go-gemini/client.go

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package gemini
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import (
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"bufio"
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"context"
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"crypto/tls"
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"crypto/x509"
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"net"
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"strings"
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"time"
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)
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// Client is a Gemini client.
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type Client struct {
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// 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
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// 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.
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//
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// A Timeout of zero means no timeout.
Timeout time.Duration
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}
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// Get performs a Gemini request for the given URL.
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func (c *Client) Get(url string) (*Response, error) {
req, err := NewRequest(url)
if err != nil {
return nil, err
}
return c.Do(req)
}
// Do performs a Gemini request and returns a Gemini response.
func (c *Client) Do(req *Request) (*Response, error) {
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// Extract hostname
colonPos := strings.LastIndex(req.Host, ":")
if colonPos == -1 {
colonPos = len(req.Host)
}
hostname := req.Host[:colonPos]
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// Connect to the host
config := &tls.Config{
InsecureSkipVerify: true,
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MinVersion: tls.VersionTLS12,
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GetClientCertificate: func(_ *tls.CertificateRequestInfo) (*tls.Certificate, error) {
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if req.Certificate != nil {
return req.Certificate, nil
}
return &tls.Certificate{}, nil
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},
VerifyConnection: func(cs tls.ConnectionState) error {
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return c.verifyConnection(req, cs)
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},
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ServerName: hostname,
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}
// Set connection context
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ctx := req.Context
if ctx == nil {
ctx = context.Background()
}
netConn, err := (&net.Dialer{}).DialContext(ctx, "tcp", req.Host)
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if err != nil {
return nil, err
}
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conn := tls.Client(netConn, config)
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// Set connection deadline
if d := c.Timeout; d != 0 {
conn.SetDeadline(time.Now().Add(d))
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}
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// Write the request
w := bufio.NewWriter(conn)
req.write(w)
if err := w.Flush(); err != nil {
return nil, err
}
// Read the response
resp := &Response{}
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if err := resp.read(conn); err != nil {
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return nil, err
}
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// Store connection state
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resp.TLS = conn.ConnectionState()
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return resp, nil
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}
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func (c *Client) verifyConnection(req *Request, cs tls.ConnectionState) error {
// Verify the hostname
var hostname string
if host, _, err := net.SplitHostPort(req.Host); err == nil {
hostname = host
} else {
hostname = req.Host
}
cert := cs.PeerCertificates[0]
if err := verifyHostname(cert, hostname); err != nil {
return err
}
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// See if the client trusts the certificate
if c.TrustCertificate != nil {
return c.TrustCertificate(hostname, cert)
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}
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return nil
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}