Merge pull request #2 from cathugger/ipv6-tun

proper IPv6 option processing

llarp/net/ip.cpp

@@ -196,11 +196,11 @@ namespace llarp
 #undef SUB32CS
 
     static void
-    deltaChecksumIPv4TCP(byte_t *pld, ABSL_ATTRIBUTE_UNUSED size_t psz,
-                         size_t fragoff, size_t chksumoff, nuint32_t oSrcIP,
-                         nuint32_t oDstIP, nuint32_t nSrcIP, nuint32_t nDstIP)
+    deltaChecksumIPv4TCP(byte_t *pld, size_t psz, size_t fragoff,
+                         size_t chksumoff, nuint32_t oSrcIP, nuint32_t oDstIP,
+                         nuint32_t nSrcIP, nuint32_t nDstIP)
     {
-      if(fragoff > chksumoff)
+      if(fragoff > chksumoff || psz < chksumoff - fragoff + 2)
         return;
 
       auto check = (nuint16_t *)(pld + chksumoff - fragoff);
@@ -215,12 +215,12 @@ namespace llarp
     }
 
     static void
-    deltaChecksumIPv6TCP(byte_t *pld, ABSL_ATTRIBUTE_UNUSED size_t psz,
-                         size_t fragoff, size_t chksumoff,
-                         const uint32_t oSrcIP[4], const uint32_t oDstIP[4],
-                         const uint32_t nSrcIP[4], const uint32_t nDstIP[4])
+    deltaChecksumIPv6TCP(byte_t *pld, size_t psz, size_t fragoff,
+                         size_t chksumoff, const uint32_t oSrcIP[4],
+                         const uint32_t oDstIP[4], const uint32_t nSrcIP[4],
+                         const uint32_t nDstIP[4])
     {
-      if(fragoff > chksumoff)
+      if(fragoff > chksumoff || psz < chksumoff - fragoff + 2)
         return;
 
       auto check = (nuint16_t *)(pld + chksumoff - fragoff);
@@ -235,11 +235,11 @@ namespace llarp
     }
 
     static void
-    deltaChecksumIPv4UDP(byte_t *pld, ABSL_ATTRIBUTE_UNUSED size_t psz,
-                         size_t fragoff, nuint32_t oSrcIP, nuint32_t oDstIP,
-                         nuint32_t nSrcIP, nuint32_t nDstIP)
+    deltaChecksumIPv4UDP(byte_t *pld, size_t psz, size_t fragoff,
+                         nuint32_t oSrcIP, nuint32_t oDstIP, nuint32_t nSrcIP,
+                         nuint32_t nDstIP)
     {
-      if(fragoff > 6)
+      if(fragoff > 6 || psz < 6 + 2)
         return;
 
       auto check = (nuint16_t *)(pld + 6);
@@ -258,12 +258,11 @@ namespace llarp
     }
 
     static void
-    deltaChecksumIPv6UDP(byte_t *pld, ABSL_ATTRIBUTE_UNUSED size_t psz,
-                         size_t fragoff, const uint32_t oSrcIP[4],
-                         const uint32_t oDstIP[4], const uint32_t nSrcIP[4],
-                         const uint32_t nDstIP[4])
+    deltaChecksumIPv6UDP(byte_t *pld, size_t psz, size_t fragoff,
+                         const uint32_t oSrcIP[4], const uint32_t oDstIP[4],
+                         const uint32_t nSrcIP[4], const uint32_t nDstIP[4])
     {
-      if(fragoff > 6)
+      if(fragoff > 6 || psz < 6 + 2)
         return;
 
       auto check = (nuint16_t *)(pld + 6);
@@ -337,7 +336,7 @@ namespace llarp
     void
     IPPacket::UpdateIPv6Address(huint128_t src, huint128_t dst)
     {
-      const size_t ihs = 40;
+      const size_t ihs = 4 + 4 + 16 + 16;
 
       // XXX should've been checked at upper level?
       if(sz <= ihs)
@@ -357,11 +356,55 @@ namespace llarp
       const uint32_t *nDstIP = hdr->dstaddr.s6_addr32;
 
       // TODO IPv6 header options
-      auto pld             = buf + ihs;
-      auto psz             = sz - ihs;
-      const size_t fragoff = 0;
+      auto pld = buf + ihs;
+      auto psz = sz - ihs;
+
+      size_t fragoff = 0;
+      auto nextproto = hdr->proto;
+      for(;;)
+      {
+        switch(nextproto)
+        {
+          case 0:   // Hop-by-Hop Options
+          case 43:  // Routing Header
+          case 60:  // Destination Options
+          {
+            nextproto   = pld[0];
+            auto addlen = (size_t(pld[1]) + 1) * 8;
+            if(psz < addlen)
+              return;
+            pld += addlen;
+            psz -= addlen;
+            break;
+          }
+
+          case 44:  // Fragment Header
+            /*
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   |  Next Header  |   Reserved    |      Fragment Offset    |Res|M|
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   |                         Identification                        |
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+             */
+            nextproto = pld[0];
+            fragoff   = (uint16_t(pld[2]) << 8) | (uint16_t(pld[3]) & 0xFC);
+            if(psz < 8)
+              return;
+            pld += 8;
+            psz -= 8;
+
+            // jump straight to payload processing
+            if(fragoff != 0)
+              goto endprotohdrs;
+            break;
+
+          default:
+            goto endprotohdrs;
+        }
+      }
+    endprotohdrs:
 
-      switch(hdr->proto)
+      switch(nextproto)
       {
         case 6:  // TCP
           deltaChecksumIPv6TCP(pld, psz, fragoff, 16, oSrcIP, oDstIP, nSrcIP,