pmbootstrap/pmb/parse/bootimg.py

# Copyright 2021 Oliver Smith
# SPDX-License-Identifier: GPL-3.0-or-later
import os
import logging
import pmb


def is_dtb(path):
    if not os.path.isfile(path):
        return False
    with open(path, 'rb') as f:
        # Check FDT magic identifier (0xd00dfeed)
        return f.read(4) == b'\xd0\x0d\xfe\xed'


def has_mtk_header(path, supported_label):
    with open(path, 'rb') as f:
        # Check Mediatek header (0x88168858)
        if not f.read(4) == b'\x88\x16\x88\x58':
            return False
        f.seek(8)
        label = f.read(32).decode("utf-8").rstrip('\0')
        # We only support hardcoded labels for now as the known devices only
        # use KERNEL & ROOTFS for kernel and ramdisk respectively. To change
        # this, deviceinfo would need to store the label and
        # postmarketos-mkinitfs would need to use that label.
        if label != supported_label:
            raise RuntimeError(f"Only '{supported_label}' is supported as"
                               f" label, but your device has '{label}'. Please"
                               f" create an issue and attach your boot.img:"
                               f" https://postmarketos.org/issues")
        return True


def bootimg(args, path):
    if not os.path.exists(path):
        raise RuntimeError("Could not find file '" + path + "'")

    logging.info("NOTE: You will be prompted for your sudo password, so we can"
                 " set up a chroot to extract and analyze your boot.img file")
    pmb.chroot.apk.install(args, ["file", "unpackbootimg"])

    temp_path = pmb.chroot.other.tempfolder(args, "/tmp/bootimg_parser")
    bootimg_path = f"{args.work}/chroot_native{temp_path}/boot.img"

    # Copy the boot.img into the chroot temporary folder
    pmb.helpers.run.root(args, ["cp", path, bootimg_path])

    file_output = pmb.chroot.user(args, ["file", "-b", "boot.img"],
                                  working_dir=temp_path,
                                  output_return=True).rstrip()
    if "android bootimg" not in file_output.lower():
        if "force" in args and args.force:
            logging.warning("WARNING: boot.img file seems to be invalid, but"
                            " proceeding anyway (-f specified)")
        else:
            logging.info("NOTE: If you are sure that your file is a valid"
                         " boot.img file, you could force the analysis"
                         " with: 'pmbootstrap bootimg_analyze " + path +
                         " -f'")
            if ("linux kernel" in file_output.lower() or
                    "ARM OpenFirmware FORTH Dictionary" in file_output):
                raise RuntimeError("File is a Kernel image, you might need the"
                                   " 'heimdall-isorec' flash method. See also:"
                                   " <https://wiki.postmarketos.org/wiki/"
                                   "Deviceinfo_flash_methods>")
            else:
                raise RuntimeError("File is not an Android boot.img. (" +
                                   file_output + ")")

    # Extract all the files
    pmb.chroot.user(args, ["unpackbootimg", "-i", "boot.img"],
                    working_dir=temp_path)

    output = {}
    # Get base, offsets, pagesize, cmdline and qcdt info
    with open(bootimg_path + "-base", 'r') as f:
        output["base"] = ("0x%08x" % int(f.read().replace('\n', ''), 16))
    with open(bootimg_path + "-kernel_offset", 'r') as f:
        output["kernel_offset"] = ("0x%08x"
                                   % int(f.read().replace('\n', ''), 16))
    with open(bootimg_path + "-ramdisk_offset", 'r') as f:
        output["ramdisk_offset"] = ("0x%08x"
                                    % int(f.read().replace('\n', ''), 16))
    with open(bootimg_path + "-second_offset", 'r') as f:
        output["second_offset"] = ("0x%08x"
                                   % int(f.read().replace('\n', ''), 16))
    with open(bootimg_path + "-tags_offset", 'r') as f:
        output["tags_offset"] = ("0x%08x"
                                 % int(f.read().replace('\n', ''), 16))
    with open(bootimg_path + "-pagesize", 'r') as f:
        output["pagesize"] = f.read().replace('\n', '')
    with open(bootimg_path + "-cmdline", 'r') as f:
        output["cmdline"] = f.read().replace('\n', '')
    output["qcdt"] = ("true" if os.path.isfile(f"{bootimg_path}-dt") and
                      os.path.getsize(f"{bootimg_path}-dt") > 0 else "false")
    output["mtk_mkimage"] = ("true" if has_mtk_header(f"{bootimg_path}-kernel",
                             "KERNEL") else "false")
    output["dtb_second"] = ("true" if is_dtb(f"{bootimg_path}-second")
                            else "false")

    # Mediatek: Check that the ramdisk also has a known-good label
    # We don't care about the return value, just whether it throws an exception
    # or not.
    has_mtk_header(f"{bootimg_path}-ramdisk", "ROOTFS")

    # Cleanup
    pmb.chroot.root(args, ["rm", "-r", temp_path])

    return output