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Diffstat (limited to '')
| -rw-r--r-- | python/mozbuild/mozpack/archive.py | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/python/mozbuild/mozpack/archive.py b/python/mozbuild/mozpack/archive.py new file mode 100644 index 0000000000..89bf14b179 --- /dev/null +++ b/python/mozbuild/mozpack/archive.py @@ -0,0 +1,153 @@ +# This Source Code Form is subject to the terms of the Mozilla Public +# License, v. 2.0. If a copy of the MPL was not distributed with this +# file, You can obtain one at http://mozilla.org/MPL/2.0/. + +import bz2 +import gzip +import stat +import tarfile + +from .files import BaseFile, File + +# 2016-01-01T00:00:00+0000 +DEFAULT_MTIME = 1451606400 + + +# Python 3.9 contains this change: +# https://github.com/python/cpython/commit/674935b8caf33e47c78f1b8e197b1b77a04992d2 +# which changes the output of tar creation compared to earlier versions. +# As this code is used to generate tar files that are meant to be deterministic +# across versions of python (specifically, it's used as part of computing the hash +# of docker images, which needs to be identical between CI (which uses python 3.8), +# and developer environments (using arbitrary versions of python, at this point, +# most probably more recent than 3.9)). +# What we do is subblass TarInfo so that if used on python >= 3.9, it reproduces the +# behavior from python < 3.9. +# Here's how it goes: +# - the behavior in python >= 3.9 is the same as python < 3.9 when the type encoded +# in the tarinfo is CHRTYPE or BLKTYPE. +# - the value of the type is only compared in the context of choosing which behavior +# to take +# - we replace the type with the same value (so that using the value has no changes) +# but that pretends to be the same as CHRTYPE so that the condition that enables the +# old behavior is taken. +class HackedType(bytes): + def __eq__(self, other): + if other == tarfile.CHRTYPE: + return True + return self == other + + +class TarInfo(tarfile.TarInfo): + @staticmethod + def _create_header(info, format, encoding, errors): + info["type"] = HackedType(info["type"]) + return tarfile.TarInfo._create_header(info, format, encoding, errors) + + +def create_tar_from_files(fp, files): + """Create a tar file deterministically. + + Receives a dict mapping names of files in the archive to local filesystem + paths or ``mozpack.files.BaseFile`` instances. + + The files will be archived and written to the passed file handle opened + for writing. + + Only regular files can be written. + + FUTURE accept a filename argument (or create APIs to write files) + """ + # The format is explicitly set to tarfile.GNU_FORMAT, because this default format + # has been changed in Python 3.8. + with tarfile.open( + name="", mode="w", fileobj=fp, dereference=True, format=tarfile.GNU_FORMAT + ) as tf: + for archive_path, f in sorted(files.items()): + if not isinstance(f, BaseFile): + f = File(f) + + ti = TarInfo(archive_path) + ti.mode = f.mode or 0o0644 + ti.type = tarfile.REGTYPE + + if not ti.isreg(): + raise ValueError("not a regular file: %s" % f) + + # Disallow setuid and setgid bits. This is an arbitrary restriction. + # However, since we set uid/gid to root:root, setuid and setgid + # would be a glaring security hole if the archive were + # uncompressed as root. + if ti.mode & (stat.S_ISUID | stat.S_ISGID): + raise ValueError("cannot add file with setuid or setgid set: " "%s" % f) + + # Set uid, gid, username, and group as deterministic values. + ti.uid = 0 + ti.gid = 0 + ti.uname = "" + ti.gname = "" + + # Set mtime to a constant value. + ti.mtime = DEFAULT_MTIME + + ti.size = f.size() + # tarfile wants to pass a size argument to read(). So just + # wrap/buffer in a proper file object interface. + tf.addfile(ti, f.open()) + + +def create_tar_gz_from_files(fp, files, filename=None, compresslevel=9): + """Create a tar.gz file deterministically from files. + + This is a glorified wrapper around ``create_tar_from_files`` that + adds gzip compression. + + The passed file handle should be opened for writing in binary mode. + When the function returns, all data has been written to the handle. + """ + # Offset 3-7 in the gzip header contains an mtime. Pin it to a known + # value so output is deterministic. + gf = gzip.GzipFile( + filename=filename or "", + mode="wb", + fileobj=fp, + compresslevel=compresslevel, + mtime=DEFAULT_MTIME, + ) + with gf: + create_tar_from_files(gf, files) + + +class _BZ2Proxy(object): + """File object that proxies writes to a bz2 compressor.""" + + def __init__(self, fp, compresslevel=9): + self.fp = fp + self.compressor = bz2.BZ2Compressor(compresslevel) + self.pos = 0 + + def tell(self): + return self.pos + + def write(self, data): + data = self.compressor.compress(data) + self.pos += len(data) + self.fp.write(data) + + def close(self): + data = self.compressor.flush() + self.pos += len(data) + self.fp.write(data) + + +def create_tar_bz2_from_files(fp, files, compresslevel=9): + """Create a tar.bz2 file deterministically from files. + + This is a glorified wrapper around ``create_tar_from_files`` that + adds bzip2 compression. + + This function is similar to ``create_tar_gzip_from_files()``. + """ + proxy = _BZ2Proxy(fp, compresslevel=compresslevel) + create_tar_from_files(proxy, files) + proxy.close() |