unsquashfs: add flags to filter what file types to unpack

This allows the user to skip stuff like device special files (which
non-root can't create anyway) or to not create symlinks/fifos etc...

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

4 files changed, 140 insertions, 21 deletions

diff --git a/unpack/read_fstree.c b/unpack/read_fstree.c
index a6903b0..f200243 100644
--- a/unpack/read_fstree.c
+++ b/unpack/read_fstree.c
@@ -2,15 +2,36 @@
 #include "unsquashfs.h"
 
 
+static int should_skip(int type, int flags)
+{
+	switch (type) {
+	case SQFS_INODE_BDEV:
+	case SQFS_INODE_CDEV:
+	case SQFS_INODE_EXT_CDEV:
+	case SQFS_INODE_EXT_BDEV:
+		return (flags & UNPACK_NO_DEVICES);
+	case SQFS_INODE_SLINK:
+	case SQFS_INODE_EXT_SLINK:
+		return (flags & UNPACK_NO_SLINKS);
+	case SQFS_INODE_SOCKET:
+	case SQFS_INODE_EXT_SOCKET:
+		return(flags & UNPACK_NO_SOCKETS);
+	case SQFS_INODE_FIFO:
+	case SQFS_INODE_EXT_FIFO:
+		return (flags & UNPACK_NO_FIFO);
+	}
+	return 0;
+}
+
 static int fill_dir(meta_reader_t *ir, meta_reader_t *dr, tree_node_t *root,
-		    sqfs_super_t *super, id_table_t *idtbl)
+		    sqfs_super_t *super, id_table_t *idtbl, int flags)
 {
 	sqfs_inode_generic_t *inode;
 	sqfs_dir_header_t hdr;
 	sqfs_dir_entry_t *ent;
+	tree_node_t *n, *prev;
 	uint64_t block_start;
 	size_t size, diff;
-	tree_node_t *n;
 	uint32_t i;
 
 	block_start = root->data.dir->start_block;
@@ -35,6 +56,11 @@ static int fill_dir(meta_reader_t *ir, meta_reader_t *dr, tree_node_t *root,
 			diff = sizeof(*ent) + strlen((char *)ent->name);
 			size -= diff > size ? size : diff;
 
+			if (should_skip(ent->type, flags)) {
+				free(ent);
+				continue;
+			}
+
 			inode = meta_reader_read_inode(ir, super,
 						       hdr.start_block,
 						       ent->offset);
@@ -58,17 +84,38 @@ static int fill_dir(meta_reader_t *ir, meta_reader_t *dr, tree_node_t *root,
 		}
 	}
 
-	for (n = root->data.dir->children; n != NULL; n = n->next) {
+	n = root->data.dir->children;
+	prev = NULL;
+
+	while (n != NULL) {
 		if (S_ISDIR(n->mode)) {
-			if (fill_dir(ir, dr, n, super, idtbl))
+			if (fill_dir(ir, dr, n, super, idtbl, flags))
 				return -1;
+
+			if (n->data.dir->children == NULL &&
+			    (flags & UNPACK_NO_EMPTY)) {
+				if (prev == NULL) {
+					root->data.dir->children = n->next;
+					free(n);
+					n = root->data.dir->children;
+				} else {
+					prev->next = n->next;
+					free(n);
+					n = prev->next;
+				}
+				continue;
+			}
 		}
+
+		prev = n;
+		n = n->next;
 	}
 
 	return 0;
 }
 
-int read_fstree(fstree_t *out, int fd, sqfs_super_t *super, compressor_t *cmp)
+int read_fstree(fstree_t *out, int fd, sqfs_super_t *super, compressor_t *cmp,
+		int flags)
 {
 	sqfs_inode_generic_t *root;
 	meta_reader_t *ir, *dr;
@@ -119,7 +166,7 @@ int read_fstree(fstree_t *out, int fd, sqfs_super_t *super, compressor_t *cmp)
 	if (out->root == NULL)
 		goto out_id;
 
-	if (fill_dir(ir, dr, out->root, super, &idtbl))
+	if (fill_dir(ir, dr, out->root, super, &idtbl, flags))
 		goto fail_fs;
 
 	fstree_sort(out);
diff --git a/unpack/restore_fstree.c b/unpack/restore_fstree.c
index 56c3cc5..8ef21c3 100644
--- a/unpack/restore_fstree.c
+++ b/unpack/restore_fstree.c
@@ -3,14 +3,14 @@
 
 static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 			     size_t block_size, frag_reader_t *frag,
-			     int sqfsfd)
+			     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, n->mode) &&
+			if (mkdirat(dirfd, n->name, 0755) &&
 			    errno != EEXIST) {
 				fprintf(stderr, "mkdir %s: %s\n",
 					n->name, strerror(errno));
@@ -25,7 +25,7 @@ static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 			}
 
 			if (restore_directory(fd, n, cmp, block_size,
-					      frag, sqfsfd)) {
+					      frag, sqfsfd, flags)) {
 				close(fd);
 				return -1;
 			}
@@ -42,7 +42,8 @@ static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 			break;
 		case S_IFSOCK:
 		case S_IFIFO:
-			if (mknodat(dirfd, n->name, n->mode, 0)) {
+			if (mknodat(dirfd, n->name,
+				    (n->mode & S_IFMT) | 0700, 0)) {
 				fprintf(stderr, "creating %s: %s\n",
 					n->name, strerror(errno));
 				return -1;
@@ -50,7 +51,8 @@ static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 			break;
 		case S_IFBLK:
 		case S_IFCHR:
-			if (mknodat(dirfd, n->name, n->mode, n->data.devno)) {
+			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;
@@ -58,7 +60,7 @@ static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 			break;
 		case S_IFREG:
 			fd = openat(dirfd, n->name,
-				    O_WRONLY | O_CREAT | O_EXCL, n->mode);
+				    O_WRONLY | O_CREAT | O_EXCL, 0600);
 			if (fd < 0) {
 				fprintf(stderr, "creating %s: %s\n",
 					n->name, strerror(errno));
@@ -76,13 +78,32 @@ static int restore_directory(int dirfd, tree_node_t *n, compressor_t *cmp,
 		default:
 			break;
 		}
+
+		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;
 }
 
 int restore_fstree(const char *rootdir, tree_node_t *root, compressor_t *cmp,
-		   size_t block_size, frag_reader_t *frag, int sqfsfd)
+		   size_t block_size, frag_reader_t *frag, int sqfsfd,
+		   int flags)
 {
 	int dirfd;
 
@@ -95,7 +116,8 @@ 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)) {
+	if (restore_directory(dirfd, root, cmp, block_size, frag,
+			      sqfsfd, flags)) {
 		close(dirfd);
 		return -1;
 	}
diff --git a/unpack/unsquashfs.c b/unpack/unsquashfs.c
index 178def4..8ec1b94 100644
--- a/unpack/unsquashfs.c
+++ b/unpack/unsquashfs.c
@@ -12,11 +12,18 @@ static struct option long_opts[] = {
 	{ "list", required_argument, NULL, 'l' },
 	{ "cat", required_argument, NULL, 'c' },
 	{ "unpack-root", required_argument, NULL, 'u' },
+	{ "no-dev", no_argument, NULL, 'D' },
+	{ "no-sock", no_argument, NULL, 'S' },
+	{ "no-fifo", no_argument, NULL, 'F' },
+	{ "no-slink", no_argument, NULL, 'L' },
+	{ "no-empty-dir", no_argument, NULL, 'E' },
+	{ "chmod", no_argument, NULL, 'C' },
+	{ "chown", no_argument, NULL, 'O' },
 	{ "help", no_argument, NULL, 'h' },
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "l:c:u:hV";
+static const char *short_opts = "l:c:u:DSFLCOEhV";
 
 static const char *help_string =
 "Usage: %s [OPTIONS] <squashfs-file>\n"
@@ -29,7 +36,17 @@ static const char *help_string =
 "  --cat, -c <path>      If the specified path is a regular file in the,\n"
 "                        image, dump its contents to stdout.\n"
 "  --unpack-root <path>  Unpack the contents of the filesystem into the\n"
-"                        specified path\n"
+"                        specified path.\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"
+"  --no-slink, -L        Do not unpack symbolic links.\n"
+"  --no-empty-dir, -E    Do not unpack directories that would end up empty.\n"
+"  --chmod, -C           Change permission flags of unpacked files to those\n"
+"                        store in the squashfs image.\n"
+"  --chown, -O           Change ownership of unpacked files to the UID/GID\n"
+"                        set in the squashfs iamge.\n"
+"\n"
 "  --help, -h            Print help text and exit.\n"
 "  --version, -V         Print version information and exit.\n"
 "\n";
@@ -92,7 +109,7 @@ static char *get_path(char *old, const char *arg)
 
 int main(int argc, char **argv)
 {
-	int i, fd, status = EXIT_FAILURE, op = OP_NONE;
+	int i, fd, status = EXIT_FAILURE, op = OP_NONE, unpack_flags = 0;
 	const char *unpack_root = NULL;
 	frag_reader_t *frag = NULL;
 	char *cmdpath = NULL;
@@ -107,6 +124,27 @@ int main(int argc, char **argv)
 			break;
 
 		switch (i) {
+		case 'D':
+			unpack_flags |= UNPACK_NO_DEVICES;
+			break;
+		case 'S':
+			unpack_flags |= UNPACK_NO_SOCKETS;
+			break;
+		case 'F':
+			unpack_flags |= UNPACK_NO_FIFO;
+			break;
+		case 'L':
+			unpack_flags |= UNPACK_NO_SLINKS;
+			break;
+		case 'C':
+			unpack_flags |= UNPACK_CHMOD;
+			break;
+		case 'O':
+			unpack_flags |= UNPACK_CHOWN;
+			break;
+		case 'E':
+			unpack_flags |= UNPACK_NO_EMPTY;
+			break;
 		case 'c':
 			op = OP_CAT;
 			cmdpath = get_path(cmdpath, optarg);
@@ -178,7 +216,7 @@ int main(int argc, char **argv)
 	if (cmp == NULL)
 		goto out_fd;
 
-	if (read_fstree(&fs, fd, &super, cmp))
+	if (read_fstree(&fs, fd, &super, cmp, unpack_flags))
 		goto out_cmp;
 
 	switch (op) {
@@ -226,7 +264,7 @@ int main(int argc, char **argv)
 		}
 
 		if (restore_fstree(unpack_root, fs.root, cmp, super.block_size,
-				   frag, fd)) {
+				   frag, fd, unpack_flags)) {
 			goto out_fs;
 		}
 		break;
diff --git a/unpack/unsquashfs.h b/unpack/unsquashfs.h
index 5895fb8..a8784fc 100644
--- a/unpack/unsquashfs.h
+++ b/unpack/unsquashfs.h
@@ -19,12 +19,23 @@
 #include <fcntl.h>
 #include <stdio.h>
 
+enum UNPACK_FLAGS {
+	UNPACK_NO_DEVICES = 0x01,
+	UNPACK_NO_SOCKETS = 0x02,
+	UNPACK_NO_FIFO = 0x04,
+	UNPACK_NO_SLINKS = 0x08,
+	UNPACK_NO_EMPTY = 0x10,
+	UNPACK_CHMOD = 0x20,
+	UNPACK_CHOWN = 0x40,
+};
+
 tree_node_t *tree_node_from_inode(sqfs_inode_generic_t *inode,
 				  const id_table_t *idtbl,
 				  const char *name,
 				  size_t block_size);
 
-int read_fstree(fstree_t *out, int fd, sqfs_super_t *super, compressor_t *cmp);
+int read_fstree(fstree_t *out, int fd, sqfs_super_t *super, compressor_t *cmp,
+		int flags);
 
 void list_files(tree_node_t *node);
 
@@ -32,6 +43,7 @@ int extract_file(file_info_t *fi, compressor_t *cmp, size_t block_size,
 		 frag_reader_t *frag, int sqfsfd, int outfd);
 
 int restore_fstree(const char *rootdir, tree_node_t *root, compressor_t *cmp,
-		   size_t block_size, frag_reader_t *frag, int sqfsfd);
+		   size_t block_size, frag_reader_t *frag, int sqfsfd,
+		   int flags);
 
 #endif /* UNSQUASHFS_H */