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[SETUPLIB] Improve the bootloader 'validity' checks -- Addendum to f06734e5 (r74512).

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Adapted from PR #89 by Serge Gautherie.
This should improve the situation described in CORE-12672 and CORE-4870.
This commit is contained in:
Hermès Bélusca-Maïto 2017-12-24 22:37:19 +01:00
parent ad9e57895d
commit a7a11dd60d
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GPG key ID: 3B2539C65E7B93D0
1 changed files with 8 additions and 8 deletions
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16
base/setup/lib/bootsup.c
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@ -551,7 +551,6 @@ IsThereAValidBootSector(
HANDLE FileHandle; HANDLE FileHandle;
LARGE_INTEGER FileOffset; LARGE_INTEGER FileOffset;
PUCHAR BootSector; PUCHAR BootSector;
ULONG Instruction;
/* Allocate buffer for bootsector */ /* Allocate buffer for bootsector */
BootSector = RtlAllocateHeap(ProcessHeap, 0, SECTORSIZE); BootSector = RtlAllocateHeap(ProcessHeap, 0, SECTORSIZE);
@ -593,17 +592,18 @@ IsThereAValidBootSector(
if (!NT_SUCCESS(Status)) if (!NT_SUCCESS(Status))
goto Quit; goto Quit;
/* Check the instruction; we use a ULONG to read three bytes */ /* Check for the existence of the bootsector signature */
Instruction = (*(PULONG)BootSector) & 0x00FFFFFF; IsValid = (*(PUSHORT)(BootSector + 0x1FE) == 0xAA55);
IsValid = (Instruction != 0x00000000); if (IsValid)
{
/* Check the bootsector signature */ /* Check for the first instruction encoded on three bytes */
IsValid &= (*(PUSHORT)(BootSector + 0x1fe) == 0xaa55); IsValid = (((*(PULONG)BootSector) & 0x00FFFFFF) != 0x00000000);
}
Quit: Quit:
/* Free the boot sector */ /* Free the boot sector */
RtlFreeHeap(ProcessHeap, 0, BootSector); RtlFreeHeap(ProcessHeap, 0, BootSector);
return IsValid; // Status; return IsValid;
} }
static static