Decouple Client from KnownHostsFile

client.go

@@ -5,7 +5,6 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
-	"errors"
 	"net"
 	"net/url"
 	"strings"
@@ -13,25 +12,19 @@ import (
 )
 
 // Client is a Gemini client.
-//
-// Clients are safe for concurrent use by multiple goroutines.
 type Client struct {
-	// KnownHosts is a list of known hosts.
-	KnownHosts KnownHostsFile
+	// TrustCertificate is called to determine whether the client
+	// should trust the certificate provided by the server.
+	// If TrustCertificate is nil, the client will accept any certificate.
+	// If the returned error is not nil, the certificate will not be trusted
+	// and the request will be aborted.
+	TrustCertificate func(hostname string, cert *x509.Certificate) error
 
-	// Timeout specifies a time limit for requests made by this
-	// Client. The timeout includes connection time and reading
-	// the response body. The timer remains running after
-	// Get and Do return and will interrupt reading of the Response.Body.
-	//
-	// A Timeout of zero means no timeout.
-	Timeout time.Duration
-
-	// InsecureSkipTrust specifies whether the client should trust
-	// any certificate it receives without checking KnownHosts
-	// or calling TrustCertificate.
-	// Use with caution.
-	InsecureSkipTrust bool
+	// GetCertificate is called to retrieve a certificate upon
+	// the request of a server.
+	// If GetCertificate is nil or the returned error is not nil,
+	// the request will not be sent again and the response will be returned.
+	GetCertificate func(scope, path string) (tls.Certificate, error)
 
 	// GetInput is called to retrieve input when the server requests it.
 	// If GetInput is nil or returns false, no input will be sent and
@@ -42,25 +35,16 @@ type Client struct {
 	// If CheckRedirect is nil, redirects will not be followed.
 	CheckRedirect func(req *Request, via []*Request) error
 
-	// GetCertificate is called to retrieve a certificate upon
-	// the request of a server.
-	// If GetCertificate is nil or the returned error is not nil,
-	// the request will not be sent again and the response will be returned.
-	GetCertificate func(scope, path string) (tls.Certificate, error)
-
-	// TrustCertificate is called to determine whether the client
-	// should trust a certificate it has not seen before.
-	// If TrustCertificate is nil, the certificate will not be trusted
-	// and the connection will be aborted.
+	// Timeout specifies a time limit for requests made by this
+	// Client. The timeout includes connection time and reading
+	// the response body. The timer remains running after
+	// Get and Do return and will interrupt reading of the Response.Body.
 	//
-	// If TrustCertificate returns TrustOnce, the certificate will be added
-	// to the client's list of known hosts.
-	// If TrustCertificate returns TrustAlways, the certificate will also be
-	// written to the known hosts file.
-	TrustCertificate func(hostname string, cert *x509.Certificate) Trust
+	// A Timeout of zero means no timeout.
+	Timeout time.Duration
 }
 
-// Get performs a Gemini request for the given url.
+// Get performs a Gemini request for the given URL.
 func (c *Client) Get(url string) (*Response, error) {
 	req, err := NewRequest(url)
 	if err != nil {
@@ -130,34 +114,39 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 
 	switch {
 	case resp.Status == StatusCertificateRequired:
+		if c.GetCertificate == nil {
+			break
+		}
+
 		// Check to see if a certificate was already provided to prevent an infinite loop
 		if req.Certificate != nil {
-			return resp, nil
+			break
 		}
-
 		hostname, path := req.URL.Hostname(), strings.TrimSuffix(req.URL.Path, "/")
-		if c.GetCertificate != nil {
-			cert, err := c.GetCertificate(hostname, path)
-			if err != nil {
-				return resp, err
-			}
-			req.Certificate = &cert
-			return c.do(req, via)
+		cert, err := c.GetCertificate(hostname, path)
+		if err != nil {
+			return resp, err
 		}
-		return resp, nil
+		req.Certificate = &cert
+		return c.do(req, via)
 
 	case resp.Status.Class() == StatusClassInput:
-		if c.GetInput != nil {
-			input, ok := c.GetInput(resp.Meta, resp.Status == StatusSensitiveInput)
-			if ok {
-				req.URL.ForceQuery = true
-				req.URL.RawQuery = QueryEscape(input)
-				return c.do(req, via)
-			}
+		if c.GetInput == nil {
+			break
+		}
+
+		input, ok := c.GetInput(resp.Meta, resp.Status == StatusSensitiveInput)
+		if ok {
+			req.URL.ForceQuery = true
+			req.URL.RawQuery = QueryEscape(input)
+			return c.do(req, via)
 		}
-		return resp, nil
 
 	case resp.Status.Class() == StatusClassRedirect:
+		if c.CheckRedirect == nil {
+			break
+		}
+
 		if via == nil {
 			via = []*Request{}
 		}
@@ -171,12 +160,10 @@ func (c *Client) do(req *Request, via []*Request) (*Response, error) {
 
 		redirect := NewRequestFromURL(target)
 		redirect.Context = req.Context
-		if c.CheckRedirect != nil {
-			if err := c.CheckRedirect(redirect, via); err != nil {
-				return resp, err
-			}
-			return c.do(redirect, via)
+		if err := c.CheckRedirect(redirect, via); err != nil {
+			return resp, err
 		}
+		return c.do(redirect, via)
 	}
 
 	return resp, nil
@@ -194,33 +181,10 @@ func (c *Client) verifyConnection(req *Request, cs tls.ConnectionState) error {
 	if err := verifyHostname(cert, hostname); err != nil {
 		return err
 	}
-	if c.InsecureSkipTrust {
-		return nil
-	}
 
-	// Check the known hosts
-	knownHost, ok := c.KnownHosts.Lookup(hostname)
-	if !ok || !time.Now().Before(knownHost.Expires) {
-		// See if the client trusts the certificate
-		if c.TrustCertificate != nil {
-			switch c.TrustCertificate(hostname, cert) {
-			case TrustOnce:
-				fingerprint := NewFingerprint(cert.Raw, cert.NotAfter)
-				c.KnownHosts.Add(hostname, fingerprint)
-				return nil
-			case TrustAlways:
-				fingerprint := NewFingerprint(cert.Raw, cert.NotAfter)
-				c.KnownHosts.Add(hostname, fingerprint)
-				c.KnownHosts.Write(hostname, fingerprint)
-				return nil
-			}
-		}
-		return errors.New("gemini: certificate not trusted")
+	// See if the client trusts the certificate
+	if c.TrustCertificate != nil {
+		return c.TrustCertificate(hostname, cert)
 	}
-
-	fingerprint := NewFingerprint(cert.Raw, cert.NotAfter)
-	if knownHost.Hex == fingerprint.Hex {
-		return nil
-	}
-	return errors.New("gemini: fingerprint does not match")
+	return nil
 }

examples/client.go

@@ -5,6 +5,7 @@ package main
 import (
 	"bufio"
 	"crypto/x509"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -25,43 +26,52 @@ Otherwise, this should be safe to trust.
 [t]rust always; trust [o]nce; [a]bort
 => `
 
-var (
-	scanner = bufio.NewScanner(os.Stdin)
-	client  = &gemini.Client{}
-)
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Printf("usage: %s <url> [host]", os.Args[0])
+		os.Exit(1)
+	}
+
+	// Load known hosts file
+	var knownHosts gemini.KnownHostsFile
+	if err := knownHosts.Load(filepath.Join(xdg.DataHome(), "gemini", "known_hosts")); err != nil {
+		log.Println(err)
+	}
+
+	scanner := bufio.NewScanner(os.Stdin)
+
+	var client gemini.Client
+	client.TrustCertificate = func(hostname string, cert *x509.Certificate) error {
+		knownHost, ok := knownHosts.Lookup(hostname)
+		if ok && time.Now().Before(knownHost.Expires) {
+			// Certificate is in known hosts file and is not expired
+			return nil
+		}
 
-func init() {
-	client.Timeout = 30 * time.Second
-	client.KnownHosts.Load(filepath.Join(xdg.DataHome(), "gemini", "known_hosts"))
-	client.TrustCertificate = func(hostname string, cert *x509.Certificate) gemini.Trust {
 		fingerprint := gemini.NewFingerprint(cert.Raw, cert.NotAfter)
 		fmt.Printf(trustPrompt, hostname, fingerprint.Hex)
 		scanner.Scan()
 		switch scanner.Text() {
 		case "t":
-			return gemini.TrustAlways
+			knownHosts.Add(hostname, fingerprint)
+			knownHosts.Write(hostname, fingerprint)
+			return nil
 		case "o":
-			return gemini.TrustOnce
+			knownHosts.Add(hostname, fingerprint)
+			return nil
 		default:
-			return gemini.TrustNone
+			return errors.New("certificate not trusted")
 		}
 	}
 	client.GetInput = func(prompt string, sensitive bool) (string, bool) {
-		fmt.Printf("%s: ", prompt)
+		fmt.Printf("%s ", prompt)
 		scanner.Scan()
 		return scanner.Text(), true
 	}
-}
-
-func main() {
-	if len(os.Args) < 2 {
-		fmt.Printf("usage: %s gemini://... [host]", os.Args[0])
-		os.Exit(1)
-	}
 
+	// Do the request
 	url := os.Args[1]
 	req, err := gemini.NewRequest(url)
-
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(1)
@@ -69,13 +79,13 @@ func main() {
 	if len(os.Args) == 3 {
 		req.Host = os.Args[2]
 	}
-
 	resp, err := client.Do(req)
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(1)
 	}
 
+	// Handle response
 	if resp.Status.Class() == gemini.StatusClassSuccess {
 		defer resp.Body.Close()
 		body, err := ioutil.ReadAll(resp.Body)
@@ -84,6 +94,7 @@ func main() {
 		}
 		fmt.Print(string(body))
 	} else {
-		fmt.Printf("request failed: %d %s: %s", resp.Status, resp.Status.Message(), resp.Meta)
+		fmt.Printf("%d %s: %s\n", resp.Status, resp.Status.Message(), resp.Meta)
+		os.Exit(1)
 	}
 }

tofu.go

@@ -12,15 +12,6 @@ import (
 	"time"
 )
 
-// Trust represents the trustworthiness of a certificate.
-type Trust int
-
-const (
-	TrustNone   Trust = iota // The certificate is not trusted.
-	TrustOnce                // The certificate is trusted once.
-	TrustAlways              // The certificate is trusted always.
-)
-
 // KnownHosts maps hosts to fingerprints.
 type KnownHosts map[string]Fingerprint