Remove support for shadow(5)'s sp_min

[alejandro-colomar]

Password expiry was deprecated in 4.19.

sp_min (password minimum age) doesn't seem to be regulated, so it seems we can remove it already.

Link: #1432

---

Revisions:

v1b

• Rebase

$ git rd 
1:  d23f4fd515f2 = 1:  cedee3d5c4fb src/chage.c: Remove interactive -m
2:  df14c804a6a7 = 2:  aa27a3c7d6f5 */: chage(1): -m,--mindays: Remove option
3:  66cf7e9ab2ec = 3:  99023e27937c */: passwd(1): -n,--mindays: Remove option
4:  dacb4880dd83 ! 4:  ba480ec8b60e */: login.defs(5): PASS_MIN_DAYS: Remove configuration variable
    @@ man/login.defs.5.xml
            HOME_MODE
     -      PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
     +      PASS_MAX_DAYS PASS_WARN_AGE
    -       <phrase condition="sha_crypt">SHA_CRYPT_MAX_ROUNDS
    -       SHA_CRYPT_MIN_ROUNDS</phrase>
    +       SHA_CRYPT_MAX_ROUNDS SHA_CRYPT_MIN_ROUNDS
            SUB_GID_COUNT SUB_GID_MAX SUB_GID_MIN
    +       SUB_UID_COUNT SUB_UID_MAX SUB_UID_MIN
     @@
        <term>pwck</term>
        <listitem>
5:  c8f041d71528 = 5:  61639063c123 */: shadow(5): sp_min: Ignore field, and clear it

[patrakov]

The use case for the minimum password age is to prevent lazy people in environments where periodic password changes are required, knowing that they can't reuse 10 last passwords, from changing the password 10 times to throwaway values and then back to the original. In practice, even though it is not explicitly regulated, auditors view it as a part of enforcement of the password history requirement.

[alejandro-colomar]

The use case for the minimum password age is to prevent lazy people,

That's actually not lazy people, but intelligent people that know ways of enforcing security even under regulations that actively try them to decrease security.

knowing that they can't reuse 10 last passwords, from changing the password 10 times to throwaway values and then back to the original. In practice, even though it is not explicitly regulated, auditors view it as a part of enforcement of the password history requirement.

Auditors can come here and talk with us. :)