s4-kdc: added proxying of kdc requests for RODCs

when we are an RODC and we get a request for a principal that we don't
have the right secrets for, we need to proxy the request to a
writeable DC. This happens for both TCP and UDP requests, for both
krb5 and kpasswd

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

Autobuild-User: Andrew Tridgell <tridge@samba.org>
Autobuild-Date: Fri Nov 12 08:03:20 UTC 2010 on sn-devel-104

1 files changed, 657 insertions, 0 deletions

diff --git a/source4/kdc/proxy.c b/source4/kdc/proxy.c
new file mode 100644
index 0000000000..3929a127ef
--- /dev/null
+++ b/source4/kdc/proxy.c
@@ -0,0 +1,657 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   KDC Server request proxying
+
+   Copyright (C) Andrew Tridgell	2010
+   Copyright (C) Andrew Bartlett        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 "smbd/process_model.h"
+#include "lib/tsocket/tsocket.h"
+#include "libcli/util/tstream.h"
+#include "system/network.h"
+#include "param/param.h"
+#include "lib/stream/packet.h"
+#include "kdc/kdc-glue.h"
+#include "ldb.h"
+#include "librpc/gen_ndr/drsblobs.h"
+#include "dsdb/schema/schema.h"
+#include "dsdb/common/proto.h"
+#include "libcli/composite/composite.h"
+#include "libcli/resolve/resolve.h"
+
+
+/*
+  get a list of our replication partners from repsFrom, returning it in *proxy_list
+ */
+static WERROR kdc_proxy_get_writeable_dcs(struct kdc_server *kdc, TALLOC_CTX *mem_ctx, char ***proxy_list)
+{
+	WERROR werr;
+	uint32_t count, i;
+	struct repsFromToBlob *reps;
+
+	werr = dsdb_loadreps(kdc->samdb, mem_ctx, ldb_get_default_basedn(kdc->samdb), "repsFrom", &reps, &count);
+	W_ERROR_NOT_OK_RETURN(werr);
+
+	if (count == 0) {
+		/* we don't have any DCs to replicate with. Very
+		   strange for a RODC */
+		DEBUG(1,(__location__ ": No replication sources for RODC in KDC proxy\n"));
+		talloc_free(reps);
+		return WERR_DS_DRA_NO_REPLICA;
+	}
+
+	(*proxy_list) = talloc_array(mem_ctx, char *, count+1);
+	W_ERROR_HAVE_NO_MEMORY_AND_FREE(*proxy_list, reps);
+
+	talloc_steal(*proxy_list, reps);
+
+	for (i=0; i<count; i++) {
+		const char *dns_name = NULL;
+		if (reps->version == 1) {
+			dns_name = reps->ctr.ctr1.other_info->dns_name;
+		} else if (reps->version == 2) {
+			dns_name = reps->ctr.ctr2.other_info->dns_name1;
+		}
+		(*proxy_list)[i] = talloc_strdup(*proxy_list, dns_name);
+		W_ERROR_HAVE_NO_MEMORY_AND_FREE((*proxy_list)[i], *proxy_list);
+	}
+	(*proxy_list)[i] = NULL;
+
+	talloc_free(reps);
+
+	return WERR_OK;
+}
+
+
+struct kdc_udp_proxy_state {
+	struct kdc_udp_call *call;
+	struct kdc_udp_socket *sock;
+	struct kdc_server *kdc;
+	char **proxy_list;
+	uint32_t next_proxy;
+	const char *proxy_ip;
+	uint16_t port;
+};
+
+
+static void kdc_udp_next_proxy(struct kdc_udp_proxy_state *state);
+
+/*
+  called when the send of the call to the proxy is complete
+  this is used to get an errors from the sendto()
+ */
+static void kdc_udp_proxy_sendto_done(struct tevent_req *req)
+{
+	struct kdc_udp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_udp_proxy_state);
+	ssize_t ret;
+	int sys_errno;
+
+	ret = tdgram_sendto_queue_recv(req, &sys_errno);
+	talloc_free(req);
+
+	if (ret == -1) {
+		DEBUG(4,("kdc_udp_proxy: sendto for %s gave %d : %s\n",
+			 state->proxy_ip, sys_errno, strerror(sys_errno)));
+		kdc_udp_next_proxy(state);
+	}
+}
+
+/*
+  called when the send of the reply to the client is complete
+  this is used to get an errors from the sendto()
+ */
+static void kdc_udp_proxy_reply_done(struct tevent_req *req)
+{
+	struct kdc_udp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_udp_proxy_state);
+	ssize_t ret;
+	int sys_errno;
+
+	ret = tdgram_sendto_queue_recv(req, &sys_errno);
+	if (ret == -1) {
+		DEBUG(3,("kdc_udp_proxy: reply sendto gave %d : %s\n",
+			 sys_errno, strerror(sys_errno)));
+	}
+
+	/* all done - we can destroy the proxy state */
+	talloc_free(req);
+	talloc_free(state);
+}
+
+
+/*
+  called when the proxy replies
+ */
+static void kdc_udp_proxy_reply(struct tevent_req *req)
+{
+	struct kdc_udp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_udp_proxy_state);
+	int sys_errno;
+	uint8_t *buf;
+	struct tsocket_address *src;
+	ssize_t len;
+
+	len = tdgram_recvfrom_recv(req, &sys_errno,
+				   state, &buf, &src);
+	talloc_free(req);
+	if (len == -1) {
+		DEBUG(4,("kdc_udp_proxy: reply from %s gave %d : %s\n",
+			 state->proxy_ip, sys_errno, strerror(sys_errno)));
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	state->call->out.length = len;
+	state->call->out.data = buf;
+
+	/* TODO: check the reply came from the right IP? */
+
+	req = tdgram_sendto_queue_send(state,
+				       state->kdc->task->event_ctx,
+				       state->sock->dgram,
+				       state->sock->send_queue,
+				       state->call->out.data,
+				       state->call->out.length,
+				       state->call->src);
+	if (req == NULL) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_udp_proxy_reply_done, state);
+}
+
+
+/*
+  called when we've resolved the name of a proxy
+ */
+static void kdc_udp_proxy_resolve_done(struct composite_context *c)
+{
+	struct kdc_udp_proxy_state *state;
+	NTSTATUS status;
+	struct tevent_req *req;
+	struct tsocket_address *local_addr, *proxy_addr;
+	int ret;
+	struct tdgram_context *dgram;
+	struct tevent_queue *send_queue;
+
+	state = talloc_get_type(c->async.private_data, struct kdc_udp_proxy_state);
+
+	status = resolve_name_recv(c, state, &state->proxy_ip);
+	if (!NT_STATUS_IS_OK(status)) {
+		DEBUG(0,("Unable to resolve proxy\n"));
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	/* get an address for us to use locally */
+	ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0, &local_addr);
+	if (ret != 0) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	ret = tsocket_address_inet_from_strings(state, "ip",
+						state->proxy_ip, state->port, &proxy_addr);
+	if (ret != 0) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	/* create a socket for us to work on */
+	ret = tdgram_inet_udp_socket(local_addr, proxy_addr, state, &dgram);
+	if (ret != 0) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	send_queue = tevent_queue_create(state, "kdc_udp_proxy");
+	if (send_queue == NULL) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	req = tdgram_sendto_queue_send(state,
+				       state->kdc->task->event_ctx,
+				       dgram,
+				       send_queue,
+				       state->call->in.data,
+				       state->call->in.length,
+				       proxy_addr);
+	if (req == NULL) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_udp_proxy_sendto_done, state);
+
+	/* setup to receive the reply from the proxy */
+	req = tdgram_recvfrom_send(state, state->kdc->task->event_ctx, dgram);
+	if (req == NULL) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_udp_proxy_reply, state);
+
+	tevent_req_set_endtime(req, state->kdc->task->event_ctx,
+			       timeval_current_ofs(state->kdc->proxy_timeout, 0));
+
+	DEBUG(4,("kdc_udp_proxy: proxying request to %s\n", state->proxy_ip));
+}
+
+
+/*
+  called when our proxies are not available
+ */
+static void kdc_udp_proxy_unavailable(struct kdc_udp_proxy_state *state)
+{
+	int kret;
+	krb5_data k5_error_blob;
+	struct tevent_req *req;
+
+	kret = krb5_mk_error(state->kdc->smb_krb5_context->krb5_context,
+			     KRB5KDC_ERR_SVC_UNAVAILABLE, NULL, NULL,
+			     NULL, NULL, NULL, NULL, &k5_error_blob);
+	if (kret != 0) {
+		DEBUG(2,(__location__ ": Unable to form krb5 error reply\n"));
+		talloc_free(state);
+		return;
+	}
+
+	state->call->out = data_blob_talloc(state, k5_error_blob.data, k5_error_blob.length);
+	krb5_data_free(&k5_error_blob);
+	if (!state->call->out.data) {
+		talloc_free(state);
+		return;
+	}
+
+	req = tdgram_sendto_queue_send(state,
+				       state->kdc->task->event_ctx,
+				       state->sock->dgram,
+				       state->sock->send_queue,
+				       state->call->out.data,
+				       state->call->out.length,
+				       state->call->src);
+	if (!req) {
+		talloc_free(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_udp_proxy_reply_done, state);
+}
+
+/*
+  try the next proxy in the list
+ */
+static void kdc_udp_next_proxy(struct kdc_udp_proxy_state *state)
+{
+	const char *proxy_dnsname = state->proxy_list[state->next_proxy];
+	struct nbt_name name;
+	struct composite_context *c;
+
+	if (proxy_dnsname == NULL) {
+		kdc_udp_proxy_unavailable(state);
+		return;
+	}
+
+	state->next_proxy++;
+
+	make_nbt_name(&name, proxy_dnsname, 0);
+
+	c = resolve_name_ex_send(lpcfg_resolve_context(state->kdc->task->lp_ctx),
+				 state,
+				 RESOLVE_NAME_FLAG_FORCE_DNS,
+				 0,
+				 &name,
+				 state->kdc->task->event_ctx);
+	if (c == NULL) {
+		kdc_udp_next_proxy(state);
+		return;
+	}
+	c->async.fn = kdc_udp_proxy_resolve_done;
+	c->async.private_data = state;
+}
+
+
+/*
+  proxy a UDP kdc request to a writeable DC
+ */
+void kdc_udp_proxy(struct kdc_server *kdc, struct kdc_udp_socket *sock,
+		   struct kdc_udp_call *call, uint16_t port)
+{
+	struct kdc_udp_proxy_state *state;
+	WERROR werr;
+
+	state = talloc_zero(kdc, struct kdc_udp_proxy_state);
+	if (state == NULL) {
+		talloc_free(call);
+		return;
+	}
+
+	state->call = talloc_steal(state, call);
+	state->sock = sock;
+	state->kdc  = kdc;
+	state->port = port;
+
+	werr = kdc_proxy_get_writeable_dcs(kdc, state, &state->proxy_list);
+	if (!W_ERROR_IS_OK(werr)) {
+		kdc_udp_proxy_unavailable(state);
+		return;
+	}
+
+	kdc_udp_next_proxy(state);
+}
+
+
+struct kdc_tcp_proxy_state {
+	struct kdc_tcp_call *call;
+	struct kdc_tcp_connection *kdc_conn;
+	struct kdc_server *kdc;
+	uint16_t port;
+	uint32_t next_proxy;
+	char **proxy_list;
+	const char *proxy_ip;
+};
+
+static void kdc_tcp_next_proxy(struct kdc_tcp_proxy_state *state);
+
+/*
+  called when the send of the proxied reply to the client is done
+ */
+static void kdc_tcp_proxy_reply_done(struct tevent_req *req)
+{
+	struct kdc_tcp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_tcp_proxy_state);
+	int ret, sys_errno;
+
+	ret = tstream_writev_queue_recv(req, &sys_errno);
+	if (ret == -1) {
+		DEBUG(4,("kdc_tcp_proxy: writev of reply gave %d : %s\n",
+			 sys_errno, strerror(sys_errno)));
+	}
+	talloc_free(req);
+	talloc_free(state);
+}
+
+/*
+  called when the recv of the proxied reply is done
+ */
+static void kdc_tcp_proxy_recv_done(struct tevent_req *req)
+{
+	struct kdc_tcp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_tcp_proxy_state);
+	NTSTATUS status;
+
+	status = tstream_read_pdu_blob_recv(req,
+					    state,
+					    &state->call->out);
+	talloc_free(req);
+
+	if (!NT_STATUS_IS_OK(status)) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+
+	/* send the reply to the original caller */
+
+	state->call->out_iov[0].iov_base = (char *)state->call->out.data;
+	state->call->out_iov[0].iov_len = state->call->out.length;
+
+	req = tstream_writev_queue_send(state,
+					state->kdc_conn->conn->event.ctx,
+					state->kdc_conn->tstream,
+					state->kdc_conn->send_queue,
+					state->call->out_iov, 1);
+	if (req == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_tcp_proxy_reply_done, state);
+}
+
+/*
+  called when the send of the proxied packet is done
+ */
+static void kdc_tcp_proxy_send_done(struct tevent_req *req)
+{
+	struct kdc_tcp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_tcp_proxy_state);
+	int ret, sys_errno;
+
+	ret = tstream_writev_queue_recv(req, &sys_errno);
+	talloc_free(req);
+	if (ret == -1) {
+		kdc_tcp_next_proxy(state);
+	}
+}
+
+/*
+  called when we've connected to the proxy
+ */
+static void kdc_tcp_proxy_connect_done(struct tevent_req *req)
+{
+	struct kdc_tcp_proxy_state *state = tevent_req_callback_data(req,
+								     struct kdc_tcp_proxy_state);
+	int ret, sys_errno;
+	struct tstream_context *stream;
+	struct tevent_queue *send_queue;
+
+
+	ret = tstream_inet_tcp_connect_recv(req, &sys_errno, state, &stream, NULL);
+	talloc_free(req);
+
+	if (ret != 0) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	RSIVAL(state->call->out_hdr, 0, state->call->in.length);
+	state->call->out_iov[0].iov_base = (char *)state->call->out_hdr;
+	state->call->out_iov[0].iov_len = 4;
+	state->call->out_iov[1].iov_base = (char *) state->call->in.data;
+	state->call->out_iov[1].iov_len = state->call->in.length;
+
+	send_queue = tevent_queue_create(state, "kdc_tcp_proxy");
+	if (send_queue == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	req = tstream_writev_queue_send(state,
+					state->kdc_conn->conn->event.ctx,
+					stream,
+					send_queue,
+					state->call->out_iov, 2);
+	if (req == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_tcp_proxy_send_done, state);
+
+	req = tstream_read_pdu_blob_send(state,
+					 state->kdc_conn->conn->event.ctx,
+					 stream,
+					 4, /* initial_read_size */
+					 packet_full_request_u32,
+					 state);
+	if (req == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_tcp_proxy_recv_done, state);
+	tevent_req_set_endtime(req, state->kdc->task->event_ctx,
+			       timeval_current_ofs(state->kdc->proxy_timeout, 0));
+
+}
+
+
+/*
+  called when name resolution for a proxy is done
+ */
+static void kdc_tcp_proxy_resolve_done(struct composite_context *c)
+{
+	struct kdc_tcp_proxy_state *state;
+	NTSTATUS status;
+	struct tevent_req *req;
+	struct tsocket_address *local_addr, *proxy_addr;
+	int ret;
+
+	state = talloc_get_type(c->async.private_data, struct kdc_tcp_proxy_state);
+
+	status = resolve_name_recv(c, state, &state->proxy_ip);
+	if (!NT_STATUS_IS_OK(status)) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	/* get an address for us to use locally */
+	ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0, &local_addr);
+	if (ret != 0) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	ret = tsocket_address_inet_from_strings(state, "ip",
+						state->proxy_ip, state->port, &proxy_addr);
+	if (ret != 0) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	/* connect to the proxy */
+	req = tstream_inet_tcp_connect_send(state, state->kdc->task->event_ctx, local_addr, proxy_addr);
+	if (req == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_tcp_proxy_connect_done, state);
+
+	tevent_req_set_endtime(req, state->kdc->task->event_ctx,
+			       timeval_current_ofs(state->kdc->proxy_timeout, 0));
+
+	DEBUG(4,("kdc_tcp_proxy: proxying request to %s\n", state->proxy_ip));
+}
+
+
+/*
+  called when our proxies are not available
+ */
+static void kdc_tcp_proxy_unavailable(struct kdc_tcp_proxy_state *state)
+{
+	int kret;
+	krb5_data k5_error_blob;
+	struct tevent_req *req;
+
+	kret = krb5_mk_error(state->kdc->smb_krb5_context->krb5_context,
+			     KRB5KDC_ERR_SVC_UNAVAILABLE, NULL, NULL,
+			     NULL, NULL, NULL, NULL, &k5_error_blob);
+	if (kret != 0) {
+		DEBUG(2,(__location__ ": Unable to form krb5 error reply\n"));
+		talloc_free(state);
+		return;
+	}
+
+
+	state->call->out = data_blob_talloc(state, k5_error_blob.data, k5_error_blob.length);
+	krb5_data_free(&k5_error_blob);
+	if (!state->call->out.data) {
+		talloc_free(state);
+		return;
+	}
+
+	state->call->out_iov[0].iov_base = (char *)state->call->out.data;
+	state->call->out_iov[0].iov_len = state->call->out.length;
+
+	req = tstream_writev_queue_send(state,
+					state->kdc_conn->conn->event.ctx,
+					state->kdc_conn->tstream,
+					state->kdc_conn->send_queue,
+					state->call->out_iov, 1);
+	if (!req) {
+		talloc_free(state);
+		return;
+	}
+
+	tevent_req_set_callback(req, kdc_tcp_proxy_reply_done, state);
+}
+
+/*
+  try the next proxy in the list
+ */
+static void kdc_tcp_next_proxy(struct kdc_tcp_proxy_state *state)
+{
+	const char *proxy_dnsname = state->proxy_list[state->next_proxy];
+	struct nbt_name name;
+	struct composite_context *c;
+
+	if (proxy_dnsname == NULL) {
+		kdc_tcp_proxy_unavailable(state);
+		return;
+	}
+
+	state->next_proxy++;
+
+	make_nbt_name(&name, proxy_dnsname, 0);
+
+	c = resolve_name_ex_send(lpcfg_resolve_context(state->kdc->task->lp_ctx),
+				 state,
+				 RESOLVE_NAME_FLAG_FORCE_DNS,
+				 0,
+				 &name,
+				 state->kdc->task->event_ctx);
+	if (c == NULL) {
+		kdc_tcp_next_proxy(state);
+		return;
+	}
+	c->async.fn = kdc_tcp_proxy_resolve_done;
+	c->async.private_data = state;
+}
+
+
+/*
+  proxy a TCP kdc request to a writeable DC
+ */
+void kdc_tcp_proxy(struct kdc_server *kdc, struct kdc_tcp_connection *kdc_conn,
+		   struct kdc_tcp_call *call, uint16_t port)
+{
+	struct kdc_tcp_proxy_state *state;
+	WERROR werr;
+
+	state = talloc_zero(kdc_conn, struct kdc_tcp_proxy_state);
+
+	state->call = talloc_steal(state, call);
+	state->kdc_conn = kdc_conn;
+	state->kdc  = kdc;
+	state->port = port;
+
+	werr = kdc_proxy_get_writeable_dcs(kdc, state, &state->proxy_list);
+	if (!W_ERROR_IS_OK(werr)) {
+		kdc_tcp_proxy_unavailable(state);
+		return;
+	}
+
+	kdc_tcp_next_proxy(state);
+}