Users and permissions: accounts, login, enforced file permissions, setuid, su, passwd, doas

The kernel now checks owner/group/other on open, create, unlink, rename, exec
and path search; honours set-user-id and set-group-id; restricts kill, mount,
reboot and mknod; keeps supplementary groups; and implements chown. devtmpfs
nodes carry owners and modes that chmod/chown keep. Terminals run login, the
image has root and schos, X starts as the ordinary user.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EVRhxi9zpdW2uDUN4FVcao

etc/schinit/console-shell.job

@@ -1,11 +1,11 @@
 # The interactive shell on /dev/tty1, the first virtual terminal.
 
 Label         = os.schos.console-shell
-# zsh, not /bin/sh. mksh stays as /bin/sh and is what schinit falls back to
-# when no manifest loads -- so if zsh ever fails to start, the recovery shell
-# is a different program rather than the same broken one. See ports/zsh.
-Program       = /bin/zsh
-Args          = -zsh
+# A login prompt, not a shell: /etc/schos-getty hands the terminal to login,
+# which asks who is there and starts their shell. tty6 keeps a root shell
+# with no login, for when this part of the system is what is broken.
+Program       = /bin/sh
+Args          = sh /etc/schos-getty
 RunAtLoad     = yes
 KeepAlive     = yes
 
@@ -15,8 +15,6 @@ KeepAlive     = yes
 # most: a line editor with no TERM cannot ask terminfo how to move a cursor.
 Environment = TERM=linux
 Environment = PATH=/bin:/usr/bin
-Environment = HOME=/root
-Environment = SHELL=/bin/zsh
 
 # This job reads the console, so it has to own it: schinit puts every job in
 # its own session, and a session with no controlling terminal is not delivered

etc/schinit/tty2-shell.job

@@ -6,15 +6,13 @@
 # what /dev/tty1 and /dev/tty2 being different terminals means.
 
 Label         = os.schos.tty2-shell
-Program       = /bin/zsh
-Args          = -zsh
+Program       = /bin/sh
+Args          = sh /etc/schos-getty
 RunAtLoad     = yes
 KeepAlive     = yes
 
 Environment = TERM=linux
 Environment = PATH=/bin:/usr/bin
-Environment = HOME=/root
-Environment = SHELL=/bin/zsh
 
 ControllingTerminal = yes
 

etc/schinit/tty3-shell.job

@@ -10,15 +10,13 @@
 # for six lines each is the wrong trade.
 
 Label         = os.schos.tty3-shell
-Program       = /bin/zsh
-Args          = -zsh
+Program       = /bin/sh
+Args          = sh /etc/schos-getty
 RunAtLoad     = yes
 KeepAlive     = yes
 
 Environment = TERM=linux
 Environment = PATH=/bin:/usr/bin
-Environment = HOME=/root
-Environment = SHELL=/bin/zsh
 
 ControllingTerminal = yes
 

etc/schinit/tty4-shell.job

@@ -10,15 +10,13 @@
 # for six lines each is the wrong trade.
 
 Label         = os.schos.tty4-shell
-Program       = /bin/zsh
-Args          = -zsh
+Program       = /bin/sh
+Args          = sh /etc/schos-getty
 RunAtLoad     = yes
 KeepAlive     = yes
 
 Environment = TERM=linux
 Environment = PATH=/bin:/usr/bin
-Environment = HOME=/root
-Environment = SHELL=/bin/zsh
 
 ControllingTerminal = yes
 

etc/schinit/tty5-shell.job

@@ -10,15 +10,13 @@
 # for six lines each is the wrong trade.
 
 Label         = os.schos.tty5-shell
-Program       = /bin/zsh
-Args          = -zsh
+Program       = /bin/sh
+Args          = sh /etc/schos-getty
 RunAtLoad     = yes
 KeepAlive     = yes
 
 Environment = TERM=linux
 Environment = PATH=/bin:/usr/bin
-Environment = HOME=/root
-Environment = SHELL=/bin/zsh
 
 ControllingTerminal = yes
 

etc/schinit/tty6-shell.job

@@ -1,3 +1,6 @@
+# A root shell on /dev/tty6, with no login: the way in when login itself is
+# what has broken. Every other terminal asks who is there.
+#
 # An interactive shell on /dev/tty6.
 #
 # NVT is 6 (include/dev/vt.h) and the kernel creates all six terminals, but only

etc/schos-getty

@@ -0,0 +1,10 @@
+#!/bin/sh
+# What a virtual terminal runs: take the terminal back from whoever had it, and
+# ask for a login. login hands the terminal to the user it lets in, and this
+# runs again when their shell exits.
+t=$(tty 2>/dev/null)
+if [ -n "$t" ]; then
+    chown root:tty "$t" 2>/dev/null
+    chmod 0660 "$t" 2>/dev/null
+fi
+exec /bin/login

etc/udev-schos.rules

@@ -0,0 +1,14 @@
+# SchOS's own device permissions, applied after Alpine's (the name sorts last
+# once installed as 90-schos.rules).
+#
+# The kernel makes these nodes with the permissions it means them to have
+# (kernel/fs/devfs.c). udev, with no rule that names a node, would chmod it to
+# 0600 -- which made /dev/null unusable to everyone but root -- so every kernel
+# device is named here with the same answer the kernel gave.
+
+SUBSYSTEM=="mem", MODE="0666"
+SUBSYSTEM=="tty", KERNEL=="console", GROUP="root", MODE="0600"
+SUBSYSTEM=="tty", KERNEL=="tty0|tty[0-9]|tty1[0-2]", GROUP="tty", MODE="0660"
+SUBSYSTEM=="input", GROUP="input", MODE="0660"
+SUBSYSTEM=="graphics", GROUP="video", MODE="0660"
+SUBSYSTEM=="block", GROUP="disk", MODE="0660"