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#!/usr/bin/python3
#
#    Query and display EC2 metadata related to the AMI instance
#    Copyright (c) 2009 Canonical Ltd. (Canonical Contributor Agreement 2.5)
#
#    Author: Alon Swartz <alon@turnkeylinux.org>
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.

import sys
import time
import getopt
import socket
import os
try:
    from urllib import request as urllib_request
    from urllib import error as urllib_error
    from urllib import parse as urllib_parse
except ImportError:
    # python2
    import urllib2 as urllib_request
    import urllib2 as urllib_error
    import urlparse as urllib_parse


instdata_host = "169.254.169.254"
instdata_ver = "2009-04-04"
instdata_url = "http://%s/%s" % (instdata_host, instdata_ver)

TOKEN_TTL_SECONDS = 21600
TOKEN_HEADER = "X-aws-ec2-metadata-token"
TOKEN_HEADER_TTL = "X-aws-ec2-metadata-token-ttl-seconds"

session_token_url = "http://%s/%s/%s" % (instdata_host, 'latest', 'api/token')

__doc__ = """
Query and display EC2 metadata.

If no options are provided, all options will be displayed

Options:
    -h --help               show this help

    --kernel-id             display the kernel id
    --ramdisk-id            display the ramdisk id
    --reservation-id        display the reservation id

    --ami-id                display the ami id
    --ami-launch-index      display the ami launch index
    --ami-manifest-path     display the ami manifest path
    --ancestor-ami-ids      display the ami ancestor id
    --product-codes         display the ami associated product codes
    --availability-zone     display the ami placement zone name
    --availability-zone-id  display the ami placement zone id
    --region                display the ami placement region name
    --group-name            display the ami placement group name
    --host-id               display the dedicated host id
    --partition-number      display the partition instance was launched from

    --instance-id           display the instance id
    --instance-type         display the instance type

    --local-hostname        display the local hostname
    --public-hostname       display the public hostname

    --local-ipv4            display the local ipv4 ip address
    --public-ipv4           display the public ipv4 ip address

    --block-device-mapping  display the block device id
    --security-groups       display the security groups

    --mac                   display the instance mac address
    --profile               display the instance profile
    --instance-action       display the instance-action

    --public-keys           display the openssh public keys
    --user-data             display the user data (not actually metadata)

    -u | --url URL          use URL (default: %s)

""" % instdata_url


METAOPTS = ['ami-id', 'ami-launch-index', 'ami-manifest-path',
            'ancestor-ami-ids', 'availability-zone', 'block-device-mapping',
            'instance-action', 'instance-id', 'instance-type',
            'local-hostname', 'local-ipv4', 'kernel-id', 'mac',
            'profile', 'product-codes', 'public-hostname', 'public-ipv4',
            'public-keys', 'ramdisk-id', 'reservation-id', 'security-groups',
            'user-data', 'availability-zone-id', 'region', 'host-id',
            'group-name', 'partition-number']

binstdout = os.fdopen(sys.stdout.fileno(), 'wb')


def print_binary(data):
    if not isinstance(data, bytes):
        data = data.encode()
    binstdout.write(data)
    binstdout.flush()


class Error(Exception):
    pass


class EC2Metadata:  # pylint: disable=R0903
    """Class for querying metadata from EC2"""

    def __init__(self, burl=instdata_url):
        self.burl = burl

        s = urllib_parse.urlsplit(burl)
        addr = s.netloc.split(":")[0]
        port = s.port
        if s.port is None:
            port = 80
        if not self._test_connectivity(addr, port):
            raise Error("could not establish connection to: %s:%s" %
                        (addr, port))
        self._imdsv2_ensure_token()

    @staticmethod
    def _test_connectivity(addr, port):
        for _ in range(6):
            s = socket.socket()
            try:
                s.connect((addr, port))
                s.close()
                return True
            except socket.error:
                time.sleep(1)

        return False

    def _imdsv2_ensure_token(self):
        # Get IMDSv2 session token
        request = urllib_request.Request(
            session_token_url,
            method='PUT',
            headers={TOKEN_HEADER_TTL: TOKEN_TTL_SECONDS})
        resp = urllib_request.urlopen(request)
        self.session_token = resp.read()

    def _get(self, uri, decode=True):
        url = "%s/%s" % (self.burl, uri)
        try:
            resp = urllib_request.urlopen(
                urllib_request.Request(
                    url,
                    headers={TOKEN_HEADER: self.session_token}))
            value = resp.read()
            if decode:
                value = value.decode()
        except urllib_error.HTTPError as e:
            if e.code == 404:
                return None
            # Eucalyptus may raise a 500 (Internal Server Error)
            if e.code == 500:
                return None
            raise

        return value

    def get(self, metaopt):
        """return value of metaopt"""

        if metaopt not in METAOPTS:
            raise Error('unknown metaopt', metaopt, METAOPTS)

        if metaopt in [
                'availability-zone',
                'availability-zone-id',
                'region',
                'host-id',
                'group-name',
                'partition-number',
                ]:
            return self._get('meta-data/placement/' + metaopt)

        if metaopt == 'public-keys':
            data = self._get('meta-data/public-keys')
            if data is None:
                return None

            keyids = [line.split('=')[0] for line in data.splitlines()]

            public_keys = []
            for keyid in keyids:
                uri = 'meta-data/public-keys/%d/openssh-key' % int(keyid)
                public_keys.append(self._get(uri).rstrip())

            return public_keys

        if metaopt == 'user-data':
            return self._get('user-data', decode=False)

        return self._get('meta-data/' + metaopt)


def get(metaopt):
    """primitive: return value of metaopt"""

    m = EC2Metadata()
    return m.get(metaopt)


def display(metaopts, burl, prefix=False):
    """primitive: display metaopts (list) values with optional prefix"""

    m = EC2Metadata(burl)
    for metaopt in metaopts:
        value = m.get(metaopt)
        if not value:
            value = "unavailable"

        if prefix:
            print("%s: %s" % (metaopt, value))
        elif metaopt == "user-data":
            # We want to avoid binary blob corruption while printing as string
            print_binary(value)
        else:
            print(value)


def usage(s=None):
    """display usage and exit"""

    msg = ""
    if s:
        msg = "Error: %s\n" % s
    msg += "Syntax: %s [options]\n" % sys.argv[0]
    msg += __doc__
    sys.stderr.write(msg + "\n")
    sys.exit(1)


def main():
    """handle cli options"""

    try:
        getopt_metaopts = METAOPTS[:]
        getopt_metaopts.append('help')
        getopt_metaopts.append('url=')
        opts, _ = getopt.gnu_getopt(sys.argv[1:], "hu:", getopt_metaopts)
    except getopt.GetoptError as e:
        usage(e)

    burl = instdata_url

    metaopts = []
    prefix = False
    for opt, val in opts:
        if opt in ('-h', '--help'):
            usage()
        if opt in ('-u', '--url'):
            burl = val
            continue

        metaopts.append(opt.replace('--', ''))

    if len(metaopts) == 0:
        prefix = True
        metaopts = METAOPTS

    display(metaopts, burl, prefix)


if __name__ == "__main__":
    main()

# vi: ts=4 expandtab