This is important for parallel image builds to ensure all pre-seeded snaps have the same versions across image variants.sil2100/core18-pi3-arm64
Tobias Koch
6 years ago
parent
a06d208871
commit
654fcae467
@ -0,0 +1,397 @@
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#!/usr/bin/python3
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#-*- encoding: utf-8 -*-
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"""
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This script can be used instead of the traditional `snap` command to download
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snaps and accompanying assertions. It uses the new store API (v2) which allows
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creating temporary snapshots of the channel map.
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To create such a snapshot run
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snap-tool cohort-create
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This will print a "cohort-key" to stdout, which can then be passed to future
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invocations of `snap-tool download`. Whenever a cohort key is provided, the
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store will provide a view of the channel map as it existed when the key was
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created.
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"""
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from textwrap import dedent
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import argparse
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import base64
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import binascii
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import getopt
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import hashlib
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import json
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import os
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import shutil
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import subprocess
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import sys
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import urllib.error
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import urllib.request
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EXIT_OK = 0
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EXIT_ERR = 1
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class SnapError(Exception):
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"""Generic error thrown by the Snap class."""
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pass
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class SnapCraftError(SnapError):
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"""Error thrown on problems with the snapcraft APIs."""
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pass
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class SnapAssertionError(SnapError):
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"""Error thrown on problems with the assertions API."""
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pass
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class Snap:
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"""This class provides methods to retrieve information about a snap and
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download it together with its assertions."""
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def __init__(self, name, channel="stable", arch="amd64", series=16,
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cohort_key=None, assertion_url="https://assertions.ubuntu.com",
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snapcraft_url="https://api.snapcraft.io", **kwargs):
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"""
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:param name:
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The name of the snap.
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:param channel:
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The channel to operate on.
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:param arch:
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The Debian architecture of the snap (e.g. amd64, armhf, arm64, ...).
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:param series:
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The device series. This should always be 16.
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:param cohort_key:
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A cohort key to access a snapshot of the channel map.
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"""
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self._name = name
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self._channel = channel
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self._arch = arch
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self._series = series
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self._cohort_key = cohort_key
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self._assertion_url = assertion_url
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self._snapcraft_url = snapcraft_url
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self._details = None
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self._assertions = {}
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@classmethod
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def cohort_create(cls):
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"""Get a cohort key for the current moment. A cohort key is valid
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across all snaps, channels and architectures."""
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return Snap("core")\
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.get_details(cohort_create=True)\
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.get("cohort-key")
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def download(self, download_assertions=True):
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"""Download the snap container. If download_assertions is True, the
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corresponding assertions will be downloaded, as well."""
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snap = self.get_details()
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snap_name = snap["name"]
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snap_revision = snap["revision"]
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publisher_id = snap["publisher"]["id"]
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snap_download_url = snap["download"]["url"]
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snap_byte_size = snap["download"]["size"]
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filename = snap_name + "_" + str(snap_revision)
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snap_filename = filename + ".snap"
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assert_filename = filename + ".assert"
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skip_snap_download = False
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if os.path.exists(snap_filename) and os.path.getsize(snap_filename) \
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== snap_byte_size:
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skip_snap_download = True
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headers = {}
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if os.environ.get("SNAPPY_STORE_NO_CDN", "0") != "0":
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headers.update({
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"X-Ubuntu-No-Cdn": "true",
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"Snap-CDN": "none",
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})
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request = urllib.request.Request(snap_download_url, headers=headers)
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if not skip_snap_download:
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with urllib.request.urlopen(request) as response, \
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open(snap_filename, "wb+") as fp:
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shutil.copyfileobj(response, fp)
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if not download_assertions:
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return
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required_assertions = [
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"account-key",
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"account",
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"snap-declaration",
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"snap-revision",
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]
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if publisher_id == "canonical":
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required_assertions.remove("account")
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for assertion_name in required_assertions:
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attr_name = "get_assertion_" + assertion_name.replace("-", "_")
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# This will populate self._assertions[<assertion_name>].
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getattr(self, attr_name)()
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with open(assert_filename, "w+", encoding="utf-8") as fp:
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fp.write("\n".join(self._assertions[a] for a in
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required_assertions))
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def get_details(self, cohort_create=False):
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"""Get details about the snap. On subsequent calls, the cached results
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are returned. If cohort_create is set to True, a cohort key will be
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created and included in the result."""
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if self._details and not cohort_create:
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return self._details
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path = "/v2/snaps/refresh"
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data = {
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"context": [],
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"actions": [
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{
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"action": "download",
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"instance-key": "0",
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"name": self._name,
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}
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]
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}
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# These are mutually exclusive.
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if cohort_create:
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data["actions"][0]["cohort-create"] = True
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elif self._cohort_key:
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data["actions"][0]["cohort-key"] = self._cohort_key
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request_json = json.dumps(data, ensure_ascii=False).encode("utf-8")
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try:
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response_dict = self._do_snapcraft_request(path, data=request_json)
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except SnapCraftError as e:
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raise SnapError("failed to get details for '{}': {}"
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.format(self._name, str(e)))
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snap_data = response_dict["results"][0]
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# Copy the key into the snap details.
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if "cohort-key" in snap_data:
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snap_data["snap"]["cohort-key"] = snap_data["cohort-key"]
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if "error" in snap_data:
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raise SnapError(
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"failed to get details for '{}' in '{}' on '{}': {}"
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.format(self._name, self._channel, self._arch,
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snap_data["error"]["message"])
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)
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self._details = snap_data["snap"]
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return self._details
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def get_assertion_snap_revision(self):
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"""Download the snap-revision assertion associated with this snap. The
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assertion is returned as a string."""
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if "snap-revision" in self._assertions:
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return self._assertions["snap-revision"]
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snap = self.get_details()
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snap_sha3_384 = base64.urlsafe_b64encode(
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binascii.a2b_hex(snap["download"]["sha3-384"])
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).decode("us-ascii")
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data = self._do_assertion_request("/v1/assertions/snap-revision/{}"
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.format(snap_sha3_384))
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self._assertions["snap-revision"] = data
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return data
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def get_assertion_snap_declaration(self):
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"""Download the snap-declaration assertion associated with this snap.
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The assertion is returned as a string."""
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if "snap-declaration" in self._assertions:
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return self._assertions["snap-declaration"]
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snap = self.get_details()
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series = self._series
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snap_id = snap["snap-id"]
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data = self._do_assertion_request(
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"/v1/assertions/snap-declaration/{}/{}"
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.format(series, snap_id))
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self._assertions["snap-declaration"] = data
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return data
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def get_assertion_account(self):
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"""Download the account assertion associated with this snap. The
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assertion is returned as a string."""
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if "account" in self._assertions:
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return self._assertions["account"]
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snap = self.get_details()
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publisher_id = snap["publisher"]["id"]
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data = self._do_assertion_request("/v1/assertions/account/{}"
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.format(publisher_id))
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self._assertions["account"] = data
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return data
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def get_assertion_account_key(self):
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"""Download the account-key assertion associated with this snap. The
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assertion will be returned as a string."""
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if "account-key" in self._assertions:
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return self._assertions["account-key"]
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declaration_data = self.get_assertion_snap_declaration()
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sign_key_sha3 = None
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for line in declaration_data.splitlines():
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if line.startswith("sign-key-sha3-384:"):
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sign_key_sha3 = line.split(":")[1].strip()
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data = self._do_assertion_request("/v1/assertions/account-key/{}"
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.format(sign_key_sha3))
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self._assertions["account-key"] = data
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return data
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def _do_assertion_request(self, path):
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url = self._assertion_url + path
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headers = {
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"Accept": "application/x.ubuntu.assertion",
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}
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request = urllib.request.Request(url, headers=headers)
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try:
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with urllib.request.urlopen(request) as response:
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body = response.read()
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except urllib.error.HTTPError as e:
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raise SnapAssertionError(str(e))
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return body.decode("utf-8")
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def _do_snapcraft_request(self, path, data=None):
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url = self._snapcraft_url + "/" + path
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headers = {
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"Snap-Device-Series": str(self._series),
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"Snap-Device-Architecture": self._arch,
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"Content-Type": "application/json",
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}
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request = urllib.request.Request(url, data=data, headers=headers)
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try:
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with urllib.request.urlopen(request) as response:
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body = response.read()
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except urllib.error.HTTPError as e:
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raise SnapCraftError(str(e))
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try:
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response_data = json.loads(body, encoding="utf-8")
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except json.JSONDecodeError as e:
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raise SnapCraftError("failed to decode response body: " + str(e))
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return response_data
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class SnapCli:
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def __call__(self, args):
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"""Parse the command line arguments and execute the selected command."""
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options = self._parse_opts(args)
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try:
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options.func(getattr(options, "snap", None), **vars(options))
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except SnapError as e:
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sys.stderr.write("snap-tool {}: {}\n".format(
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options.command, str(e)))
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return EXIT_ERR
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return EXIT_OK
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@staticmethod
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def _get_host_deb_arch():
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result = subprocess.run(["dpkg", "--print-architecture"],
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stdout=subprocess.PIPE, stderr=subprocess.PIPE,
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universal_newlines=True, check=True)
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return result.stdout.strip()
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def _parse_opts(self, args):
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main_parser = argparse.ArgumentParser()
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subparsers = main_parser.add_subparsers(dest="command")
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parser_cohort_create = subparsers.add_parser("cohort-create",
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help="Create a cohort key for the snap store channel map.")
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parser_cohort_create.set_defaults(func=self._cohort_create)
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parser_download = subparsers.add_parser("download",
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help="Download a snap from the store.")
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parser_download.set_defaults(func=self._download)
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parser_info = subparsers.add_parser("info",
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help="Retrieve information about a snap.")
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parser_info.set_defaults(func=self._info)
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# Add common parameters.
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for parser in [parser_download, parser_info]:
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parser.add_argument("--cohort-key", dest="cohort_key",
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help="A cohort key to pin the channel map to.", type=str)
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parser.add_argument("--channel", dest="channel",
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help="The publication channel to query (default: stable).",
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type=str, default="stable")
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parser.add_argument("--series", dest="series",
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help="The device series (default: 16)",
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type=int, default=16)
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parser.add_argument("--arch", dest="arch",
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help="The Debian architecture (default: amd64).",
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type=str, default=self._get_host_deb_arch())
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parser.add_argument("snap", help="The name of the snap.")
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if not args:
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main_parser.print_help()
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sys.exit(EXIT_ERR)
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return main_parser.parse_args(args)
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def _cohort_create(self, _, **kwargs):
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print(Snap.cohort_create())
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def _download(self, snap_name, **kwargs):
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Snap(snap_name, **kwargs).download()
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def _info(self, snap_name, **kwargs):
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snap = Snap(snap_name, **kwargs)
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info = snap.get_details()
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print(dedent("""\
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name: {}
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summary: {}
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arch: {}
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channel: {}
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publisher: {}
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license: {}
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snap-id: {}
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revision: {}"""
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.format(
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snap_name,
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info.get("summary", ""),
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snap._arch,
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snap._channel,
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info.get("publisher", {}).get("display-name", ""),
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info.get("license", ""),
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info.get("snap-id", ""),
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info.get("revision", "")
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))
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)
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if __name__ == "__main__":
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try:
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SnapCli()(sys.argv[1:])
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except KeyboardInterrupt:
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sys.stderr.write("snap-tool: caught keyboard interrupt, exiting.\n")
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sys.exit(EXIT_ERR)
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