Add function to write known hosts to io.Writer

client.go

@@ -168,7 +168,7 @@ func (resp *Response) read(r *bufio.Reader) error {
 // Client represents a Gemini client.
 type Client struct {
 	// KnownHosts is a list of known hosts that the client trusts.
-	KnownHosts *KnownHosts
+	KnownHosts KnownHosts
 
 	// CertificateStore contains all the certificates that the client has stored.
 	CertificateStore *CertificateStore
@@ -210,12 +210,10 @@ func (c *Client) Send(req *Request) (*Response, error) {
 			}
 			// Check that the client trusts the certificate
 			if c.TrustCertificate == nil {
-				if c.KnownHosts == nil {
-					return ErrCertificateNotTrusted
-				} else if err := c.KnownHosts.Lookup(cert); err != nil {
+				if err := c.KnownHosts.Lookup(cert); err != nil {
 					return err
 				}
-			} else if err := c.TrustCertificate(cert, c.KnownHosts); err != nil {
+			} else if err := c.TrustCertificate(cert, &c.KnownHosts); err != nil {
 				return err
 			}
 			return nil

examples/client/client.go

@@ -19,15 +19,8 @@ var (
 )
 
 func init() {
-	// Load the list of known hosts
-	knownHosts, err := gemini.LoadKnownHosts()
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	client = &gemini.Client{
-		KnownHosts: knownHosts,
-	}
+	client = &gemini.Client{}
+	client.KnownHosts.Load()
 
 	client.TrustCertificate = func(cert *x509.Certificate, knownHosts *gemini.KnownHosts) error {
 		err := knownHosts.Lookup(cert)
@@ -53,12 +46,10 @@ func init() {
 	}
 
 	// Configure a client side certificate.
-	// To generate a certificate, run:
-	//
-	//     openssl genrsa -out client.key 2048
-	//     openssl ecparam -genkey -name secp384r1 -out client.key
-	//     openssl req -new -x509 -sha512 -key client.key -out client.crt -days 365
+	// To generate a TLS key pair, run:
 	//
+	//     go run -tags=example ../cert
+	var cert tls.Certificate
 	cert, err = tls.LoadX509KeyPair("examples/client/localhost.crt", "examples/client/localhost.key")
 	if err != nil {
 		log.Fatal(err)

examples/server/server.go

@@ -13,10 +13,7 @@ func main() {
 	// Load a TLS key pair.
 	// To generate a TLS key pair, run:
 	//
-	//     openssl genrsa -out server.key 2048
-	//     openssl ecparam -genkey -name secp384r1 -out server.key
-	//     openssl req -new -x509 -sha512 -key server.key -out server.crt -days 365
-	//
+	//     go run -tags=example ../cert
 	cert, err := tls.LoadX509KeyPair("examples/server/localhost.crt", "examples/server/localhost.key")
 	if err != nil {
 		log.Fatal(err)

gemini.go

@@ -60,11 +60,7 @@ func init() {
 var setupDefaultClientOnce sync.Once
 
 func setupDefaultClient() {
-	knownHosts, err := LoadKnownHosts()
-	if err != nil {
-		knownHosts = &KnownHosts{}
-	}
-	DefaultClient.KnownHosts = knownHosts
+	DefaultClient.KnownHosts.Load()
 }
 
 // Send sends a Gemini request and returns a Gemini response.

tofu.go

@@ -15,50 +15,50 @@ import (
 )
 
 // KnownHosts represents a list of known hosts.
+// The zero value for KnownHosts is an empty list ready to use.
 type KnownHosts struct {
 	hosts []KnownHost
 	file  *os.File
 }
 
-// LoadKnownHosts loads the known hosts from the default known hosts path.
-// The default path is $XDG_DATA_HOME/gemini/known_hosts
+// Load loads the known hosts from the default known hosts path, which is
+// `$XDG_DATA_HOME/gemini/known_hosts`.
 // It creates the path and any of its parent directories if they do not exist.
-// The returned KnownHosts appends to the file whenever a certificate is added.
-func LoadKnownHosts() (*KnownHosts, error) {
+// KnownHosts will append to the file whenever a certificate is added.
+func (k *KnownHosts) Load() error {
 	path, err := defaultKnownHostsPath()
 	if err != nil {
-		return nil, err
+		return err
 	}
-	return LoadKnownHostsFrom(path)
+	return k.LoadFrom(path)
 }
 
-// LoadKnownHosts loads the known hosts from the provided path.
+// LoadFrom loads the known hosts from the provided path.
 // It creates the path and any of its parent directories if they do not exist.
-// The returned KnownHosts appends to the file whenever a certificate is added.
-func LoadKnownHostsFrom(path string) (*KnownHosts, error) {
+// KnownHosts will append to the file whenever a certificate is added.
+func (k *KnownHosts) LoadFrom(path string) error {
 	if dir := filepath.Dir(path); dir != "." {
 		err := os.MkdirAll(dir, 0755)
 		if err != nil {
-			return nil, err
+			return err
 		}
 	}
 	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDONLY, 0644)
 	if err != nil {
-		return nil, err
+		return err
 	}
-	k := &KnownHosts{}
 	k.Parse(f)
 	f.Close()
 	// Open the file for append-only use
 	f, err = os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	k.file = f
-	return k, nil
+	return nil
 }
 
-// Add adds a certificate to the KnownHosts.
+// Add adds a certificate to the list of known hosts.
 // If KnownHosts was loaded from a file, Add will append to the file.
 func (k *KnownHosts) Add(cert *x509.Certificate) {
 	host := NewKnownHost(cert)
@@ -125,6 +125,13 @@ func (k *KnownHosts) Parse(r io.Reader) {
 	}
 }
 
+// Write writes the known hosts to the provided io.Writer.
+func (k *KnownHosts) Write(w io.Writer) {
+	for _, h := range k.hosts {
+		h.Write(w)
+	}
+}
+
 // KnownHost represents a known host.
 type KnownHost struct {
 	Hostname    string // e.g. gemini.circumlunar.space