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✏️ Editing: cc_seed_random.py

# Copyright (C) 2013 Yahoo! Inc.
# Copyright (C) 2014 Canonical, Ltd
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
# Author: Dustin Kirkland <kirkland@ubuntu.com>
# Author: Scott Moser <scott.moser@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
"""Seed Random: Provide random seed data"""

import base64
import logging
import os
from io import BytesIO
from textwrap import dedent

from cloudinit import subp, util
from cloudinit.cloud import Cloud
from cloudinit.config import Config
from cloudinit.config.schema import MetaSchema, get_meta_doc
from cloudinit.distros import ALL_DISTROS
from cloudinit.settings import PER_INSTANCE

LOG = logging.getLogger(__name__)

MODULE_DESCRIPTION = """\
All cloud instances started from the same image will produce very similar
data when they are first booted as they are all starting with the same seed
for the kernel's entropy keyring. To avoid this, random seed data can be
provided to the instance either as a string or by specifying a command to run
to generate the data.

Configuration for this module is under the ``random_seed`` config key. If
the cloud provides its own random seed data, it will be appended to ``data``
before it is written to ``file``.

If the ``command`` key is specified, the given command will be executed.  This
will happen after ``file`` has been populated.  That command's environment will
contain the value of the ``file`` key as ``RANDOM_SEED_FILE``. If a command is
specified that cannot be run, no error will be reported unless
``command_required`` is set to true.
"""

meta: MetaSchema = {
    "id": "cc_seed_random",
    "name": "Seed Random",
    "title": "Provide random seed data",
    "description": MODULE_DESCRIPTION,
    "distros": [ALL_DISTROS],
    "frequency": PER_INSTANCE,
    "examples": [
        dedent(
            """\
            random_seed:
              file: /dev/urandom
              data: my random string
              encoding: raw
              command: ['sh', '-c', 'dd if=/dev/urandom of=$RANDOM_SEED_FILE']
              command_required: true
            """
        ),
        dedent(
            """\
            # To use 'pollinate' to gather data from a remote entropy
            # server and write it to '/dev/urandom', the following
            # could be used:
            random_seed:
              file: /dev/urandom
              command: ["pollinate", "--server=http://local.polinate.server"]
              command_required: true
            """
        ),
    ],
    "activate_by_schema_keys": [],
}

__doc__ = get_meta_doc(meta)

def _decode(data, encoding=None):
    if not data:
        return b""
    if not encoding or encoding.lower() in ["raw"]:
        return util.encode_text(data)
    elif encoding.lower() in ["base64", "b64"]:
        return base64.b64decode(data)
    elif encoding.lower() in ["gzip", "gz"]:
        return util.decomp_gzip(data, quiet=False, decode=None)
    else:
        raise IOError("Unknown random_seed encoding: %s" % (encoding))

def handle_random_seed_command(command, required, env=None):
    if not command and required:
        raise ValueError("no command found but required=true")
    elif not command:
        LOG.debug("no command provided")
        return

cmd = command[0]
    if not subp.which(cmd):
        if required:
            raise ValueError(
                "command '{cmd}' not found but required=true".format(cmd=cmd)
            )
        else:
            LOG.debug("command '%s' not found for seed_command", cmd)
            return
    subp.subp(command, env=env, capture=False)

def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None:
    mycfg = cfg.get("random_seed", {})
    seed_path = mycfg.get("file", "/dev/urandom")
    seed_data = mycfg.get("data", b"")

seed_buf = BytesIO()
    if seed_data:
        seed_buf.write(_decode(seed_data, encoding=mycfg.get("encoding")))

# 'random_seed' is set up by Azure datasource, and comes already in
    # openstack meta_data.json
    metadata = cloud.datasource.metadata
    if metadata and "random_seed" in metadata:
        seed_buf.write(util.encode_text(metadata["random_seed"]))

seed_data = seed_buf.getvalue()
    if len(seed_data):
        LOG.debug(
            "%s: adding %s bytes of random seed entropy to %s",
            name,
            len(seed_data),
            seed_path,
        )
        util.append_file(seed_path, seed_data)

command = mycfg.get("command", None)
    req = mycfg.get("command_required", False)
    try:
        env = os.environ.copy()
        env["RANDOM_SEED_FILE"] = seed_path
        handle_random_seed_command(command=command, required=req, env=env)
    except ValueError as e:
        LOG.warning("handling random command [%s] failed: %s", command, e)
        raise e

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