go-gemini/examples/client/client.go

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