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quickstart: recognize likely NAT setup and set up host IPs in "NATIPs…
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…" field in the public listener

for issue #59 by pmarini, thanks!
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@mjl-
mjl- committed Sep 21, 2023
1 parent cde5444 commit d649cf7
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Showing 3 changed files with 129 additions and 73 deletions.
196 changes: 125 additions & 71 deletions quickstart.go
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Original file line number Diff line number Diff line change
Expand Up @@ -149,78 +149,76 @@ logging in with IMAP.
// We are going to find the (public) IPs to listen on and possibly the host name.

// Start with reasonable defaults. We'll replace them specific IPs, if we can find them.
publicListenerIPs := []string{"0.0.0.0", "::"}
privateListenerIPs := []string{"127.0.0.1", "::1"}
publicListenerIPs := []string{"0.0.0.0", "::"}
var publicNATIPs []string // Actual public IP, but when it is NATed and machine doesn't have direct access.
defaultPublicListenerIPs := true

// If we find IPs based on network interfaces, {public,private}ListenerIPs are set
// based on these values.
var privateIPs, publicIPs []string
var loopbackIPs, privateIPs, publicIPs []string

var dnshostname dns.Domain
if hostname == "" {
// Gather IP addresses for public and private listeners.
// If we cannot find addresses for a category we fallback to all ips or localhost ips.
// We look at each network interface. If an interface has a private address, we
// conservatively assume all addresses on that interface are private.
ifaces, err := net.Interfaces()
// Gather IP addresses for public and private listeners.
// We look at each network interface. If an interface has a private address, we
// conservatively assume all addresses on that interface are private.
ifaces, err := net.Interfaces()
if err != nil {
fatalf("listing network interfaces: %s", err)
}
parseAddrIP := func(s string) net.IP {
if strings.HasPrefix(s, "[") && strings.HasSuffix(s, "]") {
s = s[1 : len(s)-1]
}
ip, _, _ := net.ParseCIDR(s)
return ip
}
for _, iface := range ifaces {
if iface.Flags&net.FlagUp == 0 {
continue
}
addrs, err := iface.Addrs()
if err != nil {
fatalf("listing network interfaces: %s", err)
fatalf("listing address for network interface: %s", err)
}
parseAddrIP := func(s string) net.IP {
if strings.HasPrefix(s, "[") && strings.HasSuffix(s, "]") {
s = s[1 : len(s)-1]
}
ip, _, _ := net.ParseCIDR(s)
return ip
if len(addrs) == 0 {
continue
}
for _, iface := range ifaces {
if iface.Flags&net.FlagUp == 0 {

// todo: should we detect temporary/ephemeral ipv6 addresses and not add them?
var nonpublic bool
for _, addr := range addrs {
ip := parseAddrIP(addr.String())
if ip.IsInterfaceLocalMulticast() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast() || ip.IsMulticast() {
continue
}
addrs, err := iface.Addrs()
if err != nil {
fatalf("listing address for network interface: %s", err)
if ip.IsLoopback() || ip.IsPrivate() {
nonpublic = true
break
}
if len(addrs) == 0 {
}

for _, addr := range addrs {
ip := parseAddrIP(addr.String())
if ip == nil {
continue
}

// todo: should we detect temporary/ephemeral ipv6 addresses and not add them?
var nonpublic bool
for _, addr := range addrs {
ip := parseAddrIP(addr.String())
if ip.IsInterfaceLocalMulticast() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast() || ip.IsMulticast() {
continue
}
if ip.IsLoopback() || ip.IsPrivate() {
nonpublic = true
break
}
if ip.IsInterfaceLocalMulticast() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast() || ip.IsMulticast() {
continue
}

for _, addr := range addrs {
ip := parseAddrIP(addr.String())
if ip == nil {
continue
}
if ip.IsInterfaceLocalMulticast() || ip.IsLinkLocalMulticast() || ip.IsLinkLocalUnicast() || ip.IsMulticast() {
continue
}
if nonpublic {
privateIPs = append(privateIPs, ip.String())
if nonpublic {
if ip.IsLoopback() {
loopbackIPs = append(loopbackIPs, ip.String())
} else {
publicIPs = append(publicIPs, ip.String())
privateIPs = append(privateIPs, ip.String())
}
} else {
publicIPs = append(publicIPs, ip.String())
}
}
}

if len(publicIPs) > 0 {
publicListenerIPs = publicIPs
}
if len(privateIPs) > 0 {
privateListenerIPs = privateIPs
}

var dnshostname dns.Domain
if hostname == "" {
hostnameStr, err := os.Hostname()
if err != nil {
fatalf("hostname: %s", err)
Expand Down Expand Up @@ -311,9 +309,13 @@ again with the -hostname flag.
ips, err := resolver.LookupIPAddr(ipctx, dnshostname.ASCII+".")
ipcancel()
var xips []net.IPAddr
var xipstrs []string
var hostIPs []string
var dnswarned bool
hostPrivate := len(ips) > 0
for _, ip := range ips {
if !ip.IP.IsPrivate() {
hostPrivate = false
}
// During linux install, you may get an alias for you full hostname in /etc/hosts
// resolving to 127.0.1.1, which would result in a false positive about the
// hostname having a record. Filter it out. It is a bit surprising that hosts don't
Expand All @@ -324,17 +326,60 @@ again with the -hostname flag.
continue
}
xips = append(xips, ip)
xipstrs = append(xipstrs, ip.String())
hostIPs = append(hostIPs, ip.String())
}
if err == nil && len(xips) == 0 {
// todo: possibly check this by trying to resolve without using /etc/hosts?
err = errors.New("hostname not in dns, probably only in /etc/hosts")
}
ips = xips
if hostname != "" {
// Host name was specified, assume we will run on a machine with those IPs.
publicListenerIPs = xipstrs
publicIPs = xipstrs

// We may have found private and public IPs on the machine, and IPs for the host
// name we think we should use. They may not match with each other. E.g. the public
// IPs on interfaces could be different from the IPs for the host. We don't try to
// detect all possible configs, but just generate what makes sense given whether we
// found public/private/hostname IPs. If the user is doing sensible things, it
// should be correct. But they should be checking the generated config file anyway.
// And we do log which host name we are using, and whether we detected a NAT setup.
// In the future, we may do an interactive setup that can guide the user better.

if !hostPrivate && len(publicIPs) == 0 && len(privateIPs) > 0 {
// We only have private IPs, assume we are behind a NAT and put the IPs of the host in NATIPs.
publicListenerIPs = privateIPs
publicNATIPs = hostIPs
defaultPublicListenerIPs = false
if len(loopbackIPs) > 0 {
privateListenerIPs = loopbackIPs
}
} else {
if len(hostIPs) > 0 {
publicListenerIPs = hostIPs
defaultPublicListenerIPs = false

// Only keep private IPs that are not in host-based publicListenerIPs. For
// internal-only setups, including integration tests.
m := map[string]bool{}
for _, ip := range hostIPs {
m[ip] = true
}
var npriv []string
for _, ip := range privateIPs {
if !m[ip] {
npriv = append(npriv, ip)
}
}
sort.Strings(npriv)
privateIPs = npriv
} else if len(publicIPs) > 0 {
publicListenerIPs = publicIPs
defaultPublicListenerIPs = false
hostIPs = publicIPs // For DNSBL check below.
}
if len(privateIPs) > 0 {
privateListenerIPs = append(privateIPs, loopbackIPs...)
} else if len(loopbackIPs) > 0 {
privateListenerIPs = loopbackIPs
}
}
if err != nil {
if !dnswarned {
Expand Down Expand Up @@ -422,11 +467,11 @@ This likely means one of two things:
{ASCII: "sbl.spamhaus.org"},
{ASCII: "bl.spamcop.net"},
}
if len(publicIPs) > 0 {
fmt.Printf("Checking whether your public IPs are listed in popular DNS block lists...")
if len(hostIPs) > 0 {
fmt.Printf("Checking whether host name IPs are listed in popular DNS block lists...")
var listed bool
for _, zone := range zones {
for _, ip := range publicIPs {
for _, ip := range hostIPs {
dnsblctx, dnsblcancel := context.WithTimeout(resolveCtx, 5*time.Second)
status, expl, err := dnsbl.Lookup(dnsblctx, resolver, zone, net.ParseIP(ip))
dnsblcancel()
Expand All @@ -449,7 +494,7 @@ email. Your IP may be in block lists only temporarily. To see if your IPs are
listed in more DNS block lists, visit:
`)
for _, ip := range publicIPs {
for _, ip := range hostIPs {
fmt.Printf("- https://multirbl.valli.org/lookup/%s.html\n", url.PathEscape(ip))
}
fmt.Printf("\n")
Expand All @@ -458,20 +503,28 @@ listed in more DNS block lists, visit:
}
}

if len(publicIPs) == 0 {
log.Printf(`WARNING: Could not find your public IP address(es). The "public" listener is
if defaultPublicListenerIPs {
log.Printf(`
WARNING: Could not find your public IP address(es). The "public" listener is
configured to listen on 0.0.0.0 (IPv4) and :: (IPv6). If you don't change these
to your actual public IP addresses, you will likely get "address in use" errors
when starting mox because the "internal" listener binds to a specific IP
address on the same port(s). If you are behind a NAT, instead configure the
actual public IPs in the listener's "NATIPs" option.
If you are behind a NAT that does not preserve the remote IPs of connections,
you will likely experience problems accepting email due to IP-based policies.
For example, SPF is a mechanism that checks if an IP address is allowed to send
`)
}
if len(publicNATIPs) > 0 {
log.Printf(`
NOTE: Quickstart used the IPs of the host name of the mail server, but only
found private IPs on the machine. This indicates this machine is behind a NAT,
so the host IPs were configured in the NATIPs field of the public listeners. If
you are behind a NAT that does not preserve the remote IPs of connections, you
will likely experience problems accepting email due to IP-based policies. For
example, SPF is a mechanism that checks if an IP address is allowed to send
email for a domain, and mox uses IP-based (non)junk classification, and IP-based
rate-limiting both for accepting email and blocking bad actors (such as with
too many authentication failures).
rate-limiting both for accepting email and blocking bad actors (such as with too
many authentication failures).
`)
}
Expand Down Expand Up @@ -510,7 +563,8 @@ too many authentication failures).
fmt.Printf("Admin password: %s\n", adminpw)

public := config.Listener{
IPs: publicListenerIPs,
IPs: publicListenerIPs,
NATIPs: publicNATIPs,
}
public.SMTP.Enabled = true
public.Submissions.Enabled = true
Expand Down
3 changes: 2 additions & 1 deletion testdata/integration/moxacmepebble.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,8 @@ mkdir /tmp/mox
cd /tmp/mox
mox quickstart [email protected] "$MOX_UID" > output.txt

sed -i -e '/- 172.28.1.10/d' -e 's/- 0.0.0.0/- 172.28.1.10/' -e '/- ::/d' -e 's/letsencrypt:/pebble:/g' -e 's/: letsencrypt/: pebble/g' -e 's,DirectoryURL: https://acme-v02.api.letsencrypt.org/directory,DirectoryURL: https://acmepebble.example:14000/dir,' -e 's/SMTP:$/SMTP:\n\t\t\tFirstTimeSenderDelay: 1s/' config/mox.conf
cp config/mox.conf config/mox.conf.orig
sed -i -e 's/letsencrypt:/pebble:/g' -e 's/: letsencrypt/: pebble/g' -e 's,DirectoryURL: https://acme-v02.api.letsencrypt.org/directory,DirectoryURL: https://acmepebble.example:14000/dir,' -e 's/SMTP:$/SMTP:\n\t\t\tFirstTimeSenderDelay: 1s/' config/mox.conf
cat <<EOF >>config/mox.conf
TLS:
Expand Down
3 changes: 2 additions & 1 deletion testdata/integration/moxmail2.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,8 @@ mkdir /tmp/mox
cd /tmp/mox
mox quickstart [email protected] "$MOX_UID" > output.txt

sed -i -e '/- 172.28.1.20/d' -e 's/- 0.0.0.0/- 172.28.1.20/' -e '/- ::/d' -e 's,ACME: .*$,KeyCerts:\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/moxmail2.pem\n\t\t\t\t\tKeyFile: /integration/tls/moxmail2-key.pem\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/mox2-autoconfig.pem\n\t\t\t\t\tKeyFile: /integration/tls/mox2-autoconfig-key.pem\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/mox2-mtasts.pem\n\t\t\t\t\tKeyFile: /integration/tls/mox2-mtasts-key.pem\n,' -e 's/SMTP:$/SMTP:\n\t\t\tFirstTimeSenderDelay: 1s/' config/mox.conf
cp config/mox.conf config/mox.conf.orig
sed -i -e 's,ACME: .*$,KeyCerts:\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/moxmail2.pem\n\t\t\t\t\tKeyFile: /integration/tls/moxmail2-key.pem\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/mox2-autoconfig.pem\n\t\t\t\t\tKeyFile: /integration/tls/mox2-autoconfig-key.pem\n\t\t\t\t-\n\t\t\t\t\tCertFile: /integration/tls/mox2-mtasts.pem\n\t\t\t\t\tKeyFile: /integration/tls/mox2-mtasts-key.pem\n,' -e 's/SMTP:$/SMTP:\n\t\t\tFirstTimeSenderDelay: 1s/' config/mox.conf
cat <<EOF >>config/mox.conf
TLS:
Expand Down

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