[Spice-devel] [vdagent-win PATCH v2] Avoid to use names with reserved characters.

[Frediano Ziglio]

Some characters are reserved and should not be used in Windows
independently by the file system used.
This avoid to use paths in the filename which could lead to some
nasty hacks (like names like "..\hack.txt").
The return statement cause the file transfer to be aborted with
VD_AGENT_FILE_XFER_STATUS_ERROR as status.

":" is used to separate filenames from stream names and can be used
to create hidden streams. Also is used for drive separator (A:)
or device names (NUL:).
"/" and "\" are reserved for components (directory, filename, drive,
share, server) separators.
"*" and "?" are wildcards (which on Windows are supported by
different APIs too).
"<", ">", """ and "|" are reserved for shell usage.

More information on "Naming Files, Paths, and Namespaces" page at
https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx

This fixes also https://bugzilla.redhat.com/show_bug.cgi?id=1520393.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 vdagent/file_xfer.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

Changes since v1:
- define a constant in code;
- add some commit message and links.

diff --git a/vdagent/file_xfer.cpp b/vdagent/file_xfer.cpp
index e877cca..8203b99 100644
--- a/vdagent/file_xfer.cpp
+++ b/vdagent/file_xfer.cpp
@@ -33,6 +33,12 @@
 #include "file_xfer.h"
 #include "as_user.h"
 
+#define FILENAME_RESERVED_CHAR_LIST \
+    ":" /* streams and devices */ \
+    "/\\" /* components separator */ \
+    "?*" /* wildcards */ \
+    "<>\"|" /* reserved to shell */
+
 void FileXfer::reset()
 {
     FileXferTasks::iterator iter;
@@ -72,6 +78,10 @@ void FileXfer::handle_start(VDAgentFileXferStartMessage* start,
         return;
     }
     vd_printf("%u %s (%" PRIu64 ")", start->id, file_name, file_size);
+    if (strcspn(file_name, FILENAME_RESERVED_CHAR_LIST) != strlen(file_name)) {
+        vd_printf("filename contains invalid characters");
+        return;
+    }
     if (!as_user.begin()) {
         vd_printf("as_user failed");
         return;
-- 
2.17.0