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tytso / e2fsprogs

Ext2/3/4 file system utilities
http://ext4.wiki.kernel.org
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RFE: Support SOURCE_DATE_EPOCH and timestamp clamping #131

Closed nl6720 closed 6 months ago

nl6720 commented 1 year ago

e1f7100643a46456be107b33098f6034b0835e6d added support for a e2fsprogs-specific variable E2FSPROGS_FAKE_TIME. But as the commit message says, you still need to manually set a reproducible hash seed.

It would be useful if e2fsprogs could support SOURCE_DATE_EPOCH. I.e. if SOURCE_DATE_EPOCH is set, use it as the mkfs timestamp and generate a reproducible hash seed from it.

Additionally, mkfs.ext4 -d reproducibility requires timestamp clamping. The various timestamps of files in the file system should not be newer than SOURCE_DATE_EPOCH.

tytso commented 7 months ago

The hash seed is not actually time based (it's a random value), so it seems at odds with the definition of SOURCE_DATE_EPOCH to say that we should change how the hash seed is generated. I understand why this would be considered "convenient", but it still seems strange.

katexochen commented 7 months ago

so it seems at odds with the definition of SOURCE_DATE_EPOCH to say that we should change how the hash seed is generated

I agree, using time as seed only in this case would be somewhat unexpected.

But I would really love to see SOURCE_DATE_EPOCH respected, and support for timestamp clamping seems to be a great idea, too.

tytso commented 6 months ago

SOURCE_DATE_EPOCH has been implementing with timestamp clamping in v1.47.1-rc1+