99 lines
2.7 KiB
Go
99 lines
2.7 KiB
Go
package client
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import (
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"crypto/sha256"
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"crypto/x509"
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"errors"
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"fmt"
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"strings"
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"time"
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"github.com/makeworld-the-better-one/amfora/config"
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)
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// TOFU implementation.
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// Stores cert hash and expiry for now, like Bombadillo.
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// There is ongoing TOFU discussiong on the mailing list about better
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// ways to do this, and I will update this file once those are decided on.
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var ErrTofu = errors.New("server cert does not match TOFU database")
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var tofuStore = config.TofuStore
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// idKey returns the config/viper key needed to retrieve
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// a cert's ID / fingerprint.
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func idKey(domain string) string {
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return strings.ReplaceAll(domain, ".", "/")
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}
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func expiryKey(domain string) string {
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return strings.ReplaceAll(strings.TrimSuffix(domain, "."), ".", "/") + "/expiry"
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}
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func loadTofuEntry(domain string) (string, time.Time, error) {
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id := tofuStore.GetString(idKey(domain)) // Fingerprint
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if len(id) != 64 {
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// Not set, or invalid
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return "", time.Time{}, errors.New("not found")
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}
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expiry := tofuStore.GetTime(expiryKey(domain))
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if expiry.IsZero() {
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// Not set
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return id, time.Time{}, errors.New("not found")
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}
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return id, expiry, nil
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}
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// certID returns a generic string representing a cert or domain.
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func certID(cert *x509.Certificate) string {
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h := sha256.New()
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h.Write(cert.Raw)
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return fmt.Sprintf("%X", h.Sum(nil))
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// The old way that uses the cert public key:
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// b, err := x509.MarshalPKIXPublicKey(cert.PublicKey)
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// h := sha256.New()
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// if err != nil {
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// // Unsupported key type - try to store a hash of the struct instead
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// h.Write([]byte(fmt.Sprint(cert.PublicKey)))
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// return fmt.Sprintf("%X", h.Sum(nil))
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// }
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// h.Write(b)
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// return fmt.Sprintf("%X", h.Sum(nil))
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}
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func saveTofuEntry(cert *x509.Certificate) {
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tofuStore.Set(idKey(cert.Subject.CommonName), certID(cert))
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tofuStore.Set(expiryKey(cert.Subject.CommonName), cert.NotAfter.UTC())
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err := tofuStore.WriteConfig()
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if err != nil {
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panic(err)
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}
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}
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// handleTofu is the abstracted interface for taking care of TOFU.
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// A cert is provided and storage, checking, etc, are taken care of.
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// It returns a bool indicating if the cert is valid according to
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// the TOFU database.
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// If false is returned, the connection should not go ahead.
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func handleTofu(cert *x509.Certificate) bool {
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id, expiry, err := loadTofuEntry(cert.Subject.CommonName)
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if err != nil {
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// Cert isn't in database or data is malformed
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// So it can't be checked and anything is valid
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saveTofuEntry(cert)
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return true
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}
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if certID(cert) == id {
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// Save cert as the one stored
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return true
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}
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if time.Now().After(expiry) {
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// Old cert expired, so anything is valid
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saveTofuEntry(cert)
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return true
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}
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return false
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}
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