Fix TOFU

cert.go

@@ -2,12 +2,14 @@ package gemini
 
 import (
 	"crypto"
+	"crypto/ecdsa"
 	"crypto/ed25519"
+	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/tls"
 	"crypto/x509"
+	"crypto/x509/pkix"
 	"encoding/pem"
-	"log"
 	"math/big"
 	"net"
 	"os"
@@ -26,7 +28,7 @@ type CertificateStore struct {
 
 // Add adds a certificate for the given scope to the store.
 // It tries to parse the certificate if it is not already parsed.
-func (c *CertificateStore) Add(scope string, cert tls.Certificate) {
+func (c *CertificateStore) Add(scope string, cert tls.Certificate) error {
 	if c.store == nil {
 		c.store = map[string]tls.Certificate{}
 	}
@@ -39,27 +41,20 @@ func (c *CertificateStore) Add(scope string, cert tls.Certificate) {
 	}
 	if c.dir {
 		// Write certificates
-		log.Printf("gemini: Writing certificate for %s to %s", scope, c.path)
 		certPath := filepath.Join(c.path, scope+".crt")
 		keyPath := filepath.Join(c.path, scope+".key")
 		if err := WriteCertificate(cert, certPath, keyPath); err != nil {
-			log.Printf("gemini: Failed to write certificate for %s: %s", scope, err)
+			return err
 		}
 	}
 	c.store[scope] = cert
+	return nil
 }
 
 // Lookup returns the certificate for the given scope.
-func (c *CertificateStore) Lookup(scope string) (*tls.Certificate, error) {
+func (c *CertificateStore) Lookup(scope string) (tls.Certificate, bool) {
 	cert, ok := c.store[scope]
-	if !ok {
-		return nil, ErrCertificateNotFound
-	}
-	// Ensure that the certificate is not expired
-	if cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) {
-		return &cert, ErrCertificateExpired
-	}
-	return &cert, nil
+	return cert, ok
 }
 
 // Load loads certificates from the given path.
@@ -87,11 +82,31 @@ func (c *CertificateStore) Load(path string) error {
 	return nil
 }
 
-// CertificateOptions configures how a certificate is created.
+// CertificateOptions configures the creation of a certificate.
 type CertificateOptions struct {
+	// Subject Alternate Name values.
+	// Should contain the IP addresses that the certificate is valid for.
 	IPAddresses []net.IP
-	DNSNames    []string
-	Duration    time.Duration
+
+	// Subject Alternate Name values.
+	// Should contain the DNS names that this certificate is valid for.
+	// E.g. example.com, *.example.com
+	DNSNames []string
+
+	// Subject specifies the certificate Subject.
+	//
+	// Subject.CommonName can contain the DNS name that this certificate
+	// is valid for. Server certificates should specify both a Subject
+	// and a Subject Alternate Name.
+	Subject pkix.Name
+
+	// Duration specifies the amount of time that the certificate is valid for.
+	Duration time.Duration
+
+	// Ed25519 specifies whether to generate an Ed25519 key pair.
+	// If false, an ECDSA key will be generated instead.
+	// Ed25519 is not as widely supported as ECDSA.
+	Ed25519 bool
 }
 
 // CreateCertificate creates a new TLS certificate.
@@ -109,15 +124,27 @@ func CreateCertificate(options CertificateOptions) (tls.Certificate, error) {
 
 // newX509KeyPair creates and returns a new certificate and private key.
 func newX509KeyPair(options CertificateOptions) (*x509.Certificate, crypto.PrivateKey, error) {
-	// Generate an ED25519 private key
-	_, priv, err := ed25519.GenerateKey(rand.Reader)
-	if err != nil {
-		return nil, nil, err
+	var pub crypto.PublicKey
+	var priv crypto.PrivateKey
+	if options.Ed25519 {
+		// Generate an Ed25519 private key
+		var err error
+		pub, priv, err = ed25519.GenerateKey(rand.Reader)
+		if err != nil {
+			return nil, nil, err
+		}
+	} else {
+		// Generate an ECDSA private key
+		private, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+		if err != nil {
+			return nil, nil, err
+		}
+		priv = private
+		pub = &private.PublicKey
 	}
-	public := priv.Public()
 
-	// ED25519 keys should have the DigitalSignature KeyUsage bits set
-	// in the x509.Certificate template
+	// ECDSA and Ed25519 keys should have the DigitalSignature KeyUsage bits
+	// set in the x509.Certificate template
 	keyUsage := x509.KeyUsageDigitalSignature
 
 	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
@@ -138,9 +165,10 @@ func newX509KeyPair(options CertificateOptions) (*x509.Certificate, crypto.Priva
 		BasicConstraintsValid: true,
 		IPAddresses:           options.IPAddresses,
 		DNSNames:              options.DNSNames,
+		Subject:               options.Subject,
 	}
 
-	crt, err := x509.CreateCertificate(rand.Reader, &template, &template, public, priv)
+	crt, err := x509.CreateCertificate(rand.Reader, &template, &template, pub, priv)
 	if err != nil {
 		return nil, nil, err
 	}

client.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"crypto/tls"
 	"crypto/x509"
+	"errors"
 	"net"
 	"net/url"
 	"path"
@@ -39,8 +40,7 @@ type Client struct {
 	GetInput func(prompt string, sensitive bool) (input string, ok bool)
 
 	// CheckRedirect determines whether to follow a redirect.
-	// If CheckRedirect is nil, a default policy of no more than 5 consecutive
-	// redirects will be enforced.
+	// If CheckRedirect is nil, redirects will not be followed.
 	CheckRedirect func(req *Request, via []*Request) error
 
 	// CreateCertificate is called to generate a certificate upon
@@ -125,9 +125,10 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 				return resp, err
 			}
 			c.Certificates.Add(hostname+path, cert)
+			req.Certificate = &cert
 			return c.do(req, via)
 		}
-		return resp, ErrCertificateRequired
+		return resp, nil
 
 	case resp.Status.Class() == StatusClassInput:
 		if c.GetInput != nil {
@@ -138,7 +139,7 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 				return c.do(req, via)
 			}
 		}
-		return resp, ErrInputRequired
+		return resp, nil
 
 	case resp.Status.Class() == StatusClassRedirect:
 		if via == nil {
@@ -150,21 +151,19 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 		if err != nil {
 			return resp, err
 		}
+
 		target = req.URL.ResolveReference(target)
-		redirect, err := NewRequestFromURL(target)
-		if err != nil {
-			return resp, err
+		if target.Scheme != "" && target.Scheme != "gemini" {
+			return resp, nil
 		}
 
+		redirect := NewRequestFromURL(target)
 		if c.CheckRedirect != nil {
 			if err := c.CheckRedirect(redirect, via); err != nil {
 				return resp, err
 			}
-		} else if len(via) > 5 {
-			// Default policy of no more than 5 redirects
-			return resp, ErrTooManyRedirects
+			return c.do(redirect, via)
 		}
-		return c.do(redirect, via)
 	}
 
 	resp.Request = req
@@ -180,11 +179,14 @@ func (c *Client) getClientCertificate(req *Request) (*tls.Certificate, error) {
 	// Search recursively for the certificate
 	scope := req.URL.Hostname() + strings.TrimSuffix(req.URL.Path, "/")
 	for {
-		cert, err := c.Certificates.Lookup(scope)
-		if err == nil {
-			return cert, err
-		}
-		if err == ErrCertificateExpired {
+		cert, ok := c.Certificates.Lookup(scope)
+		if ok {
+			// Ensure that the certificate is not expired
+			if cert.Leaf != nil && !time.Now().After(cert.Leaf.NotAfter) {
+				// Store the certificate
+				req.Certificate = &cert
+				return &cert, nil
+			}
 			break
 		}
 		scope = path.Dir(scope)
@@ -211,10 +213,10 @@ func (c *Client) verifyConnection(req *Request, cs tls.ConnectionState) error {
 	if c.InsecureSkipTrust {
 		return nil
 	}
+
 	// Check the known hosts
-	err := c.KnownHosts.Lookup(hostname, cert)
-	switch err {
-	case ErrCertificateExpired, ErrCertificateNotFound:
+	knownHost, ok := c.KnownHosts.Lookup(hostname)
+	if !ok || time.Now().Unix() >= knownHost.Expires {
 		// See if the client trusts the certificate
 		if c.TrustCertificate != nil {
 			switch c.TrustCertificate(hostname, cert) {
@@ -226,7 +228,12 @@ func (c *Client) verifyConnection(req *Request, cs tls.ConnectionState) error {
 				return nil
 			}
 		}
-		return ErrCertificateNotTrusted
+		return errors.New("gemini: certificate not trusted")
 	}
-	return err
+
+	fingerprint := NewFingerprint(cert)
+	if knownHost.Hex == fingerprint.Hex {
+		return nil
+	}
+	return errors.New("gemini: fingerprint does not match")
 }

examples/auth.go

@@ -3,9 +3,12 @@
 package main
 
 import (
+	"crypto/tls"
 	"crypto/x509"
+	"crypto/x509/pkix"
 	"fmt"
 	"log"
+	"time"
 
 	"git.sr.ht/~adnano/go-gemini"
 )
@@ -44,6 +47,15 @@ func main() {
 	if err := server.Certificates.Load("/var/lib/gemini/certs"); err != nil {
 		log.Fatal(err)
 	}
+	server.CreateCertificate = func(hostname string) (tls.Certificate, error) {
+		return gemini.CreateCertificate(gemini.CertificateOptions{
+			Subject: pkix.Name{
+				CommonName: hostname,
+			},
+			DNSNames: []string{hostname},
+			Duration: time.Hour,
+		})
+	}
 	server.Register("localhost", &mux)
 
 	if err := server.ListenAndServe(); err != nil {
@@ -51,41 +63,43 @@ func main() {
 	}
 }
 
-func getSession(crt *x509.Certificate) (*session, bool) {
-	fingerprint := gemini.Fingerprint(crt)
-	session, ok := sessions[fingerprint]
+func getSession(cert *x509.Certificate) (*session, bool) {
+	fingerprint := gemini.NewFingerprint(cert)
+	session, ok := sessions[fingerprint.Hex]
 	return session, ok
 }
 
 func login(w *gemini.ResponseWriter, r *gemini.Request) {
-	cert, ok := gemini.Certificate(w, r)
-	if !ok {
+	if r.Certificate == nil {
+		w.WriteStatus(gemini.StatusCertificateRequired)
 		return
 	}
-	username, ok := gemini.Input(w, r, "Username")
+	username, ok := gemini.Input(r)
 	if !ok {
+		w.WriteHeader(gemini.StatusInput, "Username")
 		return
 	}
-	fingerprint := gemini.Fingerprint(cert)
-	sessions[fingerprint] = &session{
+	fingerprint := gemini.NewFingerprint(r.Certificate.Leaf)
+	sessions[fingerprint.Hex] = &session{
 		username: username,
 	}
 	w.WriteHeader(gemini.StatusRedirect, "/password")
 }
 
 func loginPassword(w *gemini.ResponseWriter, r *gemini.Request) {
-	cert, ok := gemini.Certificate(w, r)
-	if !ok {
+	if r.Certificate == nil {
+		w.WriteStatus(gemini.StatusCertificateRequired)
 		return
 	}
-	session, ok := getSession(cert)
+	session, ok := getSession(r.Certificate.Leaf)
 	if !ok {
 		w.WriteStatus(gemini.StatusCertificateNotAuthorized)
 		return
 	}
 
-	password, ok := gemini.SensitiveInput(w, r, "Password")
+	password, ok := gemini.Input(r)
 	if !ok {
+		w.WriteHeader(gemini.StatusSensitiveInput, "Password")
 		return
 	}
 	expected := logins[session.username].password
@@ -93,26 +107,27 @@ func loginPassword(w *gemini.ResponseWriter, r *gemini.Request) {
 		session.authorized = true
 		w.WriteHeader(gemini.StatusRedirect, "/profile")
 	} else {
-		gemini.SensitiveInput(w, r, "Wrong password. Try again")
+		w.WriteHeader(gemini.StatusSensitiveInput, "Password")
 	}
 }
 
 func logout(w *gemini.ResponseWriter, r *gemini.Request) {
-	cert, ok := gemini.Certificate(w, r)
-	if !ok {
+	if r.Certificate == nil {
+		w.WriteStatus(gemini.StatusCertificateRequired)
 		return
 	}
-	fingerprint := gemini.Fingerprint(cert)
-	delete(sessions, fingerprint)
+	fingerprint := gemini.NewFingerprint(r.Certificate.Leaf)
+	delete(sessions, fingerprint.Hex)
 	fmt.Fprintln(w, "Successfully logged out.")
+	fmt.Fprintln(w, "=> / Index")
 }
 
 func profile(w *gemini.ResponseWriter, r *gemini.Request) {
-	cert, ok := gemini.Certificate(w, r)
-	if !ok {
+	if r.Certificate == nil {
+		w.WriteStatus(gemini.StatusCertificateRequired)
 		return
 	}
-	session, ok := getSession(cert)
+	session, ok := getSession(r.Certificate.Leaf)
 	if !ok {
 		w.WriteStatus(gemini.StatusCertificateNotAuthorized)
 		return
@@ -124,11 +139,11 @@ func profile(w *gemini.ResponseWriter, r *gemini.Request) {
 }
 
 func admin(w *gemini.ResponseWriter, r *gemini.Request) {
-	cert, ok := gemini.Certificate(w, r)
-	if !ok {
+	if r.Certificate == nil {
+		w.WriteStatus(gemini.StatusCertificateRequired)
 		return
 	}
-	session, ok := getSession(cert)
+	session, ok := getSession(r.Certificate.Leaf)
 	if !ok {
 		w.WriteStatus(gemini.StatusCertificateNotAuthorized)
 		return

examples/cert.go

@@ -3,10 +3,7 @@
 package main
 
 import (
-	"bytes"
-	"crypto/tls"
-	"crypto/x509"
-	"encoding/pem"
+	"crypto/x509/pkix"
 	"fmt"
 	"log"
 	"os"
@@ -26,6 +23,9 @@ func main() {
 		log.Fatal(err)
 	}
 	options := gemini.CertificateOptions{
+		Subject: pkix.Name{
+			CommonName: host,
+		},
 		DNSNames: []string{host},
 		Duration: duration,
 	}
@@ -33,63 +33,9 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	if err := writeCertificate(host, cert); err != nil {
+	certPath := host + ".crt"
+	keyPath := host + ".key"
+	if err := gemini.WriteCertificate(cert, certPath, keyPath); err != nil {
 		log.Fatal(err)
 	}
 }
-
-// writeCertificate writes the provided certificate and private key
-// to path.crt and path.key respectively.
-func writeCertificate(path string, cert tls.Certificate) error {
-	crt, err := marshalX509Certificate(cert.Leaf.Raw)
-	if err != nil {
-		return err
-	}
-	key, err := marshalPrivateKey(cert.PrivateKey)
-	if err != nil {
-		return err
-	}
-
-	// Write the certificate
-	crtPath := path + ".crt"
-	crtOut, err := os.OpenFile(crtPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
-	if err != nil {
-		return err
-	}
-	if _, err := crtOut.Write(crt); err != nil {
-		return err
-	}
-
-	// Write the private key
-	keyPath := path + ".key"
-	keyOut, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
-	if err != nil {
-		return err
-	}
-	if _, err := keyOut.Write(key); err != nil {
-		return err
-	}
-	return nil
-}
-
-// marshalX509Certificate returns a PEM-encoded version of the given raw certificate.
-func marshalX509Certificate(cert []byte) ([]byte, error) {
-	var b bytes.Buffer
-	if err := pem.Encode(&b, &pem.Block{Type: "CERTIFICATE", Bytes: cert}); err != nil {
-		return nil, err
-	}
-	return b.Bytes(), nil
-}
-
-// marshalPrivateKey returns PEM encoded versions of the given certificate and private key.
-func marshalPrivateKey(priv interface{}) ([]byte, error) {
-	var b bytes.Buffer
-	privBytes, err := x509.MarshalPKCS8PrivateKey(priv)
-	if err != nil {
-		return nil, err
-	}
-	if err := pem.Encode(&b, &pem.Block{Type: "PRIVATE KEY", Bytes: privBytes}); err != nil {
-		return nil, err
-	}
-	return b.Bytes(), nil
-}

examples/client.go

@@ -30,10 +30,11 @@ var (
 )
 
 func init() {
-	client.Timeout = 2 * time.Minute
+	client.Timeout = 30 * time.Second
 	client.KnownHosts.LoadDefault()
 	client.TrustCertificate = func(hostname string, cert *x509.Certificate) gemini.Trust {
-		fmt.Printf(trustPrompt, hostname, gemini.Fingerprint(cert))
+		fingerprint := gemini.NewFingerprint(cert)
+		fmt.Printf(trustPrompt, hostname, fingerprint.Hex)
 		scanner.Scan()
 		switch scanner.Text() {
 		case "t":

examples/html.go

@@ -37,11 +37,10 @@ func textToHTML(text gemini.Text) string {
 			list = false
 			fmt.Fprint(&b, "</ul>\n")
 		}
-		switch l.(type) {
+		switch l := l.(type) {
 		case gemini.LineLink:
-			link := l.(gemini.LineLink)
-			url := html.EscapeString(link.URL)
-			name := html.EscapeString(link.Name)
+			url := html.EscapeString(l.URL)
+			name := html.EscapeString(l.Name)
 			if name == "" {
 				name = url
 			}
@@ -54,29 +53,22 @@ func textToHTML(text gemini.Text) string {
 				fmt.Fprint(&b, "</pre>\n")
 			}
 		case gemini.LinePreformattedText:
-			text := string(l.(gemini.LinePreformattedText))
-			fmt.Fprintf(&b, "%s\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "%s\n", html.EscapeString(string(l)))
 		case gemini.LineHeading1:
-			text := string(l.(gemini.LineHeading1))
-			fmt.Fprintf(&b, "<h1>%s</h1>\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "<h1>%s</h1>\n", html.EscapeString(string(l)))
 		case gemini.LineHeading2:
-			text := string(l.(gemini.LineHeading2))
-			fmt.Fprintf(&b, "<h2>%s</h2>\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "<h2>%s</h2>\n", html.EscapeString(string(l)))
 		case gemini.LineHeading3:
-			text := string(l.(gemini.LineHeading3))
-			fmt.Fprintf(&b, "<h3>%s</h3>\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "<h3>%s</h3>\n", html.EscapeString(string(l)))
 		case gemini.LineListItem:
-			text := string(l.(gemini.LineListItem))
-			fmt.Fprintf(&b, "<li>%s</li>\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "<li>%s</li>\n", html.EscapeString(string(l)))
 		case gemini.LineQuote:
-			text := string(l.(gemini.LineQuote))
-			fmt.Fprintf(&b, "<blockquote>%s</blockquote>\n", html.EscapeString(text))
+			fmt.Fprintf(&b, "<blockquote>%s</blockquote>\n", html.EscapeString(string(l)))
 		case gemini.LineText:
-			text := string(l.(gemini.LineText))
-			if text == "" {
+			if l == "" {
 				fmt.Fprint(&b, "<br>\n")
 			} else {
-				fmt.Fprintf(&b, "<p>%s</p>\n", html.EscapeString(text))
+				fmt.Fprintf(&b, "<p>%s</p>\n", html.EscapeString(string(l)))
 			}
 		}
 	}

examples/server.go

@@ -4,6 +4,7 @@ package main
 
 import (
 	"crypto/tls"
+	"crypto/x509/pkix"
 	"log"
 	"time"
 
@@ -12,13 +13,16 @@ import (
 
 func main() {
 	var server gemini.Server
-	server.ReadTimeout = 1 * time.Minute
-	server.WriteTimeout = 2 * time.Minute
+	server.ReadTimeout = 30 * time.Second
+	server.WriteTimeout = 1 * time.Minute
 	if err := server.Certificates.Load("/var/lib/gemini/certs"); err != nil {
 		log.Fatal(err)
 	}
 	server.CreateCertificate = func(hostname string) (tls.Certificate, error) {
 		return gemini.CreateCertificate(gemini.CertificateOptions{
+			Subject: pkix.Name{
+				CommonName: hostname,
+			},
 			DNSNames: []string{hostname},
 			Duration: time.Minute, // for testing purposes
 		})

fs.go

@@ -96,9 +96,9 @@ func openFile(p string) (File, error) {
 			if stat.Mode().IsRegular() {
 				return f, nil
 			}
-			return nil, ErrNotAFile
+			return nil, os.ErrNotExist
 		} else if !stat.Mode().IsRegular() {
-			return nil, ErrNotAFile
+			return nil, os.ErrNotExist
 		}
 	}
 	return f, nil

gemini.go

@@ -9,44 +9,30 @@ var crlf = []byte("\r\n")
 
 // Errors.
 var (
-	ErrInvalidURL            = errors.New("gemini: invalid URL")
-	ErrInvalidResponse       = errors.New("gemini: invalid response")
-	ErrCertificateExpired    = errors.New("gemini: certificate expired")
-	ErrCertificateNotFound   = errors.New("gemini: certificate not found")
-	ErrCertificateNotTrusted = errors.New("gemini: certificate not trusted")
-	ErrCertificateRequired   = errors.New("gemini: certificate required")
-	ErrNotAFile              = errors.New("gemini: not a file")
-	ErrNotAGeminiURL         = errors.New("gemini: not a Gemini URL")
-	ErrBodyNotAllowed        = errors.New("gemini: response status code does not allow for body")
-	ErrTooManyRedirects      = errors.New("gemini: too many redirects")
-	ErrInputRequired         = errors.New("gemini: input required")
+	ErrInvalidURL      = errors.New("gemini: invalid URL")
+	ErrInvalidResponse = errors.New("gemini: invalid response")
+	ErrBodyNotAllowed  = errors.New("gemini: response body not allowed")
 )
 
-// DefaultClient is the default client. It is used by Get and Do.
-//
-// On the first request, DefaultClient loads the default list of known hosts.
-var DefaultClient Client
+// defaultClient is the default client. It is used by Get and Do.
+var defaultClient Client
 
 // Get performs a Gemini request for the given url.
-//
-// Get is a wrapper around DefaultClient.Get.
 func Get(url string) (*Response, error) {
 	setupDefaultClientOnce()
-	return DefaultClient.Get(url)
+	return defaultClient.Get(url)
 }
 
 // Do performs a Gemini request and returns a Gemini response.
-//
-// Do is a wrapper around DefaultClient.Do.
 func Do(req *Request) (*Response, error) {
 	setupDefaultClientOnce()
-	return DefaultClient.Do(req)
+	return defaultClient.Do(req)
 }
 
 var defaultClientOnce sync.Once
 
 func setupDefaultClientOnce() {
 	defaultClientOnce.Do(func() {
-		DefaultClient.KnownHosts.LoadDefault()
+		defaultClient.KnownHosts.LoadDefault()
 	})
 }

request.go

@@ -19,7 +19,9 @@ type Request struct {
 
 	// Certificate specifies the TLS certificate to use for the request.
 	// Request certificates take precedence over client certificates.
-	// This field is ignored by the server.
+	//
+	// On the server side, if the client provided a certificate then
+	// Certificate.Leaf is guaranteed to be non-nil.
 	Certificate *tls.Certificate
 
 	// RemoteAddr allows servers and other software to record the network
@@ -39,15 +41,12 @@ func NewRequest(rawurl string) (*Request, error) {
 	if err != nil {
 		return nil, err
 	}
-	return NewRequestFromURL(u)
+	return NewRequestFromURL(u), nil
 }
 
 // NewRequestFromURL returns a new request for the given URL.
 // The host is inferred from the URL.
-func NewRequestFromURL(url *url.URL) (*Request, error) {
-	if url.Scheme != "" && url.Scheme != "gemini" {
-		return nil, ErrNotAGeminiURL
-	}
+func NewRequestFromURL(url *url.URL) *Request {
 	host := url.Host
 	if url.Port() == "" {
 		host += ":1965"
@@ -55,7 +54,7 @@ func NewRequestFromURL(url *url.URL) (*Request, error) {
 	return &Request{
 		URL:  url,
 		Host: host,
-	}, nil
+	}
 }
 
 // write writes the Gemini request to the provided buffered writer.

server.go

@@ -3,7 +3,7 @@ package gemini
 import (
 	"bufio"
 	"crypto/tls"
-	"crypto/x509"
+	"errors"
 	"log"
 	"net"
 	"net/url"
@@ -32,6 +32,11 @@ type Server struct {
 	// if the current one is expired or missing.
 	CreateCertificate func(hostname string) (tls.Certificate, error)
 
+	// ErrorLog specifies an optional logger for errors accepting connections
+	// and file system errors.
+	// If nil, logging is done via the log package's standard logger.
+	ErrorLog *log.Logger
+
 	// registered responders
 	responders map[responderKey]Responder
 	hosts      map[string]bool
@@ -118,7 +123,7 @@ func (s *Server) Serve(l net.Listener) error {
 				if max := 1 * time.Second; tempDelay > max {
 					tempDelay = max
 				}
-				log.Printf("gemini: Accept error: %v; retrying in %v", err, tempDelay)
+				s.logf("gemini: Accept error: %v; retrying in %v", err, tempDelay)
 				time.Sleep(tempDelay)
 				continue
 			}
@@ -146,22 +151,24 @@ func (s *Server) getCertificate(h *tls.ClientHelloInfo) (*tls.Certificate, error
 
 func (s *Server) getCertificateFor(hostname string) (*tls.Certificate, error) {
 	if _, ok := s.hosts[hostname]; !ok {
-		return nil, ErrCertificateNotFound
+		return nil, errors.New("hostname not registered")
 	}
-	cert, err := s.Certificates.Lookup(hostname)
 
-	switch err {
-	case ErrCertificateNotFound, ErrCertificateExpired:
+	// Generate a new certificate if it is missing or expired
+	cert, ok := s.Certificates.Lookup(hostname)
+	if !ok || cert.Leaf != nil && cert.Leaf.NotAfter.Before(time.Now()) {
 		if s.CreateCertificate != nil {
 			cert, err := s.CreateCertificate(hostname)
 			if err == nil {
-				s.Certificates.Add(hostname, cert)
+				if err := s.Certificates.Add(hostname, cert); err != nil {
+					s.logf("gemini: Failed to add new certificate for %s: %s", hostname, err)
+				}
 			}
 			return &cert, err
 		}
+		return nil, errors.New("no certificate")
 	}
-
-	return cert, err
+	return &cert, nil
 }
 
 // respond responds to a connection.
@@ -199,10 +206,24 @@ func (s *Server) respond(conn net.Conn) {
 		if url.Scheme == "" {
 			url.Scheme = "gemini"
 		}
+
+		// Store information about the TLS connection
+		connState := conn.(*tls.Conn).ConnectionState()
+		var cert *tls.Certificate
+		if len(connState.PeerCertificates) > 0 {
+			peerCert := connState.PeerCertificates[0]
+			// Store the TLS certificate
+			cert = &tls.Certificate{
+				Certificate: [][]byte{peerCert.Raw},
+				Leaf:        peerCert,
+			}
+		}
+
 		req := &Request{
-			URL:        url,
-			RemoteAddr: conn.RemoteAddr(),
-			TLS:        conn.(*tls.Conn).ConnectionState(),
+			URL:         url,
+			RemoteAddr:  conn.RemoteAddr(),
+			TLS:         connState,
+			Certificate: cert,
 		}
 		resp := s.responder(req)
 		if resp != nil {
@@ -228,6 +249,14 @@ func (s *Server) responder(r *Request) Responder {
 	return nil
 }
 
+func (s *Server) logf(format string, args ...interface{}) {
+	if s.ErrorLog != nil {
+		s.ErrorLog.Printf(format, args...)
+	} else {
+		log.Printf(format, args...)
+	}
+}
+
 // ResponseWriter is used by a Gemini handler to construct a Gemini response.
 type ResponseWriter struct {
 	b           *bufio.Writer
@@ -304,41 +333,29 @@ type Responder interface {
 	Respond(*ResponseWriter, *Request)
 }
 
-// Input returns the request query.
-// If no input is provided, it responds with StatusInput.
-func Input(w *ResponseWriter, r *Request, prompt string) (string, bool) {
-	if r.URL.ForceQuery || r.URL.RawQuery != "" {
-		query, err := url.QueryUnescape(r.URL.RawQuery)
-		return query, err == nil
-	}
-	w.WriteHeader(StatusInput, prompt)
-	return "", false
-}
-
-// SensitiveInput returns the request query.
-// If no input is provided, it responds with StatusSensitiveInput.
-func SensitiveInput(w *ResponseWriter, r *Request, prompt string) (string, bool) {
-	if r.URL.ForceQuery || r.URL.RawQuery != "" {
-		query, err := url.QueryUnescape(r.URL.RawQuery)
-		return query, err == nil
-	}
-	w.WriteHeader(StatusSensitiveInput, prompt)
-	return "", false
-}
-
-// Certificate returns the request certificate. If one is not provided,
-// it returns nil and responds with StatusCertificateRequired.
-func Certificate(w *ResponseWriter, r *Request) (*x509.Certificate, bool) {
-	if len(r.TLS.PeerCertificates) == 0 {
-		w.WriteStatus(StatusCertificateRequired)
-		return nil, false
-	}
-	return r.TLS.PeerCertificates[0], true
-}
-
 // ResponderFunc is a wrapper around a bare function that implements Responder.
 type ResponderFunc func(*ResponseWriter, *Request)
 
 func (f ResponderFunc) Respond(w *ResponseWriter, r *Request) {
 	f(w, r)
 }
+
+// Input returns the request query.
+// If the query is invalid or no query is provided, ok will be false.
+//
+// Example:
+//
+//    input, ok := gemini.Input(req)
+//    if !ok {
+//        w.WriteHeader(gemini.StatusInput, "Prompt")
+//        return
+//    }
+//    // ...
+//
+func Input(r *Request) (query string, ok bool) {
+	if r.URL.ForceQuery || r.URL.RawQuery != "" {
+		query, err := url.QueryUnescape(r.URL.RawQuery)
+		return query, err == nil
+	}
+	return "", false
+}

tofu.go

@@ -10,7 +10,6 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
-	"time"
 )
 
 // Trust represents the trustworthiness of a certificate.
@@ -25,7 +24,7 @@ const (
 // KnownHosts represents a list of known hosts.
 // The zero value for KnownHosts is an empty list ready to use.
 type KnownHosts struct {
-	hosts map[string]certInfo
+	hosts map[string]Fingerprint
 	file  *os.File
 }
 
@@ -80,47 +79,28 @@ func (k *KnownHosts) AddTemporary(hostname string, cert *x509.Certificate) {
 
 func (k *KnownHosts) add(hostname string, cert *x509.Certificate, write bool) {
 	if k.hosts == nil {
-		k.hosts = map[string]certInfo{}
+		k.hosts = map[string]Fingerprint{}
 	}
-	info := certInfo{
-		Algorithm:   "SHA-512",
-		Fingerprint: Fingerprint(cert),
-		Expires:     cert.NotAfter.Unix(),
-	}
-	k.hosts[hostname] = info
+	fingerprint := NewFingerprint(cert)
+	k.hosts[hostname] = fingerprint
 	// Append to the file
 	if write && k.file != nil {
-		appendKnownHost(k.file, hostname, info)
+		appendKnownHost(k.file, hostname, fingerprint)
 	}
 }
 
-// Lookup looks for the provided certificate in the list of known hosts.
-// If the hostname is not in the list, Lookup returns ErrCertificateNotFound.
-// If the fingerprint doesn't match, Lookup returns ErrCertificateNotTrusted.
-// Otherwise, Lookup returns nil.
-func (k *KnownHosts) Lookup(hostname string, cert *x509.Certificate) error {
-	now := time.Now().Unix()
-	fingerprint := Fingerprint(cert)
-	if c, ok := k.hosts[hostname]; ok {
-		if c.Expires <= now {
-			// Certificate is expired
-			return ErrCertificateExpired
-		}
-		if c.Fingerprint != fingerprint {
-			// Fingerprint does not match
-			return ErrCertificateNotTrusted
-		}
-		// Certificate is found
-		return nil
-	}
-	return ErrCertificateNotFound
+// Lookup returns the fingerprint of the certificate corresponding to
+// the given hostname.
+func (k *KnownHosts) Lookup(hostname string) (Fingerprint, bool) {
+	c, ok := k.hosts[hostname]
+	return c, ok
 }
 
 // Parse parses the provided reader and adds the parsed known hosts to the list.
 // Invalid lines are ignored.
 func (k *KnownHosts) Parse(r io.Reader) {
 	if k.hosts == nil {
-		k.hosts = map[string]certInfo{}
+		k.hosts = map[string]Fingerprint{}
 	}
 	scanner := bufio.NewScanner(r)
 	for scanner.Scan() {
@@ -136,15 +116,16 @@ func (k *KnownHosts) Parse(r io.Reader) {
 			continue
 		}
 		fingerprint := parts[2]
+
 		expires, err := strconv.ParseInt(parts[3], 10, 0)
 		if err != nil {
 			continue
 		}
 
-		k.hosts[hostname] = certInfo{
-			Algorithm:   algorithm,
-			Fingerprint: fingerprint,
-			Expires:     expires,
+		k.hosts[hostname] = Fingerprint{
+			Algorithm: algorithm,
+			Hex:       fingerprint,
+			Expires:   expires,
 		}
 	}
 }
@@ -156,18 +137,19 @@ func (k *KnownHosts) Write(w io.Writer) {
 	}
 }
 
-type certInfo struct {
-	Algorithm   string // fingerprint algorithm e.g. SHA-512
-	Fingerprint string // fingerprint in hexadecimal, with ':' between each octet
-	Expires     int64  // unix time of certificate notAfter date
+func appendKnownHost(w io.Writer, hostname string, f Fingerprint) (int, error) {
+	return fmt.Fprintf(w, "%s %s %s %d\n", hostname, f.Algorithm, f.Hex, f.Expires)
 }
 
-func appendKnownHost(w io.Writer, hostname string, c certInfo) (int, error) {
-	return fmt.Fprintf(w, "%s %s %s %d\n", hostname, c.Algorithm, c.Fingerprint, c.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
 }
 
-// Fingerprint returns the SHA-512 fingerprint of the provided certificate.
-func Fingerprint(cert *x509.Certificate) string {
+// NewFingerprint returns the SHA-512 fingerprint of the provided certificate.
+func NewFingerprint(cert *x509.Certificate) Fingerprint {
 	sum512 := sha512.Sum512(cert.Raw)
 	var b strings.Builder
 	for i, f := range sum512 {
@@ -176,7 +158,11 @@ func Fingerprint(cert *x509.Certificate) string {
 		}
 		fmt.Fprintf(&b, "%02X", f)
 	}
-	return b.String()
+	return Fingerprint{
+		Algorithm: "SHA-512",
+		Hex:       b.String(),
+		Expires:   cert.NotAfter.Unix(),
+	}
 }
 
 // defaultKnownHostsPath returns the default known_hosts path.