From 0ed2458cc4eff6d9a9199527e2a0b6d445802f94 Mon Sep 17 00:00:00 2001 From: Maxim Suhanov Date: Mon, 28 Aug 2023 16:32:33 +0300 Subject: [PATCH 2/6] fs/ntfs: Fix an OOB read when reading data from the resident $DATA attribute 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 c3c4db117bba..a68e173d8285 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; } -- 2.43.0