Move certificate verification code to VerifyConnection

cert.go

@@ -41,11 +41,11 @@ func (c *CertificateStore) Add(hostname string, cert tls.Certificate) {
 func (c *CertificateStore) Lookup(hostname string) (*tls.Certificate, error) {
 	cert, ok := c.store[hostname]
 	if !ok {
-		return nil, ErrUnknownCertificate
+		return nil, ErrCertificateUnknown
 	}
 	// Ensure that the certificate is not expired
 	if cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) {
-		return &cert, ErrInvalidCertificate
+		return &cert, ErrCertificateExpired
 	}
 	return &cert, nil
 }

client.go

@@ -9,15 +9,13 @@ import (
 	"net"
 	"net/url"
 	"strconv"
-	"time"
 )
 
 // Client errors.
 var (
 	ErrInvalidURL            = errors.New("gemini: invalid URL")
 	ErrInvalidResponse       = errors.New("gemini: invalid response")
-	ErrInvalidCertificate    = errors.New("gemini: invalid certificate")
-	ErrUnknownCertificate    = errors.New("gemini: unknown certificate")
+	ErrCertificateUnknown    = errors.New("gemini: unknown certificate")
 	ErrCertificateNotTrusted = errors.New("gemini: certificate is not trusted")
 )
 
@@ -221,18 +219,9 @@ func (c *Client) Send(req *Request) (*Response, error) {
 			}
 			return &tls.Certificate{}, nil
 		},
-		VerifyPeerCertificate: func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
-			// Parse the certificate
-			cert, err := x509.ParseCertificate(rawCerts[0])
-			if err != nil {
-				return err
-			}
-			// Validate the certificate
-			if !validCertificate(cert) {
-				return ErrInvalidCertificate
-			}
-			// Check that the certificate is valid for the hostname
-			// Use our own implementation of verifyHostname
+		VerifyConnection: func(cs tls.ConnectionState) error {
+			cert := cs.PeerCertificates[0]
+			// Verify the hostname
 			if err := verifyHostname(cert, hostname(req.Host)); err != nil {
 				return err
 			}
@@ -285,17 +274,3 @@ func (c *Client) Send(req *Request) (*Response, error) {
 	}
 	return resp, nil
 }
-
-// validCertificate determines whether cert is a valid certificate
-func validCertificate(cert *x509.Certificate) bool {
-	// Check notBefore and notAfter
-	now := time.Now()
-	if cert.NotBefore.After(now) {
-		return false
-	}
-	if cert.NotAfter.Before(now) {
-		return false
-	}
-	// No need to check hash algorithms, hopefully tls has checked for us already
-	return true
-}

examples/client.go

@@ -29,7 +29,7 @@ func init() {
 				// Alert the user that the certificate is not trusted
 				fmt.Printf("Warning: Certificate for %s is not trusted!\n", hostname)
 				fmt.Println("This could indicate a Man-in-the-Middle attack.")
-			case gmi.ErrUnknownCertificate:
+			case gmi.ErrCertificateUnknown:
 				// Prompt the user to trust the certificate
 				trust := trustCertificate(cert)
 				switch trust {

examples/server.go

@@ -19,7 +19,7 @@ func main() {
 		cert, err := store.Lookup(hostname)
 		if err != nil {
 			switch err {
-			case gmi.ErrInvalidCertificate:
+			case gmi.ErrCertificateExpired:
 				log.Print("Old certificate expired, creating new one")
 				// Generate a new certificate if the old one is expired.
 				crt, key, err := gmi.NewRawCertificate(hostname, time.Minute)

server.go

@@ -18,7 +18,8 @@ import (
 
 // Server errors.
 var (
-	ErrBodyNotAllowed = errors.New("gemini: response status code does not allow for body")
+	ErrBodyNotAllowed     = errors.New("gemini: response status code does not allow for body")
+	ErrCertificateExpired = errors.New("gemini: certificate expired")
 )
 
 // Server is a Gemini server.
@@ -92,15 +93,14 @@ func (s *Server) ListenAndServe() error {
 	defer ln.Close()
 
 	config := &tls.Config{
-		InsecureSkipVerify: true,
-		MinVersion:         tls.VersionTLS12,
+		ClientAuth: tls.RequestClientCert,
+		MinVersion: tls.VersionTLS12,
 		GetCertificate: func(h *tls.ClientHelloInfo) (*tls.Certificate, error) {
 			if s.GetCertificate != nil {
 				return s.GetCertificate(h.ServerName, &s.CertificateStore), nil
 			}
 			return s.CertificateStore.Lookup(h.ServerName)
 		},
-		ClientAuth: tls.RequestClientCert,
 	}
 	tlsListener := tls.NewListener(ln, config)
 	return s.Serve(tlsListener)

tofu.go

@@ -7,7 +7,6 @@ import (
 	"crypto/x509"
 	"fmt"
 	"io"
-	"log"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -93,7 +92,6 @@ func (k *KnownHosts) Lookup(hostname string, cert *x509.Certificate) error {
 			// Certificate is expired
 			continue
 		}
-		log.Print(k.hosts[i].Expires, now)
 		if k.hosts[i].Fingerprint == fingerprint {
 			// Fingerprint matches
 			return nil
@@ -101,7 +99,7 @@ func (k *KnownHosts) Lookup(hostname string, cert *x509.Certificate) error {
 		// Fingerprint does not match
 		return ErrCertificateNotTrusted
 	}
-	return ErrUnknownCertificate
+	return ErrCertificateUnknown
 }
 
 // Parse parses the provided reader and adds the parsed known hosts to the list.

vendor.go

@@ -10,37 +10,22 @@ package gmi
 
 import (
 	"crypto/x509"
-	"crypto/x509/pkix"
-	"encoding/asn1"
 	"net"
 	"strings"
 	"unicode/utf8"
 )
 
-var (
-	oidExtensionSubjectAltName = []int{2, 5, 29, 17}
-)
+var oidExtensionSubjectAltName = []int{2, 5, 29, 17}
 
-// oidNotInExtensions reports whether an extension with the given oid exists in
-// extensions.
-func oidInExtensions(oid asn1.ObjectIdentifier, extensions []pkix.Extension) bool {
-	for _, e := range extensions {
-		if e.Id.Equal(oid) {
+func hasSANExtension(c *x509.Certificate) bool {
+	for _, e := range c.Extensions {
+		if e.Id.Equal(oidExtensionSubjectAltName) {
 			return true
 		}
 	}
 	return false
 }
 
-func hasSANExtension(c *x509.Certificate) bool {
-	return oidInExtensions(oidExtensionSubjectAltName, c.Extensions)
-}
-
-// ignoreCN disables interpreting Common Name as a hostname. See issue 24151.
-// NOTE: This is set to false so that certificates with common names will still
-// be supported.
-var ignoreCN = false
-
 func validHostnamePattern(host string) bool { return validHostname(host, true) }
 func validHostnameInput(host string) bool   { return validHostname(host, false) }
 
@@ -100,7 +85,7 @@ func validHostname(host string, isPattern bool) bool {
 // constraints if there is no risk the CN would be matched as a hostname.
 // See NameConstraintsWithoutSANs and issue 24151.
 func commonNameAsHostname(c *x509.Certificate) bool {
-	return !ignoreCN && !hasSANExtension(c) && validHostnamePattern(c.Subject.CommonName)
+	return !hasSANExtension(c) && validHostnamePattern(c.Subject.CommonName)
 }
 
 func matchExactly(hostA, hostB string) bool {