[Pkg-shadow-devel] Bug#1100632: debian-policy: document subuids

[Chris Hofstaedtler]

Package: debian-policy
X-Debbugs-CC: pkg-shadow-devel at lists.alioth.debian.org, base-passwd at packages.debian.org

Dear Policy Editors,

passwd/shadow has long ago introduced the concept of "subuids". 
Please see subuid(5), or https://manpages.debian.org/bookworm/passwd/subuid.5.en.html

These are used by unshare and other container managers. They are 
*automatically* assigned by useradd, when creating non-system users.

Debian's src:shadow uses the same uid-range as upstream:

SUB_UID_MIN        100000
SUB_UID_MAX     600100000

These ranges are in the range currently documented in policy 9.2.2 
as:

| 65536-4294967293:
| Dynamically allocated user accounts. By default adduser will not 
| allocate UIDs and GIDs in this range, to ease compatibility with 
| legacy systems where uid_t is still 16 bits.

Given this concept exists since at least jessie, I think it should 
finally be documented in policy, too.

I'm not sure about a text. Maybe:

diff --git i/policy/ch-opersys.rst w/policy/ch-opersys.rst
index 1501076..37b4674 100644
--- i/policy/ch-opersys.rst
+++ w/policy/ch-opersys.rst
@@ -292,11 +292,16 @@ The UID and GID numbers are divided into classes as follows:
      This value *must not* be used, because it was the error return
      sentinel value when ``uid_t`` was 16 bits.

-65536-4294967293:
+65536-99999, 600100000-4294967293:
      Dynamically allocated user accounts. By default ``adduser`` will not
      allocate UIDs and GIDs in this range, to ease compatibility with
      legacy systems where ``uid_t`` is still 16 bits.

+100000-600100000:
+    Dynamically allocated subordinate user ids. See subuid(5).
+    ``useradd`` (and thus ``adduser``) automatically allocate these
+    when non-system users are created.
+
  4294967294:
      ``(uid_t)(-2) == (gid_t)(-2)`` *must not* be used, because it is
      used as the anonymous, unauthenticated user by some NFS


Thanks,
Chris