path: root/source4/kdc/wdc-samba4.c

/*
   Unix SMB/CIFS implementation.

   PAC Glue between Samba and the KDC

   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005-2009
   Copyright (C) Simo Sorce <idra@samba.org> 2010

   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 "kdc/kdc-glue.h"
#include "kdc/db-glue.h"
#include "kdc/pac-glue.h"
#include "sdb.h"
#include "sdb_hdb.h"
#include "librpc/gen_ndr/auth.h"

/*
 * Given the right private pointer from hdb_samba4,
 * get a PAC from the attached ldb messages.
 *
 * For PKINIT we also get pk_reply_key and can add PAC_CREDENTIAL_INFO.
 */
static krb5_error_code samba_wdc_get_pac(void *priv, krb5_context context,
					 struct hdb_entry_ex *client,
					 struct hdb_entry_ex *server,
					 const krb5_keyblock *pk_reply_key,
					 const krb5_boolean *pac_request,
					 krb5_pac *pac)
{
	TALLOC_CTX *mem_ctx;
	DATA_BLOB *logon_blob = NULL;
	DATA_BLOB *cred_ndr = NULL;
	DATA_BLOB **cred_ndr_ptr = NULL;
	DATA_BLOB _cred_blob = data_blob_null;
	DATA_BLOB *cred_blob = NULL;
	DATA_BLOB *upn_blob = NULL;
	DATA_BLOB *pac_attrs_blob = NULL;
	DATA_BLOB *requester_sid_blob = NULL;
	krb5_error_code ret;
	NTSTATUS nt_status;
	struct samba_kdc_entry *skdc_entry =
		talloc_get_type_abort(client->ctx,
		struct samba_kdc_entry);
	bool is_krbtgt;

	mem_ctx = talloc_named(client->ctx, 0, "samba_get_pac context");
	if (!mem_ctx) {
		return ENOMEM;
	}

	if (pk_reply_key != NULL) {
		cred_ndr_ptr = &cred_ndr;
	}

	is_krbtgt = krb5_principal_is_krbtgt(context, server->entry.principal);

	nt_status = samba_kdc_get_pac_blobs(mem_ctx, skdc_entry,
					    &logon_blob,
					    cred_ndr_ptr,
					    &upn_blob,
					    is_krbtgt ? &pac_attrs_blob : NULL,
					    pac_request,
					    is_krbtgt ? &requester_sid_blob : NULL,
					    NULL);
	if (!NT_STATUS_IS_OK(nt_status)) {
		talloc_free(mem_ctx);
		return EINVAL;
	}

	if (pk_reply_key != NULL && cred_ndr != NULL) {
		ret = samba_kdc_encrypt_pac_credentials(context,
							pk_reply_key,
							cred_ndr,
							mem_ctx,
							&_cred_blob);
		if (ret != 0) {
			talloc_free(mem_ctx);
			return ret;
		}
		cred_blob = &_cred_blob;
	}

	ret = samba_make_krb5_pac(context, logon_blob, cred_blob,
				  upn_blob, pac_attrs_blob,
				  requester_sid_blob, NULL, pac);

	talloc_free(mem_ctx);
	return ret;
}

static krb5_error_code samba_wdc_get_pac_compat(void *priv, krb5_context context,
						struct hdb_entry_ex *client,
						struct hdb_entry_ex *server,
						const krb5_boolean *pac_request,
						krb5_pac *pac)
{
	return samba_wdc_get_pac(priv, context, client, server, NULL, pac_request, pac);
}

static krb5_error_code samba_wdc_reget_pac2(krb5_context context,
					    const krb5_principal delegated_proxy_principal,
					    struct hdb_entry_ex *client,
					    struct hdb_entry_ex *server,
					    struct hdb_entry_ex *krbtgt,
					    krb5_pac *pac,
					    krb5_cksumtype ctype)
{
	struct samba_kdc_entry *server_skdc_entry =
		talloc_get_type_abort(server->ctx,
		struct samba_kdc_entry);
	struct samba_kdc_entry *krbtgt_skdc_entry =
		talloc_get_type_abort(krbtgt->ctx,
		struct samba_kdc_entry);
	TALLOC_CTX *mem_ctx = talloc_named(server_skdc_entry,
					   0,
					   "samba_kdc_reget_pac2 context");
	krb5_pac new_pac = NULL;
	DATA_BLOB *pac_blob = NULL;
	DATA_BLOB *upn_blob = NULL;
	DATA_BLOB *requester_sid_blob = NULL;
	DATA_BLOB *deleg_blob = NULL;
	krb5_error_code ret;
	NTSTATUS nt_status;
	bool is_in_db, is_untrusted;
	bool is_krbtgt;
	size_t num_types = 0;
	uint32_t *types = NULL;
	uint32_t forced_next_type = 0;
	size_t i = 0;
	ssize_t logon_info_idx = -1;
	ssize_t delegation_idx = -1;
	ssize_t logon_name_idx = -1;
	ssize_t upn_dns_info_idx = -1;
	ssize_t srv_checksum_idx = -1;
	ssize_t kdc_checksum_idx = -1;
	ssize_t tkt_checksum_idx = -1;
	ssize_t attrs_info_idx = -1;
	ssize_t requester_sid_idx = -1;
	ssize_t full_checksum_idx = -1;

	if (!mem_ctx) {
		return ENOMEM;
	}

	if (client != NULL) {
		struct samba_kdc_entry *client_skdc_entry = NULL;

		client_skdc_entry = talloc_get_type_abort(client->ctx,
							  struct samba_kdc_entry);

		/*
		 * Check the objectSID of the client and pac data are the same.
		 * Does a parse and SID check, but no crypto.
		 */
		ret = samba_kdc_validate_pac_blob(context, client_skdc_entry, *pac);
		if (ret != 0) {
			talloc_free(mem_ctx);
			return ret;
		}
	}

	/*
	 * If the krbtgt was generated by an RODC, and we are not that
	 * RODC, then we need to regenerate the PAC - we can't trust
	 * it, and confirm that the RODC was permitted to print this ticket
	 *
	 * Becasue of the samba_kdc_validate_pac_blob() step we can be
	 * sure that the record in 'client' matches the SID in the
	 * original PAC.
	 */
	ret = samba_krbtgt_is_in_db(krbtgt_skdc_entry, &is_in_db, &is_untrusted);
	if (ret != 0) {
		talloc_free(mem_ctx);
		return ret;
	}

	if (delegated_proxy_principal != NULL) {
		krb5_enctype etype;
		Key *key = NULL;

		if (!is_in_db) {
			/*
			 * The RODC-issued PAC was signed by a KDC entry that we
			 * don't have a key for. The server signature is not
			 * trustworthy, since it could have been created by the
			 * server we got the ticket from. We must not proceed as
			 * otherwise the ticket signature is unchecked.
			 */
			talloc_free(mem_ctx);
			return HDB_ERR_NOT_FOUND_HERE;
		}

		/* Fetch the correct key depending on the checksum type. */
		if (ctype == CKSUMTYPE_HMAC_MD5) {
			etype = ENCTYPE_ARCFOUR_HMAC;
		} else {
			ret = krb5_cksumtype_to_enctype(context,
							ctype,
							&etype);
			if (ret != 0) {
				talloc_free(mem_ctx);
				return ret;
			}
		}
		ret = hdb_enctype2key(context, &krbtgt->entry, etype, &key);
		if (ret != 0) {
			return ret;
		}

		/* Check the KDC, whole-PAC and ticket signatures. */
		ret = krb5_pac_verify(context,
				      *pac,
				      0,
				      NULL,
				      NULL,
				      &key->key);
		if (ret != 0) {
			DEBUG(1, ("PAC KDC signature failed to verify\n"));
			talloc_free(mem_ctx);
			return ret;
		}

		deleg_blob = talloc_zero(mem_ctx, DATA_BLOB);
		if (!deleg_blob) {
			talloc_free(mem_ctx);
			return ENOMEM;
		}

		nt_status = samba_kdc_update_delegation_info_blob(mem_ctx,
					context, *pac,
					server->entry.principal,
					delegated_proxy_principal,
					deleg_blob);
		if (!NT_STATUS_IS_OK(nt_status)) {
			DEBUG(0, ("Building PAC failed: %s\n",
				  nt_errstr(nt_status)));
			talloc_free(mem_ctx);
			return EINVAL;
		}
	}

	if (is_untrusted) {
		struct samba_kdc_entry *client_skdc_entry = NULL;
		struct auth_user_info_dc *user_info_dc = NULL;
		WERROR werr;

		if (client == NULL) {
			return KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN;
		}

		client_skdc_entry = talloc_get_type_abort(client->ctx,
							  struct samba_kdc_entry);

		nt_status = samba_kdc_get_pac_blobs(mem_ctx, client_skdc_entry,
						    &pac_blob, NULL, &upn_blob,
						    NULL, NULL, &requester_sid_blob,
						    &user_info_dc);
		if (!NT_STATUS_IS_OK(nt_status)) {
			talloc_free(mem_ctx);
			return KRB5KDC_ERR_TGT_REVOKED;
		}

		/*
		 * Now check if the SID list in the user_info_dc
		 * intersects correctly with the RODC allow/deny
		 * lists
		 */

		werr = samba_rodc_confirm_user_is_allowed(user_info_dc->num_sids,
							  user_info_dc->sids,
							  krbtgt_skdc_entry,
							  client_skdc_entry);
		if (!W_ERROR_IS_OK(werr)) {
			talloc_free(mem_ctx);
			if (W_ERROR_EQUAL(werr, WERR_DOMAIN_CONTROLLER_NOT_FOUND)) {
				return KRB5KDC_ERR_POLICY;
			} else {
				return KRB5KDC_ERR_TGT_REVOKED;
			}
		}
	}

	if (!is_untrusted) {
		pac_blob = talloc_zero(mem_ctx, DATA_BLOB);
		if (!pac_blob) {
			talloc_free(mem_ctx);
			return ENOMEM;
		}

		nt_status = samba_kdc_update_pac_blob(mem_ctx, context,
						      krbtgt_skdc_entry->kdc_db_ctx->samdb,
						      *pac, pac_blob,
						      NULL, NULL);
		if (!NT_STATUS_IS_OK(nt_status)) {
			DEBUG(0, ("Building PAC failed: %s\n",
				  nt_errstr(nt_status)));
			talloc_free(mem_ctx);
			return EINVAL;
		}
	}

	/* Check the types of the given PAC */
	ret = krb5_pac_get_types(context, *pac, &num_types, &types);
	if (ret != 0) {
		talloc_free(mem_ctx);
		return ret;
	}

	for (i = 0; i < num_types; i++) {
		switch (types[i]) {
		case PAC_TYPE_LOGON_INFO:
			if (logon_info_idx != -1) {
				DEBUG(1, ("logon info type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  logon_info_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			logon_info_idx = i;
			break;
		case PAC_TYPE_CONSTRAINED_DELEGATION:
			if (delegation_idx != -1) {
				DEBUG(1, ("constrained delegation type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  delegation_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			delegation_idx = i;
			break;
		case PAC_TYPE_LOGON_NAME:
			if (logon_name_idx != -1) {
				DEBUG(1, ("logon name type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  logon_name_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			logon_name_idx = i;
			break;
		case PAC_TYPE_UPN_DNS_INFO:
			if (upn_dns_info_idx != -1) {
				DEBUG(1, ("upn dns info type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  upn_dns_info_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			upn_dns_info_idx = i;
			break;
		case PAC_TYPE_SRV_CHECKSUM:
			if (srv_checksum_idx != -1) {
				DEBUG(1, ("server checksum type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  srv_checksum_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			srv_checksum_idx = i;
			break;
		case PAC_TYPE_KDC_CHECKSUM:
			if (kdc_checksum_idx != -1) {
				DEBUG(1, ("kdc checksum type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  kdc_checksum_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			kdc_checksum_idx = i;
			break;
		case PAC_TYPE_TICKET_CHECKSUM:
			if (tkt_checksum_idx != -1) {
				DEBUG(1, ("ticket checksum type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  tkt_checksum_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			tkt_checksum_idx = i;
			break;
		case PAC_TYPE_ATTRIBUTES_INFO:
			if (attrs_info_idx != -1) {
				DEBUG(1, ("attributes info type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  attrs_info_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			attrs_info_idx = i;
			break;
		case PAC_TYPE_REQUESTER_SID:
			if (requester_sid_idx != -1) {
				DEBUG(1, ("requester sid type[%"PRIu32"] twice [%zd] and [%zu]: \n",
					  types[i],
					  requester_sid_idx,
					  i));
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			requester_sid_idx = i;
			break;
		case PAC_TYPE_FULL_CHECKSUM:
			if (full_checksum_idx != -1) {
				DBG_WARNING("full checksum type[%"PRIu32"] twice "
					    "[%zd] and [%zu]: \n",
					    types[i],
					    full_checksum_idx,
					    i);
				SAFE_FREE(types);
				talloc_free(mem_ctx);
				return EINVAL;
			}
			full_checksum_idx = i;
			break;
		default:
			continue;
		}
	}

	if (logon_info_idx == -1) {
		DEBUG(1, ("PAC_TYPE_LOGON_INFO missing\n"));
		SAFE_FREE(types);
		talloc_free(mem_ctx);
		return EINVAL;
	}
	if (logon_name_idx == -1) {
		DEBUG(1, ("PAC_TYPE_LOGON_NAME missing\n"));
		SAFE_FREE(types);
		talloc_free(mem_ctx);
		return EINVAL;
	}
	if (srv_checksum_idx == -1) {
		DEBUG(1, ("PAC_TYPE_SRV_CHECKSUM missing\n"));
		SAFE_FREE(types);
		talloc_free(mem_ctx);
		return EINVAL;
	}
	if (kdc_checksum_idx == -1) {
		DEBUG(1, ("PAC_TYPE_KDC_CHECKSUM missing\n"));
		SAFE_FREE(types);
		talloc_free(mem_ctx);
		return EINVAL;
	}
	if (delegated_proxy_principal == NULL && requester_sid_idx == -1) {
		DEBUG(1, ("PAC_TYPE_REQUESTER_SID missing\n"));
		SAFE_FREE(types);
		talloc_free(mem_ctx);
		return KRB5KDC_ERR_TGT_REVOKED;
	}

	/*
	 * The server account may be set not to want the PAC.
	 *
	 * While this is wasteful if the above cacluations were done
	 * and now thrown away, this is cleaner as we do any ticket
	 * signature checking etc always.
	 *
	 * UF_NO_AUTH_DATA_REQUIRED is the rare case and most of the
	 * time (eg not accepting a ticket from the RODC) we do not
	 * need to re-generate anything anyway.
	 */
	if (!samba_princ_needs_pac(server_skdc_entry)) {
		ret = 0;
		new_pac = NULL;
		goto out;
	}

	is_krbtgt = krb5_principal_is_krbtgt(context, server->entry.principal);

	if (!is_untrusted && !is_krbtgt) {
		/*
		 * The client may have requested no PAC when obtaining the
		 * TGT.
		 */
		bool requested_pac;
		ret = samba_client_requested_pac(context, pac, mem_ctx,
						 &requested_pac);
		if (ret != 0 || !requested_pac) {
			new_pac = NULL;
			goto out;
		}
	}

	/* Otherwise build an updated PAC */
	ret = krb5_pac_init(context, &new_pac);
	if (ret != 0) {
		new_pac = NULL;
		goto out;
	}

	for (i = 0;;) {
		const uint8_t zero_byte = 0;
		krb5_data type_data;
		DATA_BLOB type_blob = data_blob_null;
		uint32_t type;

		if (forced_next_type != 0) {
			/*
			 * We need to inject possible missing types
			 */
			type = forced_next_type;
			forced_next_type = 0;
		} else if (i < num_types) {
			type = types[i];
			i++;
		} else {
			break;
		}

		switch (type) {
		case PAC_TYPE_LOGON_INFO:
			type_blob = *pac_blob;

			if (delegation_idx == -1 && deleg_blob != NULL) {
				/* inject CONSTRAINED_DELEGATION behind */
				forced_next_type = PAC_TYPE_CONSTRAINED_DELEGATION;
			}
			break;
		case PAC_TYPE_CONSTRAINED_DELEGATION:
			if (deleg_blob != NULL) {
				type_blob = *deleg_blob;
			}
			break;
		case PAC_TYPE_CREDENTIAL_INFO:
			/*
			 * Note that we copy the credential blob,
			 * as it's only usable with the PKINIT based
			 * AS-REP reply key, it's only available on the
			 * host which did the AS-REQ/AS-REP exchange.
			 *
			 * This matches Windows 2008R2...
			 */
			break;
		case PAC_TYPE_LOGON_NAME:
			/*
			 * this is generated in the main KDC code
			 * we just add a place holder here.
			 */
			type_blob = data_blob_const(&zero_byte, 1);

			if (upn_dns_info_idx == -1 && upn_blob != NULL) {
				/* inject UPN_DNS_INFO behind */
				forced_next_type = PAC_TYPE_UPN_DNS_INFO;
			}
			break;
		case PAC_TYPE_UPN_DNS_INFO:
			/*
			 * Replace in the RODC case, otherwise
			 * upn_blob is NULL and we just copy.
			 */
			if (upn_blob != NULL) {
				type_blob = *upn_blob;
			}
			break;
		case PAC_TYPE_SRV_CHECKSUM:
			/*
			 * this are generated in the main KDC code
			 * we just add a place holder here.
			 */
			type_blob = data_blob_const(&zero_byte, 1);

			if (requester_sid_idx == -1 && requester_sid_blob != NULL) {
				/* inject REQUESTER_SID behind */
				forced_next_type = PAC_TYPE_REQUESTER_SID;
			}
			break;
		case PAC_TYPE_KDC_CHECKSUM:
			/*
			 * this are generated in the main KDC code
			 * we just add a place holders here.
			 */
			type_blob = data_blob_const(&zero_byte, 1);
			break;
		case PAC_TYPE_ATTRIBUTES_INFO:
			if (!is_untrusted && is_krbtgt) {
				/* just copy... */
				break;
			} else {
				continue;
			}
		case PAC_TYPE_REQUESTER_SID:
			if (is_krbtgt) {
				/*
				 * Replace in the RODC case, otherwise
				 * requester_sid_blob is NULL and we just copy.
				 */
				if (requester_sid_blob != NULL) {
					type_blob = *requester_sid_blob;
				}
				break;
			} else {
				continue;
			}
		case PAC_TYPE_FULL_CHECKSUM:
			/*
			 * this is generated in the main KDC code
			 * we just add a place holder here.
			 */
			type_blob = data_blob_const(&zero_byte, 1);
			break;
		default:
			/* just copy... */
			break;
		}

		if (type_blob.length != 0) {
			ret = smb_krb5_copy_data_contents(&type_data,
							  type_blob.data,
							  type_blob.length);
			if (ret != 0) {
				SAFE_FREE(types);
				krb5_pac_free(context, new_pac);
				talloc_free(mem_ctx);
				return ret;
			}
		} else {
			ret = krb5_pac_get_buffer(context, *pac,
						  type, &type_data);
			if (ret != 0) {
				SAFE_FREE(types);
				krb5_pac_free(context, new_pac);
				talloc_free(mem_ctx);
				return ret;
			}
		}

		ret = krb5_pac_add_buffer(context, new_pac,
					  type, &type_data);
		smb_krb5_free_data_contents(context, &type_data);
		if (ret != 0) {
			SAFE_FREE(types);
			krb5_pac_free(context, new_pac);
			talloc_free(mem_ctx);
			return ret;
		}
	}

out:

	SAFE_FREE(types);

	/* We now replace the pac */
	krb5_pac_free(context, *pac);
	*pac = new_pac;

	talloc_free(mem_ctx);
	return ret;
}

/* Resign (and reform, including possibly new groups) a PAC */

static krb5_error_code samba_wdc_reget_pac(void *priv, krb5_context context,
					   const krb5_principal client_principal,
					   const krb5_principal delegated_proxy_principal,
					   struct hdb_entry_ex *client,
					   struct hdb_entry_ex *server,
					   struct hdb_entry_ex *krbtgt,
					   krb5_pac *pac)
{
	struct samba_kdc_entry *krbtgt_skdc_entry =
		talloc_get_type_abort(krbtgt->ctx,
				      struct samba_kdc_entry);
	krb5_error_code ret;
	krb5_cksumtype ctype = CKSUMTYPE_NONE;
	struct hdb_entry_ex signing_krbtgt_hdb;

	if (delegated_proxy_principal) {
		uint16_t rodc_id;
		unsigned int my_krbtgt_number;

		/*
		 * We're using delegated_proxy_principal for the moment to
		 * indicate cases where the ticket was encrypted with the server
		 * key, and not a krbtgt key. This cannot be trusted, so we need
		 * to find a krbtgt key that signs the PAC in order to trust the
		 * ticket.
		 *
		 * The krbtgt passed in to this function refers to the krbtgt
		 * used to decrypt the ticket of the server requesting
		 * S4U2Proxy.
		 *
		 * When we implement service ticket renewal, we need to check
		 * the PAC, and this will need to be updated.
		 */
		ret = krb5_pac_get_kdc_checksum_info(context,
						     *pac,
						     &ctype,
						     &rodc_id);
		if (ret != 0) {
			DEBUG(1, ("Failed to get PAC checksum info\n"));
			return ret;
		}

		/*
		 * We need to check the KDC and ticket signatures, fetching the
		 * correct key based on the enctype.
		 */

		my_krbtgt_number = krbtgt_skdc_entry->kdc_db_ctx->my_krbtgt_number;

		if (my_krbtgt_number != 0) {
			/*
			 * If we are an RODC, and we are not the KDC that signed
			 * the evidence ticket, then we need to proxy the
			 * request.
			 */
			if (rodc_id != my_krbtgt_number) {
				return HDB_ERR_NOT_FOUND_HERE;
			}
		} else {
			/*
			 * If we are a DC, the ticket may have been signed by a
			 * different KDC than the one that issued the header
			 * ticket.
			 */
			if (rodc_id != krbtgt->entry.kvno >> 16) {
				struct sdb_entry_ex signing_krbtgt_sdb;

				/*
				 * If we didn't sign the ticket, then return an
				 * error.
				 */
				if (rodc_id != 0) {
					return KRB5KRB_AP_ERR_MODIFIED;
				}

				/*
				 * Fetch our key from the database. To support
				 * key rollover, we're going to need to try
				 * multiple keys by trial and error. For now,
				 * krbtgt keys aren't assumed to change.
				 */
				ret = samba_kdc_fetch(context,
						      krbtgt_skdc_entry->kdc_db_ctx,
						      krbtgt->entry.principal,
						      SDB_F_GET_KRBTGT | SDB_F_CANON,
						      0,
						      &signing_krbtgt_sdb);
				if (ret != 0) {
					return ret;
				}

				ret = sdb_entry_ex_to_hdb_entry_ex(context,
								   &signing_krbtgt_sdb,
								   &signing_krbtgt_hdb);
				sdb_free_entry(&signing_krbtgt_sdb);
				if (ret != 0) {
					return ret;
				}

				/*
				 * Replace the krbtgt entry with our own entry
				 * for further processing.
				 */
				krbtgt = &signing_krbtgt_hdb;
			}
		}
	}

	ret = samba_wdc_reget_pac2(context,
				   delegated_proxy_principal,
				   client,
				   server,
				   krbtgt,
				   pac,
				   ctype);

	if (krbtgt == &signing_krbtgt_hdb) {
		hdb_free_entry(context, &signing_krbtgt_hdb);
	}

	return ret;
}

static char *get_netbios_name(TALLOC_CTX *mem_ctx, HostAddresses *addrs)
{
	char *nb_name = NULL;
	size_t len;
	unsigned int i;

	for (i = 0; addrs && i < addrs->len; i++) {
		if (addrs->val[i].addr_type != KRB5_ADDRESS_NETBIOS) {
			continue;
		}
		len = MIN(addrs->val[i].address.length, 15);
		nb_name = talloc_strndup(mem_ctx,
					 addrs->val[i].address.data, len);
		if (nb_name) {
			break;
		}
	}

	if ((nb_name == NULL) || (nb_name[0] == '\0')) {
		return NULL;
	}

	/* Strip space padding */
	for (len = strlen(nb_name) - 1;
	     (len > 0) && (nb_name[len] == ' ');
	     --len) {
		nb_name[len] = '\0';
	}

	return nb_name;
}

static krb5_data fill_krb5_data(void *data, size_t length)
{
	krb5_data kdata;

	kdata.data = data;
	kdata.length = length;

	return kdata;
}

/* this function allocates 'data' using malloc.
 * The caller is responsible for freeing it */
static void samba_kdc_build_edata_reply(NTSTATUS nt_status, DATA_BLOB *e_data)
{
	krb5_error_code ret = 0;
	PA_DATA pa;
	unsigned char *buf;
	size_t len;

	if (!e_data)
		return;

	e_data->data   = NULL;
	e_data->length = 0;

	pa.padata_type		= KRB5_PADATA_PW_SALT;
	pa.padata_value.length	= 12;
	pa.padata_value.data	= malloc(pa.padata_value.length);
	if (!pa.padata_value.data) {
		e_data->length = 0;
		e_data->data = NULL;
		return;
	}

	SIVAL(pa.padata_value.data, 0, NT_STATUS_V(nt_status));
	SIVAL(pa.padata_value.data, 4, 0);
	SIVAL(pa.padata_value.data, 8, 1);

	ASN1_MALLOC_ENCODE(PA_DATA, buf, len, &pa, &len, ret);
	free(pa.padata_value.data);
	if (ret) {
		return;
	}

	e_data->data   = buf;
	e_data->length = len;

	return;
}


static krb5_error_code samba_wdc_check_client_access(void *priv,
						     krb5_context context,
						     krb5_kdc_configuration *config,
						     hdb_entry_ex *client_ex, const char *client_name,
						     hdb_entry_ex *server_ex, const char *server_name,
						     KDC_REQ *req,
						     krb5_data *e_data)
{
	struct samba_kdc_entry *kdc_entry;
	bool password_change;
	char *workstation;
	NTSTATUS nt_status;

	kdc_entry = talloc_get_type(client_ex->ctx, struct samba_kdc_entry);
	password_change = (server_ex && server_ex->entry.flags.change_pw);
	workstation = get_netbios_name((TALLOC_CTX *)client_ex->ctx,
					req->req_body.addresses);

	nt_status = samba_kdc_check_client_access(kdc_entry,
						  client_name,
						  workstation,
						  password_change);

	if (!NT_STATUS_IS_OK(nt_status)) {
		if (NT_STATUS_EQUAL(nt_status, NT_STATUS_NO_MEMORY)) {
			return ENOMEM;
		}

		if (e_data) {
			DATA_BLOB data;

			samba_kdc_build_edata_reply(nt_status, &data);
			*e_data = fill_krb5_data(data.data, data.length);
		}

		return samba_kdc_map_policy_err(nt_status);
	}

	/* Now do the standard Heimdal check */
	return kdc_check_flags(context, config,
			       client_ex, client_name,
			       server_ex, server_name,
			       req->msg_type == krb_as_req);
}

static krb5_error_code samba_wdc_plugin_init(krb5_context context, void **ptr)
{
	*ptr = NULL;
	return 0;
}

static void samba_wdc_plugin_fini(void *ptr)
{
	return;
}

struct krb5plugin_windc_ftable windc_plugin_table = {
	.minor_version = KRB5_WINDC_PLUGIN_MINOR,
	.init = samba_wdc_plugin_init,
	.fini = samba_wdc_plugin_fini,
	.pac_generate = samba_wdc_get_pac_compat,
	.pac_verify = samba_wdc_reget_pac,
	.client_access = samba_wdc_check_client_access,
	.pac_pk_generate = samba_wdc_get_pac,
};