nix/doc/manual/rl-next/leading-period.md
Robert Hensing 6e3548f866 Disallow store path names that are . or .. (plus opt. -)
As discussed in the maintainer meeting on 2024-01-29.

Mainly this is to avoid a situation where the name is parsed and
treated as a file name, mostly to protect users.
.-* and ..-* are also considered invalid because they might strip
on that separator to remove versions. Doesn't really work, but that's
what we decided, and I won't argue with it, because .-* probably
doesn't seem to have a real world application anyway.
We do still permit a 1-character name that's just "-", which still
poses a similar risk in such a situation. We can't start disallowing
trailing -, because a non-zero number of users will need it and we've
seen how annoying and painful such a change is.

What matters most is preventing a situation where . or .. can be
injected, and to just get this done.
2024-03-26 13:47:41 +01:00

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---
synopsis: Store paths are allowed to start with `.`
issues: 912
prs: 9867 9091 9095 9120 9121 9122 9130 9219 9224
---
Leading periods were allowed by accident in Nix 2.4. The Nix team has considered this to be a bug, but this behavior has since been relied on by users, leading to unnecessary difficulties.
From now on, leading periods are officially, definitively supported. The names `.` and `..` are disallowed, as well as those starting with `.-` or `..-`.
Nix versions that denied leading periods are documented [in the issue](https://github.com/NixOS/nix/issues/912#issuecomment-1919583286).