From ba705c909d98c181e126c952c97e2d56d8c7a24e Mon Sep 17 00:00:00 2001
From: Gordon GECOS <u@adam>
Date: Wed, 3 Mar 2021 23:08:58 -0500
Subject: improve penme

---
 penme | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/penme b/penme
index 06356ab..4dbe2e8 100755
--- a/penme
+++ b/penme
@@ -1,36 +1,40 @@
 #!/bin/sh
+set -e
 if [ "$(id -u)" -ne 0 ]
 then
         exec sudo -- "$0" "$@"
 fi
 
+vprintf() { [ ! "$VERBOSE" ] || printf "$@" >&2; }
+
+write()
+{
+        printf '%s\n' "$line" >> /root/.ssh/authorized_keys
+        vprintf 'New root authorization: %s\n' "$line"
+        [ "$VERBOSE" ] || printf '%s\n' "$line" >&2
+}
+
 scan_network()
 {
-        ip -oneline addr |
-        sed -ne 's/.*inet \([^ ]*\) .*/\1/p' |
-        while read line
-        do
-                case "$line" in
-                        127.*) continue ;;
-                esac
-                arp-scan "$line" 2>/dev/null
-        done | while read ip junk
+        arp-scan --localnet |
+        while read ip junk
         do
                 case "$ip" in
-                        *.*.*.*) echo $ip ;;
+                        *.*.*.*) ;;
                         *) continue ;;
                 esac
+                vprintf 'ARP scan found IP: %s\n' "$ip"
+                ( grep -q " penme host key @ $ip\$" /root/.ssh/authorized_keys ) || echo $ip
         done
 }
 
-ips=$(scan_network)
-
 mkdir -p /root/.ssh
-touch /root/.ssh/authorized_keys
+[ -e /root/.ssh/authorized_keys ] || touch /root/.ssh/authorized_keys
 
-ssh-keyscan - $ips | while read ip key
+ssh-keyscan - $(scan_network) 2>/dev/null |
+while read ip key
 do
-        line=$(printf '%s host key @ %s\n' "$key" "$ip")
-        grep -Fx "$line" /root/.ssh/authorized_keys ||
-        echo "$line" >> /root/.ssh/authorized_keys
+        line=$(printf '%s penme host key @ %s\n' "$key" "$ip")
+        grep -q -Fx "$line" /root/.ssh/authorized_keys && vprintf 'Already authorized: %s\n' "$line" ||
+        write "$line" /root/.ssh/authorized_keys
 done
-- 
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