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>

1 files changed, 53 insertions, 6 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);