From f423b7078d291b84952464aca6930a9d772319b0 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Tue, 8 Jun 2021 14:12:58 +0200
Subject: [PATCH 09/10] NetworkPkg/IScsiDxe: fix IScsiHexToBin() buffer
overflow
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RH-Author: Laszlo Ersek <lersek@redhat.com>
RH-MergeRequest: 5: NetworkPkg/IScsiDxe: fix IScsiHexToBin() security and functionality bugs [rhel-8.5.0, post-rebase]
RH-Commit: [9/10] acf102203198d575a12e5257c12b8e43ccdfc589
RH-Bugzilla: 1956408
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
The IScsiHexToBin() function documents the EFI_BUFFER_TOO_SMALL return
condition, but never actually checks whether the decoded buffer fits into
the caller-provided room (i.e., the input value of "BinLength"), and
EFI_BUFFER_TOO_SMALL is never returned. The decoding of "HexStr" can
overflow "BinBuffer".
This is remotely exploitable, as shown in a subsequent patch, which adds
error checking to the IScsiHexToBin() call sites. This issue allows the
target to compromise the initiator.
Introduce EFI_BAD_BUFFER_SIZE, in addition to the existent
EFI_BUFFER_TOO_SMALL, for reporting a special case of the buffer overflow,
plus actually catch the buffer overflow.
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3356
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210608121259.32451-10-lersek@redhat.com>
(cherry picked from commit 54e90edaed0d7c15230902ac4d74f4304bad2ebd)
---
NetworkPkg/IScsiDxe/IScsiMisc.c | 20 +++++++++++++++++---
NetworkPkg/IScsiDxe/IScsiMisc.h | 3 +++
2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.c b/NetworkPkg/IScsiDxe/IScsiMisc.c
index f0f4992b07..4069547867 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.c
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.c
@@ -377,6 +377,9 @@ IScsiBinToHex (
@retval EFI_SUCCESS The hexadecimal string is converted into a
binary encoded buffer.
@retval EFI_INVALID_PARAMETER Invalid hex encoding found in HexStr.
+ @retval EFI_BAD_BUFFER_SIZE The length of HexStr is too large for decoding:
+ the decoded size cannot be expressed in
+ BinLength on output.
@retval EFI_BUFFER_TOO_SMALL The binary buffer is too small to hold the
converted data.
**/
@@ -387,6 +390,8 @@ IScsiHexToBin (
IN CHAR8 *HexStr
)
{
+ UINTN BinLengthMin;
+ UINT32 BinLengthProvided;
UINTN Index;
UINTN Length;
UINT8 Digit;
@@ -409,6 +414,18 @@ IScsiHexToBin (
if (Length == 0 || Length % 2 != 0) {
return EFI_INVALID_PARAMETER;
}
+ //
+ // Check if the caller provides enough room for the decoded blob.
+ //
+ BinLengthMin = Length / 2;
+ if (BinLengthMin > MAX_UINT32) {
+ return EFI_BAD_BUFFER_SIZE;
+ }
+ BinLengthProvided = *BinLength;
+ *BinLength = (UINT32)BinLengthMin;
+ if (BinLengthProvided < BinLengthMin) {
+ return EFI_BUFFER_TOO_SMALL;
+ }
for (Index = 0; Index < Length; Index ++) {
TemStr[0] = HexStr[Index];
@@ -425,9 +442,6 @@ IScsiHexToBin (
BinBuffer [Index/2] = (UINT8) ((BinBuffer [Index/2] << 4) + Digit);
}
}
-
- *BinLength = (UINT32) ((Index + 1)/2);
-
return EFI_SUCCESS;
}
diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.h b/NetworkPkg/IScsiDxe/IScsiMisc.h
index 404a482e57..fddef4f466 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.h
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.h
@@ -172,6 +172,9 @@ IScsiBinToHex (
@retval EFI_SUCCESS The hexadecimal string is converted into a
binary encoded buffer.
@retval EFI_INVALID_PARAMETER Invalid hex encoding found in HexStr.
+ @retval EFI_BAD_BUFFER_SIZE The length of HexStr is too large for decoding:
+ the decoded size cannot be expressed in
+ BinLength on output.
@retval EFI_BUFFER_TOO_SMALL The binary buffer is too small to hold the
converted data.
**/
--
2.27.0