go-gemini/client.go
2021-02-18 21:55:17 -05:00

193 lines
4.6 KiB
Go

package gemini
import (
"bufio"
"context"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"net"
"time"
)
// A Client is a Gemini client. Its zero value is a usable client.
type Client struct {
// 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.
//
// See the tofu submodule for an implementation of trust on first use.
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 or Do return and will interrupt reading of the Response.Body.
//
// A Timeout of zero means no timeout.
Timeout time.Duration
}
// Get sends a Gemini request for the given URL.
//
// An error is returned if there was a Gemini protocol error.
// A non-2x status code doesn't cause an error.
//
// If the returned error is nil, the Response will contain a non-nil Body
// which the user is expected to close.
//
// For more control over requests, use NewRequest and Client.Do.
func (c *Client) Get(url string) (*Response, error) {
req, err := NewRequest(url)
if err != nil {
return nil, err
}
return c.Do(req)
}
// Do sends a Gemini request and returns a Gemini response, following
// policy as configured on the client.
//
// An error is returned if there was a Gemini protocol error.
// A non-2x status code doesn't cause an error.
//
// If the returned error is nil, the Response will contain a non-nil Body
// which the user is expected to close.
//
// Generally Get will be used instead of Do.
func (c *Client) Do(req *Request) (*Response, error) {
// Punycode request URL host
hostname, port, err := net.SplitHostPort(req.URL.Host)
if err != nil {
// Likely no port
hostname = req.URL.Host
port = "1965"
}
punycode, err := punycodeHostname(hostname)
if err != nil {
return nil, err
}
if hostname != punycode {
hostname = punycode
// Make a copy of the request
_req := *req
req = &_req
_url := *req.URL
req.URL = &_url
// Set the host
req.URL.Host = net.JoinHostPort(hostname, port)
}
// Use request host if provided
if req.Host != "" {
hostname, port, err = net.SplitHostPort(req.Host)
if err != nil {
// Port is required
return nil, err
}
// Punycode hostname
hostname, err = punycodeHostname(hostname)
if err != nil {
return nil, err
}
}
// Connect to the host
config := &tls.Config{
InsecureSkipVerify: true,
MinVersion: tls.VersionTLS12,
GetClientCertificate: func(_ *tls.CertificateRequestInfo) (*tls.Certificate, error) {
if req.Certificate != nil {
return req.Certificate, nil
}
return &tls.Certificate{}, nil
},
VerifyConnection: func(cs tls.ConnectionState) error {
return c.verifyConnection(hostname, punycode, cs)
},
ServerName: hostname,
}
ctx := req.Context
if ctx == nil {
ctx = context.Background()
}
start := time.Now()
dialer := net.Dialer{
Timeout: c.Timeout,
}
address := net.JoinHostPort(hostname, port)
netConn, err := dialer.DialContext(ctx, "tcp", address)
if err != nil {
return nil, err
}
conn := tls.Client(netConn, config)
// Set connection deadline
if c.Timeout != 0 {
err := conn.SetDeadline(start.Add(c.Timeout))
if err != nil {
return nil, fmt.Errorf("failed to set connection deadline: %w", err)
}
}
resp, err := c.do(conn, req)
if err != nil {
// If we fail to perform the request/response we have
// to take responsibility for closing the connection.
_ = conn.Close()
return nil, err
}
// Store connection state
state := conn.ConnectionState()
resp.TLS = &state
return resp, nil
}
func (c *Client) do(conn *tls.Conn, req *Request) (*Response, error) {
// Write the request
w := bufio.NewWriter(conn)
err := req.Write(w)
if err != nil {
return nil, fmt.Errorf("failed to write request: %w", err)
}
// Read the response
resp, err := ReadResponse(conn)
if err != nil {
return nil, err
}
return resp, nil
}
func (c *Client) verifyConnection(hostname, punycode string, cs tls.ConnectionState) error {
cert := cs.PeerCertificates[0]
// Verify punycoded hostname
if err := verifyHostname(cert, punycode); err != nil {
return err
}
// Check expiration date
if !time.Now().Before(cert.NotAfter) {
return errors.New("gemini: certificate expired")
}
// See if the client trusts the certificate
if c.TrustCertificate != nil {
return c.TrustCertificate(hostname, cert)
}
return nil
}