NetworkPkg/Dhcp6Dxe: Fix sanitizer issues

* EFI_DHCP6_DUID structure declares Duid[1], so the size
  of that structure is not large enough to hold an entire
  Duid. Instead, compute the correct size to allocate an
  EFI_DHCP6_DUID structure.
* Dhcp6AppendOption() takes a length parameter that in
  network order. Update test cases to make sure a network
  order length is passed in. A value of 0x0004 was being
  passed in and was then converted to 0x0400 length and
  buffer overflow was detected.

Signed-off-by: Michael D Kinney <[email protected]>

NetworkPkg/Dhcp6Dxe/GoogleTest/Dhcp6IoGoogleTest.cpp

@@ -161,7 +161,7 @@ TEST_F (Dhcp6AppendOptionTest, ValidDataExpectSuccess) {
   Packet->Length = sizeof (EFI_DHCP6_HEADER);
   OriginalLength = Packet->Length;
 
-  UntrustedDuid = (EFI_DHCP6_DUID *)AllocateZeroPool (sizeof (EFI_DHCP6_DUID));
+  UntrustedDuid = (EFI_DHCP6_DUID *)AllocateZeroPool (OFFSET_OF (EFI_DHCP6_DUID, Duid) + sizeof (Duid));
   ASSERT_NE (UntrustedDuid, (EFI_DHCP6_DUID *)NULL);
 
   UntrustedDuid->Length = NTOHS (sizeof (Duid));
@@ -763,7 +763,7 @@ TEST_F (Dhcp6SeekStsOptionTest, SeekIATAOptionExpectFail) {
              Dhcp6SeekStsOptionTest::Packet,
              &Option,
              Dhcp6OptStatusCode,
-             SearchPatternLength,
+             HTONS (SearchPatternLength),
              (UINT8 *)&SearchPattern
              );
   ASSERT_EQ (Status, EFI_SUCCESS);
@@ -815,7 +815,7 @@ TEST_F (Dhcp6SeekStsOptionTest, SeekIANAOptionExpectSuccess) {
              Dhcp6SeekStsOptionTest::Packet,
              &Option,
              Dhcp6OptStatusCode,
-             SearchPatternLength,
+             HTONS (SearchPatternLength),
              (UINT8 *)&SearchPattern
              );
   ASSERT_EQ (Status, EFI_SUCCESS);