/* GNU Mailutils -- a suite of utilities for electronic mail
   Copyright (C) 2002-2021 Free Software Foundation, Inc.

   This library 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 3 of the License, or (at your option) any later version.

   This library 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 this library.  If not, see
   <http://www.gnu.org/licenses/>. */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#ifdef HAVE_SHADOW_H
# include <shadow.h>
#endif
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#ifdef HAVE_SECURITY_PAM_APPL_H
# include <security/pam_appl.h>
#endif
#ifdef HAVE_CRYPT_H
# include <crypt.h>
#endif
#include <mailutils/list.h>
#include <mailutils/errno.h>
#include <mailutils/iterator.h>
#include <mailutils/mailbox.h>
#include <mailutils/mu_auth.h>
#include <mailutils/nls.h>

char *mu_pam_service = PACKAGE;

#ifdef USE_LIBPAM
static struct mu_cfg_param mu_pam_param[] = {
  { "service", mu_c_string, &mu_pam_service, 0, NULL,
    N_("Set PAM service name."),
    N_("name") },
  { NULL }
};


#define COPY_STRING(s) (s) ? strdup(s) : NULL

static char *_pwd;
static char *_user;

#define overwrite_and_free(ptr)			\
  do						\
    {						\
      char *s = ptr;				\
      while (*s)				\
	*s++ = 0;				\
    }						\
  while (0)


#ifndef PAM_AUTHTOK_RECOVER_ERR
# define PAM_AUTHTOK_RECOVER_ERR PAM_CONV_ERR
#endif

static int
mu_pam_conv (int num_msg, const struct pam_message **msg,
	     struct pam_response **resp, void *appdata_ptr MU_ARG_UNUSED)
{
  int status = PAM_SUCCESS;
  int i;
  struct pam_response *reply = NULL;

  reply = calloc (num_msg, sizeof (*reply));
  if (!reply)
    return PAM_CONV_ERR;

  for (i = 0; i < num_msg && status == PAM_SUCCESS; i++)
    {
      switch (msg[i]->msg_style)
	{
	case PAM_PROMPT_ECHO_ON:
	  reply[i].resp_retcode = PAM_SUCCESS;
	  reply[i].resp = COPY_STRING (_user);
	  /* PAM frees resp */
	  break;

	case PAM_PROMPT_ECHO_OFF:
	  if (_pwd)
	    {
	      reply[i].resp_retcode = PAM_SUCCESS;
	      reply[i].resp = COPY_STRING (_pwd);
	      /* PAM frees resp */
	    }
	  else
	    status = PAM_AUTHTOK_RECOVER_ERR;
	  break;

	case PAM_TEXT_INFO:
	case PAM_ERROR_MSG:
	  reply[i].resp_retcode = PAM_SUCCESS;
	  reply[i].resp = NULL;
	  break;
 
	default:
	  status = PAM_CONV_ERR;
	}
    }
  if (status != PAM_SUCCESS)
    {
      for (i = 0; i < num_msg; i++)
	if (reply[i].resp)
	  {
	    switch (msg[i]->msg_style)
	      {
	      case PAM_PROMPT_ECHO_ON:
	      case PAM_PROMPT_ECHO_OFF:
		overwrite_and_free (reply[i].resp);
		break;
		
	      case PAM_ERROR_MSG:
	      case PAM_TEXT_INFO:
		free (reply[i].resp);
	      }
	  }
      free (reply);
    }
  else
    *resp = reply;
  return status;
}

static struct pam_conv PAM_conversation = { &mu_pam_conv, NULL };

int
mu_authenticate_pam (struct mu_auth_data **return_data MU_ARG_UNUSED,
		     const void *key,
		     void *func_data MU_ARG_UNUSED,
		     void *call_data)
{
  const struct mu_auth_data *auth_data = key;
  char *pass = call_data;
  pam_handle_t *pamh;
  int pamerror;

#define PAM_ERROR if (pamerror != PAM_SUCCESS) goto pam_errlab;

  if (!auth_data)
    return EINVAL;
  
  _user = (char *) auth_data->name;
  _pwd = pass;
  pamerror = pam_start (mu_pam_service, _user, &PAM_conversation, &pamh);
  PAM_ERROR;
  pamerror = pam_authenticate (pamh, 0);
  PAM_ERROR;
  pamerror = pam_acct_mgmt (pamh, 0);
  PAM_ERROR;
  pamerror = pam_setcred (pamh, PAM_ESTABLISH_CRED);
 pam_errlab:
  pam_end (pamh, PAM_SUCCESS);
  switch (pamerror)
    {
    case PAM_SUCCESS:
      return 0;
    case PAM_AUTH_ERR:
      return MU_ERR_AUTH_FAILURE;
    }
  return MU_ERR_FAILURE;
}

#else
# define mu_pam_param NULL
# define mu_authenticate_pam NULL
#endif

struct mu_auth_module mu_auth_pam_module = {
  .name = "pam",
  .handler = { [mu_auth_authenticate] = mu_authenticate_pam },
  .cfg = mu_pam_param
};