pam_modules/krb5/krb5_authenticate.c

/*
 * 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(void *, 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(pam_handle_t *, char *, char *, boolean_t, 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);

	/* Prompt for user name if it is not already available */
	if (user == NULL || !user[0]) {
		if (debug)
			syslog(LOG_DEBUG, "PAM-KRB5 (auth): user empty "
				"or null");
		if ((err = pam_get_user(pamh, &user, NULL)) != PAM_SUCCESS)
			return (err);

		if (user == NULL || !user[0])
			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(pamh, 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(
	void		*pamh,
	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(pamh, kuser, *krb5_pass,
					    0, kmd->debug);

			if (kmd->debug)
				syslog(LOG_DEBUG,
				    "PAM-KRB5 (auth): attempt_krb5_auth: "
				    "verifypw %s", error_message(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);
}