Merge pull request kaitai-io#291 from NN---/patch-6

Support TXT, SRV and PTR records
riverloopsec · May 30, 2020 · 8678108 · 8678108
2 parents 0070bb7 + b6fb961
commit 8678108
Showing 1 changed file with 38 additions and 11 deletions.
diff --git a/network/dns_packet.ksy b/network/dns_packet.ksy
@@ -5,6 +5,7 @@ meta:
     rfc: 1035
   license: CC0-1.0
   endian: be
+  encoding: utf-8
 doc: |
   (No support for Auth-Name + Add-Name for simplicity)
 seq:
@@ -46,7 +47,7 @@ seq:
     repeat-expr: arcount
 types:
   query:
-    seq: 
+    seq:
       - id: name
         type: domain_name
       - id: type
@@ -71,19 +72,23 @@ types:
       - id: rdlength
         doc: "Length in octets of the following payload"
         type: u2
-      - id: ptrdname
-        type: domain_name
-        if: "type == type_type::ptr"
-      - id: address
-        type: address
-        if: "type == type_type::a"
+      - id: payload
+        size: rdlength
+        type:
+          switch-on: type
+          cases:
+            "type_type::ptr": domain_name
+            "type_type::a": address
+            "type_type::cname": domain_name
+            "type_type::srv": service
+            "type_type::txt": txt_body
   domain_name:
     seq:
       - id: name
         type: label
         repeat: until
         doc: "Repeat until the length is 0 or it is a pointer (bit-hack to get around lack of OR operator)"
-        repeat-until: "_.length == 0 or _.length == 0b1100_0000"
+        repeat-until: "_.length == 0 or _.length >= 192"
   label:
     seq:
       - id: length
@@ -96,11 +101,10 @@ types:
         if: "not is_pointer"
         doc: "Otherwise its a string the length of the length value"
         type: str
-        encoding: "ASCII"
         size: length
     instances:
       is_pointer:
-        value: length == 0b1100_0000
+        value: length >= 192
   pointer_struct:
     seq:
       - id: value
@@ -109,7 +113,7 @@ types:
     instances:
       contents:
         io: _root._io
-        pos: value
+        pos: value + ((_parent.length - 192) << 8)
         type: domain_name
   address:
     seq:
@@ -144,6 +148,28 @@ types:
         value: (flag & 0b0000_0000_0000_1111) >> 0
       is_opcode_valid:
         value: opcode == 0 or opcode == 1 or opcode == 2
+  service:
+    seq:
+      - id: priority
+        type: u2
+      - id: weight
+        type: u2
+      - id: port
+        type: u2
+      - id: target
+        type: domain_name
+  txt:
+    seq:
+      - id: length
+        type: u1
+      - id: text
+        type: str
+        size: length
+  txt_body:
+    seq:
+      - id: data
+        type: txt
+        repeat: eos
 
 enums:
   class_type:
@@ -168,3 +194,4 @@ enums:
     14: minfo
     15: mx
     16: txt
+    33: srv