fix(amneziawg): resolve 7 Medium findings from the automated PR review

Each is independently reproducible; fixed together since one review pass found all of them. - manager.go: the shared "ip rule add fwmark" policy route had no existence check, so it duplicated in "ip rule show" on every interface bounce (which hostRulesFingerprint forces on any client add/remove/ re-IP). Now checked via "ip rule list | grep -q ..." first. (Finding 2) - params.go: ExternalInterface, IPv6ExternalInterface, and subnetIp/ subnetCidr are interpolated unescaped into a shell-executed PostUp/ PostDown line, but only obfuscation and the IPv6 subnet were validated before save. Added ValidateInterfaceName (a strict charset+length pattern) and ValidateSubnetIPv4 (netip.ParsePrefix), wired into normalizeAmneziaWGSettings. (Finding 3) - amneziawg_job.go: IsAwgInstalled() existed but nothing ever called it, so a host without awg/awg-quick (the Docker image, RHEL, Arch, a failed install.sh PPA step) logged a reconcile failure every 10s forever. Now checked once an inbound actually needs it, warning once instead of spamming. (Finding 4) - client_inbound_apply.go: the WireGuard/AmneziaWG credential carry-forward (added so a metadata-only client edit doesn't rotate keys) never covered ForwardedPorts, so a partial edit -- an API call or Telegram-bot toggle that omits the field -- silently wiped a client's port-forwarding spec. Carried forward and written back the same way the key fields already are. (Finding 5) - manager.go: hostRulesFingerprint keyed each peer on its IPv4 address only, and structuralFingerprint omitted IPv6Enabled/IPv6ExternalInterface entirely, so an IPv6-only change could pick the syncconf reload path (which never re-runs PostUp, leaving a stale NDP-proxy entry) or be a complete no-op. Both fingerprints now cover the IPv6 fields. (Finding 6) - port_conflict.go: the AmneziaWG egress bridge (injectAmneziawgEgress) binds 127.0.0.1:63100+id with no collision check anywhere, since it isn't a database row the ordinary port-conflict query can see -- same blind spot the reserved Xray API port already has its own check for. Added the equivalent check for the AmneziaWG bridge port. (Finding 7) - install.sh: install_amneziawg ran unconditionally for every install/ update, building a DKMS kernel module and enabling host-wide IPv4/IPv6 forwarding whether or not the feature is ever used. Gated behind a new should_install_amneziawg (XUI_INSTALL_AMNEZIAWG=true/false, or an interactive y/N prompt defaulting to no). Also replaced the deprecated apt-key adv with a dedicated keyring + signed-by= on the Debian branch, and guarded its sources.list appends against duplication on a retried install. (Finding 8) Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-09-19 08:37:14 +00:00 · 2026-07-26 00:16:20 +03:00
parent f5543047b7
commit c41f97cf86
10 changed files with 376 additions and 9 deletions
@@ -134,6 +134,8 @@ func (inst Instance) structuralFingerprint() string {
 		strconv.Itoa(o.S1), strconv.Itoa(o.S2), strconv.Itoa(o.S3), strconv.Itoa(o.S4),
 		o.H1, o.H2, o.H3, o.H4, o.I1,
 		inst.ExternalInterface,
+		strconv.FormatBool(inst.IPv6Enabled),
+		inst.IPv6ExternalInterface,
 	}
 	return strings.Join(parts, "|")
 }
@@ -155,8 +157,9 @@ func (inst Instance) peersFingerprint() string {
 }

 // hostRulesFingerprint identifies per-peer state that only ever takes effect
-// through PostUp/PostDown shell rules — forwarded ports, and (unconditionally,
-// for every peer with a usable IPv4 address) the TPROXY rule into this
+// through PostUp/PostDown shell rules — forwarded ports, the peer's IPv6
+// address (its NDP-proxy PostUp/PostDown entry), and (unconditionally, for
+// every peer with a usable IPv4 address) the TPROXY rule into this
 // instance's own Xray bridge — rather than the WireGuard peer table itself.
 // It is checked separately from peersFingerprint because `awg syncconf`
 // never re-runs PostUp/PostDown, so a change here must force a full
@@ -165,11 +168,15 @@ func (inst Instance) peersFingerprint() string {
 // now tied to every peer's mere presence (there's no more per-peer opt-in
 // flag), every peer is included unconditionally: adding, removing, or
 // re-addressing a peer now also forces a bounce, the same way a
-// ForwardedPorts-only change always did.
+// ForwardedPorts-only change always did. The IPv6 address must be included
+// here too: without it, a peer that only changes its IPv6 AllowedIPs entry
+// still matches on FirstIPv4 alone, so ensureActionFor would pick the
+// syncconf reload path — which never re-runs PostUp — leaving that peer's
+// NDP-proxy entry pointed at its old, now-wrong address.
 func (inst Instance) hostRulesFingerprint() string {
 	pairs := make([]string, 0, len(inst.Peers))
 	for _, p := range inst.Peers {
-		pairs = append(pairs, fmt.Sprintf("%s=fwd:%s;ip:%s", p.Email, p.ForwardedPorts, FirstIPv4(p.AllowedIPs)))
+		pairs = append(pairs, fmt.Sprintf("%s=fwd:%s;ip:%s;ip6:%s", p.Email, p.ForwardedPorts, FirstIPv4(p.AllowedIPs), firstIPv6(p.AllowedIPs)))
 	}
 	slices.Sort(pairs)
 	return strings.Join(pairs, "|")
@@ -687,8 +694,13 @@ func defaultPostUpDown(inst Instance, ext string) (postUp, postDown string) {
 		// IPv6-forwarding sysctl above — it is added idempotently here and
 		// never torn down in PostDown; a second AmneziaWG instance must find
 		// it already in place, not race to remove what the first still needs.
+		// "ip rule add" is not itself idempotent (a second call inserts a
+		// duplicate rather than deduplicating), and hostRulesFingerprint keys
+		// on every peer's presence/IP, so PostUp re-runs on any client
+		// add/remove/re-IP — without the existence check below, "ip rule
+		// show" would accumulate one duplicate entry per bounce forever.
 		up = append(up,
-			fmt.Sprintf("ip rule add fwmark %#x lookup %d 2>/dev/null || true", EgressFwmark, EgressTable),
+			fmt.Sprintf("ip rule list | grep -q 'fwmark %#x lookup %d' || ip rule add fwmark %#x lookup %d", EgressFwmark, EgressTable, EgressFwmark, EgressTable),
 			fmt.Sprintf("ip route replace local 0.0.0.0/0 dev lo table %d", EgressTable),
 		)
 	}
@@ -156,6 +156,21 @@ func TestStructuralFingerprintStableAndSensitive(t *testing.T) {
 	if a.structuralFingerprint() != c.structuralFingerprint() {
 		t.Fatal("a peer-only change must NOT change the structural fingerprint")
 	}
+
+	d := baseInstance()
+	d.IPv6Enabled = true
+	if a.structuralFingerprint() == d.structuralFingerprint() {
+		t.Fatal("enabling IPv6 must change the structural fingerprint")
+	}
+
+	e := baseInstance()
+	e.IPv6Enabled = true
+	f := baseInstance()
+	f.IPv6Enabled = true
+	f.IPv6ExternalInterface = "eth1"
+	if e.structuralFingerprint() == f.structuralFingerprint() {
+		t.Fatal("changing IPv6ExternalInterface must change the structural fingerprint -- otherwise the edit is a complete no-op")
+	}
 }

 func TestPeersFingerprintOrderIndependentButContentSensitive(t *testing.T) {
@@ -231,6 +246,12 @@ func TestHostRulesFingerprintCoversForwardedPortsAndPeerIP(t *testing.T) {
 	if a.hostRulesFingerprint() == fewer.hostRulesFingerprint() {
 		t.Fatal("removing a peer must change the host-rules fingerprint -- one fewer TPROXY rule is needed")
 	}
+
+	ip6Added := baseInstance()
+	ip6Added.Peers[0].AllowedIPs = []string{"10.8.1.2/32", "fd86:ea04:1115::2/128"}
+	if a.hostRulesFingerprint() == ip6Added.hostRulesFingerprint() {
+		t.Fatal("adding a peer's IPv6 address must change the host-rules fingerprint -- its NDP-proxy entry is keyed on it, and a change here must force the full bounce that (re-)runs PostUp")
+	}
 }

 func TestRouteEgressComment(t *testing.T) {
@@ -308,6 +329,9 @@ func TestDefaultPostUpDownEmitsTproxyForEveryPeer(t *testing.T) {
 	if !strings.Contains(up, fmt.Sprintf("ip rule add fwmark %#x", EgressFwmark)) {
 		t.Errorf("expected the shared policy route to be added once in PostUp, got:\n%s", up)
 	}
+	if wantCheck := fmt.Sprintf("ip rule list | grep -q 'fwmark %#x lookup %d'", EgressFwmark, EgressTable); !strings.Contains(up, wantCheck) {
+		t.Errorf("expected an existence check before 'ip rule add', so repeated bounces don't accumulate duplicate rules, got:\n%s", up)
+	}
 	if strings.Contains(down, "ip rule") || strings.Contains(down, "ip route") {
 		t.Error("the shared policy route must never be removed in PostDown -- other instances may still need it")
 	}
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"math/big"
 	"net/netip"
+	"regexp"
 	"strconv"
 	"strings"
 )
@@ -140,6 +141,54 @@ func ValidateIPv6Subnet(enabled bool, subnet string) error {
 	return nil
 }

+// interfaceNamePattern matches a plausible Linux network interface name:
+// letters, digits, and the handful of separators seen in real device names
+// (eth0, wg0, br-lan, eno1.100, eth0:0), capped at 15 bytes (IFNAMSIZ-1).
+var interfaceNamePattern = regexp.MustCompile(`^[A-Za-z0-9_.@:-]{1,15}$`)
+
+// ValidateInterfaceName rejects a value that isn't a plausible network
+// interface name before it's saved. ExternalInterface and
+// IPv6ExternalInterface are interpolated unescaped into a shell-executed
+// PostUp/PostDown line by generateServerConfig, so — unlike the client email
+// (already hashed for exactly this reason, see routeEgressComment) — an
+// unvalidated value here could carry a shell metacharacter straight into a
+// root-executed command. A blank value is allowed: it means "auto-detect"
+// for ExternalInterface, or "reuse ExternalInterface" for
+// IPv6ExternalInterface.
+func ValidateInterfaceName(name string) error {
+	if name == "" {
+		return nil
+	}
+	if !interfaceNamePattern.MatchString(name) {
+		return fmt.Errorf("invalid interface name %q: must be 1-15 characters of letters, digits, '.', '_', '@', ':' or '-'", name)
+	}
+	return nil
+}
+
+// ValidateSubnetIPv4 rejects a malformed IPv4 tunnel subnet before it's
+// saved: subnetIP is interpolated into the PostUp/PostDown MASQUERADE rule
+// the same way ExternalInterface is (see ValidateInterfaceName), so it needs
+// the same protection against a value that isn't really an address at all.
+// subnetCIDR <= 0 is treated as unset, mirroring serverAddress's own
+// default-to-/24 leniency.
+func ValidateSubnetIPv4(subnetIP string, subnetCIDR int) error {
+	cidr := subnetCIDR
+	if cidr <= 0 {
+		cidr = 24
+	}
+	if cidr > 32 {
+		return fmt.Errorf("invalid subnetCidr %d: must be 0..32", subnetCIDR)
+	}
+	prefix, err := netip.ParsePrefix(fmt.Sprintf("%s/%d", subnetIP, cidr))
+	if err != nil {
+		return fmt.Errorf("invalid subnetIp %q: %w", subnetIP, err)
+	}
+	if !prefix.Addr().Is4() {
+		return fmt.Errorf("invalid subnetIp %q: not an IPv4 address", subnetIP)
+	}
+	return nil
+}
+
 // validateHValue checks one H parameter: empty, a single uint32, or
 // "low-high" with 0 <= low <= high <= uint32 max.
 func validateHValue(v string) error {
@@ -153,3 +153,61 @@ func TestValidateObfuscationRejectsBadH(t *testing.T) {
 		}
 	}
 }
+
+func TestValidateInterfaceNameAcceptsBlankAndPlausibleNames(t *testing.T) {
+	for _, name := range []string{"", "eth0", "wg0", "br-lan", "eno1.100", "veth1a2b3c", "eth0:0"} {
+		if err := ValidateInterfaceName(name); err != nil {
+			t.Errorf("ValidateInterfaceName(%q) rejected a plausible name: %v", name, err)
+		}
+	}
+}
+
+func TestValidateInterfaceNameRejectsShellMetacharactersAndOverlength(t *testing.T) {
+	cases := []string{
+		"eth0 -j ACCEPT; rm -rf /",
+		"eth0`whoami`",
+		"eth0$(id)",
+		"eth0|cat /etc/passwd",
+		"eth0\nMASQUERADE",
+		"aaaaaaaaaaaaaaaaaaaa", // 20 chars, over IFNAMSIZ-1
+	}
+	for _, name := range cases {
+		if err := ValidateInterfaceName(name); err == nil {
+			t.Errorf("ValidateInterfaceName(%q) must be rejected", name)
+		}
+	}
+}
+
+func TestValidateSubnetIPv4AcceptsValidBases(t *testing.T) {
+	cases := []struct {
+		ip   string
+		cidr int
+	}{
+		{"10.8.1.0", 24},
+		{"10.8.1.0", 0}, // cidr <= 0 defaults to /24, mirroring serverAddress
+		{"192.168.5.10", 32},
+	}
+	for _, c := range cases {
+		if err := ValidateSubnetIPv4(c.ip, c.cidr); err != nil {
+			t.Errorf("ValidateSubnetIPv4(%q, %d) rejected a valid subnet: %v", c.ip, c.cidr, err)
+		}
+	}
+}
+
+func TestValidateSubnetIPv4RejectsMalformedOrInjectedValues(t *testing.T) {
+	cases := []struct {
+		ip   string
+		cidr int
+	}{
+		{"10.8.1.0 -j ACCEPT; rm -rf /", 24}, // shell injection attempt
+		{"not-an-ip", 24},
+		{"", 24},
+		{"fd86::1", 64},  // IPv6, not IPv4
+		{"10.8.1.0", 33}, // cidr out of range
+	}
+	for _, c := range cases {
+		if err := ValidateSubnetIPv4(c.ip, c.cidr); err == nil {
+			t.Errorf("ValidateSubnetIPv4(%q, %d) must be rejected", c.ip, c.cidr)
+		}
+	}
+}