samba-mirror/source3/libads/kerberos_keytab.c

/*
   Unix SMB/CIFS implementation.
   kerberos keytab utility library
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Remus Koos 2001
   Copyright (C) Luke Howard 2003
   Copyright (C) Jim McDonough (jmcd@us.ibm.com) 2003
   Copyright (C) Guenther Deschner 2003
   Copyright (C) Rakesh Patel 2004
   Copyright (C) Dan Perry 2004
   Copyright (C) Jeremy Allison 2004
   Copyright (C) Gerald Carter 2006

   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 "includes.h"
#include "smb_krb5.h"
#include "ads.h"
#include "secrets.h"

#ifdef HAVE_KRB5

#ifdef HAVE_ADS

/* This MAX_NAME_LEN is a constant defined in krb5.h */
#ifndef MAX_KEYTAB_NAME_LEN
#define MAX_KEYTAB_NAME_LEN 1100
#endif

static krb5_error_code ads_keytab_open(krb5_context context,
				       krb5_keytab *keytab)
{
	char keytab_str[MAX_KEYTAB_NAME_LEN] = {0};
	const char *keytab_name = NULL;
	krb5_error_code ret = 0;

	switch (lp_kerberos_method()) {
	case KERBEROS_VERIFY_SYSTEM_KEYTAB:
	case KERBEROS_VERIFY_SECRETS_AND_KEYTAB:
		ret = krb5_kt_default_name(context,
					   keytab_str,
					   sizeof(keytab_str) - 2);
		if (ret != 0) {
			DBG_WARNING("Failed to get default keytab name");
			goto out;
		}
		keytab_name = keytab_str;
		break;
	case KERBEROS_VERIFY_DEDICATED_KEYTAB:
		keytab_name = lp_dedicated_keytab_file();
		break;
	default:
		DBG_ERR("Invalid kerberos method set (%d)\n",
			lp_kerberos_method());
		ret = KRB5_KT_BADNAME;
		goto out;
	}

	if (keytab_name == NULL || keytab_name[0] == '\0') {
		DBG_ERR("Invalid keytab name\n");
		ret = KRB5_KT_BADNAME;
		goto out;
	}

	ret = smb_krb5_kt_open(context, keytab_name, true, keytab);
	if (ret != 0) {
		DBG_WARNING("smb_krb5_kt_open failed (%s)\n",
			    error_message(ret));
		goto out;
	}

out:
	return ret;
}

/**********************************************************************
 Adds a single service principal, i.e. 'host' to the system keytab
***********************************************************************/

int ads_keytab_add_entry(ADS_STRUCT *ads, const char *srvPrinc)
{
	krb5_error_code ret = 0;
	krb5_context context = NULL;
	krb5_keytab keytab = NULL;
	krb5_data password;
	krb5_kvno kvno;
        krb5_enctype enctypes[6] = {
		ENCTYPE_DES_CBC_CRC,
		ENCTYPE_DES_CBC_MD5,
#ifdef HAVE_ENCTYPE_AES128_CTS_HMAC_SHA1_96
		ENCTYPE_AES128_CTS_HMAC_SHA1_96,
#endif
#ifdef HAVE_ENCTYPE_AES256_CTS_HMAC_SHA1_96
		ENCTYPE_AES256_CTS_HMAC_SHA1_96,
#endif
		ENCTYPE_ARCFOUR_HMAC,
		0
	};
	char *princ_s = NULL;
	char *short_princ_s = NULL;
	char *salt_princ_s = NULL;
	char *password_s = NULL;
	char *my_fqdn;
	TALLOC_CTX *tmpctx = NULL;
	char *machine_name;
	ADS_STATUS aderr;
	int i;

	initialize_krb5_error_table();
	ret = krb5_init_context(&context);
	if (ret) {
		DEBUG(1, (__location__ ": could not krb5_init_context: %s\n",
			  error_message(ret)));
		return -1;
	}

	ret = ads_keytab_open(context, &keytab);
	if (ret != 0) {
		goto out;
	}

	/* retrieve the password */
	if (!secrets_init()) {
		DEBUG(1, (__location__ ": secrets_init failed\n"));
		ret = -1;
		goto out;
	}
	password_s = secrets_fetch_machine_password(lp_workgroup(), NULL, NULL);
	if (!password_s) {
		DEBUG(1, (__location__ ": failed to fetch machine password\n"));
		ret = -1;
		goto out;
	}
	ZERO_STRUCT(password);
	password.data = password_s;
	password.length = strlen(password_s);

	/* we need the dNSHostName value here */
	tmpctx = talloc_init(__location__);
	if (!tmpctx) {
		DEBUG(0, (__location__ ": talloc_init() failed!\n"));
		ret = -1;
		goto out;
	}

	my_fqdn = ads_get_dnshostname(ads, tmpctx, lp_netbios_name());
	if (!my_fqdn) {
		DEBUG(0, (__location__ ": unable to determine machine "
			  "account's dns name in AD!\n"));
		ret = -1;
		goto out;
	}

	machine_name = ads_get_samaccountname(ads, tmpctx, lp_netbios_name());
	if (!machine_name) {
		DEBUG(0, (__location__ ": unable to determine machine "
			  "account's short name in AD!\n"));
		ret = -1;
		goto out;
	}
	/*strip the trailing '$' */
	machine_name[strlen(machine_name)-1] = '\0';

	/* Construct our principal */
	if (strchr_m(srvPrinc, '@')) {
		/* It's a fully-named principal. */
		princ_s = talloc_asprintf(tmpctx, "%s", srvPrinc);
		if (!princ_s) {
			ret = -1;
			goto out;
		}
	} else if (srvPrinc[strlen(srvPrinc)-1] == '$') {
		/* It's the machine account, as used by smbclient clients. */
		princ_s = talloc_asprintf(tmpctx, "%s@%s",
					  srvPrinc, lp_realm());
		if (!princ_s) {
			ret = -1;
			goto out;
		}
	} else {
		/* It's a normal service principal.  Add the SPN now so that we
		 * can obtain credentials for it and double-check the salt value
		 * used to generate the service's keys. */

		princ_s = talloc_asprintf(tmpctx, "%s/%s@%s",
					  srvPrinc, my_fqdn, lp_realm());
		if (!princ_s) {
			ret = -1;
			goto out;
		}
		short_princ_s = talloc_asprintf(tmpctx, "%s/%s@%s",
						srvPrinc, machine_name,
						lp_realm());
		if (short_princ_s == NULL) {
			ret = -1;
			goto out;
		}

		/* According to http://support.microsoft.com/kb/326985/en-us,
		   certain principal names are automatically mapped to the
		   host/... principal in the AD account.
		   So only create these in the keytab, not in AD.  --jerry */

		if (!strequal(srvPrinc, "cifs") &&
		    !strequal(srvPrinc, "host")) {
			DEBUG(3, (__location__ ": Attempting to add/update "
				  "'%s'\n", princ_s));

			aderr = ads_add_service_principal_name(ads,
					lp_netbios_name(), my_fqdn, srvPrinc);
			if (!ADS_ERR_OK(aderr)) {
				DEBUG(1, (__location__ ": failed to "
					 "ads_add_service_principal_name.\n"));
				goto out;
			}
		}
	}

	kvno = (krb5_kvno)ads_get_machine_kvno(ads, lp_netbios_name());
	if (kvno == -1) {
		/* -1 indicates failure, everything else is OK */
		DEBUG(1, (__location__ ": ads_get_machine_kvno failed to "
			 "determine the system's kvno.\n"));
		ret = -1;
		goto out;
	}

	salt_princ_s = kerberos_secrets_fetch_salt_princ();
	if (salt_princ_s == NULL) {
		DBG_WARNING("kerberos_secrets_fetch_salt_princ() failed\n");
		ret = -1;
		goto out;
	}

	for (i = 0; enctypes[i]; i++) {

		/* add the fqdn principal to the keytab */
		ret = smb_krb5_kt_add_entry(context,
					    keytab,
					    kvno,
					    princ_s,
					    salt_princ_s,
					    enctypes[i],
					    &password,
					    false,
					    false);
		if (ret) {
			DEBUG(1, (__location__ ": Failed to add entry to keytab\n"));
			goto out;
		}

		/* add the short principal name if we have one */
		if (short_princ_s) {
			ret = smb_krb5_kt_add_entry(context,
						    keytab,
						    kvno,
						    short_princ_s,
						    salt_princ_s,
						    enctypes[i],
						    &password,
						    false,
						    false);
			if (ret) {
				DEBUG(1, (__location__
					  ": Failed to add short entry to keytab\n"));
				goto out;
			}
		}
	}

out:
	SAFE_FREE(salt_princ_s);
	TALLOC_FREE(tmpctx);

	if (keytab) {
		krb5_kt_close(context, keytab);
	}
	if (context) {
		krb5_free_context(context);
	}
	return (int)ret;
}

/**********************************************************************
 Flushes all entries from the system keytab.
***********************************************************************/

int ads_keytab_flush(ADS_STRUCT *ads)
{
	krb5_error_code ret = 0;
	krb5_context context = NULL;
	krb5_keytab keytab = NULL;
	krb5_kvno kvno;
	ADS_STATUS aderr;

	initialize_krb5_error_table();
	ret = krb5_init_context(&context);
	if (ret) {
		DEBUG(1, (__location__ ": could not krb5_init_context: %s\n",
			  error_message(ret)));
		return ret;
	}

	ret = ads_keytab_open(context, &keytab);
	if (ret != 0) {
		goto out;
	}

	kvno = (krb5_kvno)ads_get_machine_kvno(ads, lp_netbios_name());
	if (kvno == -1) {
		/* -1 indicates a failure */
		DEBUG(1, (__location__ ": Error determining the kvno.\n"));
		goto out;
	}

	/* Seek and delete old keytab entries */
	ret = smb_krb5_kt_seek_and_delete_old_entries(context,
						      keytab,
						      kvno,
						      ENCTYPE_NULL,
						      NULL,
						      NULL,
						      true,
						      false);
	if (ret) {
		goto out;
	}

	aderr = ads_clear_service_principal_names(ads, lp_netbios_name());
	if (!ADS_ERR_OK(aderr)) {
		DEBUG(1, (__location__ ": Error while clearing service "
			  "principal listings in LDAP.\n"));
		goto out;
	}

out:
	if (keytab) {
		krb5_kt_close(context, keytab);
	}
	if (context) {
		krb5_free_context(context);
	}
	return ret;
}

/**********************************************************************
 Adds all the required service principals to the system keytab.
***********************************************************************/

int ads_keytab_create_default(ADS_STRUCT *ads)
{
	krb5_error_code ret = 0;
	krb5_context context = NULL;
	krb5_keytab keytab = NULL;
	krb5_kt_cursor cursor = {0};
	krb5_keytab_entry kt_entry = {0};
	krb5_kvno kvno;
	size_t found = 0;
	char *sam_account_name, *upn;
	char **oldEntries = NULL, *princ_s[26];
	TALLOC_CTX *frame;
	char *machine_name;
	char **spn_array;
	size_t num_spns;
	size_t i;
	ADS_STATUS status;

	ZERO_STRUCT(kt_entry);
	ZERO_STRUCT(cursor);

	frame = talloc_stackframe();
	if (frame == NULL) {
		ret = -1;
		goto done;
	}

	status = ads_get_service_principal_names(frame,
						 ads,
						 lp_netbios_name(),
						 &spn_array,
						 &num_spns);
	if (!ADS_ERR_OK(status)) {
		ret = -1;
		goto done;
	}

	for (i = 0; i < num_spns; i++) {
		char *srv_princ;
		char *p;

		srv_princ = strlower_talloc(frame, spn_array[i]);
		if (srv_princ == NULL) {
			ret = -1;
			goto done;
		}

		p = strchr_m(srv_princ, '/');
		if (p == NULL) {
			continue;
		}
		p[0] = '\0';

		/* Add the SPNs found on the DC */
		ret = ads_keytab_add_entry(ads, srv_princ);
		if (ret != 0) {
			DEBUG(1, ("ads_keytab_add_entry failed while "
				  "adding '%s' principal.\n",
				  spn_array[i]));
			goto done;
		}
	}

#if 0	/* don't create the CIFS/... keytab entries since no one except smbd
	   really needs them and we will fall back to verifying against
	   secrets.tdb */

	ret = ads_keytab_add_entry(ads, "cifs"));
	if (ret != 0 ) {
		DEBUG(1, (__location__ ": ads_keytab_add_entry failed while "
			  "adding 'cifs'.\n"));
		return ret;
	}
#endif

	memset(princ_s, '\0', sizeof(princ_s));

	initialize_krb5_error_table();
	ret = krb5_init_context(&context);
	if (ret) {
		DEBUG(1, (__location__ ": could not krb5_init_context: %s\n",
			  error_message(ret)));
		goto done;
	}

	machine_name = talloc_strdup(frame, lp_netbios_name());
	if (!machine_name) {
		ret = -1;
		goto done;
	}

	/* now add the userPrincipalName and sAMAccountName entries */
	sam_account_name = ads_get_samaccountname(ads, frame, machine_name);
	if (!sam_account_name) {
		DEBUG(0, (__location__ ": unable to determine machine "
			  "account's name in AD!\n"));
		ret = -1;
		goto done;
	}

	/* upper case the sAMAccountName to make it easier for apps to
	   know what case to use in the keytab file */
	if (!strupper_m(sam_account_name)) {
		ret = -1;
		goto done;
	}

	ret = ads_keytab_add_entry(ads, sam_account_name);
	if (ret != 0) {
		DEBUG(1, (__location__ ": ads_keytab_add_entry() failed "
			  "while adding sAMAccountName (%s)\n",
			  sam_account_name));
		goto done;
	}

	/* remember that not every machine account will have a upn */
	upn = ads_get_upn(ads, frame, machine_name);
	if (upn) {
		ret = ads_keytab_add_entry(ads, upn);
		if (ret != 0) {
			DEBUG(1, (__location__ ": ads_keytab_add_entry() "
				  "failed while adding UPN (%s)\n", upn));
			goto done;
		}
	}

	/* Now loop through the keytab and update any other existing entries */
	kvno = (krb5_kvno)ads_get_machine_kvno(ads, machine_name);
	if (kvno == (krb5_kvno)-1) {
		DEBUG(1, (__location__ ": ads_get_machine_kvno() failed to "
			  "determine the system's kvno.\n"));
		goto done;
	}

	DEBUG(3, (__location__ ": Searching for keytab entries to preserve "
		  "and update.\n"));

	ret = ads_keytab_open(context, &keytab);
	if (ret != 0) {
		goto done;
	}

	ret = krb5_kt_start_seq_get(context, keytab, &cursor);
	if (ret != KRB5_KT_END && ret != ENOENT ) {
		while ((ret = krb5_kt_next_entry(context, keytab,
						 &kt_entry, &cursor)) == 0) {
			smb_krb5_kt_free_entry(context, &kt_entry);
			ZERO_STRUCT(kt_entry);
			found++;
		}
	}
	krb5_kt_end_seq_get(context, keytab, &cursor);
	ZERO_STRUCT(cursor);

	/*
	 * Hmmm. There is no "rewind" function for the keytab. This means we
	 * have a race condition where someone else could add entries after
	 * we've counted them. Re-open asap to minimise the race. JRA.
	 */
	DEBUG(3, (__location__ ": Found %zd entries in the keytab.\n", found));
	if (!found) {
		goto done;
	}

	oldEntries = talloc_zero_array(frame, char *, found + 1);
	if (!oldEntries) {
		DEBUG(1, (__location__ ": Failed to allocate space to store "
			  "the old keytab entries (talloc failed?).\n"));
		ret = -1;
		goto done;
	}

	ret = krb5_kt_start_seq_get(context, keytab, &cursor);
	if (ret == KRB5_KT_END || ret == ENOENT) {
		krb5_kt_end_seq_get(context, keytab, &cursor);
		ZERO_STRUCT(cursor);
		goto done;
	}

	while (krb5_kt_next_entry(context, keytab, &kt_entry, &cursor) == 0) {
		if (kt_entry.vno != kvno) {
			char *ktprinc = NULL;
			char *p;

			/* This returns a malloc'ed string in ktprinc. */
			ret = smb_krb5_unparse_name(oldEntries, context,
						    kt_entry.principal,
						    &ktprinc);
			if (ret) {
				DEBUG(1, (__location__
					 ": smb_krb5_unparse_name failed "
					 "(%s)\n", error_message(ret)));
				goto done;
			}
			/*
			 * From looking at the krb5 source they don't seem to
			 * take locale or mb strings into account.
			 * Maybe this is because they assume utf8 ?
			 * In this case we may need to convert from utf8 to
			 * mb charset here ? JRA.
			 */
			p = strchr_m(ktprinc, '@');
			if (p) {
				*p = '\0';
			}

			p = strchr_m(ktprinc, '/');
			if (p) {
				*p = '\0';
			}
			for (i = 0; i < found; i++) {
				if (!oldEntries[i]) {
					oldEntries[i] = ktprinc;
					break;
				}
				if (!strcmp(oldEntries[i], ktprinc)) {
					TALLOC_FREE(ktprinc);
					break;
				}
			}
			if (i == found) {
				TALLOC_FREE(ktprinc);
			}
		}
		smb_krb5_kt_free_entry(context, &kt_entry);
		ZERO_STRUCT(kt_entry);
	}
	krb5_kt_end_seq_get(context, keytab, &cursor);
	ZERO_STRUCT(cursor);

	ret = 0;
	for (i = 0; oldEntries[i]; i++) {
		ret |= ads_keytab_add_entry(ads, oldEntries[i]);
		TALLOC_FREE(oldEntries[i]);
	}

done:
	TALLOC_FREE(oldEntries);
	TALLOC_FREE(frame);

	if (context) {
		if (!all_zero((uint8_t *)&kt_entry, sizeof(kt_entry))) {
			smb_krb5_kt_free_entry(context, &kt_entry);
		}
		if (!all_zero((uint8_t *)&cursor, sizeof(cursor)) && keytab) {
			krb5_kt_end_seq_get(context, keytab, &cursor);
		}
		if (keytab) {
			krb5_kt_close(context, keytab);
		}
		krb5_free_context(context);
	}
	return ret;
}

#endif /* HAVE_ADS */

/**********************************************************************
 List system keytab.
***********************************************************************/

int ads_keytab_list(const char *keytab_name)
{
	krb5_error_code ret = 0;
	krb5_context context = NULL;
	krb5_keytab keytab = NULL;
	krb5_kt_cursor cursor;
	krb5_keytab_entry kt_entry;

	ZERO_STRUCT(kt_entry);
	ZERO_STRUCT(cursor);

	initialize_krb5_error_table();
	ret = krb5_init_context(&context);
	if (ret) {
		DEBUG(1, (__location__ ": could not krb5_init_context: %s\n",
			  error_message(ret)));
		return ret;
	}

	if (keytab_name == NULL) {
		ret = ads_keytab_open(context, &keytab);
	} else {
		ret = smb_krb5_kt_open(context, keytab_name, False, &keytab);
	}
	if (ret) {
		DEBUG(1, ("smb_krb5_kt_open failed (%s)\n",
			  error_message(ret)));
		goto out;
	}

	ret = krb5_kt_start_seq_get(context, keytab, &cursor);
	if (ret) {
		ZERO_STRUCT(cursor);
		goto out;
	}

	printf("Vno  Type                                        Principal\n");

	while (krb5_kt_next_entry(context, keytab, &kt_entry, &cursor) == 0) {

		char *princ_s = NULL;
		char *etype_s = NULL;
		krb5_enctype enctype = 0;

		ret = smb_krb5_unparse_name(talloc_tos(), context,
					    kt_entry.principal, &princ_s);
		if (ret) {
			goto out;
		}

		enctype = smb_krb5_kt_get_enctype_from_entry(&kt_entry);

		ret = smb_krb5_enctype_to_string(context, enctype, &etype_s);
		if (ret &&
		    (asprintf(&etype_s, "UNKNOWN: %d\n", enctype) == -1)) {
			TALLOC_FREE(princ_s);
			goto out;
		}

		printf("%3d  %-43s %s\n", kt_entry.vno, etype_s, princ_s);

		TALLOC_FREE(princ_s);
		SAFE_FREE(etype_s);

		ret = smb_krb5_kt_free_entry(context, &kt_entry);
		if (ret) {
			goto out;
		}
	}

	ret = krb5_kt_end_seq_get(context, keytab, &cursor);
	if (ret) {
		goto out;
	}

	/* Ensure we don't double free. */
	ZERO_STRUCT(kt_entry);
	ZERO_STRUCT(cursor);
out:

	if (!all_zero((uint8_t *)&kt_entry, sizeof(kt_entry))) {
		smb_krb5_kt_free_entry(context, &kt_entry);
	}
	if (!all_zero((uint8_t *)&cursor, sizeof(cursor)) && keytab) {
		krb5_kt_end_seq_get(context, keytab, &cursor);
	}

	if (keytab) {
		krb5_kt_close(context, keytab);
	}
	if (context) {
		krb5_free_context(context);
	}
	return ret;
}

#endif /* HAVE_KRB5 */