361 lines
13 KiB
Python
Executable File
361 lines
13 KiB
Python
Executable File
#!/usr/local/autopkg/python
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#
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# Refactoring 2018 Michal Moravec
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# Copyright 2015 Greg Neagle
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""See docstring for URLDownloader class"""
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import os.path
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import platform
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import tempfile
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from autopkglib import ProcessorError, xattr
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from autopkglib.common import BUNDLE_ID
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from autopkglib.URLGetter import URLGetter
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__all__ = ["URLDownloader"]
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class URLDownloader(URLGetter):
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"""Downloads a URL to the specified download_dir using curl."""
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description = __doc__
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input_variables = {
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"url": {"required": True, "description": "The URL to download."},
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"request_headers": {
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"required": False,
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"description": (
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"Optional dictionary of headers to include with the download request."
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),
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},
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"curl_opts": {
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"required": False,
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"description": (
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"Optional array of options to include with the download request."
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),
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},
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"download_dir": {
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"required": False,
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"description": (
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"The directory where the file will be downloaded to. Defaults "
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"to RECIPE_CACHE_DIR/downloads."
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),
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},
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"filename": {
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"required": False,
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"description": "Filename to override the URL's tail.",
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},
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"prefetch_filename": {
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"default": False,
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"required": False,
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"description": (
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"If True, URLDownloader attempts to determine filename from HTTP "
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"headers downloaded before the file itself. 'prefetch_filename' "
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"overrides 'filename' option. Filename is determined from the first "
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"available source of information in this order:\n"
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"\t1. Content-Disposition header\n"
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"\t2. Location header\n"
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"\t3. 'filename' option (if set)\n"
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"\t4. last part of 'url'. \n"
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"'prefetch_filename' is useful for URLs with redirects."
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),
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},
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"CHECK_FILESIZE_ONLY": {
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"default": False,
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"required": False,
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"description": (
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"If True, a server's ETag and Last-Modified "
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"headers will not be checked to verify whether "
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"a download is newer than a cached item, and only "
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"Content-Length (filesize) will be used. This "
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"is useful for cases where a download always "
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"redirects to different mirrors, which could "
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"cause items to be needlessly re-downloaded. "
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"Defaults to False."
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),
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},
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"PKG": {
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"required": False,
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"description": (
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"Local path to the pkg/dmg we'd otherwise download. "
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"If provided, the download is skipped and we just use "
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"this package or disk image."
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),
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},
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}
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output_variables = {
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"pathname": {"description": "Path to the downloaded file."},
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"last_modified": {
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"description": "last-modified header for the downloaded item."
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},
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"etag": {"description": "etag header for the downloaded item."},
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"download_changed": {
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"description": (
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"Boolean indicating if the download has changed since the "
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"last time it was downloaded."
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)
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},
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"url_downloader_summary_result": {
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"description": "Description of interesting results."
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},
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}
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def getxattr(self, attr):
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"""Get a named xattr from a file. Return None if not present."""
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if attr in xattr.listxattr(self.env["pathname"]):
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return xattr.getxattr(self.env["pathname"], attr).decode()
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return None
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def prepare_base_curl_cmd(self):
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"""Assemble base curl command and return it."""
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curl_cmd = [
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self.curl_binary(),
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"--silent",
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"--show-error",
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"--no-buffer",
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"--dump-header",
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"-",
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"--speed-time",
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"30",
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"--location",
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"--url",
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self.env["url"],
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]
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return curl_cmd
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def clear_zero_file(self, pathname):
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"""If file already exists and the size is 0, discard it to download again."""
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if os.path.exists(pathname) and os.path.getsize(pathname) == 0:
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os.remove(pathname)
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def prepare_download_curl_cmd(self, pathname_temporary):
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"""Assemble file download curl command and return it."""
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curl_cmd = self.prepare_base_curl_cmd()
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curl_cmd.extend(["--fail", "--output", pathname_temporary])
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# Add the common options
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self.add_curl_common_opts(curl_cmd)
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# Clear out a potentially zero-byte file
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self.clear_zero_file(self.env["pathname"])
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self.add_curl_headers(curl_cmd, self.produce_etag_headers(self.env["pathname"]))
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return curl_cmd
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def clear_vars(self):
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"""Clear and initialize variables."""
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# Delete summary result if exists
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if "url_downloader_summary_result" in self.env:
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del self.env["url_downloader_summary_result"]
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# XATTR names for Etag and Last-Modified headers
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if platform.platform().startswith("Linux"):
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self.xattr_etag = f"user.{BUNDLE_ID}.etag"
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self.xattr_last_modified = f"user.{BUNDLE_ID}.last-modified"
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else:
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self.xattr_etag = f"{BUNDLE_ID}.etag"
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self.xattr_last_modified = f"{BUNDLE_ID}.last-modified"
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self.env["last_modified"] = ""
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self.env["etag"] = ""
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self.existing_file_size = None
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def prefetch_filename(self):
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"""Attempt to find filename in HTTP headers."""
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curl_cmd = self.prepare_base_curl_cmd()
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curl_cmd.extend(["--head"])
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raw_headers = self.download_with_curl(curl_cmd)
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header = self.parse_headers(raw_headers)
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if "filename=" in header.get("content-disposition", ""):
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filename = (
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header["content-disposition"]
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.rpartition("filename=")[2]
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.replace('"', "")
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)
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self.output(
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f"Filename prefetched from the HTTP Content-Disposition header: {filename}",
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verbose_level=2,
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)
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elif header.get("http_redirected", None):
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filename = header["http_redirected"].rpartition("/")[2]
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self.output(
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f"Filename prefetched from the HTTP Location header: {filename}",
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verbose_level=2,
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)
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else:
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self.output(
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"Unable to find filename in the HTTP headers during prefetch",
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verbose_level=2,
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)
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return None
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return filename
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def get_filename(self):
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"""Obtain filename from PKG variable or URL."""
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if "PKG" in self.env:
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self.env["pathname"] = os.path.expanduser(self.env["PKG"])
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self.env["download_changed"] = True
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self.output(f"Given {self.env['pathname']}, no download needed.")
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return None
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if self.env.get("prefetch_filename", False):
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filename = self.prefetch_filename()
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if filename:
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return filename
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if "filename" in self.env:
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filename = self.env["filename"]
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else:
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# Generate filename from URL.
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filename = self.env["url"].rpartition("/")[2]
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return filename
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def get_download_dir(self):
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"""Create download dir and return its path."""
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download_dir = self.env.get("download_dir") or os.path.join(
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self.env["RECIPE_CACHE_DIR"], "downloads"
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)
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if not os.path.exists(download_dir):
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try:
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os.makedirs(download_dir)
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except OSError as err:
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raise ProcessorError(
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f"Can't create {download_dir}: {err.strerror}"
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) from err
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return download_dir
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def create_temp_file(self, download_dir):
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"""Create temporary file and return its path."""
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temporary_file = tempfile.NamedTemporaryFile(dir=download_dir, delete=False)
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pathname_temporary = temporary_file.name
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# Set permissions on the temp file as curl would set for a newly-downloaded
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# file. NamedTemporaryFile uses mkstemp(), which sets a mode of 0600, and
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# this can cause issues if this item is eventually copied to a Munki repo
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# with the same permissions and the file is inaccessible by (for example)
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# the webserver.
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os.chmod(pathname_temporary, 0o644)
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return pathname_temporary
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def download_changed(self, header):
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"""Check if downloaded file changed on server."""
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# If Content-Length header is present and we had a cached
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# file, see if it matches the size of the cached file.
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# Useful for webservers that don't provide Last-Modified
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# and ETag headers.
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if (not header.get("etag") and not header.get("last-modified")) or self.env[
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"CHECK_FILESIZE_ONLY"
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]:
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size_header = header.get("content-length")
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if size_header and int(size_header) == self.existing_file_size:
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self.env["download_changed"] = False
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self.output(
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"File size returned by webserver matches that "
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f"of the cached file: {size_header} bytes"
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)
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self.output(
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"WARNING: Matching a download by filesize is a "
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"fallback mechanism that does not guarantee "
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"that a build is unchanged."
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)
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self.output(f"Using existing {self.env['pathname']}")
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return False
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if header["http_result_code"] == "304":
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# resource not modified
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self.env["download_changed"] = False
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self.output("Item at URL is unchanged.")
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self.output(f"Using existing {self.env['pathname']}")
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return False
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return True
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def move_temp_file(self, pathname_temporary):
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"""Move temporary download file to pathname."""
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if os.path.exists(self.env["pathname"]):
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os.remove(self.env["pathname"])
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try:
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os.rename(pathname_temporary, self.env["pathname"])
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except OSError:
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raise ProcessorError(
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f"Can't move {pathname_temporary} to {self.env['pathname']}"
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) from None
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def store_headers(self, header):
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"""Store last-modified and etag headers in pathname xattr."""
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if header.get("last-modified"):
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self.env["last_modified"] = header.get("last-modified")
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xattr.setxattr(
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self.env["pathname"],
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self.xattr_last_modified,
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header.get("last-modified").encode(),
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)
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self.output(
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f"Storing new Last-Modified header: {header.get('last-modified')}"
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)
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self.env["etag"] = ""
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if header.get("etag"):
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self.env["etag"] = header.get("etag")
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xattr.setxattr(
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self.env["pathname"], self.xattr_etag, header.get("etag").encode()
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)
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self.output(f"Storing new ETag header: {header.get('etag')}")
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def main(self):
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# Clear and initiazize data structures
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self.clear_vars()
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# Ensure existence of necessary files, directories and paths
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filename = self.get_filename()
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if filename is None:
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return
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download_dir = self.get_download_dir()
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self.env["pathname"] = os.path.join(download_dir, filename)
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pathname_temporary = self.create_temp_file(download_dir)
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# Prepare curl command
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curl_cmd = self.prepare_download_curl_cmd(pathname_temporary)
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# Execute curl command and parse headers
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raw_headers = self.download_with_curl(curl_cmd)
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header = self.parse_headers(raw_headers)
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if self.download_changed(header):
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self.env["download_changed"] = True
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else:
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# Discard the temp file
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os.remove(pathname_temporary)
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return
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# New resource was downloaded. Move the temporary download file to the pathname
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self.move_temp_file(pathname_temporary)
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# Save last-modified and etag headers to files xattr
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self.store_headers(header)
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# Generate output messages and variables
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self.output(f"Downloaded {self.env['pathname']}")
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self.env["url_downloader_summary_result"] = {
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"summary_text": "The following new items were downloaded:",
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"data": {"download_path": self.env["pathname"]},
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}
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if __name__ == "__main__":
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PROCESSOR = URLDownloader()
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PROCESSOR.execute_shell()
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