Subject: Complain if an inc-recursive path is not right for its dir.
From: Wayne Davison <[email-masked]>
Date: Wed, 31 Dec 2014 20:41:03 +0000 (-0800)

Complain if an inc-recursive path is not right for its dir.
This ensures that a malicious sender can't use a just-sent
symlink as a trasnfer path.
---

diff --git a/flist.c b/flist.c
index c24672e..92e4b65 100644
--- a/flist.c
+++ b/flist.c
@@ -2435,8 +2435,9 @@ struct file_list *send_file_list(int f, int argc, char *argv[])
 	return flist;
 }
 
-struct file_list *recv_file_list(int f)
+struct file_list *recv_file_list(int f, int dir_ndx)
 {
+	const char *good_dirname = NULL;
 	struct file_list *flist;
 	int dstart, flags;
 	int64 start_read;
@@ -2492,6 +2493,23 @@ struct file_list *recv_file_list(int f)
 		flist_expand(flist, 1);
 		file = recv_file_entry(f, flist, flags);
 
+		if (inc_recurse) {
+			static const char empty_dir[] = "\0";
+			const char *cur_dir = file->dirname ? file->dirname : empty_dir;
+			if (relative_paths && *cur_dir == '/')
+				cur_dir++;
+			if (cur_dir != good_dirname) {
+				const char *d = dir_ndx >= 0 ? f_name(dir_flist->files[dir_ndx], NULL) : empty_dir;
+				if (strcmp(cur_dir, d) != 0) {
+					rprintf(FERROR,
+						"ABORTING due to invalid dir prefix from sender: %s (should be: %s)\n",
+						cur_dir, d);
+					exit_cleanup(RERR_PROTOCOL);
+				}
+				good_dirname = cur_dir;
+			}
+		}
+
 		if (S_ISREG(file->mode)) {
 			/* Already counted */
 		} else if (S_ISDIR(file->mode)) {
@@ -2615,7 +2633,7 @@ void recv_additional_file_list(int f)
 			rprintf(FINFO, "[%s] receiving flist for dir %d\n",
 				who_am_i(), ndx);
 		}
-		flist = recv_file_list(f);
+		flist = recv_file_list(f, ndx);
 		flist->parent_ndx = ndx;
 	}
 }
diff --git a/io.c b/io.c
index b9a9bd0..a868fa9 100644
--- a/io.c
+++ b/io.c
@@ -1685,7 +1685,7 @@ void wait_for_receiver(void)
 				rprintf(FINFO, "[%s] receiving flist for dir %d\n",
 					who_am_i(), ndx);
 			}
-			flist = recv_file_list(iobuf.in_fd);
+			flist = recv_file_list(iobuf.in_fd, ndx);
 			flist->parent_ndx = ndx;
 #ifdef SUPPORT_HARD_LINKS
 			if (preserve_hard_links)
diff --git a/main.c b/main.c
index e7a13f7..713b818 100644
--- a/main.c
+++ b/main.c
@@ -1009,7 +1009,7 @@ static void do_server_recv(int f_in, int f_out, int argc, char *argv[])
 		filesfrom_fd = -1;
 	}
 
-	flist = recv_file_list(f_in);
+	flist = recv_file_list(f_in, -1);
 	if (!flist) {
 		rprintf(FERROR,"server_recv: recv_file_list error\n");
 		exit_cleanup(RERR_FILESELECT);
@@ -1183,7 +1183,7 @@ int client_run(int f_in, int f_out, pid_t pid, int argc, char *argv[])
 
 	if (write_batch && !am_server)
 		start_write_batch(f_in);
-	flist = recv_file_list(f_in);
+	flist = recv_file_list(f_in, -1);
 	if (inc_recurse && file_total == 1)
 		recv_additional_file_list(f_in);
 
diff --git a/rsync.c b/rsync.c
index 68ff6b1..c3ecc51 100644
--- a/rsync.c
+++ b/rsync.c
@@ -364,7 +364,7 @@ int read_ndx_and_attrs(int f_in, int f_out, int *iflag_ptr, uchar *type_ptr,
 		}
 		/* Send all the data we read for this flist to the generator. */
 		start_flist_forward(ndx);
-		flist = recv_file_list(f_in);
+		flist = recv_file_list(f_in, ndx);
 		flist->parent_ndx = ndx;
 		stop_flist_forward();
 	}