/* 
   Unix SMB/CIFS implementation.
   kerberos utility library
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Remus Koos 2001
   Copyright (C) Luke Howard 2003   
   Copyright (C) Guenther Deschner 2003
   Copyright (C) Jim McDonough (jmcd@us.ibm.com) 2003
   
   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 2 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, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

#ifdef HAVE_KRB5

static DATA_BLOB unwrap_pac(TALLOC_CTX *mem_ctx, DATA_BLOB *auth_data)
{
	DATA_BLOB out;
	DATA_BLOB pac_contents = data_blob(NULL, 0);
	ASN1_DATA data;
	int data_type;
	if (!auth_data->length) {
		return data_blob(NULL, 0);
	}

	asn1_load(&data, *auth_data);
	asn1_start_tag(&data, ASN1_SEQUENCE(0));
	asn1_start_tag(&data, ASN1_SEQUENCE(0));
	asn1_start_tag(&data, ASN1_CONTEXT(0));
	asn1_read_Integer(&data, &data_type);
	asn1_end_tag(&data);
	asn1_start_tag(&data, ASN1_CONTEXT(1));
	asn1_read_OctetString(&data, &pac_contents);
	asn1_end_tag(&data);
	asn1_end_tag(&data);
	asn1_end_tag(&data);
	asn1_free(&data);

	out = data_blob_talloc(mem_ctx, pac_contents.data, pac_contents.length);

	data_blob_free(&pac_contents);

	return out;
}

/**********************************************************************************
 Try to verify a ticket using the system keytab... the system keytab has kvno -1 entries, so
 it's more like what microsoft does... see comment in utils/net_ads.c in the
 ads_keytab_add_entry function for details.
***********************************************************************************/

static BOOL ads_keytab_verify_ticket(krb5_context context, krb5_auth_context auth_context,
			const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt,
			krb5_keyblock *keyblock)
{
	krb5_error_code ret = 0;
	BOOL auth_ok = False;

	krb5_keytab keytab = NULL;
	krb5_kt_cursor cursor;
	krb5_keytab_entry kt_entry;
	char *princ_name = NULL;

	ZERO_STRUCT(kt_entry);
	ZERO_STRUCT(cursor);

	ZERO_STRUCTP(keyblock);

	ret = krb5_kt_default(context, &keytab);
	if (ret) {
		DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_default failed (%s)\n", error_message(ret)));
		goto out;
	}

	ret = krb5_kt_start_seq_get(context, keytab, &cursor);
	if (ret) {
		DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_start_seq_get failed (%s)\n", error_message(ret)));
		goto out;
	}

	while (!krb5_kt_next_entry(context, keytab, &kt_entry, &cursor)) {
		ret = krb5_unparse_name(context, kt_entry.principal, &princ_name);
		if (ret) {
			DEBUG(1, ("ads_keytab_verify_ticket: krb5_unparse_name failed (%s)\n", error_message(ret)));
			goto out;
		}
		/* Look for a CIFS ticket */
		if (!strncasecmp(princ_name, "cifs/", 5) || (!strncasecmp(princ_name, "host/", 5))) {
#ifdef HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK
			krb5_auth_con_setuseruserkey(context, auth_context, &kt_entry.keyblock);
#else
			krb5_auth_con_setuseruserkey(context, auth_context, &kt_entry.key);
#endif

			p_packet->length = ticket->length;
			p_packet->data = (krb5_pointer)ticket->data;

			ret = krb5_rd_req(context, &auth_context, p_packet, NULL, NULL, NULL, pp_tkt);
			if (!ret) {
				unsigned int keytype;
				krb5_free_unparsed_name(context, princ_name);
				princ_name = NULL;
#ifdef HAVE_KRB5_KEYTAB_ENTRY_KEYBLOCK
				keytype = (unsigned int) kt_entry.keyblock.keytype;
				copy_EncryptionKey(&kt_entry.keyblock, keyblock);
#else
				keytype = (unsigned int) kt_entry.key.enctype;
				/* TODO: copy the keyblock on MIT krb5*/
#endif
				DEBUG(10,("ads_keytab_verify_ticket: enc type [%u] decrypted message !\n",
					  keytype));
				
				auth_ok = True;
				break;
			}
		}
		krb5_free_unparsed_name(context, princ_name);
		princ_name = NULL;
	}
	if (ret && ret != KRB5_KT_END) {
		/* This failed because something went wrong, not because the keytab file was empty. */
		DEBUG(1, ("ads_keytab_verify_ticket: krb5_kt_next_entry failed (%s)\n", error_message(ret)));
		goto out;
	}

  out:

	if (princ_name) {
		krb5_free_unparsed_name(context, princ_name);
	}
	{
		krb5_kt_cursor zero_csr;
		ZERO_STRUCT(zero_csr);
		if ((memcmp(&cursor, &zero_csr, sizeof(krb5_kt_cursor)) != 0) && keytab) {
			krb5_kt_end_seq_get(context, keytab, &cursor);
		}
	}
	if (keytab) {
		krb5_kt_close(context, keytab);
	}

	return auth_ok;
}

/**********************************************************************************
 Try to verify a ticket using the secrets.tdb.
***********************************************************************************/

static BOOL ads_secrets_verify_ticket(krb5_context context, krb5_auth_context auth_context,
			krb5_principal host_princ,
			const DATA_BLOB *ticket, krb5_data *p_packet, krb5_ticket **pp_tkt,
			krb5_keyblock *keyblock)
{
	krb5_error_code ret = 0;
	BOOL auth_ok = False;
	char *password_s = NULL;
	krb5_data password;
	krb5_enctype *enctypes = NULL;
	int i;

	ZERO_STRUCTP(keyblock);

	if (!secrets_init()) {
		DEBUG(1,("ads_secrets_verify_ticket: secrets_init failed\n"));
		return False;
	}

	password_s = secrets_fetch_machine_password(lp_workgroup());
	if (!password_s) {
		DEBUG(1,("ads_secrets_verify_ticket: failed to fetch machine password\n"));
		return False;
	}

	password.data = password_s;
	password.length = strlen(password_s);

	/* CIFS doesn't use addresses in tickets. This would break NAT. JRA */

	if ((ret = get_kerberos_allowed_etypes(context, &enctypes))) {
		DEBUG(1,("ads_secrets_verify_ticket: krb5_get_permitted_enctypes failed (%s)\n", 
			 error_message(ret)));
		goto out;
	}

	p_packet->length = ticket->length;
	p_packet->data = (krb5_pointer)ticket->data;

	/* We need to setup a auth context with each possible encoding type in turn. */
	for (i=0;enctypes[i];i++) {
		if (create_kerberos_key_from_string(context, host_princ, &password, keyblock, enctypes[i])) {
			continue;
		}

		krb5_auth_con_setuseruserkey(context, auth_context, keyblock);

		ret = krb5_rd_req(context, &auth_context, p_packet, 
					NULL,
					NULL, NULL, pp_tkt);
		if (!ret) {
			DEBUG(10,("ads_secrets_verify_ticket: enc type [%u] decrypted message !\n",
				(unsigned int)enctypes[i] ));
			auth_ok = True;
			break;
		}

		krb5_free_keyblock(context, keyblock);

		DEBUG((ret != KRB5_BAD_ENCTYPE) ? 3 : 10,
				("ads_secrets_verify_ticket: enc type [%u] failed to decrypt with error %s\n",
				(unsigned int)enctypes[i], error_message(ret)));
	}

 out:

	free_kerberos_etypes(context, enctypes);
	SAFE_FREE(password_s);

	return auth_ok;
}

/**********************************************************************************
 Verify an incoming ticket and parse out the principal name and 
 authorization_data if available.
***********************************************************************************/

 NTSTATUS ads_verify_ticket(TALLOC_CTX *mem_ctx, 
			   krb5_context context,
			   krb5_auth_context auth_context,
			   const char *realm, const DATA_BLOB *ticket, 
			   char **principal, DATA_BLOB *auth_data,
			   DATA_BLOB *ap_rep,
			   krb5_keyblock *keyblock)
{
	NTSTATUS sret = NT_STATUS_LOGON_FAILURE;
	krb5_data packet;
	krb5_ticket *tkt = NULL;
	krb5_rcache rcache = NULL;
	int ret;

	krb5_principal host_princ = NULL;
	char *host_princ_s = NULL;
	BOOL got_replay_mutex = False;

	char *myname;
	BOOL auth_ok = False;

	char *malloc_principal;

	ZERO_STRUCT(packet);
	ZERO_STRUCTP(auth_data);
	ZERO_STRUCTP(ap_rep);

	/* This whole process is far more complex than I would
           like. We have to go through all this to allow us to store
           the secret internally, instead of using /etc/krb5.keytab */

	myname = name_to_fqdn(mem_ctx, lp_netbios_name());
	strlower_m(myname);
	asprintf(&host_princ_s, "host/%s@%s", myname, lp_realm());
	ret = krb5_parse_name(context, host_princ_s, &host_princ);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_parse_name(%s) failed (%s)\n",
					host_princ_s, error_message(ret)));
		goto out;
	}


	/* Lock a mutex surrounding the replay as there is no locking in the MIT krb5
	 * code surrounding the replay cache... */

	if (!grab_server_mutex("replay cache mutex")) {
		DEBUG(1,("ads_verify_ticket: unable to protect replay cache with mutex.\n"));
		goto out;
	}

	got_replay_mutex = True;

	/*
	 * JRA. We must set the rcache here. This will prevent replay attacks.
	 */

	ret = krb5_get_server_rcache(context, krb5_princ_component(context, host_princ, 0), &rcache);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_get_server_rcache failed (%s)\n", error_message(ret)));
		goto out;
	}

	ret = krb5_auth_con_setrcache(context, auth_context, rcache);
	if (ret) {
		DEBUG(1,("ads_verify_ticket: krb5_auth_con_setrcache failed (%s)\n", error_message(ret)));
		goto out;
	}

	auth_ok = ads_keytab_verify_ticket(context, auth_context, ticket, &packet, &tkt, keyblock);
	if (!auth_ok) {
		auth_ok = ads_secrets_verify_ticket(context, auth_context, host_princ,
							ticket, &packet, &tkt, keyblock);
	}

	release_server_mutex();
	got_replay_mutex = False;

	if (!auth_ok) {
		DEBUG(3,("ads_verify_ticket: krb5_rd_req with auth failed (%s)\n", 
			 error_message(ret)));
		goto out;
	}

	ret = krb5_mk_rep(context, auth_context, &packet);
	if (ret) {
		DEBUG(3,("ads_verify_ticket: Failed to generate mutual authentication reply (%s)\n",
			error_message(ret)));
		goto out;
	}

	*ap_rep = data_blob_talloc(mem_ctx, packet.data, packet.length);
	SAFE_FREE(packet.data);
	packet.length = 0;

#if 0
	file_save("/tmp/ticket.dat", ticket->data, ticket->length);
#endif

	*auth_data = get_auth_data_from_tkt(mem_ctx, tkt);

	*auth_data = unwrap_pac(mem_ctx, auth_data);

#if 0
	if (tkt->enc_part2) {
		file_save("/tmp/authdata.dat",
			  tkt->enc_part2->authorization_data[0]->contents,
			  tkt->enc_part2->authorization_data[0]->length);
	}
#endif

	if ((ret = krb5_unparse_name(context, get_principal_from_tkt(tkt),
				     &malloc_principal))) {
		DEBUG(3,("ads_verify_ticket: krb5_unparse_name failed (%s)\n", 
			 error_message(ret)));
		sret = NT_STATUS_LOGON_FAILURE;
		goto out;
	}

	*principal = talloc_strdup(mem_ctx, malloc_principal);
	SAFE_FREE(malloc_principal);
	if (!principal) {
		DEBUG(3,("ads_verify_ticket: talloc_strdup() failed\n"));
		sret = NT_STATUS_NO_MEMORY;
		goto out;
	}

	sret = NT_STATUS_OK;

 out:

	if (got_replay_mutex) {
		release_server_mutex();
	}

	if (!NT_STATUS_IS_OK(sret)) {
		data_blob_free(auth_data);
	}

	if (!NT_STATUS_IS_OK(sret)) {
		data_blob_free(ap_rep);
	}

	if (host_princ) {
		krb5_free_principal(context, host_princ);
	}

	if (tkt != NULL) {
		krb5_free_ticket(context, tkt);
	}

	SAFE_FREE(host_princ_s);

	return sret;
}

#endif /* HAVE_KRB5 */