NetworkPkg/DnsDxe: [CVE-2018-12178] Check the received packet size before parsing...

Fix CVE-2018-12178
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=809

The DNS driver only checks the received packet size against the
minimum DNS header size in DnsOnPacketReceived(), later it accesses
the QueryName and QuerySection beyond the header scope, which might
cause the pointer within DNS driver points to an invalid entry or
modifies the memory content beyond the header scope.

This patch is to fix above problem.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Wang Fan <fan.wang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Siyuan Fu <siyuan.fu@intel.com>

diff --git a/NetworkPkg/DnsDxe/DnsImpl.c b/NetworkPkg/DnsDxe/DnsImpl.c
index 89ea755cb2b95b094f81e76e352cb771e18a0e44..26a718987cc00451a782898ee2c9fae2b7661aeb 100644 (file)
--- a/NetworkPkg/DnsDxe/DnsImpl.c
+++ b/NetworkPkg/DnsDxe/DnsImpl.c
@@ -1114,6 +1114,7 @@ IsValidDnsResponse (
 \r
   @param  Instance              The DNS instance\r
   @param  RxString              Received buffer.\r
+  @param  Length                Received buffer length.\r
   @param  Completed             Flag to indicate that Dns response is valid.\r
 \r
   @retval EFI_SUCCESS           Parse Dns Response successfully.\r
@@ -1124,12 +1125,14 @@ EFI_STATUS
 ParseDnsResponse (\r
   IN OUT DNS_INSTANCE              *Instance,\r
   IN     UINT8                     *RxString,\r
+  IN     UINT32                    Length,\r
      OUT BOOLEAN                   *Completed\r
   )\r
 {\r
   DNS_HEADER            *DnsHeader;\r
 \r
   CHAR8                 *QueryName;\r
+  UINT32                QueryNameLen;\r
   DNS_QUERY_SECTION     *QuerySection;\r
 \r
   CHAR8                 *AnswerName;\r
@@ -1155,6 +1158,7 @@ ParseDnsResponse (
   DNS6_RESOURCE_RECORD  *Dns6RR;\r
 \r
   EFI_STATUS            Status;\r
+  UINT32                RemainingLength;\r
 \r
   EFI_TPL               OldTpl;\r
 \r
@@ -1178,6 +1182,17 @@ ParseDnsResponse (
 \r
   *Completed       = TRUE;\r
   Status           = EFI_SUCCESS;\r
+  RemainingLength  = Length;\r
+\r
+  //\r
+  // Check whether the remaining packet length is avaiable or not.\r
+  //\r
+  if (RemainingLength <= sizeof (DNS_HEADER)) {\r
+    *Completed = FALSE;\r
+    return EFI_ABORTED;\r
+  } else {\r
+    RemainingLength -= sizeof (DNS_HEADER);\r
+  }\r
 \r
   //\r
   // Get header\r
@@ -1191,22 +1206,38 @@ ParseDnsResponse (
   DnsHeader->AuthorityNum = NTOHS (DnsHeader->AuthorityNum);\r
   DnsHeader->AditionalNum = NTOHS (DnsHeader->AditionalNum);\r
 \r
+  //\r
+  // There is always one QuestionsNum in DNS message. The capability to handle more\r
+  // than one requires to redesign the message format. Currently, it's not supported.\r
+  //\r
+  if (DnsHeader->QuestionsNum > 1) {\r
+    *Completed = FALSE;\r
+    return EFI_UNSUPPORTED;\r
+  }\r
+\r
   //\r
   // Get Query name\r
   //\r
   QueryName = (CHAR8 *) (RxString + sizeof (*DnsHeader));\r
 \r
+  QueryNameLen = (UINT32) AsciiStrLen (QueryName) + 1;\r
+\r
   //\r
-  // Get query section\r
+  // Check whether the remaining packet length is avaiable or not.\r
   //\r
-  QuerySection = (DNS_QUERY_SECTION *) (QueryName + AsciiStrLen (QueryName) + 1);\r
-  QuerySection->Type = NTOHS (QuerySection->Type);\r
-  QuerySection->Class = NTOHS (QuerySection->Class);\r
+  if (RemainingLength <= QueryNameLen + sizeof (DNS_QUERY_SECTION)) {\r
+    *Completed = FALSE;\r
+    return EFI_ABORTED;\r
+  } else {\r
+    RemainingLength -= (QueryNameLen + sizeof (DNS_QUERY_SECTION));\r
+  }\r
 \r
   //\r
-  // Get Answer name\r
+  // Get query section\r
   //\r
-  AnswerName = (CHAR8 *) QuerySection + sizeof (*QuerySection);\r
+  QuerySection = (DNS_QUERY_SECTION *) (QueryName + QueryNameLen);\r
+  QuerySection->Type = NTOHS (QuerySection->Type);\r
+  QuerySection->Class = NTOHS (QuerySection->Class);\r
 \r
   OldTpl = gBS->RaiseTPL (TPL_CALLBACK);\r
 \r
@@ -1341,10 +1372,26 @@ ParseDnsResponse (
 \r
   Status = EFI_NOT_FOUND;\r
 \r
+  //\r
+  // Get Answer name\r
+  //\r
+  AnswerName = (CHAR8 *) QuerySection + sizeof (*QuerySection);\r
+\r
   //\r
   // Processing AnswerSection.\r
   //\r
   while (AnswerSectionNum < DnsHeader->AnswersNum) {\r
+    //\r
+    // Check whether the remaining packet length is avaiable or not.\r
+    //\r
+    if (RemainingLength <= sizeof (UINT16) + sizeof (DNS_ANSWER_SECTION)) {\r
+      *Completed = FALSE;\r
+      Status = EFI_ABORTED;\r
+      goto ON_EXIT;\r
+    } else {\r
+      RemainingLength -= (sizeof (UINT16) + sizeof (DNS_ANSWER_SECTION));\r
+    }\r
+\r
     //\r
     // Answer name should be PTR, else EFI_UNSUPPORTED returned.\r
     //\r
@@ -1362,6 +1409,17 @@ ParseDnsResponse (
     AnswerSection->Ttl = NTOHL (AnswerSection->Ttl);\r
     AnswerSection->DataLength = NTOHS (AnswerSection->DataLength);\r
 \r
+    //\r
+    // Check whether the remaining packet length is avaiable or not.\r
+    //\r
+    if (RemainingLength < AnswerSection->DataLength) {\r
+      *Completed = FALSE;\r
+      Status = EFI_ABORTED;\r
+      goto ON_EXIT;\r
+    } else {\r
+      RemainingLength -= AnswerSection->DataLength;\r
+    }\r
+\r
     //\r
     // Check whether it's the GeneralLookUp querying.\r
     //\r
@@ -1733,6 +1791,7 @@ DnsOnPacketReceived (
   DNS_INSTANCE              *Instance;\r
 \r
   UINT8                     *RcvString;\r
+  UINT32                    Len;\r
 \r
   BOOLEAN                   Completed;\r
 \r
@@ -1748,9 +1807,7 @@ DnsOnPacketReceived (
 \r
   ASSERT (Packet != NULL);\r
 \r
-  if (Packet->TotalSize <= sizeof (DNS_HEADER)) {\r
-    goto ON_EXIT;\r
-  }\r
+  Len = Packet->TotalSize;\r
 \r
   RcvString = NetbufGetByte (Packet, 0, NULL);\r
   ASSERT (RcvString != NULL);\r
@@ -1758,7 +1815,7 @@ DnsOnPacketReceived (
   //\r
   // Parse Dns Response\r
   //\r
-  ParseDnsResponse (Instance, RcvString, &Completed);\r
+  ParseDnsResponse (Instance, RcvString, Len, &Completed);\r
 \r
 ON_EXIT:\r
 \r

diff --git a/NetworkPkg/DnsDxe/DnsImpl.h b/NetworkPkg/DnsDxe/DnsImpl.h
index 90dc0549038428859190500088263a6f1d92affa..45feca21602c08e953fd956fd9b1db0cfb251610 100644 (file)
--- a/NetworkPkg/DnsDxe/DnsImpl.h
+++ b/NetworkPkg/DnsDxe/DnsImpl.h
@@ -583,6 +583,7 @@ IsValidDnsResponse (
 \r
   @param  Instance              The DNS instance\r
   @param  RxString              Received buffer.\r
+  @param  Length                Received buffer length.\r
   @param  Completed             Flag to indicate that Dns response is valid.\r
 \r
   @retval EFI_SUCCESS           Parse Dns Response successfully.\r
@@ -593,6 +594,7 @@ EFI_STATUS
 ParseDnsResponse (\r
   IN OUT DNS_INSTANCE              *Instance,\r
   IN     UINT8                     *RxString,\r
+  IN     UINT32                    Length,\r
      OUT BOOLEAN                   *Completed\r
   );\r
 \r