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keyscan.go
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keyscan.go
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package sshutil
import (
"fmt"
"net"
"strconv"
"strings"
"golang.org/x/crypto/ssh"
)
const defaultPort = 22
var ErrMalformedServer = fmt.Errorf("invalid server, must be of the form hostname, or hostname:port")
var errCallbackDone = fmt.Errorf("callback failed on purpose")
// SshKeyScan scans a ssh server for the hostkey; server should be in the form hostname, or hostname:port
func SSHKeyScan(server string) (string, error) {
port := defaultPort
parts := strings.Split(server, ":")
if len(parts) == 2 {
var err error
server = parts[0]
port, err = strconv.Atoi(parts[1])
if err != nil {
return "", ErrMalformedServer
}
} else if len(parts) > 2 {
return "", ErrMalformedServer
}
var key string
KeyScanCallback := func(hostname string, remote net.Addr, pubKey ssh.PublicKey) error {
hostname = strings.TrimSuffix(hostname, fmt.Sprintf(":%d", port))
key = strings.TrimSpace(fmt.Sprintf("%s %s", hostname, string(ssh.MarshalAuthorizedKey(pubKey))))
return errCallbackDone
}
config := &ssh.ClientConfig{
HostKeyCallback: KeyScanCallback,
}
conn, err := ssh.Dial("tcp", fmt.Sprintf("%s:%d", server, port), config)
if key != "" {
// as long as we get the key, the function worked
err = nil
}
if conn != nil {
conn.Close()
}
return key, err
}