PrintLastLog fails on systems without lastlog but with utmpx

[Ed Maste]

On Wed, 18 May 2022 at 14:13, Ed Maste <emaste at freebsd.org> wrote:
>
> From FreeBSD PR 209441. configure sets DISABLE_LASTLOG if we do not
> have lastlog.ll_line:
>
> AC_CHECK_MEMBER([struct lastlog.ll_line], [], [
>     if test x$SKIP_DISABLE_LASTLOG_DEFINE != "xyes" ; then
>         AC_DEFINE([DISABLE_LASTLOG])
>     fi
>         ], [
>
> However DISABLE_LASTLOG disables support for PrintLastLog altogether
> -- from servconf.c:
>
> #ifdef DISABLE_LASTLOG
>         { "printlastlog", sUnsupported, SSHCFG_GLOBAL },
> #else
>         { "printlastlog", sPrintLastLog, SSHCFG_GLOBAL },
> #endif
>
> In getlast_entry() DISABLE_LASTLOG disables use of wtmp and wtmpx, but
> not utmpx. DISABLE_LASTLOG seems to be intended to mean disable last
> login functionality altogether, and disable use of specifically
> utmp/lastlog, in different locations.

This is still the case -- DISABLE_LASTLOG can be set if we do not want
lastlog functionality, but it is automatically set by configure if we
don't have lastlog.ll_line:

AC_CHECK_MEMBER([struct lastlog.ll_line], [], [
    if test x$SKIP_DISABLE_LASTLOG_DEFINE != "xyes" ; then
        AC_DEFINE([DISABLE_LASTLOG])
    fi

elsewhere we explicitly do not set DISABLE_LASTLOG if a lastlog file
cannot be found, with a comment that wtmp/wtmpx would not be tested:

                if test -z "$conf_lastlog_location"; then
                        AC_MSG_WARN([** Cannot find lastlog **])
                        dnl Don't define DISABLE_LASTLOG - that means
we don't try wtmp/wtmpx
                fi

and there's a special case SCO OpenServer 5.x:

        SKIP_DISABLE_LASTLOG_DEFINE=yes

to avoid the lastlog.ll_line test.

As a workaround to fix this for FreeBSD I just added SKIP_DISABLE_LASTLOG_DEFINE
https://cgit.freebsd.org/src/commit/?id=170511589e4d15a27ee92979691cfc1b26929bb7
but this needs a proper fix, presumably by splitting DISABLE_LASTLOG in two.