Fix TOFU

client.go

@@ -213,27 +213,27 @@ func (c *Client) verifyConnection(req *Request, cs tls.ConnectionState) error {
 	if c.InsecureSkipTrust {
 		return nil
 	}
+
 	// Check the known hosts
-	// No need to check if it is expired as tls already does that
 	knownHost, ok := c.KnownHosts.Lookup(hostname)
-	if ok {
-		fingerprint := NewFingerprint(cert)
-		if knownHost.Hex != fingerprint.Hex {
-			return errors.New("gemini: fingerprint does not match")
+	if !ok || time.Now().Unix() >= knownHost.Expires {
+		// See if the client trusts the certificate
+		if c.TrustCertificate != nil {
+			switch c.TrustCertificate(hostname, cert) {
+			case TrustOnce:
+				c.KnownHosts.AddTemporary(hostname, cert)
+				return nil
+			case TrustAlways:
+				c.KnownHosts.Add(hostname, cert)
+				return nil
+			}
 		}
-		return nil
+		return errors.New("gemini: certificate not trusted")
 	}
 
-	// See if the client trusts the certificate
-	if c.TrustCertificate != nil {
-		switch c.TrustCertificate(hostname, cert) {
-		case TrustOnce:
-			c.KnownHosts.AddTemporary(hostname, cert)
-			return nil
-		case TrustAlways:
-			c.KnownHosts.Add(hostname, cert)
-			return nil
-		}
+	fingerprint := NewFingerprint(cert)
+	if knownHost.Hex == fingerprint.Hex {
+		return nil
 	}
-	return errors.New("gemini: certificate not trusted")
+	return errors.New("gemini: fingerprint does not match")
 }

server.go

@@ -156,7 +156,7 @@ func (s *Server) getCertificateFor(hostname string) (*tls.Certificate, error) {
 
 	// Generate a new certificate if it is missing or expired
 	cert, ok := s.Certificates.Lookup(hostname)
-	if !ok || cert.Leaf != nil && !time.Now().After(cert.Leaf.NotAfter) {
+	if !ok || cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) {
 		if s.CreateCertificate != nil {
 			cert, err := s.CreateCertificate(hostname)
 			if err == nil {

tofu.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 )
 
@@ -105,7 +106,7 @@ func (k *KnownHosts) Parse(r io.Reader) {
 	for scanner.Scan() {
 		text := scanner.Text()
 		parts := strings.Split(text, " ")
-		if len(parts) < 3 {
+		if len(parts) < 4 {
 			continue
 		}
 
@@ -116,9 +117,15 @@ func (k *KnownHosts) Parse(r io.Reader) {
 		}
 		fingerprint := parts[2]
 
+		expires, err := strconv.ParseInt(parts[3], 10, 0)
+		if err != nil {
+			continue
+		}
+
 		k.hosts[hostname] = Fingerprint{
 			Algorithm: algorithm,
 			Hex:       fingerprint,
+			Expires:   expires,
 		}
 	}
 }
@@ -131,13 +138,14 @@ func (k *KnownHosts) Write(w io.Writer) {
 }
 
 func appendKnownHost(w io.Writer, hostname string, f Fingerprint) (int, error) {
-	return fmt.Fprintf(w, "%s %s %s\n", hostname, f.Algorithm, f.Hex)
+	return fmt.Fprintf(w, "%s %s %s %d\n", hostname, f.Algorithm, f.Hex, f.Expires)
 }
 
 // Fingerprint represents a fingerprint using a certain algorithm.
 type Fingerprint struct {
 	Algorithm string // fingerprint algorithm e.g. SHA-512
 	Hex       string // fingerprint in hexadecimal, with ':' between each octet
+	Expires   int64  // unix time of the fingerprint expiration date
 }
 
 // NewFingerprint returns the SHA-512 fingerprint of the provided certificate.
@@ -153,6 +161,7 @@ func NewFingerprint(cert *x509.Certificate) Fingerprint {
 	return Fingerprint{
 		Algorithm: "SHA-512",
 		Hex:       b.String(),
+		Expires:   cert.NotAfter.Unix(),
 	}
 }