fix memory corruption in pubkey filter over network

grub_pubkey_open closed original file after it was read; it set
io->device to NULL to prevent grub_file_close from trying to close device.
But network device itself is stacked (net -> bufio); and bufio preserved
original netfs file which hold reference to device. grub_file_close(io)
called grub_bufio_close which called grub_file_close for original file.
grub_file_close(netfs-file) now also called grub_device_close which
freed file->device->net. So file structure returned by grub_pubkey_open
now had device->net pointed to freed memory. When later file was closed,
it was attempted to be freed again.

Change grub_pubkey_open to behave like other filters - preserve original
parent file and pass grub_file_close down to parent. In this way only the
original file will close device. We really need to move this logic into
core instead.

Also plug memory leaks in error paths on the way.

Reported-By: Robert Kliewer <robert.kliewer@gmail.com>
Closes: bug #43601

ChangeLog

@@ -13,6 +13,8 @@
 	* tests/file_filter/keys: Likewise.
 	* tests/file_filter/keys.pub: Likewise.
 	* tests/file_filter/test.cfg: Likewise.
+	* grub-core/commands/verify.c: Fix memory corruption doing
+	signature check for network files (closes 43601).
 
 2014-12-01  Andrei Borzenkov  <arvidjaar@gmail.com>
 

grub-core/commands/verify.c

@@ -33,6 +33,13 @@
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
+struct grub_verified
+{
+  grub_file_t file;
+  void *buf;
+};
+typedef struct grub_verified *grub_verified_t;
+
 enum
   {
     OPTION_SKIP_SIG = 0
@@ -802,19 +809,39 @@ grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
 
 static int sec = 0;
 
+static void
+verified_free (grub_verified_t verified)
+{
+  if (verified)
+    {
+      grub_free (verified->buf);
+      grub_free (verified);
+    }
+}
+
 static grub_ssize_t
 verified_read (struct grub_file *file, char *buf, grub_size_t len)
 {
-  grub_memcpy (buf, (char *) file->data + file->offset, len);
+  grub_verified_t verified = file->data;
+
+  grub_memcpy (buf, (char *) verified->buf + file->offset, len);
   return len;
 }
 
 static grub_err_t
 verified_close (struct grub_file *file)
 {
-  grub_free (file->data);
+  grub_verified_t verified = file->data;
+
+  grub_file_close (verified->file);
+  verified_free (verified);
   file->data = 0;
-  return GRUB_ERR_NONE;
+
+  /* device and name are freed by parent */
+  file->device = 0;
+  file->name = 0;
+
+  return grub_errno;
 }
 
 struct grub_fs verified_fs =
@@ -832,6 +859,7 @@ grub_pubkey_open (grub_file_t io, const char *filename)
   grub_err_t err;
   grub_file_filter_t curfilt[GRUB_FILE_FILTER_MAX];
   grub_file_t ret;
+  grub_verified_t verified;
 
   if (!sec)
     return io;
@@ -857,7 +885,10 @@ grub_pubkey_open (grub_file_t io, const char *filename)
 
   ret = grub_malloc (sizeof (*ret));
   if (!ret)
+    {
+      grub_file_close (sig);
       return NULL;
+    }
   *ret = *io;
 
   ret->fs = &verified_fs;
@@ -866,29 +897,46 @@ grub_pubkey_open (grub_file_t io, const char *filename)
     {
       grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
 		  "big file signature isn't implemented yet");
-      return NULL;
+      grub_file_close (sig);
-    }
-  ret->data = grub_malloc (ret->size);
-  if (!ret->data)
-    {
       grub_free (ret);
       return NULL;
     }
-  if (grub_file_read (io, ret->data, ret->size) != (grub_ssize_t) ret->size)
+  verified = grub_malloc (sizeof (*verified));
+  if (!verified)
+    {
+      grub_file_close (sig);
+      grub_free (ret);
+      return NULL;
+    }
+  verified->buf = grub_malloc (ret->size);
+  if (!verified->buf)
+    {
+      grub_file_close (sig);
+      grub_free (verified);
+      grub_free (ret);
+      return NULL;
+    }
+  if (grub_file_read (io, verified->buf, ret->size) != (grub_ssize_t) ret->size)
     {
       if (!grub_errno)
 	grub_error (GRUB_ERR_FILE_READ_ERROR, N_("premature end of file %s"),
 		    filename);
+      grub_file_close (sig);
+      verified_free (verified);
+      grub_free (ret);
       return NULL;
     }
 
-  err = grub_verify_signature_real (ret->data, ret->size, 0, sig, NULL);
+  err = grub_verify_signature_real (verified->buf, ret->size, 0, sig, NULL);
   grub_file_close (sig);
   if (err)
+    {
+      verified_free (verified);
+      grub_free (ret);
       return NULL;
-  io->device = 0;
+    }
-  io->name = 0;
+  verified->file = io;
-  grub_file_close (io);
+  ret->data = verified;
   return ret;
 }