s4 dns: Handle GSS-TSIG signatures

5 files changed, 352 insertions, 59 deletions

diff --git a/source4/dns_server/dns_crypto.c b/source4/dns_server/dns_crypto.c
new file mode 100644
index 0000000000..ab422221c0
--- /dev/null
+++ b/source4/dns_server/dns_crypto.c
@@ -0,0 +1,269 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   DNS server handler for signed packets
+
+   Copyright (C) 2012 Kai Blin  <kai@samba.org>
+
+   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 "lib/crypto/hmacmd5.h"
+#include "system/network.h"
+#include "librpc/ndr/libndr.h"
+#include "librpc/gen_ndr/ndr_dns.h"
+#include "dns_server/dns_server.h"
+#include "libcli/util/ntstatus.h"
+#include "auth/auth.h"
+#include "auth/gensec/gensec.h"
+
+static WERROR dns_copy_tsig(TALLOC_CTX *mem_ctx,
+			    struct dns_res_rec *old,
+			    struct dns_res_rec *new_rec)
+{
+	new_rec->name = talloc_strdup(mem_ctx, old->name);
+	W_ERROR_HAVE_NO_MEMORY(new_rec->name);
+
+	new_rec->rr_type = old->rr_type;
+	new_rec->rr_class = old->rr_class;
+	new_rec->ttl = old->ttl;
+	new_rec->length = old->length;
+	new_rec->rdata.tsig_record.algorithm_name = talloc_strdup(mem_ctx,
+				old->rdata.tsig_record.algorithm_name);
+	W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.algorithm_name);
+
+	new_rec->rdata.tsig_record.time_prefix = old->rdata.tsig_record.time_prefix;
+	new_rec->rdata.tsig_record.time = old->rdata.tsig_record.time;
+	new_rec->rdata.tsig_record.fudge = old->rdata.tsig_record.fudge;
+	new_rec->rdata.tsig_record.mac_size = old->rdata.tsig_record.mac_size;
+	new_rec->rdata.tsig_record.mac = talloc_memdup(mem_ctx,
+					old->rdata.tsig_record.mac,
+					old->rdata.tsig_record.mac_size);
+	W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.mac);
+
+	new_rec->rdata.tsig_record.original_id = old->rdata.tsig_record.original_id;
+	new_rec->rdata.tsig_record.error = old->rdata.tsig_record.error;
+	new_rec->rdata.tsig_record.other_size = old->rdata.tsig_record.other_size;
+	new_rec->rdata.tsig_record.other_data = talloc_memdup(mem_ctx,
+					old->rdata.tsig_record.other_data,
+					old->rdata.tsig_record.other_size);
+	W_ERROR_HAVE_NO_MEMORY(new_rec->rdata.tsig_record.other_data);
+
+	return WERR_OK;
+}
+
+struct dns_server_tkey *dns_find_tkey(struct dns_server_tkey_store *store,
+				      const char *name)
+{
+	struct dns_server_tkey *tkey = NULL;
+	uint16_t i = 0;
+
+	do {
+		struct dns_server_tkey *tmp_key = store->tkeys[i];
+
+		i++;
+		i %= TKEY_BUFFER_SIZE;
+
+		if (tmp_key == NULL) {
+			continue;
+		}
+		if (dns_name_equal(name, tmp_key->name)) {
+			tkey = tmp_key;
+			break;
+		}
+	} while (i != 0);
+
+	return tkey;
+}
+
+WERROR dns_verify_tsig(struct dns_server *dns,
+		       struct dns_request_state *state,
+		       struct dns_name_packet *packet)
+{
+	WERROR werror;
+	bool found_tsig = false;
+	uint16_t i, mac_length = 0;
+	struct dns_server_tkey *tkey = NULL;
+	uint8_t *mac = NULL;
+
+	/* Find the first TSIG record in the additional records */
+	for (i=0; i < packet->arcount; i++) {
+		if (packet->additional[i].rr_type == DNS_QTYPE_TSIG) {
+			found_tsig = true;
+			break;
+		}
+	}
+
+	if (!found_tsig) {
+		return WERR_OK;
+	}
+
+	/* The TSIG record needs to be the last additional record */
+	if (found_tsig && i + 1 != packet->arcount) {
+		DEBUG(0, ("TSIG record not the last additional record!\n"));
+		return DNS_ERR(FORMAT_ERROR);
+	}
+
+	/* We got a TSIG, so we need to sign our reply */
+	state->sign = true;
+
+	state->tsig = talloc_zero(state, struct dns_res_rec);
+	W_ERROR_HAVE_NO_MEMORY(state->tsig);
+
+	werror = dns_copy_tsig(state->tsig, &packet->additional[i],
+			       state->tsig);
+	W_ERROR_NOT_OK_RETURN(werror);
+
+	packet->arcount--;
+
+	tkey = dns_find_tkey(dns->tkeys, state->tsig->name);
+	if (tkey == NULL) {
+		state->tsig_error = DNS_RCODE_BADKEY;
+		return DNS_ERR(NOTAUTH);
+	}
+
+	/* FIXME: check TSIG here */
+
+	dump_data(1, mac, mac_length);
+	state->tsig_error = DNS_RCODE_BADKEY;
+	return DNS_ERR(NOTAUTH);
+}
+
+WERROR dns_sign_tsig(struct dns_server *dns,
+		     TALLOC_CTX *mem_ctx,
+		     struct dns_request_state *state,
+		     struct dns_name_packet *packet,
+		     uint16_t error)
+{
+	WERROR werror;
+	NTSTATUS status;
+	enum ndr_err_code ndr_err;
+	time_t current_time = time(NULL);
+	DATA_BLOB packet_blob, tsig_blob, sig;
+	uint8_t *buffer = NULL;
+	size_t buffer_len = 0;
+	struct dns_server_tkey * tkey = NULL;
+	struct dns_res_rec *tsig = talloc_zero(mem_ctx, struct dns_res_rec);
+
+	struct dns_fake_tsig_rec *check_rec = talloc_zero(mem_ctx,
+			struct dns_fake_tsig_rec);
+
+	if (tsig == NULL) {
+		return WERR_NOMEM;
+	}
+
+	if (check_rec == NULL) {
+		return WERR_NOMEM;
+	}
+
+	tkey = dns_find_tkey(dns->tkeys, state->key_name);
+	if (tkey == NULL) {
+		/* FIXME: read up on what to do when we can't find a key */
+		return WERR_OK;
+	}
+
+	/* first build and verify check packet */
+	check_rec->name = talloc_strdup(check_rec, tkey->name);
+	if (check_rec->name == NULL) {
+		return WERR_NOMEM;
+	}
+	check_rec->rr_class = DNS_QCLASS_ANY;
+	check_rec->ttl = 0;
+	check_rec->algorithm_name = talloc_strdup(check_rec, tkey->algorithm);
+	if (check_rec->algorithm_name == NULL) {
+		return WERR_NOMEM;
+	}
+	check_rec->time_prefix = 0;
+	check_rec->time = current_time;
+	check_rec->fudge = 300;
+	check_rec->error = state->tsig_error;
+	check_rec->other_size = 0;
+	check_rec->other_data = NULL;
+
+	ndr_err = ndr_push_struct_blob(&packet_blob, mem_ctx, packet,
+		(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		DEBUG(1, ("Failed to push packet: %s!\n",
+			  ndr_errstr(ndr_err)));
+		return DNS_ERR(SERVER_FAILURE);
+	}
+
+	ndr_err = ndr_push_struct_blob(&tsig_blob, mem_ctx, check_rec,
+		(ndr_push_flags_fn_t)ndr_push_dns_fake_tsig_rec);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		DEBUG(1, ("Failed to push packet: %s!\n",
+			  ndr_errstr(ndr_err)));
+		return DNS_ERR(SERVER_FAILURE);
+	}
+
+	buffer_len = packet_blob.length + tsig_blob.length;
+	buffer = talloc_zero_array(mem_ctx, uint8_t, buffer_len);
+	if (buffer == NULL) {
+		return WERR_NOMEM;
+	}
+
+	memcpy(buffer, packet_blob.data, packet_blob.length);
+	memcpy(buffer, tsig_blob.data, tsig_blob.length);
+
+
+	status = gensec_sign_packet(tkey->gensec, mem_ctx, buffer, buffer_len,
+				    buffer, buffer_len, &sig);
+	if (!NT_STATUS_IS_OK(status)) {
+		return ntstatus_to_werror(status);
+	}
+
+	tsig->name = talloc_strdup(tsig, check_rec->name);
+	if (tsig->name == NULL) {
+		return WERR_NOMEM;
+	}
+	tsig->rr_class = check_rec->rr_class;
+	tsig->rr_type = DNS_QTYPE_TSIG;
+	tsig->ttl = 0;
+	tsig->length = UINT16_MAX;
+	tsig->rdata.tsig_record.algorithm_name = talloc_strdup(tsig,
+			check_rec->algorithm_name);
+	tsig->rdata.tsig_record.time_prefix = check_rec->time_prefix;
+	tsig->rdata.tsig_record.time = check_rec->time;
+	tsig->rdata.tsig_record.fudge = check_rec->fudge;
+	tsig->rdata.tsig_record.error = state->tsig_error;
+	tsig->rdata.tsig_record.original_id = packet->id;
+	tsig->rdata.tsig_record.other_size = 0;
+	tsig->rdata.tsig_record.other_data = NULL;
+	tsig->rdata.tsig_record.mac_size = sig.length;
+	tsig->rdata.tsig_record.mac = talloc_memdup(tsig, sig.data, sig.length);
+
+
+	if (packet->arcount == 0) {
+		packet->additional = talloc_zero(mem_ctx, struct dns_res_rec);
+		if (packet->additional == NULL) {
+			return WERR_NOMEM;
+		}
+	}
+	packet->additional = talloc_realloc(mem_ctx, packet->additional,
+					    struct dns_res_rec,
+					    packet->arcount + 1);
+	if (packet->additional == NULL) {
+		return WERR_NOMEM;
+	}
+
+	werror = dns_copy_tsig(mem_ctx, tsig,
+			       &packet->additional[packet->arcount]);
+	if (!W_ERROR_IS_OK(werror)) {
+		return werror;
+	}
+	packet->arcount++;
+
+	return WERR_OK;
+}
diff --git a/source4/dns_server/dns_query.c b/source4/dns_server/dns_query.c
index 530b7b22bd..98ebc63d97 100644
--- a/source4/dns_server/dns_query.c
+++ b/source4/dns_server/dns_query.c
@@ -320,62 +320,9 @@ static WERROR handle_question(struct dns_server *dns,
 	return WERR_OK;
 }
 
-static NTSTATUS accept_gss_ticket(TALLOC_CTX *mem_ctx,
-				  struct dns_server *dns,
-				  struct dns_server_tkey *tkey,
-				  const DATA_BLOB *key,
-				  DATA_BLOB *reply,
-				  uint16_t *dns_auth_error)
-{
-	NTSTATUS status;
-
-	status = gensec_update(tkey->gensec, mem_ctx, dns->task->event_ctx,
-			       *key, reply);
-
-	if (NT_STATUS_EQUAL(NT_STATUS_MORE_PROCESSING_REQUIRED, status)) {
-		*dns_auth_error = DNS_RCODE_OK;
-		return status;
-	}
-
-	if (NT_STATUS_IS_OK(status)) {
-
-		status = gensec_session_info(tkey->gensec, tkey, &tkey->session_info);
-		if (!NT_STATUS_IS_OK(status)) {
-			*dns_auth_error = DNS_RCODE_BADKEY;
-			return status;
-		}
-		*dns_auth_error = DNS_RCODE_OK;
-	}
-
-	return status;
-}
-
-static struct dns_server_tkey *find_tkey(struct dns_server_tkey_store *store,
-					 const char *name)
-{
-	struct dns_server_tkey *tkey = NULL;
-	uint16_t i = 0;
-
-	do {
-		struct dns_server_tkey *tmp_key = store->tkeys[i];
-
-		i++;
-		i %= TKEY_BUFFER_SIZE;
-
-		if (tmp_key == NULL) {
-			continue;
-		}
-		if (dns_name_equal(name, tmp_key->name)) {
-			tkey = tmp_key;
-			break;
-		}
-	} while (i != 0);
-
-	return tkey;
-}
-
 static NTSTATUS create_tkey(struct dns_server *dns,
 			    const char* name,
+			    const char* algorithm,
 			    struct dns_server_tkey **tkey)
 {
 	NTSTATUS status;
@@ -392,6 +339,11 @@ static NTSTATUS create_tkey(struct dns_server *dns,
 		return NT_STATUS_NO_MEMORY;
 	}
 
+	k->algorithm = talloc_strdup(k, algorithm);
+	if (k->algorithm == NULL) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
 	status = samba_server_gensec_start(k,
 					   dns->task->event_ctx,
 					   dns->task->msg_ctx,
@@ -428,9 +380,40 @@ static NTSTATUS create_tkey(struct dns_server *dns,
 	return NT_STATUS_OK;
 }
 
+static NTSTATUS accept_gss_ticket(TALLOC_CTX *mem_ctx,
+				  struct dns_server *dns,
+				  struct dns_server_tkey *tkey,
+				  const DATA_BLOB *key,
+				  DATA_BLOB *reply,
+				  uint16_t *dns_auth_error)
+{
+	NTSTATUS status;
+
+	status = gensec_update(tkey->gensec, mem_ctx, dns->task->event_ctx,
+			       *key, reply);
+
+	if (NT_STATUS_EQUAL(NT_STATUS_MORE_PROCESSING_REQUIRED, status)) {
+		*dns_auth_error = DNS_RCODE_OK;
+		return status;
+	}
+
+	if (NT_STATUS_IS_OK(status)) {
+
+		status = gensec_session_info(tkey->gensec, tkey, &tkey->session_info);
+		if (!NT_STATUS_IS_OK(status)) {
+			*dns_auth_error = DNS_RCODE_BADKEY;
+			return status;
+		}
+		*dns_auth_error = DNS_RCODE_OK;
+	}
+
+	return status;
+}
+
 static WERROR handle_tkey(struct dns_server *dns,
                           TALLOC_CTX *mem_ctx,
                           const struct dns_name_packet *in,
+			  struct dns_request_state *state,
                           struct dns_res_rec **answers,
                           uint16_t *ancount)
 {
@@ -466,7 +449,8 @@ static WERROR handle_tkey(struct dns_server *dns,
 	ret_tkey->rr_class = DNS_QCLASS_ANY;
 	ret_tkey->length = UINT16_MAX;
 
-	ret_tkey->rdata.tkey_record.algorithm = talloc_strdup(ret_tkey, ret_tkey->name);
+	ret_tkey->rdata.tkey_record.algorithm = talloc_strdup(ret_tkey,
+			in_tkey->rdata.tkey_record.algorithm);
 	if (ret_tkey->rdata.tkey_record.algorithm  == NULL) {
 		return WERR_NOMEM;
 	}
@@ -487,7 +471,7 @@ static WERROR handle_tkey(struct dns_server *dns,
 		DATA_BLOB key;
 		DATA_BLOB reply;
 
-		tkey = find_tkey(dns->tkeys, in->questions[0].name);
+		tkey = dns_find_tkey(dns->tkeys, in->questions[0].name);
 		if (tkey != NULL && tkey->complete) {
 			/* TODO: check if the key is still valid */
 			DEBUG(1, ("Rejecting tkey negotiation for already established key\n"));
@@ -497,6 +481,7 @@ static WERROR handle_tkey(struct dns_server *dns,
 
 		if (tkey == NULL) {
 			status  = create_tkey(dns, in->questions[0].name,
+					      in_tkey->rdata.tkey_record.algorithm,
 					      &tkey);
 			if (!NT_STATUS_IS_OK(status)) {
 				ret_tkey->rdata.tkey_record.error = DNS_RCODE_BADKEY;
@@ -514,6 +499,15 @@ static WERROR handle_tkey(struct dns_server *dns,
 			ret_tkey->rdata.tkey_record.error = DNS_RCODE_BADKEY;
 		} else if (NT_STATUS_IS_OK(status)) {
 			DEBUG(1, ("Tkey handshake completed\n"));
+			ret_tkey->rdata.tkey_record.key_size = reply.length;
+			ret_tkey->rdata.tkey_record.key_data = talloc_memdup(ret_tkey,
+								reply.data,
+								reply.length);
+			state->sign = true;
+			state->key_name = talloc_strdup(mem_ctx, tkey->name);
+			if (state->key_name == NULL) {
+				return WERR_NOMEM;
+			}
 		} else {
 			DEBUG(0, ("GSS key negotiation returned %s\n", nt_errstr(status)));
 			ret_tkey->rdata.tkey_record.error = DNS_RCODE_BADKEY;
@@ -582,8 +576,8 @@ struct tevent_req *dns_server_process_query_send(
 	if (in->questions[0].question_type == DNS_QTYPE_TKEY) {
                 WERROR err;
 
-		err = handle_tkey(dns, state, in, &state->answers,
-				  &state->ancount);
+		err = handle_tkey(dns, state, in, req_state,
+				  &state->answers, &state->ancount);
 		if (tevent_req_werror(req, err)) {
 			return tevent_req_post(req, ev);
 		}
diff --git a/source4/dns_server/dns_server.c b/source4/dns_server/dns_server.c
index 887fc8ee1d..cd121f9d8b 100644
--- a/source4/dns_server/dns_server.c
+++ b/source4/dns_server/dns_server.c
@@ -98,6 +98,7 @@ static void dns_tcp_send(struct stream_connection *conn, uint16_t flags)
 
 struct dns_process_state {
 	DATA_BLOB *in;
+	struct dns_server *dns;
 	struct dns_name_packet in_packet;
 	struct dns_request_state state;
 	uint16_t dns_err;
@@ -123,6 +124,8 @@ static struct tevent_req *dns_process_send(TALLOC_CTX *mem_ctx,
 	}
 	state->in = in;
 
+	state->dns = dns;
+
 	if (in->length < 12) {
 		tevent_req_werror(req, WERR_INVALID_PARAM);
 		return tevent_req_post(req, ev);
@@ -142,6 +145,8 @@ static struct tevent_req *dns_process_send(TALLOC_CTX *mem_ctx,
 		NDR_PRINT_DEBUG(dns_name_packet, &state->in_packet);
 	}
 
+	ret = dns_verify_tsig(dns, &state->state, &state->in_packet);
+
 	state->state.flags = state->in_packet.operation;
 	state->state.flags |= DNS_FLAG_REPLY;
 
@@ -215,6 +220,15 @@ static WERROR dns_process_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
 	}
 	state->out_packet.operation |= state->state.flags;
 
+	if (state->state.sign) {
+		ret = dns_sign_tsig(state->dns, mem_ctx, &state->state,
+				    &state->out_packet, 0);
+		if (!W_ERROR_IS_OK(ret)) {
+			state->dns_err = DNS_RCODE_SERVFAIL;
+			goto drop;
+		}
+	}
+
 	ndr_err = ndr_push_struct_blob(
 		out, mem_ctx, &state->out_packet,
 		(ndr_push_flags_fn_t)ndr_push_dns_name_packet);
diff --git a/source4/dns_server/dns_server.h b/source4/dns_server/dns_server.h
index 42ae0ba660..6cd60267c0 100644
--- a/source4/dns_server/dns_server.h
+++ b/source4/dns_server/dns_server.h
@@ -36,6 +36,7 @@ struct dns_server_zone {
 struct dns_server_tkey {
 	const char *name;
 	enum dns_tkey_mode mode;
+	const char *algorithm;
 	struct auth_session_info *session_info;
 	struct gensec_security *gensec;
 	bool complete;
@@ -59,6 +60,11 @@ struct dns_server {
 
 struct dns_request_state {
 	uint16_t flags;
+	bool authenticated;
+	bool sign;
+	char *key_name;
+	struct dns_res_rec *tsig;
+	uint16_t tsig_error;
 };
 
 struct tevent_req *dns_server_process_query_send(
@@ -101,6 +107,16 @@ WERROR dns_name2dn(struct dns_server *dns,
 		   TALLOC_CTX *mem_ctx,
 		   const char *name,
 		   struct ldb_dn **_dn);
+struct dns_server_tkey *dns_find_tkey(struct dns_server_tkey_store *store,
+				      const char *name);
+WERROR dns_verify_tsig(struct dns_server *dns,
+		       struct dns_request_state *state,
+		       struct dns_name_packet *packet);
+WERROR dns_sign_tsig(struct dns_server *dns,
+		     TALLOC_CTX *mem_ctx,
+		     struct dns_request_state *state,
+		     struct dns_name_packet *packet,
+		     uint16_t error);
 
 #define DNS_ERR(err_str) WERR_DNS_ERROR_RCODE_##err_str
 #endif /* __DNS_SERVER_H__ */
diff --git a/source4/dns_server/wscript_build b/source4/dns_server/wscript_build
index 8cb23ee938..6989f2567b 100644
--- a/source4/dns_server/wscript_build
+++ b/source4/dns_server/wscript_build
@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 
 bld.SAMBA_MODULE('service_dns',
-        source='dns_server.c dns_query.c dns_update.c dns_utils.c',
+        source='dns_server.c dns_query.c dns_update.c dns_utils.c dns_crypto.c',
         subsystem='service',
         init_function='server_service_dns_init',
         deps='samba-hostconfig LIBTSOCKET LIBSAMBA_TSOCKET ldbsamba clidns gensec auth',