pam_modules/krb5/krb5_authenticate.c

	krb5_authenticate.c revision 2278144afd2005b3eabcfd9bc412fe5ceb78749d
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_impl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#include <syslog.h>
#include <libintl.h>
#include <k5-int.h>
#include "profile/prof_int.h"
#include <netdb.h>
#include <ctype.h>
#include "utils.h"
#include "krb5_repository.h"

#define KRB5_DEFAULT_OPTIONS 0

int forwardable_flag = 0;
int renewable_flag = 0;
int proxiable_flag = 0;
int no_address_flag = 0;
profile_options_boolean config_option[] = {
    { "forwardable", &forwardable_flag, 0 },
    { "renewable",  &renewable_flag, 0 },
    { "proxiable", &proxiable_flag, 0 },
    { "no_addresses", &no_address_flag, 0 },
    { NULL, NULL, 0 }
};
char *renew_timeval;
char *life_timeval;
profile_option_strings config_times[] = {
    { "max_life", &life_timeval, 0 },
    { "max_renewable_life",  &renew_timeval, 0 },
    { NULL, NULL, 0 }
};
char *realmdef[] = { "realms", NULL, NULL, NULL };
char *appdef[] = { "appdefaults", "kinit", NULL };

#define krb_realm (*(realmdef + 1))

int attempt_krb5_auth(krb5_module_data_t *, char *, char **, boolean_t);
void    krb5_cleanup(pam_handle_t *, void *, int);

extern errcode_t profile_get_options_boolean();
extern errcode_t profile_get_options_string();
extern int krb5_verifypw(char *, char *, int);
extern krb5_error_code krb5_verify_init_creds(krb5_context,
        krb5_creds *, krb5_principal, krb5_keytab, krb5_ccache *,
        krb5_verify_init_creds_opt *);

/*
 * pam_sm_authenticate      - Authenticate user
 */
int
pam_sm_authenticate(
    pam_handle_t        *pamh,
    int             flags,
    int         argc,
    const char      **argv)
{
    char            *user = NULL;
    int         err;
    int         result = PAM_AUTH_ERR;
    /* pam.conf options */
    int         debug = 0;
    int         warn = 1;
    /* return an error on password expire */
    int         err_on_exp = 0;
    int         i;
    char            *password = NULL;
    uid_t           pw_uid;
    krb5_module_data_t  *kmd = NULL;
    krb5_repository_data_t  *krb5_data = NULL;
    pam_repository_t    *rep_data = NULL;

    for (i = 0; i < argc; i++) {
        if (strcmp(argv[i], "debug") == 0) {
            debug = 1;
        } else if (strcmp(argv[i], "nowarn") == 0) {
            warn = 0;
        } else if (strcmp(argv[i], "err_on_exp") == 0) {
            err_on_exp = 1;
        } else {
            syslog(LOG_ERR, dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth) unrecognized option %s"),
                argv[i]);
        }
    }
    if (flags & PAM_SILENT) warn = 0;

    if (debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): pam_sm_authenticate flags=%d",
            flags);

    (void) pam_get_item(pamh, PAM_USER, (void**) &user);

    if (user == NULL || *user == '\0') {
        if (debug)
            syslog(LOG_DEBUG, "PAM-KRB5 (auth): user empty "
                "or null");
        return (PAM_USER_UNKNOWN);
    }

    /* make sure a password entry exists for this user */
    if (!get_pw_uid(user, &pw_uid))
        return (PAM_USER_UNKNOWN);

    /*
     * pam_get_data could fail if we are being called for the first time
     * or if the module is not found, PAM_NO_MODULE_DATA is not an error
     */
    err = pam_get_data(pamh, KRB5_DATA, (const void**)&kmd);
    if (!(err == PAM_SUCCESS || err == PAM_NO_MODULE_DATA))
        return (PAM_AUTH_ERR);

    if (kmd == NULL) {
        kmd = calloc(1, sizeof (krb5_module_data_t));
        if (kmd == NULL) {
            result = PAM_BUF_ERR;
            goto out;
        }

        err = pam_set_data(pamh, KRB5_DATA, kmd, &krb5_cleanup);
        if (err != PAM_SUCCESS) {
            free(kmd);
            result = err;
            goto out;
        }
    }

    if (!kmd->env) {
        char buffer[512];

        if (snprintf(buffer, sizeof (buffer),
                "%s=FILE:/tmp/krb5cc_%d",
                KRB5_ENV_CCNAME, (int)pw_uid) >= sizeof (buffer)) {
            result = PAM_SYSTEM_ERR;
            goto out;
        }

        /* we MUST copy this to the heap for the putenv to work! */
        kmd->env = strdup(buffer);
        if (!kmd->env) {
            result = PAM_BUF_ERR;
            goto out;
        } else {
            if (putenv(kmd->env)) {
                result = PAM_SYSTEM_ERR;
                goto out;
            }
        }
    }

    kmd->auth_status = PAM_AUTH_ERR;
    kmd->debug = debug;
    kmd->warn = warn;
    kmd->err_on_exp = err_on_exp;
    kmd->ccache = NULL;
    kmd->kcontext = NULL;
    kmd->password = NULL;
    kmd->age_status = PAM_SUCCESS;
    (void) memset((char *)&kmd->initcreds, 0, sizeof (krb5_creds));

    /*
     * For apps that already did krb5 auth exchange...
     * Now that we've created the kmd structure, we can
     * return SUCCESS.  'kmd' may be needed later by other
     * PAM functions, thats why we wait until this point to
     * return.
     */
    (void) pam_get_item(pamh, PAM_REPOSITORY, (void **)&rep_data);

    if (rep_data != NULL) {
        if (strcmp(rep_data->type, KRB5_REPOSITORY_NAME) != 0) {
            if (debug)
                syslog(LOG_DEBUG, "PAM-KRB5 (auth): wrong"
                    "repository found (%s), returning "
                    "PAM_IGNORE", rep_data->type);
            return (PAM_IGNORE);
        }
        if (rep_data->scope_len == sizeof (krb5_repository_data_t)) {
            krb5_data = (krb5_repository_data_t *)rep_data->scope;

            if (krb5_data->flags ==
                SUNW_PAM_KRB5_ALREADY_AUTHENTICATED &&
                krb5_data->principal != NULL &&
                strlen(krb5_data->principal)) {
                if (debug)
                    syslog(LOG_DEBUG,
                        "PAM-KRB5 (auth): Principal "
                        "%s already authenticated",
                        krb5_data->principal);
                kmd->auth_status = PAM_SUCCESS;
                return (PAM_SUCCESS);
            }
        }
    }

    /*
     * if root key exists in the keytab, it's a random key so no
     * need to prompt for pw and we just return IGNORE.
     *
     * note we don't need to force a prompt for pw as authtok_get
     * is required to be stacked above this module.
     */
    if ((strcmp(user, ROOT_UNAME) == 0) &&
        key_in_keytab(user, debug)) {
        if (debug)
            syslog(LOG_DEBUG,
                "PAM-KRB5 (auth): "
                "key for '%s' in keytab, returning IGNORE", user);
        result = PAM_IGNORE;
        goto out;
    }

    (void) pam_get_item(pamh, PAM_AUTHTOK, (void **)&password);

    result = attempt_krb5_auth(kmd, user, &password, 1);

out:
    if (kmd) {
        if (debug)
            syslog(LOG_DEBUG,
                "PAM-KRB5 (auth): pam_sm_auth finalize"
                " ccname env, result =%d, env ='%s',"
                " age = %d, status = %d",
                result, kmd->env ? kmd->env : "<null>",
                kmd->age_status, kmd->auth_status);

        if (kmd->env &&
            !(kmd->age_status == PAM_NEW_AUTHTOK_REQD &&
                kmd->auth_status == PAM_SUCCESS)) {


            if (result == PAM_SUCCESS) {
                /*
                 * Put ccname into the pamh so that login
                 * apps can pick this up when they run
                 * pam_getenvlist().
                 */
                if ((result = pam_putenv(pamh, kmd->env))
                    != PAM_SUCCESS) {
                    /* should not happen but... */
                    syslog(LOG_ERR,
                        dgettext(TEXT_DOMAIN,
                        "PAM-KRB5 (auth):"
                        " pam_putenv failed: result: %d"),
                        result);
                    goto cleanupccname;
                }
            } else {
            cleanupccname:
                /* for lack of a Solaris unputenv() */
                krb5_unsetenv(KRB5_ENV_CCNAME);
                free(kmd->env);
                kmd->env = NULL;
            }
        }
        kmd->auth_status = result;
    }

    if (debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): end: %s", pam_strerror(pamh, result));

    return (result);
}

int
attempt_krb5_auth(
    krb5_module_data_t  *kmd,
    char        *user,
    char        **krb5_pass,
    boolean_t   verify_tik)
{
    krb5_principal  me = NULL;
    krb5_principal  server = NULL;
    krb5_creds  *my_creds;
    krb5_timestamp  now;
    krb5_error_code code = 0;
    char        kuser[2*MAXHOSTNAMELEN];
    krb5_deltat lifetime;
    krb5_deltat rlife;
    krb5_deltat krb5_max_duration;
    int     options = KRB5_DEFAULT_OPTIONS;
    krb5_data tgtname = {
        0,
        KRB5_TGS_NAME_SIZE,
        KRB5_TGS_NAME
    };
    krb5_get_init_creds_opt opts;
    /*
     * "result" should not be assigned PAM_SUCCESS unless
     * authentication has succeeded and there are no other errors.
     *
     * "code" is sometimes used for PAM codes, sometimes for krb5
     * codes.  Be careful.
     */
    int result = PAM_AUTH_ERR;

    if (kmd->debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): attempt_krb5_auth: start: user='%s'",
            user ? user : "<null>");

    krb5_get_init_creds_opt_init(&opts);

    /* need to free context with krb5_free_context */
    if (code = krb5_init_context(&kmd->kcontext)) {
        syslog(LOG_ERR, dgettext(TEXT_DOMAIN,
            "PAM-KRB5 (auth): Error initializing "
            "krb5: %s"),
            error_message(code));
        return (PAM_SYSTEM_ERR);
    }

    if ((code = get_kmd_kuser(kmd->kcontext, (const char *)user, kuser,
        2*MAXHOSTNAMELEN)) != 0) {
        /* get_kmd_kuser returns proper PAM error statuses */
        return (code);
    }

    if ((code = krb5_parse_name(kmd->kcontext, kuser, &me)) != 0) {
        krb5_free_context(kmd->kcontext);
        kmd->kcontext = NULL;
        return (PAM_AUTH_ERR);
    }

    /* call krb5_free_cred_contents() on error */
    my_creds = &kmd->initcreds;

    if ((code = krb5_copy_principal(kmd->kcontext, me, &my_creds->client)))
            goto out_err;

    if (code = krb5_build_principal_ext(kmd->kcontext, &server,
                krb5_princ_realm(kmd->kcontext, me)->length,
                krb5_princ_realm(kmd->kcontext, me)->data,
                tgtname.length, tgtname.data,
                krb5_princ_realm(kmd->kcontext, me)->length,
                krb5_princ_realm(kmd->kcontext, me)->data, 0)) {
        syslog(LOG_ERR, dgettext(TEXT_DOMAIN,
                    "PAM-KRB5 (auth): attempt_krb5_auth: "
                    "krb5_build_princ_ext failed: %s"),
            error_message(code));
        goto out;
    }

    if (code = krb5_copy_principal(kmd->kcontext, server,
                &my_creds->server)) {
        goto out_err;
    }

    if (code = krb5_timeofday(kmd->kcontext, &now)) {
        syslog(LOG_ERR, dgettext(TEXT_DOMAIN,
                    "PAM-KRB5 (auth): attempt_krb5_auth: "
                    "krb5_timeofday failed: %s"),
            error_message(code));
        goto out;
    }

    /*
     * set the values for lifetime and rlife to be the maximum
     * possible
     */
    krb5_max_duration = KRB5_KDB_EXPIRATION - now - 60*60;
    lifetime = krb5_max_duration;
    rlife = krb5_max_duration;

    /*
     * Let us get the values for various options
     * from Kerberos configuration file
     */

    krb_realm = krb5_princ_realm(kmd->kcontext, me)->data;
    profile_get_options_boolean(kmd->kcontext->profile,
                    realmdef, config_option);
    profile_get_options_boolean(kmd->kcontext->profile,
                    appdef, config_option);
    profile_get_options_string(kmd->kcontext->profile,
                realmdef, config_times);
    profile_get_options_string(kmd->kcontext->profile,
                appdef, config_times);

    if (renew_timeval) {
        code = krb5_string_to_deltat(renew_timeval, &rlife);
        if (code != 0 || rlife == 0 || rlife > krb5_max_duration) {
            syslog(LOG_ERR,
                dgettext(TEXT_DOMAIN,
                    "PAM-KRB5 (auth): Bad max_renewable_life "
                    " value '%s' in Kerberos config file"),
                renew_timeval);
            result = PAM_SYSTEM_ERR;
            goto out;
        }
    }
    if (life_timeval) {
        code = krb5_string_to_deltat(life_timeval, &lifetime);
        if (code != 0 || lifetime == 0 ||
            lifetime > krb5_max_duration) {
            syslog(LOG_ERR,
                dgettext(TEXT_DOMAIN, "PAM-KRB5 (auth): Bad "
                "lifetime value '%s' in Kerberos config file"),
                life_timeval);
            result = PAM_SYSTEM_ERR;
            goto out;
        }
    }
    /*  start timer when request gets to KDC */
    my_creds->times.starttime = 0;
    my_creds->times.endtime = now + lifetime;

    if (options & KDC_OPT_RENEWABLE) {
        my_creds->times.renew_till = now + rlife;
    } else
        my_creds->times.renew_till = 0;

    krb5_get_init_creds_opt_set_tkt_life(&opts, lifetime);

    if (proxiable_flag) {       /* Set in config file */
        if (kmd->debug)
            syslog(LOG_DEBUG, dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth): Proxiable tickets "
                "requested"));
        krb5_get_init_creds_opt_set_proxiable(&opts, TRUE);
    }
    if (forwardable_flag) {
        if (kmd->debug)
            syslog(LOG_DEBUG, dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth): Forwardable tickets "
                "requested"));
        krb5_get_init_creds_opt_set_forwardable(&opts, TRUE);
    }
    if (renewable_flag) {
        if (kmd->debug)
            syslog(LOG_DEBUG, dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth): Renewable tickets "
                "requested"));
        krb5_get_init_creds_opt_set_renew_life(&opts, rlife);
    }
    if (no_address_flag) {
        if (kmd->debug)
            syslog(LOG_DEBUG, dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth): Addressless tickets "
                "requested"));
        krb5_get_init_creds_opt_set_address_list(&opts, NULL);
    }

    /*
     * mech_krb5 interprets empty passwords as NULL passwords
     * and tries to read a password from stdin. Since we are in
     * pam this is bad and should not be allowed.
     */
    if (*krb5_pass == NULL || strlen(*krb5_pass) == 0) {
        code = KRB5KRB_AP_ERR_BAD_INTEGRITY;
    } else {
        code = krb5_get_init_creds_password(kmd->kcontext,
                my_creds,
                me,
                *krb5_pass, /* clear text passwd */
                NULL,       /* prompter */
                NULL,       /* data */
                0,      /* start time */
                NULL,       /* defaults to krbtgt@REALM */
                &opts);
    }

    if (kmd->debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): attempt_krb5_auth: "
            "krb5_get_init_creds_password returns: %s",
            code == 0 ? "SUCCESS" : error_message(code));

    switch (code) {
    case 0:
        /* got a tgt, let's verify it */
        if (verify_tik) {
            krb5_verify_init_creds_opt vopts;

            krb5_principal sp = NULL;
            char kt_name[MAX_KEYTAB_NAME_LEN];
            char *fqdn;

            krb5_verify_init_creds_opt_init(&vopts);

            code = krb5_verify_init_creds(kmd->kcontext,
                my_creds,
                NULL,   /* defaults to host/localhost@REALM */
                NULL,
                NULL,
                &vopts);

            if (code) {
                result = PAM_SYSTEM_ERR;

                /*
                 * Give a better error message when the
                 * keytable entry isn't found or the keytab
                 * file cannot be found.
                 */
                if (krb5_sname_to_principal(kmd->kcontext, NULL,
                        NULL, KRB5_NT_SRV_HST, &sp))
                    fqdn = "<fqdn>";
                else
                    fqdn = sp->data[1].data;

                if (krb5_kt_default_name(kmd->kcontext, kt_name,
                            sizeof (kt_name)))
                    (void) strncpy(kt_name,
                        "default keytab",
                        sizeof (kt_name));

                switch (code) {
                case KRB5_KT_NOTFOUND:
                    syslog(LOG_ERR,
                    dgettext(TEXT_DOMAIN,
                        "PAM-KRB5 (auth): "
                        "krb5_verify_init_creds failed:"
                        " Key table entry \"host/%s\""
                        " not found in %s"),
                        fqdn, kt_name);
                    break;
                case ENOENT:
                    syslog(LOG_ERR,
                    dgettext(TEXT_DOMAIN,
                        "PAM-KRB5 (auth): "
                        "krb5_verify_init_creds failed:"
                        " Keytab file \"%s\""
                        " does not exist.\n"),
                        kt_name);
                    break;
                default:
                    syslog(LOG_ERR,
                    dgettext(TEXT_DOMAIN,
                        "PAM-KRB5 (auth): "
                        "krb5_verify_init_creds failed:"
                        " %s"),
                        error_message(code));
                    break;
                }

                if (sp)
                    krb5_free_principal(kmd->kcontext, sp);
            }
        }
        break;

    case KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN:
        /*
         * Since this principal is not part of the local
         * Kerberos realm, we just return PAM_USER_UNKNOWN.
         */
        result = PAM_USER_UNKNOWN;

        if (kmd->debug)
            syslog(LOG_DEBUG, "PAM-KRB5 (auth): attempt_krb5_auth:"
                " User is not part of the local Kerberos"
                " realm: %s", error_message(code));
        break;

    case KRB5KDC_ERR_PREAUTH_FAILED:
    case KRB5KRB_AP_ERR_BAD_INTEGRITY:
        /*
         * We could be trying the password from a previous
         * pam authentication module, but we don't want to
         * generate an error if the unix password is different
         * than the Kerberos password...
         */
        break;

    case KRB5KDC_ERR_KEY_EXP:
        if (!kmd->err_on_exp) {
            /*
             * Request a tik for changepw service
             * and it will tell us if pw is good or not.
             */
            code = krb5_verifypw(kuser, *krb5_pass, kmd->debug);

            if (kmd->debug)
                syslog(LOG_DEBUG,
                    "PAM-KRB5 (auth): attempt_krb5_auth: "
                    "verifypw %d", code);

            if (code == 0) {
                /* pw is good, set age status for acct_mgmt */
                kmd->age_status = PAM_NEW_AUTHTOK_REQD;
            }
        }
        break;

    default:
        result = PAM_SYSTEM_ERR;
        if (kmd->debug)
            syslog(LOG_DEBUG, "PAM-KRB5 (auth): error %d - %s",
                code, error_message(code));
        break;
    }

    if (code == 0) {
        /*
         * success for the entered pw
         *
         * we can't rely on the pw in PAM_AUTHTOK
         * to be the (correct) krb5 one so
         * store krb5 pw in module data for
         * use in acct_mgmt
         */
        if (!(kmd->password = strdup(*krb5_pass))) {
            syslog(LOG_ERR, "Cannot strdup password");
            result = PAM_BUF_ERR;
            goto out_err;
        }
        result = PAM_SUCCESS;
        goto out;
    }

out_err:
    /* jump (or reach) here if error and cred cache has been init */

    if (kmd->debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): clearing initcreds in "
            "pam_authenticate()");

    krb5_free_cred_contents(kmd->kcontext, &kmd->initcreds);
    (void) memset((char *)&kmd->initcreds, 0, sizeof (krb5_creds));

out:
    if (server)
        krb5_free_principal(kmd->kcontext, server);
    if (me)
        krb5_free_principal(kmd->kcontext, me);
    if (kmd->kcontext) {
        krb5_free_context(kmd->kcontext);
        kmd->kcontext = NULL;
    }

    if (kmd->debug)
        syslog(LOG_DEBUG,
            "PAM-KRB5 (auth): attempt_krb5_auth returning %d",
            result);

    return (kmd->auth_status = result);
}

/*ARGSUSED*/
void
krb5_cleanup(pam_handle_t *pamh, void *data, int pam_status)
{
    krb5_module_data_t *kmd = (krb5_module_data_t *)data;

    if (kmd == NULL)
        return;

    if (kmd->debug) {
        syslog(LOG_DEBUG,
            dgettext(TEXT_DOMAIN,
                "PAM-KRB5 (auth): krb5_cleanup auth_status = %d"),
            kmd->auth_status);
    }

    /*
     * if pam_status is PAM_SUCCESS, clean up based on value in
     * auth_status, otherwise just purge the context
     */
    if ((pam_status == PAM_SUCCESS) &&
        (kmd->auth_status == PAM_SUCCESS) && kmd->ccache)
        krb5_cc_close(kmd->kcontext, kmd->ccache);

    if (kmd->password) {
        (void) memset(kmd->password, 0, strlen(kmd->password));
        free(kmd->password);
    }

    if ((pam_status != PAM_SUCCESS) ||
        (kmd->auth_status != PAM_SUCCESS)) {
        krb5_free_cred_contents(kmd->kcontext, &kmd->initcreds);
        (void) memset((char *)&kmd->initcreds, 0, sizeof (krb5_creds));
    }

    free(kmd);
}