From cf01b2dc8fc3ff9cf49fb891af5703dc03e3193e Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Tue, 8 Jun 2021 14:12:54 +0200
Subject: NetworkPkg/IScsiDxe: fix potential integer overflow in
 IScsiBinToHex()
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Considering IScsiBinToHex():

>   if (((*HexLength) - 3) < BinLength * 2) {
>     *HexLength = BinLength * 2 + 3;
>   }

the following subexpressions are problematic:

  (*HexLength) - 3
  BinLength * 2
  BinLength * 2 + 3

The first one may wrap under zero, the latter two may wrap over
MAX_UINT32.

Rewrite the calculation using SafeIntLib.

While at it, change the type of the "Index" variable from UINTN to UINT32.
The largest "Index"-based value that we calculate is

  Index * 2 + 2                                (with (Index == BinLength))

Because the patch makes

  BinLength * 2 + 3

safe to calculate in UINT32, using UINT32 for

  Index * 2 + 2                                (with (Index == BinLength))

is safe too. Consistently using UINT32 improves readability.

This patch is best reviewed with "git show -W".

The integer overflows that this patch fixes are theoretical; a subsequent
patch in the series will audit the IScsiBinToHex() call sites, and show
that none of them can fail.

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: <20210608121259.32451-6-lersek@redhat.com>
---
 NetworkPkg/IScsiDxe/IScsiDxe.inf |  1 +
 NetworkPkg/IScsiDxe/IScsiImpl.h  |  1 +
 NetworkPkg/IScsiDxe/IScsiMisc.c  | 19 +++++++++++++++----
 NetworkPkg/IScsiDxe/IScsiMisc.h  |  1 +
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/NetworkPkg/IScsiDxe/IScsiDxe.inf b/NetworkPkg/IScsiDxe/IScsiDxe.inf
index 543c408302..1dde56d00c 100644
--- a/NetworkPkg/IScsiDxe/IScsiDxe.inf
+++ b/NetworkPkg/IScsiDxe/IScsiDxe.inf
@@ -74,6 +74,7 @@
   MemoryAllocationLib
   NetLib
   PrintLib
+  SafeIntLib
   TcpIoLib
   UefiBootServicesTableLib
   UefiDriverEntryPoint
diff --git a/NetworkPkg/IScsiDxe/IScsiImpl.h b/NetworkPkg/IScsiDxe/IScsiImpl.h
index d895c7feb9..ac3a25730e 100644
--- a/NetworkPkg/IScsiDxe/IScsiImpl.h
+++ b/NetworkPkg/IScsiDxe/IScsiImpl.h
@@ -44,6 +44,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <Library/MemoryAllocationLib.h>
 #include <Library/NetLib.h>
 #include <Library/PrintLib.h>
+#include <Library/SafeIntLib.h>
 #include <Library/TcpIoLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/UefiHiiServicesLib.h>
diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.c b/NetworkPkg/IScsiDxe/IScsiMisc.c
index b8fef3ff6f..42988e15cb 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.c
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.c
@@ -316,6 +316,7 @@ IScsiMacAddrToStr (
   @retval EFI_SUCCESS          The binary data is converted to the hexadecimal string
                                and the length of the string is updated.
   @retval EFI_BUFFER_TOO_SMALL The string is too small.
+  @retval EFI_BAD_BUFFER_SIZE  BinLength is too large for hex encoding.
   @retval EFI_INVALID_PARAMETER The IP string is malformatted.
 
 **/
@@ -327,18 +328,28 @@ IScsiBinToHex (
   IN OUT UINT32 *HexLength
   )
 {
-  UINTN Index;
+  UINT32 HexLengthMin;
+  UINT32 HexLengthProvided;
+  UINT32 Index;
 
   if ((HexStr == NULL) || (BinBuffer == NULL) || (BinLength == 0)) {
     return EFI_INVALID_PARAMETER;
   }
 
-  if (((*HexLength) - 3) < BinLength * 2) {
-    *HexLength = BinLength * 2 + 3;
+  //
+  // Safely calculate: HexLengthMin := BinLength * 2 + 3.
+  //
+  if (RETURN_ERROR (SafeUint32Mult (BinLength, 2, &HexLengthMin)) ||
+      RETURN_ERROR (SafeUint32Add (HexLengthMin, 3, &HexLengthMin))) {
+    return EFI_BAD_BUFFER_SIZE;
+  }
+
+  HexLengthProvided = *HexLength;
+  *HexLength = HexLengthMin;
+  if (HexLengthProvided < HexLengthMin) {
     return EFI_BUFFER_TOO_SMALL;
   }
 
-  *HexLength = BinLength * 2 + 3;
   //
   // Prefix for Hex String.
   //
diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.h b/NetworkPkg/IScsiDxe/IScsiMisc.h
index 46c725aab3..231413993b 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.h
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.h
@@ -150,6 +150,7 @@ IScsiAsciiStrToIp (
   @retval EFI_SUCCESS          The binary data is converted to the hexadecimal string
                                and the length of the string is updated.
   @retval EFI_BUFFER_TOO_SMALL The string is too small.
+  @retval EFI_BAD_BUFFER_SIZE  BinLength is too large for hex encoding.
   @retval EFI_INVALID_PARAMETER The IP string is malformatted.
 
 **/
-- 
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