gensec_krb5.c

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/* 
   Unix SMB/CIFS implementation.

   Kerberos backend for GENSEC
   
   Copyright (C) Andrew Bartlett <[e-mail]> 2004
   Copyright (C) Andrew Tridgell 2001
   Copyright (C) Luke Howard 2002-2003
   Copyright (C) Stefan Metzmacher 2004-2005

   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/kerberos.h"
#include "auth/kerberos/kerberos.h"
#include "librpc/gen_ndr/krb5pac.h"
#include "auth/auth.h"
#include "lib/ldb/include/ldb.h"
#include "auth/auth_sam.h"
#include "system/network.h"
#include "lib/socket/socket.h"
#include "librpc/rpc/dcerpc.h"
#include "auth/credentials/credentials.h"
#include "auth/credentials/credentials_krb5.h"
#include "auth/gensec/gensec.h"
#include "auth/gensec/gensec_proto.h"
#include "param/param.h"
#include "auth/session_proto.h"

enum GENSEC_KRB5_STATE {
	GENSEC_KRB5_SERVER_START,
	GENSEC_KRB5_CLIENT_START,
	GENSEC_KRB5_CLIENT_MUTUAL_AUTH,
	GENSEC_KRB5_DONE
};

struct gensec_krb5_state {
	DATA_BLOB session_key;
	DATA_BLOB pac;
	enum GENSEC_KRB5_STATE state_position;
	struct smb_krb5_context *smb_krb5_context;
	krb5_auth_context auth_context;
	krb5_data enc_ticket;
	krb5_keyblock *keyblock;
	krb5_ticket *ticket;
	bool gssapi;
};

static int gensec_krb5_destroy(struct gensec_krb5_state *gensec_krb5_state)
{
	if (!gensec_krb5_state->smb_krb5_context) {
		/* We can't clean anything else up unless we started up this far */
		return 0;
	}
	if (gensec_krb5_state->enc_ticket.length) { 
		kerberos_free_data_contents(gensec_krb5_state->smb_krb5_context->krb5_context, 
					    &gensec_krb5_state->enc_ticket); 
	}

	if (gensec_krb5_state->ticket) {
		krb5_free_ticket(gensec_krb5_state->smb_krb5_context->krb5_context, 
				 gensec_krb5_state->ticket);
	}

	/* ccache freed in a child destructor */

	krb5_free_keyblock(gensec_krb5_state->smb_krb5_context->krb5_context, 
			   gensec_krb5_state->keyblock);
		
	if (gensec_krb5_state->auth_context) {
		krb5_auth_con_free(gensec_krb5_state->smb_krb5_context->krb5_context, 
				   gensec_krb5_state->auth_context);
	}

	return 0;
}

static NTSTATUS gensec_krb5_start(struct gensec_security *gensec_security)
{
	krb5_error_code ret;
	struct gensec_krb5_state *gensec_krb5_state;
	struct cli_credentials *creds;
	const struct socket_address *my_addr, *peer_addr;
	krb5_address my_krb5_addr, peer_krb5_addr;
	
	creds = gensec_get_credentials(gensec_security);
	if (!creds) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	gensec_krb5_state = talloc(gensec_security, struct gensec_krb5_state);
	if (!gensec_krb5_state) {
		return NT_STATUS_NO_MEMORY;
	}

	gensec_security->private_data = gensec_krb5_state;
	gensec_krb5_state->smb_krb5_context = NULL;
	gensec_krb5_state->auth_context = NULL;
	gensec_krb5_state->ticket = NULL;
	ZERO_STRUCT(gensec_krb5_state->enc_ticket);
	gensec_krb5_state->keyblock = NULL;
	gensec_krb5_state->session_key = data_blob(NULL, 0);
	gensec_krb5_state->pac = data_blob(NULL, 0);
	gensec_krb5_state->gssapi = false;

	talloc_set_destructor(gensec_krb5_state, gensec_krb5_destroy); 

	if (cli_credentials_get_krb5_context(creds, 
					     gensec_security->event_ctx, 
					     gensec_security->lp_ctx, &gensec_krb5_state->smb_krb5_context)) {
		talloc_free(gensec_krb5_state);
		return NT_STATUS_INTERNAL_ERROR;
	}

	ret = krb5_auth_con_init(gensec_krb5_state->smb_krb5_context->krb5_context, &gensec_krb5_state->auth_context);
	if (ret) {
		DEBUG(1,("gensec_krb5_start: krb5_auth_con_init failed (%s)\n", 
			 smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, 
						    ret, gensec_krb5_state)));
		talloc_free(gensec_krb5_state);
		return NT_STATUS_INTERNAL_ERROR;
	}

	ret = krb5_auth_con_setflags(gensec_krb5_state->smb_krb5_context->krb5_context, 
				     gensec_krb5_state->auth_context,
				     KRB5_AUTH_CONTEXT_DO_SEQUENCE);
	if (ret) {
		DEBUG(1,("gensec_krb5_start: krb5_auth_con_setflags failed (%s)\n", 
			 smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, 
						    ret, gensec_krb5_state)));
		talloc_free(gensec_krb5_state);
		return NT_STATUS_INTERNAL_ERROR;
	}

	my_addr = gensec_get_my_addr(gensec_security);
	if (my_addr && my_addr->sockaddr) {
		ret = krb5_sockaddr2address(gensec_krb5_state->smb_krb5_context->krb5_context, 
					    my_addr->sockaddr, &my_krb5_addr);
		if (ret) {
			DEBUG(1,("gensec_krb5_start: krb5_sockaddr2address (local) failed (%s)\n", 
				 smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, 
							    ret, gensec_krb5_state)));
			talloc_free(gensec_krb5_state);
			return NT_STATUS_INTERNAL_ERROR;
		}
	}

	peer_addr = gensec_get_peer_addr(gensec_security);
	if (peer_addr && peer_addr->sockaddr) {
		ret = krb5_sockaddr2address(gensec_krb5_state->smb_krb5_context->krb5_context, 
					    peer_addr->sockaddr, &peer_krb5_addr);
		if (ret) {
			DEBUG(1,("gensec_krb5_start: krb5_sockaddr2address (local) failed (%s)\n", 
				 smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, 
							    ret, gensec_krb5_state)));
			talloc_free(gensec_krb5_state);
			return NT_STATUS_INTERNAL_ERROR;
		}
	}

	ret = krb5_auth_con_setaddrs(gensec_krb5_state->smb_krb5_context->krb5_context, 
				     gensec_krb5_state->auth_context,
				     my_addr ? &my_krb5_addr : NULL, 
				     peer_addr ? &peer_krb5_addr : NULL);
	if (ret) {
		DEBUG(1,("gensec_krb5_start: krb5_auth_con_setaddrs failed (%s)\n", 
			 smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, 
						    ret, gensec_krb5_state)));
		talloc_free(gensec_krb5_state);
		return NT_STATUS_INTERNAL_ERROR;
	}

	return NT_STATUS_OK;
}

static NTSTATUS gensec_krb5_server_start(struct gensec_security *gensec_security)
{
	NTSTATUS nt_status;
	struct gensec_krb5_state *gensec_krb5_state;

	nt_status = gensec_krb5_start(gensec_security);
	if (!NT_STATUS_IS_OK(nt_status)) {
		return nt_status;
	}
	
	gensec_krb5_state = (struct gensec_krb5_state *)gensec_security->private_data;
	gensec_krb5_state->state_position = GENSEC_KRB5_SERVER_START;

	return NT_STATUS_OK;
}

static NTSTATUS gensec_fake_gssapi_krb5_server_start(struct gensec_security *gensec_security)
{
	NTSTATUS nt_status = gensec_krb5_server_start(gensec_security);

	if (NT_STATUS_IS_OK(nt_status)) {
		struct gensec_krb5_state *gensec_krb5_state;
		gensec_krb5_state = (struct gensec_krb5_state *)gensec_security->private_data;
		gensec_krb5_state->gssapi = true;
	}
	return nt_status;
}

static NTSTATUS gensec_krb5_client_start(struct gensec_security *gensec_security)
{
	struct gensec_krb5_state *gensec_krb5_state;
	krb5_error_code ret;
	NTSTATUS nt_status;
	struct ccache_container *ccache_container;
	const char *hostname;
	krb5_flags ap_req_options = AP_OPTS_USE_SUBKEY | AP_OPTS_MUTUAL_REQUIRED;

	const char *principal;
	krb5_data in_data;

	hostname = gensec_get_target_hostname(gensec_security);
	if (!hostname) {
		DEBUG(1, ("Could not determine hostname for target computer, cannot use kerberos\n"));
		return NT_STATUS_INVALID_PARAMETER;
	}
	if (is_ipaddress(hostname)) {
		DEBUG(2, ("Cannot do krb5 to an IP address"));
		return NT_STATUS_INVALID_PARAMETER;
	}
	if (strcmp(hostname, "localhost") == 0) {
		DEBUG(2, ("krb5 to 'localhost' does not make sense"));
		return NT_STATUS_INVALID_PARAMETER;
	}
			
	nt_status = gensec_krb5_start(gensec_security);
	if (!NT_STATUS_IS_OK(nt_status)) {
		return nt_status;
	}

	gensec_krb5_state = (struct gensec_krb5_state *)gensec_security->private_data;
	gensec_krb5_state->state_position = GENSEC_KRB5_CLIENT_START;

	principal = gensec_get_target_principal(gensec_security);

	ret = cli_credentials_get_ccache(gensec_get_credentials(gensec_security), 
				         gensec_security->event_ctx, 
					 gensec_security->lp_ctx, &ccache_container);
	switch (ret) {
	case 0:
		break;
	case KRB5KDC_ERR_PREAUTH_FAILED:
		return NT_STATUS_LOGON_FAILURE;
	case KRB5_KDC_UNREACH:
		DEBUG(3, ("Cannot reach a KDC we require to contact %s\n", principal));
		return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
	default:
		DEBUG(1, ("gensec_krb5_start: Aquiring initiator credentials failed: %s\n", error_message(ret)));
		return NT_STATUS_UNSUCCESSFUL;
	}
	in_data.length = 0;
	
	if (principal && lp_client_use_spnego_principal(gensec_security->lp_ctx)) {
		krb5_principal target_principal;
		ret = krb5_parse_name(gensec_krb5_state->smb_krb5_context->krb5_context, principal,
				      &target_principal);
		if (ret == 0) {
			ret = krb5_mk_req_exact(gensec_krb5_state->smb_krb5_context->krb5_context, 
						&gensec_krb5_state->auth_context,
						ap_req_options, 
						target_principal,
						&in_data, ccache_container->ccache, 
						&gensec_krb5_state->enc_ticket);
			krb5_free_principal(gensec_krb5_state->smb_krb5_context->krb5_context, 
					    target_principal);
		}
	} else {
		ret = krb5_mk_req(gensec_krb5_state->smb_krb5_context->krb5_context, 
				  &gensec_krb5_state->auth_context,
				  ap_req_options,
				  gensec_get_target_service(gensec_security),
				  hostname,
				  &in_data, ccache_container->ccache, 
				  &gensec_krb5_state->enc_ticket);
	}
	switch (ret) {
	case 0:
		return NT_STATUS_OK;
	case KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN:
		DEBUG(3, ("Server [%s] is not registered with our KDC: %s\n", 
			  hostname, smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, ret, gensec_krb5_state)));
		return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
	case KRB5_KDC_UNREACH:
		DEBUG(3, ("Cannot reach a KDC we require to contact host [%s]: %s\n",
			  hostname, smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, ret, gensec_krb5_state)));
		return NT_STATUS_INVALID_PARAMETER; /* Make SPNEGO ignore us, we can't go any further here */
	case KRB5KDC_ERR_PREAUTH_FAILED:
	case KRB5KRB_AP_ERR_TKT_EXPIRED:
	case KRB5_CC_END:
		/* Too much clock skew - we will need to kinit to re-skew the clock */
	case KRB5KRB_AP_ERR_SKEW:
	case KRB5_KDCREP_SKEW:
	{
		DEBUG(3, ("kerberos (mk_req) failed: %s\n", 
			  smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, ret, gensec_krb5_state)));
		/*fall through*/
	}
	
	/* just don't print a message for these really ordinary messages */
	case KRB5_FCC_NOFILE:
	case KRB5_CC_NOTFOUND:
	case ENOENT:
		
		return NT_STATUS_UNSUCCESSFUL;
		break;
		
	default:
		DEBUG(0, ("kerberos: %s\n", 
			  smb_get_krb5_error_message(gensec_krb5_state->smb_krb5_context->krb5_context, ret, gensec_krb5_state)));
		return NT_STATUS_UNSUCCESSFUL;
	}
}

static NTSTATUS gensec_fake_gssapi_krb5_client_start(struct gensec_security *gensec_security)
{
	NTSTATUS nt_status = gensec_krb5_client_start(gensec_security);

	if (NT_STATUS_IS_OK(nt_status)) {
		struct gensec_krb5_state *gensec_krb5_state;
		gensec_krb5_state = (struct gensec_krb5_state *)gensec_security->private_data;
		gensec_krb5_state->gssapi = true;
	}
	return nt_status;
}

/**
 * Check if the packet is one for this mechansim
 * 
 * @param gensec_security GENSEC state
 * @param in The request, as a DATA_BLOB
 * @return Error, INVALID_PARAMETER if it's not a packet for us
 *                or NT_STATUS_OK if the packet is ok. 
 */

static NTSTATUS gensec_fake_gssapi_krb5_magic(struct gensec_security *gensec_security, 
				  const DATA_BLOB *in) 
{
	if (gensec_gssapi_check_oid(in, GENSEC_OID_KERBEROS5)) {
		return NT_STATUS_OK;
	} else {
		return NT_STATUS_INVALID_PARAMETER;
	}
}


/**
 * Next state function for the Krb5 GENSEC mechanism
 * 
 * @param gensec_krb5_state KRB5 State
 * @param out_mem_ctx The TALLOC_CTX for *out to be allocated on
 * @param in The request, as a DATA_BLOB
 * @param out The reply, as an talloc()ed DATA_BLOB, on *out_mem_ctx
 * @return Error, MORE_PROCESSING_REQUIRED if a reply is sent, 
 *                or NT_STATUS_OK if the user is authenticated. 
 */

static NTSTATUS gensec_krb5_update(struct gensec_security *gensec_security, 
				   TALLOC_CTX *out_mem_ctx, 
				   const DATA_BLOB in, DATA_BLOB *out) 
{
	struct gensec_krb5_state *gensec_krb5_state = (struct gensec_krb5_state *)gensec_security->private_data;
	krb5_error_code ret = 0;
	NTSTATUS nt_status;

	switch (gensec_krb5_state->state_position) {
	case GENSEC_KRB5_CLIENT_START:
	{
		DATA_BLOB unwrapped_out;
		
		if (gensec_krb5_state->gssapi) {
			unwrapped_out = data_blob_talloc(out_mem_ctx, gensec_krb5_state->enc_ticket.data, gensec_krb5_state->enc_ticket.length);
			
			/* wrap that up in a nice GSS-API wrapping */
			*out = gensec_gssapi_gen_krb5_wrap(out_mem_ctx, &unwrapped_out, TOK_ID_KRB_AP_REQ);
		} else {
			*out = data_blob_talloc(out_mem_ctx, gensec_krb5_state->enc_ticket.data, gensec_krb5_state->enc_ticket.length);
		}
		gensec_krb5_state->state_position = GENSEC_KRB5_CLIENT_MUTUAL_AUTH;
		nt_status = NT_STATUS_MORE_PROCESSING_REQUIRED;
		return nt_status;
	}
		
	case GENSEC_KRB5_CLIENT_MUTUAL_AUTH:
	{
		DATA_BLOB unwrapped_in;
		krb5_data inbuf;
		krb5_ap_rep_enc_part *repl = NULL;
		uint8_t tok_id[2];