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Filename : __init__.py
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# Copyright (C) 2012 Canonical Ltd.
# Copyright (C) 2012, 2013 Hewlett-Packard Development Company, L.P.
# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Juerg Haefliger <juerg.haefliger@hp.com>
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import abc
import logging
import os

from cloudinit import importer, type_utils, util
from cloudinit.settings import FREQUENCIES, PER_ALWAYS, PER_INSTANCE

LOG = logging.getLogger(__name__)

# Used as the content type when a message is not multipart
# and it doesn't contain its own content-type
NOT_MULTIPART_TYPE = "text/x-not-multipart"

# When none is assigned this gets used
OCTET_TYPE = "application/octet-stream"

# Special content types that signal the start and end of processing
CONTENT_END = "__end__"
CONTENT_START = "__begin__"
CONTENT_SIGNALS = [CONTENT_START, CONTENT_END]

# Used when a part-handler type is encountered
# to allow for registration of new types.
PART_CONTENT_TYPES = ["text/part-handler"]
PART_HANDLER_FN_TMPL = "part-handler-%03d"

# For parts without filenames
PART_FN_TPL = "part-%03d"

# Different file beginnings to their content type
INCLUSION_TYPES_MAP = {
    "#include": "text/x-include-url",
    "#include-once": "text/x-include-once-url",
    "#!": "text/x-shellscript",
    "#cloud-config": "text/cloud-config",
    "#part-handler": "text/part-handler",
    "#cloud-boothook": "text/cloud-boothook",
    "#cloud-config-archive": "text/cloud-config-archive",
    "#cloud-config-jsonp": "text/cloud-config-jsonp",
    "## template: jinja": "text/jinja2",
    # Note: for the next 3 entries, the prefix doesn't matter because these
    # are for types that can only be used as part of a MIME message. However,
    # including these entries suppresses warnings during `cloudinit devel
    # make-mime`, which otherwise would require `--force`.
    "text/x-shellscript-per-boot": "text/x-shellscript-per-boot",
    "text/x-shellscript-per-instance": "text/x-shellscript-per-instance",
    "text/x-shellscript-per-once": "text/x-shellscript-per-once",
}

# Sorted longest first
INCLUSION_SRCH = sorted(
    list(INCLUSION_TYPES_MAP.keys()), key=(lambda e: 0 - len(e))
)


class Handler(metaclass=abc.ABCMeta):
    def __init__(self, frequency, version=2):
        self.handler_version = version
        self.frequency = frequency

    def __repr__(self):
        return "%s: [%s]" % (type_utils.obj_name(self), self.list_types())

    def list_types(self):
        # Each subclass must define the supported content prefixes it handles.
        if not hasattr(self, "prefixes"):
            raise NotImplementedError("Missing prefixes subclass attribute")
        else:
            return [
                INCLUSION_TYPES_MAP[prefix]
                for prefix in getattr(self, "prefixes")
            ]

    @abc.abstractmethod
    def handle_part(self, *args, **kwargs):
        raise NotImplementedError()


def run_part(mod, data, filename, payload, frequency, headers):
    mod_freq = mod.frequency
    if not (
        mod_freq == PER_ALWAYS
        or (frequency == PER_INSTANCE and mod_freq == PER_INSTANCE)
    ):
        return
    # Sanity checks on version (should be an int convertible)
    try:
        mod_ver = mod.handler_version
        mod_ver = int(mod_ver)
    except (TypeError, ValueError, AttributeError):
        mod_ver = 1
    content_type = headers["Content-Type"]
    try:
        LOG.debug(
            "Calling handler %s (%s, %s, %s) with frequency %s",
            mod,
            content_type,
            filename,
            mod_ver,
            frequency,
        )
        if mod_ver == 3:
            # Treat as v. 3 which does get a frequency + headers
            mod.handle_part(
                data, content_type, filename, payload, frequency, headers
            )
        elif mod_ver == 2:
            # Treat as v. 2 which does get a frequency
            mod.handle_part(data, content_type, filename, payload, frequency)
        elif mod_ver == 1:
            # Treat as v. 1 which gets no frequency
            mod.handle_part(data, content_type, filename, payload)
        else:
            raise ValueError("Unknown module version %s" % (mod_ver))
    except Exception:
        util.logexc(
            LOG,
            "Failed calling handler %s (%s, %s, %s) with frequency %s",
            mod,
            content_type,
            filename,
            mod_ver,
            frequency,
        )


def call_begin(mod, data, frequency):
    # Create a fake header set
    headers = {
        "Content-Type": CONTENT_START,
    }
    run_part(mod, data, None, None, frequency, headers)


def call_end(mod, data, frequency):
    # Create a fake header set
    headers = {
        "Content-Type": CONTENT_END,
    }
    run_part(mod, data, None, None, frequency, headers)


def walker_handle_handler(pdata, _ctype, _filename, payload):
    curcount = pdata["handlercount"]
    modname = PART_HANDLER_FN_TMPL % (curcount)
    frequency = pdata["frequency"]
    modfname = os.path.join(pdata["handlerdir"], "%s" % (modname))
    if not modfname.endswith(".py"):
        modfname = "%s.py" % (modfname)
    # TODO(harlowja): Check if path exists??
    util.write_file(modfname, payload, 0o600)
    handlers = pdata["handlers"]
    try:
        mod = fixup_handler(importer.import_module(modname))
        call_begin(mod, pdata["data"], frequency)
        # Only register and increment after the above have worked, so we don't
        # register if it fails starting.
        handlers.register(mod, initialized=True)
        pdata["handlercount"] = curcount + 1
    except Exception:
        util.logexc(
            LOG,
            "Failed at registering python file: %s (part handler %s)",
            modfname,
            curcount,
        )


def _extract_first_or_bytes(blob, size):
    # Extract the first line or upto X symbols for text objects
    # Extract first X bytes for binary objects
    try:
        if isinstance(blob, str):
            start = blob.split("\n", 1)[0]
        else:
            # We want to avoid decoding the whole blob (it might be huge)
            # By taking 4*size bytes we guarantee to decode size utf8 chars
            start = blob[: 4 * size].decode(errors="ignore").split("\n", 1)[0]
        if len(start) >= size:
            start = start[:size]
    except UnicodeDecodeError:
        # Bytes array doesn't contain text so return chunk of raw bytes
        start = blob[0:size]
    return start


def _escape_string(text):
    try:
        return text.encode("string_escape")
    except (LookupError, TypeError):
        try:
            # Unicode (and Python 3's str) doesn't support string_escape...
            return text.encode("unicode_escape")
        except TypeError:
            # Give up...
            pass
    except AttributeError:
        # We're in Python3 and received blob as text
        # No escaping is needed because bytes are printed
        # as 'b\xAA\xBB' automatically in Python3
        pass
    return text


def walker_callback(data, filename, payload, headers):
    content_type = headers["Content-Type"]
    if content_type in data.get("excluded"):
        LOG.debug('content_type "%s" is excluded', content_type)
        return

    if content_type in PART_CONTENT_TYPES:
        walker_handle_handler(data, content_type, filename, payload)
        return
    handlers = data["handlers"]
    if content_type in handlers:
        run_part(
            handlers[content_type],
            data["data"],
            filename,
            payload,
            data["frequency"],
            headers,
        )
    elif payload:
        # Extract the first line or 24 bytes for displaying in the log
        start = _extract_first_or_bytes(payload, 24)
        details = "'%s...'" % (_escape_string(start))
        if content_type == NOT_MULTIPART_TYPE:
            LOG.warning(
                "Unhandled non-multipart (%s) userdata: %s",
                content_type,
                details,
            )
        else:
            LOG.warning(
                "Unhandled unknown content-type (%s) userdata: %s",
                content_type,
                details,
            )
    else:
        LOG.debug("Empty payload of type %s", content_type)


# Callback is a function that will be called with
# (data, content_type, filename, payload)
def walk(msg, callback, data):
    partnum = 0
    for part in msg.walk():
        # multipart/* are just containers
        if part.get_content_maintype() == "multipart":
            continue

        ctype = part.get_content_type()
        if ctype is None:
            ctype = OCTET_TYPE

        filename = part.get_filename()
        if not filename:
            filename = PART_FN_TPL % (partnum)

        headers = dict(part)
        LOG.debug(headers)
        headers["Content-Type"] = ctype
        payload = util.fully_decoded_payload(part)
        callback(data, filename, payload, headers)
        partnum = partnum + 1


def fixup_handler(mod, def_freq=PER_INSTANCE):
    if not hasattr(mod, "handler_version"):
        setattr(mod, "handler_version", 1)
    if not hasattr(mod, "frequency"):
        setattr(mod, "frequency", def_freq)
    else:
        freq = mod.frequency
        if freq and freq not in FREQUENCIES:
            LOG.warning("Handler %s has an unknown frequency %s", mod, freq)
    return mod


def type_from_starts_with(payload, default=None):
    try:
        payload_lc = util.decode_binary(payload).lower()
    except UnicodeDecodeError:
        return default
    payload_lc = payload_lc.lstrip()
    for text in INCLUSION_SRCH:
        if payload_lc.startswith(text):
            return INCLUSION_TYPES_MAP[text]
    return default