/*
 * This file is part of Cockpit.
 *
 * Copyright (C) 2016 Red Hat, Inc.
 *
 * Cockpit is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * Cockpit is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Cockpit; If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "common/cockpitauthorize.h"
#include "common/cockpitconf.h"
#include "common/cockpithex.h"
#include "common/cockpitframe.h"
#include "common/cockpitjson.h"
#include "common/cockpitmemory.h"
#include "common/cockpitpipe.h"
#include "common/cockpittest.h"
#include "common/cockpittransport.h"

#include "cockpitsshrelay.h"
#include "cockpitsshoptions.h"

#include <libssh/libssh.h>
#include <libssh/callbacks.h>

#include <krb5/krb5.h>
#include <gssapi/gssapi.h>
#include <gssapi/gssapi_krb5.h>
#include <gssapi/gssapi_ext.h>

#include <glib/gstdio.h>

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>

typedef struct {
  const gchar *logname;
  gchar *initial_auth_data;
  gchar *auth_type;

  gchar **env;
  CockpitSshOptions *ssh_options;

  gchar *username;
  gboolean in_bridge;

  ssh_session session;

  gchar *conversation;

  gchar *host_key;
  gchar *host_fingerprint;
  const gchar *host_key_type;
  GHashTable *auth_results;
  gchar *user_known_hosts;

  gchar *problem_error;
} CockpitSshData;

static gchar *tmp_knownhost_file;

static const gchar*
exit_code_problem (int exit_code)
{
  switch (exit_code)
    {
      case 0:
        return NULL;
      case AUTHENTICATION_FAILED:
        return "authentication-failed";
      case DISCONNECTED:
        return "disconnected";
      case TERMINATED:
        return "terminated";
      case NO_COCKPIT:
        return "no-cockpit";
      default:
        return "internal-error";
    }
}

static const gchar *
auth_method_description (int method)
{
  if (method == SSH_AUTH_METHOD_NONE)
    return "none";
  else if (method == SSH_AUTH_METHOD_PASSWORD || method == SSH_AUTH_METHOD_INTERACTIVE)
    return "password";
  else if (method == SSH_AUTH_METHOD_PUBLICKEY)
    return "public-key";
  else if (method == SSH_AUTH_METHOD_HOSTBASED)
    return "host-based";
  else if (method == SSH_AUTH_METHOD_GSSAPI_MIC)
    return "gssapi-mic";
  else
    return "unknown";
}

static gchar *
auth_methods_line (int methods)
{
  GString *string;
  int i = 0;
  int check[6] = {
    SSH_AUTH_METHOD_NONE,
    SSH_AUTH_METHOD_INTERACTIVE,
    SSH_AUTH_METHOD_PASSWORD,
    SSH_AUTH_METHOD_PUBLICKEY,
    SSH_AUTH_METHOD_HOSTBASED,
    SSH_AUTH_METHOD_GSSAPI_MIC
  };

  string = g_string_new ("");
  for (i = 0; i < G_N_ELEMENTS (check); i++)
    {
      if (methods & check[i])
        {
          g_string_append (string, auth_method_description (check[i]));
          g_string_append (string, " ");
        }
    }

  return g_string_free (string, FALSE);
}

static gboolean
ssh_msg_is_disconnected (const gchar *msg)
{
      return msg && (strstr (msg, "disconnected") ||
                     strstr (msg, "SSH_MSG_DISCONNECT") ||
                     strstr (msg, "Socket error: Success") ||
                     strstr (msg, "Socket error: Connection reset by peer"));
}

static gboolean
write_control_message (int fd,
                       JsonObject *options)
{
  gboolean ret = TRUE;
  gchar *payload;
  gchar *prefixed;
  gsize length;

  payload = cockpit_json_write_object (options, &length);
  prefixed = g_strdup_printf ("\n%s", payload);
  if (cockpit_frame_write (fd, (unsigned char *)prefixed, length + 1) < 0)
    {
      g_message ("couldn't write control message: %s", g_strerror (errno));
      ret = FALSE;
    }
  g_free (prefixed);
  g_free (payload);

  return ret;
}

static void
byte_array_clear_and_free (gpointer data)
{
  GByteArray *buffer = data;
  cockpit_memory_clear (buffer->data, buffer->len);
  g_byte_array_free (buffer, TRUE);
}

static JsonObject *
read_control_message (int fd)
{
  JsonObject *options = NULL;
  GBytes *payload = NULL;
  GBytes *bytes = NULL;
  gchar *channel = NULL;
  guchar *data = NULL;
  gssize length = 0;

  length = cockpit_frame_read (fd, &data);
  if (length < 0)
    {
      g_message ("couldn't read control message: %s", g_strerror (errno));
      length = 0;
    }
  else if (length > 0)
    {
      /* This could have a password, so clear it when freeing */
      bytes = g_bytes_new_with_free_func (data, length, byte_array_clear_and_free,
                                          g_byte_array_new_take (data, length));
      payload = cockpit_transport_parse_frame (bytes, &channel);
      data = NULL;
    }

  if (payload == NULL)
    {
      if (length > 0)
        g_message ("cockpit-ssh did not receive valid message");
    }
  else if (channel != NULL)
    {
      g_message ("cockpit-ssh did not receive a control message");
    }
  else if (!cockpit_transport_parse_command (payload, NULL, NULL, &options))
    {
      g_message ("cockpit-ssh did not receive a valid control message");
    }

  g_free (channel);

  if (bytes)
    g_bytes_unref (bytes);
  if (payload)
    g_bytes_unref (payload);
  free (data);
  return options;
}

static void
send_authorize_challenge (const gchar *challenge)
{
  gchar *cookie = NULL;
  JsonObject *object = json_object_new ();

  cookie = g_strdup_printf ("session%u%u",
                            (unsigned int)getpid(),
                            (unsigned int)time (NULL));
  json_object_set_string_member (object, "command", "authorize");
  json_object_set_string_member (object, "challenge", challenge);
  json_object_set_string_member (object, "cookie", cookie);

  write_control_message (STDOUT_FILENO, object);

  g_free (cookie);
  json_object_unref (object);
}

static gchar *
challenge_for_auth_data (const gchar *challenge,
                         gchar **ret_type)
{
  const gchar *response = NULL;
  const gchar *command;
  gchar *ptr = NULL;
  gchar *type = NULL;
  JsonObject *reply;

  send_authorize_challenge (challenge ? challenge : "*");
  reply = read_control_message (STDIN_FILENO);
  if (!reply)
    goto out;

  if (!cockpit_json_get_string (reply, "command", "", &command) ||
      !g_str_equal (command, "authorize"))
    {
      g_message ("received \"%s\" control message instead of \"authorize\"", command);
    }
  else if (!cockpit_json_get_string (reply, "response", NULL, &response))
    {
      g_message ("received unexpected \"authorize\" control message: %s", response);
    }

  if (response)
    cockpit_authorize_type (response, &type);

out:
  if (ret_type)
    *ret_type = type;
  else
    g_free (type);

  if (response && !g_str_equal (response, ""))
    ptr = g_strdup (response);

  if (reply)
    json_object_unref (reply);
  return ptr;
}

static gchar *
challenge_for_knownhosts_data (CockpitSshData *data)
{
  const gchar *value = NULL;
  gchar *ret = NULL;
  gchar *response = NULL;

  response = challenge_for_auth_data ("x-host-key", NULL);
  if (response)
    {
      value = cockpit_authorize_type (response, NULL);
      /* Legacy blank string means force fail */
      if (value && value[0] == '\0')
        ret = g_strdup ("* invalid key");
      else
        ret = g_strdup (value);
    }


  g_free (response);
  return ret;
}

static gchar *
prompt_with_authorize (CockpitSshData *data,
                       const gchar *prompt,
                       const gchar *msg,
                       const gchar *default_value,
                       const gchar *host_key,
                       gboolean echo)
{
  JsonObject *request = NULL;
  JsonObject *reply = NULL;
  const gchar *command = NULL;
  const char *response = NULL;
  char *challenge = NULL;
  gchar *result = NULL;
  gboolean ret;

  challenge = cockpit_authorize_build_x_conversation (prompt, &data->conversation);
  if (!challenge)
    return NULL;

  request = json_object_new ();
  json_object_set_string_member (request, "command", "authorize");
  json_object_set_string_member (request, "cookie", data->conversation);
  json_object_set_string_member (request, "challenge", challenge);
  cockpit_memory_clear (challenge, -1);
  free (challenge);

  if (msg)
    json_object_set_string_member (request, "message", msg);
  if (default_value)
    json_object_set_string_member (request, "default", default_value);
  if (host_key)
    json_object_set_string_member (request, "host-key", host_key);

  json_object_set_boolean_member (request, "echo", echo);

  ret = write_control_message (STDOUT_FILENO, request);
  json_object_unref (request);

  if (!ret)
    return NULL;

  reply = read_control_message (STDIN_FILENO);
  if (!reply)
    return NULL;

  if (!cockpit_json_get_string (reply, "command", "", &command) ||
      !g_str_equal (command, "authorize"))
    {
      g_message ("received \"%s\" control message instead of \"authorize\"", command);
    }
  else if (!cockpit_json_get_string (reply, "response", "", &response))
    {
      g_message ("received unexpected \"authorize\" control message");
    }
  else if (!g_str_equal (response, ""))
    {
      result = cockpit_authorize_parse_x_conversation (response, NULL);
      if (!result)
        g_message ("received unexpected \"authorize\" control message \"response\"");
    }

  json_object_unref (reply);
  return result;
}

static const gchar *
prompt_for_host_key (CockpitSshData *data)
{
  const gchar *ret;
  gchar *host = NULL;
  guint port = 22;
  gchar *message = NULL;
  gchar *prompt = NULL;
  gchar *reply = NULL;

  if (ssh_options_get (data->session, SSH_OPTIONS_HOST, &host) < 0)
    {
      g_warning ("Failed to get host");
      goto out;
    }

  if (ssh_options_get_port (data->session, &port) < 0)
    {
      g_warning ("Failed to get port");
      goto out;
    }

  message = g_strdup_printf ("The authenticity of host '%s:%d' can't be established. Do you want to proceed this time?",
                             host, port);
  prompt = g_strdup_printf ("SHA256 Fingerprint (%s):", data->host_key_type);

  reply = prompt_with_authorize (data, prompt, message, data->host_fingerprint, data->host_key, TRUE);

out:
  if (g_strcmp0 (reply, data->host_fingerprint) == 0 || g_strcmp0 (reply, data->host_key) == 0)
    ret = NULL;
  else
    ret = "unknown-hostkey";

  g_free (reply);
  g_free (message);
  g_free (prompt);
  g_free (host);
  return ret;
}

static void cleanup_knownhosts_file (void)
{
  if (tmp_knownhost_file)
    {
      g_unlink (tmp_knownhost_file);
      g_free (tmp_knownhost_file);
    }
}

static gboolean
write_tmp_knownhosts_file (CockpitSshData *data,
                           const gchar *content,
                           const gchar **problem)
{
  int fd;
  g_autoptr(GError) error = NULL;

  fd = g_file_open_tmp ("known-hosts.XXXXXX", &tmp_knownhost_file, &error);
  if (fd < 0)
    {
      g_warning ("%s: couldn't open temporary known host file for data: %s",
                 data->logname, error->message);
      *problem = "internal-error";
      return FALSE;
    }
  /* now we own the file; let g_file_set_contents() do the safe writing, instead of bothering with a write() loop */
  close (fd);

  atexit (cleanup_knownhosts_file);

  if (!g_file_set_contents (tmp_knownhost_file, content, -1, &error))
    {
      g_warning ("%s: couldn't write data to temporary known host file %s: %s", data->logname, tmp_knownhost_file, error->message);
      *problem = "internal-error";
      return FALSE;
    }

  return TRUE;
}

/**
 * prepend_host_port:
 *
 * Transform lines of keys to an ssh known_hosts format with lines of
 * "[host]:port key".
 */
static gchar *
prepend_host_port (const gchar *host,
                   guint port,
                   const gchar *keys)
{
  gchar **lines = g_strsplit (keys, "\n", 0);
  gchar **line;
  GString *result = g_string_new (NULL);

  for (line = lines; *line; ++line)
    {
      if (port == 22)
        g_string_append_printf (result, "%s %s\n", host, *line);
      else
        g_string_append_printf (result, "[%s]:%d %s\n", host, port, *line);
    }

  g_strfreev (lines);
  return g_string_free (result, FALSE);

}

static gboolean
session_has_known_host_in_file (const gchar *file,
                                CockpitSshData *data,
                                const gchar *host,
                                const guint port)
{
  g_warn_if_fail (ssh_options_set (data->session, SSH_OPTIONS_KNOWNHOSTS, file) == 0);
  return ssh_session_has_known_hosts_entry (data->session) == SSH_KNOWN_HOSTS_OK;
}

static gboolean
is_localhost (const char *host)
{
  return g_strcmp0 (host, "127.0.0.1") == 0 ||
         g_strcmp0 (host, "::1") == 0 ||
         g_strcmp0 (host, "localhost") == 0 ||
         g_strcmp0 (host, "localhost4") == 0 ||
         g_strcmp0 (host, "localhost6") == 0;
}

/**
 * set_knownhosts_file:
 *
 * Check the various ssh known hosts locations and set the appropriate one into
 * SSH_OPTIONS_KNOWNHOSTS.
 *
 * Returns: error string or %NULL on success.
 */
static const gchar *
set_knownhosts_file (CockpitSshData *data,
                     const gchar* host,
                     const guint port)
{
  gboolean host_known;
  const gchar *problem = NULL;
  gchar *sout = NULL;
  gchar *serr = NULL;
  gchar *authorize_knownhosts_data = NULL;

  /* first check the libssh defaults including local and global file */
  host_known = session_has_known_host_in_file (NULL, data, host, port);

  /* check file set by COCKPIT_SSH_KNOWN_HOSTS_FILE */
  if (!host_known)
    host_known = session_has_known_host_in_file (data->ssh_options->knownhosts_file, data, host, port);


  /* last (most expensive) fallback is to ask sssd's ssh known_hosts proxy */
  if (!host_known && tmp_knownhost_file == NULL)
    {
      char port_str[10];
      const gchar *argv [] = {
          "sss_ssh_knownhostsproxy",
          "--pubkey",
          "--port", port_str,
          host,
          NULL
      };
      GError *error = NULL;
      gint exit;

      g_debug ("%s: host not known in any local file, asking sssd", data->logname);

      snprintf (port_str, sizeof (port_str), "%u", port);

      if (g_spawn_sync (NULL, (gchar **) argv, NULL, G_SPAWN_SEARCH_PATH, NULL,
                        NULL, &sout, &serr, &exit, &error))
        {
          sout = g_strstrip (sout);
          if (exit == 0 && strlen (sout) > 0)
            {
              gchar *known_hosts = prepend_host_port (host, port, sout);
              gboolean res = write_tmp_knownhosts_file (data, known_hosts, &problem);
              g_free (known_hosts);
              if (!res)
                goto out;

              host_known = session_has_known_host_in_file (tmp_knownhost_file, data, host, port);
              if (host_known)
                data->ssh_options->knownhosts_file = tmp_knownhost_file;
              else
                g_warning ("sss_ssh_knownhostsproxy reported key for %s:%u which is not known to session_has_known_host_in_file()", host, port);
            } else {
              /* the --pubkey option is not yet known by many older distributions; don't show the error in the log */
              g_debug ("%s: sss_ssh_knownhostsproxy failed: exit code %i, output '%s', error '%s'", data->logname, exit, sout, serr);
            }
        } else {
          g_debug ("%s: Failed to run sss_ssh_knownhostsproxy: %s", data->logname, error->message);
          g_clear_error (&error);
        }
    }

  if (!host_known)
    {
      authorize_knownhosts_data = challenge_for_knownhosts_data (data);
      if (authorize_knownhosts_data)
        {
          if (write_tmp_knownhosts_file (data, authorize_knownhosts_data, &problem))
            {
              host_known = session_has_known_host_in_file (tmp_knownhost_file, data, host, port);
              if (host_known)
                data->ssh_options->knownhosts_file = tmp_knownhost_file;
              else
                g_warning ("authorize challenge reported key for %s:%u which is not known to cockpit_is_host_known()", host, port);
            }
          else
            goto out;
        }
    }

  g_debug ("%s: using known hosts file %s; host known: %i; connect to unknown hosts: %i",
           data->logname, data->ssh_options->knownhosts_file, host_known, data->ssh_options->connect_to_unknown_hosts);
  if (!data->ssh_options->connect_to_unknown_hosts && !host_known && !is_localhost (host))
      {
          g_message ("%s: refusing to connect to unknown host: %s:%d",
                     data->logname, host, port);
          problem = "unknown-host";
          goto out;
      }

  problem = NULL;
out:
  g_free (authorize_knownhosts_data);
  g_free (sout);
  g_free (serr);
  return problem;
}

static const gchar *
verify_knownhost (CockpitSshData *data,
                  const gchar* host,
                  const guint port)
{
  const gchar *ret = "invalid-hostkey";
  ssh_key key = NULL;
  unsigned char *hash = NULL;
  enum ssh_known_hosts_e state;
  gsize len;

  g_warn_if_fail (ssh_session_export_known_hosts_entry(data->session, &data->host_key) == SSH_OK);
  if (data->host_key == NULL)
    {
      ret = "internal-error";
      goto done;
    }

  if (ssh_get_server_publickey (data->session, &key) != SSH_OK)
    {
      g_warning ("Couldn't look up ssh host key");
      ret = "internal-error";
      goto done;
    }

  data->host_key_type = ssh_key_type_to_char (ssh_key_type (key));
  if (data->host_key_type == NULL)
    {
      g_warning ("Couldn't lookup host key type");
      ret = "internal-error";
      goto done;
    }

  if (ssh_get_publickey_hash (key, SSH_PUBLICKEY_HASH_SHA256, &hash, &len) < 0)
    {
      g_warning ("Couldn't hash ssh public key");
      ret = "internal-error";
      goto done;
    }
  else
    {
      data->host_fingerprint = ssh_get_fingerprint_hash (SSH_PUBLICKEY_HASH_SHA256, hash, len);
      ssh_clean_pubkey_hash (&hash);
    }

  state = ssh_session_is_known_server (data->session);
  if (state == SSH_KNOWN_HOSTS_OK)
    {
      g_debug ("%s: verified host key", data->logname);
      ret = NULL; /* success */
      goto done;
    }
  else if (state == SSH_KNOWN_HOSTS_ERROR)
    {
      g_warning ("%s: couldn't check host key: %s", data->logname,
                 ssh_get_error (data->session));
      ret = "internal-error";
      goto done;
    }

  switch (state)
    {
    case SSH_KNOWN_HOSTS_OK:
    case SSH_KNOWN_HOSTS_ERROR:
      g_assert_not_reached ();
      break;
    case SSH_KNOWN_HOSTS_CHANGED:
      g_message ("%s: %s host key for server has changed to: %s",
                 data->logname, data->host_key_type, data->host_fingerprint);
      break;
    case SSH_KNOWN_HOSTS_OTHER:
      g_message ("%s: host key for this server changed key type: %s",
                 data->logname, data->host_key_type);
      break;
    case SSH_KNOWN_HOSTS_NOT_FOUND:
      g_debug ("%s: Couldn't find the known hosts file", data->logname);
      /* fall through */
    case SSH_KNOWN_HOSTS_UNKNOWN:
      ret = prompt_for_host_key (data);
      if (ret)
        {
          g_message ("%s: %s host key for server is not known: %s",
                     data->logname, data->host_key_type, data->host_fingerprint);
        }
      break;
    }

done:
  if (key)
    ssh_key_free (key);
  return ret;
}

static const gchar *
auth_result_string (int rc)
{
  switch (rc)
    {
    case SSH_AUTH_SUCCESS:
      return "succeeded";
    case SSH_AUTH_DENIED:
      return "denied";
    case SSH_AUTH_PARTIAL:
      return "partial";
      break;
    case SSH_AUTH_AGAIN:
      return "again";
    default:
      return "error";
    }
}

static gchar *
parse_auth_password (const gchar *auth_type,
                     const gchar *auth_data)
{
  gchar *password = NULL;

  g_assert (auth_data != NULL);
  g_assert (auth_type != NULL);

  if (g_strcmp0 (auth_type, "basic") == 0)
    password = cockpit_authorize_parse_basic (auth_data, NULL);
  else
    password = g_strdup (cockpit_authorize_type (auth_data, NULL));

  if (password == NULL)
    password = g_strdup ("");

  return password;
}

static int
do_interactive_auth (CockpitSshData *data)
{
  int rc;
  gboolean sent_pw = FALSE;
  gchar *password = NULL;

  password = parse_auth_password (data->auth_type,
                                  data->initial_auth_data);
  rc = ssh_userauth_kbdint (data->session, NULL, NULL);
  while (rc == SSH_AUTH_INFO)
    {
      const gchar *msg;
      int n, i;

      msg = ssh_userauth_kbdint_getinstruction (data->session);
      n = ssh_userauth_kbdint_getnprompts (data->session);

      for (i = 0; i < n && rc == SSH_AUTH_INFO; i++)
        {
          const char *prompt;
          char *answer = NULL;
          char echo = '\0';
          int status = 0;
          prompt = ssh_userauth_kbdint_getprompt (data->session, i, &echo);
          g_debug ("%s: Got prompt %s prompt", data->logname, prompt);
          if (!sent_pw)
            {
              status = ssh_userauth_kbdint_setanswer (data->session, i, password);
              sent_pw = TRUE;
            }
          else
            {
              answer = prompt_with_authorize (data, prompt, msg, NULL, NULL, echo != '\0');
              if (answer)
                  status = ssh_userauth_kbdint_setanswer (data->session, i, answer);
              else
                  rc = SSH_AUTH_ERROR;

              g_free (answer);
            }

          if (status < 0)
            {
              g_warning ("%s: failed to set answer for %s", data->logname, prompt);
              rc = SSH_AUTH_ERROR;
            }
        }

      if (rc == SSH_AUTH_INFO)
        rc = ssh_userauth_kbdint (data->session, NULL, NULL);
    }

  cockpit_memory_clear (password, strlen (password));
  g_free (password);
  return rc;
}

static int
do_password_auth (CockpitSshData *data)
{
  gchar *password = NULL;
  const gchar *msg;
  int rc;

  password = parse_auth_password (data->auth_type,
                                  data->initial_auth_data);

  rc = ssh_userauth_password (data->session, NULL, password);
  switch (rc)
    {
    case SSH_AUTH_SUCCESS:
      g_debug ("%s: password auth succeeded", data->logname);
      break;
    case SSH_AUTH_DENIED:
      g_debug ("%s: password auth failed", data->logname);
      break;
    case SSH_AUTH_PARTIAL:
      g_message ("%s: password auth worked, but server wants more authentication",
                 data->logname);
      break;
    case SSH_AUTH_AGAIN:
      g_message ("%s: password auth failed: server asked for retry",
                 data->logname);
      break;
    default:
      msg = ssh_get_error (data->session);
      g_message ("%s: couldn't authenticate: %s", data->logname, msg);
    }

  cockpit_memory_clear (password, strlen (password));
  g_free (password);
  return rc;
}

struct CockpitSshPromptData {
  CockpitSshData *data;
  const gchar *identity;
  gboolean did_prompt;
};

/* We don't support unlocking identities within cockpit-ssh so fail here */
static int
prompt_for_identity_password (const char *prompt, char *buf, size_t len,
                              int echo, int verify, void *userdata)
{
  struct CockpitSshPromptData *prompt_data = userdata;
  prompt_data->data->problem_error = g_strdup_printf ("locked identity: %s", prompt_data->identity);
  prompt_data->did_prompt = TRUE;
  return -1;
}

static int
do_auto_auth (CockpitSshData *data)
{
  /* HACK: When prompting for a key passphrase, libssh doesn't provide
     enough information to say which key it is for, but we need that
     information since Cockpit will offer to load the key into the
     agent in order to log in.

     To get this information, we reimplement
     ssh_userauth_publickey_auto here in a way that passes that
     information to the callback.

     We would like to iterate over all configured identities, the same
     way that the real ssh_userauth_publickey does, but there is no
     API to do that either.  So we hard code all the names, based on
     what ssh-add would add to the agent.

     This whole thing is meant to be replaced with something like this
     eventually:

     static int
     intercept_prompt (const char *prompt, char *buf, size_t len,
                       int echo, int verify, void *userdata)
     {
       CockpitSshData *data = userdata;
       char *identity = NULL;
       if (ssh_userauth_publickey_auto_get_current_identity (data->session, &identity) == SSH_OK)
         {
           data->problem_error = g_strdup_printf ("locked identity: %s", identity);
           ssh_string_free_char (identity);
         }
       return -1;
     }

     static int
     do_auto_auth (CockpitSshData *data)
     {
       struct ssh_callbacks_struct cb = { .userdata = data, .auth_function = intercept_prompt };
       ssh_callbacks_init (&cb);
       ssh_set_callbacks (data->session, &cb);
       int rc = ssh_userauth_publickey_auto (data->session, NULL, NULL);
       ssh_set_callbacks (data->session, NULL);
       return rc;
     }

     See https://gitlab.com/libssh/libssh-mirror/-/merge_requests/134
  */

  int rc;
  const gchar *msg;

  rc = ssh_userauth_agent (data->session, NULL);
  if (rc == SSH_AUTH_SUCCESS ||
      rc == SSH_AUTH_PARTIAL ||
      rc == SSH_AUTH_AGAIN ) {
    return rc;
  }

  /* See "man ssh-add" for the list of default identities.
   */
  gchar *libssh_identity = NULL;
  gchar *default_identities[] = { "id_dsa", "id_ecdsa", "id_ecdsa_sk", "id_ed25519", "id_ed25519_sk", "id_rsa", NULL };

  rc = ssh_options_get (data->session, SSH_OPTIONS_IDENTITY, &libssh_identity);
  if (rc != SSH_OK)
    {
      g_debug ("Unable to get identity from config");
      return rc;
    }

  for (int i = -1; i < 0 || default_identities[i]; i++)
    {
      g_autofree gchar *identity = NULL;
      g_autofree gchar *pub_key_path = NULL;
      ssh_key priv_key = NULL;
      ssh_key pub_key = NULL;

      if (i == -1)
        identity = g_strdup (libssh_identity);
      else
        {
          identity = g_strdup_printf ("%s/.ssh/%s", g_get_home_dir (), default_identities[i]);
          // No need to try the libssh identity twice, and we need to
          // be precious with our tries because when we run into
          // MaxAuthTries, libssh will hang.
          if (g_strcmp0 (identity, libssh_identity) == 0)
            continue;
        }

      pub_key_path = g_strconcat (identity, ".pub", NULL);
      rc = ssh_pki_import_pubkey_file (pub_key_path, &pub_key);
      /* If the public key file exist and is readable, see if the identity is accepted by the server */
      if (rc == SSH_OK)
        {
          rc = ssh_userauth_try_publickey (data->session, NULL, pub_key);
          if (rc != SSH_AUTH_SUCCESS)
            {
              g_debug ("%s isn't accepted by the server", identity);
              ssh_key_free (pub_key);
              continue;
            }
        }
      else if (rc == SSH_EOF)
        {
          g_debug ("Public key file %s doesn't exist or isn't readable", pub_key_path);
        }
      else
        {
          msg = ssh_get_error (data->session);
          g_warning ("Error importing public key %s: %s", pub_key_path, msg);
        }

      struct CockpitSshPromptData pd = { data, identity, FALSE };
      rc = ssh_pki_import_privkey_file (identity, NULL, prompt_for_identity_password, &pd, &priv_key);
      if (rc == SSH_ERROR)
        {
          if (pd.did_prompt)
            rc = SSH_AUTH_DENIED;
        }
      else if (rc == SSH_EOF)
        {
          rc = SSH_AUTH_DENIED;
        }
      else if (rc == SSH_OK)
        {
          rc = ssh_userauth_publickey (data->session, NULL, priv_key);
          ssh_key_free (priv_key);

          if (rc == SSH_AUTH_SUCCESS)
            {
              g_debug ("%s: key auth succeeded", data->logname);
              ssh_key_free (pub_key);
              break;
            }
          else
            {
              switch (rc)
                {
                case SSH_AUTH_DENIED:
                  g_debug ("%s: key auth failed", data->logname);
                  break;
                case SSH_AUTH_PARTIAL:
                  g_message ("%s: key auth worked, but server wants more authentication",
                             data->logname);
                  break;
                case SSH_AUTH_AGAIN:
                  g_message ("%s: key auth failed: server asked for retry",
                             data->logname);
                  break;
                default:
                  msg = ssh_get_error (data->session);
                  g_message ("%s: couldn't key authenticate: %s", data->logname, msg);
                }
            }
        }

      ssh_key_free (pub_key);
    }

  ssh_string_free_char (libssh_identity);
  return rc;
}

static int
do_key_auth (CockpitSshData *data)
{
  int rc;
  const gchar *msg;

  g_assert (data->initial_auth_data != NULL);

  rc = do_auto_auth (data);
  if (rc != SSH_AUTH_SUCCESS)
    {
      const gchar *key_data;
      ssh_key key;

      key_data = cockpit_authorize_type (data->initial_auth_data, NULL);
      if (!key_data)
        {
          g_message ("%s: Got invalid private-key data, %s", data->logname, data->initial_auth_data);
          return SSH_AUTH_DENIED;
        }

      rc = ssh_pki_import_privkey_base64 (key_data, NULL, NULL, NULL, &key);
      if (rc != SSH_OK)
        {
          g_message ("%s: Got invalid key data, %s", data->logname, data->initial_auth_data);
          return rc;
        }
      rc = ssh_userauth_publickey (data->session, NULL, key);
      ssh_key_free (key);
    }

  switch (rc)
    {
    case SSH_AUTH_SUCCESS:
      g_debug ("%s: key auth succeeded", data->logname);
      break;
    case SSH_AUTH_DENIED:
      g_debug ("%s: key auth failed", data->logname);
      break;
    case SSH_AUTH_PARTIAL:
      g_message ("%s: key auth worked, but server wants more authentication",
                 data->logname);
      break;
    case SSH_AUTH_AGAIN:
      g_message ("%s: key auth failed: server asked for retry",
                 data->logname);
      break;
    default:
      msg = ssh_get_error (data->session);
      g_message ("%s: couldn't key authenticate: %s", data->logname, msg);
    }

  return rc;
}

static int
do_gss_auth (CockpitSshData *data)
{
  int rc;
  const gchar *msg;

  rc = ssh_userauth_gssapi (data->session);

  switch (rc)
    {
    case SSH_AUTH_SUCCESS:
      g_debug ("%s: gssapi auth succeeded", data->logname);
      break;
    case SSH_AUTH_DENIED:
      g_debug ("%s: gssapi auth failed", data->logname);
      break;
    case SSH_AUTH_PARTIAL:
      g_message ("%s: gssapi auth worked, but server wants more authentication",
                 data->logname);
      break;
    default:
      msg = ssh_get_error (data->session);
      g_message ("%s: couldn't authenticate: %s", data->logname, msg);
    }

  return rc;
}

static gboolean
has_password (CockpitSshData *data)
{
  if (data->auth_type == NULL &&
      data->initial_auth_data == NULL)
    {
      data->initial_auth_data = challenge_for_auth_data ("basic", &data->auth_type);
    }

  return (data->initial_auth_data != NULL &&
          (g_strcmp0 (data->auth_type, "basic") == 0 ||
           g_strcmp0 (data->auth_type, "password") == 0));
}

static const gchar *
cockpit_ssh_authenticate (CockpitSshData *data)
{
  const gchar *problem;
  gboolean have_final_result = FALSE;
  gchar *description;
  const gchar *msg;
  int rc;
  int methods_server;
  int methods_tried = 0;
  int methods_to_try = SSH_AUTH_METHOD_INTERACTIVE |
                       SSH_AUTH_METHOD_GSSAPI_MIC |
                       SSH_AUTH_METHOD_PUBLICKEY;

  problem = "authentication-failed";

  rc = ssh_userauth_none (data->session, NULL);
  if (rc == SSH_AUTH_ERROR)
    {
      g_message ("%s: server authentication handshake failed: %s",
                 data->logname, ssh_get_error (data->session));
      problem = "internal-error";
      goto out;
    }

  if (rc == SSH_AUTH_SUCCESS)
    {
      problem = NULL;
      goto out;
    }

  methods_server = ssh_userauth_list (data->session, NULL);

  /* If interactive isn't supported try password instead */
  if (!(methods_server & SSH_AUTH_METHOD_INTERACTIVE))
    {
      methods_to_try = methods_to_try | SSH_AUTH_METHOD_PASSWORD;
      methods_to_try = methods_to_try & ~SSH_AUTH_METHOD_INTERACTIVE;
    }

  while (methods_to_try != 0)
    {
      int (*auth_func)(CockpitSshData *data);
      const gchar *result_string;
      int method;
      gboolean has_creds = FALSE;

      if (methods_to_try & SSH_AUTH_METHOD_PUBLICKEY)
        {
          method = SSH_AUTH_METHOD_PUBLICKEY;
          if (g_strcmp0 (data->auth_type, "private-key") == 0)
            {
              auth_func = do_key_auth;
              has_creds = data->initial_auth_data != NULL;
            }
          else
            {
              auth_func = do_auto_auth;
              has_creds = TRUE;
            }
        }
      else if (methods_to_try & SSH_AUTH_METHOD_INTERACTIVE)
        {
          auth_func = do_interactive_auth;
          method = SSH_AUTH_METHOD_INTERACTIVE;
          has_creds = has_password(data);
        }
      else if (methods_to_try & SSH_AUTH_METHOD_PASSWORD)
        {
          auth_func = do_password_auth;
          method = SSH_AUTH_METHOD_PASSWORD;
          has_creds = has_password(data);
        }
      else
        {
          auth_func = do_gss_auth;
          method = SSH_AUTH_METHOD_GSSAPI_MIC;
          has_creds = TRUE;
        }

      methods_to_try = methods_to_try & ~method;

      if (!(methods_server & method))
        {
          result_string = "no-server-support";
        }
      else if (!has_creds)
        {
          result_string = "not-provided";
          methods_tried = methods_tried | method;
        }
      else
        {
          methods_tried = methods_tried | method;
          if (!have_final_result)
            {
              rc = auth_func (data);
              result_string = auth_result_string (rc);

              if (rc == SSH_AUTH_SUCCESS)
                {
                  have_final_result = TRUE;
                  problem = NULL;
                }
              else if (rc == SSH_AUTH_ERROR)
                {
                  have_final_result = TRUE;
                  msg = ssh_get_error (data->session);
                  g_message ("%s: couldn't authenticate: %s", data->logname, msg);

                  if (ssh_msg_is_disconnected (msg))
                    problem = "terminated";
                  else
                    problem = "internal-error";
                }
            }
          else
            {
              result_string = "not-tried";
            }
        }

        g_hash_table_insert (data->auth_results,
                             g_strdup (auth_method_description (method)),
                             g_strdup (result_string));
    }

  if (have_final_result)
    goto out;

  if (methods_tried == 0)
    {
      if (methods_server == 0)
        {
          g_message ("%s: server offered no authentication methods", data->logname);
        }
      else
        {
          description = auth_methods_line (methods_server);
          g_message ("%s: server offered unsupported authentication methods: %s",
                     data->logname, description);
          g_free (description);
        }
    }

out:
  return problem;
}

static gboolean
send_auth_reply (CockpitSshData *data,
                 const gchar *problem)
{
  GHashTableIter auth_iter;
  JsonObject *auth_json = NULL; // consumed by object
  JsonObject *object = NULL;
  gboolean ret;
  gpointer hkey;
  gpointer hvalue;
  object = json_object_new ();
  auth_json = json_object_new ();

  g_assert (problem != NULL);

  json_object_set_string_member (object, "command", "init");
  if (data->host_key)
    json_object_set_string_member (object, "host-key", data->host_key);
  if (data->host_fingerprint)
    json_object_set_string_member (object, "host-fingerprint", data->host_fingerprint);

  json_object_set_string_member (object, "problem", problem);
  if (data->problem_error)
    json_object_set_string_member (object, "error", data->problem_error);
  else
    json_object_set_string_member (object, "error", problem);

  if (data->auth_results)
    {
      g_hash_table_iter_init (&auth_iter, data->auth_results);
      while (g_hash_table_iter_next (&auth_iter, &hkey, &hvalue))
        json_object_set_string_member (auth_json, hkey, hvalue);
    }

  json_object_set_object_member (object, "auth-method-results", auth_json);
  ret = write_control_message (STDOUT_FILENO, object);
  json_object_unref (object);

  if (!ret)
    g_message ("couldn't write authorize message: %s", g_strerror (errno));

  return ret;
}

static gboolean
parse_host (const gchar *host,
            gchar **hostname,
            gchar **username,
            guint *port)
{
  GError *error = NULL;
  g_autoptr (GRegex) regex = g_regex_new ("^"
         "(?:(.+)@)?"         /* optional username */
         "(?|"                /* one of... */
           "\\[([^]@]+)\\]"     /* hostname in square brackets, no @ */
           "(?::([1-9][0-9]*))?"     /* optional port number */
         "|"                  /* or */
           "([^@:]+)"           /* hostname with no : or @ */
           "(?::([1-9][0-9]*))?"     /* optional port number */
         "|"                  /* or */
           "([^@]+)"            /* hostname with no @ but : (IPv6 address), and no port */
         ")"                  /* . */
       "$",
       0, 0, &error);
  g_assert_no_error (error);

  g_autoptr(GMatchInfo) info = NULL;

  if (g_regex_match (regex, host, 0, &info))
    {
      g_autofree gchar *port_str = g_match_info_fetch (info, 3);
      /* regexp makes sure that it's a positive number, so don't need much error checking */
      guint value = atoi (port_str ?: "");
      if (value < 65536)
        {
          *port = value;
        }
      else
        {
          g_message ("invalid port: %s", port_str);
          return FALSE;
        }

      *hostname = g_match_info_fetch (info, 2);

      *username = g_match_info_fetch (info, 1);
      if ((*username)[0] == '\0')
        {
          g_free (*username);
          *username = g_strdup (g_get_user_name ());
        }

      return TRUE;
    }
  else
    {
      g_message ("invalid host: %s", host);
      return FALSE;
    }
}

static gchar *
username_from_basic (const gchar *basic_data)
{
  gchar *user = NULL;
  gchar *password;

  password = cockpit_authorize_parse_basic (basic_data, &user);
  if (password)
    {
      cockpit_memory_clear (password, -1);
      free (password);
    }
  return user;
}

static const gchar*
cockpit_ssh_connect (CockpitSshData *data,
                     const gchar *host_arg,
                     ssh_channel *out_channel)
{
  const gchar *ignore_hostkey;
  gboolean host_is_whitelisted;
  const gchar *problem;
  g_autofree gchar *username = NULL;

  guint port = 0;
  gchar *host = NULL;

  ssh_channel channel;
  int rc;

  if (!parse_host (host_arg, &host, &data->username, &port))
    {
      problem = "no-host";
      goto out;
    }
  g_debug ("%s: host argument '%s', host '%s', username '%s', port '%u'", data->logname, host_arg, host, data->username, port);

  g_warn_if_fail (ssh_options_set (data->session, SSH_OPTIONS_HOST, host) == 0);
  g_warn_if_fail (ssh_options_parse_config (data->session, NULL) == 0);

  if (strrchr (host_arg, '@'))
    {
      g_warn_if_fail (ssh_options_set (data->session, SSH_OPTIONS_USER, data->username) == 0);
    }
  else if (ssh_options_get (data->session, SSH_OPTIONS_USER, &username) != 0)
    {
      /* User comes from auth message when using basic if it's not set in ssh config */
      if (g_strcmp0 (data->auth_type, "basic") == 0)
        {
          g_free (data->username);
          data->username = username_from_basic (data->initial_auth_data);
        }

      if (!data->username || *data->username == '\0')
        {
          g_message ("%s: No username provided", data->logname);
          problem = "authentication-failed";
          goto out;
        }
      g_warn_if_fail (ssh_options_set (data->session, SSH_OPTIONS_USER, data->username) == 0);
    }

  /* If the user specifies a port explicitly, overwrite the config */
  if (port != 0)
    g_warn_if_fail (ssh_options_set (data->session, SSH_OPTIONS_PORT, &port) == 0);

  /* Parsing the config might have changed the host or port */
  gchar *new_host;
  if (ssh_options_get (data->session, SSH_OPTIONS_HOST, &new_host) == 0)
    {
      g_free (host);
      host = new_host;
    }
  g_warn_if_fail (ssh_options_get_port (data->session, &port) == 0);

  /* This is a single host, for which we have been told to ignore the host key */
  ignore_hostkey = cockpit_conf_string (COCKPIT_CONF_SSH_SECTION, "host");
  if (!ignore_hostkey)
    ignore_hostkey = "127.0.0.1";
  host_is_whitelisted = g_str_equal (ignore_hostkey, host);

  if (!host_is_whitelisted)
    {
      problem = set_knownhosts_file (data, host, port);
      if (problem != NULL)
        goto out;
    }

  rc = ssh_connect (data->session);
  if (rc != SSH_OK)
    {
      g_message ("%s: %d couldn't connect: %s '%s' '%d'", data->logname, rc,
                 ssh_get_error (data->session), host, port);
      problem = "no-host";
      goto out;
    }

  g_debug ("%s: connected", data->logname);
  if (!host_is_whitelisted)
    {
      problem = verify_knownhost (data, host, port);
      if (problem != NULL)
        goto out;
    }

  /* The problem returned when auth failure */
  problem = cockpit_ssh_authenticate (data);
  if (problem != NULL)
    goto out;

  channel = ssh_channel_new (data->session);
  rc = ssh_channel_open_session (channel);
  if (rc != SSH_OK)
    {
      g_message ("%s: couldn't open session: %s", data->logname,
                 ssh_get_error (data->session));
      problem = "internal-error";
      goto out;
    }

  if (data->ssh_options->remote_peer)
    {
      /* Try to set the remote peer env var, this will
       * often fail as ssh servers have to be configured
       * to allow it.
       */
      rc = ssh_channel_request_env (channel, "COCKPIT_REMOTE_PEER",
                                    data->ssh_options->remote_peer);
      if (rc != SSH_OK)
        {
          g_debug ("%s: Couldn't set COCKPIT_REMOTE_PEER: %s",
                   data->logname,
                   ssh_get_error (data->session));
        }
    }

  g_debug ("%s: opened channel", data->logname);

  *out_channel = channel;
out:
  g_free (host);
  return problem;
}

static void
cockpit_ssh_data_free (CockpitSshData *data)
{
  if (data->initial_auth_data)
    {
      memset (data->initial_auth_data, 0, strlen (data->initial_auth_data));
      free (data->initial_auth_data);
    }

  g_free (data->host_key);
  if (data->host_fingerprint)
    ssh_string_free_char (data->host_fingerprint);

  if (data->auth_results)
    g_hash_table_destroy (data->auth_results);

  g_free (data->problem_error);
  g_free (data->conversation);
  g_free (data->username);
  g_free (data->ssh_options);
  g_free (data->user_known_hosts);
  g_free (data->auth_type);
  g_strfreev (data->env);
  g_free (data);
}


#define COCKPIT_SSH_RELAY(o)    (G_TYPE_CHECK_INSTANCE_CAST ((o), COCKPIT_TYPE_SSH_RELAY, CockpitSshRelay))

struct  _CockpitSshRelay {
  GObject parent_instance;

  CockpitSshData *ssh_data;

  gboolean sent_disconnect;
  gboolean received_eof;
  gboolean received_frame;
  gboolean received_close;
  gboolean received_exit;

  gboolean sent_close;
  gboolean sent_eof;

  guint exit_code;
  guint sig_read;
  guint sig_close;
  gboolean pipe_closed;
  CockpitPipe *pipe;

  GQueue *queue;
  gsize partial;

  gchar *logname;
  gchar *connection_string;

  ssh_session session;
  ssh_channel channel;
  ssh_event event;

  GSource *io;

  struct ssh_channel_callbacks_struct channel_cbs;
};

struct _CockpitSshRelayClass {
  GObjectClass parent_class;
};

static guint sig_disconnect = 0;

enum {
  PROP_0,
  PROP_CONNECTION_STRING
};

G_DEFINE_TYPE (CockpitSshRelay, cockpit_ssh_relay, G_TYPE_OBJECT);

static void
cockpit_ssh_relay_dispose (GObject *object)
{
  CockpitSshRelay *self = COCKPIT_SSH_RELAY (object);

  g_assert (self->ssh_data == NULL);

  if (self->sig_read > 0)
    g_signal_handler_disconnect (self->pipe, self->sig_read);
  self->sig_read = 0;

  if (self->sig_close > 0)
    g_signal_handler_disconnect (self->pipe, self->sig_close);
  self->sig_close = 0;

  if (self->io)
    g_source_destroy (self->io);

  G_OBJECT_CLASS (cockpit_ssh_relay_parent_class)->dispose (object);
}

static void
cockpit_ssh_relay_finalize (GObject *object)
{
  CockpitSshRelay *self = COCKPIT_SSH_RELAY (object);

  if (self->pipe)
    g_object_unref (self->pipe);

  g_queue_free_full (self->queue, (GDestroyNotify)g_bytes_unref);

  if (self->event)
    ssh_event_free (self->event);

  /* libssh channels like to hang around even after they're freed */
  if (self->channel)
    memset (&self->channel_cbs, 0, sizeof (self->channel_cbs));

  g_free (self->logname);
  g_free (self->connection_string);

  if (self->io)
    g_source_unref (self->io);

  ssh_disconnect (self->session);
  ssh_free (self->session);

  G_OBJECT_CLASS (cockpit_ssh_relay_parent_class)->finalize (object);
}

static gboolean
emit_disconnect (gpointer user_data)
{
  CockpitSshRelay *self = user_data;

  if (!self->sent_disconnect)
    {
      self->sent_disconnect = TRUE;
      g_signal_emit (self, sig_disconnect, 0);
    }

  return FALSE;
}

static void
cockpit_relay_disconnect (CockpitSshRelay *self,
                          const gchar *problem)
{
  if (self->ssh_data)
    {
      send_auth_reply (self->ssh_data, problem ? problem : exit_code_problem (self->exit_code));
      cockpit_ssh_data_free (self->ssh_data);
      self->ssh_data = NULL;
    }

  /* libssh channels like to hang around even after they're freed */
  if (self->channel)
      memset (&self->channel_cbs, 0, sizeof (self->channel_cbs));
  self->channel = NULL;

  if (self->io)
    g_source_destroy (self->io);

  g_timeout_add (0, emit_disconnect, self);
}

static int
on_channel_data (ssh_session session,
                 ssh_channel channel,
                 void *data,
                 uint32_t len,
                 int is_stderr,
                 void *userdata)
{
  CockpitSshRelay *self = userdata;
  guint32 size, i;
  gint ret = 0;
  GBytes *bytes = NULL;
  guint8 *bdata = data;

  if (!self->received_frame && !is_stderr)
    {
      size = 0;
      for (i = 0; i < len; i++)
        {
          /* Check invalid characters, prevent integer overflow, limit max length */
          if (i > 7 || bdata[i] < '0' || bdata[i] > '9')
            break;
          size *= 10;
          size += bdata[i] - '0';
        }

      /* If we don't have enough data return 0 bytes processed
       * so that this data will be included in the next callback
       */
      if (i == len)
          goto out;

      /*
       * So we may be talking to a process that's not cockpit-bridge. How does
       * that happen? ssh always executes commands inside of a shell ... and
       * bash prints its 'cockpit-bridge: not found' message on stdout (!)
       *
       * So we degrade gracefully in this case, and start to treat output as
       * error output.
       */
      if (bdata[i] != '\n')
        {
          self->exit_code = NO_COCKPIT;
        }
      else
        {
          self->received_frame = TRUE;
          cockpit_ssh_data_free (self->ssh_data);
          self->ssh_data = NULL;
        }
    }

  if (is_stderr || self->exit_code == NO_COCKPIT)
    {
      g_printerr ("%.*s", (int) len, bdata);
      ret = len;
    }
  else if (self->received_frame)
    {
      if (!self->pipe_closed)
        {
          bytes = g_bytes_new (bdata, len);
          cockpit_pipe_write (self->pipe, bytes);
          g_bytes_unref (bytes);
          ret = len;
        }
      else
        {
          g_debug ("%s: dropping %d incoming bytes, pipe is closed", self->logname, len);
          ret = len;
        }
    }
out:
  return ret;
}

static void
on_channel_eof (ssh_session session,
                ssh_channel channel,
                void *userdata)
{
  CockpitSshRelay *self = userdata;
  g_debug ("%s: received eof", self->logname);
  self->received_eof = TRUE;
}

static void
on_channel_close (ssh_session session,
                  ssh_channel channel,
                  void *userdata)
{
  CockpitSshRelay *self = userdata;
  g_debug ("%s: received close", self->logname);
  self->received_close = TRUE;
}

static void
on_channel_exit_signal (ssh_session session,
                        ssh_channel channel,
                        const char *signal,
                        int core,
                        const char *errmsg,
                        const char *lang,
                        void *userdata)
{
  CockpitSshRelay *self = userdata;
  guint exit_code;
  g_return_if_fail (signal != NULL);
  self->received_exit = TRUE;

  if (g_ascii_strcasecmp (signal, "TERM") == 0 ||
      g_ascii_strcasecmp (signal, "Terminated") == 0)
    {
      g_debug ("%s: received TERM signal", self->logname);
      exit_code = TERMINATED;
    }
  else
    {
      g_warning ("%s: bridge killed%s%s%s%s", self->logname,
                 signal ? " by signal " : "", signal ? signal : "",
                 errmsg && errmsg[0] ? ": " : "", errmsg ? errmsg : "");
      exit_code = INTERNAL_ERROR;
    }

  if (!self->exit_code)
    self->exit_code = exit_code;

  cockpit_relay_disconnect (self, NULL);
}

static void
on_channel_signal (ssh_session session,
                   ssh_channel channel,
                   const char *signal,
                   void *userdata)
{
  /*
   * HACK: So it looks like libssh is buggy and is confused about
   * the difference between "exit-signal" and "signal" in section 6.10
   * of the RFC. Accept signal as a usable substitute
   */
  if (g_ascii_strcasecmp (signal, "TERM") == 0 ||
      g_ascii_strcasecmp (signal, "Terminated") == 0)
    on_channel_exit_signal (session, channel, signal, 0, NULL, NULL, userdata);
}

static void
on_channel_exit_status (ssh_session session,
                        ssh_channel channel,
                        int exit_status,
                        void *userdata)
{
  CockpitSshRelay *self = userdata;
  guint exit_code = 0;

  self->received_exit = TRUE;
  if (exit_status == 127)
    {
      g_debug ("%s: received exit status %d", self->logname, exit_status);
      exit_code = NO_COCKPIT;        /* cockpit-bridge not installed */
    }
  else if (!self->received_frame)
    {
      g_message ("%s: spawning remote bridge failed with %d status", self->logname, exit_status);
      exit_code = NO_COCKPIT;
    }
  else if (exit_status)
    {
      g_message ("%s: remote bridge exited with %d status", self->logname, exit_status);
      exit_code = INTERNAL_ERROR;
    }
  if (!self->exit_code && exit_code)
    self->exit_code = exit_code;

  cockpit_relay_disconnect (self, NULL);
}

static gboolean
dispatch_queue (CockpitSshRelay *self)
{
  GBytes *block;
  const guchar *data;
  const gchar *msg;
  gsize length;
  gsize want;
  int rc;

  if (self->sent_eof)
    return FALSE;
  if (self->received_close)
    return FALSE;

  for (;;)
    {
      block = g_queue_peek_head (self->queue);
      if (!block)
        return FALSE;

      data = g_bytes_get_data (block, &length);
      g_assert (self->partial <= length);

      want = length - self->partial;
      rc = ssh_channel_write (self->channel, data + self->partial, want);
      if (rc < 0)
        {
          msg = ssh_get_error (self->session);
          if (ssh_get_error_code (self->session) == SSH_REQUEST_DENIED)
            {
              g_debug ("%s: couldn't write: %s", self->logname, msg);
              return FALSE;
            }
          else if (ssh_msg_is_disconnected (msg))
            {
              g_message ("%s: couldn't write: %s", self->logname, msg);
              self->received_close = TRUE;
              self->received_eof = TRUE;
              return FALSE;
            }
          else
            {
              g_warning ("%s: couldn't write: %s", self->logname, msg);
              return FALSE;
            }
          break;
        }

      if (rc == want)
        {
          g_debug ("%s: wrote %d bytes", self->logname, rc);
          g_queue_pop_head (self->queue);
          g_bytes_unref (block);
          self->partial = 0;
        }
      else
        {
          g_debug ("%s: wrote %d of %d bytes", self->logname, rc, (int)want);
          g_return_val_if_fail (rc < want, FALSE);
          self->partial += rc;
          if (rc == 0)
            break;
        }
    }

  return TRUE;
}

static void
dispatch_close (CockpitSshRelay *self)
{
  g_assert (!self->sent_close);

  switch (ssh_channel_close (self->channel))
    {
    case SSH_AGAIN:
      g_debug ("%s: will send close later", self->logname);
      break;
    case SSH_OK:
      g_debug ("%s: sent close", self->logname);
      self->sent_close = TRUE;
      break;
    default:
      if (ssh_get_error_code (self->session) == SSH_REQUEST_DENIED)
        {
          g_debug ("%s: couldn't send close: %s", self->logname,
                   ssh_get_error (self->session));
          self->sent_close = TRUE; /* channel is already closed */
        }
      else
        {
          g_warning ("%s: couldn't send close: %s", self->logname,
                     ssh_get_error (self->session));
          self->received_exit = TRUE;
          if (!self->exit_code)
            self->exit_code = INTERNAL_ERROR;
          cockpit_relay_disconnect (self, NULL);
        }
      break;
    }
}

static void
dispatch_eof (CockpitSshRelay *self)
{
  g_assert (!self->sent_eof);

  switch (ssh_channel_send_eof (self->channel))
    {
    case SSH_AGAIN:
      g_debug ("%s: will send eof later", self->logname);
      break;
    case SSH_OK:
      g_debug ("%s: sent eof", self->logname);
      self->sent_eof = TRUE;
      break;
    default:
      if (ssh_get_error_code (self->session) == SSH_REQUEST_DENIED)
        {
          g_debug ("%s: couldn't send eof: %s", self->logname,
                   ssh_get_error (self->session));
          self->sent_eof = TRUE; /* channel is already closed */
        }
      else
        {
          g_warning ("%s: couldn't send eof: %s", self->logname,
                     ssh_get_error (self->session));
          self->received_exit = TRUE;
          if (!self->exit_code)
            self->exit_code = INTERNAL_ERROR;
          cockpit_relay_disconnect (self, NULL);
        }
      break;
    }
}

static void
on_pipe_read (CockpitPipe *pipe,
              GByteArray *input,
              gboolean end_of_data,
              gpointer user_data)
{
  CockpitSshRelay *self = user_data;
  GByteArray *buf = NULL;

  buf = cockpit_pipe_get_buffer (pipe);
  g_byte_array_ref (buf);

  if (!self->sent_eof && !self->received_close && buf->len > 0)
    {
      g_debug ("%s: queued %d bytes", self->logname, buf->len);
      g_queue_push_tail (self->queue, g_byte_array_free_to_bytes (buf));
    }
  else
    {
      g_debug ("%s: dropping %d bytes", self->logname, buf->len);
      g_byte_array_free (buf, TRUE);
    }

  if (end_of_data)
    cockpit_pipe_close (pipe, NULL);
}

static void
on_pipe_close (CockpitPipe *pipe,
               const gchar *problem,
               gpointer user_data)
{
  CockpitSshRelay *self = user_data;

  self->pipe_closed = TRUE;
  // Pipe closing before data was received doesn't mean no-cockpit
  self->received_frame = TRUE;

  if (!self->received_eof)
    dispatch_eof (self);
}

typedef struct {
  GSource source;
  GPollFD pfd;
  CockpitSshRelay *relay;
} CockpitSshSource;

static gboolean
cockpit_ssh_source_check (GSource *source)
{
  CockpitSshSource *cs = (CockpitSshSource *)source;
  return (cs->pfd.events & cs->pfd.revents) != 0;
}

static gboolean
cockpit_ssh_source_prepare (GSource *source,
                            gint *timeout)
{
  CockpitSshSource *cs = (CockpitSshSource *)source;
  CockpitSshRelay *self = cs->relay;
  gint status;

  *timeout = 1;

  status = ssh_get_status (self->session);

  cs->pfd.revents = 0;
  cs->pfd.events = G_IO_IN | G_IO_ERR | G_IO_NVAL | G_IO_HUP;

  /* libssh has something in its buffer: want to write */
  if (status & SSH_WRITE_PENDING)
    cs->pfd.events |= G_IO_OUT;

  /* We have something in our queue: want to write */
  else if (!g_queue_is_empty (self->queue))
    cs->pfd.events |= G_IO_OUT;

  /* We are closing and need to send eof: want to write */
  else if (self->pipe_closed && !self->sent_eof)
    cs->pfd.events |= G_IO_OUT;

  /* Need to reply to an EOF or close */
  if ((self->received_eof && self->sent_eof && !self->sent_close) ||
      (self->received_close && !self->sent_close))
    cs->pfd.events |= G_IO_OUT;

  return cockpit_ssh_source_check (source);
}

static gboolean
cockpit_ssh_source_dispatch (GSource *source,
                             GSourceFunc callback,
                             gpointer user_data)
{
  CockpitSshSource *cs = (CockpitSshSource *)source;
  int rc;
  const gchar *msg;
  gboolean ret = TRUE;
  CockpitSshRelay *self = cs->relay;
  GIOCondition cond = cs->pfd.revents;

  if (cond & (G_IO_HUP | G_IO_ERR))
    {
      if (self->sent_close || self->sent_eof)
        {
          self->received_eof = TRUE;
          self->received_close = TRUE;
        }
    }

  if (self->received_exit)
    return FALSE;

  g_return_val_if_fail ((cond & G_IO_NVAL) == 0, FALSE);

  /*
   * HACK: Yes this is another poll() call. The async support in
   * libssh is quite hacky right now.
   *
   * https://red.libssh.org/issues/155
   */
  rc = ssh_event_dopoll (self->event, 0);
  switch (rc)
    {
    case SSH_OK:
    case SSH_AGAIN:
      break;
    case SSH_ERROR:
      msg = ssh_get_error (self->session);

      /*
       * HACK: There doesn't seem to be a way to get at the original socket errno
       * here. So we have to screen scrape.
       *
       * https://red.libssh.org/issues/158
       */
      if (ssh_msg_is_disconnected (msg))
        {
          g_debug ("%s: failed to process channel: %s", self->logname, msg);
          self->received_exit = TRUE;
          if (!self->exit_code)
            self->exit_code = TERMINATED;
        }
      else
        {
          g_message ("%s: failed to process channel: %s", self->logname, msg);
          self->received_exit = TRUE;
          if (!self->exit_code)
            self->exit_code = INTERNAL_ERROR;
        }
      ret = FALSE;
      break;
    default:
      self->received_exit = TRUE;
      if (!self->exit_code)
        self->exit_code = INTERNAL_ERROR;
      g_critical ("%s: ssh_event_dopoll() returned %d", self->logname, rc);
      ret = FALSE;
    }

  if (!ret)
    goto out;

  if (cond & G_IO_ERR)
    {
      g_message ("%s: error reading from ssh", self->logname);
      ret = FALSE;
      self->received_exit = TRUE;
      if (!self->exit_code)
        self->exit_code = DISCONNECTED;
      goto out;
    }

  if (cond & G_IO_OUT)
    {
      if (!dispatch_queue (self) && self->pipe_closed && !self->sent_eof)
        dispatch_eof (self);
      if (self->received_eof && self->sent_eof && !self->sent_close)
        dispatch_close (self);
      if (self->received_eof && !self->received_close && !self->sent_close)
        dispatch_close (self);
    }

out:
  if (self->received_exit)
    cockpit_relay_disconnect (self, NULL);
  return ret;
}

static GSource *
cockpit_ssh_relay_start_source (CockpitSshRelay *self) {
  static GSourceFuncs source_funcs = {
    cockpit_ssh_source_prepare,
    cockpit_ssh_source_check,
    cockpit_ssh_source_dispatch,
    NULL,
  };
  GSource *source = g_source_new (&source_funcs, sizeof (CockpitSshSource));
  CockpitSshSource *cs = (CockpitSshSource *)source;
  cs->relay = self;
  cs->pfd.fd = ssh_get_fd (self->session);
  g_source_add_poll (source, &cs->pfd);
  g_source_attach (source, g_main_context_default ());

  return source;
}

static void
cockpit_ssh_relay_start (CockpitSshRelay *self)
{
  const gchar *problem;
  int in;
  int out;
  int rc;

  static struct ssh_channel_callbacks_struct channel_cbs = {
    .channel_data_function = on_channel_data,
    .channel_eof_function = on_channel_eof,
    .channel_close_function = on_channel_close,
    .channel_signal_function = on_channel_signal,
    .channel_exit_signal_function = on_channel_exit_signal,
    .channel_exit_status_function = on_channel_exit_status,
  };

  self->ssh_data->initial_auth_data = challenge_for_auth_data ("*", &self->ssh_data->auth_type);

  problem = cockpit_ssh_connect (self->ssh_data, self->connection_string, &self->channel);
  if (problem)
    goto out;

  self->event = ssh_event_new ();
  memcpy (&self->channel_cbs, &channel_cbs, sizeof (channel_cbs));
  self->channel_cbs.userdata = self;
  ssh_callbacks_init (&self->channel_cbs);
  ssh_set_channel_callbacks (self->channel, &self->channel_cbs);
  ssh_set_blocking (self->session, 0);
  ssh_event_add_session (self->event, self->session);

  in = dup (0);
  g_assert (in >= 0);
  out = dup (1);
  g_assert (out >= 0);

  self->pipe = g_object_new (COCKPIT_TYPE_PIPE,
                             "in-fd", in,
                             "out-fd", out,
                             "name", self->logname,
                             NULL);
  self->sig_read = g_signal_connect (self->pipe,
                                      "read",
                                      G_CALLBACK (on_pipe_read),
                                      self);
  self->sig_close = g_signal_connect (self->pipe,
                                      "close",
                                      G_CALLBACK (on_pipe_close),
                                      self);

  for (rc = SSH_AGAIN; rc == SSH_AGAIN; )
    rc = ssh_channel_request_exec (self->channel, self->ssh_data->ssh_options->command);

  if (rc != SSH_OK)
    {
      g_message ("%s: couldn't execute command: %s: %s", self->logname,
                 self->ssh_data->ssh_options->command,
                 ssh_get_error (self->session));
      problem = "internal-error";
      goto out;
    }

  self->io = cockpit_ssh_relay_start_source (self);

out:
  if (problem)
    {
      self->exit_code = AUTHENTICATION_FAILED;
      cockpit_relay_disconnect (self, problem);
    }
}

static void
cockpit_ssh_relay_init (CockpitSshRelay *self)
{
  const gchar *debug;

  ssh_init ();

  self->queue = g_queue_new ();
  debug = g_getenv ("G_MESSAGES_DEBUG");

  if (debug && (strstr (debug, "libssh") || g_strcmp0 (debug, "all") == 0))
    ssh_set_log_level (SSH_LOG_FUNCTIONS);
}

static void
cockpit_ssh_relay_set_property (GObject *obj,
                                guint prop_id,
                                const GValue *value,
                                GParamSpec *pspec)
{
  CockpitSshRelay *self = COCKPIT_SSH_RELAY (obj);

  switch (prop_id)
    {
    case PROP_CONNECTION_STRING:
      self->connection_string = g_value_dup_string (value);
      self->logname = g_strdup_printf ("cockpit-ssh %s", self->connection_string);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (obj, prop_id, pspec);
      break;
    }
}

static void
cockpit_ssh_relay_constructed (GObject *object)
{
  CockpitSshRelay *self = COCKPIT_SSH_RELAY (object);

  G_OBJECT_CLASS (cockpit_ssh_relay_parent_class)->constructed (object);

  self->session = ssh_new ();
  self->ssh_data = g_new0 (CockpitSshData, 1);
  self->ssh_data->env = g_get_environ ();
  self->ssh_data->session = self->session;
  self->ssh_data->logname = self->logname;
  self->ssh_data->auth_results = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
  self->ssh_data->ssh_options = cockpit_ssh_options_from_env (self->ssh_data->env);
  self->ssh_data->user_known_hosts = g_build_filename (g_get_home_dir (), ".ssh/known_hosts", NULL);
}

static void
authorize_logger (const char *data)
{
  g_message ("%s", data);
}

static void
cockpit_ssh_relay_class_init (CockpitSshRelayClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  object_class->dispose = cockpit_ssh_relay_dispose;
  object_class->finalize = cockpit_ssh_relay_finalize;
  object_class->constructed = cockpit_ssh_relay_constructed;
  object_class->set_property = cockpit_ssh_relay_set_property;

  g_object_class_install_property (object_class, PROP_CONNECTION_STRING,
         g_param_spec_string ("connection-string", NULL, NULL, "localhost",
                              G_PARAM_WRITABLE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS));

  sig_disconnect = g_signal_new ("disconnect", COCKPIT_TYPE_SSH_RELAY,
                                 G_SIGNAL_RUN_LAST, 0, NULL, NULL, NULL,
                                 G_TYPE_NONE, 0);

  cockpit_authorize_logger (authorize_logger, 0);
}

CockpitSshRelay *
cockpit_ssh_relay_new (const gchar *connection_string)
{

  CockpitSshRelay *self = g_object_new (COCKPIT_TYPE_SSH_RELAY,
                                        "connection-string", connection_string,
                                        NULL);
  cockpit_ssh_relay_start (self);
  return self;
}

gint
cockpit_ssh_relay_result (CockpitSshRelay* self)
{
  return self->exit_code;
}
