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override tscert.TailscaledTransport with muxing transport
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This provides an http.RoundTripper implementation that dynamically
routes requests to the correct tsnet server's LocalAPI based on the
ClientHelloInfo in the context.

Previously, we were just overriding the tscert Dialer. That worked fine
the first time it dialed a LocalAPI, and would correctly dial the right
tsnet server. However, tscert caches the Transport with that Dialer, so
requests that should be routed to different tsnet servers would be
routed incorrectly.

Updates #19
Updates #53
Updates #66

Signed-off-by: Will Norris <will@tailscale.com>
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willnorris committed Jun 7, 2024
1 parent 5cc2140 commit 4b6f3fe
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Showing 3 changed files with 51 additions and 34 deletions.
2 changes: 1 addition & 1 deletion go.mod
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ require (
github.com/caddyserver/caddy/v2 v2.8.4
github.com/caddyserver/certmagic v0.21.3
github.com/google/go-cmp v0.6.0
github.com/tailscale/tscert v0.0.0-20240517230440-bbccfbf48933
github.com/tailscale/tscert v0.0.0-20240607232451-34704dbdb4b3
go.uber.org/zap v1.27.0
tailscale.com v1.67.0-pre.0.20240602211424-42cfbf427c67
)
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4 changes: 2 additions & 2 deletions go.sum
Original file line number Diff line number Diff line change
Expand Up @@ -521,8 +521,8 @@ github.com/tailscale/netlink v1.1.1-0.20211101221916-cabfb018fe85 h1:zrsUcqrG2uQ
github.com/tailscale/netlink v1.1.1-0.20211101221916-cabfb018fe85/go.mod h1:NzVQi3Mleb+qzq8VmcWpSkcSYxXIg0DkI6XDzpVkhJ0=
github.com/tailscale/peercred v0.0.0-20240214030740-b535050b2aa4 h1:Gz0rz40FvFVLTBk/K8UNAenb36EbDSnh+q7Z9ldcC8w=
github.com/tailscale/peercred v0.0.0-20240214030740-b535050b2aa4/go.mod h1:phI29ccmHQBc+wvroosENp1IF9195449VDnFDhJ4rJU=
github.com/tailscale/tscert v0.0.0-20240517230440-bbccfbf48933 h1:pV0H+XIvFoP7pl1MRtyPXh5hqoxB5I7snOtTHgrn6HU=
github.com/tailscale/tscert v0.0.0-20240517230440-bbccfbf48933/go.mod h1:kNGUQ3VESx3VZwRwA9MSCUegIl6+saPL8Noq82ozCaU=
github.com/tailscale/tscert v0.0.0-20240607232451-34704dbdb4b3 h1:KKyPUIj4xlNYCryHDjvaQs92jYaEyYrmLAC9Ip4S6js=
github.com/tailscale/tscert v0.0.0-20240607232451-34704dbdb4b3/go.mod h1:kNGUQ3VESx3VZwRwA9MSCUegIl6+saPL8Noq82ozCaU=
github.com/tailscale/web-client-prebuilt v0.0.0-20240226180453-5db17b287bf1 h1:tdUdyPqJ0C97SJfjB9tW6EylTtreyee9C44de+UBG0g=
github.com/tailscale/web-client-prebuilt v0.0.0-20240226180453-5db17b287bf1/go.mod h1:agQPE6y6ldqCOui2gkIh7ZMztTkIQKH049tv8siLuNQ=
github.com/tailscale/wf v0.0.0-20240214030419-6fbb0a674ee6 h1:l10Gi6w9jxvinoiq15g8OToDdASBni4CyJOdHY1Hr8M=
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79 changes: 48 additions & 31 deletions module.go
Original file line number Diff line number Diff line change
Expand Up @@ -12,17 +12,20 @@ import (
"crypto/tls"
"fmt"
"net"
"net/http"
"net/netip"
"os"
"path/filepath"
"strconv"
"strings"
"sync"

"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"github.com/caddyserver/certmagic"
"github.com/tailscale/tscert"
"go.uber.org/zap"
"tailscale.com/client/tailscale"
"tailscale.com/hostinfo"
"tailscale.com/tsnet"
)
Expand All @@ -36,7 +39,8 @@ func init() {
// Caddy uses tscert to get certificates for Tailscale hostnames.
// Update the tscert dialer to dial the LocalAPI of the correct tsnet node,
// rather than just always dialing the local tailscaled.
tscert.TailscaledDialer = localAPIDialer
//tscert.TailscaledDialer = localAPIDialer
tscert.TailscaledTransport = &tsnetMuxTransport{}
hostinfo.SetApp("caddy")
}

Expand Down Expand Up @@ -317,40 +321,53 @@ func (t *tsnetServerListener) Close() error {
return err
}

// localAPIDialer finds the node that matches the requested certificate in ctx
// and dials that node's local API.
// If no matching node is found, the default dialer is used,
// which tries to connect to a local tailscaled on the machine.
func localAPIDialer(ctx context.Context, network, addr string) (net.Conn, error) {
if addr != "local-tailscaled.sock:80" {
return nil, fmt.Errorf("unexpected URL address %q", addr)
}
// localAPITransport is an [http.RoundTripper] that sends requests to a [tailscale.LocalClient]'s LocalAPI.
type localAPITransport struct {
*tailscale.LocalClient
}

func (t *localAPITransport) RoundTrip(req *http.Request) (*http.Response, error) {
return t.DoLocalRequest(req)
}

// tsnetMuxTransport is an [http.RoundTripper] that sends requests to the LocalAPI
// for the tsnet server that matches the ClientHelloInfo server name.
// If no tsnet server matches, a default Transport is used.
type tsnetMuxTransport struct {
defaultTransport *http.Transport
defaultTransportOnce sync.Once
}

func (t *tsnetMuxTransport) RoundTrip(req *http.Request) (*http.Response, error) {
ctx := req.Context()
var rt http.RoundTripper

clientHello, ok := ctx.Value(certmagic.ClientHelloInfoCtxKey).(*tls.ClientHelloInfo)
if !ok || clientHello == nil {
return tscert.DialLocalAPI(ctx, network, addr)
}

var tn *tailscaleNode
nodes.Range(func(key, value any) bool {
if n, ok := value.(*tailscaleNode); ok && n != nil {
for _, d := range n.CertDomains() {
// Tailscale doesn't do wildcard certs, but caddy uses MatchWildcard
// for the built-in Tailscale cert manager, so we do so here as well.
if certmagic.MatchWildcard(clientHello.ServerName, d) {
tn = n
return false
if ok && clientHello != nil {
nodes.Range(func(key, value any) bool {
if n, ok := value.(*tailscaleNode); ok && n != nil {
for _, d := range n.CertDomains() {
// Tailscale doesn't do wildcard certs, but caddy uses MatchWildcard
// for the built-in Tailscale cert manager, so we do so here as well.
if certmagic.MatchWildcard(clientHello.ServerName, d) {
if lc, err := n.LocalClient(); err == nil {
rt = &localAPITransport{lc}
}
return false
}
}
}
}
return true
})

if tn != nil {
if lc, err := tn.LocalClient(); err == nil {
return lc.Dial(ctx, network, addr)
}
return true
})
}

return tscert.DialLocalAPI(ctx, network, addr)
if rt == nil {
t.defaultTransportOnce.Do(func() {
t.defaultTransport = &http.Transport{
DialContext: tscert.TailscaledDialer,
}
})
rt = t.defaultTransport
}
return rt.RoundTrip(req)
}

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