From f25f641513540845470ce34c489bea1cd8fecb93 Mon Sep 17 00:00:00 2001
From: Benjamin <bschwendemann@ernw.de>
Date: Sat, 31 Dec 2016 14:46:52 +0100
Subject: [PATCH] Fix issue #359 Handle ipv6 addresses according to RFC 5952
 Add regression tests

---
 scapy/pton_ntop.py  | 70 +++++++++++++++++++++++++++++++--------------
 test/regression.uts | 63 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+), 21 deletions(-)

diff --git a/scapy/pton_ntop.py b/scapy/pton_ntop.py
index 25f7ef98eff..64a5af41592 100644
--- a/scapy/pton_ntop.py
+++ b/scapy/pton_ntop.py
@@ -10,7 +10,7 @@
 without IPv6 support, on Windows for instance.
 """
 
-import socket,struct
+import socket,struct,re
 
 def inet_pton(af, addr):
     """Convert an IP address from text representation into binary form"""
@@ -77,25 +77,53 @@ def inet_ntop(af, addr):
         except AttributeError:
             pass
 
-        # IPv6 addresses have 128bits (16 bytes)
-        if len(addr) != 16:
+        return _ipv6_bin_to_str(addr)
+    else:
+        raise Exception("Address family not supported yet")
+
+
+def _ipv6_bin_to_str(addr):
+    # IPv6 addresses have 128bits (16 bytes)
+    if len(addr) != 16:
+        raise Exception("Illegal syntax for IP address")
+    parts = []
+    for left in [0, 2, 4, 6, 8, 10, 12, 14]:
+        try:
+            value = struct.unpack("!H", addr[left:left + 2])[0]
+            hexstr = hex(value)[2:]
+        except TypeError:
             raise Exception("Illegal syntax for IP address")
-        parts = []
-        for left in [0, 2, 4, 6, 8, 10, 12, 14]:
-            try: 
-                value = struct.unpack("!H", addr[left:left+2])[0]
-                hexstr = hex(value)[2:]
-            except TypeError:
-                raise Exception("Illegal syntax for IP address")
-            parts.append(hexstr.lstrip("0").lower())
-        result = ":".join(parts)
-        while ":::" in result:
-            result = result.replace(":::", "::")
-        # Leaving out leading and trailing zeros is only allowed with ::
-        if result.endswith(":") and not result.endswith("::"):
-            result = result + "0"
-        if result.startswith(":") and not result.startswith("::"):
-            result = "0" + result
-        return result
+        parts.append(hexstr.lower())
+
+    address = ":".join(parts)
+
+    # Find all consecutive zero blocks
+    matches = re.findall('(?::|^)(0(?::0)+)(?::|$)', address)
+    if matches:
+        # If multiple consecutive blocks have the same length, take the leftmost
+        match = max(matches)
+        if address.startswith(match):
+            leftidx = 0
+        else:
+            leftidx = address.find(':' + match) + 1
+        left = address[:leftidx]
+        rightidx = leftidx + len(match)
+
+        # Adrress is like abcd:ef01::
+        if len(address) == rightidx:
+            compact_address = left + ":"
+
+        # Adrress is like ::abcd:ef01
+        elif leftidx == 0:
+            compact_address = ":" + address[rightidx:]
+
+        # Adrress is like abcd::ef01
+        else:
+            compact_address = left + address[rightidx:]
+
+        # Special case: address full of zeros
+        if compact_address == ":":
+            compact_address = "::"
     else:
-        raise Exception("Address family not supported yet")   
+        compact_address = address
+    return compact_address
diff --git a/test/regression.uts b/test/regression.uts
index 41c640a052f..a8cee7f9ee1 100644
--- a/test/regression.uts
+++ b/test/regression.uts
@@ -6897,3 +6897,66 @@ x = f.i2repr(mp, {'*', '+', 'bit 2'})
 assert(re.match(r'^.*Star \(\*\).*$', x) is not None)
 assert(re.match(r'^.*Plus \(\+\).*$', x) is not None)
 assert(re.match(r'^.*bit 2.*$', x) is not None)
+
+###########################################################################################################
++ Test correct conversion from binary to string of IPv6 addresses
+
+= IPv6 bin to string conversion - all zero bytes
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' # All zero
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '::')
+
+= IPv6 bin to string conversion - non-compressable
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x11\x11\x22\x22\x33\x33\x44\x44\x55\x55\x66\x66\x77\x77\x88\x88' # Not compressable
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1111:2222:3333:4444:5555:6666:7777:8888')
+
+= IPv6 bin to string conversion - Zero-block right
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x11\x11\x22\x22\x33\x33\x44\x44\x55\x55\x00\x00\x00\x00\x00\x00' # Zeroblock right
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1111:2222:3333:4444:5555::')
+
+= IPv6 bin to string conversion - Zero-block left
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x00\x00\x00\x00\x00\x00\x44\x44\x55\x55\x66\x66\x77\x77\x88\x88' # Zeroblock left
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '::4444:5555:6666:7777:8888')
+
+= IPv6 bin to string conversion - Two zero-block with different length
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x00\x00\x00\x00\x33\x33\x44\x44\x00\x00\x00\x00\x00\x00\x88\x88' # Short and long zero block
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '0:0:3333:4444::8888')
+
+= IPv6 bin to string conversion - Address 1::
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' # only 1 on the left
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1::')
+
+= IPv6 bin to string conversion - Address ::1
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01' # loopback
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '::1')
+
+= IPv6 bin to string conversion - Zero-block of length 1
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x11\x11\x22\x22\x33\x33\x44\x44\x55\x55\x66\x66\x00\x00\x88\x88' # only one zero block
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1111:2222:3333:4444:5555:6666:0:8888')
+
+= IPv6 bin to string conversion - Two zero-blocks with equal length
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x11\x11\x00\x00\x00\x00\x44\x44\x00\x00\x00\x00\x77\x77\x88\x88' # two zero blocks of equal length
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1111::4444:0:0:7777:8888')
+
+= IPv6 bin to string conversion - Leading zero suppression
+from scapy.pton_ntop import _ipv6_bin_to_str
+address=b'\x10\x00\x02\x00\x00\x30\x00\x04\x00\x05\x00\x60\x07\x00\x80\x00' # Leading zero suppression
+compressed = _ipv6_bin_to_str(address)
+assert(compressed == '1000:200:30:4:5:60:700:8000')
\ No newline at end of file