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✏️ Editing: ec2.py

# Copyright (C) 2012 Yahoo! Inc.
# Copyright (C) 2014 Amazon.com, Inc. or its affiliates.
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
# Author: Andrew Jorgensen <ajorgens@amazon.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import functools
import json
import logging

from cloudinit import url_helper, util

LOG = logging.getLogger(__name__)
SKIP_USERDATA_CODES = frozenset([url_helper.NOT_FOUND])

class MetadataLeafDecoder:
    """Decodes a leaf blob into something meaningful."""

def _maybe_json_object(self, text):
        if not text:
            return False
        text = text.strip()
        if text.startswith("{") and text.endswith("}"):
            return True
        return False

def __call__(self, field, blob):
        if not blob:
            return ""
        try:
            blob = util.decode_binary(blob)
        except UnicodeDecodeError:
            return blob
        if self._maybe_json_object(blob):
            try:
                # Assume it's json, unless it fails parsing...
                return json.loads(blob)
            except (ValueError, TypeError) as e:
                LOG.warning(
                    "Field %s looked like a json object, but it was not: %s",
                    field,
                    e,
                )
        if blob.find("\n") != -1:
            return blob.splitlines()
        return blob

# See: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/
#         ec2-instance-metadata.html
class MetadataMaterializer:
    def __init__(self, blob, base_url, caller, leaf_decoder=None):
        self._blob = blob
        self._md = None
        self._base_url = base_url
        self._caller = caller
        if leaf_decoder is None:
            self._leaf_decoder = MetadataLeafDecoder()
        else:
            self._leaf_decoder = leaf_decoder

def _parse(self, blob):
        leaves = {}
        children = []
        blob = util.decode_binary(blob)

if not blob:
            return (leaves, children)

def has_children(item):
            if item.endswith("/"):
                return True
            else:
                return False

def get_name(item):
            if item.endswith("/"):
                return item.rstrip("/")
            return item

for field in blob.splitlines():
            field = field.strip()
            field_name = get_name(field)
            if not field or not field_name:
                continue
            # Don't materialize credentials
            if field_name == "security-credentials":
                continue
            if has_children(field):
                if field_name not in children:
                    children.append(field_name)
            else:
                contents = field.split("=", 1)
                resource = field_name
                if len(contents) > 1:
                    # What a PITA...
                    (ident, sub_contents) = contents
                    ident = util.safe_int(ident)
                    if ident is not None:
                        resource = "%s/openssh-key" % (ident)
                        field_name = sub_contents
                leaves[field_name] = resource
        return (leaves, children)

def materialize(self):
        if self._md is not None:
            return self._md
        self._md = self._materialize(self._blob, self._base_url)
        return self._md

def _materialize(self, blob, base_url):
        (leaves, children) = self._parse(blob)
        child_contents = {}
        for c in children:
            child_url = url_helper.combine_url(base_url, c)
            if not child_url.endswith("/"):
                child_url += "/"
            child_blob = self._caller(child_url)
            child_contents[c] = self._materialize(child_blob, child_url)
        leaf_contents = {}
        for (field, resource) in leaves.items():
            leaf_url = url_helper.combine_url(base_url, resource)
            leaf_blob = self._caller(leaf_url)
            leaf_contents[field] = self._leaf_decoder(field, leaf_blob)
        joined = {}
        joined.update(child_contents)
        for field in leaf_contents.keys():
            if field in joined:
                LOG.warning("Duplicate key found in results from %s", base_url)
            else:
                joined[field] = leaf_contents[field]
        return joined

def skip_retry_on_codes(status_codes, _request_args, cause):
    """Returns False if cause.code is in status_codes."""
    return cause.code not in status_codes

def get_instance_userdata(
    api_version="latest",
    metadata_address="http://169.254.169.254",
    ssl_details=None,
    timeout=5,
    retries=5,
    headers_cb=None,
    headers_redact=None,
    exception_cb=None,
):
    ud_url = url_helper.combine_url(metadata_address, api_version)
    ud_url = url_helper.combine_url(ud_url, "user-data")
    user_data = b""
    try:
        if not exception_cb:
            # It is ok for userdata to not exist (thats why we are stopping if
            # NOT_FOUND occurs) and just in that case returning an empty
            # string.
            exception_cb = functools.partial(
                skip_retry_on_codes, SKIP_USERDATA_CODES
            )
        response = url_helper.read_file_or_url(
            ud_url,
            ssl_details=ssl_details,
            timeout=timeout,
            retries=retries,
            exception_cb=exception_cb,
            headers_cb=headers_cb,
            headers_redact=headers_redact,
        )
        user_data = response.contents
    except url_helper.UrlError as e:
        if e.code not in SKIP_USERDATA_CODES:
            util.logexc(LOG, "Failed fetching userdata from url %s", ud_url)
    except Exception:
        util.logexc(LOG, "Failed fetching userdata from url %s", ud_url)
    return user_data

def _get_instance_metadata(
    tree,
    api_version="latest",
    metadata_address="http://169.254.169.254",
    ssl_details=None,
    timeout=5,
    retries=5,
    leaf_decoder=None,
    headers_cb=None,
    headers_redact=None,
    exception_cb=None,
    retrieval_exception_ignore_cb=None,
):
    md_url = url_helper.combine_url(metadata_address, api_version, tree)
    caller = functools.partial(
        url_helper.read_file_or_url,
        ssl_details=ssl_details,
        timeout=timeout,
        retries=retries,
        headers_cb=headers_cb,
        headers_redact=headers_redact,
        exception_cb=exception_cb,
    )

def mcaller(url):
        try:
            return caller(url).contents
        except url_helper.UrlError as e:
            if (
                not retrieval_exception_ignore_cb
                or not retrieval_exception_ignore_cb(e)
            ):
                raise
            else:
                LOG.warning("Skipped retrieval of the content of %s", url)
                return "(skipped)"

try:
        response = caller(md_url)
        materializer = MetadataMaterializer(
            response.contents, md_url, mcaller, leaf_decoder=leaf_decoder
        )
        md = materializer.materialize()
        if not isinstance(md, (dict)):
            md = {}
        return md
    except Exception:
        util.logexc(LOG, "Failed fetching %s from url %s", tree, md_url)
        return {}

def get_instance_metadata(
    api_version="latest",
    metadata_address="http://169.254.169.254",
    ssl_details=None,
    timeout=5,
    retries=5,
    leaf_decoder=None,
    headers_cb=None,
    headers_redact=None,
    exception_cb=None,
    retrieval_exception_ignore_cb=None,
):
    # Note, 'meta-data' explicitly has trailing /.
    # this is required for CloudStack (LP: #1356855)
    return _get_instance_metadata(
        tree="meta-data/",
        api_version=api_version,
        metadata_address=metadata_address,
        ssl_details=ssl_details,
        timeout=timeout,
        retries=retries,
        leaf_decoder=leaf_decoder,
        headers_redact=headers_redact,
        headers_cb=headers_cb,
        exception_cb=exception_cb,
        retrieval_exception_ignore_cb=retrieval_exception_ignore_cb,
    )

def get_instance_identity(
    api_version="latest",
    metadata_address="http://169.254.169.254",
    ssl_details=None,
    timeout=5,
    retries=5,
    leaf_decoder=None,
    headers_cb=None,
    headers_redact=None,
    exception_cb=None,
):
    return _get_instance_metadata(
        tree="dynamic/instance-identity",
        api_version=api_version,
        metadata_address=metadata_address,
        ssl_details=ssl_details,
        timeout=timeout,
        retries=retries,
        leaf_decoder=leaf_decoder,
        headers_redact=headers_redact,
        headers_cb=headers_cb,
        exception_cb=exception_cb,
    )

MR SKB