/*
   pam.c - pam module functions

   Copyright (C) 2009 Howard Chu
   Copyright (C) 2009, 2010 Arthur de Jong

   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 2.1 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, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301 USA
*/

#include "config.h"

#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>

/* these are defined (before including pam_modules.h) for staticly linking */
#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT
#define PAM_SM_SESSION
#define PAM_SM_PASSWORD

#include "common.h"
#include "compat/attrs.h"
#include "compat/pam_compat.h"

#ifdef HAVE_SECURITY_PAM_APPL_H
#include <security/pam_appl.h>
#endif /* HAVE_SECURITY_PAM_APPL_H */
#ifndef HAVE_PAM_PAM_MODULES_H
#include <security/pam_modules.h>
#ifdef HAVE_SECURITY_PAM_EXT_H
#include <security/pam_ext.h>
#endif /* HAVE_SECURITY_PAM_EXT_H */
#else /* not HAVE_PAM_PAM_MODULES_H */
#include <pam/pam_modules.h>
#endif /* not HAVE_PAM_PAM_MODULES_H */

/* the name we store our context under */
#define PLD_CTX "PAM_LDAPD_CTX"

/* some systems don't have LOG_AUTHPRIV */
#ifndef LOG_AUTHPRIV
#define LOG_AUTHPRIV LOG_AUTH
#endif /* not LOG_AUTHPRIV */


/* this struct represents the context that the PAM module keeps
   between calls */
struct pld_ctx {
  char *user;
  char *dn;
  char *tmpluser;
  char *authzmsg;
  char *oldpassword;
  int authok;
  int authz;
  int sessid;
  char buf[1024];
};

/* clear the context to all empty values */
static void ctx_clear(struct pld_ctx *ctx)
{
  if (ctx->user)
  {
    free(ctx->user);
    ctx->user=NULL;
  }
  if (ctx->oldpassword)
  {
    memset(ctx->oldpassword,0,strlen(ctx->oldpassword));
    free(ctx->oldpassword);
    ctx->oldpassword=NULL;
  }
  ctx->dn=NULL;
  ctx->tmpluser=NULL;
  ctx->authzmsg=NULL;
  ctx->authok=0;
  ctx->authz=0;
}

/* free the context (this is installed as handler into PAM) */
static void ctx_free(pam_handle_t *UNUSED(pamh),void *data,int UNUSED(err))
{
  struct pld_ctx *ctx=data;
  ctx_clear(ctx);
  free(ctx);
}

/* try to get the module's context, returns a PAM status code */
static int ctx_get(pam_handle_t *pamh,const char *username,struct pld_ctx **pctx)
{
  struct pld_ctx *ctx=NULL;
  int rc;
  /* try to get the context from PAM */
  rc=pam_get_data(pamh, PLD_CTX,(const void **)&ctx);
  if ((rc==PAM_SUCCESS)&&(ctx!=NULL))
  {
    /* if the user is different clear the context */
    if ((ctx->user!=NULL)&&(strcmp(ctx->user,username)!=0))
      ctx_clear(ctx);
  }
  else
  {
    /* allocate a new context */
    ctx=calloc(1,sizeof(struct pld_ctx));
    if (ctx==NULL)
      return PAM_BUF_ERR;
    ctx_clear(ctx);
    /* store the new context with the handler to free it */
    rc=pam_set_data(pamh,PLD_CTX,ctx,ctx_free);
    if (rc!=PAM_SUCCESS)
    {
      ctx_free(pamh,ctx,0);
      return rc;
    }
  }
  /* return the context */
  *pctx=ctx;
  return PAM_SUCCESS;
}

/* our PAM module configuration */
struct pld_cfg {
  int use_first_pass;
  int try_first_pass;
  int use_authtok;
  int no_warn;
  int ignore_unknown_user;
  int ignore_authinfo_unavail;
  int debug;
  uid_t minimum_uid;
};

static void parse_args(struct pld_cfg *cfg,int flags,int argc,const char **argv)
{
  int i;
  /* initialise config with defaults */
  cfg->use_first_pass=0;
  cfg->try_first_pass=0;
  cfg->use_authtok=0;
  cfg->no_warn=0;
  cfg->ignore_unknown_user=0;
  cfg->ignore_authinfo_unavail=0;
  cfg->debug=0;
  cfg->minimum_uid=0;
  /* go over arguments */
  for (i=0;i<argc;i++)
  {
    if (strcmp(argv[i],"use_first_pass")==0)
      cfg->use_first_pass=1;
    else if (strcmp(argv[i],"try_first_pass")==0)
      cfg->try_first_pass=1;
    else if (strcmp(argv[i],"use_authtok")==0)
      cfg->use_authtok=1;
    else if (strcmp(argv[i], "no_warn")==0)
      cfg->no_warn=1;
    else if (strcmp(argv[i],"ignore_unknown_user")==0)
      cfg->ignore_unknown_user=1;
    else if (strcmp(argv[i],"ignore_authinfo_unavail")==0)
      cfg->ignore_authinfo_unavail=1;
    else if (strcmp(argv[i],"debug")==0)
      cfg->debug=1;
    else if (strncmp(argv[i], "minimum_uid=", 12) == 0)
      cfg->minimum_uid=(uid_t)atoi(argv[i]+12);
    else
      syslog(LOG_AUTHPRIV|LOG_ERR,"unknown option: %s",argv[i]);
  }
  /* check flags */
  if (flags&PAM_SILENT)
    cfg->no_warn=1;
}

/* map a NSLCD PAM status code to a PAM status code */
static int nslcd2pam_rc(int rc)
{
#define map(i) case NSLCD_##i: return i;
  switch(rc) {
    map(PAM_SUCCESS);
    map(PAM_PERM_DENIED);
    map(PAM_AUTH_ERR);
    map(PAM_CRED_INSUFFICIENT);
    map(PAM_AUTHINFO_UNAVAIL);
    map(PAM_USER_UNKNOWN);
    map(PAM_MAXTRIES);
    map(PAM_NEW_AUTHTOK_REQD);
    map(PAM_ACCT_EXPIRED);
    map(PAM_SESSION_ERR);
    map(PAM_AUTHTOK_DISABLE_AGING);
    map(PAM_IGNORE);
    map(PAM_ABORT);
    default: return PAM_ABORT;
  }
}

/* perform an authentication call over nslcd */
static int nslcd_request_authc(struct pld_ctx *ctx,const char *username,
                               const char *service,const char *passwd)
{
  PAM_REQUEST(NSLCD_ACTION_PAM_AUTHC,
    /* write the request parameters */
    WRITE_STRING(fp,username);
    WRITE_STRING(fp,ctx->dn);
    WRITE_STRING(fp,service);
    WRITE_STRING(fp,passwd),
    /* read the result entry */
    READ_BUF_STRING(fp,ctx->tmpluser);
    READ_BUF_STRING(fp,ctx->dn);
    READ_PAM_CODE(fp,ctx->authok)
    READ_PAM_CODE(fp,ctx->authz)
    READ_BUF_STRING(fp,ctx->authzmsg);)
}

/* perform an authorisation call over nslcd */
static int nslcd_request_authz(struct pld_ctx *ctx,const char *username,
                               const char *service,const char *ruser,
                               const char *rhost,const char *tty)
{
  PAM_REQUEST(NSLCD_ACTION_PAM_AUTHZ,
    /* write the request parameters */
    WRITE_STRING(fp,username);
    WRITE_STRING(fp,ctx->dn);
    WRITE_STRING(fp,service);
    WRITE_STRING(fp,ruser);
    WRITE_STRING(fp,rhost);
    WRITE_STRING(fp,tty),
    /* read the result entry */
    READ_BUF_STRING(fp,ctx->tmpluser);
    READ_BUF_STRING(fp,ctx->dn);
    READ_PAM_CODE(fp,ctx->authz);
    READ_BUF_STRING(fp,ctx->authzmsg);)
}

/* do a session nslcd request (open or close) */
static int nslcd_request_sess(struct pld_ctx *ctx,int action,
                              const char *username,const char *service,
                              const char *tty, const char *rhost,
                              const char *ruser)
{
  PAM_REQUEST(action,
    /* write the request parameters */
    WRITE_STRING(fp,username);
    WRITE_STRING(fp,ctx->dn);
    WRITE_STRING(fp,service);
    WRITE_STRING(fp,tty);
    WRITE_STRING(fp,rhost);
    WRITE_STRING(fp,ruser);
    WRITE_INT32(fp,ctx->sessid),
    /* read the result entry */
    READ_INT32(fp,ctx->sessid))
}

/* do a password modification nslcd call */
static int nslcd_request_pwmod(struct pld_ctx *ctx,const char *username,
                               const char *service,const char *oldpasswd,
                               const char *newpasswd)
{
  PAM_REQUEST(NSLCD_ACTION_PAM_PWMOD,
    /* write the request parameters */
    WRITE_STRING(fp,username);
    WRITE_STRING(fp,ctx->dn);
    WRITE_STRING(fp,service);
    WRITE_STRING(fp,oldpasswd);
    WRITE_STRING(fp,newpasswd),
    /* read the result entry */
    READ_BUF_STRING(fp,ctx->tmpluser);
    READ_BUF_STRING(fp,ctx->dn);
    READ_PAM_CODE(fp,ctx->authz);
    READ_BUF_STRING(fp,ctx->authzmsg);)
}

/* PAM authentication check */
int pam_sm_authenticate(pam_handle_t *pamh,int flags,int argc,const char **argv)
{
  struct pld_cfg cfg;
  int rc;
  const char *username,*svc;
  char *passwd=NULL;
  int i;
  struct pld_ctx *ctx;
  struct passwd *pwd;
  /* parse module options */
  parse_args(&cfg,flags,argc,argv);
  /* get user name */
  rc=pam_get_user(pamh,(const char **)&username,NULL);
  if (rc!=PAM_SUCCESS)
    return rc;
  if ((username==NULL)||(username[0]=='\0'))
    return PAM_USER_UNKNOWN;
  /* check uid */
  if (cfg.minimum_uid>0)
  {
    pwd=pam_modutil_getpwnam(args->pamh,username);
    if ((pwd!=NULL)&&(pwd->pw_uid<cfg.minimum_uid))
      return cfg.ignore_unknown_user?PAM_IGNORE:PAM_USER_UNKNOWN;
  }
  /* get our context */
  rc=ctx_get(pamh,username,&ctx);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get service name */
  rc=pam_get_item(pamh,PAM_SERVICE,(const void **)&svc);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* try twice */
  for (i=0;i<2;i++)
  {
    if ((!cfg.try_first_pass)&&(!cfg.use_first_pass))
    {
      rc=pam_get_authtok(pamh,PAM_AUTHTOK,(const char **)&passwd,i==0?"Password: ":"LDAP Password: ");
      if (rc!=PAM_SUCCESS)
        return rc;
      /* exit loop after trying this password */
      i=2;
    }
    rc=pam_get_item(pamh,PAM_AUTHTOK,(const void **)&passwd);
    if (rc==PAM_SUCCESS)
    {
      rc=nslcd_request_authc(ctx,username,svc,passwd);
      if (rc==PAM_SUCCESS)
        rc=ctx->authok;
      if ((rc==PAM_AUTHINFO_UNAVAIL)&&cfg.ignore_authinfo_unavail)
        rc=PAM_IGNORE;
      else if ((rc==PAM_USER_UNKNOWN)&&cfg.ignore_unknown_user)
        rc=PAM_IGNORE;
    }
    if ((rc==PAM_SUCCESS)||(cfg.use_first_pass))
      break;
    cfg.try_first_pass=0;
  }
  /* save username */
  if (rc==PAM_SUCCESS) {
    ctx->user=strdup(username);
    /* if password change is required, save old password in context */
    if (ctx->authz==PAM_NEW_AUTHTOK_REQD)
      ctx->oldpassword=strdup(passwd);
  }
  /* update caller's idea of the user name */
  if ( (rc==PAM_SUCCESS) && ctx->tmpluser && ctx->tmpluser[0] &&
       (strcmp(ctx->tmpluser,username)!=0) ) {
    rc=pam_set_item(pamh,PAM_USER,ctx->tmpluser);
  }
  return rc;
}

/* called to update the authentication credentials */
int pam_sm_setcred(pam_handle_t UNUSED(*pamh),int UNUSED(flags),
                   int UNUSED(argc),const char UNUSED(**argv))
{
  /* we don't need to do anything here */
  return PAM_SUCCESS;
}

/* PAM authorisation check */
int pam_sm_acct_mgmt(pam_handle_t *pamh,int flags,int argc,const char **argv)
{
  struct pld_cfg cfg;
  int rc;
  const char *username,*svc,*ruser,*rhost,*tty;
  struct pld_ctx *ctx=NULL, ctx2;
  struct passwd *pwent;
  /* parse module options */
  parse_args(&cfg,flags,argc,argv);
  /* get user name */
  rc=pam_get_user(pamh,(const char **)&username,NULL);
  if (rc!=PAM_SUCCESS)
    return rc;
  if ((username==NULL)||(username[0]=='\0'))
    return PAM_USER_UNKNOWN;
  /* check uid */
  if (cfg.minimum_uid>0)
  {
    pwent=pam_modutil_getpwnam(args->pamh,username);
    if ((pwent!=NULL)&&(pwent->pw_uid<cfg.minimum_uid))
      return cfg.ignore_unknown_user?PAM_IGNORE:PAM_USER_UNKNOWN;
  }
  /* get our context */
  rc=ctx_get(pamh,username,&ctx);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get service name */
  rc=pam_get_item(pamh,PAM_SERVICE,(const void **)&svc);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get remote user name */
  rc=pam_get_item(pamh,PAM_RUSER,(const void **)&ruser);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get service host */
  rc=pam_get_item(pamh,PAM_RHOST,(const void **)&rhost);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get tty name */
  rc=pam_get_item(pamh,PAM_TTY,(const void **)&tty);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* call the function with a copy of the context to be able to keep the
     original context */
  ctx2.dn=ctx->dn;
  ctx2.user=ctx->user;
  rc=nslcd_request_authz(&ctx2,username,svc,ruser,rhost,tty);
  if ((rc==PAM_AUTHINFO_UNAVAIL)&&cfg.ignore_authinfo_unavail)
    rc=PAM_IGNORE;
  else if ((rc==PAM_USER_UNKNOWN)&&cfg.ignore_unknown_user)
    rc=PAM_IGNORE;
  if (rc!=PAM_SUCCESS)
  {
    if (rc!=PAM_IGNORE)
      if (!cfg.no_warn)
        pam_error(pamh,"LDAP authorization failed");
    return rc;
  }
  /* check the returned authorisation value */
  if (ctx2.authz!=PAM_SUCCESS)
  {
    if (!cfg.no_warn)
      pam_error(pamh,"%s",ctx2.authzmsg);
    return ctx2.authz;
  }
  /* check the original authorisation check from authentication */
  if (ctx->authz!=PAM_SUCCESS)
  {
    if (!cfg.no_warn)
      pam_error(pamh,"%s",ctx->authzmsg);
    return ctx->authz;
  }
  /* present any informational messages to the user */
  if ((ctx2.authzmsg!=NULL)&&(ctx2.authzmsg[0]!='\0')&&(!cfg.no_warn))
    pam_info(pamh,"%s",ctx2.authzmsg);
  if ((ctx->authzmsg!=NULL)&&(ctx->authzmsg[0]!='\0')&&(!cfg.no_warn))
    pam_info(pamh,"%s",ctx->authzmsg);
  return PAM_SUCCESS;
}

/* PAM session open/close calls */
static int pam_sm_session(pam_handle_t *pamh,int flags,int argc,
                          const char **argv,int action)
{
  struct pld_cfg cfg;
  int rc;
  const char *username;
  struct pld_ctx *ctx=NULL;
  const char *service=NULL,*tty=NULL,*rhost=NULL,*ruser=NULL;
  struct passwd *pwent;
  /* parse module options */
  parse_args(&cfg,flags,argc,argv);
  /* get user name */
  rc=pam_get_user(pamh,(const char **)&username,NULL);
  if (rc!=PAM_SUCCESS)
    return rc;
  if ((username==NULL)||(username[0]=='\0'))
    return PAM_USER_UNKNOWN;
  /* check uid */
  if (cfg.minimum_uid>0)
  {
    pwent=pam_modutil_getpwnam(args->pamh,username);
    if ((pwent!=NULL)&&(pwent->pw_uid<cfg.minimum_uid))
      return cfg.ignore_unknown_user?PAM_IGNORE:PAM_USER_UNKNOWN;
  }
  /* get our context */
  rc=ctx_get(pamh,username,&ctx);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* read PAM information */
  pam_get_item(pamh,PAM_SERVICE,(const void **)&service);
  pam_get_item(pamh,PAM_TTY,(const void **)&tty);
  pam_get_item(pamh,PAM_RHOST,(const void **)&rhost);
  pam_get_item(pamh,PAM_RUSER,(const void **)&ruser);
  /* do the nslcd request */
  rc=nslcd_request_sess(ctx,action,username,service,tty,rhost,ruser);
  if ((rc==PAM_AUTHINFO_UNAVAIL)&&cfg.ignore_authinfo_unavail)
    rc=PAM_IGNORE;
  else if ((rc==PAM_USER_UNKNOWN)&&cfg.ignore_unknown_user)
    rc=PAM_IGNORE;
  if ((rc!=PAM_SUCCESS)&&(rc!=PAM_IGNORE))
    if (!cfg.no_warn)
      pam_error(pamh,"LDAP %s session failed",
                     (action==NSLCD_ACTION_PAM_SESS_O)?"open":"clode");
  return rc;
}

/* PAM session open call */
int pam_sm_open_session(
  pam_handle_t *pamh, int flags, int argc, const char **argv)
{
  return pam_sm_session(pamh,flags,argc,argv,NSLCD_ACTION_PAM_SESS_O);
}

/* PAM session close call */
int pam_sm_close_session(
  pam_handle_t *pamh, int flags, int argc, const char **argv)
{
  return pam_sm_session(pamh,flags,argc,argv,NSLCD_ACTION_PAM_SESS_C);
}

/* Change the password of the user. This function is first called with
   PAM_PRELIM_CHECK set in the flags and then without the flag. In the first
   pass it is determined whether we can contact the LDAP server and the
   provided old password is valid. In the second pass we get the new
   password and actually modify the password. */
int pam_sm_chauthtok(pam_handle_t *pamh,int flags,int argc,const char **argv)
{
  struct pld_cfg cfg;
  int rc;
  const char *username,*service;
  const char *oldpassword=NULL;
  const char *newpassword=NULL;
  struct pld_ctx *ctx=NULL;
  struct passwd *pwent;
  /* parse module options */
  parse_args(&cfg,flags,argc,argv);
  /* get user name */
  rc=pam_get_user(pamh,(const char **)&username,NULL);
  if (rc!=PAM_SUCCESS)
    return rc;
  if ((username==NULL)||(username[0]=='\0'))
    return PAM_USER_UNKNOWN;
  /* check uid */
  if (cfg.minimum_uid>0)
  {
    pwent=pam_modutil_getpwnam(args->pamh,username);
    if ((pwent!=NULL)&&(pwent->pw_uid<cfg.minimum_uid))
      return cfg.ignore_unknown_user?PAM_IGNORE:PAM_USER_UNKNOWN;
  }
  /* get our context */
  rc=ctx_get(pamh,username,&ctx);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get service name */
  rc=pam_get_item(pamh,PAM_SERVICE,(const void **)&service);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* prelimenary check, just see if we can connect to the LDAP server
     and authenticate with the current password */
  if (flags&PAM_PRELIM_CHECK)
  {
    /* see if the user is trying to modify another user's password */
    pwent=getpwnam(username);
    if ((pwent!=NULL)&&(pwent->pw_uid!=getuid()))
    {
      /* try to  authenticate with the LDAP administrator password by passing
         an empty username to the authc request */
      rc=pam_get_authtok(pamh,PAM_OLDAUTHTOK,&oldpassword,"LDAP administrator password: ");
      if (rc!=PAM_SUCCESS)
        return rc;
      username="";
    }
    else if ((ctx->oldpassword!=NULL)&&(*ctx->oldpassword!='\0'))
      /* we already have an old password stored (from a previous
         authentication phase) so we'll use that */
      oldpassword=ctx->oldpassword;
    else
    {
      rc=pam_get_authtok(pamh,PAM_OLDAUTHTOK,(const char **)&oldpassword,"(current) LDAP Password: ");
      if (rc!=PAM_SUCCESS)
        return rc;
    }
    /* try authenticating */
    rc=nslcd_request_authc(ctx,username,service,oldpassword);
    if (rc==PAM_SUCCESS)
      rc=ctx->authok;
    if ((rc==PAM_AUTHINFO_UNAVAIL)&&cfg.ignore_authinfo_unavail)
      rc=PAM_IGNORE;
    else if ((rc==PAM_USER_UNKNOWN)&&cfg.ignore_unknown_user)
      rc=PAM_IGNORE;
    /* TODO: figure out when to return PAM_TRY_AGAIN */
    /* TODO: if password is incorrect (NSLCD_PAM_AUTH_ERR) log that */
    return rc;
  }
  /* get the old password (from the previous call) */
  rc=pam_get_item(pamh,PAM_OLDAUTHTOK,(const void **)&oldpassword);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* get the new password */
  rc=pam_get_authtok(pamh,PAM_AUTHTOK,&newpassword,NULL);
  if (rc!=PAM_SUCCESS)
    return rc;
  /* perform the password modification */
  rc=nslcd_request_pwmod(ctx,username,service,oldpassword,newpassword);
  if (rc==PAM_SUCCESS)
    rc=ctx->authz;
  else
    ctx->authzmsg=(char *)pam_strerror(pamh,rc);
  if ((rc==PAM_AUTHINFO_UNAVAIL)&&cfg.ignore_authinfo_unavail)
    rc=PAM_IGNORE;
  else if ((rc==PAM_USER_UNKNOWN)&&cfg.ignore_unknown_user)
    rc=PAM_IGNORE;
  else if (!cfg.no_warn)
    pam_error(pamh,"%s",ctx->authzmsg);
  return rc;
}

#ifdef PAM_STATIC
struct pam_module _pam_ldap_modstruct={
  "pam_ldap",
  pam_sm_authenticate,
  pam_sm_setcred,
  pam_sm_acct_mgmt,
  pam_sm_open_session,
  pam_sm_close_session,
  pam_sm_chauthtok
};
#endif /* PAM_STATIC */