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From: Daniel Kiper <>
Subject: [SECURITY PATCH 2/6] fs/ntfs: Fix an OOB read when reading data from the resident $DATA attribute
Date: Tue,  3 Oct 2023 19:12:24 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <ZRxK8s4nQV2jBq/>

From: Maxim Suhanov <>

When reading a file containing resident data, i.e., the file data is stored in
the $DATA attribute within the NTFS file record, not in external clusters,
there are no checks that this resident data actually fits the corresponding
file record segment.

When parsing a specially-crafted file system image, the current NTFS code will
read the file data from an arbitrary, attacker-chosen memory offset and of
arbitrary, attacker-chosen length.

This allows an attacker to display arbitrary chunks of memory, which could
contain sensitive information like password hashes or even plain-text,
obfuscated passwords from BS EFI variables.

This fix implements a check to ensure that resident data is read from the
corresponding file record segment only.

Fixes: CVE-2023-4693

Reported-by: Maxim Suhanov <>
Signed-off-by: Maxim Suhanov <>
Reviewed-by: Daniel Kiper <>
 grub-core/fs/ntfs.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/grub-core/fs/ntfs.c b/grub-core/fs/ntfs.c
index c3c4db117..a68e173d8 100644
--- a/grub-core/fs/ntfs.c
+++ b/grub-core/fs/ntfs.c
@@ -401,7 +401,18 @@ read_data (struct grub_ntfs_attr *at, grub_uint8_t *pa, grub_uint8_t *dest,
       if (ofs + len > u32at (pa, 0x10))
 	return grub_error (GRUB_ERR_BAD_FS, "read out of range");
-      grub_memcpy (dest, pa + u32at (pa, 0x14) + ofs, len);
+      if (u32at (pa, 0x10) > (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR))
+	return grub_error (GRUB_ERR_BAD_FS, "resident attribute too large");
+      if (pa >= at->mft->buf + (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR))
+	return grub_error (GRUB_ERR_BAD_FS, "resident attribute out of range");
+      if (u16at (pa, 0x14) + u32at (pa, 0x10) >
+	  (grub_addr_t) at->mft->buf + (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR) - (grub_addr_t) pa)
+	return grub_error (GRUB_ERR_BAD_FS, "resident attribute out of range");
+      grub_memcpy (dest, pa + u16at (pa, 0x14) + ofs, len);
       return 0;

Grub-devel mailing list

  parent reply	other threads:[~2023-10-03 17:13 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-03 17:10 [SECURITY PATCH 0/6] GRUB2 NTFS driver vulnerabilities - 2023/10/03 Daniel Kiper
2023-10-03 17:12 ` [SECURITY PATCH 1/6] fs/ntfs: Fix an OOB write when parsing the $ATTRIBUTE_LIST attribute for the $MFT file Daniel Kiper
2023-10-03 17:12 ` Daniel Kiper [this message]
2023-10-03 17:12 ` [SECURITY PATCH 3/6] fs/ntfs: Fix an OOB read when parsing directory entries from resident and non-resident index attributes Daniel Kiper
2023-10-03 17:12 ` [SECURITY PATCH 4/6] fs/ntfs: Fix an OOB read when parsing bitmaps for " Daniel Kiper
2023-10-03 17:12 ` [SECURITY PATCH 5/6] fs/ntfs: Fix an OOB read when parsing a volume label Daniel Kiper
2023-10-03 17:12 ` [SECURITY PATCH 6/6] fs/ntfs: Make code more readable Daniel Kiper

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