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Filename : dmi.py
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# This file is part of cloud-init. See LICENSE file for license information.
import os
import re
from collections import namedtuple
from typing import Optional

from cloudinit import log as logging
from cloudinit import subp
from cloudinit.util import is_container, is_FreeBSD

LOG = logging.getLogger(__name__)

# Path for DMI Data
DMI_SYS_PATH = "/sys/class/dmi/id"

KernelNames = namedtuple("KernelNames", ["linux", "freebsd"])
KernelNames.__new__.__defaults__ = (None, None)

# FreeBSD's kenv(1) and Linux /sys/class/dmi/id/* both use different names from
# dmidecode. The values are the same, and ultimately what we're interested in.
# These tools offer a "cheaper" way to access those values over dmidecode.
# This is our canonical translation table. If we add more tools on other
# platforms to find dmidecode's values, their keys need to be put in here.
DMIDECODE_TO_KERNEL = {
    "baseboard-asset-tag": KernelNames("board_asset_tag", "smbios.planar.tag"),
    "baseboard-manufacturer": KernelNames(
        "board_vendor", "smbios.planar.maker"
    ),
    "baseboard-product-name": KernelNames(
        "board_name", "smbios.planar.product"
    ),
    "baseboard-serial-number": KernelNames(
        "board_serial", "smbios.planar.serial"
    ),
    "baseboard-version": KernelNames("board_version", "smbios.planar.version"),
    "bios-release-date": KernelNames("bios_date", "smbios.bios.reldate"),
    "bios-vendor": KernelNames("bios_vendor", "smbios.bios.vendor"),
    "bios-version": KernelNames("bios_version", "smbios.bios.version"),
    "chassis-asset-tag": KernelNames(
        "chassis_asset_tag", "smbios.chassis.tag"
    ),
    "chassis-manufacturer": KernelNames(
        "chassis_vendor", "smbios.chassis.maker"
    ),
    "chassis-serial-number": KernelNames(
        "chassis_serial", "smbios.chassis.serial"
    ),
    "chassis-version": KernelNames(
        "chassis_version", "smbios.chassis.version"
    ),
    "system-manufacturer": KernelNames("sys_vendor", "smbios.system.maker"),
    "system-product-name": KernelNames(
        "product_name", "smbios.system.product"
    ),
    "system-serial-number": KernelNames(
        "product_serial", "smbios.system.serial"
    ),
    "system-uuid": KernelNames("product_uuid", "smbios.system.uuid"),
    "system-version": KernelNames("product_version", "smbios.system.version"),
}


def _read_dmi_syspath(key: str) -> Optional[str]:
    """
    Reads dmi data from /sys/class/dmi/id
    """
    kmap = DMIDECODE_TO_KERNEL.get(key)
    if kmap is None or kmap.linux is None:
        return None
    dmi_key_path = "{0}/{1}".format(DMI_SYS_PATH, kmap.linux)
    LOG.debug("querying dmi data %s", dmi_key_path)
    if not os.path.exists(dmi_key_path):
        LOG.debug("did not find %s", dmi_key_path)
        return None

    try:
        with open(dmi_key_path, "rb") as fp:
            key_data = fp.read()
    except PermissionError:
        LOG.debug("Could not read %s", dmi_key_path)
        return None

    # uninitialized dmi values show as all \xff and /sys appends a '\n'.
    # in that event, return empty string.
    if key_data == b"\xff" * (len(key_data) - 1) + b"\n":
        key_data = b""

    try:
        return key_data.decode("utf8").strip()
    except UnicodeDecodeError as e:
        LOG.error(
            "utf-8 decode of content (%s) in %s failed: %s",
            dmi_key_path,
            key_data,
            e,
        )

    return None


def _read_kenv(key: str) -> Optional[str]:
    """
    Reads dmi data from FreeBSD's kenv(1)
    """
    kmap = DMIDECODE_TO_KERNEL.get(key)
    if kmap is None or kmap.freebsd is None:
        return None

    LOG.debug("querying dmi data %s", kmap.freebsd)

    try:
        cmd = ["kenv", "-q", kmap.freebsd]
        (result, _err) = subp.subp(cmd)
        result = result.strip()
        LOG.debug("kenv returned '%s' for '%s'", result, kmap.freebsd)
        return result
    except subp.ProcessExecutionError as e:
        LOG.debug("failed kenv cmd: %s\n%s", cmd, e)

    return None


def _call_dmidecode(key: str, dmidecode_path: str) -> Optional[str]:
    """
    Calls out to dmidecode to get the data out. This is mostly for supporting
    OS's without /sys/class/dmi/id support.
    """
    try:
        cmd = [dmidecode_path, "--string", key]
        (result, _err) = subp.subp(cmd)
        result = result.strip()
        LOG.debug("dmidecode returned '%s' for '%s'", result, key)
        if result.replace(".", "") == "":
            return ""
        return result
    except subp.ProcessExecutionError as e:
        LOG.debug("failed dmidecode cmd: %s\n%s", cmd, e)
        return None


def read_dmi_data(key: str) -> Optional[str]:
    """
    Wrapper for reading DMI data.

    If running in a container return None.  This is because DMI data is
    assumed to be not useful in a container as it does not represent the
    container but rather the host.

    This will do the following (returning the first that produces a
    result):
        1) Use a mapping to translate `key` from dmidecode naming to
           sysfs naming and look in /sys/class/dmi/... for a value.
        2) Use `key` as a sysfs key directly and look in /sys/class/dmi/...
        3) Fall-back to passing `key` to `dmidecode --string`.

    If all of the above fail to find a value, None will be returned.
    """

    if is_container():
        return None

    if is_FreeBSD():
        return _read_kenv(key)

    syspath_value = _read_dmi_syspath(key)
    if syspath_value is not None:
        return syspath_value

    def is_x86(arch):
        return arch == "x86_64" or (arch[0] == "i" and arch[2:] == "86")

    # running dmidecode can be problematic on some arches (LP: #1243287)
    uname_arch = os.uname()[4]
    if not (is_x86(uname_arch) or uname_arch in ("aarch64", "amd64")):
        LOG.debug("dmidata is not supported on %s", uname_arch)
        return None

    dmidecode_path = subp.which("dmidecode")
    if dmidecode_path:
        return _call_dmidecode(key, dmidecode_path)

    LOG.debug("did not find either path %s or dmidecode command", DMI_SYS_PATH)
    return None


def sub_dmi_vars(src: str) -> str:
    """Replace __dmi.VARNAME__ with DMI values from either sysfs or kenv."""
    if "__" not in src:
        return src
    valid_dmi_keys = DMIDECODE_TO_KERNEL.keys()
    for match in re.findall(r"__dmi\.([^_]+)__", src):
        if match not in valid_dmi_keys:
            LOG.warning(
                "Ignoring invalid __dmi.%s__ in %s. Expected one of: %s.",
                match,
                src,
                valid_dmi_keys,
            )
            continue
        dmi_value = read_dmi_data(match)
        if not dmi_value:
            dmi_value = ""
        LOG.debug(
            "Replacing __dmi.%s__ in '%s' with '%s'.",
            match,
            src,
            dmi_value,
        )
        src = src.replace(f"__dmi.{match}__", dmi_value)
    return src


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