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package gemini
import (
"bufio"
"bytes"
"crypto/sha512"
"crypto/x509"
"fmt"
"io"
"os"
"path/filepath"
"strconv"
"strings"
"time"
)
// KnownHosts represents a list of known hosts.
type KnownHosts struct {
hosts []KnownHost
file *os.File
}
// LoadKnownHosts loads the known hosts from the provided path.
// It creates the path and any of its parent directories if they do not exist.
// The returned KnownHosts appends to the file whenever a certificate is added.
func LoadKnownHosts(path string) (*KnownHosts, error) {
if dir := filepath.Dir(path); dir != "." {
err := os.MkdirAll(dir, 0755)
if err != nil {
return nil, err
}
}
f, err := os.OpenFile(path, os.O_CREATE|os.O_RDONLY, 0644)
if err != nil {
return nil, err
}
k := &KnownHosts{}
k.Parse(f)
f.Close()
// Open the file for append-only use
f, err = os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
if err != nil {
return nil, err
}
k.file = f
return k, nil
}
// Add adds a certificate to the KnownHosts.
// If KnownHosts was loaded from a file, Add will append to the file.
func (k *KnownHosts) Add(cert *x509.Certificate) {
host := NewKnownHost(cert)
k.hosts = append(k.hosts, host)
// Append to the file
if k.file != nil {
host.Write(k.file)
}
}
// Has reports whether the provided certificate is in the list.
func (k *KnownHosts) Has(cert *x509.Certificate) bool {
now := time.Now().Unix()
hostname := cert.Subject.CommonName
fingerprint := Fingerprint(cert)
for i := range k.hosts {
if k.hosts[i].Expires > now && k.hosts[i].Hostname == hostname &&
k.hosts[i].Fingerprint == fingerprint {
return true
}
}
return false
}
// Parse parses the provided reader and adds the parsed known hosts to the list.
// Invalid lines are ignored.
func (k *KnownHosts) Parse(r io.Reader) {
scanner := bufio.NewScanner(r)
for scanner.Scan() {
text := scanner.Text()
parts := strings.Split(text, " ")
if len(parts) < 4 {
continue
}
hostname := parts[0]
algorithm := parts[1]
fingerprint := parts[2]
expires, err := strconv.ParseInt(parts[3], 10, 0)
if err != nil {
continue
}
k.hosts = append(k.hosts, KnownHost{
Hostname: hostname,
Algorithm: algorithm,
Fingerprint: fingerprint,
Expires: expires,
})
}
}
// KnownHost represents a known host.
type KnownHost struct {
Hostname string // e.g. gemini.circumlunar.space
Algorithm string // fingerprint algorithm e.g. SHA-512
Fingerprint string // fingerprint in hexadecimal, with ':' between each octet
Expires int64 // unix time of certificate notAfter date
}
// NewKnownHost creates a new known host from a certificate.
func NewKnownHost(cert *x509.Certificate) KnownHost {
return KnownHost{
Hostname: cert.Subject.CommonName,
Algorithm: "SHA-512",
Fingerprint: Fingerprint(cert),
Expires: cert.NotAfter.Unix(),
}
}
// Write writes the known host to the provided io.Writer.
func (k KnownHost) Write(w io.Writer) (int, error) {
s := fmt.Sprintf("%s %s %s %d\n", k.Hostname, k.Algorithm, k.Fingerprint, k.Expires)
return w.Write([]byte(s))
}
// Fingerprint returns the SHA-512 fingerprint of the provided certificate.
func Fingerprint(cert *x509.Certificate) string {
sum512 := sha512.Sum512(cert.Raw)
var buf bytes.Buffer
for i, f := range sum512 {
if i > 0 {
fmt.Fprintf(&buf, ":")
}
fmt.Fprintf(&buf, "%02X", f)
}
return buf.String()
}
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