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// 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 (
"context"
"crypto/tls"
"encoding/json"
"errors"
"fmt"
"net"
"strings"
"github.com/caddyserver/certmagic"
"github.com/mholt/acmez/v2"
"go.uber.org/zap"
"github.com/caddyserver/caddy/v2"
)
// 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.
//
// This list is a filter, not a command. In other words, it is used
// only to filter whether this policy should apply to a subject that
// needs a certificate; it does NOT command the TLS app to manage a
// certificate for that subject. To have Caddy automate a certificate
// or specific subjects, use the "automate" certificate loader module
// of the TLS app.
SubjectsRaw []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. Specifying a Manager
// enables on-demand TLS, i.e. it has the side-effect of setting
// the on_demand parameter to `true`.
//
// TODO: This is an EXPERIMENTAL feature. 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"`
// If true, private keys already existing in storage
// will be reused. Otherwise, a new key will be
// created for every new certificate to mitigate
// pinning and reduce the scope of key compromise.
// TEMPORARY: Key pinning is against industry best practices.
// This property will likely be removed in the future.
// Do not rely on it forever; watch the release notes.
ReusePrivateKeys bool `json:"reuse_private_keys,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.Manager `json:"-"`
subjects []string
magic *certmagic.Config
storage certmagic.Storage
}
// Provision sets up ap and builds its underlying CertMagic config.
func (ap *AutomationPolicy) Provision(tlsApp *TLS) error {
// replace placeholders in subjects to allow environment variables
repl := caddy.NewReplacer()
subjects := make([]string, len(ap.SubjectsRaw))
for i, sub := range ap.SubjectsRaw {
subjects[i] = repl.ReplaceAll(sub, "")
}
ap.subjects = subjects
// 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
}
// 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
hadExplicitManagers := len(ap.ManagersRaw) > 0
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.([]any) {
ap.Managers = append(ap.Managers, getCertVal.(certmagic.Manager))
}
}
// 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.([]any) {
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()
}
// on-demand TLS
var ond *certmagic.OnDemandConfig
if ap.OnDemand || len(ap.Managers) > 0 {
// permission module is now required after a number of negligence cases that allowed abuse;
// but it may still be optional for explicit subjects (bounded, non-wildcard), for the
// internal issuer since it doesn't cause public PKI pressure on ACME servers; subtly, it
// is useful to allow on-demand TLS to be enabled so Managers can be used, but to still
// prevent issuance from Issuers (when Managers don't provide a certificate) if there's no
// permission module configured
noProtections := ap.isWildcardOrDefault() && !ap.onlyInternalIssuer() && (tlsApp.Automation == nil || tlsApp.Automation.OnDemand == nil || tlsApp.Automation.OnDemand.permission == nil)
failClosed := noProtections && hadExplicitManagers // don't allow on-demand issuance (other than implicit managers) if no managers have been explicitly configured
if noProtections {
if !hadExplicitManagers {
// no managers, no explicitly-configured permission module, this is a config error
return fmt.Errorf("on-demand TLS cannot be enabled without a permission module to prevent abuse; please refer to documentation for details")
}
// allow on-demand to be enabled but only for the purpose of the Managers; issuance won't be allowed from Issuers
tlsApp.logger.Warn("on-demand TLS can only get certificates from the configured external manager(s) because no ask endpoint / permission module is specified")
}
ond = &certmagic.OnDemandConfig{
DecisionFunc: func(ctx context.Context, name string) error {
if failClosed {
return fmt.Errorf("no permission module configured; certificates not allowed except from external Managers")
}
if tlsApp.Automation == nil || tlsApp.Automation.OnDemand == nil {
return nil
}
// logging the remote IP can be useful for servers that want to count
// attempts from clients to detect patterns of abuse -- it should NOT be
// used solely for decision making, however
var remoteIP string
if hello, ok := ctx.Value(certmagic.ClientHelloInfoCtxKey).(*tls.ClientHelloInfo); ok && hello != nil {
if remote := hello.Conn.RemoteAddr(); remote != nil {
remoteIP, _, _ = net.SplitHostPort(remote.String())
}
}
tlsApp.logger.Debug("asking for permission for on-demand certificate",
zap.String("remote_ip", remoteIP),
zap.String("domain", name))
// ask the permission module if this cert is allowed
if err := tlsApp.Automation.OnDemand.permission.CertificateAllowed(ctx, name); err != nil {
// distinguish true errors from denials, because it's important to elevate actual errors
if errors.Is(err, ErrPermissionDenied) {
tlsApp.logger.Debug("on-demand certificate issuance denied",
zap.String("domain", name),
zap.Error(err))
} else {
tlsApp.logger.Error("failed to get permission for on-demand certificate",
zap.String("domain", name),
zap.Error(err))
}
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
},
Managers: ap.Managers,
}
}
template := certmagic.Config{
MustStaple: ap.MustStaple,
RenewalWindowRatio: ap.RenewalWindowRatio,
KeySource: keySource,
OnEvent: tlsApp.onEvent,
OnDemand: ond,
ReusePrivateKeys: ap.ReusePrivateKeys,
OCSP: certmagic.OCSPConfig{
DisableStapling: ap.DisableOCSPStapling,
ResponderOverrides: ap.OCSPOverrides,
},
Storage: storage,
Issuers: issuers,
Logger: tlsApp.logger,
}
certCacheMu.RLock()
ap.magic = certmagic.New(certCache, template)
certCacheMu.RUnlock()
// 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
}
// Subjects returns the list of subjects with all placeholders replaced.
func (ap *AutomationPolicy) Subjects() []string {
return ap.subjects
}
// AllInternalSubjects returns true if all the subjects on this policy are internal.
func (ap *AutomationPolicy) AllInternalSubjects() bool {
for _, subj := range ap.subjects {
if !certmagic.SubjectIsInternal(subj) {
return false
}
}
return true
}
func (ap *AutomationPolicy) onlyInternalIssuer() bool {
if len(ap.Issuers) != 1 {
return false
}
_, ok := ap.Issuers[0].(*InternalIssuer)
return ok
}
// isWildcardOrDefault determines if the subjects include any wildcard domains,
// or is the "default" policy (i.e. no subjects) which is unbounded.
func (ap *AutomationPolicy) isWildcardOrDefault() bool {
isWildcardOrDefault := false
if len(ap.subjects) == 0 {
isWildcardOrDefault = true
}
for _, sub := range ap.subjects {
if strings.HasPrefix(sub, "*") {
isWildcardOrDefault = true
break
}
}
return isWildcardOrDefault
}
// DefaultIssuers returns empty Issuers (not provisioned) to be used as defaults.
// This function is experimental and has no compatibility promises.
func DefaultIssuers(userEmail string) []certmagic.Issuer {
issuers := []certmagic.Issuer{new(ACMEIssuer)}
if strings.TrimSpace(userEmail) != "" {
issuers = append(issuers, &ACMEIssuer{
CA: certmagic.ZeroSSLProductionCA,
Email: userEmail,
})
}
return issuers
}
// 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.
// Required.
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 before starting propagation checks.
// Default: 0 (no wait).
PropagationDelay caddy.Duration `json:"propagation_delay,omitempty"`
// Maximum time to wait for temporary DNS record to appear.
// Set to -1 to disable propagation checks.
// Default: 2 minutes.
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
}
// 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)
}
|