[PATCH 11/13] libxl: use pipe instead of temporary file for VNC viewer --autopass

[Matthew Daley <mattd@bugfuzz.com>]

Coverity was complaining about the permissions implicitly set on the
temporary file used to pass the VNC password to the viewer when using
the --autopass feature. By replacing the use of the temporary file
with a pipe, we fix the problem (well, quiesce Coverity at least), tidy
the code and remove the buildup of temporary file cruft all at once.

Tested with TightVNC.

Coverity-ID: 1055958
Signed-off-by: Matthew Daley <mattd@bugfuzz.com>
---
 tools/libxl/libxl.c |   30 +++++++++++-------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index ca4c2cd..41b8f60 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1623,7 +1623,7 @@ int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass)
     GC_INIT(ctx);
     const char *vnc_port;
     const char *vnc_listen = NULL, *vnc_pass = NULL;
-    int port = 0, autopass_fd = -1;
+    int port = 0, autopass_fds[2] = {-1, -1};
     char *vnc_bin, *args[] = {
         "vncviewer",
         NULL, /* hostname:display */
@@ -1655,38 +1655,30 @@ int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t domid, int autopass)
     args[1] = libxl__sprintf(gc, "%s:%d", vnc_listen, port);
 
     if ( vnc_pass ) {
-        char tmpname[] = "/tmp/vncautopass.XXXXXX";
-        autopass_fd = mkstemp(tmpname);
-        if ( autopass_fd < 0 ) {
-            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
-                             "mkstemp %s failed", tmpname);
-            goto x_fail;
-        }
-
-        if ( unlink(tmpname) ) {
-            /* should never happen */
-            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
-                             "unlink %s failed", tmpname);
+        if ( pipe(autopass_fds) < 0 ) {
+            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "pipe failed");
             goto x_fail;
         }
 
-        if ( libxl_write_exactly(ctx, autopass_fd, vnc_pass, strlen(vnc_pass),
-                                    tmpname, "vnc password") )
+        if ( libxl_write_exactly(ctx, autopass_fds[1], vnc_pass, strlen(vnc_pass),
+                                    "(pipe)", "vnc password") )
             goto x_fail;
 
-        if ( lseek(autopass_fd, SEEK_SET, 0) ) {
-            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
-                             "rewind %s (autopass) failed", tmpname);
+        if ( close(autopass_fds[1]) < 0 ) {
+            autopass_fds[1] = -1;
             goto x_fail;
         }
+        autopass_fds[1] = -1;
 
         args[2] = "-autopass";
     }
 
-    libxl__exec(gc, autopass_fd, -1, -1, args[0], args, NULL);
+    libxl__exec(gc, autopass_fds[0], -1, -1, args[0], args, NULL);
     abort();
 
  x_fail:
+    if ( autopass_fds[0] >= 0 ) close(autopass_fds[0]);
+    if ( autopass_fds[1] >= 0 ) close(autopass_fds[1]);
     GC_FREE;
     return ERROR_FAIL;
 }
-- 
1.7.10.4