/*
    Authors:
        Sumit Bose <sbose@redhat.com>

    Copyright (C) 2009 Red Hat
    Copyright (C) 2010, rhafer@suse.de, Novell Inc.

    This program 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 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT
#define PAM_SM_SESSION
#define PAM_SM_PASSWORD

#include "config.h"
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <syslog.h>
#include <time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <locale.h>
#include <stdbool.h>

#include <security/pam_modules.h>
#include <security/pam_ext.h>
#include <security/pam_modutil.h>
#include "sss_pam_macros.h"

#include "sss_cli.h"

#include <libintl.h>
#define _(STRING) dgettext (PACKAGE, STRING)

#define FLAGS_USE_FIRST_PASS (1 << 0)
#define FLAGS_FORWARD_PASS   (1 << 1)
#define FLAGS_USE_AUTHTOK    (1 << 2)

#define PWEXP_FLAG "pam_sss:password_expired_flag"

#define PW_RESET_MSG_FILENAME_TEMPLATE SSSD_CONF_DIR"/customize/%s/pam_sss_pw_reset_message.%s"
#define PW_RESET_MSG_MAX_SIZE 4096

#define OPT_RETRY_KEY "retry="

struct pam_items {
    const char* pam_service;
    const char* pam_user;
    const char* pam_tty;
    const char* pam_ruser;
    const char* pam_rhost;
    char* pam_authtok;
    char* pam_newauthtok;
    const char* pamstack_authtok;
    const char* pamstack_oldauthtok;
    size_t pam_service_size;
    size_t pam_user_size;
    size_t pam_tty_size;
    size_t pam_ruser_size;
    size_t pam_rhost_size;
    int pam_authtok_type;
    size_t pam_authtok_size;
    int pam_newauthtok_type;
    size_t pam_newauthtok_size;
    pid_t cli_pid;
    const char *login_name;
    char *domain_name;
};

#define DEBUG_MGS_LEN 1024
#define MAX_AUTHTOK_SIZE (1024*1024)
#define CHECK_AND_RETURN_PI_STRING(s) ((s != NULL && *s != '\0')? s : "(not available)")

static void logger(pam_handle_t *pamh, int level, const char *fmt, ...) {
    va_list ap;

    va_start(ap, fmt);

#ifdef DEBUG
    va_list apd;
    char debug_msg[DEBUG_MGS_LEN];
    int ret;
    va_copy(apd, ap);

    ret = vsnprintf(debug_msg, DEBUG_MGS_LEN, fmt, apd);
    if (ret >= DEBUG_MGS_LEN) {
        D(("the following message is truncated: %s", debug_msg));
    } else if (ret < 0) {
        D(("vsnprintf failed to format debug message!"));
    } else {
        D((debug_msg));
    }

    va_end(apd);
#endif

    pam_vsyslog(pamh, LOG_AUTHPRIV|level, fmt, ap);

    va_end(ap);
}

static void free_exp_data(pam_handle_t *pamh, void *ptr, int err)
{
    free(ptr);
    ptr = NULL;
}

static size_t add_authtok_item(enum pam_item_type type,
                               enum sss_authtok_type authtok_type,
                               const char *tok, const size_t size,
                               uint8_t *buf) {
    size_t rp=0;
    uint32_t c;

    if (tok == NULL) return 0;

    c = type;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    c = size + sizeof(uint32_t);
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    c = authtok_type;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    memcpy(&buf[rp], tok, size);
    rp += size;

    return rp;
}


static size_t add_uint32_t_item(enum pam_item_type type, const uint32_t val,
                                uint8_t *buf) {
    size_t rp=0;
    uint32_t c;

    c = type;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    c = sizeof(uint32_t);
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    c = val;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    return rp;
}

static size_t add_string_item(enum pam_item_type type, const char *str,
                           const size_t size, uint8_t *buf) {
    size_t rp=0;
    uint32_t c;

    if (str == NULL || *str == '\0') return 0;

    c = type;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    c = size;
    memcpy(&buf[rp], &c, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    memcpy(&buf[rp], str, size);
    rp += size;

    return rp;
}

static void overwrite_and_free_pam_items(struct pam_items *pi)
{
    if (pi->pam_authtok != NULL) {
        _pam_overwrite_n((void *)pi->pam_authtok, pi->pam_authtok_size);
        free((void *)pi->pam_authtok);
        pi->pam_authtok = NULL;
    }

    if (pi->pam_newauthtok != NULL) {
        _pam_overwrite_n((void *)pi->pam_newauthtok,  pi->pam_newauthtok_size);
        free((void *)pi->pam_newauthtok);
        pi->pam_newauthtok = NULL;
    }

    pi->pamstack_authtok = NULL;
    pi->pamstack_oldauthtok = NULL;

    free(pi->domain_name);
    pi->domain_name = NULL;
}

static int pack_message_v3(struct pam_items *pi, size_t *size,
                           uint8_t **buffer) {
    int len;
    uint8_t *buf;
    int rp;
    uint32_t terminator = SSS_END_OF_PAM_REQUEST;

    len = sizeof(uint32_t) +
          2*sizeof(uint32_t) + pi->pam_user_size +
          sizeof(uint32_t);
    len += *pi->pam_service != '\0' ?
                2*sizeof(uint32_t) + pi->pam_service_size : 0;
    len += *pi->pam_tty != '\0' ?
                2*sizeof(uint32_t) + pi->pam_tty_size : 0;
    len += *pi->pam_ruser != '\0' ?
                2*sizeof(uint32_t) + pi->pam_ruser_size : 0;
    len += *pi->pam_rhost != '\0' ?
                2*sizeof(uint32_t) + pi->pam_rhost_size : 0;
    len += pi->pam_authtok != NULL ?
                3*sizeof(uint32_t) + pi->pam_authtok_size : 0;
    len += pi->pam_newauthtok != NULL ?
                3*sizeof(uint32_t) + pi->pam_newauthtok_size : 0;
    len += 3*sizeof(uint32_t); /* cli_pid */

    buf = malloc(len);
    if (buf == NULL) {
        D(("malloc failed."));
        return PAM_BUF_ERR;
    }

    rp = 0;
    ((uint32_t *)(&buf[rp]))[0] = SSS_START_OF_PAM_REQUEST;
    rp += sizeof(uint32_t);

    rp += add_string_item(SSS_PAM_ITEM_USER, pi->pam_user, pi->pam_user_size,
                          &buf[rp]);

    rp += add_string_item(SSS_PAM_ITEM_SERVICE, pi->pam_service,
                          pi->pam_service_size, &buf[rp]);

    rp += add_string_item(SSS_PAM_ITEM_TTY, pi->pam_tty, pi->pam_tty_size,
                          &buf[rp]);

    rp += add_string_item(SSS_PAM_ITEM_RUSER, pi->pam_ruser, pi->pam_ruser_size,
                          &buf[rp]);

    rp += add_string_item(SSS_PAM_ITEM_RHOST, pi->pam_rhost, pi->pam_rhost_size,
                          &buf[rp]);

    rp += add_uint32_t_item(SSS_PAM_ITEM_CLI_PID, (uint32_t) pi->cli_pid,
                            &buf[rp]);

    rp += add_authtok_item(SSS_PAM_ITEM_AUTHTOK, pi->pam_authtok_type,
                           pi->pam_authtok, pi->pam_authtok_size, &buf[rp]);

    rp += add_authtok_item(SSS_PAM_ITEM_NEWAUTHTOK, pi->pam_newauthtok_type,
                           pi->pam_newauthtok, pi->pam_newauthtok_size,
                           &buf[rp]);

    memcpy(&buf[rp], &terminator, sizeof(uint32_t));
    rp += sizeof(uint32_t);

    if (rp != len) {
        D(("error during packet creation."));
        free(buf);
        return PAM_BUF_ERR;
    }

    *size = len;
    *buffer = buf;

    return 0;
}

static int null_strcmp(const char *s1, const char *s2) {
    if (s1 == NULL && s2 == NULL) return 0;
    if (s1 == NULL && s2 != NULL) return -1;
    if (s1 != NULL && s2 == NULL) return 1;
    return strcmp(s1, s2);
}

enum {
    SSS_PAM_CONV_DONE = 0,
    SSS_PAM_CONV_STD,
    SSS_PAM_CONV_REENTER,
};

static int do_pam_conversation(pam_handle_t *pamh, const int msg_style,
                               const char *msg,
                               const char *reenter_msg,
                               char **_answer)
{
    int ret;
    int state = SSS_PAM_CONV_STD;
    struct pam_conv *conv;
    const struct pam_message *mesg[1];
    struct pam_message *pam_msg;
    struct pam_response *resp=NULL;
    char *answer = NULL;

    if ((msg_style == PAM_TEXT_INFO || msg_style == PAM_ERROR_MSG) &&
        msg == NULL) return PAM_SYSTEM_ERR;

    if ((msg_style == PAM_PROMPT_ECHO_OFF ||
         msg_style == PAM_PROMPT_ECHO_ON) &&
        (msg == NULL || _answer == NULL)) return PAM_SYSTEM_ERR;

    if (msg_style == PAM_TEXT_INFO || msg_style == PAM_ERROR_MSG) {
        logger(pamh, LOG_INFO, "User %s message: %s",
                               msg_style == PAM_TEXT_INFO ? "info" : "error",
                               msg);
    }

    ret=pam_get_item(pamh, PAM_CONV, (const void **) &conv);
    if (ret != PAM_SUCCESS) return ret;

    do {
        pam_msg = malloc(sizeof(struct pam_message));
        if (pam_msg == NULL) {
            D(("Malloc failed."));
            ret = PAM_SYSTEM_ERR;
            goto failed;
        }

        pam_msg->msg_style = msg_style;
        if (state == SSS_PAM_CONV_REENTER) {
            pam_msg->msg = reenter_msg;
        } else {
            pam_msg->msg = msg;
        }

        mesg[0] = (const struct pam_message *) pam_msg;

        ret=conv->conv(1, mesg, &resp,
                       conv->appdata_ptr);
        free(pam_msg);
        if (ret != PAM_SUCCESS) {
            D(("Conversation failure: %s.",  pam_strerror(pamh,ret)));
            goto failed;
        }

        if (msg_style == PAM_PROMPT_ECHO_OFF ||
            msg_style == PAM_PROMPT_ECHO_ON) {
            if (resp == NULL) {
                D(("response expected, but resp==NULL"));
                ret = PAM_SYSTEM_ERR;
                goto failed;
            }

            if (state == SSS_PAM_CONV_REENTER) {
                if (null_strcmp(answer, resp[0].resp) != 0) {
                    logger(pamh, LOG_NOTICE, "Passwords do not match.");
                    _pam_overwrite((void *)resp[0].resp);
                    free(resp[0].resp);
                    if (answer != NULL) {
                        _pam_overwrite((void *) answer);
                        free(answer);
                        answer = NULL;
                    }
                    ret = do_pam_conversation(pamh, PAM_ERROR_MSG,
                                              _("Passwords do not match"),
                                              NULL, NULL);
                    if (ret != PAM_SUCCESS) {
                        D(("do_pam_conversation failed."));
                        ret = PAM_SYSTEM_ERR;
                        goto failed;
                    }
                    ret = PAM_CRED_ERR;
                    goto failed;
                }
                _pam_overwrite((void *)resp[0].resp);
                free(resp[0].resp);
            } else {
                if (resp[0].resp == NULL) {
                    D(("Empty password"));
                    answer = NULL;
                } else {
                    answer = strndup(resp[0].resp, MAX_AUTHTOK_SIZE);
                    _pam_overwrite((void *)resp[0].resp);
                    free(resp[0].resp);
                    if(answer == NULL) {
                        D(("strndup failed"));
                        ret = PAM_BUF_ERR;
                        goto failed;
                    }
                }
            }
            free(resp);
            resp = NULL;
        }

        if (reenter_msg != NULL && state == SSS_PAM_CONV_STD) {
            state = SSS_PAM_CONV_REENTER;
        } else {
            state = SSS_PAM_CONV_DONE;
        }
    } while (state != SSS_PAM_CONV_DONE);

    if (_answer) *_answer = answer;
    return PAM_SUCCESS;

failed:
    free(answer);
    return ret;

}

static errno_t display_pw_reset_message(pam_handle_t *pamh,
                                        const char *domain_name,
                                        const char *suffix)
{
    int ret;
    struct stat stat_buf;
    char *msg_buf = NULL;
    int fd = -1;
    size_t size;
    size_t total_len;
    char *filename = NULL;