Configure Auto Configuration on All IPv6 Interfaces
Sets net.ipv6.conf.all.autoconf to 0 so the host does not auto-assign IPv6 addresses from prefixes learned via Router Advertisements (SLAAC).
Checked against the resolved running state (e.g. sshd -T, sysctl, systemctl show), catches drop-ins and Includes a file read would miss. Caveat: runtime ≠ persistence; a value correct now may not survive a reboot.
Pavois asserts the effective configuration, the live, resolved state, not a file. File-based scanners (OVAL/SCAP, Lynis) miss Includes, drop-ins and runtime defaults; this check sees what is actually applied.
A mapping is a cross-reference to where each standard places this requirement, anchored and cross-validated, not a claim of equivalence. A passing check is evidence toward these references, how to read it.
Why this rule matters
Stateless address autoconfiguration (SLAAC) derives IPv6 addresses from prefixes announced in unauthenticated Router Advertisements. A rogue node can advertise forged prefixes to make the host configure attacker-influenced addresses and routing, enabling man-in-the-middle attacks. On servers with deliberate, static addressing, autoconf adds unpredictability and attack surface for no benefit.
What Pavois checks
Pavois reads the effective runtime value via the kernel_parameter resource (equivalent to sysctl net.ipv6.conf.all.autoconf) and asserts it is 0. The live value is authoritative: a setting in /etc/sysctl.d/* may be shadowed by a later drop-in or never applied, so the running parameter is the only reliable evidence, file inspection can give a false pass.
describe kernel_parameter('net.ipv6.conf.all.autoconf') do
its('value') { should cmp 0 }
end
describe command("grep -hsE '^[[:space:]]*net.ipv6.conf.all.autoconf[[:space:]]*=[[:space:]]*0([[:space:]]|$)' /etc/sysctl.conf /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf 2>/dev/null") do
its('stdout') { should match(/\S/) }
endHow to verify it is applied
Run sysctl net.ipv6.conf.all.autoconf (or cat /proc/sys/net/ipv6/conf/all/autoconf). Expected output:
net.ipv6.conf.all.autoconf = 0
Inspect & investigate
No dedicated log. Check the live value with sysctl net.ipv6.conf.all.autoconf, audit its source with sysctl --system, and confirm no autoconfigured addresses appear with ip -6 addr show.
Remediation
Pavois's harden plan uses the sysctl resource to set net.ipv6.conf.all.autoconf to 0, persisting it in a Pavois-owned /etc/sysctl.d/ drop-in and applying it live (no reboot). Run it with pavois harden apply.
Pavois applies this with its own harden engine, the plan below, not a shell script:
| key | net.ipv6.conf.all.autoconf |
|---|---|
| resource | sysctl |
| value | 0 |
pavois harden plan localwhere the target is local, a user@host SSH alias, or a container , Docs
Impact & precautions
On hosts that obtain their IPv6 address via SLAAC, disabling autoconf removes that address and can break IPv6 connectivity. Apply only where the host uses static IPv6 or DHCPv6, verify the addressing model first. Do not enforce on systems intended to autoconfigure. No effect on IPv4-only hosts.
Standards mapping
| Standard | Reference | Type | Version | Confidence |
|---|---|---|---|---|
| ANSSI BP-028 | R13 | direct | 2.0 | high |
Each reference is a cross-reference anchored in the upstream benchmark and cross-validated against the SCAP Security Guide and ansible-lockdown, not a claim of equivalence. Direct = a prescriptive, line-level requirement; supporting = an abstract control family (NIST) the check provides evidence toward. How to read a mapping.