/* Copyright © 2005-2007  Roger Leigh <rleigh@debian.org>
 *
 * schroot is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * schroot 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 *********************************************************************/

#include <config.h>

#include "sbuild-auth-pam.h"
#include "sbuild-auth-pam-conv.h"
#include "sbuild-feature.h"

#include <cassert>
#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <sstream>

#include <syslog.h>

#include <boost/format.hpp>

using std::cerr;
using std::endl;
using boost::format;
using namespace sbuild;

#if defined(__LINUX_PAM__)
#define PAM_TEXT_DOMAIN "Linux-PAM"
#elif defined(__sun__)
#define PAM_TEXT_DOMAIN "SUNW_OST_SYSOSPAM"
#endif

namespace
{

  /* This is the glue to link PAM user interaction with auth_pam_conv. */
  int
  auth_pam_conv_hook (int                        num_msg,
                      const struct pam_message **msgm,
                      struct pam_response      **response,
                      void                      *appdata_ptr)
  {
    log_debug(DEBUG_NOTICE) << "PAM conversation hook started" << endl;

    try
      {
        if (appdata_ptr == 0)
          return PAM_CONV_ERR;

        auth_pam_conv *conv = static_cast<auth_pam_conv *>(appdata_ptr);
        assert (conv != 0);

        log_debug(DEBUG_INFO) << "Found PAM conversation handler" << endl;

        /* Construct a message vector */
        auth_pam_conv::message_list messages;
        for (int i = 0; i < num_msg; ++i)
          {
            const struct pam_message *source = msgm[i];

            auth_pam_message
              message(static_cast<auth_pam_message::message_type>(source->msg_style),
                      source->msg);

            /* Replace PAM prompt */
            if (message.message == dgettext(PAM_TEXT_DOMAIN, "Password: ") ||
                message.message == dgettext(PAM_TEXT_DOMAIN, "Password:"))
              {
                std::string user = "unknown"; // Set in case auth is void
                std::shared_ptr<auth_pam> auth = conv->get_auth();
                assert(auth && auth.get() != 0); // Check auth is not void
                if (auth && auth.get() != 0)
                  user = auth->get_user();
                format fmt(_("[schroot] password for %1%: "));
                fmt % user;
                message.message = fmt.str();
              }

            messages.push_back(message);
          }

        log_debug(DEBUG_INFO) << "Set PAM conversation message vector" << endl;

        /* Do the conversation; an exception will be thrown on failure */
        conv->conversation(messages);

        log_debug(DEBUG_INFO) << "Run PAM conversation" << endl;

        /* Copy response into **reponse */
        struct pam_response *reply =
          static_cast<struct pam_response *>
          (malloc(sizeof(struct pam_response) * num_msg));

        for (int i = 0; i < num_msg; ++i)
          {
            reply[i].resp_retcode = 0;
            reply[i].resp = strdup(messages[i].response.c_str());
          }

        *response = reply;
        reply = 0;

        log_debug(DEBUG_INFO) << "Set PAM conversation reply" << endl;

        return PAM_SUCCESS;
      }
    catch (std::exception const& e)
      {
        log_exception_error(e);
      }
    catch (...)
      {
        log_error() << _("An unknown exception occurred") << endl;
      }

    return PAM_CONV_ERR;
  }

  sbuild::feature feature_devlock("PAM",
                                  N_("Pluggable Authentication Modules"));
}

auth_pam::auth_pam (std::string const& service_name):
  auth(service_name),
  pam(0),
  conv()
{
}

auth_pam::~auth_pam ()
{
  // Shutdown PAM.
  try
    {
      stop();
    }
  catch (error const& e)
    {
      log_exception_error(e);
    }
}

auth::ptr
auth_pam::create (std::string const& service_name)
{
  return ptr(new auth_pam(service_name));
}

environment
auth_pam::get_auth_environment () const
{
  return environment(pam_getenvlist(this->pam));
}

auth_pam_conv::ptr&
auth_pam::get_conv ()
{
  return this->conv;
}

void
auth_pam::set_conv (auth_pam_conv::ptr& conv)
{
  this->conv = conv;
}

void
auth_pam::start ()
{
  assert(!this->user.empty());

  if (this->pam != 0)
    {
      log_debug(DEBUG_CRITICAL)
        << "pam_start FAIL (already initialised)" << endl;
      throw error("Init PAM", PAM_DOUBLE_INIT);
    }

  struct pam_conv conv_hook =
    {
      auth_pam_conv_hook,
      reinterpret_cast<void *>(this->conv.get())
    };

  int pam_status;

  if ((pam_status =
       pam_start(this->service.c_str(), this->user.c_str(),
                 &conv_hook, &this->pam)) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_start FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_start OK" << endl;
}

void
auth_pam::stop ()
{
  if (this->pam) // PAM must be initialised
  {
    int pam_status;

    if ((pam_status =
         pam_end(this->pam, PAM_SUCCESS)) != PAM_SUCCESS)
      {
        log_debug(DEBUG_WARNING) << "pam_end FAIL" << endl;
        throw error(PAM_END);
      }

    this->pam = 0;
    log_debug(DEBUG_NOTICE) << "pam_end OK" << endl;
  }
}

void
auth_pam::authenticate (status auth_status)
{
  assert(!this->user.empty());
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_set_item(this->pam, PAM_RUSER, this->ruser.c_str())) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_set_item (PAM_RUSER) FAIL" << endl;
      throw error(_("Set RUSER"), PAM, pam_strerror(pam_status));
    }

  long hl = 256; /* sysconf(_SC_HOST_NAME_MAX); BROKEN with Debian libc6 2.3.2.ds1-22 */

  char *hostname = new char[hl];
  try
    {
      if (gethostname(hostname, hl) != 0)
        {
          log_debug(DEBUG_CRITICAL) << "gethostname FAIL" << endl;
          throw error(HOSTNAME, strerror(errno));
        }

      if ((pam_status =
           pam_set_item(this->pam, PAM_RHOST, hostname)) != PAM_SUCCESS)
        {
          log_debug(DEBUG_WARNING) << "pam_set_item (PAM_RHOST) FAIL" << endl;
          throw error(_("Set RHOST"), PAM, pam_strerror(pam_status));
        }
    }
  catch (error const& e)
    {
      delete[] hostname;
      hostname = 0;
      throw;
    }
  delete[] hostname;
  hostname = 0;

  const char *tty = ttyname(STDIN_FILENO);
  if (tty)
    {
      if ((pam_status =
           pam_set_item(this->pam, PAM_TTY, tty)) != PAM_SUCCESS)
        {
          log_debug(DEBUG_WARNING) << "pam_set_item (PAM_TTY) FAIL" << endl;
          throw error(_("Set TTY"), PAM, pam_strerror(pam_status));
        }
    }

  /* Authenticate as required. */
  switch (auth_status)
    {
    case STATUS_NONE:
      if ((pam_status = pam_set_item(this->pam, PAM_USER, this->user.c_str()))
          != PAM_SUCCESS)
        {
          log_debug(DEBUG_WARNING) << "pam_set_item (PAM_USER) FAIL" << endl;
          throw error(_("Set USER"), PAM, pam_strerror(pam_status));
        }
      break;

    case STATUS_USER:
      if ((pam_status = pam_authenticate(this->pam, 0)) != PAM_SUCCESS)
        {
          log_debug(DEBUG_INFO) << "pam_authenticate FAIL" << endl;
          syslog(LOG_AUTH|LOG_WARNING, "%s->%s Authentication failure",
                 this->ruser.c_str(), this->user.c_str());
          throw error(AUTHENTICATION, pam_strerror(pam_status));
        }
      log_debug(DEBUG_NOTICE) << "pam_authenticate OK" << endl;
      break;

    case STATUS_FAIL:
        {
          log_debug(DEBUG_INFO) << "PAM auth premature FAIL" << endl;
          syslog(LOG_AUTH|LOG_WARNING,
                 "%s->%s Unauthorised",
                 this->ruser.c_str(), this->user.c_str());
          error e(AUTHORISATION);
          // TRANSLATORS: %1% = program name (PAM service name)
          std::string reason(_("You do not have permission to access the %1% service."));
          reason += '\n';
          reason += _("This failure will be reported.");
          format fmt(reason);
          fmt % this->service;
          e.set_reason(fmt.str());
          throw e;
        }
    default:
      break;
    }
}

void
auth_pam::setupenv ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  environment minimal(get_minimal_environment());

  // Move into PAM environment.
  for (environment::const_iterator cur = minimal.begin();
       cur != minimal.end();
       ++cur)
    {
      std::string env_string = cur->first + "=" + cur->second;
      if ((pam_status =
           pam_putenv(this->pam, env_string.c_str())) != PAM_SUCCESS)
        {
          log_debug(DEBUG_WARNING) << "pam_putenv FAIL" << endl;
          throw error(PAM, pam_strerror(pam_status));
        }
      log_debug(DEBUG_INFO)
        << format("pam_putenv: set %1%=%2%") % cur->first % cur->second
        << endl;
    }

  log_debug(DEBUG_NOTICE) << "pam_putenv OK" << endl;
}

void
auth_pam::account ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_acct_mgmt(this->pam, 0)) != PAM_SUCCESS)
    {
      /* We don't handle changing expired passwords here, since we are
         not login or ssh. */
      log_debug(DEBUG_WARNING) << "pam_acct_mgmt FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_acct_mgmt OK" << endl;
}

void
auth_pam::cred_establish ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_setcred(this->pam, PAM_ESTABLISH_CRED)) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_setcred FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_setcred OK" << endl;

  const char *authuser = 0;
  const void *tmpcast = reinterpret_cast<const void *>(authuser);
  pam_get_item(this->pam, PAM_USER, &tmpcast);
  log_debug(DEBUG_INFO)
    << format("PAM authentication succeeded for user %1%") % authuser
    << endl;
}

void
auth_pam::cred_delete ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_setcred(this->pam, PAM_DELETE_CRED)) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_setcred (delete) FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_setcred (delete) OK" << endl;
}

void
auth_pam::open_session ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_open_session(this->pam, 0)) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_open_session FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_open_session OK" << endl;
}

void
auth_pam::close_session ()
{
  assert(this->pam != 0); // PAM must be initialised

  int pam_status;

  if ((pam_status =
       pam_close_session(this->pam, 0)) != PAM_SUCCESS)
    {
      log_debug(DEBUG_WARNING) << "pam_close_session FAIL" << endl;
      throw error(PAM, pam_strerror(pam_status));
    }

  log_debug(DEBUG_NOTICE) << "pam_close_session OK" << endl;
}

bool
auth_pam::is_initialised () const
{
  return this->pam != 0;
}

const char *
auth_pam::pam_strerror (int pam_error)
{
  assert(this->pam != 0); // PAM must be initialised

  return ::pam_strerror (this->pam, pam_error);
}