From 56ac0705da55800ce01e96d6a95433b90ab7f0bc Mon Sep 17 00:00:00 2001
From: Darren 'Tadgy' Austin <darren@afterdark.org.uk>
Date: Mon, 8 Mar 2021 19:18:51 +0000
Subject: Add SLAAC security and privacy options.

This patch adds some security and privacy enhancements to SLAAC configuration.
When SLAAC_PRIVIPGEN is "yes", address generation is enhanced with a secret
key for the interface set in SLAAC_SECRET.  This prevents predictable
address generation.
When SLAAC_TEMPADDR is "yes", a temporary address is used with SLAAC.

Thanks to davjohn from LQ for the inital patches and help testing.
---
 netconfig     | 10 ++++++++++
 rc.inet1      | 19 +++++++++++++++++--
 rc.inet1.conf | 10 ++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/netconfig b/netconfig
index 56b8593..a33b85d 100644
--- a/netconfig
+++ b/netconfig
@@ -232,6 +232,16 @@ GATEWAY6="$GATEWAY6"
 #SLAAC_TIMEOUT[4]="15"          # The default timeout for auto configuration to
                                 # wait for the interface to come up is 15 sec.
                                 # Increase the timeout if required.
+#SLAAC_PRIVIPGEN[4]="yes"       # When assigning addresses via SLAAC, use the
+                                # 'private' (RFC7217) address generation method.
+                                # It is advisable to also set SLAAC_SECRET[x].
+#SLAAC_SECRET[4]="xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx"
+                                # When SLAAC_PRIVIPGEN[x]="yes" is set, this is
+                                # the secret to be used.  This must be in the
+                                # form of an IPv6 address.  When left unset, a
+                                # random secret is used (this is the default).
+#SLAAC_TEMPADDR[4]="yes"        # Use a temporary address with SLAAC to enhance
+                                # security.
 #USE_RA[4]="yes"                # Accept router advertisements even when SLAAC
                                 # is disabled on the interface.
 #WLAN_ESSID[4]="DARKSTAR"       # An example of how you can override _any_
diff --git a/rc.inet1 b/rc.inet1
index a9ae95b..7de9920 100644
--- a/rc.inet1
+++ b/rc.inet1
@@ -329,6 +329,18 @@ if_up() {
       IF_UP=0
       if [ -e /proc/sys/net/ipv6 ] && [ "${USE_DHCP6[$i]}" != "yes" ] && [ "${USE_SLAAC[$i]}" = "yes" ]; then # configure via SLAAC
         info_log "${1}: enabling SLAAC"
+        if [ "${SLAAC_PRIVIPGEN[$i]}" = "yes" ]; then
+          if [ -n "${SLAAC_SECRET[$i]}" ]; then
+            echo "${SLAAC_SECRET[$i]}" >/proc/sys/net/ipv6/conf/${1}/stable_secret
+            echo "2" >/proc/sys/net/ipv6/conf/${1}/addr_gen_mode
+          else
+            echo -n >/proc/sys/net/ipv6/conf/${1}/stable_secret
+            echo "3" >/proc/sys/net/ipv6/conf/${1}/addr_gen_mode
+          fi
+        fi
+        if [ "${SLAAC_TEMPADDR[$i]}" = "yes" ]; then
+          echo "2" >/proc/sys/net/ipv6/conf/${1}/use_tempaddr
+        fi
         # Enable accepting of RA packets, unless explicitly configured not to:
         if [ "${USE_RA[$i]}" = "no" ]; then
           debug_log "${1}: ignoring IPv6 RA"
@@ -549,11 +561,14 @@ if_down() {
     # Bring the interface down:
     debug_log "/sbin/ip link set dev ${1} down"
     /sbin/ip link set dev ${1} down
-    # Reset autoconf and accept_ra back to defaults:
+    # Reset everything back to defaults:
     if [ -e /proc/sys/net/ipv6 ]; then
-      debug_log "${1}: resetting IPv6 autoconf and RA to defaults"
+      debug_log "${1}: resetting IPv6 configuration to defaults"
       cat /proc/sys/net/ipv6/conf/default/autoconf >/proc/sys/net/ipv6/conf/${1}/autoconf
       cat /proc/sys/net/ipv6/conf/default/accept_ra >/proc/sys/net/ipv6/conf/${1}/accept_ra
+      cat /proc/sys/net/ipv6/conf/defailt/use_tempaddr >/proc/sys/net/ipv6/conf/${1}/use_tempaddr
+      cat /proc/sys/net/ipv6/conf/default/addr_gen_mode >/proc/sys/net/ipv6/conf/${1}/addr_gen_mode
+      echo -n >/proc/sys/net/ipv6/conf/${1}/stable_secret
     fi
     # If the interface is a bridge, then destroy it now:
     [ -n "${BRNICS[$i]}" ] && br_close $i
diff --git a/rc.inet1.conf b/rc.inet1.conf
index 26ef87e..e952498 100644
--- a/rc.inet1.conf
+++ b/rc.inet1.conf
@@ -198,6 +198,16 @@ GATEWAY6=""
 #SLAAC_TIMEOUT[4]="15"          # The default timeout for auto configuration to
                                 # wait for the interface to come up is 15 sec.
                                 # Increase the timeout if required.
+#SLAAC_PRIVIPGEN[4]="yes"       # When assigning addresses via SLAAC, use the
+                                # 'private' (RFC7217) address generation method.
+                                # It is advisable to also set SLAAC_SECRET[x].
+#SLAAC_SECRET[4]="xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx"
+                                # When SLAAC_PRIVIPGEN[x]="yes" is set, this is
+                                # the secret to be used.  This must be in the
+                                # form of an IPv6 address.  When left unset, a
+                                # random secret is used (this is the default).
+#SLAAC_TEMPADDR[4]="yes"        # Use a temporary address with SLAAC to enhance
+                                # security.
 #USE_RA[4]="yes"                # Accept router advertisements even when SLAAC
                                 # is disabled on the interface.
 #WLAN_ESSID[4]="DARKSTAR"       # An example of how you can override _any_
-- 
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