go-gemini/client.go
2021-03-04 14:36:31 -05:00

215 lines
5.1 KiB
Go

package gemini
import (
"context"
"crypto/tls"
"crypto/x509"
"net"
"net/url"
"unicode/utf8"
"golang.org/x/net/idna"
)
// 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 or returns nil, the client will accept
// any certificate. Otherwise, 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
// DialContext specifies the dial function for creating TCP connections.
// If DialContext is nil, the client dials using package net.
DialContext func(ctx context.Context, network, addr string) (net.Conn, error)
}
// Get sends a Gemini request for the given URL.
// The context controls the entire lifetime of a request and its response:
// obtaining a connection, sending the request, and reading the response
// header and body.
//
// 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 user is expected to close the Response.
//
// For more control over requests, use NewRequest and Client.Do.
func (c *Client) Get(ctx context.Context, url string) (*Response, error) {
req, err := NewRequest(url)
if err != nil {
return nil, err
}
return c.Do(ctx, req)
}
// Do sends a Gemini request and returns a Gemini response.
// The context controls the entire lifetime of a request and its response:
// obtaining a connection, sending the request, and reading the response
// header and body.
//
// 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 user is expected to close the Response.
func (c *Client) Do(ctx context.Context, req *Request) (*Response, error) {
if ctx == nil {
panic("nil context")
}
// Punycode request URL host
host, port := splitHostPort(req.URL.Host)
punycode, err := punycodeHostname(host)
if err != nil {
return nil, err
}
if host != punycode {
host = punycode
// Copy the URL and update the host
u := new(url.URL)
*u = *req.URL
u.Host = net.JoinHostPort(host, port)
// Use the new URL in the request so that the server gets
// the punycoded hostname
r := new(Request)
*r = *req
r.URL = u
req = r
}
// Use request host if provided
if req.Host != "" {
host, port = splitHostPort(req.Host)
host, err = punycodeHostname(host)
if err != nil {
return nil, err
}
}
addr := net.JoinHostPort(host, port)
// Connect to the host
conn, err := c.dialContext(ctx, "tcp", addr)
if err != nil {
return nil, err
}
// Setup TLS
conn = tls.Client(conn, &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(cs, host)
},
ServerName: host,
})
type result struct {
resp *Response
err error
}
res := make(chan result, 1)
go func() {
resp, err := c.do(ctx, conn, req)
res <- result{resp, err}
}()
select {
case <-ctx.Done():
conn.Close()
return nil, ctx.Err()
case r := <-res:
return r.resp, r.err
}
}
func (c *Client) do(ctx context.Context, conn net.Conn, req *Request) (*Response, error) {
ctx, cancel := context.WithCancel(ctx)
done := ctx.Done()
w := &contextWriter{
ctx: ctx,
done: done,
cancel: cancel,
wc: conn,
}
rc := &contextReader{
ctx: ctx,
done: done,
cancel: cancel,
rc: conn,
}
// Write the request
if _, err := req.WriteTo(w); err != nil {
return nil, err
}
// Read the response
resp, err := ReadResponse(rc)
if err != nil {
return nil, err
}
resp.conn = conn
return resp, nil
}
func (c *Client) dialContext(ctx context.Context, network, addr string) (net.Conn, error) {
if c.DialContext != nil {
return c.DialContext(ctx, network, addr)
}
return (&net.Dialer{}).DialContext(ctx, network, addr)
}
func (c *Client) verifyConnection(cs tls.ConnectionState, hostname string) error {
cert := cs.PeerCertificates[0]
// See if the client trusts the certificate
if c.TrustCertificate != nil {
return c.TrustCertificate(hostname, cert)
}
return nil
}
func splitHostPort(hostport string) (host, port string) {
var err error
host, port, err = net.SplitHostPort(hostport)
if err != nil {
// Likely no port
host = hostport
port = "1965"
}
return
}
func isASCII(s string) bool {
for i := 0; i < len(s); i++ {
if s[i] >= utf8.RuneSelf {
return false
}
}
return true
}
// punycodeHostname returns the punycoded version of hostname.
func punycodeHostname(hostname string) (string, error) {
if net.ParseIP(hostname) != nil {
return hostname, nil
}
if isASCII(hostname) {
return hostname, nil
}
return idna.Lookup.ToASCII(hostname)
}