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733 lines (670 loc) · 27.9 KB
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// Copyright 2015 Matthew Holt
//
// 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 certmagic
import (
"context"
"crypto/tls"
"crypto/x509"
"encoding/json"
"errors"
"fmt"
"math/rand/v2"
"net"
"os"
"strings"
"time"
"github.com/mholt/acmez/v3/acme"
"go.uber.org/zap"
"golang.org/x/crypto/ocsp"
)
// Certificate is a tls.Certificate with associated metadata tacked on.
// Even if the metadata can be obtained by parsing the certificate,
// we are more efficient by extracting the metadata onto this struct,
// but at the cost of slightly higher memory use.
type Certificate struct {
tls.Certificate
// Names is the list of subject names this
// certificate is signed for.
Names []string
// Optional; user-provided, and arbitrary.
Tags []string
// OCSP contains the certificate's parsed OCSP response.
// It is not necessarily the response that is stapled
// (e.g. if the status is not Good), it is simply the
// most recent OCSP response we have for this certificate.
ocsp *ocsp.Response
// The hex-encoded hash of this cert's chain's DER bytes.
hash string
// Whether this certificate is under our management.
managed bool
// The unique string identifying the issuer of this certificate.
issuerKey string
// ACME Renewal Information, if available
ari acme.RenewalInfo
}
// Empty returns true if the certificate struct is not filled out; at
// least the tls.Certificate.Certificate field is expected to be set.
func (cert Certificate) Empty() bool {
return len(cert.Certificate.Certificate) == 0
}
// Hash returns a checksum of the certificate chain's DER-encoded bytes.
func (cert Certificate) Hash() string { return cert.hash }
// NeedsRenewal returns true if the certificate is expiring
// soon (according to ARI and/or cfg) or has expired.
func (cert Certificate) NeedsRenewal(cfg *Config) bool {
return cfg.certNeedsRenewal(cert.Leaf, cert.ari, true)
}
// certNeedsRenewal consults ACME Renewal Info (ARI) and certificate expiration to determine
// whether the leaf certificate needs to be renewed yet. If true is returned, the certificate
// should be renewed as soon as possible. The reasoning for a true return value is logged
// unless emitLogs is false; this can be useful to suppress noisy logs in the case where you
// first call this to determine if a cert in memory needs renewal, and then right after you
// call it again to see if the cert in storage still needs renewal -- you probably don't want
// to log the second time for checking the cert in storage which is mainly for synchronization.
func (cfg *Config) certNeedsRenewal(leaf *x509.Certificate, ari acme.RenewalInfo, emitLogs bool) bool {
// though this should never happen, safeguard to avoid panics which happened before (since patched; but just in case)
if leaf == nil {
if emitLogs {
cfg.Logger.Error("cannot check if nil leaf cert needs renewal")
}
return false
}
cfg.certCache.optionsMu.RLock()
renewCheckInterval := cfg.certCache.options.RenewCheckInterval
cfg.certCache.optionsMu.RUnlock()
expiration := expiresAt(leaf)
var logger *zap.Logger
if emitLogs {
logger = cfg.Logger.With(
zap.Strings("subjects", leaf.DNSNames),
zap.Time("expiration", expiration),
zap.String("ari_cert_id", ari.UniqueIdentifier),
zap.Timep("next_ari_update", ari.RetryAfter),
zap.Duration("renew_check_interval", renewCheckInterval),
zap.Time("window_start", ari.SuggestedWindow.Start),
zap.Time("window_end", ari.SuggestedWindow.End))
} else {
logger = zap.NewNop()
}
if !cfg.DisableARI {
// first check ARI: if it says it's time to renew, it's time to renew
// (notice that we don't strictly require an ARI window to also exist; we presume
// that if a time has been selected, a window does or did exist, even if it didn't
// get stored/encoded for some reason - but also: this allows administrators to
// manually or explicitly schedule a renewal time independently of ARI which could
// be useful)
selectedTime := ari.SelectedTime
// if, for some reason a random time in the window hasn't been selected yet, but an ARI
// window does exist, we can always improvise one... even if this is called repeatedly,
// a random time is a random time, whether you generate it once or more :D
// (code borrowed from our acme package)
if selectedTime.IsZero() &&
(!ari.SuggestedWindow.Start.IsZero() && !ari.SuggestedWindow.End.IsZero()) {
start, end := ari.SuggestedWindow.Start.Unix()+1, ari.SuggestedWindow.End.Unix()
selectedTime = time.Unix(rand.Int64N(end-start)+start, 0).UTC()
logger.Warn("no renewal time had been selected with ARI; chose an ephemeral one for now",
zap.Time("ephemeral_selected_time", selectedTime))
}
// if a renewal time has been selected, start with that
if !selectedTime.IsZero() {
// ARI spec recommends an algorithm that renews after the randomly-selected
// time OR just before it if the next waking time would be after it; this
// cutoff can actually be before the start of the renewal window, but the spec
// author says that's OK: https://github.com/aarongable/draft-acme-ari/issues/71
cutoff := ari.SelectedTime.Add(-renewCheckInterval)
if time.Now().After(cutoff) {
logger.Info("certificate needs renewal based on ARI window",
zap.Time("selected_time", selectedTime),
zap.Time("renewal_cutoff", cutoff))
return true
}
// according to ARI, we are not ready to renew; however, we do not rely solely on
// ARI calculations... what if there is a bug in our implementation, or in the
// server's, or the stored metadata? for redundancy, give credence to the expiration
// date; ignore ARI if we are past a "dangerously close" limit, to avoid any
// possibility of a bug in ARI compromising a site's uptime: we should always always
// always give heed to actual validity period
if currentlyInRenewalWindow(leaf.NotBefore, expiration, 1.0/20.0) {
logger.Warn("certificate is in emergency renewal window; superseding ARI",
zap.Duration("remaining", time.Until(expiration)),
zap.Time("renewal_cutoff", cutoff))
return true
}
}
}
// the normal check, in the absence of ARI, is to determine if we're near enough (or past)
// the expiration date based on the configured remaining:lifetime ratio
if currentlyInRenewalWindow(leaf.NotBefore, expiration, cfg.RenewalWindowRatio) {
logger.Info("certificate is in configured renewal window based on expiration date",
zap.Duration("remaining", time.Until(expiration)))
return true
}
// finally, if the certificate is expiring imminently, always attempt a renewal;
// we check both a (very low) lifetime ratio and also a strict difference between
// the time until expiration and the interval at which we run the standard maintenance
// routine to check for renewals, to accommodate both exceptionally long and short
// cert lifetimes
if currentlyInRenewalWindow(leaf.NotBefore, expiration, 1.0/50.0) ||
time.Until(expiration) < renewCheckInterval*5 {
logger.Warn("certificate is in emergency renewal window; expiration imminent",
zap.Duration("remaining", time.Until(expiration)))
return true
}
return false
}
// Expired returns true if the certificate has expired.
func (cert Certificate) Expired() bool {
if cert.Leaf == nil {
// ideally cert.Leaf would never be nil, but this can happen for
// "synthetic" certs like those made to solve the TLS-ALPN challenge
// which adds a special cert directly to the cache, since
// tls.X509KeyPair() discards the leaf; oh well
return false
}
return time.Now().After(expiresAt(cert.Leaf))
}
// Lifetime returns the duration of the certificate's validity.
func (cert Certificate) Lifetime() time.Duration {
if cert.Leaf == nil || cert.Leaf.NotAfter.IsZero() {
return 0
}
return expiresAt(cert.Leaf).Sub(cert.Leaf.NotBefore)
}
// currentlyInRenewalWindow returns true if the current time is within
// (or after) the renewal window, according to the given start/end
// dates and the ratio of the renewal window. If true is returned,
// the certificate being considered is due for renewal. The ratio
// is remaining:total time, i.e. 1/3 = 1/3 of lifetime remaining,
// or 9/10 = 9/10 of time lifetime remaining.
func currentlyInRenewalWindow(notBefore, notAfter time.Time, renewalWindowRatio float64) bool {
if notAfter.IsZero() {
return false
}
lifetime := notAfter.Sub(notBefore)
if renewalWindowRatio == 0 {
renewalWindowRatio = DefaultRenewalWindowRatio
}
renewalWindow := time.Duration(float64(lifetime) * renewalWindowRatio)
renewalWindowStart := notAfter.Add(-renewalWindow)
return time.Now().After(renewalWindowStart)
}
// HasTag returns true if cert.Tags has tag.
func (cert Certificate) HasTag(tag string) bool {
for _, t := range cert.Tags {
if t == tag {
return true
}
}
return false
}
// expiresAt return the time that a certificate expires. Account for the 1s
// resolution of ASN.1 UTCTime/GeneralizedTime by including the extra fraction
// of a second of certificate validity beyond the NotAfter value.
func expiresAt(cert *x509.Certificate) time.Time {
if cert == nil {
return time.Time{}
}
return cert.NotAfter.Truncate(time.Second).Add(1 * time.Second)
}
// CacheManagedCertificate loads the certificate for domain into the
// cache, from the TLS storage for managed certificates. It returns a
// copy of the Certificate that was put into the cache.
//
// This is a lower-level method; normally you'll call Manage() instead.
//
// This method is safe for concurrent use.
func (cfg *Config) CacheManagedCertificate(ctx context.Context, domain string) (Certificate, error) {
domain = cfg.transformSubject(ctx, nil, domain)
cert, err := cfg.loadManagedCertificate(ctx, domain, cfg.cachedStorage())
if cfg.LocalCache != nil && errors.Is(err, errUnusableCert) {
// the local cache may hold a torn write, such as a renewed certificate
// next to the key it replaced; loading from storage replaces the local
// copies with ones that belong together
cfg.Logger.Warn("certificate assets from local cache are unusable; reloading from storage",
zap.String("identifier", domain),
zap.Error(err))
cert, err = cfg.loadManagedCertificate(ctx, domain, cfg.groundTruthStorage())
}
if err != nil {
return cert, err
}
cfg.certCache.cacheCertificate(cert)
cfg.emit(ctx, "cached_managed_cert", map[string]any{"sans": cert.Names})
return cert, nil
}
// WarmLocalCache copies the certificate assets for domain from Storage into
// the LocalCache, so that a later handshake needing that certificate can load
// it without reaching Storage; assets already in the local cache are left
// alone. Unlike CacheManagedCertificate, the certificate is not put into the
// in-memory cache, and no certificate operations are performed: this only
// warms the local cache.
//
// It is an error to call this without a LocalCache configured, since there
// would be nothing to warm. Callers warming many domains should limit their
// concurrency.
//
// EXPERIMENTAL: Subject to change or removal.
func (cfg *Config) WarmLocalCache(ctx context.Context, domain string) error {
if cfg.LocalCache == nil {
return fmt.Errorf("no local cache configured; nothing to warm")
}
domain = cfg.transformSubject(ctx, nil, domain)
_, err := cfg.loadCertResourceAnyIssuer(ctx, domain, cfg.cachedStorage())
return err
}
// loadManagedCertificate loads the managed certificate for domain from any
// of the configured issuers' storage locations, but it does not add it to
// the cache. It just loads from the given storage and returns it: see
// cachedStorage and groundTruthStorage.
func (cfg *Config) loadManagedCertificate(ctx context.Context, domain string, storage Storage) (Certificate, error) {
certRes, err := cfg.loadCertResourceAnyIssuer(ctx, domain, storage)
if err != nil {
return Certificate{}, err
}
cert, err := cfg.makeCertificateWithOCSP(ctx, certRes.CertificatePEM, certRes.PrivateKeyPEM)
if err != nil {
// the assets were all there, they just don't make a certificate
return cert, fmt.Errorf("%w: %w", errUnusableCert, err)
}
cert.managed = true
cert.issuerKey = certRes.issuerKey
if ari, err := certRes.getARI(); err == nil && ari != nil {
cert.ari = *ari
}
return cert, nil
}
// getARI unpacks ACME Renewal Information from the issuer data, if available.
// It is only an error if there is invalid JSON.
func (certRes CertificateResource) getARI() (*acme.RenewalInfo, error) {
acmeData, err := certRes.getACMEData()
if err != nil {
return nil, err
}
return acmeData.RenewalInfo, nil
}
// getACMEData returns the ACME certificate metadata from the IssuerData, but
// note that a non-ACME-issued certificate may return an empty value and nil
// since the JSON may still decode successfully but just not match any or all
// of the fields. Remember that the IssuerKey is used to store and access the
// cert files in the first place (it is part of the path) so in theory if you
// load a CertificateResource from an ACME issuer it should work as expected.
func (certRes CertificateResource) getACMEData() (acme.Certificate, error) {
if len(certRes.IssuerData) == 0 {
return acme.Certificate{}, nil
}
var acmeCert acme.Certificate
err := json.Unmarshal(certRes.IssuerData, &acmeCert)
return acmeCert, err
}
// CacheUnmanagedCertificatePEMFile loads a certificate for host using certFile
// and keyFile, which must be in PEM format. It stores the certificate in
// the in-memory cache and returns the hash, useful for removing from the cache.
//
// This method is safe for concurrent use.
func (cfg *Config) CacheUnmanagedCertificatePEMFile(ctx context.Context, certFile, keyFile string, tags []string) (string, error) {
cert, err := cfg.makeCertificateFromDiskWithOCSP(ctx, certFile, keyFile)
if err != nil {
return "", err
}
cert.Tags = tags
cfg.certCache.cacheCertificate(cert)
cfg.emit(ctx, "cached_unmanaged_cert", map[string]any{"sans": cert.Names})
return cert.hash, nil
}
// CacheUnmanagedTLSCertificate adds tlsCert to the certificate cache
//
// and returns the hash, useful for removing from the cache.
//
// It staples OCSP if possible.
//
// This method is safe for concurrent use.
func (cfg *Config) CacheUnmanagedTLSCertificate(ctx context.Context, tlsCert tls.Certificate, tags []string) (string, error) {
var cert Certificate
err := fillCertFromLeaf(&cert, tlsCert)
if err != nil {
return "", err
}
if time.Now().After(cert.Leaf.NotAfter) {
cfg.Logger.Warn("unmanaged certificate has expired",
zap.Time("not_after", cert.Leaf.NotAfter),
zap.Strings("sans", cert.Names))
} else if time.Until(cert.Leaf.NotAfter) < 24*time.Hour {
cfg.Logger.Warn("unmanaged certificate expires within 1 day",
zap.Time("not_after", cert.Leaf.NotAfter),
zap.Strings("sans", cert.Names))
}
if !cfg.OCSP.DisableStapling {
err = stapleOCSP(ctx, cfg.OCSP, cfg.cachedStorage(), &cert, nil)
if err != nil {
if errors.Is(err, ErrNoOCSPServerSpecified) {
cfg.Logger.Debug("stapling OCSP", zap.Error(err))
} else {
cfg.Logger.Warn("stapling OCSP", zap.Error(err))
}
}
}
cfg.emit(ctx, "cached_unmanaged_cert", map[string]any{"sans": cert.Names})
cert.Tags = tags
cfg.certCache.cacheCertificate(cert)
return cert.hash, nil
}
// CacheUnmanagedCertificatePEMBytes makes a certificate out of the PEM bytes
// of the certificate and key, then caches it in memory, and returns the hash,
// which is useful for removing from the cache.
//
// This method is safe for concurrent use.
func (cfg *Config) CacheUnmanagedCertificatePEMBytes(ctx context.Context, certBytes, keyBytes []byte, tags []string) (string, error) {
cert, err := cfg.makeCertificateWithOCSP(ctx, certBytes, keyBytes)
if err != nil {
return "", err
}
cert.Tags = tags
cfg.certCache.cacheCertificate(cert)
cfg.emit(ctx, "cached_unmanaged_cert", map[string]any{"sans": cert.Names})
return cert.hash, nil
}
// CacheUnmanagedCertificatePEMBytesAsReplacement is the same as CacheUnmanagedCertificatePEMBytes,
// but it also removes any other loaded certificates for the SANs on the certificate being cached.
// This has the effect of using this certificate exclusively and immediately for its SANs. The SANs
// for which the certificate should apply may optionally be passed in as well. By default, a cert
// is used for any of its SANs.
//
// This method is safe for concurrent use.
//
// EXPERIMENTAL: Subject to change/removal.
func (cfg *Config) CacheUnmanagedCertificatePEMBytesAsReplacement(ctx context.Context, certBytes, keyBytes []byte, tags, sans []string) (string, error) {
cert, err := cfg.makeCertificateWithOCSP(ctx, certBytes, keyBytes)
if err != nil {
return "", err
}
cert.Tags = tags
if len(sans) > 0 {
cert.Names = sans
}
cfg.certCache.mu.Lock()
for _, san := range cert.Names {
existingCerts := cfg.certCache.getAllMatchingCerts(san)
for _, existingCert := range existingCerts {
cfg.certCache.removeCertificate(existingCert)
}
}
cfg.certCache.unsyncedCacheCertificate(cert)
cfg.certCache.mu.Unlock()
cfg.emit(ctx, "cached_unmanaged_cert", map[string]any{"sans": cert.Names, "replacement": true})
return cert.hash, nil
}
// makeCertificateFromDiskWithOCSP makes a Certificate by loading the
// certificate and key files. It fills out all the fields in
// the certificate except for the Managed and OnDemand flags.
// (It is up to the caller to set those.) It staples OCSP.
func (cfg Config) makeCertificateFromDiskWithOCSP(ctx context.Context, certFile, keyFile string) (Certificate, error) {
certPEMBlock, err := os.ReadFile(certFile)
if err != nil {
return Certificate{}, err
}
keyPEMBlock, err := os.ReadFile(keyFile)
if err != nil {
return Certificate{}, err
}
return cfg.makeCertificateWithOCSP(ctx, certPEMBlock, keyPEMBlock)
}
// makeCertificateWithOCSP is the same as makeCertificate except that it also
// staples OCSP to the certificate.
func (cfg Config) makeCertificateWithOCSP(ctx context.Context, certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
cert, err := makeCertificate(certPEMBlock, keyPEMBlock)
if err != nil {
return cert, err
}
if !cfg.OCSP.DisableStapling {
err = stapleOCSP(ctx, cfg.OCSP, cfg.cachedStorage(), &cert, certPEMBlock)
if errors.Is(err, ErrNoOCSPServerSpecified) {
cfg.Logger.Debug("stapling OCSP", zap.Error(err), zap.Strings("identifiers", cert.Names))
} else if err != nil {
cfg.Logger.Warn("stapling OCSP", zap.Error(err), zap.Strings("identifiers", cert.Names))
}
}
return cert, nil
}
// makeCertificate turns a certificate PEM bundle and a key PEM block into
// a Certificate with necessary metadata from parsing its bytes filled into
// its struct fields for convenience (except for the OnDemand and Managed
// flags; it is up to the caller to set those properties!). This function
// does NOT staple OCSP.
func makeCertificate(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
var cert Certificate
// Convert to a tls.Certificate
tlsCert, err := tls.X509KeyPair(certPEMBlock, keyPEMBlock)
if err != nil {
return cert, err
}
// Extract necessary metadata
err = fillCertFromLeaf(&cert, tlsCert)
if err != nil {
return cert, err
}
return cert, nil
}
// fillCertFromLeaf populates cert from tlsCert. If it succeeds, it
// guarantees that cert.Leaf is non-nil.
func fillCertFromLeaf(cert *Certificate, tlsCert tls.Certificate) error {
if len(tlsCert.Certificate) == 0 {
return fmt.Errorf("certificate is empty")
}
cert.Certificate = tlsCert
// the leaf cert should be the one for the site; we must set
// the tls.Certificate.Leaf field so that TLS handshakes are
// more efficient
leaf := cert.Certificate.Leaf
if leaf == nil {
var err error
leaf, err = x509.ParseCertificate(tlsCert.Certificate[0])
if err != nil {
return err
}
cert.Certificate.Leaf = leaf
}
// for convenience, we do want to assemble all the
// subjects on the certificate into one list
if leaf.Subject.CommonName != "" { // TODO: CommonName is deprecated
cert.Names = []string{strings.ToLower(leaf.Subject.CommonName)}
}
for _, name := range leaf.DNSNames {
if name != leaf.Subject.CommonName { // TODO: CommonName is deprecated
cert.Names = append(cert.Names, strings.ToLower(name))
}
}
for _, ip := range leaf.IPAddresses {
if ipStr := ip.String(); ipStr != leaf.Subject.CommonName { // TODO: CommonName is deprecated
cert.Names = append(cert.Names, strings.ToLower(ipStr))
}
}
for _, email := range leaf.EmailAddresses {
if email != leaf.Subject.CommonName { // TODO: CommonName is deprecated
cert.Names = append(cert.Names, strings.ToLower(email))
}
}
for _, u := range leaf.URIs {
if u.String() != leaf.Subject.CommonName { // TODO: CommonName is deprecated
cert.Names = append(cert.Names, u.String())
}
}
if len(cert.Names) == 0 {
return fmt.Errorf("certificate has no names")
}
cert.hash = hashCertificateChain(cert.Certificate.Certificate)
return nil
}
// managedCertInStorageNeedsRenewal returns true if cert (being a
// managed certificate) is expiring soon (according to cfg) or if
// ACME Renewal Information (ARI) is available and says that it is
// time to renew (it uses existing ARI; it does not update it).
// It returns false if there was an error, the cert is not expiring
// soon, and ARI window is still future. A certificate that is expiring
// soon in our cache but is not expiring soon in storage probably
// means that another instance renewed the certificate in the
// meantime, and it would be a good idea to simply load the cert
// into our cache rather than repeating the renewal process again.
func (cfg *Config) managedCertInStorageNeedsRenewal(ctx context.Context, cert Certificate) (bool, error) {
// this decides whether we renew, so it must observe what the rest of
// the cluster sees, not a possibly-stale local cache
certRes, err := cfg.loadCertResourceAnyIssuer(ctx, cert.Names[0], cfg.groundTruthStorage())
if err != nil {
return false, err
}
_, _, needsRenew := cfg.managedCertNeedsRenewal(certRes, false)
return needsRenew, nil
}
// reloadManagedCertificate reloads the certificate corresponding to the name(s)
// on oldCert into the cache, from storage. This also replaces the old certificate
// with the new one, so that all configurations that used the old cert now point
// to the new cert. It assumes that the new certificate for oldCert.Names[0] is
// already in storage. It returns the newly-loaded certificate if successful.
func (cfg *Config) reloadManagedCertificate(ctx context.Context, oldCert Certificate) (Certificate, error) {
cfg.Logger.Info("reloading managed certificate", zap.Strings("identifiers", oldCert.Names))
// the point of reloading is usually to pick up a renewal from another
// instance, so read storage rather than the local cache
newCert, err := cfg.loadManagedCertificate(ctx, oldCert.Names[0], cfg.groundTruthStorage())
if err != nil {
return Certificate{}, fmt.Errorf("loading managed certificate for %v from storage: %v", oldCert.Names, err)
}
cfg.certCache.replaceCertificate(oldCert, newCert)
return newCert, nil
}
// SubjectQualifiesForCert returns true if subj is a name which,
// as a quick sanity check, looks like it could be the subject
// of a certificate. Requirements are:
// - must not be empty
// - must not start or end with a dot (RFC 1034; RFC 6066 section 3)
// - must not contain common accidental special characters
func SubjectQualifiesForCert(subj string) bool {
// must not be empty
return strings.TrimSpace(subj) != "" &&
// must not start or end with a dot
!strings.HasPrefix(subj, ".") &&
!strings.HasSuffix(subj, ".") &&
// if it has a wildcard, must be a left-most label (or exactly "*"
// which won't be trusted by browsers but still technically works)
(!strings.Contains(subj, "*") || strings.HasPrefix(subj, "*.") || subj == "*") &&
// must not contain other common special characters
!strings.ContainsAny(subj, "()[]{}<> \t\n\"\\!@#$%^&|;'+=")
}
// SubjectQualifiesForPublicCert returns true if the subject
// name appears eligible for automagic TLS with a public
// CA such as Let's Encrypt. For example: internal IP addresses
// and localhost are not eligible because we cannot obtain certs
// for those names with a public CA. Wildcard names are
// allowed, as long as they conform to CABF requirements (only
// one wildcard label, and it must be the left-most label).
func SubjectQualifiesForPublicCert(subj string) bool {
// must at least qualify for a certificate
return SubjectQualifiesForCert(subj) &&
// loopback hosts and internal IPs are ineligible
!SubjectIsInternal(subj) &&
// only one wildcard label allowed, and it must be left-most, with 3+ labels
(!strings.Contains(subj, "*") ||
(strings.Count(subj, "*") == 1 &&
strings.Count(subj, ".") > 1 &&
len(subj) > 2 &&
strings.HasPrefix(subj, "*.")))
}
// SubjectIsIP returns true if subj is an IP address.
func SubjectIsIP(subj string) bool {
return net.ParseIP(subj) != nil
}
// SubjectIsInternal returns true if subj is an internal-facing
// hostname or address, including localhost/loopback hosts.
// Ports are ignored, if present.
func SubjectIsInternal(subj string) bool {
subj = strings.ToLower(strings.TrimSuffix(hostOnly(subj), "."))
return subj == "localhost" ||
strings.HasSuffix(subj, ".localhost") ||
strings.HasSuffix(subj, ".local") ||
strings.HasSuffix(subj, ".internal") ||
strings.HasSuffix(subj, ".home.arpa") ||
isInternalIP(subj)
}
// isInternalIP returns true if the IP of addr
// belongs to a private network IP range. addr
// must only be an IP or an IP:port combination.
func isInternalIP(addr string) bool {
privateNetworks := []string{
"127.0.0.0/8", // IPv4 loopback
"0.0.0.0/16",
"10.0.0.0/8", // RFC1918
"172.16.0.0/12", // RFC1918
"192.168.0.0/16", // RFC1918
"169.254.0.0/16", // RFC3927 link-local
"::1/7", // IPv6 loopback
"fe80::/10", // IPv6 link-local
"fc00::/7", // IPv6 unique local addr
}
host := hostOnly(addr)
ip := net.ParseIP(host)
if ip == nil {
return false
}
for _, privateNetwork := range privateNetworks {
_, ipnet, _ := net.ParseCIDR(privateNetwork)
if ipnet.Contains(ip) {
return true
}
}
return false
}
// hostOnly returns only the host portion of hostport.
// If there is no port or if there is an error splitting
// the port off, the whole input string is returned.
func hostOnly(hostport string) string {
host, _, err := net.SplitHostPort(hostport)
if err != nil {
// May be a bare IPv6 address in brackets without a port (e.g. "[::1]").
// net.SplitHostPort requires a port when brackets are present, so strip them.
if len(hostport) > 1 && hostport[0] == '[' && hostport[len(hostport)-1] == ']' {
return hostport[1 : len(hostport)-1]
}
return hostport // OK; probably had no port to begin with
}
return host
}
// MatchWildcard returns true if subject (a candidate DNS name)
// matches wildcard (a reference DNS name), mostly according to
// RFC 6125-compliant wildcard rules. See also RFC 2818 which
// states that IP addresses must match exactly, but this function
// does not attempt to distinguish IP addresses from internal or
// external DNS names that happen to look like IP addresses.
// It uses DNS wildcard matching logic and is case-insensitive.
// https://tools.ietf.org/html/rfc2818#section-3.1
func MatchWildcard(subject, wildcard string) bool {
// Strip brackets from IPv6 addresses (e.g. "[::1]" from HTTP Host headers).
subject = hostOnly(subject)
subject, wildcard = strings.ToLower(subject), strings.ToLower(wildcard)
if subject == wildcard {
return true
}
if !strings.Contains(wildcard, "*") {
return false
}
labels := strings.Split(subject, ".")
for i := range labels {
if labels[i] == "" {
continue // invalid label
}
labels[i] = "*"
candidate := strings.Join(labels, ".")
if candidate == wildcard {
return true
}
}
return false
}