | O_CREAT | O_EXCL, 0600);
-			if (fd < 0) {
-				fprintf(stderr, "creating %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
-
-			if (extract_file(n->data.file, cmp, block_size,
-					 frag, sqfsfd, fd)) {
-				close(fd);
-				return -1;
-			}
+		close(fd);
+		break;
+	case S_IFLNK:
+		if (symlinkat(n->data.slink_target, dirfd, n->name)) {
+			fprintf(stderr, "ln -s %s %s: %s\n",
+				n->data.slink_target, n->name,
+				strerror(errno));
+			return -1;
+		}
+		break;
+	case S_IFSOCK:
+	case S_IFIFO:
+		if (mknodat(dirfd, n->name, (n->mode & S_IFMT) | 0700, 0)) {
+			fprintf(stderr, "creating %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
+		break;
+	case S_IFBLK:
+	case S_IFCHR:
+		if (mknodat(dirfd, n->name, (n->mode & S_IFMT),
+			    n->data.devno)) {
+			fprintf(stderr, "creating device %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
+		break;
+	case S_IFREG:
+		fd = openat(dirfd, n->name, O_WRONLY | O_CREAT | O_EXCL, 0600);
+		if (fd < 0) {
+			fprintf(stderr, "creating %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
 
+		if (extract_file(n->data.file, cmp, block_size,
+				 frag, sqfsfd, fd)) {
 			close(fd);
-			break;
-		default:
-			break;
+			return -1;
 		}
 
-		if (flags & UNPACK_CHOWN) {
-			if (fchownat(dirfd, n->name, n->uid, n->gid,
-				     AT_SYMLINK_NOFOLLOW)) {
-				fprintf(stderr, "chown %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
-		}
+		close(fd);
+		break;
+	default:
+		break;
+	}
 
-		if (flags & UNPACK_CHMOD) {
-			if (fchmodat(dirfd, n->name, n->mode,
-				     AT_SYMLINK_NOFOLLOW)) {
-				fprintf(stderr, "chmod %s: %s\n",
-					n->name, strerror(errno));
-				return -1;
-			}
+	if (flags & UNPACK_CHOWN) {
+		if (fchownat(dirfd, n->name, n->uid, n->gid,
+			     AT_SYMLINK_NOFOLLOW)) {
+			fprintf(stderr, "chown %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
 		}
 	}
 
+	if (flags & UNPACK_CHMOD) {
+		if (fchmodat(dirfd, n->name, n->mode,
+			     AT_SYMLINK_NOFOLLOW)) {
+			fprintf(stderr, "chmod %s: %s\n",
+				n->name, strerror(errno));
+			return -1;
+		}
+	}
 	return 0;
 }
 
@@ -105,6 +101,7 @@ int restore_fstree(const char *rootdir, tree_node_t *root, compressor_t *cmp,
 		   size_t block_size, frag_reader_t *frag, int sqfsfd,
 		   int flags)
 {
+	tree_node_t *n;
 	int dirfd;
 
 	if (mkdir_p(rootdir))
@@ -116,8 +113,18 @@ int restore_fstree(const char *rootdir, tree_node_t *root, compressor_t *cmp,
 		return -1;
 	}
 
-	if (restore_directory(dirfd, root, cmp, block_size, frag,
-			      sqfsfd, flags)) {
+	if (S_ISDIR(root->mode)) {
+		for (n = root->data.dir->children; n != NULL; n = n->next) {
+			if (create_node(dirfd, n, cmp, block_size, frag,
+					sqfsfd, flags)) {
+				close(dirfd);
+				return -1;
+			}
+		}
+		return 0;
+	}
+
+	if (create_node(dirfd, root, cmp, block_size, frag, sqfsfd, flags)) {
 		close(dirfd);
 		return -1;
 	}