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package caddytls
import (
"context"
"crypto/tls"
"fmt"
"io"
"net/http"
"net/url"
"strings"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
"github.com/caddyserver/certmagic"
"github.com/tailscale/tscert"
"go.uber.org/zap"
)
func init() {
caddy.RegisterModule(Tailscale{})
caddy.RegisterModule(HTTPCertGetter{})
}
// Tailscale is a module that can get certificates from the local Tailscale process.
type Tailscale struct {
// If true, this module will operate in "best-effort" mode and
// ignore "soft" errors; i.e. try Tailscale, and if it doesn't connect
// or return a certificate, oh well. Failure to connect to Tailscale
// results in a no-op instead of an error. Intended for the use case
// where this module is added implicitly for convenience, even if
// Tailscale isn't necessarily running.
Optional bool `json:"optional,omitempty"`
logger *zap.Logger
}
// CaddyModule returns the Caddy module information.
func (Tailscale) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "tls.get_certificate.tailscale",
New: func() caddy.Module { return new(Tailscale) },
}
}
func (ts *Tailscale) Provision(ctx caddy.Context) error {
ts.logger = ctx.Logger(ts)
return nil
}
func (ts Tailscale) GetCertificate(ctx context.Context, hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
canGetCert, err := ts.canHazCertificate(ctx, hello)
if err == nil && !canGetCert {
return nil, nil // pass-thru: Tailscale can't offer a cert for this name
}
if err != nil {
ts.logger.Warn("could not get status; will try to get certificate anyway", zap.Error(err))
}
return tscert.GetCertificate(hello)
}
// canHazCertificate returns true if Tailscale reports it can get a certificate for the given ClientHello.
func (ts Tailscale) canHazCertificate(ctx context.Context, hello *tls.ClientHelloInfo) (bool, error) {
if ts.Optional && !strings.HasSuffix(strings.ToLower(hello.ServerName), tailscaleDomainAliasEnding) {
return false, nil
}
status, err := tscert.GetStatus(ctx)
if err != nil {
if ts.Optional {
// ignore error if we don't expect/require it to work anyway, but log it for debugging
ts.logger.Debug("error getting tailscale status", zap.Error(err), zap.String("server_name", hello.ServerName))
return false, nil
}
return false, err
}
for _, domain := range status.CertDomains {
if certmagic.MatchWildcard(hello.ServerName, domain) {
return true, nil
}
}
return false, nil
}
// UnmarshalCaddyfile deserializes Caddyfile tokens into ts.
//
// ... tailscale
func (Tailscale) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
for d.Next() {
if d.NextArg() {
return d.ArgErr()
}
}
return nil
}
// tailscaleDomainAliasEnding is the ending for all Tailscale custom domains.
const tailscaleDomainAliasEnding = ".ts.net"
// HTTPCertGetter can get a certificate via HTTP(S) request.
type HTTPCertGetter struct {
// The URL from which to download the certificate. Required.
//
// The URL will be augmented with query string parameters taken
// from the TLS handshake:
//
// - server_name: The SNI value
// - signature_schemes: Comma-separated list of hex IDs of signatures
// - cipher_suites: Comma-separated list of hex IDs of cipher suites
//
// To be valid, the response must be HTTP 200 with a PEM body
// consisting of blocks for the certificate chain and the private
// key.
URL string `json:"url,omitempty"`
ctx context.Context
}
// CaddyModule returns the Caddy module information.
func (hcg HTTPCertGetter) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "tls.get_certificate.http",
New: func() caddy.Module { return new(HTTPCertGetter) },
}
}
func (hcg *HTTPCertGetter) Provision(ctx caddy.Context) error {
hcg.ctx = ctx
if hcg.URL == "" {
return fmt.Errorf("URL is required")
}
return nil
}
func (hcg HTTPCertGetter) GetCertificate(ctx context.Context, hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
sigs := make([]string, len(hello.SignatureSchemes))
for i, sig := range hello.SignatureSchemes {
sigs[i] = fmt.Sprintf("%x", uint16(sig)) // you won't believe what %x uses if the val is a Stringer
}
suites := make([]string, len(hello.CipherSuites))
for i, cs := range hello.CipherSuites {
suites[i] = fmt.Sprintf("%x", cs)
}
parsed, err := url.Parse(hcg.URL)
if err != nil {
return nil, err
}
qs := parsed.Query()
qs.Set("server_name", hello.ServerName)
qs.Set("signature_schemes", strings.Join(sigs, ","))
qs.Set("cipher_suites", strings.Join(suites, ","))
parsed.RawQuery = qs.Encode()
req, err := http.NewRequestWithContext(hcg.ctx, http.MethodGet, parsed.String(), nil)
if err != nil {
return nil, err
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("got HTTP %d", resp.StatusCode)
}
bodyBytes, err := io.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("error reading response body: %v", err)
}
cert, err := tlsCertFromCertAndKeyPEMBundle(bodyBytes)
if err != nil {
return nil, err
}
return &cert, nil
}
// UnmarshalCaddyfile deserializes Caddyfile tokens into ts.
//
// ... http <url>
func (hcg *HTTPCertGetter) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
for d.Next() {
if !d.NextArg() {
return d.ArgErr()
}
hcg.URL = d.Val()
if d.NextArg() {
return d.ArgErr()
}
for nesting := d.Nesting(); d.NextBlock(nesting); {
return d.Err("block not allowed here")
}
}
return nil
}
// Interface guards
var (
_ certmagic.Manager = (*Tailscale)(nil)
_ caddy.Provisioner = (*Tailscale)(nil)
_ caddyfile.Unmarshaler = (*Tailscale)(nil)
_ certmagic.Manager = (*HTTPCertGetter)(nil)
_ caddy.Provisioner = (*HTTPCertGetter)(nil)
_ caddyfile.Unmarshaler = (*HTTPCertGetter)(nil)
)
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