scripts/dl_github_archive.py: rename from download.py

 - Make the code more GitHub-specific
 - Requires mirror hash to work with .gitattributes
 - Use different API depending on whether PKG_SOURCE_VERSION is a
   complete commit id or other ref types like tags
 - Fix removing symbolic link
 - pre-clean dir_untar for possible leftovers from previous run

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

1 files changed, 426 insertions, 0 deletions

diff --git a/scripts/dl_github_archive.py b/scripts/dl_github_archive.py
new file mode 100755
index 0000000000..5a5a016e37
--- /dev/null
+++ b/scripts/dl_github_archive.py
@@ -0,0 +1,426 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2018 Yousong Zhou <yszhou4tech@gmail.com>
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+
+import argparse
+import calendar
+import datetime
+import errno
+import fcntl
+import hashlib
+import json
+import os
+import os.path
+import re
+import shutil
+import ssl
+import subprocess
+import sys
+import time
+import urllib2
+
+TMPDIR = os.environ.get('TMP_DIR') or '/tmp'
+TMPDIR_DL = os.path.join(TMPDIR, 'dl')
+
+
+class PathException(Exception): pass
+class DownloadGitHubError(Exception): pass
+
+
+class Path(object):
+    """Context class for preparing and cleaning up directories.
+
+    If ```preclean` is ``False``, ``path`` will NOT be removed on context enter
+
+    If ``path`` ``isdir``, then it will be created on context enter.
+
+    If ``keep`` is True, then ``path`` will NOT be removed on context exit
+    """
+
+    def __init__(self, path, isdir=True, preclean=False, keep=False):
+        self.path = path
+        self.isdir = isdir
+        self.preclean = preclean
+        self.keep = keep
+
+    def __enter__(self):
+        if self.preclean:
+            self.rm_all(self.path)
+        if self.isdir:
+            self.mkdir_all(self.path)
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        if not self.keep:
+            self.rm_all(self.path)
+
+    @staticmethod
+    def mkdir_all(path):
+        """Same as mkdir -p."""
+        names = os.path.split(path)
+        p = ''
+        for name in names:
+            p = os.path.join(p, name)
+            Path._mkdir(p)
+
+    @staticmethod
+    def _rmdir_dir(dir_):
+        names = Path._listdir(dir_)
+        for name in names:
+            p = os.path.join(dir_, name)
+            Path.rm_all(p)
+        Path._rmdir(dir_)
+
+    @staticmethod
+    def _mkdir(path):
+        Path._os_func(os.mkdir, path, errno.EEXIST)
+
+    @staticmethod
+    def _rmdir(path):
+        Path._os_func(os.rmdir, path, errno.ENOENT)
+
+    @staticmethod
+    def _remove(path):
+        Path._os_func(os.remove, path, errno.ENOENT)
+
+    @staticmethod
+    def _listdir(path):
+        return Path._os_func(os.listdir, path, errno.ENOENT, default=[])
+
+    @staticmethod
+    def _os_func(func, path, errno, default=None):
+        """Call func(path) in an idempotent way.
+
+        On exception ``ex``, if the type is OSError and ``ex.errno == errno``,
+        return ``default``, otherwise, re-raise
+        """
+        try:
+            return func(path)
+        except OSError as e:
+            if e.errno == errno:
+                return default
+            else:
+                raise
+
+    @staticmethod
+    def rm_all(path):
+        """Same as rm -r."""
+        if os.path.islink(path):
+            Path._remove(path)
+        elif os.path.isdir(path):
+            Path._rmdir_dir(path)
+        else:
+            Path._remove(path)
+
+    @staticmethod
+    def untar(path, into=None):
+        """Extract tarball at ``path`` into subdir ``into``.
+
+        return subdir name if and only if there exists one, otherwise raise PathException
+        """
+        args = ('tar', '-C', into, '-xzf', path, '--no-same-permissions')
+        subprocess.check_call(args, preexec_fn=lambda: os.umask(0o22))
+        dirs = os.listdir(into)
+        if len(dirs) == 1:
+            return dirs[0]
+        else:
+            raise PathException('untar %s: expecting a single subdir, got %s' % (path, dirs))
+
+    @staticmethod
+    def tar(path, subdir, into=None, ts=None):
+        """Pack ``path`` into tarball ``into``."""
+        # --sort=name requires a recent build of GNU tar
+        args = ['tar', '--numeric-owner', '--owner=0', '--group=0', '--sort=name']
+        args += ['-C', path, '-cf', into, subdir]
+        envs = os.environ.copy()
+        if ts is not None:
+            args.append('--mtime=@%d' % ts)
+        if into.endswith('.xz'):
+            envs['XZ_OPT'] = '-7e'
+            args.append('-J')
+        elif into.endswith('.bz2'):
+            args.append('-j')
+        elif into.endswith('.gz'):
+            args.append('-z')
+            envs['GZIP'] = '-n'
+        else:
+            raise PathException('unknown compression type %s' % into)
+        subprocess.check_call(args, env=envs)
+
+
+class GitHubCommitTsCache(object):
+    __cachef = 'github.commit.ts.cache'
+    __cachen = 2048
+
+    def __init__(self):
+        Path.mkdir_all(TMPDIR_DL)
+        self.cachef = os.path.join(TMPDIR_DL, self.__cachef)
+        self.cache = {}
+
+    def get(self, k):
+        """Get timestamp with key ``k``."""
+        fileno = os.open(self.cachef, os.O_RDONLY | os.O_CREAT)
+        with os.fdopen(fileno) as fin:
+            try:
+                fcntl.lockf(fileno, fcntl.LOCK_SH)
+                self._cache_init(fin)
+                if k in self.cache:
+                    ts = self.cache[k][0]
+                    return ts
+            finally:
+                fcntl.lockf(fileno, fcntl.LOCK_UN)
+        return None
+
+    def set(self, k, v):
+        """Update timestamp with ``k``."""
+        fileno = os.open(self.cachef, os.O_RDWR | os.O_CREAT)
+        with os.fdopen(fileno, 'wb+') as f:
+            try:
+                fcntl.lockf(fileno, fcntl.LOCK_EX)
+                self._cache_init(f)
+                self.cache[k] = (v, int(time.time()))
+                self._cache_flush(f)
+            finally:
+                fcntl.lockf(fileno, fcntl.LOCK_UN)
+
+    def _cache_init(self, fin):
+        for line in fin:
+            k, ts, updated = line.split()
+            ts = int(ts)
+            updated = int(updated)
+            self.cache[k] = (ts, updated)
+
+    def _cache_flush(self, fout):
+        cache = sorted(self.cache.iteritems(), cmp=lambda a, b: b[1][1] - a[1][1])
+        cache = cache[:self.__cachen]
+        self.cache = {}
+        os.ftruncate(fout.fileno(), 0)
+        fout.seek(0, os.SEEK_SET)
+        for k, ent in cache:
+            ts = ent[0]
+            updated = ent[1]
+            line = '{0} {1} {2}\n'.format(k, ts, updated)
+            fout.write(line)
+
+
+class DownloadGitHubTarball(object):
+    """Download and repack archive tarabll from GitHub.
+
+    Compared with the method of packing after cloning the whole repo, this
+    method is more friendly to users with fragile internet connection.
+
+    However, there are limitations with this method
+
+     - GitHub imposes a 60 reqs/hour limit for unauthenticated API access.
+       This affects fetching commit date for reproducible tarballs.  Download
+       through the archive link is not affected.
+
+     - GitHub archives do not contain source codes for submodules.
+
+     - GitHub archives seem to respect .gitattributes and ignore pathes with
+       export-ignore attributes.
+
+    For the first two issues, the method will fail loudly to allow fallback to
+    clone-then-pack method.
+
+    As for the 3rd issue, to make sure that this method only produces identical
+    tarballs as the fallback method, we require the expected hash value to be
+    supplied.  That means the first tarball will need to be prepared by the
+    clone-then-pack method
+    """
+
+    __repo_url_regex = re.compile(r'^(?:https|git)://github.com/(?P<owner>[^/]+)/(?P<repo>[^/]+)')
+
+    def __init__(self, args):
+        self.dl_dir = args.dl_dir
+        self.version = args.version
+        self.subdir = args.subdir
+        self.source = args.source
+        self.url = args.url
+        self._init_owner_repo()
+        self.xhash = args.hash
+        self._init_hasher()
+        self.commit_ts = None           # lazy load commit timestamp
+        self.commit_ts_cache = GitHubCommitTsCache()
+        self.name = 'github-tarball'
+
+    def download(self):
+        """Download and repack GitHub archive tarball."""
+        self._init_commit_ts()
+        with Path(TMPDIR_DL, keep=True) as dir_dl:
+            # fetch tarball from GitHub
+            tarball_path = os.path.join(dir_dl.path, self.subdir + '.tar.gz.dl')
+            with Path(tarball_path, isdir=False):
+                self._fetch(tarball_path)
+                # unpack
+                d = os.path.join(dir_dl.path, self.subdir + '.untar')
+                with Path(d, preclean=True) as dir_untar:
+                    tarball_prefix = Path.untar(tarball_path, into=dir_untar.path)
+                    dir0 = os.path.join(dir_untar.path, tarball_prefix)
+                    dir1 = os.path.join(dir_untar.path, self.subdir)
+                    # submodules check
+                    if self._has_submodule(dir0):
+                        raise self._error('Fetching submodules is not yet supported')
+                    # rename subdir
+                    os.rename(dir0, dir1)
+                    # repack
+                    into=os.path.join(TMPDIR_DL, self.source)
+                    Path.tar(dir_untar.path, self.subdir, into=into, ts=self.commit_ts)
+                    try:
+                        self._hash_check(into)
+                    except Exception:
+                        Path.rm_all(into)
+                        raise
+                    # move to target location
+                    file1 = os.path.join(self.dl_dir, self.source)
+                    if into != file1:
+                        shutil.move(into, file1)
+
+    def _has_submodule(self, dir_):
+        m = os.path.join(dir_, '.gitmodules')
+        try:
+            st = os.stat(m)
+            return st.st_size > 0
+        except OSError as e:
+            return e.errno != errno.ENOENT
+
+    def _init_owner_repo(self):
+        m = self.__repo_url_regex.search(self.url)
+        if m is None:
+            raise self._error('Invalid github url: {}'.format(self.url))
+        owner = m.group('owner')
+        repo = m.group('repo')
+        if repo.endswith('.git'):
+            repo = repo[:-4]
+        self.owner = owner
+        self.repo = repo
+
+    def _init_hasher(self):
+        xhash = self.xhash
+        if len(xhash) == 64:
+            self.hasher = hashlib.sha256()
+        elif len(xhash) == 32:
+            self.hasher = hashlib.md5()
+        else:
+            raise self._error('Requires sha256sum for verification')
+        self.xhash = xhash
+
+    def _hash_check(self, f):
+        with open(f, 'rb') as fin:
+            while True:
+                d = fin.read(4096)
+                if not d:
+                    break
+                self.hasher.update(d)
+        xhash = self.hasher.hexdigest()
+        if xhash != self.xhash:
+            raise self._error('Wrong hash (probably caused by .gitattributes), expecting {}, got {}'.format(self.xhash, xhash))
+
+    def _init_commit_ts(self):
+        if self.commit_ts is not None:
+            return
+        # GitHub provides 2 APIs[1,2] for fetching commit data.  API[1] is more
+        # terse while API[2] provides more verbose info such as commit diff
+        # etc.  That's the main reason why API[1] is preferred: the response
+        # size is predictable.
+        #
+        # However, API[1] only accepts complete commit sha1sum as the parameter
+        # while API[2] is more liberal accepting also partial commit id and
+        # tags, etc.
+        #
+        # [1] Get a single commit, Repositories, https://developer.github.com/v3/repos/commits/#get-a-single-commit
+        # [2] Git Commits, Git Data, https://developer.github.com/v3/git/commits/#get-a-commit
+        apis = [
+            {
+                'url': self._make_repo_url_path('git', 'commits', self.version),
+                'attr_path': ('committer', 'date'),
+            }, {
+                'url': self._make_repo_url_path('commits', self.version),
+                'attr_path': ('commit', 'committer', 'date'),
+            },
+        ]
+        version_is_sha1sum = len(self.version) == 40
+        if not version_is_sha1sum:
+            apis.insert(0, apis.pop())
+        for api in apis:
+            url = api['url']
+            attr_path = api['attr_path']
+            try:
+                ct = self.commit_ts_cache.get(url)
+                if ct is not None:
+                    self.commit_ts = ct
+                    return
+                ct = self._init_commit_ts_remote_get(url, attr_path)
+                self.commit_ts = ct
+                self.commit_ts_cache.set(url, ct)
+                return
+            except Exception:
+                pass
+        raise self._error('Cannot fetch commit ts: {}'.format(url))
+
+    def _init_commit_ts_remote_get(self, url, attrpath):
+        resp = self._make_request(url)
+        data = resp.read()
+        date = json.loads(data)
+        for attr in attrpath:
+            date = date[attr]
+        date = datetime.datetime.strptime(date, '%Y-%m-%dT%H:%M:%SZ')
+        date = date.timetuple()
+        ct = calendar.timegm(date)
+        return ct
+
+    def _fetch(self, path):
+        """Fetch tarball of the specified version ref."""
+        ref = self.version
+        url = self._make_repo_url_path('tarball', ref)
+        resp = self._make_request(url)
+        with open(path, 'wb') as fout:
+            while True:
+                d = resp.read(4096)
+                if not d:
+                    break
+                fout.write(d)
+
+    def _make_repo_url_path(self, *args):
+        url = '/repos/{0}/{1}'.format(self.owner, self.repo)
+        if args:
+            url += '/' + '/'.join(args)
+        return url
+
+    def _make_request(self, path):
+        """Request GitHub API endpoint on ``path``."""
+        url = 'https://api.github.com' + path
+        headers = {
+            'Accept': 'application/vnd.github.v3+json',
+            'User-Agent': 'OpenWrt',
+        }
+        req = urllib2.Request(url, headers=headers)
+        sslcontext = ssl._create_unverified_context()
+        fileobj = urllib2.urlopen(req, context=sslcontext)
+        return fileobj
+
+    def _error(self, msg):
+        return DownloadGitHubError('{}: {}'.format(self.source, msg))
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--dl-dir', default=os.getcwd(), help='Download dir')
+    parser.add_argument('--url', help='Download URL')
+    parser.add_argument('--subdir', help='Source code subdir name')
+    parser.add_argument('--version', help='Source code version')
+    parser.add_argument('--source', help='Source tarball filename')
+    parser.add_argument('--hash', help='Source tarball\'s expected sha256sum')
+    args = parser.parse_args()
+    method = DownloadGitHubTarball(args)
+    try:
+        method.download()
+    except Exception:
+        sys.stderr.write('download {} from {} failed\n'.format(args.source, args.url))
+        raise
+
+if __name__ == '__main__':
+    main()