Add unsquashfs stub

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

7 files changed, 166 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index d10a7fe..944a414 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,3 +19,4 @@ config.h
 *.a
 *~
 mksquashfs
+unsquashfs
diff --git a/Makefile.am b/Makefile.am
index 1b8284b..7fc95c3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,3 +10,4 @@ EXTRA_DIST = autogen.sh LICENSE
 
 include lib/Makemodule.am
 include mkfs/Makemodule.am
+include unpack/Makemodule.am
diff --git a/include/squashfs.h b/include/squashfs.h
index 30c7d3d..a690aad 100644
--- a/include/squashfs.h
+++ b/include/squashfs.h
@@ -184,4 +184,6 @@ int sqfs_super_init(sqfs_super_t *super, size_t block_size, uint32_t mtime,
 
 int sqfs_super_write(sqfs_super_t *super, int fd);
 
+int sqfs_super_read(sqfs_super_t *super, int fd);
+
 #endif /* SQUASHFS_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index c2d7dab..026e3f1 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -11,6 +11,7 @@ libsquashfs_a_SOURCES = include/meta_writer.h include/squashfs.h
 libsquashfs_a_SOURCES += lib/sqfs/meta_writer.c lib/sqfs/super.c
 libsquashfs_a_SOURCES += lib/sqfs/id_table.c include/id_table.h
 libsquashfs_a_SOURCES += lib/sqfs/table.c include/table.h
+libsquashfs_a_SOURCES += lib/sqfs/read_super.c
 
 libutil_a_SOURCES = lib/util/canonicalize_name.c lib/util/write_retry.c
 libutil_a_SOURCES += lib/util/read_retry.c include/util.h
diff --git a/lib/sqfs/read_super.c b/lib/sqfs/read_super.c
new file mode 100644
index 0000000..22dd822
--- /dev/null
+++ b/lib/sqfs/read_super.c
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "squashfs.h"
+#include "util.h"
+
+#include <endian.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int sqfs_super_read(sqfs_super_t *super, int fd)
+{
+	sqfs_super_t temp;
+	size_t block_size;
+	ssize_t ret;
+	int i;
+
+	if (lseek(fd, 0, SEEK_SET) == (off_t)-1)
+		goto fail_seek;
+
+	ret = read_retry(fd, &temp, sizeof(temp));
+
+	if (ret < 0) {
+		perror("reading super block");
+		return -1;
+	}
+
+	if ((size_t)ret < sizeof(temp)) {
+		fputs("reading super block: unexpected end of file\n", stderr);
+		return -1;
+	}
+
+	temp.magic = le32toh(temp.magic);
+	temp.inode_count = le32toh(temp.inode_count);
+	temp.modification_time = le32toh(temp.modification_time);
+	temp.block_size = le32toh(temp.block_size);
+	temp.fragment_entry_count = le32toh(temp.fragment_entry_count);
+	temp.compression_id = le16toh(temp.compression_id);
+	temp.block_log = le16toh(temp.block_log);
+	temp.flags = le16toh(temp.flags);
+	temp.id_count = le16toh(temp.id_count);
+	temp.version_major = le16toh(temp.version_major);
+	temp.version_minor = le16toh(temp.version_minor);
+	temp.root_inode_ref = le64toh(temp.root_inode_ref);
+	temp.bytes_used = le64toh(temp.bytes_used);
+	temp.id_table_start = le64toh(temp.id_table_start);
+	temp.xattr_id_table_start = le64toh(temp.xattr_id_table_start);
+	temp.inode_table_start = le64toh(temp.inode_table_start);
+	temp.directory_table_start = le64toh(temp.directory_table_start);
+	temp.fragment_table_start = le64toh(temp.fragment_table_start);
+	temp.export_table_start = le64toh(temp.export_table_start);
+
+	if (temp.magic != SQFS_MAGIC) {
+		fputs("Magic number missing. Not a squashfs image.\n", stderr);
+		return -1;
+	}
+
+	if ((temp.block_size - 1) & temp.block_size) {
+		fputs("Block size in image is not a power of 2!\n", stderr);
+		return -1;
+	}
+
+	block_size = 1;
+
+	for (i = 0; i < temp.block_log; ++i)
+		block_size <<= 1;
+
+	if (temp.block_size != block_size) {
+		fputs("Mismatch between block size and block log\n", stderr);
+		fputs("Filesystem probably currupted.\n", stderr);
+		return -1;
+	}
+
+	if (temp.compression_id < SQFS_COMP_MIN ||
+	    temp.compression_id > SQFS_COMP_MAX) {
+		fputs("Image uses an unsupported compressor\n", stderr);
+		return -1;
+	}
+
+	memcpy(super, &temp, sizeof(temp));
+	return 0;
+fail_seek:
+	perror("squashfs writing super block: seek on output file");
+	return -1;
+}
diff --git a/unpack/Makemodule.am b/unpack/Makemodule.am
new file mode 100644
index 0000000..190803e
--- /dev/null
+++ b/unpack/Makemodule.am
@@ -0,0 +1,12 @@
+unsquashfs_SOURCES = unpack/unsquashfs.c
+unsquashfs_LDADD = libsquashfs.a libfstree.a libcompress.a libutil.a
+
+if WITH_LZMA
+unsquashfs_LDADD += $(XZ_LIBS)
+endif
+
+if WITH_ZLIB
+unsquashfs_LDADD += $(ZLIB_LIBS)
+endif
+
+bin_PROGRAMS += unsquashfs
diff --git a/unpack/unsquashfs.c b/unpack/unsquashfs.c
new file mode 100644
index 0000000..4606366
--- /dev/null
+++ b/unpack/unsquashfs.c
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "squashfs.h"
+#include "compress.h"
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <fcntl.h>
+
+extern const char *__progname;
+
+int main(int argc, char **argv)
+{
+	int fd, status = EXIT_FAILURE;
+	sqfs_super_t super;
+	compressor_t *cmp;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <filename>\n", __progname);
+		return EXIT_FAILURE;
+	}
+
+	fd = open(argv[1], O_RDONLY);
+	if (fd < 0) {
+		perror(argv[1]);
+		return EXIT_FAILURE;
+	}
+
+	if (sqfs_super_read(&super, fd))
+		goto out;
+
+	if ((super.version_major != SQFS_VERSION_MAJOR) ||
+	    (super.version_minor != SQFS_VERSION_MINOR)) {
+		fprintf(stderr,
+			"The image uses squashfs version %d.%d\n"
+			"We currently only supports version %d.%d (sorry).\n",
+			super.version_major, super.version_minor,
+			SQFS_VERSION_MAJOR, SQFS_VERSION_MINOR);
+		goto out;
+	}
+
+	if (super.flags & SQFS_FLAG_COMPRESSOR_OPTIONS) {
+		fputs("Image has been built with compressor options.\n"
+		      "This is not yet supported.\n",
+		      stderr);
+		goto out;
+	}
+
+	if (!compressor_exists(super.compression_id)) {
+		fputs("Image uses a compressor that has not been built in\n",
+		      stderr);
+		goto out;
+	}
+
+	cmp = compressor_create(super.compression_id, false, super.block_size);
+	if (cmp == NULL)
+		goto out;
+
+	status = EXIT_SUCCESS;
+
+	cmp->destroy(cmp);
+out:
+	close(fd);
+	return status;
+}