Re: [edk2-devel] [PATCH v1] NetworkPkg/Ip6Dxe: Improve Neightbor Discovery message validation (CVE-2019-14559)

["Laszlo Ersek" <lersek@redhat.com>]

Jiaxin, Siyuan,

On 03/02/20 13:38, Maciej Rabeda wrote:
> 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>
> ---
>  NetworkPkg/Ip6Dxe/Ip6Nd.c     | 44 +++++++++------
>  NetworkPkg/Ip6Dxe/Ip6Nd.h     | 13 +++++
>  NetworkPkg/Ip6Dxe/Ip6Option.c | 57 +++++++++++++++-----
>  3 files changed, 83 insertions(+), 31 deletions(-)

can you please review this patch? It has spent 3+ weeks on the list.

Thanks,
Laszlo

> 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;
>