/*
    SSSD

    Kerberos 5 Backend Module

    Authors:
        Sumit Bose <sbose@redhat.com>

    Copyright (C) 2009-2010 Red Hat

    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; 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 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 <errno.h>
#include <sys/time.h>

#include <sys/types.h>
#include <sys/wait.h>
#include <pwd.h>
#include <sys/stat.h>

#include <security/pam_modules.h>

#include "util/util.h"
#include "util/find_uid.h"
#include "db/sysdb.h"
#include "providers/child_common.h"
#include "providers/krb5/krb5_auth.h"
#include "providers/krb5/krb5_utils.h"

#define TIME_T_MAX LONG_MAX
#define int64_to_time_t(val) ((time_t)((val) < TIME_T_MAX ? val : TIME_T_MAX))

static errno_t safe_remove_old_ccache_file(const char *old_ccache_file,
                                           const char *new_ccache_file)
{
    int ret;
    size_t old_offset = 0;
    size_t new_offset = 0;

    if (new_ccache_file == NULL) {
        DEBUG(1, ("Missing new ccache file, "
                  "old ccache file is not deleted.\n"));
        return EINVAL;
    }

    if (old_ccache_file != NULL) {
        if (strncmp(old_ccache_file, "FILE:", 5) == 0) {
            old_offset = 5;
        }
        if (strncmp(new_ccache_file, "FILE:", 5) == 0) {
            new_offset = 5;
        }
        if (strcmp(old_ccache_file + old_offset,
                   new_ccache_file + new_offset) == 0) {
            DEBUG(7, ("New and old ccache file are the same, "
                      "no one will be deleted.\n"));
            return EOK;
        }
        if (old_ccache_file[old_offset] != '/') {
            DEBUG(1, ("Ccache file name [%s] is not an absolute path.\n",
                      old_ccache_file + old_offset));
            return EINVAL;
        }
        ret = unlink(old_ccache_file + old_offset);
        if (ret == -1 && errno != ENOENT) {
            ret = errno;
            DEBUG(1, ("unlink [%s] failed [%d][%s].\n", old_ccache_file, ret,
                                                        strerror(ret)));
            return ret;
        }
    }

    return EOK;
}

static errno_t check_if_ccache_file_is_used(uid_t uid, const char *ccname,
                                            bool *result)
{
    int ret;
    size_t offset = 0;
    struct stat stat_buf;
    const char *filename;
    bool active;

    *result = false;

    if (ccname == NULL || *ccname == '\0') {
        return EINVAL;
    }

    if (strncmp(ccname, "FILE:", 5) == 0) {
        offset = 5;
    }

    filename = ccname + offset;

    if (filename[0] != '/') {
        DEBUG(1, ("Only absolute path names are allowed.\n"));
        return EINVAL;
    }

    ret = lstat(filename, &stat_buf);

    if (ret == -1 && errno != ENOENT) {
        DEBUG(1, ("stat failed [%d][%s].\n", errno, strerror(errno)));
        return errno;
    } else if (ret == EOK) {
        if (stat_buf.st_uid != uid) {
            DEBUG(1, ("Cache file [%s] exists, but is owned by [%d] instead of "
                      "[%d].\n", filename, stat_buf.st_uid, uid));
            return EINVAL;
        }

        if (!S_ISREG(stat_buf.st_mode)) {
            DEBUG(1, ("Cache file [%s] exists, but is not a regular file.\n",
                      filename));
            return EINVAL;
        }
    }

    ret = check_if_uid_is_active(uid, &active);
    if (ret != EOK) {
        DEBUG(1, ("check_if_uid_is_active failed.\n"));
        return ret;
    }

    if (!active) {
        DEBUG(5, ("User [%d] is not active\n", uid));
    } else {
        DEBUG(9, ("User [%d] is still active, reusing ccache file [%s].\n",
                  uid, filename));
        *result = true;
    }
    return EOK;
}

static int krb5_save_ccname(TALLOC_CTX *mem_ctx,
                            struct sysdb_ctx *sysdb,
                            struct sss_domain_info *domain,
                            const char *name,
                            const char *ccname)
{
    TALLOC_CTX *tmpctx;
    struct sysdb_attrs *attrs;
    int ret;

    if (name == NULL || ccname == NULL) {
        DEBUG(1, ("Missing user or ccache name.\n"));
        return EINVAL;
    }

    DEBUG(9, ("Save ccname [%s] for user [%s].\n", ccname, name));

    tmpctx = talloc_new(mem_ctx);
    if (!tmpctx) {
        return ENOMEM;
    }

    attrs = sysdb_new_attrs(mem_ctx);
    if (!attrs) {
        ret = ENOMEM;
        goto done;
    }

    ret = sysdb_attrs_add_string(attrs, SYSDB_CCACHE_FILE, ccname);
    if (ret != EOK) {
        DEBUG(1, ("sysdb_attrs_add_string failed.\n"));
        goto done;
    }

    ret = sysdb_transaction_start(sysdb);
    if (ret != EOK) {
        DEBUG(6, ("Error %d starting transaction (%s)\n", ret, strerror(ret)));
        goto done;
    }

    ret = sysdb_set_user_attr(tmpctx, sysdb,
                              domain, name, attrs, SYSDB_MOD_REP);
    if (ret != EOK) {
        DEBUG(6, ("Error: %d (%s)\n", ret, strerror(ret)));
        sysdb_transaction_cancel(sysdb);
        goto done;
    }

    ret = sysdb_transaction_commit(sysdb);
    if (ret != EOK) {
        DEBUG(1, ("Failed to commit transaction!\n"));
    }

done:
    talloc_zfree(tmpctx);
    return ret;
}

static struct krb5_ctx *get_krb5_ctx(struct be_req *be_req)
{
    struct pam_data *pd;

    pd = talloc_get_type(be_req->req_data, struct pam_data);

    switch (pd->cmd) {
        case SSS_PAM_AUTHENTICATE:
        case SSS_CMD_RENEW:
            return talloc_get_type(be_req->be_ctx->bet_info[BET_AUTH].pvt_bet_data,
                                   struct krb5_ctx);
            break;
        case SSS_PAM_ACCT_MGMT:
            return talloc_get_type(be_req->be_ctx->bet_info[BET_ACCESS].pvt_bet_data,
                                   struct krb5_ctx);
            break;
        case SSS_PAM_CHAUTHTOK:
        case SSS_PAM_CHAUTHTOK_PRELIM:
            return talloc_get_type(be_req->be_ctx->bet_info[BET_CHPASS].pvt_bet_data,
                                   struct krb5_ctx);
            break;
        default:
            DEBUG(1, ("Unsupported PAM task.\n"));
            return NULL;
    }
}

static void krb_reply(struct be_req *req, int dp_err, int result);

static int krb5_cleanup(void *ptr)
{
    struct krb5child_req *kr = talloc_get_type(ptr, struct krb5child_req);

    if (kr == NULL) return EOK;

    memset(kr, 0, sizeof(struct krb5child_req));

    return EOK;
}

errno_t krb5_setup(TALLOC_CTX *mem_ctx, struct pam_data *pd,
                   struct krb5_ctx *krb5_ctx, struct krb5child_req **krb5_req)
{
    struct krb5child_req *kr = NULL;

    kr = talloc_zero(mem_ctx, struct krb5child_req);
    if (kr == NULL) {
        DEBUG(1, ("talloc failed.\n"));
        return ENOMEM;
    }
    kr->is_offline = false;
    kr->active_ccache_present = true;
    kr->run_as_user = true;
    talloc_set_destructor((TALLOC_CTX *) kr, krb5_cleanup);

    kr->pd = pd;
    kr->krb5_ctx = krb5_ctx;

    *krb5_req = kr;

    return EOK;
}

static void krb5_resolve_kdc_done(struct tevent_req *subreq);
static void krb5_resolve_kpasswd_done(struct tevent_req *subreq);
static void krb5_find_ccache_step(struct tevent_req *req);
static void krb5_save_ccname_done(struct tevent_req *req);
static void krb5_child_done(struct tevent_req *req);
static void krb5_pam_handler_cache_auth_step(struct tevent_req *req);

struct krb5_auth_state {
    struct tevent_context *ev;
    struct be_ctx *be_ctx;
    struct pam_data *pd;
    struct krb5_ctx *krb5_ctx;
    struct krb5child_req *kr;

    int pam_status;
    int dp_err;
};

int krb5_auth_recv(struct tevent_req *req, int *pam_status, int *dp_err)
{
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);

    *pam_status = state->pam_status;
    *dp_err = state->dp_err;

    TEVENT_REQ_RETURN_ON_ERROR(req);

    return EOK;
}

struct tevent_req *krb5_auth_send(TALLOC_CTX *mem_ctx,
                                  struct tevent_context *ev,
                                  struct be_ctx *be_ctx,
                                  struct pam_data *pd,
                                  struct krb5_ctx *krb5_ctx)
{
    const char **attrs;
    struct krb5_auth_state *state;
    struct ldb_result *res;
    struct krb5child_req *kr = NULL;
    const char *ccache_file = NULL;
    const char *realm;
    krb5_error_code kerr;
    struct tevent_req *req;
    struct tevent_req *subreq;
    int ret;

    req = tevent_req_create(mem_ctx, &state, struct krb5_auth_state);
    if (req == NULL) {
        DEBUG(1, ("tevent_req_create failed.\n"));
        return NULL;
    }

    state->ev = ev;
    state->be_ctx = be_ctx;
    state->pd = pd;
    state->krb5_ctx = krb5_ctx;
    state->kr = NULL;
    state->pam_status = PAM_SYSTEM_ERR;
    state->dp_err = DP_ERR_FATAL;

    switch (pd->cmd) {
        case SSS_PAM_AUTHENTICATE:
        case SSS_CMD_RENEW:
        case SSS_PAM_CHAUTHTOK:
            break;
        case SSS_PAM_CHAUTHTOK_PRELIM:
            if (pd->priv == 1 && pd->authtok_size == 0) {
                DEBUG(4, ("Password reset by root is not supported.\n"));
                state->pam_status = PAM_PERM_DENIED;
                state->dp_err = DP_ERR_OK;
                ret = EOK;
                goto done;
            }
            break;
        default:
            DEBUG(4, ("Unexpected pam task %d.\n", pd->cmd));
            state->pam_status = PAM_SYSTEM_ERR;
            state->dp_err = DP_ERR_FATAL;
            ret = EINVAL;
            goto done;
    }

    if (be_is_offline(be_ctx) &&
        (pd->cmd == SSS_PAM_CHAUTHTOK || pd->cmd == SSS_PAM_CHAUTHTOK_PRELIM ||
         pd->cmd == SSS_CMD_RENEW)) {
        DEBUG(9, ("Password changes and ticket renewal are not possible "
                  "while offline.\n"));
        state->pam_status = PAM_AUTHINFO_UNAVAIL;
        state->dp_err = DP_ERR_OFFLINE;
        ret = EOK;
        goto done;
    }

    attrs = talloc_array(state, const char *, 6);
    if (attrs == NULL) {
        ret = ENOMEM;
        goto done;
    }

    attrs[0] = SYSDB_UPN;
    attrs[1] = SYSDB_HOMEDIR;
    attrs[2] = SYSDB_CCACHE_FILE;
    attrs[3] = SYSDB_UIDNUM;
    attrs[4] = SYSDB_GIDNUM;
    attrs[5] = NULL;

    ret = krb5_setup(state, pd, krb5_ctx, &state->kr);
    if (ret != EOK) {
        DEBUG(1, ("krb5_setup failed.\n"));
        goto done;
    }
    kr = state->kr;

    ret = sysdb_get_user_attr(state, be_ctx->sysdb, be_ctx->domain,
                              state->pd->user, attrs, &res);
    if (ret) {
        DEBUG(5, ("sysdb search for upn of user [%s] failed.\n", pd->user));
        state->pam_status = PAM_SYSTEM_ERR;
        state->dp_err = DP_ERR_OK;
        goto done;
    }

    realm = dp_opt_get_cstring(krb5_ctx->opts, KRB5_REALM);
    if (realm == NULL) {
        DEBUG(1, ("Missing Kerberos realm.\n"));
        ret = ENOENT;
        goto done;
    }

    switch (res->count) {
    case 0:
        DEBUG(5, ("No attributes for user [%s] found.\n", pd->user));
        ret = ENOENT;
        goto done;
        break;

    case 1:
        kr->upn = ldb_msg_find_attr_as_string(res->msgs[0], SYSDB_UPN, NULL);
        if (kr->upn == NULL) {
            ret = krb5_get_simple_upn(state, krb5_ctx, pd->user, &kr->upn);
            if (ret != EOK) {
                DEBUG(1, ("krb5_get_simple_upn failed.\n"));
                goto done;
            }
        }

        kr->homedir = ldb_msg_find_attr_as_string(res->msgs[0], SYSDB_HOMEDIR,
                                                  NULL);
        if (kr->homedir == NULL) {
            DEBUG(4, ("Home directory for user [%s] not known.\n", pd->user));
        }

        kr->uid = ldb_msg_find_attr_as_uint64(res->msgs[0], SYSDB_UIDNUM, 0);
        if (kr->uid == 0) {
            DEBUG(4, ("UID for user [%s] not known.\n", pd->user));
            ret = ENOENT;
            goto done;
        }

        kr->gid = ldb_msg_find_attr_as_uint64(res->msgs[0], SYSDB_GIDNUM, 0);
        if (kr->gid == 0) {
            DEBUG(4, ("GID for user [%s] not known.\n", pd->user));
            ret = ENOENT;
            goto done;
        }

        ccache_file = ldb_msg_find_attr_as_string(res->msgs[0],
                                                  SYSDB_CCACHE_FILE,
                                                  NULL);
        if (ccache_file != NULL) {
            ret = check_if_ccache_file_is_used(kr->uid, ccache_file,
                                               &kr->active_ccache_present);
            if (ret != EOK) {
                DEBUG(1, ("check_if_ccache_file_is_used failed.\n"));
                goto done;
            }

            kerr = check_for_valid_tgt(ccache_file, realm, kr->upn,
                                       &kr->valid_tgt_present);
            if (kerr != 0) {
                DEBUG(1, ("check_for_valid_tgt failed.\n"));
                ret = kerr;
                goto done;
            }
        } else {
            kr->active_ccache_present = false;
            kr->valid_tgt_present = false;
            DEBUG(4, ("No ccache file for user [%s] found.\n", pd->user));
        }
        DEBUG(9, ("Ccache_file is [%s] and is %s active and TGT is %s valid.\n",
                  ccache_file ? ccache_file : "not set",
                  kr->active_ccache_present ? "" : "not",
                  kr->valid_tgt_present ? "" : "not"));
        if (ccache_file != NULL) {
            kr->ccname = ccache_file;
            kr->old_ccname = talloc_strdup(kr, ccache_file);
            if (kr->old_ccname == NULL) {
                DEBUG(1, ("talloc_strdup failed.\n"));
                ret = ENOMEM;
                goto done;
            }
        } else {
            kr->ccname = NULL;
            kr->old_ccname = NULL;
        }
        break;

    default:
        DEBUG(1, ("User search for (%s) returned > 1 results!\n", pd->user));
        ret = EINVAL;
        goto done;
        break;
    }

    kr->srv = NULL;
    kr->kpasswd_srv = NULL;
    subreq = be_resolve_server_send(state, state->ev, state->be_ctx,
                                    krb5_ctx->service->name);
    if (subreq == NULL) {
        DEBUG(1, ("be_resolve_server_send failed.\n"));
        ret = ENOMEM;
        goto done;
    }

    tevent_req_set_callback(subreq, krb5_resolve_kdc_done, req);

    return req;

done:
    if (ret == EOK) {
        tevent_req_done(req);
    } else {
        tevent_req_error(req, ret);
    }
    tevent_req_post(req, state->ev);
    return req;
}

static void krb5_resolve_kdc_done(struct tevent_req *subreq)
{
    struct tevent_req *req = tevent_req_callback_data(subreq, struct tevent_req);
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    struct krb5child_req *kr = state->kr;
    int ret;

    ret = be_resolve_server_recv(subreq, &kr->srv);
    talloc_zfree(subreq);
    if (ret) {
        /* all servers have been tried and none
         * was found good, setting offline,
         * but we still have to call the child to setup
         * the ccache file. */
        be_mark_offline(state->be_ctx);
        kr->is_offline = true;
    } else {
        if (kr->krb5_ctx->kpasswd_service != NULL) {
            subreq = be_resolve_server_send(state, state->ev, state->be_ctx,
                                            kr->krb5_ctx->kpasswd_service->name);
            if (subreq == NULL) {
                DEBUG(1, ("be_resolve_server_send failed.\n"));
                ret = ENOMEM;
                goto failed;
            }

            tevent_req_set_callback(subreq, krb5_resolve_kpasswd_done, req);

            return;
        }
    }

    krb5_find_ccache_step(req);
    return;

failed:
    tevent_req_error(req, ret);
}

static void krb5_resolve_kpasswd_done(struct tevent_req *subreq)
{
    struct tevent_req *req = tevent_req_callback_data(subreq, struct tevent_req);
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    int ret;

    ret = be_resolve_server_recv(subreq, &state->kr->kpasswd_srv);
    talloc_zfree(subreq);
    if (ret) {
        /* all kpasswd servers have been tried and none was found good, but the
         * kdc seems ok. Password changes are not possible but
         * authentication. We return an PAM error here, but do not mark the
         * backend offline. */
        state->pam_status = PAM_AUTHTOK_LOCK_BUSY;
        state->dp_err = DP_ERR_OK;
        tevent_req_done(req);
        return;
    }

    krb5_find_ccache_step(req);
}

static void krb5_find_ccache_step(struct tevent_req *req)
{
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    int ret;
    struct krb5child_req *kr = state->kr;
    struct pam_data *pd = kr->pd;
    char *msg;
    bool private_path = false;
    struct tevent_req *subreq = NULL;

    if (!kr->is_offline) {
        kr->is_offline = be_is_offline(state->be_ctx);
    }

    /* The ccache file should be (re)created if one of the following conditions
     * is true:
     * - it doesn't exist (kr->ccname == NULL)
     * - the backend is online and the current ccache file is not used, i.e
     *   the related user is currently not logged in and it is not a renewal
     *   request
     *   (!kr->is_offline && !kr->active_ccache_present &&
     *    pd->cmd != SSS_CMD_RENEW)
     * - the backend is offline and the current cache file not used and
     *   it does not contain a valid tgt
     *   (kr->is_offline &&
     *    !kr->active_ccache_present && !kr->valid_tgt_present)
     */
    if (kr->ccname == NULL ||
        (kr->is_offline && !kr->active_ccache_present &&
            !kr->valid_tgt_present) ||
        (!kr->is_offline && !kr->active_ccache_present &&
         pd->cmd != SSS_CMD_RENEW)) {
            DEBUG(9, ("Recreating  ccache file.\n"));
            kr->ccname = expand_ccname_template(kr, kr,
                                          dp_opt_get_cstring(kr->krb5_ctx->opts,
                                                             KRB5_CCNAME_TMPL),
                                                true, &private_path);
            if (kr->ccname == NULL) {
                DEBUG(1, ("expand_ccname_template failed.\n"));
                ret = ENOMEM;
                goto done;
            }

            ret = create_ccache_dir(kr, kr->ccname,
                                    kr->krb5_ctx->illegal_path_re,
                                    kr->uid, kr->gid, private_path);
            if (ret != EOK) {
                DEBUG(1, ("create_ccache_dir failed.\n"));
                goto done;
            }
    }

    if (kr->is_offline) {
        DEBUG(9, ("Preparing for offline operation.\n"));

        if (kr->valid_tgt_present || kr->active_ccache_present) {
            DEBUG(9, ("Valid TGT available or "
                      "ccache file is already in use.\n"));
            kr->ccname = kr->old_ccname;
            msg = talloc_asprintf(pd, "%s=%s", CCACHE_ENV_NAME, kr->ccname);
            if (msg == NULL) {
                DEBUG(1, ("talloc_asprintf failed.\n"));
            } else {
                ret = pam_add_response(pd, SSS_PAM_ENV_ITEM, strlen(msg) + 1,
                                       (uint8_t *) msg);
                if (ret != EOK) {
                    DEBUG(1, ("pam_add_response failed.\n"));
                }
            }

            if (dp_opt_get_bool(kr->krb5_ctx->opts,
                                KRB5_STORE_PASSWORD_IF_OFFLINE)) {
                krb5_pam_handler_cache_auth_step(req);
                return;
            }

            state->pam_status = PAM_AUTHINFO_UNAVAIL;
            state->dp_err = DP_ERR_OFFLINE;
            ret = EOK;
            goto done;

        }
    }

    /* We need to keep the root privileges to read the keytab file if
     * validation or FAST is enabled, otherwise we can drop them and run
     * krb5_child with user privileges.
     * If we are offline we want to create an empty ccache file. In this
     * case we can drop the privileges, too. */
    if ((dp_opt_get_bool(kr->krb5_ctx->opts, KRB5_VALIDATE) ||
         kr->krb5_ctx->use_fast) &&
        !kr->is_offline) {
        kr->run_as_user = false;
    } else {
        kr->run_as_user = true;
    }

    subreq = handle_child_send(state, state->ev, kr);
    if (subreq == NULL) {
        DEBUG(1, ("handle_child_send failed.\n"));
        ret = ENOMEM;
        goto done;
    }

    tevent_req_set_callback(subreq, krb5_child_done, req);
    return;

done:
    if (ret == EOK) {
        tevent_req_done(req);
    } else {
        tevent_req_error(req, ret);
    }
}

static struct tevent_req *krb5_next_server(struct tevent_req *req);
static struct tevent_req *krb5_next_kdc(struct tevent_req *req);
static struct tevent_req *krb5_next_kpasswd(struct tevent_req *req);

static void krb5_child_done(struct tevent_req *subreq)
{
    struct tevent_req *req = tevent_req_callback_data(subreq, struct tevent_req);
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);

    struct krb5child_req *kr = state->kr;
    struct pam_data *pd = state->pd;
    int ret;
    uint8_t *buf = NULL;
    ssize_t len = -1;
    ssize_t pref_len;
    size_t p;
    int32_t msg_status;
    int32_t msg_type;
    int32_t msg_len;
    int64_t time_data;
    struct tgt_times tgtt;

    memset(&tgtt, 0, sizeof(tgtt));

    ret = handle_child_recv(subreq, pd, &buf, &len);
    talloc_zfree(subreq);
    if (ret != EOK) {
        DEBUG(1, ("child failed (%d [%s])\n", ret, strerror(ret)));
        if (ret == ETIMEDOUT) {
            if (krb5_next_server(req) == NULL) {
                tevent_req_error(req, ENOMEM);
            }
        } else {
            tevent_req_error(req, ret);
        }
        return;
    }

    /* A buffer with the following structure is expected.
     * int32_t status of the request (required)
     * message (zero or more)
     *
     * A message consists of:
     * int32_t type of the message
     * int32_t length of the following data
     * uint8_t[len] data
     */

    if ((size_t) len < sizeof(int32_t)) {
        DEBUG(1, ("message too short.\n"));
        ret = EINVAL;
        goto done;
    }

    p=0;
    SAFEALIGN_COPY_INT32(&msg_status, buf+p, &p);

    while (p < len) {
        SAFEALIGN_COPY_INT32(&msg_type, buf+p, &p);
        SAFEALIGN_COPY_INT32(&msg_len, buf+p, &p);

        DEBUG(9, ("child response [%d][%d][%d].\n", msg_status, msg_type,
                                                    msg_len));

        if ((p + msg_len) > len) {
            DEBUG(1, ("message format error [%d] > [%d].\n", p+msg_len, len));
            ret = EINVAL;
            goto done;
        }

        /* We need to save the name of the credential cache file. To find it
         * we check if the data part of a message starts with
         * CCACHE_ENV_NAME"=". pref_len also counts the trailing '=' because
         * sizeof() counts the trailing '\0' of a string. */
        pref_len = sizeof(CCACHE_ENV_NAME);
        if (msg_len > pref_len &&
            strncmp((const char *) &buf[p], CCACHE_ENV_NAME"=", pref_len) == 0) {
            kr->ccname = talloc_strndup(kr, (char *) &buf[p+pref_len],
                                        msg_len-pref_len);
            if (kr->ccname == NULL) {
                DEBUG(1, ("talloc_strndup failed.\n"));
                ret = ENOMEM;
                goto done;
            }
        }

        if (msg_type == SSS_KRB5_INFO_TGT_LIFETIME &&
            msg_len == 4*sizeof(int64_t)) {
            SAFEALIGN_COPY_INT64(&time_data, buf+p, NULL);
            tgtt.authtime = int64_to_time_t(time_data);
            SAFEALIGN_COPY_INT64(&time_data, buf+p+sizeof(int64_t), NULL);
            tgtt.starttime = int64_to_time_t(time_data);
            SAFEALIGN_COPY_INT64(&time_data, buf+p+2*sizeof(int64_t), NULL);
            tgtt.endtime = int64_to_time_t(time_data);
            SAFEALIGN_COPY_INT64(&time_data, buf+p+3*sizeof(int64_t), NULL);
            tgtt.renew_till = int64_to_time_t(time_data);
            DEBUG(7, ("TGT times are [%d][%d][%d][%d].\n", tgtt.authtime,
                      tgtt.starttime, tgtt.endtime, tgtt.renew_till));
        }

        ret = pam_add_response(pd, msg_type, msg_len, &buf[p]);
        if (ret != EOK) {
            /* This is not a fatal error */
            DEBUG(1, ("pam_add_response failed.\n"));
        }
        p += msg_len;

        if ((p < len) && (p + 2*sizeof(int32_t) >= len)) {
            DEBUG(1, ("The remainder of the message is too short.\n"));
            ret = EINVAL;
            goto done;
        }
    }

    /* If the child request failed, but did not return an offline error code,
     * return with the status */
    if (msg_status != PAM_SUCCESS && msg_status != PAM_AUTHINFO_UNAVAIL &&
        msg_status != PAM_AUTHTOK_LOCK_BUSY) {
        state->pam_status = msg_status;
        state->dp_err = DP_ERR_OK;
        ret = EOK;
        goto done;
    } else {
        state->pam_status = msg_status;
    }

    /* If the child request was successful and we run the first pass of the
     * change password request just return success. */
    if (msg_status == PAM_SUCCESS && pd->cmd == SSS_PAM_CHAUTHTOK_PRELIM) {
        state->pam_status = PAM_SUCCESS;
        state->dp_err = DP_ERR_OK;
        ret = EOK;
        goto done;
    }

    /* if using a dedicated kpasswd server.. */
    if (kr->kpasswd_srv != NULL) {
        /* ..which is unreachable by now.. */
        if (msg_status == PAM_AUTHTOK_LOCK_BUSY) {
            fo_set_port_status(kr->kpasswd_srv, PORT_NOT_WORKING);
            /* ..try to resolve next kpasswd server */
            if (krb5_next_kpasswd(req) == NULL) {
                tevent_req_error(req, ENOMEM);
            }
            return;
        } else {
            fo_set_port_status(kr->kpasswd_srv, PORT_WORKING);
        }
    }

    /* if the KDC for auth (PAM_AUTHINFO_UNAVAIL) or
     * chpass (PAM_AUTHTOK_LOCK_BUSY) was not available while using KDC
     * also for chpass operation... */
    if (msg_status == PAM_AUTHINFO_UNAVAIL ||
        (kr->kpasswd_srv == NULL && msg_status == PAM_AUTHTOK_LOCK_BUSY)) {
        if (kr->srv != NULL) {
            fo_set_port_status(kr->srv, PORT_NOT_WORKING);
            /* ..try to resolve next KDC */
            if (krb5_next_kdc(req) == NULL) {
                tevent_req_error(req, ENOMEM);
            }
            return;
        }
    } else if (kr->srv != NULL) {
        fo_set_port_status(kr->srv, PORT_WORKING);
    }

    /* Now only a successful authentication or password change is left.
     *
     * We expect that one of the messages in the received buffer contains
     * the name of the credential cache file. */
    if (kr->ccname == NULL) {
        DEBUG(1, ("Missing ccache name in child response.\n"));
        ret = EINVAL;
        goto done;
    }

    if (kr->old_ccname != NULL) {
        ret = safe_remove_old_ccache_file(kr->old_ccname, kr->ccname);
        if (ret != EOK) {
            DEBUG(1, ("Failed to remove old ccache file [%s], please remove it manually.\n"));
        }
    }

    struct sysdb_attrs *attrs;
    attrs = sysdb_new_attrs(state);
    ret = sysdb_attrs_add_string(attrs, SYSDB_CCACHE_FILE, kr->ccname);
    if (ret != EOK) {
        DEBUG(1, ("sysdb_attrs_add_string failed.\n"));
        goto done;
    }

    ret = krb5_save_ccname(state, state->be_ctx->sysdb,
                           state->be_ctx->domain,
                           pd->user, kr->ccname);
    if (ret) {
        DEBUG(1, ("krb5_save_ccname_send failed.\n"));
        goto done;
    }

    if (msg_status == PAM_SUCCESS &&
        dp_opt_get_int(kr->krb5_ctx->opts, KRB5_RENEW_INTERVAL) > 0 &&
        (pd->cmd == SSS_PAM_AUTHENTICATE || pd->cmd == SSS_CMD_RENEW ||
         pd->cmd == SSS_PAM_CHAUTHTOK) &&
        tgtt.renew_till > tgtt.endtime && kr->ccname != NULL) {
        DEBUG(7, ("Adding [%s] for automatic renewal.\n", kr->ccname));
        ret = add_tgt_to_renew_table(kr->krb5_ctx, kr->ccname, &tgtt, pd,
                                     kr->upn);
        if (ret != EOK) {
            DEBUG(1, ("add_tgt_to_renew_table failed, "
                      "automatic renewal not possible.\n"));
        }
    }

    krb5_save_ccname_done(req);

    return;

done:
    if (ret == EOK) {
        tevent_req_done(req);
    } else {
        tevent_req_error(req, ret);
    }
}

static struct tevent_req *krb5_next_server(struct tevent_req *req)
{
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    struct pam_data *pd = state->pd;
    struct tevent_req *next_req = NULL;

    switch (pd->cmd) {
        case SSS_PAM_AUTHENTICATE:
        case SSS_CMD_RENEW:
            fo_set_port_status(state->kr->srv, PORT_NOT_WORKING);
            next_req = krb5_next_kdc(req);
            break;
        case SSS_PAM_CHAUTHTOK:
        case SSS_PAM_CHAUTHTOK_PRELIM:
            if (state->kr->kpasswd_srv) {
                fo_set_port_status(state->kr->kpasswd_srv, PORT_NOT_WORKING);
                next_req = krb5_next_kpasswd(req);
                break;
            } else {
                fo_set_port_status(state->kr->srv, PORT_NOT_WORKING);
                next_req = krb5_next_kdc(req);
                break;
            }
        default:
            DEBUG(1, ("Unexpected PAM task\n"));
    }

    return next_req;
}

static struct tevent_req *krb5_next_kdc(struct tevent_req *req)
{
    struct tevent_req *next_req;
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);

    next_req = be_resolve_server_send(state, state->ev,
                                      state->be_ctx,
                                      state->krb5_ctx->service->name);
    if (next_req == NULL) {
        DEBUG(1, ("be_resolve_server_send failed.\n"));
        return NULL;
    }
    tevent_req_set_callback(next_req, krb5_resolve_kdc_done, req);

    return next_req;
}

static struct tevent_req *krb5_next_kpasswd(struct tevent_req *req)
{
    struct tevent_req *next_req;
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);

    next_req = be_resolve_server_send(state, state->ev,
                                state->be_ctx,
                                state->krb5_ctx->kpasswd_service->name);
    if (next_req == NULL) {
        DEBUG(1, ("be_resolve_server_send failed.\n"));
        return NULL;
    }
    tevent_req_set_callback(next_req, krb5_resolve_kpasswd_done, req);

    return next_req;
}

static void krb5_save_ccname_done(struct tevent_req *req)
{
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    struct krb5child_req *kr = state->kr;
    struct pam_data *pd = state->pd;
    int ret;
    char *password = NULL;

    if (kr->is_offline) {
        if (dp_opt_get_bool(kr->krb5_ctx->opts,KRB5_STORE_PASSWORD_IF_OFFLINE)) {
            krb5_pam_handler_cache_auth_step(req);
            return;
        }

        DEBUG(4, ("Backend is marked offline, retry later!\n"));
        state->pam_status = PAM_AUTHINFO_UNAVAIL;
        state->dp_err = DP_ERR_OFFLINE;
        ret = EOK;
        goto done;
    }

    if (state->be_ctx->domain->cache_credentials == TRUE) {

        /* password caching failures are not fatal errors */
        state->pam_status = PAM_SUCCESS;
        state->dp_err = DP_ERR_OK;

        switch(pd->cmd) {
            case SSS_CMD_RENEW:
                /* The authtok is set to the credential cache
                 * during renewal. We don't want to save this
                 * as the cached password.
                 */
                break;
            case SSS_PAM_AUTHENTICATE:
            case SSS_PAM_CHAUTHTOK_PRELIM:
                password = talloc_size(state, pd->authtok_size + 1);
                if (password != NULL) {
                    memcpy(password, pd->authtok, pd->authtok_size);
                    password[pd->authtok_size] = '\0';
                }
                break;
            case SSS_PAM_CHAUTHTOK:
                password = talloc_size(state, pd->newauthtok_size + 1);
                if (password != NULL) {
                    memcpy(password, pd->newauthtok, pd->newauthtok_size);
                    password[pd->newauthtok_size] = '\0';
                }
                break;
            default:
                DEBUG(0, ("unsupported PAM command [%d].\n", pd->cmd));
        }

        if (password == NULL) {
            if (pd->cmd != SSS_CMD_RENEW) {
                DEBUG(0, ("password not available, offline auth may not work.\n"));
                /* password caching failures are not fatal errors */
            }
            ret = EOK;
            goto done;
        }

        talloc_set_destructor((TALLOC_CTX *)password, password_destructor);

        ret = sysdb_cache_password(state, state->be_ctx->sysdb,
                                   state->be_ctx->domain, pd->user,
                                   password);
        if (ret) {
            DEBUG(2, ("Failed to cache password, offline auth may not work."
                      " (%d)[%s]!?\n", ret, strerror(ret)));
            /* password caching failures are not fatal errors */
        }
    }

    state->pam_status = PAM_SUCCESS;
    state->dp_err = DP_ERR_OK;
    ret = EOK;

done:
    if (ret == EOK) {
        tevent_req_done(req);
    } else {
        tevent_req_error(req, ret);
    }

}

static void krb5_pam_handler_cache_auth_step(struct tevent_req *req)
{
    struct krb5_auth_state *state = tevent_req_data(req, struct krb5_auth_state);
    struct pam_data *pd = state->pd;
    struct krb5_ctx *krb5_ctx = state->kr->krb5_ctx;
    int ret;

    ret = sysdb_cache_auth(state, state->be_ctx->sysdb, state->be_ctx->domain,
                           pd->user, pd->authtok, pd->authtok_size,
                           state->be_ctx->cdb, true, NULL, NULL);
    if (ret != EOK) {
        DEBUG(1, ("Offline authentication failed\n"));
        state->pam_status = PAM_SYSTEM_ERR;
        state->dp_err = DP_ERR_OK;
    } else {
        ret = add_user_to_delayed_online_authentication(krb5_ctx, pd,
                                                       state->kr->uid);
        if (ret != EOK) {
            /* This error is not fatal */
            DEBUG(1, ("add_user_to_delayed_online_authentication failed.\n"));
        }
        state->pam_status = PAM_AUTHINFO_UNAVAIL;
        state->dp_err = DP_ERR_OFFLINE;
    }

    tevent_req_done(req);
}

static void krb_reply(struct be_req *req, int dp_err, int result)
{
    req->fn(req, dp_err, result, NULL);
}

void krb5_auth_done(struct tevent_req *req);
static void krb5_access_done(struct tevent_req *req);

void krb5_pam_handler(struct be_req *be_req)
{
    struct tevent_req *req;
    struct pam_data *pd;
    struct krb5_ctx *krb5_ctx;
    int dp_err = DP_ERR_FATAL;
    int ret;

    pd = talloc_get_type(be_req->req_data, struct pam_data);
    pd->pam_status = PAM_SYSTEM_ERR;

    krb5_ctx = get_krb5_ctx(be_req);
    if (krb5_ctx == NULL) {
        DEBUG(1, ("Kerberos context not available.\n"));
        goto done;
    }

    switch (pd->cmd) {
        case SSS_PAM_AUTHENTICATE:
        case SSS_CMD_RENEW:
        case SSS_PAM_CHAUTHTOK_PRELIM:
        case SSS_PAM_CHAUTHTOK:
            ret = add_to_wait_queue(be_req, pd, krb5_ctx);
            if (ret == EOK) {
                DEBUG(7, ("Request successfully added to wait queue "
                          "of user [%s].\n", pd->user));
                return;
            } else if (ret == ENOENT) {
                DEBUG(7, ("Wait queue of user [%s] is empty, "
                          "running request immediately.\n", pd->user));
            } else {
                DEBUG(7, ("Failed to add request to wait queue of user [%s], "
                          "running request immediately.\n", pd->user));
            }

            req = krb5_auth_send(be_req, be_req->be_ctx->ev, be_req->be_ctx, pd,
                                 krb5_ctx);
            if (req == NULL) {
                DEBUG(1, ("krb5_auth_send failed.\n"));
                goto done;
            }

            tevent_req_set_callback(req, krb5_auth_done, be_req);
            break;
        case SSS_PAM_ACCT_MGMT:
            req = krb5_access_send(be_req, be_req->be_ctx->ev, be_req->be_ctx,
                                   pd, krb5_ctx);
            if (req == NULL) {
                DEBUG(1, ("krb5_access_send failed.\n"));
                goto done;
            }

            tevent_req_set_callback(req, krb5_access_done, be_req);
            break;
        case SSS_PAM_SETCRED:
        case SSS_PAM_OPEN_SESSION:
        case SSS_PAM_CLOSE_SESSION:
            pd->pam_status = PAM_SUCCESS;
            dp_err = DP_ERR_OK;
            goto done;
            break;
        default:
            DEBUG(4, ("krb5 does not handles pam task %d.\n", pd->cmd));
            pd->pam_status = PAM_MODULE_UNKNOWN;
            dp_err = DP_ERR_OK;
            goto done;
    }

    return;

done:
    krb_reply(be_req, dp_err, pd->pam_status);
}

void krb5_auth_done(struct tevent_req *req)
{
    int ret;
    struct be_req *be_req = tevent_req_callback_data(req, struct be_req);
    int pam_status;
    int dp_err;
    struct pam_data *pd;
    struct krb5_ctx *krb5_ctx;

    pd = talloc_get_type(be_req->req_data, struct pam_data);

    ret = krb5_auth_recv(req, &pam_status, &dp_err);
    talloc_zfree(req);
    if (ret) {
        pd->pam_status = PAM_SYSTEM_ERR;
        dp_err = DP_ERR_OK;
    } else {
        pd->pam_status = pam_status;
    }

    krb5_ctx = get_krb5_ctx(be_req);
    if (krb5_ctx != NULL) {
        check_wait_queue(krb5_ctx, pd->user);
    } else {
        DEBUG(1, ("Kerberos context not available.\n"));
    }

    krb_reply(be_req, dp_err, pd->pam_status);
}

static void krb5_access_done(struct tevent_req *req)
{
    int ret;
    struct be_req *be_req = tevent_req_callback_data(req, struct be_req);
    bool access_allowed;
    struct pam_data *pd;
    int dp_err = DP_ERR_OK;

    pd = talloc_get_type(be_req->req_data, struct pam_data);
    pd->pam_status = PAM_SYSTEM_ERR;

    ret = krb5_access_recv(req, &access_allowed);
    talloc_zfree(req);
    if (ret != EOK) {
        DEBUG(1, ("krb5_access request failed [%d][%s]\n", ret, strerror(ret)));
        goto done;
    }

    DEBUG(7, ("Access %s for user [%s].\n",
              access_allowed ? "allowed" : "denied", pd->user));
    pd->pam_status = access_allowed ? PAM_SUCCESS : PAM_PERM_DENIED;
    dp_err = DP_ERR_OK;

done:
    krb_reply(be_req, dp_err, pd->pam_status);
}