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caddy/modules/caddytls/automation.go
Ran Chen d9b1d46325
caddytls: dns_challenge_override_domain for challenge delegation (#4596)
* Add a override_domain option to allow DNS chanllenge delegation

CNAME can be used to delegate answering the chanllenge to another DNS
zone. One usage is to reduce the exposure of the DNS credential [1].
Based on the discussion in caddy/certmagic#160, we are adding an option
to allow the user explicitly specify the domain to delegate, instead of
following the CNAME chain.

This needs caddy/certmagic#160.

* rename override_domain to dns_challenge_override_domain

* Update CertMagic; fix spelling

Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>
2022-03-08 12:03:43 -07:00

432 lines
16 KiB
Go

// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package caddytls
import (
"encoding/json"
"fmt"
"net/http"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/certmagic"
"github.com/mholt/acmez"
)
// AutomationConfig governs the automated management of TLS certificates.
type AutomationConfig struct {
// The list of automation policies. The first policy matching
// a certificate or subject name will be applied.
Policies []*AutomationPolicy `json:"policies,omitempty"`
// On-Demand TLS defers certificate operations to the
// moment they are needed, e.g. during a TLS handshake.
// Useful when you don't know all the hostnames at
// config-time, or when you are not in control of the
// domain names you are managing certificates for.
// In 2015, Caddy became the first web server to
// implement this experimental technology.
//
// Note that this field does not enable on-demand TLS;
// it only configures it for when it is used. To enable
// it, create an automation policy with `on_demand`.
OnDemand *OnDemandConfig `json:"on_demand,omitempty"`
// Caddy staples OCSP (and caches the response) for all
// qualifying certificates by default. This setting
// changes how often it scans responses for freshness,
// and updates them if they are getting stale. Default: 1h
OCSPCheckInterval caddy.Duration `json:"ocsp_interval,omitempty"`
// Every so often, Caddy will scan all loaded, managed
// certificates for expiration. This setting changes how
// frequently the scan for expiring certificates is
// performed. Default: 10m
RenewCheckInterval caddy.Duration `json:"renew_interval,omitempty"`
// How often to scan storage units for old or expired
// assets and remove them. These scans exert lots of
// reads (and list operations) on the storage module, so
// choose a longer interval for large deployments.
// Default: 24h
//
// Storage will always be cleaned when the process first
// starts. Then, a new cleaning will be started this
// duration after the previous cleaning started if the
// previous cleaning finished in less than half the time
// of this interval (otherwise next start will be skipped).
StorageCleanInterval caddy.Duration `json:"storage_clean_interval,omitempty"`
defaultPublicAutomationPolicy *AutomationPolicy
defaultInternalAutomationPolicy *AutomationPolicy // only initialized if necessary
}
// AutomationPolicy designates the policy for automating the
// management (obtaining, renewal, and revocation) of managed
// TLS certificates.
//
// An AutomationPolicy value is not valid until it has been
// provisioned; use the `AddAutomationPolicy()` method on the
// TLS app to properly provision a new policy.
type AutomationPolicy struct {
// Which subjects (hostnames or IP addresses) this policy applies to.
Subjects []string `json:"subjects,omitempty"`
// The modules that may issue certificates. Default: internal if all
// subjects do not qualify for public certificates; othewise acme and
// zerossl.
IssuersRaw []json.RawMessage `json:"issuers,omitempty" caddy:"namespace=tls.issuance inline_key=module"`
// Modules that can get a custom certificate to use for any
// given TLS handshake at handshake-time. Custom certificates
// can be useful if another entity is managing certificates
// and Caddy need only get it and serve it.
//
// TODO: This is an EXPERIMENTAL feature. It is subject to change or removal.
ManagersRaw []json.RawMessage `json:"get_certificate,omitempty" caddy:"namespace=tls.get_certificate inline_key=via"`
// If true, certificates will be requested with MustStaple. Not all
// CAs support this, and there are potentially serious consequences
// of enabling this feature without proper threat modeling.
MustStaple bool `json:"must_staple,omitempty"`
// How long before a certificate's expiration to try renewing it,
// as a function of its total lifetime. As a general and conservative
// rule, it is a good idea to renew a certificate when it has about
// 1/3 of its total lifetime remaining. This utilizes the majority
// of the certificate's lifetime while still saving time to
// troubleshoot problems. However, for extremely short-lived certs,
// you may wish to increase the ratio to ~1/2.
RenewalWindowRatio float64 `json:"renewal_window_ratio,omitempty"`
// The type of key to generate for certificates.
// Supported values: `ed25519`, `p256`, `p384`, `rsa2048`, `rsa4096`.
KeyType string `json:"key_type,omitempty"`
// Optionally configure a separate storage module associated with this
// manager, instead of using Caddy's global/default-configured storage.
StorageRaw json.RawMessage `json:"storage,omitempty" caddy:"namespace=caddy.storage inline_key=module"`
// If true, certificates will be managed "on demand"; that is, during
// TLS handshakes or when needed, as opposed to at startup or config
// load. This enables On-Demand TLS for this policy.
OnDemand bool `json:"on_demand,omitempty"`
// Disables OCSP stapling. Disabling OCSP stapling puts clients at
// greater risk, reduces their privacy, and usually lowers client
// performance. It is NOT recommended to disable this unless you
// are able to justify the costs.
// EXPERIMENTAL. Subject to change.
DisableOCSPStapling bool `json:"disable_ocsp_stapling,omitempty"`
// Overrides the URLs of OCSP responders embedded in certificates.
// Each key is a OCSP server URL to override, and its value is the
// replacement. An empty value will disable querying of that server.
// EXPERIMENTAL. Subject to change.
OCSPOverrides map[string]string `json:"ocsp_overrides,omitempty"`
// Issuers and Managers store the decoded issuer and manager modules;
// they are only used to populate an underlying certmagic.Config's
// fields during provisioning so that the modules can survive a
// re-provisioning.
Issuers []certmagic.Issuer `json:"-"`
Managers []certmagic.CertificateManager `json:"-"`
magic *certmagic.Config
storage certmagic.Storage
}
// Provision sets up ap and builds its underlying CertMagic config.
func (ap *AutomationPolicy) Provision(tlsApp *TLS) error {
// policy-specific storage implementation
if ap.StorageRaw != nil {
val, err := tlsApp.ctx.LoadModule(ap, "StorageRaw")
if err != nil {
return fmt.Errorf("loading TLS storage module: %v", err)
}
cmStorage, err := val.(caddy.StorageConverter).CertMagicStorage()
if err != nil {
return fmt.Errorf("creating TLS storage configuration: %v", err)
}
ap.storage = cmStorage
}
// on-demand TLS
var ond *certmagic.OnDemandConfig
if ap.OnDemand {
ond = &certmagic.OnDemandConfig{
DecisionFunc: func(name string) error {
// if an "ask" endpoint was defined, consult it first
if tlsApp.Automation != nil &&
tlsApp.Automation.OnDemand != nil &&
tlsApp.Automation.OnDemand.Ask != "" {
err := onDemandAskRequest(tlsApp.Automation.OnDemand.Ask, name)
if err != nil {
return err
}
}
// check the rate limiter last because
// doing so makes a reservation
if !onDemandRateLimiter.Allow() {
return fmt.Errorf("on-demand rate limit exceeded")
}
return nil
},
}
}
// we don't store loaded modules directly in the certmagic config since
// policy provisioning may happen more than once (during auto-HTTPS) and
// loading a module clears its config bytes; thus, load the module and
// store them on the policy before putting it on the config
// load and provision any cert manager modules
if ap.ManagersRaw != nil {
vals, err := tlsApp.ctx.LoadModule(ap, "ManagersRaw")
if err != nil {
return fmt.Errorf("loading external certificate manager modules: %v", err)
}
for _, getCertVal := range vals.([]interface{}) {
ap.Managers = append(ap.Managers, getCertVal.(certmagic.CertificateManager))
}
}
// load and provision any explicitly-configured issuer modules
if ap.IssuersRaw != nil {
val, err := tlsApp.ctx.LoadModule(ap, "IssuersRaw")
if err != nil {
return fmt.Errorf("loading TLS automation management module: %s", err)
}
for _, issVal := range val.([]interface{}) {
ap.Issuers = append(ap.Issuers, issVal.(certmagic.Issuer))
}
}
issuers := ap.Issuers
if len(issuers) == 0 {
var err error
issuers, err = DefaultIssuersProvisioned(tlsApp.ctx)
if err != nil {
return err
}
}
keyType := ap.KeyType
if keyType != "" {
var err error
keyType, err = caddy.NewReplacer().ReplaceOrErr(ap.KeyType, true, true)
if err != nil {
return fmt.Errorf("invalid key type %s: %s", ap.KeyType, err)
}
if _, ok := supportedCertKeyTypes[keyType]; !ok {
return fmt.Errorf("unrecognized key type: %s", keyType)
}
}
keySource := certmagic.StandardKeyGenerator{
KeyType: supportedCertKeyTypes[keyType],
}
storage := ap.storage
if storage == nil {
storage = tlsApp.ctx.Storage()
}
template := certmagic.Config{
MustStaple: ap.MustStaple,
RenewalWindowRatio: ap.RenewalWindowRatio,
KeySource: keySource,
OnDemand: ond,
OCSP: certmagic.OCSPConfig{
DisableStapling: ap.DisableOCSPStapling,
ResponderOverrides: ap.OCSPOverrides,
},
Storage: storage,
Issuers: issuers,
Managers: ap.Managers,
Logger: tlsApp.logger,
}
ap.magic = certmagic.New(tlsApp.certCache, template)
// sometimes issuers may need the parent certmagic.Config in
// order to function properly (for example, ACMEIssuer needs
// access to the correct storage and cache so it can solve
// ACME challenges -- it's an annoying, inelegant circular
// dependency that I don't know how to resolve nicely!)
for _, issuer := range ap.magic.Issuers {
if annoying, ok := issuer.(ConfigSetter); ok {
annoying.SetConfig(ap.magic)
}
}
return nil
}
// DefaultIssuers returns empty Issuers (not provisioned) to be used as defaults.
// This function is experimental and has no compatibility promises.
func DefaultIssuers() []certmagic.Issuer {
return []certmagic.Issuer{
new(ACMEIssuer),
&ZeroSSLIssuer{ACMEIssuer: new(ACMEIssuer)},
}
}
// DefaultIssuersProvisioned returns empty but provisioned default Issuers from
// DefaultIssuers(). This function is experimental and has no compatibility promises.
func DefaultIssuersProvisioned(ctx caddy.Context) ([]certmagic.Issuer, error) {
issuers := DefaultIssuers()
for i, iss := range issuers {
if prov, ok := iss.(caddy.Provisioner); ok {
err := prov.Provision(ctx)
if err != nil {
return nil, fmt.Errorf("provisioning default issuer %d: %T: %v", i, iss, err)
}
}
}
return issuers, nil
}
// ChallengesConfig configures the ACME challenges.
type ChallengesConfig struct {
// HTTP configures the ACME HTTP challenge. This
// challenge is enabled and used automatically
// and by default.
HTTP *HTTPChallengeConfig `json:"http,omitempty"`
// TLSALPN configures the ACME TLS-ALPN challenge.
// This challenge is enabled and used automatically
// and by default.
TLSALPN *TLSALPNChallengeConfig `json:"tls-alpn,omitempty"`
// Configures the ACME DNS challenge. Because this
// challenge typically requires credentials for
// interfacing with a DNS provider, this challenge is
// not enabled by default. This is the only challenge
// type which does not require a direct connection
// to Caddy from an external server.
//
// NOTE: DNS providers are currently being upgraded,
// and this API is subject to change, but should be
// stabilized soon.
DNS *DNSChallengeConfig `json:"dns,omitempty"`
// Optionally customize the host to which a listener
// is bound if required for solving a challenge.
BindHost string `json:"bind_host,omitempty"`
}
// HTTPChallengeConfig configures the ACME HTTP challenge.
type HTTPChallengeConfig struct {
// If true, the HTTP challenge will be disabled.
Disabled bool `json:"disabled,omitempty"`
// An alternate port on which to service this
// challenge. Note that the HTTP challenge port is
// hard-coded into the spec and cannot be changed,
// so you would have to forward packets from the
// standard HTTP challenge port to this one.
AlternatePort int `json:"alternate_port,omitempty"`
}
// TLSALPNChallengeConfig configures the ACME TLS-ALPN challenge.
type TLSALPNChallengeConfig struct {
// If true, the TLS-ALPN challenge will be disabled.
Disabled bool `json:"disabled,omitempty"`
// An alternate port on which to service this
// challenge. Note that the TLS-ALPN challenge port
// is hard-coded into the spec and cannot be changed,
// so you would have to forward packets from the
// standard TLS-ALPN challenge port to this one.
AlternatePort int `json:"alternate_port,omitempty"`
}
// DNSChallengeConfig configures the ACME DNS challenge.
//
// NOTE: This API is still experimental and is subject to change.
type DNSChallengeConfig struct {
// The DNS provider module to use which will manage
// the DNS records relevant to the ACME challenge.
ProviderRaw json.RawMessage `json:"provider,omitempty" caddy:"namespace=dns.providers inline_key=name"`
// The TTL of the TXT record used for the DNS challenge.
TTL caddy.Duration `json:"ttl,omitempty"`
// How long to wait for DNS record to propagate.
PropagationTimeout caddy.Duration `json:"propagation_timeout,omitempty"`
// Custom DNS resolvers to prefer over system/built-in defaults.
// Often necessary to configure when using split-horizon DNS.
Resolvers []string `json:"resolvers,omitempty"`
// Override the domain to use for the DNS challenge. This
// is to delegate the challenge to a different domain,
// e.g. one that updates faster or one with a provider API.
OverrideDomain string `json:"override_domain,omitempty"`
solver acmez.Solver
}
// OnDemandConfig configures on-demand TLS, for obtaining
// needed certificates at handshake-time. Because this
// feature can easily be abused, you should use this to
// establish rate limits and/or an internal endpoint that
// Caddy can "ask" if it should be allowed to manage
// certificates for a given hostname.
type OnDemandConfig struct {
// An optional rate limit to throttle the
// issuance of certificates from handshakes.
RateLimit *RateLimit `json:"rate_limit,omitempty"`
// If Caddy needs to obtain or renew a certificate
// during a TLS handshake, it will perform a quick
// HTTP request to this URL to check if it should be
// allowed to try to get a certificate for the name
// in the "domain" query string parameter, like so:
// `?domain=example.com`. The endpoint must return a
// 200 OK status if a certificate is allowed;
// anything else will cause it to be denied.
// Redirects are not followed.
Ask string `json:"ask,omitempty"`
}
// RateLimit specifies an interval with optional burst size.
type RateLimit struct {
// A duration value. A certificate may be obtained 'burst'
// times during this interval.
Interval caddy.Duration `json:"interval,omitempty"`
// How many times during an interval a certificate can be obtained.
Burst int `json:"burst,omitempty"`
}
// ConfigSetter is implemented by certmagic.Issuers that
// need access to a parent certmagic.Config as part of
// their provisioning phase. For example, the ACMEIssuer
// requires a config so it can access storage and the
// cache to solve ACME challenges.
type ConfigSetter interface {
SetConfig(cfg *certmagic.Config)
}
// These perpetual values are used for on-demand TLS.
var (
onDemandRateLimiter = certmagic.NewRateLimiter(0, 0)
onDemandAskClient = &http.Client{
Timeout: 10 * time.Second,
CheckRedirect: func(req *http.Request, via []*http.Request) error {
return fmt.Errorf("following http redirects is not allowed")
},
}
)