/*
   Unix SMB/CIFS implementation.

   module to store/fetch session keys for the schannel server

   Copyright (C) Andrew Tridgell 2004
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2006-2009
   Copyright (C) Guenther Deschner 2009

   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 "system/filesys.h"
#include "../lib/tdb/include/tdb.h"
#include "../lib/util/util_tdb.h"
#include "../lib/param/param.h"
#include "../libcli/auth/schannel.h"
#include "../librpc/gen_ndr/ndr_schannel.h"
#include "lib/dbwrap/dbwrap.h"

#define SECRETS_SCHANNEL_STATE "SECRETS/SCHANNEL"

/******************************************************************************
 Open or create the schannel session store tdb.  Non-static so it can
 be called from parent processes to corectly handle TDB_CLEAR_IF_FIRST
*******************************************************************************/

struct db_context *open_schannel_session_store(TALLOC_CTX *mem_ctx,
					       struct loadparm_context *lp_ctx)
{
	struct db_context *db_sc = NULL;
	char *fname = lpcfg_private_db_path(mem_ctx, lp_ctx, "schannel_store");
	int hash_size, tdb_flags;

	if (!fname) {
		return NULL;
	}

	hash_size = lpcfg_tdb_hash_size(lp_ctx, fname);
	tdb_flags = lpcfg_tdb_flags(lp_ctx, TDB_CLEAR_IF_FIRST|TDB_NOSYNC);

	db_sc = dbwrap_local_open(
		mem_ctx,
		fname,
		hash_size,
		tdb_flags,
		O_RDWR|O_CREAT,
		0600,
		DBWRAP_LOCK_ORDER_NONE,
		DBWRAP_FLAG_NONE);

	if (!db_sc) {
		DEBUG(0,("open_schannel_session_store: Failed to open %s - %s\n",
			 fname, strerror(errno)));
		TALLOC_FREE(fname);
		return NULL;
	}

	TALLOC_FREE(fname);

	return db_sc;
}

/********************************************************************
 ********************************************************************/

static
NTSTATUS schannel_store_session_key_tdb(struct db_context *db_sc,
					TALLOC_CTX *mem_ctx,
					struct netlogon_creds_CredentialState *creds)
{
	enum ndr_err_code ndr_err;
	DATA_BLOB blob;
	TDB_DATA value;
	char *keystr;
	char *name_upper;
	NTSTATUS status;

	if (strlen(creds->computer_name) > 15) {
		/*
		 * We may want to check for a completely
		 * valid netbios name.
		 */
		return STATUS_BUFFER_OVERFLOW;
	}

	name_upper = strupper_talloc(mem_ctx, creds->computer_name);
	if (!name_upper) {
		return NT_STATUS_NO_MEMORY;
	}

	keystr = talloc_asprintf(mem_ctx, "%s/%s",
				 SECRETS_SCHANNEL_STATE, name_upper);
	TALLOC_FREE(name_upper);
	if (!keystr) {
		return NT_STATUS_NO_MEMORY;
	}

	ndr_err = ndr_push_struct_blob(&blob, mem_ctx, creds,
			(ndr_push_flags_fn_t)ndr_push_netlogon_creds_CredentialState);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		talloc_free(keystr);
		return ndr_map_error2ntstatus(ndr_err);
	}

	value.dptr = blob.data;
	value.dsize = blob.length;

	status = dbwrap_store_bystring(db_sc, keystr, value, TDB_REPLACE);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(0,("Unable to add %s to session key db - %s\n",
			 keystr, nt_errstr(status)));
		talloc_free(keystr);
		return status;
	}

	DEBUG(3,("schannel_store_session_key_tdb: stored schannel info with key %s\n",
		keystr));

	if (DEBUGLEVEL >= 10) {
		NDR_PRINT_DEBUG(netlogon_creds_CredentialState, creds);
	}

	talloc_free(keystr);

	return NT_STATUS_OK;
}

/********************************************************************
 ********************************************************************/

static
NTSTATUS schannel_fetch_session_key_tdb(struct db_context *db_sc,
					TALLOC_CTX *mem_ctx,
					const char *computer_name,
					struct netlogon_creds_CredentialState **pcreds)
{
	NTSTATUS status;
	TDB_DATA value;
	enum ndr_err_code ndr_err;
	DATA_BLOB blob;
	struct netlogon_creds_CredentialState *creds = NULL;
	char *keystr = NULL;
	char *name_upper;

	*pcreds = NULL;

	name_upper = strupper_talloc(mem_ctx, computer_name);
	if (!name_upper) {
		return NT_STATUS_NO_MEMORY;
	}

	keystr = talloc_asprintf(mem_ctx, "%s/%s",
				 SECRETS_SCHANNEL_STATE, name_upper);
	TALLOC_FREE(name_upper);
	if (!keystr) {
		return NT_STATUS_NO_MEMORY;
	}

	status = dbwrap_fetch_bystring(db_sc, keystr, keystr, &value);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(10,("schannel_fetch_session_key_tdb: Failed to find entry with key %s\n",
			keystr ));
		goto done;
	}

	creds = talloc_zero(mem_ctx, struct netlogon_creds_CredentialState);
	if (!creds) {
		status = NT_STATUS_NO_MEMORY;
		goto done;
	}

	blob = data_blob_const(value.dptr, value.dsize);

	ndr_err = ndr_pull_struct_blob(&blob, creds, creds,
			(ndr_pull_flags_fn_t)ndr_pull_netlogon_creds_CredentialState);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		status = ndr_map_error2ntstatus(ndr_err);
		goto done;
	}

	if (DEBUGLEVEL >= 10) {
		NDR_PRINT_DEBUG(netlogon_creds_CredentialState, creds);
	}

	DEBUG(3,("schannel_fetch_session_key_tdb: restored schannel info key %s\n",
		keystr));

	status = NT_STATUS_OK;

 done:

	talloc_free(keystr);

	if (!NT_STATUS_IS_OK(status)) {
		talloc_free(creds);
		return status;
	}

	*pcreds = creds;

	return NT_STATUS_OK;
}

/******************************************************************************
 Wrapper around schannel_fetch_session_key_tdb()
 Note we must be root here.
*******************************************************************************/

NTSTATUS schannel_get_creds_state(TALLOC_CTX *mem_ctx,
				  struct loadparm_context *lp_ctx,
				  const char *computer_name,
				  struct netlogon_creds_CredentialState **_creds)
{
	TALLOC_CTX *tmpctx;
	struct db_context *db_sc;
	struct netlogon_creds_CredentialState *creds;
	NTSTATUS status;

	tmpctx = talloc_named(mem_ctx, 0, "schannel_get_creds_state");
	if (!tmpctx) {
		return NT_STATUS_NO_MEMORY;
	}

	db_sc = open_schannel_session_store(tmpctx, lp_ctx);
	if (!db_sc) {
		return NT_STATUS_ACCESS_DENIED;
	}

	status = schannel_fetch_session_key_tdb(db_sc, tmpctx,
						computer_name, &creds);
	if (NT_STATUS_IS_OK(status)) {
		*_creds = talloc_steal(mem_ctx, creds);
		if (!*_creds) {
			status = NT_STATUS_NO_MEMORY;
		}
	}

	talloc_free(tmpctx);
	return status;
}

/******************************************************************************
 Wrapper around schannel_store_session_key_tdb()
 Note we must be root here.
*******************************************************************************/

NTSTATUS schannel_save_creds_state(TALLOC_CTX *mem_ctx,
				   struct loadparm_context *lp_ctx,
				   struct netlogon_creds_CredentialState *creds)
{
	TALLOC_CTX *tmpctx;
	struct db_context *db_sc;
	NTSTATUS status;

	tmpctx = talloc_named(mem_ctx, 0, "schannel_save_creds_state");
	if (!tmpctx) {
		return NT_STATUS_NO_MEMORY;
	}

	db_sc = open_schannel_session_store(tmpctx, lp_ctx);
	if (!db_sc) {
		status = NT_STATUS_ACCESS_DENIED;
		goto fail;
	}

	status = schannel_store_session_key_tdb(db_sc, tmpctx, creds);

fail:
	talloc_free(tmpctx);
	return status;
}


/*
 * Create a very lossy hash of the computer name.
 *
 * The idea here is to compress the computer name into small space so
 * that malicious clients cannot fill the database with junk, as only a
 * maximum of 16k of entries are possible.
 *
 * Collisions are certainly possible, and the design behaves in the
 * same way as when the hostname is reused, but clients that use the
 * same connection do not go via the cache, and the cache only needs
 * to function between the ReqChallenge and ServerAuthenticate
 * packets.
 */
static void hash_computer_name(const char *computer_name,
			       char keystr[16])
{
	unsigned int hash;
	TDB_DATA computer_tdb_data = {
		.dptr = (uint8_t *)discard_const_p(char, computer_name),
		.dsize = strlen(computer_name)
	};
	hash = tdb_jenkins_hash(&computer_tdb_data);

	/* we are using 14 bits of the digest to index our connections, so
	   that we use at most 16,384 buckets.*/
	snprintf(keystr, 15, "CHALLENGE/%x%x", hash & 0xFF,
		 (hash & 0xFF00 >> 8) & 0x3f);
	return;
}


static
NTSTATUS schannel_store_challenge_tdb(struct db_context *db_sc,
				      TALLOC_CTX *mem_ctx,
				      const struct netr_Credential *client_challenge,
				      const struct netr_Credential *server_challenge,
				      const char *computer_name)
{
	enum ndr_err_code ndr_err;
	DATA_BLOB blob;
	TDB_DATA value;
	char *name_upper = NULL;
	NTSTATUS status;
	char keystr[16] = { 0, };
	struct netlogon_cache_entry cache_entry;

	if (strlen(computer_name) > 255) {
		/*
		 * We don't make this a limit at 15 chars as Samba has
		 * a test showing this can be longer :-(
		 */
		return STATUS_BUFFER_OVERFLOW;
	}

	name_upper = strupper_talloc(mem_ctx, computer_name);
	if (name_upper == NULL) {
		return NT_STATUS_NO_MEMORY;
	}

	hash_computer_name(name_upper, keystr);

	cache_entry.computer_name = name_upper;
	cache_entry.client_challenge = *client_challenge;
	cache_entry.server_challenge = *server_challenge;

	ndr_err = ndr_push_struct_blob(&blob, mem_ctx, &cache_entry,
			       (ndr_push_flags_fn_t)ndr_push_netlogon_cache_entry);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		return NT_STATUS_UNSUCCESSFUL;
	}

	value.dptr = blob.data;
	value.dsize = blob.length;

	status = dbwrap_store_bystring(db_sc, keystr, value, TDB_REPLACE);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(0,("%s: failed to stored challenge info for '%s' "
			 "with key %s - %s\n",
			 __func__, cache_entry.computer_name, keystr,
			 nt_errstr(status)));
		return status;
	}

	DEBUG(3,("%s: stored challenge info for '%s' with key %s\n",
		__func__, cache_entry.computer_name, keystr));

	if (DEBUGLEVEL >= 10) {
		NDR_PRINT_DEBUG(netlogon_cache_entry, &cache_entry);
	}

	return NT_STATUS_OK;
}

/********************************************************************
 Fetch a single challenge from the TDB.
 ********************************************************************/

static
NTSTATUS schannel_fetch_challenge_tdb(struct db_context *db_sc,
				      TALLOC_CTX *mem_ctx,
				      struct netr_Credential *client_challenge,
				      struct netr_Credential *server_challenge,
				      const char *computer_name)
{
	NTSTATUS status;
	TDB_DATA value;
	enum ndr_err_code ndr_err;
	DATA_BLOB blob;
	char keystr[16] = { 0, };
	struct netlogon_cache_entry cache_entry;
	char *name_upper = NULL;

	name_upper = strupper_talloc(mem_ctx, computer_name);
	if (name_upper == NULL) {
		return NT_STATUS_NO_MEMORY;
	}

	hash_computer_name(name_upper, keystr);

	status = dbwrap_fetch_bystring(db_sc, mem_ctx, keystr, &value);
	if (!NT_STATUS_IS_OK(status)) {
		DEBUG(3,("%s: Failed to find entry for %s with key %s - %s\n",
			__func__, name_upper, keystr, nt_errstr(status)));
		goto done;
	}

	blob = data_blob_const(value.dptr, value.dsize);

	ndr_err = ndr_pull_struct_blob_all(&blob, mem_ctx, &cache_entry,
					   (ndr_pull_flags_fn_t)ndr_pull_netlogon_cache_entry);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		status = ndr_map_error2ntstatus(ndr_err);
		DEBUG(3,("%s: Failed to parse entry for %s with key %s - %s\n",
			__func__, name_upper, keystr, nt_errstr(status)));
		goto done;
	}

	if (DEBUGLEVEL >= 10) {
		NDR_PRINT_DEBUG(netlogon_cache_entry, &cache_entry);
	}

	if (strcmp(cache_entry.computer_name, name_upper) != 0) {
		status = NT_STATUS_NOT_FOUND;

		DEBUG(1, ("%s: HASH COLLISION with key %s ! "
			  "Wanted to fetch record for %s but got %s.",
			  __func__, keystr, name_upper,
			  cache_entry.computer_name));
	} else {

		DEBUG(3,("%s: restored key %s for %s\n",
			 __func__, keystr, cache_entry.computer_name));

		*client_challenge = cache_entry.client_challenge;
		*server_challenge = cache_entry.server_challenge;
	}
 done:

	if (!NT_STATUS_IS_OK(status)) {
		return status;
	}

	return NT_STATUS_OK;
}

/******************************************************************************
 Wrapper around schannel_fetch_challenge_tdb()
 Note we must be root here.

*******************************************************************************/

NTSTATUS schannel_get_challenge(struct loadparm_context *lp_ctx,
				struct netr_Credential *client_challenge,
				struct netr_Credential *server_challenge,
				const char *computer_name)
{
	TALLOC_CTX *frame = talloc_stackframe();
	struct db_context *db_sc;
	NTSTATUS status;

	db_sc = open_schannel_session_store(frame, lp_ctx);
	if (!db_sc) {
		TALLOC_FREE(frame);
		return NT_STATUS_ACCESS_DENIED;
	}

	status = schannel_fetch_challenge_tdb(db_sc, frame,
					      client_challenge,
					      server_challenge,
					      computer_name);
	TALLOC_FREE(frame);
	return status;
}

/******************************************************************************
 Wrapper around dbwrap_delete_bystring()
 Note we must be root here.

 This allows the challenge to be removed from the TDB, which should be
 as soon as the TDB or in-memory copy it is used, to avoid reuse.
*******************************************************************************/

NTSTATUS schannel_delete_challenge(struct loadparm_context *lp_ctx,
				   const char *computer_name)
{
	TALLOC_CTX *frame = talloc_stackframe();
	struct db_context *db_sc;
	char *name_upper;
	char keystr[16] = { 0, };

	db_sc = open_schannel_session_store(frame, lp_ctx);
	if (!db_sc) {
		TALLOC_FREE(frame);
		return NT_STATUS_ACCESS_DENIED;
	}

	name_upper = strupper_talloc(frame, computer_name);
	if (!name_upper) {
		TALLOC_FREE(frame);
		return NT_STATUS_NO_MEMORY;
	}

	hash_computer_name(name_upper, keystr);

	/* Now delete it, we do not want to permit fetch of this twice */
	dbwrap_delete_bystring(db_sc, keystr);

	TALLOC_FREE(frame);
	return NT_STATUS_OK;
}

/******************************************************************************
 Wrapper around schannel_store_session_key_tdb()
 Note we must be root here.
*******************************************************************************/

NTSTATUS schannel_save_challenge(struct loadparm_context *lp_ctx,
				 const struct netr_Credential *client_challenge,
				 const struct netr_Credential *server_challenge,
				 const char *computer_name)
{
	TALLOC_CTX *frame = talloc_stackframe();
	struct db_context *db_sc;
	NTSTATUS status;

	db_sc = open_schannel_session_store(frame, lp_ctx);
	if (!db_sc) {
		TALLOC_FREE(frame);
		return NT_STATUS_ACCESS_DENIED;
	}

	status = schannel_store_challenge_tdb(db_sc, frame,
					      client_challenge,
					      server_challenge,
					      computer_name);

	TALLOC_FREE(frame);
	return status;
}

/********************************************************************
 Validate an incoming authenticator against the credentials for the
 remote machine stored in the schannel database.

 The credentials are (re)read and from the schannel database, and
 written back after the caclulations are performed.

 If the creds_out parameter is not NULL returns the credentials.
 ********************************************************************/

NTSTATUS schannel_check_creds_state(TALLOC_CTX *mem_ctx,
				    struct loadparm_context *lp_ctx,
				    const char *computer_name,
				    struct netr_Authenticator *received_authenticator,
				    struct netr_Authenticator *return_authenticator,
				    struct netlogon_creds_CredentialState **creds_out)
{
	TALLOC_CTX *tmpctx;
	struct db_context *db_sc;
	struct netlogon_creds_CredentialState *creds;
	NTSTATUS status;
	char *name_upper = NULL;
	char *keystr = NULL;
	struct db_record *record;
	TDB_DATA key;

	if (creds_out != NULL) {
		*creds_out = NULL;
	}

	tmpctx = talloc_named(mem_ctx, 0, "schannel_check_creds_state");
	if (!tmpctx) {
		return NT_STATUS_NO_MEMORY;
	}

	name_upper = strupper_talloc(tmpctx, computer_name);
	if (!name_upper) {
		status = NT_STATUS_NO_MEMORY;
		goto done;
	}

	keystr = talloc_asprintf(tmpctx, "%s/%s",
				 SECRETS_SCHANNEL_STATE, name_upper);
	if (!keystr) {
		status = NT_STATUS_NO_MEMORY;
		goto done;
	}

	key = string_term_tdb_data(keystr);

	db_sc = open_schannel_session_store(tmpctx, lp_ctx);
	if (!db_sc) {
		status = NT_STATUS_ACCESS_DENIED;
		goto done;
	}

	record = dbwrap_fetch_locked(db_sc, tmpctx, key);
	if (!record) {
		status = NT_STATUS_INTERNAL_DB_CORRUPTION;
		goto done;
	}

	/* Because this is a shared structure (even across
	 * disconnects) we must update the database every time we
	 * update the structure */

	status = schannel_fetch_session_key_tdb(db_sc, tmpctx,
						computer_name, &creds);
	if (!NT_STATUS_IS_OK(status)) {
		goto done;
	}

	status = netlogon_creds_server_step_check(creds,
						  received_authenticator,
						  return_authenticator);
	if (!NT_STATUS_IS_OK(status)) {
		goto done;
	}

	status = schannel_store_session_key_tdb(db_sc, tmpctx, creds);
	if (!NT_STATUS_IS_OK(status)) {
		goto done;
	}

	if (creds_out) {
		*creds_out = talloc_steal(mem_ctx, creds);
		if (!*creds_out) {
			status = NT_STATUS_NO_MEMORY;
			goto done;
		}
	}

	status = NT_STATUS_OK;

done:
	talloc_free(tmpctx);
	return status;
}