unsquashfs: add code to unpack the entire file system

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

7 files changed, 184 insertions, 8 deletions

diff --git a/include/util.h b/include/util.h
index b1a98c0..1ec551c 100644
--- a/include/util.h
+++ b/include/util.h
@@ -12,4 +12,6 @@ ssize_t read_retry(int fd, void *buffer, size_t size);
 
 void print_version(void);
 
+int mkdir_p(const char *path);
+
 #endif /* UTIL_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index f23d9b7..691d6df 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -19,7 +19,7 @@ libsquashfs_a_SOURCES += include/frag_reader.h
 
 libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_retry.c
 libutil_a_SOURCES += lib/util/read_retry.c include/util.h
-libutil_a_SOURCES += lib/util/print_version.c
+libutil_a_SOURCES += lib/util/print_version.c lib/util/mkdir_p.c
 
 if WITH_ZLIB
 libcompress_a_SOURCES += lib/comp/zlib.c
diff --git a/lib/util/mkdir_p.c b/lib/util/mkdir_p.c
new file mode 100644
index 0000000..7d1e052
--- /dev/null
+++ b/lib/util/mkdir_p.c
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <alloca.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "util.h"
+
+int mkdir_p(const char *path)
+{
+	size_t i, len;
+	char *buffer;
+
+	while (path[0] == '/' && path[1] == '/')
+		++path;
+
+	if (*path == '\0' || (path[0] == '/' && path[1] == '\0'))
+		return 0;
+
+	len = strlen(path) + 1;
+	buffer = alloca(len);
+
+	for (i = 0; i < len; ++i) {
+		if (i > 0 && (path[i] == '/' || path[i] == '\0')) {
+			buffer[i] = '\0';
+
+			if (mkdir(buffer, 0755) != 0) {
+				if (errno != EEXIST) {
+					fprintf(stderr, "mkdir %s: %s\n",
+						buffer, strerror(errno));
+					return -1;
+				}
+			}
+		}
+
+		buffer[i] = path[i];
+	}
+
+	return 0;
+}
diff --git a/unpack/Makemodule.am b/unpack/Makemodule.am
index a8fd2e7..7d71bf5 100644
--- a/unpack/Makemodule.am
+++ b/unpack/Makemodule.am
@@ -1,6 +1,7 @@
 unsquashfs_SOURCES = unpack/unsquashfs.c unpack/tree_node_from_inode.c
 unsquashfs_SOURCES += unpack/unsquashfs.h unpack/read_fstree.c
 unsquashfs_SOURCES += unpack/list_files.c unpack/extract_file.c
+unsquashfs_SOURCES += unpack/restore_fstree.c
 unsquashfs_LDADD = libsquashfs.a libfstree.a libcompress.a libutil.a
 
 if WITH_LZMA
diff --git a/unpack/restore_fstree.c b/unpack/restore_fstree.c
new file mode 100644
index 0000000..56c3cc5
--- /dev/null
+++ b/unpack/restore_fstree.c
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "unsquashfs.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 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) &&
+			    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;
+			}
+
+			if (restore_directory(fd, n, cmp, block_size,
+					      frag, sqfsfd)) {
+				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, 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, 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, n->mode);
+			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;
+		default:
+			break;
+		}
+	}
+
+	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)
+{
+	int dirfd;
+
+	if (mkdir_p(rootdir))
+		return -1;
+
+	dirfd = open(rootdir, O_RDONLY | O_DIRECTORY);
+	if (dirfd < 0) {
+		perror(rootdir);
+		return -1;
+	}
+
+	if (restore_directory(dirfd, root, cmp, block_size, frag, sqfsfd)) {
+		close(dirfd);
+		return -1;
+	}
+
+	close(dirfd);
+	return 0;
+}
diff --git a/unpack/unsquashfs.c b/unpack/unsquashfs.c
index 90a7583..178def4 100644
--- a/unpack/unsquashfs.c
+++ b/unpack/unsquashfs.c
@@ -5,16 +5,18 @@ enum {
 	OP_NONE = 0,
 	OP_LS,
 	OP_CAT,
+	OP_UNPACK,
 };
 
 static struct option long_opts[] = {
 	{ "list", required_argument, NULL, 'l' },
 	{ "cat", required_argument, NULL, 'c' },
+	{ "unpack-root", required_argument, NULL, 'u' },
 	{ "help", no_argument, NULL, 'h' },
 	{ "version", no_argument, NULL, 'V' },
 };
 
-static const char *short_opts = "l:hV";
+static const char *short_opts = "l:c:u:hV";
 
 static const char *help_string =
 "Usage: %s [OPTIONS] <squashfs-file>\n"
@@ -22,12 +24,14 @@ static const char *help_string =
 "View or extract the contents of a squashfs image.\n"
 "\n"
 "Possible options:\n"
-"  --list, -l <path>  Produce a directory listing for a given path in the\n"
-"                     squashfs image.\n"
-"  --cat, -c <path>   If the specified path is a regular file in the image,\n"
-"                     dump its contents to stdout.\n"
-"  --help, -h         Print help text and exit.\n"
-"  --version, -V      Print version information and exit.\n"
+"  --list, -l <path>     Produce a directory listing for a given path in the\n"
+"                        squashfs image.\n"
+"  --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"
+"  --help, -h            Print help text and exit.\n"
+"  --version, -V         Print version information and exit.\n"
 "\n";
 
 extern const char *__progname;
@@ -89,6 +93,7 @@ static char *get_path(char *old, const char *arg)
 int main(int argc, char **argv)
 {
 	int i, fd, status = EXIT_FAILURE, op = OP_NONE;
+	const char *unpack_root = NULL;
 	frag_reader_t *frag = NULL;
 	char *cmdpath = NULL;
 	sqfs_super_t super;
@@ -110,6 +115,10 @@ int main(int argc, char **argv)
 			op = OP_LS;
 			cmdpath = get_path(cmdpath, optarg);
 			break;
+		case 'u':
+			op = OP_UNPACK;
+			unpack_root = optarg;
+			break;
 		case 'h':
 			printf(help_string, __progname);
 			status = EXIT_SUCCESS;
@@ -207,6 +216,20 @@ int main(int argc, char **argv)
 			goto out_fs;
 		}
 		break;
+	case OP_UNPACK:
+		if (super.fragment_entry_count > 0 &&
+		    super.fragment_table_start < super.bytes_used &&
+		    !(super.flags & SQFS_FLAG_NO_FRAGMENTS)) {
+			frag = frag_reader_create(&super, fd, cmp);
+			if (frag == NULL)
+				goto out_fs;
+		}
+
+		if (restore_fstree(unpack_root, fs.root, cmp, super.block_size,
+				   frag, fd)) {
+			goto out_fs;
+		}
+		break;
 	}
 
 	status = EXIT_SUCCESS;
diff --git a/unpack/unsquashfs.h b/unpack/unsquashfs.h
index 0e8854b..5895fb8 100644
--- a/unpack/unsquashfs.h
+++ b/unpack/unsquashfs.h
@@ -31,4 +31,7 @@ void list_files(tree_node_t *node);
 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);
+
 #endif /* UNSQUASHFS_H */