s3:messaging: make it possible to receive a fd array from another process

In order to receive the fd array the caller needs to use
messaging_filtered_read_send/recv(). For all higher level
methods we silently close/ignore the fd array.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>

4 files changed, 83 insertions, 13 deletions

diff --git a/source3/lib/dbwrap/dbwrap_watch.c b/source3/lib/dbwrap/dbwrap_watch.c
index a5f1ebd5bf..9ff8fc24b4 100644
--- a/source3/lib/dbwrap/dbwrap_watch.c
+++ b/source3/lib/dbwrap/dbwrap_watch.c
@@ -299,6 +299,9 @@ static bool dbwrap_record_watch_filter(struct messaging_rec *rec,
 	if (rec->msg_type != MSG_DBWRAP_MODIFIED) {
 		return false;
 	}
+	if (rec->num_fds != 0) {
+		return false;
+	}
 	if (rec->buf.length != state->w_key.dsize) {
 		return false;
 	}
diff --git a/source3/lib/messages.c b/source3/lib/messages.c
index 0e0259236e..56108abd21 100644
--- a/source3/lib/messages.c
+++ b/source3/lib/messages.c
@@ -204,6 +204,7 @@ bool message_send_all(struct messaging_context *msg_ctx,
 }
 
 static void messaging_recv_cb(const uint8_t *msg, size_t msg_len,
+			      const int *fds, size_t num_fds,
 			      void *private_data)
 {
 	struct messaging_context *msg_ctx = talloc_get_type_abort(
@@ -211,19 +212,38 @@ static void messaging_recv_cb(const uint8_t *msg, size_t msg_len,
 	const struct messaging_hdr *hdr;
 	struct server_id_buf idbuf;
 	struct messaging_rec rec;
+	int64_t fds64[MIN(num_fds, INT8_MAX)];
+	size_t i;
 
 	if (msg_len < sizeof(*hdr)) {
+		for (i=0; i < num_fds; i++) {
+			close(fds[i]);
+		}
 		DEBUG(1, ("message too short: %u\n", (unsigned)msg_len));
 		return;
 	}
 
+	if (num_fds > INT8_MAX) {
+		for (i=0; i < num_fds; i++) {
+			close(fds[i]);
+		}
+		DEBUG(1, ("too many fds: %u\n", (unsigned)num_fds));
+		return;
+	}
+
+	for (i=0; i < num_fds; i++) {
+		fds64[i] = fds[i];
+	}
+
 	/*
 	 * messages_dgm guarantees alignment, so we can cast here
 	 */
 	hdr = (const struct messaging_hdr *)msg;
 
-	DEBUG(10, ("%s: Received message 0x%x len %u from %s\n", __func__,
-		   (unsigned)hdr->msg_type, (unsigned)(msg_len - sizeof(*hdr)),
+	DEBUG(10, ("%s: Received message 0x%x len %u (num_fds:%u) from %s\n",
+		   __func__, (unsigned)hdr->msg_type,
+		   (unsigned)(msg_len - sizeof(*hdr)),
+		   (unsigned)num_fds,
 		   server_id_str_buf(hdr->src, &idbuf)));
 
 	rec = (struct messaging_rec) {
@@ -232,7 +252,9 @@ static void messaging_recv_cb(const uint8_t *msg, size_t msg_len,
 		.src = hdr->src,
 		.dest = hdr->dst,
 		.buf.data = discard_const_p(uint8, msg) + sizeof(*hdr),
-		.buf.length = msg_len - sizeof(*hdr)
+		.buf.length = msg_len - sizeof(*hdr),
+		.num_fds = num_fds,
+		.fds = fds64,
 	};
 
 	messaging_dispatch_rec(msg_ctx, &rec);
@@ -501,9 +523,10 @@ static struct messaging_rec *messaging_rec_dup(TALLOC_CTX *mem_ctx,
 					       struct messaging_rec *rec)
 {
 	struct messaging_rec *result;
+	size_t fds_size = sizeof(int64_t) * rec->num_fds;
 
-	result = talloc_pooled_object(mem_ctx, struct messaging_rec,
-				      1, rec->buf.length);
+	result = talloc_pooled_object(mem_ctx, struct messaging_rec, 2,
+				      rec->buf.length + fds_size);
 	if (result == NULL) {
 		return NULL;
 	}
@@ -513,6 +536,13 @@ static struct messaging_rec *messaging_rec_dup(TALLOC_CTX *mem_ctx,
 
 	result->buf.data = talloc_memdup(result, rec->buf.data,
 					 rec->buf.length);
+
+	result->fds = NULL;
+	if (result->num_fds > 0) {
+		result->fds = talloc_array(result, int64_t, result->num_fds);
+		memcpy(result->fds, rec->fds, fds_size);
+	}
+
 	return result;
 }
 
@@ -692,6 +722,10 @@ static bool messaging_read_filter(struct messaging_rec *rec,
 	struct messaging_read_state *state = talloc_get_type_abort(
 		private_data, struct messaging_read_state);
 
+	if (rec->num_fds != 0) {
+		return false;
+	}
+
 	return rec->msg_type == state->msg_type;
 }
 
@@ -825,6 +859,7 @@ void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 {
 	struct messaging_callback *cb, *next;
 	unsigned i;
+	size_t j;
 
 	for (cb = msg_ctx->callbacks; cb != NULL; cb = next) {
 		next = cb->next;
@@ -832,6 +867,16 @@ void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 			continue;
 		}
 
+		/*
+		 * the old style callbacks don't support fd passing
+		 */
+		for (j=0; j < rec->num_fds; j++) {
+			int fd = rec->fds[j];
+			close(fd);
+		}
+		rec->num_fds = 0;
+		rec->fds = NULL;
+
 		if (server_id_same_process(&rec->src, &rec->dest)) {
 			/*
 			 * This is a self-send. We are called here from
@@ -859,6 +904,12 @@ void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 	}
 
 	if (!messaging_append_new_waiters(msg_ctx)) {
+		for (j=0; j < rec->num_fds; j++) {
+			int fd = rec->fds[j];
+			close(fd);
+		}
+		rec->num_fds = 0;
+		rec->fds = NULL;
 		return;
 	}
 
@@ -889,10 +940,26 @@ void messaging_dispatch_rec(struct messaging_context *msg_ctx,
 			req, struct messaging_filtered_read_state);
 		if (state->filter(rec, state->private_data)) {
 			messaging_filtered_read_done(req, rec);
+
+			/*
+			 * Only the first one gets the fd-array
+			 */
+			rec->num_fds = 0;
+			rec->fds = NULL;
 		}
 
 		i += 1;
 	}
+
+	/*
+	 * If the fd-array isn't used, just close it.
+	 */
+	for (j=0; j < rec->num_fds; j++) {
+		int fd = rec->fds[j];
+		close(fd);
+	}
+	rec->num_fds = 0;
+	rec->fds = NULL;
 }
 
 static int mess_parent_dgm_cleanup(void *private_data);
diff --git a/source3/lib/messages_dgm.c b/source3/lib/messages_dgm.c
index 7ba79fcfd0..68307698a5 100644
--- a/source3/lib/messages_dgm.c
+++ b/source3/lib/messages_dgm.c
@@ -44,6 +44,8 @@ struct messaging_dgm_context {
 
 	void (*recv_cb)(const uint8_t *msg,
 			size_t msg_len,
+			const int *fds,
+			size_t num_fds,
 			void *private_data);
 	void *recv_cb_private_data;
 
@@ -179,6 +181,8 @@ int messaging_dgm_init(struct tevent_context *ev,
 		       uid_t dir_owner,
 		       void (*recv_cb)(const uint8_t *msg,
 				       size_t msg_len,
+				       const int *fds,
+				       size_t num_fds,
 				       void *private_data),
 		       void *recv_cb_private_data)
 {
@@ -330,15 +334,9 @@ static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
 {
 	struct messaging_dgm_context *dgm_ctx = talloc_get_type_abort(
 		private_data, struct messaging_dgm_context);
-	size_t i;
 
-	/* for now we ignore passed file descriptors */
-	for (i = 0; i < num_fds; i++) {
-		close(fds[i]);
-		fds[i] = -1;
-	}
-
-	dgm_ctx->recv_cb(msg, msg_len, dgm_ctx->recv_cb_private_data);
+	dgm_ctx->recv_cb(msg, msg_len, fds, num_fds,
+			 dgm_ctx->recv_cb_private_data);
 }
 
 int messaging_dgm_cleanup(pid_t pid)
diff --git a/source3/lib/messages_dgm.h b/source3/lib/messages_dgm.h
index 169d863219..3c915c18ef 100644
--- a/source3/lib/messages_dgm.h
+++ b/source3/lib/messages_dgm.h
@@ -26,6 +26,8 @@ int messaging_dgm_init(struct tevent_context *ev,
 		       uid_t dir_owner,
 		       void (*recv_cb)(const uint8_t *msg,
 				       size_t msg_len,
+				       const int *fds,
+				       size_t num_fds,
 				       void *private_data),
 		       void *recv_cb_private_data);
 void messaging_dgm_destroy(void);