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|
// +build example
package main
import (
"bufio"
"crypto/x509"
"fmt"
"os"
"git.sr.ht/~adnano/go-gemini"
)
var (
scanner = bufio.NewScanner(os.Stdin)
client *gmi.Client
)
func init() {
// Initialize the client
client = &gmi.Client{}
client.KnownHosts.Load() // Load known hosts
client.TrustCertificate = func(hostname string, cert *x509.Certificate, knownHosts *gmi.KnownHosts) error {
err := knownHosts.Lookup(hostname, cert)
if err != nil {
switch err {
case gmi.ErrCertificateNotTrusted:
// Alert the user that the certificate is not trusted
fmt.Printf("Warning: Certificate for %s is not trusted!\n", hostname)
fmt.Println("This could indicate a Man-in-the-Middle attack.")
case gmi.ErrUnknownCertificate:
// Prompt the user to trust the certificate
trust := trustCertificate(cert)
switch trust {
case trustOnce:
// Temporarily trust the certificate
knownHosts.AddTemporary(hostname, cert)
return nil
case trustAlways:
// Add the certificate to the known hosts file
knownHosts.Add(hostname, cert)
return nil
}
}
}
return err
}
}
// sendRequest sends a request to the given URL.
func sendRequest(req *gmi.Request) error {
resp, err := client.Send(req)
if err != nil {
return err
}
// TODO: More fine-grained analysis of the status code.
switch resp.Status / 10 {
case gmi.StatusClassInput:
fmt.Printf("%s: ", resp.Meta)
scanner.Scan()
req.URL.RawQuery = scanner.Text()
return sendRequest(req)
case gmi.StatusClassSuccess:
fmt.Print(string(resp.Body))
return nil
case gmi.StatusClassRedirect:
fmt.Println("Redirecting to", resp.Meta)
// Make the request to the same host
red, err := gmi.NewRequestTo(req.Host, resp.Meta)
if err != nil {
return err
}
// Handle relative redirects
red.URL = req.URL.ResolveReference(red.URL)
fmt.Println(red.URL, red.Host)
return sendRequest(red)
case gmi.StatusClassTemporaryFailure:
return fmt.Errorf("Temporary failure: %s", resp.Meta)
case gmi.StatusClassPermanentFailure:
return fmt.Errorf("Permanent failure: %s", resp.Meta)
case gmi.StatusClassCertificateRequired:
fmt.Println("Generating client certificate for", req.Hostname())
return nil // TODO: Generate and store client certificate
}
panic("unreachable")
}
type trust int
const (
trustAbort trust = iota
trustOnce
trustAlways
)
const trustPrompt = `The certificate offered by this server is of unknown trust. Its fingerprint is:
%s
If you knew the fingerprint to expect in advance, verify that this matches.
Otherwise, this should be safe to trust.
[t]rust always; trust [o]nce; [a]bort
=> `
func trustCertificate(cert *x509.Certificate) trust {
fmt.Printf(trustPrompt, gmi.Fingerprint(cert))
scanner.Scan()
switch scanner.Text() {
case "t":
return trustAlways
case "o":
return trustOnce
default:
return trustAbort
}
}
func main() {
if len(os.Args) < 2 {
fmt.Println("usage: %s gemini://...", os.Args[0])
os.Exit(1)
}
url := os.Args[1]
req, err := gmi.NewRequest(url)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
if err := sendRequest(req); err != nil {
fmt.Println(err)
os.Exit(1)
}
}
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