create reproducible UDF image

[milahu]

afaik, there is no way to create reproducible UDF images with mkudffs or the linux udf driver, because i cannot set file times to zero

i can create a reproducible ISO image with SOURCE_DATE_EPOCH=0 xorrisofs --modification-date=1970010100000000 --set_all_file_dates set_to_mtime -uid 0 -gid 0 -volid SOME_THING --gpt_disk_guid 00000000000000000000000000000000 -preparer "" -path-list files.txt where files.txt is sorted with LC_ALL=C sort

expected

• set file times to zero = 1970-01-01 00:00:00 +0000
• set uid to zero
• set gid to zero
• set uuid to zero
• set preparer to empty string

actual

find pycdlib/ -name "*.py" | xargs grep -HnF -e 'time.time()' -e uuid -e random

pycdlib/udf.py:22:import random
pycdlib/udf.py:566:        self.desc_creation_time.new(time.time())
pycdlib/udf.py:1528:        # random value, all ASCII encoded.
pycdlib/udf.py:1529:        unique = format(int(time.time()), '08x') + format(random.getrandbits(26), '08x')
pycdlib/udf.py:1542:        self.recording_date.new(time.time())
pycdlib/udf.py:3477:        self.recording_date.new(time.time())
pycdlib/udf.py:3649:        self.recording_date.new(time.time())
pycdlib/udf.py:4045:        self.access_time.new(time.time())
pycdlib/udf.py:4048:        self.mod_time.new(time.time())
pycdlib/udf.py:4051:        self.attr_time.new(time.time())
pycdlib/udf.py:5323:        self.timestamp.new(time.time())
pycdlib/udf.py:5505:        self.access_time.new(time.time())
pycdlib/udf.py:5508:        self.mod_time.new(time.time())
pycdlib/udf.py:5511:        self.attr_time.new(time.time())
pycdlib/headervd.py:308:        self.root_dir_record.new_root(self, seqnum, self.log_block_size, time.time())
pycdlib/headervd.py:327:        now = time.time()
pycdlib/headervd.py:424:        vol_mod_date.new(time.time())
pycdlib/pycdlib.py:1081:                # Some ISOs use random extent locations for zero-length files.
pycdlib/pycdlib.py:1083:                # other files, as the linkage will be essentially random.
pycdlib/pycdlib.py:1818:                    False, False, self.xa, 0o040555, time.time())
pycdlib/pycdlib.py:2262:                                    b'', False, 0, time.time())
pycdlib/pycdlib.py:3137:                             time.time())
pycdlib/pycdlib.py:3449:                    False, -1, time.time())
pycdlib/pycdlib.py:3718:                    vd.logical_block_size(), xa, file_mode, time.time())
pycdlib/pycdlib.py:3739:                          time.time())
pycdlib/pycdlib.py:4767:                                     self.xa, file_mode, time.time())
pycdlib/pycdlib.py:4798:                        self.xa, file_mode, time.time())
pycdlib/pycdlib.py:5347:                                rr_symlink_name_bytes, self.xa, time.time())
pycdlib/pycdlib.py:5413:                                self.xa, -1, time.time())
pycdlib/pycdlib.py:5579:         mbr_id - The mbr_id to use.  If set to None (the default), a random one
pycdlib/isohybrid.py:21:import random
pycdlib/isohybrid.py:24:import uuid
pycdlib/isohybrid.py:263:        self.part_guid = uuid.UUID(bytes=part_guid)
pycdlib/isohybrid.py:289:        self.part_guid = uuid.uuid4()
pycdlib/isohybrid.py:359:        self.disk_guid = uuid.UUID(bytes=disk_guid)
pycdlib/isohybrid.py:385:        self.disk_guid = uuid.uuid4()
pycdlib/isohybrid.py:815:            self.mbr_id = random.getrandbits(32)

workaround

# create reproducible UDF image
# set all times to zero
import time
def zero_time():
    return 0.0
time.time = zero_time
# set all uuid's to zero
import uuid
real_uuid = uuid.UUID
def zero_uuid():
    return real_uuid(hex="00000000000000000000000000000000")
uuid.UUID = zero_uuid
real_uuid4 = uuid.uuid4
def zero_uuid4():
    return real_uuid4(hex="00000000000000000000000000000000")
uuid.uuid4 = zero_uuid4
# set random bits to zero
import random
def zero_getrandbits(k):
    return 0
random.getrandbits = zero_getrandbits
import pycdlib

this will create reproducible image files

but this will set wrong times per TZ=UTC 7z l test.iso and TZ=UTC stat mnt/test.txt, times are off by 56 minutes = 3360 seconds

+ 1970-01-01 00:00:00
- 1970-01-01 00:56:00

see also

• https://reproducible-builds.org/docs/archives/
• https://reproducible-builds.org/docs/system-images/