/*      $NetBSD: pam_krb5.c,v 1.32 2023/09/28 02:31:04 riastradh Exp $  */

/*-
 * This pam_krb5 module contains code that is:
 *   Copyright (c) Derrick J. Brashear, 1996. All rights reserved.
 *   Copyright (c) Frank Cusack, 1999-2001. All rights reserved.
 *   Copyright (c) Jacques A. Vidrine, 2000-2001. All rights reserved.
 *   Copyright (c) Nicolas Williams, 2001. All rights reserved.
 *   Copyright (c) Perot Systems Corporation, 2001. All rights reserved.
 *   Copyright (c) Mark R V Murray, 2001.  All rights reserved.
 *   Copyright (c) Networks Associates Technology, Inc., 2002-2005.
 *       All rights reserved.
 *
 * Portions of this software were developed for the FreeBSD Project by
 * ThinkSec AS and NAI Labs, the Security Research Division of Network
 * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notices, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <sys/cdefs.h>
#ifdef __FreeBSD__
__FBSDID("$FreeBSD: src/lib/libpam/modules/pam_krb5/pam_krb5.c,v 1.22 2005/01/24 16:49:50 rwatson Exp $");
#else
__RCSID("$NetBSD: pam_krb5.c,v 1.32 2023/09/28 02:31:04 riastradh Exp $");
#endif

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

#include <krb5/krb5.h>
#include <krb5/com_err.h>
#include <krb5/parse_time.h>

#define PAM_SM_AUTH
#define PAM_SM_ACCOUNT
#define PAM_SM_PASSWORD

#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>
#include <security/openpam.h>

#define COMPAT_HEIMDAL
/* #define      COMPAT_MIT */

static void     log_krb5(krb5_context, krb5_error_code, struct syslog_data *,
    const char *, ...) __printflike(4, 5);
static int      verify_krb_v5_tgt_begin(krb5_context, char *, int,
    const char **, krb5_principal *, char[static BUFSIZ], struct syslog_data *);
static int      verify_krb_v5_tgt(krb5_context, krb5_ccache, char *, int,
    const char *, krb5_principal, char[static BUFSIZ], struct syslog_data *);
static void     verify_krb_v5_tgt_cleanup(krb5_context, int,
    const char *, krb5_principal, char[static BUFSIZ], struct syslog_data *);
static void     cleanup_cache(pam_handle_t *, void *, int);
static const    char *compat_princ_component(krb5_context, krb5_principal, int);
static void     compat_free_data_contents(krb5_context, krb5_data *);

#define USER_PROMPT             "Username: "
#define PASSWORD_PROMPT         "%s's password:"
#define NEW_PASSWORD_PROMPT     "New Password:"

#define PAM_OPT_CCACHE          "ccache"
#define PAM_OPT_DEBUG           "debug"
#define PAM_OPT_FORWARDABLE     "forwardable"
#define PAM_OPT_RENEWABLE       "renewable"
#define PAM_OPT_NO_CCACHE       "no_ccache"
#define PAM_OPT_REUSE_CCACHE    "reuse_ccache"
#define PAM_OPT_ALLOW_KDC_SPOOF "allow_kdc_spoof"

/*
 * authentication management
 */
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{
        krb5_error_code krbret;
        krb5_context pam_context;
        int debug;
        const char *auth_service;
        krb5_principal auth_princ;
        char auth_phost[BUFSIZ];
        struct syslog_data auth_data = SYSLOG_DATA_INIT;
        krb5_creds creds;
        krb5_principal princ;
        krb5_ccache ccache;
        krb5_get_init_creds_opt *opts = NULL;
        struct passwd *pwd, pwres;
        int retval;
        const void *ccache_data;
        const char *user, *pass;
        const void *sourceuser, *service;
        char *principal, *princ_name, *ccache_name, luser[32], *srvdup;
        char password_prompt[80];
        char pwbuf[1024];
        const char *rtime;

        princ_name = NULL;
        retval = pam_get_user(pamh, &user, USER_PROMPT);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got user: %s", user);

        retval = pam_get_item(pamh, PAM_RUSER, &sourceuser);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got ruser: %s", (const char *)sourceuser);

        service = NULL;
        pam_get_item(pamh, PAM_SERVICE, &service);
        if (service == NULL)
                service = "unknown";

        PAM_LOG("Got service: %s", (const char *)service);

        if ((srvdup = strdup(service)) == NULL) {
                retval = PAM_BUF_ERR;
                goto cleanup6;
        }

        krbret = krb5_init_context(&pam_context);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup5;
        }

        PAM_LOG("Context initialised");

        debug = openpam_get_option(pamh, PAM_OPT_DEBUG) ? 1 : 0;
        krbret = verify_krb_v5_tgt_begin(pam_context, srvdup, debug,
            &auth_service, &auth_princ, auth_phost, &auth_data);
        if (krbret != 0) {      /* failed to find key */
                /* Keytab or service key does not exist */
                if (debug)
                        log_krb5(pam_context, krbret, &auth_data,
                            "pam_krb5: verify_krb_v5_tgt: "
                            "krb5_kt_read_service_key");
                /*
                 * Give up now because we can't authenticate the KDC
                 * with a keytab, unless the administrator asked to
                 * have the traditional behaviour of being vulnerable
                 * to spoofed KDCs.
                 */
                if (!openpam_get_option(pamh, PAM_OPT_ALLOW_KDC_SPOOF)) {
                        retval = PAM_SERVICE_ERR;
                        goto cleanup4;
                }
        }

        krbret = krb5_get_init_creds_opt_alloc(pam_context, &opts);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup4;
        }

        if (openpam_get_option(pamh, PAM_OPT_FORWARDABLE))
                krb5_get_init_creds_opt_set_forwardable(opts, 1);

        if ((rtime = openpam_get_option(pamh, PAM_OPT_RENEWABLE)) != NULL) {
                krb5_deltat renew;
                char rbuf[80], *rp;

                if (*rtime) {
                        (void)strlcpy(rbuf, rtime, sizeof(rbuf));
                        rtime = rbuf;
                        for (rp = rbuf; *rp; rp++)
                                if (*rp == '_')
                                        *rp = ' ';
                }
                else
                        rtime = "1 month";
                renew = parse_time(rtime, "s");
                krb5_get_init_creds_opt_set_renew_life(opts, renew);
        }



        PAM_LOG("Credentials initialised");

        krbret = krb5_cc_register(pam_context, &krb5_mcc_ops, FALSE);
        if (krbret != 0 && krbret != KRB5_CC_TYPE_EXISTS) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }

        PAM_LOG("Done krb5_cc_register()");

        /* Get principal name */
        if (openpam_get_option(pamh, PAM_OPT_AUTH_AS_SELF))
                asprintf(&principal, "%s/%s", (const char *)sourceuser, user);
        else
                principal = strdup(user);

        PAM_LOG("Created principal: %s", principal);

        krbret = krb5_parse_name(pam_context, principal, &princ);
        free(principal);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_parse_name");
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }

        PAM_LOG("Done krb5_parse_name()");

        /* Now convert the principal name into something human readable */
        krbret = krb5_unparse_name(pam_context, princ, &princ_name);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_unparse_name");
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        PAM_LOG("Got principal: %s", princ_name);

        /* Get password */
        (void) snprintf(password_prompt, sizeof(password_prompt),
            PASSWORD_PROMPT, princ_name);
        retval = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, password_prompt);
        if (retval != PAM_SUCCESS)
                goto cleanup2;

        PAM_LOG("Got password");

        /* Verify the local user exists (AFTER getting the password) */
        if (strchr(user, '@')) {
                /* get a local account name for this principal */
                krbret = krb5_aname_to_localname(pam_context, princ,
                    sizeof(luser), luser);
                if (krbret != 0) {
                        PAM_VERBOSE_ERROR("Kerberos 5 error");
                        log_krb5(pam_context, krbret, NULL,
                            "krb5_aname_to_localname");
                        retval = PAM_USER_UNKNOWN;
                        goto cleanup2;
                }

                retval = pam_set_item(pamh, PAM_USER, luser);
                if (retval != PAM_SUCCESS)
                        goto cleanup2;

                PAM_LOG("PAM_USER Redone");
        }

        if (getpwnam_r(user, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
            pwd == NULL) {
                retval = PAM_USER_UNKNOWN;
                goto cleanup2;
        }

        PAM_LOG("Done getpwnam_r()");

        /* Get a TGT */
        memset(&creds, 0, sizeof(krb5_creds));
        krbret = krb5_get_init_creds_password(pam_context, &creds, princ,
            pass, NULL, pamh, 0, NULL, opts);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                log_krb5(pam_context, krbret, NULL,
                    "krb5_get_init_creds_password");
                retval = PAM_AUTH_ERR;
                goto cleanup2;
        }

        PAM_LOG("Got TGT");

        /* Generate a temporary cache */
        krbret = krb5_cc_new_unique(pam_context, "MEMORY", NULL, &ccache);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                log_krb5(pam_context, krbret, NULL, "krb5_cc_gen_new");
                retval = PAM_SERVICE_ERR;
                goto cleanup;
        }
        krbret = krb5_cc_initialize(pam_context, ccache, princ);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                log_krb5(pam_context, krbret, NULL, "krb5_cc_initialize");
                retval = PAM_SERVICE_ERR;
                goto cleanup;
        }
        krbret = krb5_cc_store_cred(pam_context, ccache, &creds);
        if (krbret != 0) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                log_krb5(pam_context, krbret, NULL, "krb5_cc_store_cred");
                krb5_cc_destroy(pam_context, ccache);
                retval = PAM_SERVICE_ERR;
                goto cleanup;
        }

        PAM_LOG("Credentials stashed");

        /* Verify them */
        krbret = verify_krb_v5_tgt(pam_context, ccache, srvdup,
            debug,
            auth_service, auth_princ, auth_phost, &auth_data);
        if (krbret == -1) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                krb5_cc_destroy(pam_context, ccache);
                retval = PAM_AUTH_ERR;
                goto cleanup;
        }

        PAM_LOG("Credentials stash verified");

        retval = pam_get_data(pamh, "ccache", &ccache_data);
        if (retval == PAM_SUCCESS) {
                krb5_cc_destroy(pam_context, ccache);
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_AUTH_ERR;
                goto cleanup;
        }

        PAM_LOG("Credentials stash not pre-existing");

        asprintf(&ccache_name, "%s:%s", krb5_cc_get_type(pam_context,
                ccache), krb5_cc_get_name(pam_context, ccache));
        if (ccache_name == NULL) {
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_BUF_ERR;
                goto cleanup;
        }
        retval = pam_set_data(pamh, "ccache", ccache_name, cleanup_cache);
        if (retval != 0) {
                krb5_cc_destroy(pam_context, ccache);
                PAM_VERBOSE_ERROR("Kerberos 5 error");
                retval = PAM_SERVICE_ERR;
                goto cleanup;
        }

        PAM_LOG("Credentials stash saved");

cleanup:
        krb5_free_cred_contents(pam_context, &creds);
        PAM_LOG("Done cleanup");
cleanup2:
        krb5_free_principal(pam_context, princ);
        PAM_LOG("Done cleanup2");
cleanup3:
        if (princ_name)
                free(princ_name);

        if (opts)
                krb5_get_init_creds_opt_free(pam_context, opts);
cleanup4:
        verify_krb_v5_tgt_cleanup(pam_context, debug,
            auth_service, auth_princ, auth_phost, &auth_data);

        krb5_free_context(pam_context);
cleanup5:
        free(srvdup);

        PAM_LOG("Done cleanup5");
cleanup6:
        if (retval != PAM_SUCCESS)
                PAM_VERBOSE_ERROR("Kerberos 5 refuses you");

        return (retval);
}

PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh, int flags,
    int argc __unused, const char *argv[] __unused)
{

        krb5_error_code krbret;
        krb5_context pam_context;
        krb5_principal princ;
        krb5_creds creds;
        krb5_ccache ccache_temp, ccache_perm;
        krb5_cc_cursor cursor;
        struct passwd *pwd = NULL, pwres;
        int retval;
        const char *cache_name, *q;
        const void *user;
        const void *cache_data;
        char *cache_name_buf = NULL, *p, *cache_name_buf2 = NULL;
        char pwbuf[1024];

        uid_t euid;
        gid_t egid;

        if (flags & PAM_DELETE_CRED)
                return (PAM_SUCCESS); /* XXX */

        if (!(flags & (PAM_REFRESH_CRED|PAM_REINITIALIZE_CRED|PAM_ESTABLISH_CRED)))
                return (PAM_SERVICE_ERR);

        /* If a persistent cache isn't desired, stop now. */
        if (openpam_get_option(pamh, PAM_OPT_NO_CCACHE))
                return (PAM_SUCCESS);

        PAM_LOG("Establishing credentials");

        /* Get username */
        retval = pam_get_item(pamh, PAM_USER, &user);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got user: %s", (const char *)user);

        krbret = krb5_init_context(&pam_context);
        if (krbret != 0) {
                PAM_LOG("Error krb5_init_context() failed");
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Context initialised");

        euid = geteuid();       /* Usually 0 */
        egid = getegid();

        PAM_LOG("Got euid, egid: %d %d", euid, egid);

        /* Retrieve the temporary cache */
        retval = pam_get_data(pamh, "ccache", &cache_data);
        if (retval != PAM_SUCCESS) {
                retval = PAM_CRED_UNAVAIL;
                goto cleanup3;
        }
        krbret = krb5_cc_resolve(pam_context, cache_data, &ccache_temp);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_resolve(\"%s\")",
                    (const char *)cache_data);
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }

        /* Get the uid. This should exist. */
        if (getpwnam_r(user, &pwres, pwbuf, sizeof(pwbuf), &pwd) != 0 ||
            pwd == NULL) {
                retval = PAM_USER_UNKNOWN;
                goto cleanup3;
        }

        PAM_LOG("Done getpwnam_r()");

        /* Avoid following a symlink as root */
        if (setegid(pwd->pw_gid)) {
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }
        if (seteuid(pwd->pw_uid)) {
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }

        PAM_LOG("Done setegid() & seteuid()");

        if (flags & (PAM_REFRESH_CRED|PAM_REINITIALIZE_CRED)) {
                cache_name = getenv("KRB5CCNAME");
                if (!cache_name)
                        goto cleanup3;
        } else {
                size_t len = PATH_MAX + 16;
                /* Get the cache name */
                cache_name = openpam_get_option(pamh, PAM_OPT_CCACHE);
                if (cache_name == NULL) {
                        asprintf(&cache_name_buf, "FILE:/tmp/krb5cc_%d", pwd->pw_uid);
                        cache_name = cache_name_buf;
                }

                cache_name_buf2 = p = calloc(len, sizeof(char));
                q = cache_name;
        
                if (p == NULL) {
                        PAM_LOG("Error malloc(): failure");
                        retval = PAM_BUF_ERR;
                        goto cleanup3;
                }
                cache_name = p;

                /* convert %u and %p */
                while (*q) {
                        int l;
                        if (*q == '%') {
                                q++;
                                if (*q == 'u') {
                                        l = snprintf(p, len, "%d", pwd->pw_uid);
                                }
                                else if (*q == 'p') {
                                        l = snprintf(p, len, "%d", getpid());
                                }
                                else {
                                        /* Not a special token */
                                        if (!len)
                                                goto truncated;
                                        *p = '%';
                                        l = 1;
                                        q--;
                                }
                                if ((size_t)l > len) {
truncated:                              PAM_LOG("string truncation failure");
                                        retval = PAM_BUF_ERR;
                                        goto cleanup3;
                                }
                                q++;
                        }
                        else {
                                if (!len)
                                        goto truncated;
                                *p = *q++;
                                l = 1;
                        }
                        p += l;
                        len -= (size_t)l;
                }
                if (!len)
                        goto truncated;
                *p = '\0';
        }

        PAM_LOG("Got cache_name: %s", cache_name);

        /* Initialize the new ccache */
        krbret = krb5_cc_get_principal(pam_context, ccache_temp, &princ);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_get_principal");
                retval = PAM_SERVICE_ERR;
                goto cleanup3;
        }
        krbret = krb5_cc_resolve(pam_context, cache_name, &ccache_perm);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_resolve");
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        krbret = krb5_cc_initialize(pam_context, ccache_perm, princ);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_initialize");
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        PAM_LOG("Cache initialised");

        /* Prepare for iteration over creds */
        krbret = krb5_cc_start_seq_get(pam_context, ccache_temp, &cursor);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_start_seq_get");
                krb5_cc_destroy(pam_context, ccache_perm);
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        PAM_LOG("Prepared for iteration");

        /* Copy the creds (should be two of them) */
        while ((krbret = krb5_cc_next_cred(pam_context, ccache_temp,
                                &cursor, &creds)) == 0) {

                krbret = krb5_cc_store_cred(pam_context, ccache_perm, &creds);
                if (krbret != 0) {
                        log_krb5(pam_context, krbret, NULL,
                            "krb5_cc_store_cred");
                        krb5_cc_destroy(pam_context, ccache_perm);
                        krb5_free_cred_contents(pam_context, &creds);
                        retval = PAM_SERVICE_ERR;
                        goto cleanup2;
                }

                krb5_free_cred_contents(pam_context, &creds);
                PAM_LOG("Iteration");
        }

        krb5_cc_end_seq_get(pam_context, ccache_temp, &cursor);

        PAM_LOG("Done iterating");

        if (flags & PAM_ESTABLISH_CRED) {
                if (strstr(cache_name, "FILE:") == cache_name) {
                        if (chown(&cache_name[5], pwd->pw_uid, pwd->pw_gid) == -1) {
                                PAM_LOG("Error chown(): %s", strerror(errno));
                                krb5_cc_destroy(pam_context, ccache_perm);
                                retval = PAM_SERVICE_ERR;
                                goto cleanup2;
                        }
                        PAM_LOG("Done chown()");

                        if (chmod(&cache_name[5], (S_IRUSR | S_IWUSR)) == -1) {
                                PAM_LOG("Error chmod(): %s", strerror(errno));
                                krb5_cc_destroy(pam_context, ccache_perm);
                                retval = PAM_SERVICE_ERR;
                                goto cleanup2;
                        }
                        PAM_LOG("Done chmod()");
                }
        }

        krb5_cc_close(pam_context, ccache_perm);

        PAM_LOG("Cache closed");

        retval = pam_setenv(pamh, "KRB5CCNAME", cache_name, 1);
        if (retval != PAM_SUCCESS) {
                PAM_LOG("Error pam_setenv(): %s", pam_strerror(pamh, retval));
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        PAM_LOG("Environment done: KRB5CCNAME=%s", cache_name);

cleanup2:
        krb5_free_principal(pam_context, princ);
        PAM_LOG("Done cleanup2");
cleanup3:
        krb5_free_context(pam_context);
        PAM_LOG("Done cleanup3");

        seteuid(euid);
        setegid(egid);

        PAM_LOG("Done seteuid() & setegid()");

        if (cache_name_buf != NULL)
                free(cache_name_buf);
        if (cache_name_buf2 != NULL)
                free(cache_name_buf2);

        return (retval);
}

/*
 * account management
 */
PAM_EXTERN int
pam_sm_acct_mgmt(pam_handle_t *pamh, int flags __unused,
    int argc __unused, const char *argv[] __unused)
{
        krb5_error_code krbret;
        krb5_context pam_context;
        krb5_ccache ccache;
        krb5_principal princ;
        int retval;
        const void *user;
        const void *ccache_name;

        retval = pam_get_item(pamh, PAM_USER, &user);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got user: %s", (const char *)user);

        retval = pam_get_data(pamh, "ccache", &ccache_name);
        if (retval != PAM_SUCCESS)
                return (PAM_SUCCESS);

        PAM_LOG("Got credentials");

        krbret = krb5_init_context(&pam_context);
        if (krbret != 0) {
                PAM_LOG("Error krb5_init_context() failed");
                return (PAM_PERM_DENIED);
        }

        PAM_LOG("Context initialised");

        krbret = krb5_cc_resolve(pam_context, (const char *)ccache_name, &ccache);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_resolve(\"%s\")",
                    (const char *)ccache_name);
                krb5_free_context(pam_context);
                return (PAM_PERM_DENIED);
        }

        PAM_LOG("Got ccache %s", (const char *)ccache_name);


        krbret = krb5_cc_get_principal(pam_context, ccache, &princ);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_cc_get_principal");
                retval = PAM_PERM_DENIED;
                goto cleanup;
        }

        PAM_LOG("Got principal");

        if (krb5_kuserok(pam_context, princ, (const char *)user))
                retval = PAM_SUCCESS;
        else
                retval = PAM_PERM_DENIED;
        krb5_free_principal(pam_context, princ);

        PAM_LOG("Done kuserok()");

cleanup:
        krb5_free_context(pam_context);
        PAM_LOG("Done cleanup");

        return (retval);

}

/*
 * password management
 */
PAM_EXTERN int
pam_sm_chauthtok(pam_handle_t *pamh, int flags,
    int argc __unused, const char *argv[] __unused)
{
        krb5_error_code krbret;
        krb5_context pam_context;
        krb5_creds creds;
        krb5_principal princ;
        krb5_get_init_creds_opt *opts;
        krb5_data result_code_string, result_string;
        int result_code, retval;
        const char *pass;
        const void *user;
        char *princ_name, *passdup;
        char password_prompt[80];

        princ_name = NULL;
        if (flags & PAM_PRELIM_CHECK) {
                /* Nothing to do here. */
                return (PAM_SUCCESS);
        }

        if (!(flags & PAM_UPDATE_AUTHTOK)) {
                PAM_LOG("Illegal flags argument");
                return (PAM_ABORT);
        }

        retval = pam_get_item(pamh, PAM_USER, &user);
        if (retval != PAM_SUCCESS)
                return (retval);

        PAM_LOG("Got user: %s", (const char *)user);

        krbret = krb5_init_context(&pam_context);
        if (krbret != 0) {
                PAM_LOG("Error krb5_init_context() failed");
                return (PAM_SERVICE_ERR);
        }

        PAM_LOG("Context initialised");

        krbret = krb5_get_init_creds_opt_alloc(pam_context, &opts);
        if (krbret != 0) {
                PAM_LOG("Error krb5_init_context() failed");
                return (PAM_SERVICE_ERR);
        }

        krb5_get_init_creds_opt_set_tkt_life(opts, 300);
        krb5_get_init_creds_opt_set_forwardable(opts, FALSE);
        krb5_get_init_creds_opt_set_proxiable(opts, FALSE);

        PAM_LOG("Credentials options initialised");

        /* Get principal name */
        krbret = krb5_parse_name(pam_context, (const char *)user, &princ);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_parse_name");
                retval = PAM_USER_UNKNOWN;
                goto cleanup3;
        }

        /* Now convert the principal name into something human readable */
        krbret = krb5_unparse_name(pam_context, princ, &princ_name);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "krb5_unparse_name");
                retval = PAM_SERVICE_ERR;
                goto cleanup2;
        }

        PAM_LOG("Got principal: %s", princ_name);

        /* Get password */
        (void) snprintf(password_prompt, sizeof(password_prompt),
            PASSWORD_PROMPT, princ_name);
        retval = pam_get_authtok(pamh, PAM_OLDAUTHTOK, &pass, password_prompt);
        if (retval != PAM_SUCCESS)
                goto cleanup2;

        PAM_LOG("Got password");

        memset(&creds, 0, sizeof(krb5_creds));
        krbret = krb5_get_init_creds_password(pam_context, &creds, princ,
            pass, NULL, pamh, 0, "kadmin/changepw", opts);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL,
                    "krb5_get_init_creds_password");
                retval = PAM_AUTH_ERR;
                goto cleanup2;
        }

        PAM_LOG("Credentials established");

        /* Now get the new password */
        for (;;) {
                retval = pam_get_authtok(pamh,
                    PAM_AUTHTOK, &pass, NEW_PASSWORD_PROMPT);
                if (retval != PAM_TRY_AGAIN)
                        break;
                pam_error(pamh, "Mismatch; try again, EOF to quit.");
        }
        if (retval != PAM_SUCCESS)
                goto cleanup;

        PAM_LOG("Got new password");

        /* Change it */
        if ((passdup = strdup(pass)) == NULL) {
                retval = PAM_BUF_ERR;
                goto cleanup;
        }

        krb5_data_zero(&result_code_string);
        krb5_data_zero(&result_string);

        krbret = krb5_set_password(pam_context, &creds, passdup, princ,
            &result_code, &result_code_string, &result_string);
        free(passdup);
        if (krbret != 0) {
                log_krb5(pam_context, krbret, NULL, "Unable to set password");
                retval = PAM_AUTHTOK_ERR;
                goto cleanup;
        }
        if (result_code) {
                pam_info(pamh, "%s%s%.*s",
                    krb5_passwd_result_to_string(pam_context, result_code),
                    result_string.length > 0 ? ": " : "",
                    (int)result_string.length,
                    result_string.length > 0 ? (char *)result_string.data : "");
                retval = PAM_AUTHTOK_ERR;
        } else {
                PAM_LOG("Password changed");
        }

        krb5_data_free(&result_string);
        krb5_data_free(&result_code_string);

cleanup:
        krb5_free_cred_contents(pam_context, &creds);
        PAM_LOG("Done cleanup");
cleanup2:
        krb5_free_principal(pam_context, princ);
        PAM_LOG("Done cleanup2");
cleanup3:
        if (princ_name)
                free(princ_name);

        if (opts)
                krb5_get_init_creds_opt_free(pam_context, opts);

        krb5_free_context(pam_context);

        PAM_LOG("Done cleanup3");

        return (retval);
}

PAM_MODULE_ENTRY("pam_krb5");

static void
log_krb5(krb5_context ctx, krb5_error_code err,
    struct syslog_data *data, const char *fmt, ...)
{
        char b1[1024], b2[1024];
        const char *errtxt;
        va_list ap;
 
        va_start(ap, fmt);
        vsnprintf(b1, sizeof(b1), fmt, ap);
        va_end(ap);
        if (ctx)
                errtxt = krb5_get_error_message(ctx, err);
        else
                errtxt = NULL;
        if (errtxt != NULL) {
                snprintf(b2, sizeof(b2), "%s", errtxt);
                krb5_free_error_message(ctx, errtxt);
        } else {
                snprintf(b2, sizeof(b2), "unknown %d", (int)err);
        }
        if (data)
                syslog_r(LOG_DEBUG, data, "%s (%s)", b1, b2);
        else
                PAM_LOG("%s (%s)", b1, b2);
}

/*
 * This routine with some modification is from the MIT V5B6 appl/bsd/login.c
 * Modified by Sam Hartman <hartmans@mit.edu> to support PAM services
 * for Debian.
 *
 * Verify the Kerberos ticket-granting ticket just retrieved for the
 * user.  If the Kerberos server doesn't respond, assume the user is
 * trying to fake us out (since we DID just get a TGT from what is
 * supposedly our KDC).  If the host/<host> service is unknown (i.e.,
 * the local keytab doesn't have it), and we cannot find another
 * service we do have, let her in.
 *
 * - verify_krb_v5_tgt_begin returns a krb5 error code.
 * - verify_krb_v5_tgt returns 0 on success, -1 on failure.
 */
/* ARGSUSED */
static int
verify_krb_v5_tgt_begin(krb5_context context, char *pam_service, int debug,
    const char **servicep, krb5_principal *princp, char phost[static BUFSIZ],
    struct syslog_data *datap)
{
        krb5_error_code retval;
        krb5_principal princ;
        krb5_keyblock *keyblock;
        const char *services[3], **service;

        *servicep = NULL;
        *princp = NULL;

        if (debug)
                openlog_r("pam_krb5", LOG_PID, LOG_AUTHPRIV, datap);

        /* If possible we want to try and verify the ticket we have
         * received against a keytab.  We will try multiple service
         * principals, including at least the host principal and the PAM
         * service principal.  The host principal is preferred because access
         * to that key is generally sufficient to compromise root, while the
         * service key for this PAM service may be less carefully guarded.
         * It is important to check the keytab first before the KDC so we do
         * not get spoofed by a fake KDC.
         */
        services[0] = "host";
        services[1] = pam_service;
        services[2] = NULL;
        keyblock = 0;
        retval = -1;
        for (service = &services[0]; *service != NULL; service++) {
                retval = krb5_sname_to_principal(context, NULL, *service,
                    KRB5_NT_SRV_HST, &princ);
                if (retval != 0 && debug)
                        log_krb5(context, retval, datap,
                            "pam_krb5: verify_krb_v5_tgt: "
                            "krb5_sname_to_principal");
                if (retval != 0)
                        return (retval);

                /* Extract the name directly. */
                strlcpy(phost, compat_princ_component(context, princ, 1),
                    BUFSIZ);

                /*
                 * Do we have service/<host> keys?
                 * (use default/configured keytab, kvno IGNORE_VNO to get the
                 * first match, and ignore enctype.)
                 */
                retval = krb5_kt_read_service_key(context, NULL, princ, 0, 0,
                    &keyblock);
                if (retval != 0)
                        continue;
                *servicep = *service;
                *princp = princ;
                break;
        }
        if (keyblock)
                krb5_free_keyblock(context, keyblock);

        return (retval);
}

static int
verify_krb_v5_tgt(krb5_context context, krb5_ccache ccache,
    char *pam_service, int debug,
    const char *service, krb5_principal princ, char phost[static BUFSIZ],
    struct syslog_data *datap)
{
        krb5_error_code retval;
        krb5_auth_context auth_context = NULL;
        krb5_data packet;

        if (service == NULL)
                return (0);     /* uncertain, can't authenticate KDC */

        packet.data = 0;

        /* Talk to the kdc and construct the ticket. */
        auth_context = NULL;
        retval = krb5_mk_req(context, &auth_context, 0, service, phost,
                NULL, ccache, &packet);
        if (auth_context) {
                krb5_auth_con_free(context, auth_context);
                auth_context = NULL;    /* setup for rd_req */
        }
        if (retval) {
                if (debug)
                        log_krb5(context, retval, datap,
                            "pam_krb5: verify_krb_v5_tgt: "
                            "krb5_mk_req");
                retval = -1;
                goto cleanup;
        }

        /* Try to use the ticket. */
        retval = krb5_rd_req(context, &auth_context, &packet, princ, NULL,
            NULL, NULL);
        if (retval) {
                if (debug)
                        log_krb5(context, retval, datap,
                            "pam_krb5: verify_krb_v5_tgt: "
                            "krb5_rd_req");
                retval = -1;
        }
        else
                retval = 1;

cleanup:
        if (packet.data)
                compat_free_data_contents(context, &packet);
        if (auth_context) {
                krb5_auth_con_free(context, auth_context);
                auth_context = NULL;    /* setup for rd_req */
        }
        return (retval);
}

static void
verify_krb_v5_tgt_cleanup(krb5_context context, int debug,
    const char *service, krb5_principal princ, char phost[static BUFSIZ],
    struct syslog_data *datap)
{

        if (service)
                krb5_free_principal(context, princ);
        if (debug)
                closelog_r(datap);
}

/* Free the memory for cache_name. Called by pam_end() */
/* ARGSUSED */
static void
cleanup_cache(pam_handle_t *pamh __unused, void *data, int pam_end_status __unused)
{
        krb5_context pam_context;
        krb5_ccache ccache;
        krb5_error_code krbret;

        if (krb5_init_context(&pam_context))
                return;

        krbret = krb5_cc_resolve(pam_context, data, &ccache);
        if (krbret == 0)
                krb5_cc_destroy(pam_context, ccache);
        krb5_free_context(pam_context);
        free(data);
}

#ifdef COMPAT_HEIMDAL
#ifdef COMPAT_MIT
#error This cannot be MIT and Heimdal compatible!
#endif
#endif

#ifndef COMPAT_HEIMDAL
#ifndef COMPAT_MIT
#error One of COMPAT_MIT and COMPAT_HEIMDAL must be specified!
#endif
#endif

#ifdef COMPAT_HEIMDAL
/* ARGSUSED */
static const char *
compat_princ_component(krb5_context context __unused, krb5_principal princ, int n)
{
        return princ->name.name_string.val[n];
}

/* ARGSUSED */
static void
compat_free_data_contents(krb5_context context __unused, krb5_data * data)
{
        krb5_xfree(data->data);
}
#endif

#ifdef COMPAT_MIT
static const char *
compat_princ_component(krb5_context context, krb5_principal princ, int n)
{
        return krb5_princ_component(context, princ, n)->data;
}

static void
compat_free_data_contents(krb5_context context, krb5_data * data)
{
        krb5_free_data_contents(context, data);
}
#endif