[PATCH v2] NetworkPkg/Ip6Dxe: Improve Neightbor Discovery message validation.

["Maciej Rabeda" <maciej.rabeda@linux.intel.com>]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2174

Problem has been identified with Ip6ProcessRouterAdvertise() when
Router Advertise packet contains options with malicious/invalid
'Length' field. This can lead to platform entering infinite loop
when processing options from that packet.

Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Signed-off-by: Maciej Rabeda <maciej.rabeda@linux.intel.com>
Reviewed-by: Siyuan Fu <siyuan.fu@intel.com>
---
 NetworkPkg/Ip6Dxe/Ip6Nd.c     | 44 +++++++++------
 NetworkPkg/Ip6Dxe/Ip6Nd.h     | 13 +++++
 NetworkPkg/Ip6Dxe/Ip6Option.c | 57 +++++++++++++++-----
 3 files changed, 83 insertions(+), 31 deletions(-)

diff --git a/NetworkPkg/Ip6Dxe/Ip6Nd.c b/NetworkPkg/Ip6Dxe/Ip6Nd.c
index 4288ef02dd46..fd7f60b2f92c 100644
--- a/NetworkPkg/Ip6Dxe/Ip6Nd.c
+++ b/NetworkPkg/Ip6Dxe/Ip6Nd.c
@@ -1927,7 +1927,7 @@ Ip6ProcessRouterAdvertise (
   UINT32                    ReachableTime;
   UINT32                    RetransTimer;
   UINT16                    RouterLifetime;
-  UINT16                    Offset;
+  UINT32                    Offset;
   UINT8                     Type;
   UINT8                     Length;
   IP6_ETHER_ADDR_OPTION     LinkLayerOption;
@@ -2094,10 +2094,11 @@ Ip6ProcessRouterAdvertise (
   //
   // The only defined options that may appear are the Source
   // Link-Layer Address, Prefix information and MTU options.
-  // All included options have a length that is greater than zero.
+  // All included options have a length that is greater than zero and
+  // fit within the input packet.
   //
   Offset = 16;
-  while (Offset < Head->PayloadLength) {
+  while (Offset < (UINT32) Head->PayloadLength) {
     NetbufCopy (Packet, Offset, sizeof (UINT8), &Type);
     switch (Type) {
     case Ip6OptionEtherSource:
@@ -2105,9 +2106,12 @@ Ip6ProcessRouterAdvertise (
       // Update the neighbor cache
       //
       NetbufCopy (Packet, Offset, sizeof (IP6_ETHER_ADDR_OPTION), (UINT8 *) &LinkLayerOption);
-      if (LinkLayerOption.Length <= 0) {
-        goto Exit;
-      }
+
+      //
+      // Option size validity ensured by Ip6IsNDOptionValid().
+      //
+      ASSERT (LinkLayerOption.Length != 0);
+      ASSERT (Offset + (UINT32) LinkLayerOption.Length * 8 >= (UINT32) Head->PayloadLength);
 
       ZeroMem (&LinkLayerAddress, sizeof (EFI_MAC_ADDRESS));
       CopyMem (&LinkLayerAddress, LinkLayerOption.EtherAddr, 6);
@@ -2151,13 +2155,17 @@ Ip6ProcessRouterAdvertise (
         }
       }
 
-      Offset = (UINT16) (Offset + (UINT16) LinkLayerOption.Length * 8);
+      Offset += (UINT32) LinkLayerOption.Length * 8;
       break;
     case Ip6OptionPrefixInfo:
       NetbufCopy (Packet, Offset, sizeof (IP6_PREFIX_INFO_OPTION), (UINT8 *) &PrefixOption);
-      if (PrefixOption.Length != 4) {
-        goto Exit;
-      }
+
+      //
+      // Option size validity ensured by Ip6IsNDOptionValid().
+      //
+      ASSERT (PrefixOption.Length == 4);
+      ASSERT (Offset + (UINT32) PrefixOption.Length * 8 >= (UINT32) Head->PayloadLength);
+
       PrefixOption.ValidLifetime     = NTOHL (PrefixOption.ValidLifetime);
       PrefixOption.PreferredLifetime = NTOHL (PrefixOption.PreferredLifetime);
 
@@ -2321,9 +2329,12 @@ Ip6ProcessRouterAdvertise (
       break;
     case Ip6OptionMtu:
       NetbufCopy (Packet, Offset, sizeof (IP6_MTU_OPTION), (UINT8 *) &MTUOption);
-      if (MTUOption.Length != 1) {
-        goto Exit;
-      }
+
+      //
+      // Option size validity ensured by Ip6IsNDOptionValid().
+      //
+      ASSERT (MTUOption.Length == 1);
+      ASSERT (Offset + (UINT32) MTUOption.Length * 8 >= (UINT32) Head->PayloadLength);
 
       //
       // Use IPv6 minimum link MTU 1280 bytes as the maximum packet size in order
@@ -2338,11 +2349,10 @@ Ip6ProcessRouterAdvertise (
       // Silently ignore unrecognized options
       //
       NetbufCopy (Packet, Offset + sizeof (UINT8), sizeof (UINT8), &Length);
-      if (Length <= 0) {
-        goto Exit;
-      }
 
-      Offset = (UINT16) (Offset + (UINT16) Length * 8);
+      ASSERT (Length != 0);
+
+      Offset += (UINT32) Length * 8;
       break;
     }
   }
diff --git a/NetworkPkg/Ip6Dxe/Ip6Nd.h b/NetworkPkg/Ip6Dxe/Ip6Nd.h
index 560dfa343782..5f1bd6fb922a 100644
--- a/NetworkPkg/Ip6Dxe/Ip6Nd.h
+++ b/NetworkPkg/Ip6Dxe/Ip6Nd.h
@@ -56,12 +56,21 @@ VOID
   VOID                      *Context
   );
 
+typedef struct _IP6_OPTION_HEADER {
+  UINT8                     Type;
+  UINT8                     Length;
+} IP6_OPTION_HEADER;
+
+STATIC_ASSERT (sizeof (IP6_OPTION_HEADER) == 2, "IP6_OPTION_HEADER is expected to be exactly 2 bytes long.");
+
 typedef struct _IP6_ETHE_ADDR_OPTION {
   UINT8                     Type;
   UINT8                     Length;
   UINT8                     EtherAddr[6];
 } IP6_ETHER_ADDR_OPTION;
 
+STATIC_ASSERT (sizeof (IP6_ETHER_ADDR_OPTION) == 8, "IP6_ETHER_ADDR_OPTION is expected to be exactly 8 bytes long.");
+
 typedef struct _IP6_MTU_OPTION {
   UINT8                     Type;
   UINT8                     Length;
@@ -69,6 +78,8 @@ typedef struct _IP6_MTU_OPTION {
   UINT32                    Mtu;
 } IP6_MTU_OPTION;
 
+STATIC_ASSERT (sizeof (IP6_MTU_OPTION) == 8, "IP6_MTU_OPTION is expected to be exactly 8 bytes long.");
+
 typedef struct _IP6_PREFIX_INFO_OPTION {
   UINT8                     Type;
   UINT8                     Length;
@@ -80,6 +91,8 @@ typedef struct _IP6_PREFIX_INFO_OPTION {
   EFI_IPv6_ADDRESS          Prefix;
 } IP6_PREFIX_INFO_OPTION;
 
+STATIC_ASSERT (sizeof (IP6_PREFIX_INFO_OPTION) == 32, "IP6_PREFIX_INFO_OPTION is expected to be exactly 32 bytes long.");
+
 typedef
 VOID
 (*IP6_DAD_CALLBACK) (
diff --git a/NetworkPkg/Ip6Dxe/Ip6Option.c b/NetworkPkg/Ip6Dxe/Ip6Option.c
index 4d92a852dc86..6b4b029d1479 100644
--- a/NetworkPkg/Ip6Dxe/Ip6Option.c
+++ b/NetworkPkg/Ip6Dxe/Ip6Option.c
@@ -129,45 +129,74 @@ Ip6IsNDOptionValid (
   IN UINT16                 OptionLen
   )
 {
-  UINT16                    Offset;
-  UINT8                     OptionType;
+  UINT32                    Offset;
   UINT16                    Length;
+  IP6_OPTION_HEADER         *OptionHeader;
+
+  if (Option == NULL) {
+    ASSERT (Option != NULL);
+    return FALSE;
+  }
 
   Offset = 0;
 
-  while (Offset < OptionLen) {
-    OptionType = *(Option + Offset);
-     Length    = (UINT16) (*(Option + Offset + 1) * 8);
+  //
+  // RFC 4861 states that Neighbor Discovery packet can contain zero or more
+  // options. Start processing the options if at least Type + Length fields
+  // fit within the input buffer.
+  //
+  while (Offset + sizeof (IP6_OPTION_HEADER) - 1 < OptionLen) {
+    OptionHeader  = (IP6_OPTION_HEADER*) (Option + Offset);
+    Length        = (UINT16) OptionHeader->Length * 8;
 
-    switch (OptionType) {
+    switch (OptionHeader->Type) {
     case Ip6OptionPrefixInfo:
       if (Length != 32) {
         return FALSE;
       }
-
       break;
 
     case Ip6OptionMtu:
       if (Length != 8) {
         return FALSE;
       }
-
       break;
 
     default:
-      //
-      // Check the length of Ip6OptionEtherSource, Ip6OptionEtherTarget, and
-      // Ip6OptionRedirected here. For unrecognized options, silently ignore
-      // and continue processing the message.
-      //
+      // RFC 4861 states that Length field cannot be 0.
       if (Length == 0) {
         return FALSE;
       }
+      break;
+    }
+
+    //
+    // Check whether recognized options are within the input buffer's scope.
+    //
+    switch (OptionHeader->Type) {
+    case Ip6OptionEtherSource:
+    case Ip6OptionEtherTarget:
+    case Ip6OptionPrefixInfo:
+    case Ip6OptionRedirected:
+    case Ip6OptionMtu:
+      if (Offset + Length > (UINT32) OptionLen) {
+        return FALSE;
+      }
+      break;
 
+    default:
+      //
+      // Unrecognized options can be either valid (but unused) or invalid
+      // (garbage in between or right after valid options). Silently ignore.
+      //
       break;
     }
 
-    Offset = (UINT16) (Offset + Length);
+    //
+    // Advance to the next option.
+    // Length already considers option header's Type + Length.
+    //
+    Offset += Length;
   }
 
   return TRUE;
-- 
2.24.0.windows.2