/** BEGIN COPYRIGHT BLOCK
 * This Program 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; version 2 of the License.
 *
 * This Program 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, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * In addition, as a special exception, Red Hat, Inc. gives You the additional
 * right to link the code of this Program with code not covered under the GNU
 * General Public License ("Non-GPL Code") and to distribute linked combinations
 * including the two, subject to the limitations in this paragraph. Non-GPL Code
 * permitted under this exception must only link to the code of this Program
 * through those well defined interfaces identified in the file named EXCEPTION
 * found in the source code files (the "Approved Interfaces"). The files of
 * Non-GPL Code may instantiate templates or use macros or inline functions from
 * the Approved Interfaces without causing the resulting work to be covered by
 * the GNU General Public License. Only Red Hat, Inc. may make changes or
 * additions to the list of Approved Interfaces. You must obey the GNU General
 * Public License in all respects for all of the Program code and other code used
 * in conjunction with the Program except the Non-GPL Code covered by this
 * exception. If you modify this file, you may extend this exception to your
 * version of the file, but you are not obligated to do so. If you do not wish to
 * provide this exception without modification, you must delete this exception
 * statement from your version and license this file solely under the GPL without
 * exception.
 *
 *
 * Copyright (C) 2005 Red Hat, Inc.
 * All rights reserved.
 * END COPYRIGHT BLOCK **/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#ifdef HAVE_DIRSRV_SLAPI_PLUGIN_H
#include <nspr.h>
#include <nss.h>
#include <dirsrv/slapi-plugin.h>
#else
#include <slapi-plugin.h>
#endif


#include <security/pam_appl.h>
#include "format.h"

/* Utility struct to wrap strings to avoid mallocs if possible - use
   stack allocated string space */
#define MY_STATIC_BUF_SIZE 256
typedef struct my_str_buf {
	char fixbuf[MY_STATIC_BUF_SIZE];
	char *str;
} MyStrBuf;

static char *
init_my_str_buf(MyStrBuf *buf, const char *s)
{
	PR_ASSERT(buf);
	if (s && (strlen(s) < sizeof(buf->fixbuf))) {
		strcpy(buf->fixbuf, s);
		buf->str = buf->fixbuf;
	} else {
		buf->str = slapi_ch_strdup(s);
		buf->fixbuf[0] = 0;
	}

	return buf->str;
}

static void
delete_my_str_buf(MyStrBuf *buf)
{
	if (buf->str != buf->fixbuf) {
		slapi_ch_free_string(&(buf->str));
	}
}

/* for third arg to pam_start */
struct my_pam_conv_str {
	Slapi_PBlock *pb;
	char *pam_identity;
};

static void
free_pam_response(int nresp, struct pam_response *resp)
{
	int ii;
	for (ii = 0; ii < nresp; ++ii) {
		if (resp[ii].resp) {
			slapi_ch_free((void **)&(resp[ii].resp));
		}
	}
	slapi_ch_free((void **)&resp);
}

/*
 * This is the conversation function passed into pam_start().  This is what sets the password
 * that PAM uses to authenticate.  This function is sort of stupid - it assumes all echo off
 * or binary prompts are for the password, and other prompts are for the username.  Time will
 * tell if this is actually the case.
 */
static int
pam_conv_func(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *mydata)
{
	int ii;
	struct berval *creds;
	struct my_pam_conv_str *my_data = (struct my_pam_conv_str *)mydata;
	struct pam_response *reply;
	int ret = PAM_SUCCESS;

	if (num_msg <= 0) {
		return PAM_CONV_ERR;
	}

	/* empty reply structure */
	reply = (struct pam_response *)slapi_ch_calloc(num_msg, sizeof(struct pam_response));
	slapi_pblock_get( my_data->pb, SLAPI_BIND_CREDENTIALS, &creds ); /* the password */
	for (ii = 0; ii < num_msg; ++ii) {
		/* hard to tell what prompt is for . . . */
		/* assume prompts for password are either BINARY or ECHO_OFF */
		if (msg[ii]->msg_style == PAM_PROMPT_ECHO_OFF) {
			reply[ii].resp = format_strdupbv(creds);
#ifdef LINUX
		} else if (msg[ii]->msg_style == PAM_BINARY_PROMPT) {
			reply[ii].resp = format_strdupbv(creds);
#endif
		} else if (msg[ii]->msg_style == PAM_PROMPT_ECHO_ON) { /* assume username */
			reply[ii].resp = slapi_ch_strdup(my_data->pam_identity);
		} else if (msg[ii]->msg_style == PAM_ERROR_MSG) {
		} else if (msg[ii]->msg_style == PAM_TEXT_INFO) {
		} else {
			ret = PAM_CONV_ERR;
		}
	}

	if (ret == PAM_CONV_ERR) {
		free_pam_response(num_msg, reply);
		reply = NULL;
	}

	*resp = reply;

	return ret;
}

/*
 * Do the actual work of authenticating with PAM. First, get the PAM identity
 * based on the method used to convert the BIND identity to the PAM identity.
 * Set up the structures that pam_start needs and call pam_start().  After
 * that, call pam_authenticate and pam_acct_mgmt.  Check the various return
 * values from these functions and map them to their corresponding LDAP BIND
 * return values.  Return the appropriate LDAP error code.
 * This function will also set the appropriate LDAP response controls in
 * the given pblock.
 * Since this function can be called multiple times, we only want to return
 * the errors and controls to the user if this is the final call, so the
 * final_method parameter tells us if this is the last one.  Coupled with
 * the fallback argument, we can tell if we are able to send the response
 * back to the client.
 */
static int
do_pam_auth(
	Slapi_PBlock *pb,
	char *pam_service, /* name of service for pam_start() */
	int pw_response_requested, /* do we need to send pwd policy resp control */
	const char *username
)
{
	MyStrBuf pam_id;
	const char *binddn = NULL;
	Slapi_DN *bindsdn = NULL;
	int rc = PAM_SUCCESS;
	int retcode = LDAP_SUCCESS;
	pam_handle_t *pam_handle;
	struct my_pam_conv_str my_data;
	struct pam_conv my_pam_conv = {pam_conv_func, NULL};
	char *errmsg = NULL; /* free with PR_smprintf_free */

	slapi_pblock_get( pb, SLAPI_BIND_TARGET_SDN, &bindsdn );
	if (NULL == bindsdn) {
		errmsg = PR_smprintf("Null bind dn");
		retcode = LDAP_OPERATIONS_ERROR;
		pam_id.str = NULL; /* initialize pam_id.str */
		goto done; /* skip the pam stuff */
	}
	binddn = slapi_sdn_get_dn(bindsdn);

	init_my_str_buf(&pam_id, username);
	if (!pam_id.str) {
		errmsg = PR_smprintf("Bind DN [%s] is invalid or not found", binddn);
		retcode = LDAP_NO_SUCH_OBJECT; /* user unknown */
		goto done; /* skip the pam stuff */
	}

	/* do the pam stuff */
	my_data.pb = pb;
	my_data.pam_identity = pam_id.str;
	my_pam_conv.appdata_ptr = &my_data;
	/* from this point on we are in the critical section */
	rc = pam_start(pam_service, pam_id.str, &my_pam_conv, &pam_handle);

	if (rc == PAM_SUCCESS) {
		/* use PAM_SILENT - there is no user interaction at this point */
		rc = pam_authenticate(pam_handle, 0);
		/* check different types of errors here */
		if (rc == PAM_USER_UNKNOWN) {
			errmsg = PR_smprintf("User id [%s] for bind DN [%s] does not exist in PAM",
								 pam_id.str, binddn);
			retcode = LDAP_NO_SUCH_OBJECT; /* user unknown */
		} else if (rc == PAM_AUTH_ERR) {
			errmsg = PR_smprintf("Invalid PAM password for user id [%s], bind DN [%s]",
								 pam_id.str, binddn);
			retcode = LDAP_INVALID_CREDENTIALS; /* invalid creds */
		} else if (rc == PAM_MAXTRIES) {
			errmsg = PR_smprintf("Authentication retry limit exceeded in PAM for "
								 "user id [%s], bind DN [%s]",
								 pam_id.str, binddn);
			if (pw_response_requested) {
				slapi_pwpolicy_make_response_control(pb, -1, -1, LDAP_PWPOLICY_ACCTLOCKED);
			}
			retcode = LDAP_CONSTRAINT_VIOLATION; /* max retries */
		} else if (rc != PAM_SUCCESS) {
			errmsg = PR_smprintf("Unknown PAM error [%s] for user id [%s], bind DN [%s]",
								 pam_strerror(pam_handle, rc), pam_id.str, binddn);
			retcode = LDAP_OPERATIONS_ERROR; /* pam config or network problem */
		}
	}

	/* if user authenticated successfully, see if there is anything we need
	   to report back w.r.t. password or account lockout */
	if (rc == PAM_SUCCESS) {
		rc = pam_acct_mgmt(pam_handle, 0);
		/* check different types of errors here */
		if (rc == PAM_USER_UNKNOWN) {
			errmsg = PR_smprintf("User id [%s] for bind DN [%s] does not exist in PAM",
								 pam_id.str, binddn);
			retcode = LDAP_NO_SUCH_OBJECT; /* user unknown */
		} else if (rc == PAM_AUTH_ERR) {
			errmsg = PR_smprintf("Invalid PAM password for user id [%s], bind DN [%s]",
								 pam_id.str, binddn);
			retcode = LDAP_INVALID_CREDENTIALS; /* invalid creds */
		} else if (rc == PAM_PERM_DENIED) {
			errmsg = PR_smprintf("Access denied for PAM user id [%s], bind DN [%s]"
								 " - see administrator",
								 pam_id.str, binddn);
			if (pw_response_requested) {
				slapi_pwpolicy_make_response_control(pb, -1, -1, LDAP_PWPOLICY_ACCTLOCKED);
			}
			retcode = LDAP_UNWILLING_TO_PERFORM;
		} else if (rc == PAM_ACCT_EXPIRED) {
			errmsg = PR_smprintf("Expired PAM password for user id [%s], bind DN [%s]: "
								 "reset required",
								 pam_id.str, binddn);
			slapi_add_pwd_control(pb, LDAP_CONTROL_PWEXPIRED, 0);
			if (pw_response_requested) {
				slapi_pwpolicy_make_response_control(pb, -1, -1, LDAP_PWPOLICY_PWDEXPIRED);
			}
			retcode = LDAP_INVALID_CREDENTIALS;
		} else if (rc == PAM_NEW_AUTHTOK_REQD) { /* handled same way as ACCT_EXPIRED */
			errmsg = PR_smprintf("Expired PAM password for user id [%s], bind DN [%s]: "
								 "reset required",
								 pam_id.str, binddn);
			slapi_add_pwd_control(pb, LDAP_CONTROL_PWEXPIRED, 0);
			if (pw_response_requested) {
				slapi_pwpolicy_make_response_control(pb, -1, -1, LDAP_PWPOLICY_PWDEXPIRED);
			}
			retcode = LDAP_INVALID_CREDENTIALS;
		} else if (rc != PAM_SUCCESS) {
			errmsg = PR_smprintf("Unknown PAM error [%s] for user id [%s], bind DN [%s]",
								 pam_strerror(pam_handle, rc), pam_id.str, binddn);
			retcode = LDAP_OPERATIONS_ERROR; /* unknown */
		}
	}

	rc = pam_end(pam_handle, rc);
	/* not in critical section any more */

done:
	delete_my_str_buf(&pam_id);

	if ((retcode == LDAP_SUCCESS) && (rc != PAM_SUCCESS)) {
		errmsg = PR_smprintf("Unknown PAM error [%d] for user id [%s], bind DN [%s]",
							 rc, pam_id.str, binddn);
		retcode = LDAP_OPERATIONS_ERROR;
	}

	if (retcode != LDAP_SUCCESS) {
		slapi_send_ldap_result(pb, retcode, NULL, errmsg, 0, NULL);
	}

	if (errmsg) {
		PR_smprintf_free(errmsg);
	}

	return retcode;
}

/*
 * Entry point into the PAM auth code.  Shields the rest of the app
 * from PAM API code.  Get our config params, then call the actual
 * code that does the PAM auth.  Can call that code up to 3 times,
 * depending on what methods are set in the config.
 */
int
backend_sch_do_pam_auth(Slapi_PBlock *pb, const char *username)
{
	int rc = LDAP_SUCCESS;
	MyStrBuf pam_service; /* avoid malloc if possible */
	int pw_response_requested;
	LDAPControl **reqctrls = NULL;

	init_my_str_buf(&pam_service, "system-auth");

	slapi_pblock_get (pb, SLAPI_REQCONTROLS, &reqctrls);
	slapi_pblock_get (pb, SLAPI_PWPOLICY, &pw_response_requested);

	/* figure out which method is the last one - we only return error codes, controls
	   to the client and send a response on the last method */

	rc = do_pam_auth(pb, pam_service.str, pw_response_requested, username);

	delete_my_str_buf(&pam_service);

	return rc;
}