Add hosts deserializer

jayvdb · Sep 7, 2020 · fc9ec20 · fc9ec20
1 parent a8ed923
commit fc9ec20
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Showing 4 changed files with 151 additions and 0 deletions.
diff --git a/dns_cache/hosts.py b/dns_cache/hosts.py
@@ -0,0 +1,125 @@
+from __future__ import absolute_import
+
+import os.path
+import sys
+from datetime import timedelta
+
+from dns.name import from_text
+from dns.rdataclass import IN
+from dns.rdatatype import A, AAAA
+
+from dns.resolver import Cache
+
+from reconfigure.configs import HostsConfig
+
+from .dnspython import create_answer, create_simple_rrset
+from .expiration import NoExpirationCacheBase
+from .persistence import _DeserializeOnGetCacheBase
+
+_year_in_seconds = timedelta(days=365).total_seconds()
+
+# References to https://en.wikipedia.org/wiki/Hosts_(file)
+_WINDOWS_PATHS = [
+    # Microsoft Windows NT, 2000, XP,[5] 2003, Vista, 2008, 7, 2012, 8, 10
+    r"${SystemRoot}\System32\drivers\etc\hosts",
+    # Microsoft Windows 95, 98, ME
+    r"${WinDir}\hosts",
+    # Microsoft Windows 3.1
+    r"${WinDir}\HOSTS",
+    # Symbian OS 6.1-9.0
+    r"C:\system\data\hosts",
+    # Symbian OS 9.1+
+    r"C:\private\10000882\hosts",
+]
+_UNIX_PATHS = [
+    # Unix, Unix-like, POSIX, Apple Macintosh Mac OS X 10.2 and newer,
+    # Android, iOS 2.0 and newer
+    "/etc/hosts",
+    # openSUSE
+    "/usr/etc/hosts",
+]
+_OTHER_PARTS = [
+    # Plan 9
+    "/lib/ndb/hosts",
+    # BeOS
+    "/boot/beos/etc/hosts",
+    # Haiku
+    "/boot/common/settings/network/hosts",
+]
+
+
+def guess_hosts_path():
+    if sys.platform == "win32":
+        possible_paths = _WINDOWS_PATHS + _UNIX_PATHS + _OTHER_PARTS
+    else:
+        possible_paths = _UNIX_PATHS + _OTHER_PARTS + _WINDOWS_PATHS
+
+    for path in possible_paths:
+        path = os.path.expandvars(os.path.expanduser(path))
+        if os.path.exists(path):
+            return path
+
+    raise RuntimeError()
+
+
+def _convert_entries(entries, expiration=None):
+    out_data = []
+
+    for entry in entries:
+        if ":" in entry.address:
+            rdtype = AAAA
+        elif "." in entry.address:
+            rdtype = A
+        else:
+            continue
+
+        names = [entry.name] + [
+            alias.name for alias in entry.aliases
+        ]
+        for name in names:
+            name = from_text(name)
+
+            ip = entry.address
+            rrset = create_simple_rrset(name, ip, rdtype, rdclass=IN)
+            rrset.ttl = _year_in_seconds
+            out_entry = create_answer(name, rrset)
+            if expiration:
+                out_entry.expiration = expiration
+
+            out_data.append(out_entry)
+
+    return out_data
+
+
+def loads(filename=None):
+    if not filename:
+        filename = guess_hosts_path()
+
+    mtime = os.path.getmtime(filename)
+
+    config = HostsConfig(path=filename)
+    config.load()
+
+    expiration = mtime + _year_in_seconds
+    dnspython_data = _convert_entries(config.tree.hosts, expiration)
+
+    return dnspython_data
+
+
+class HostsCacheBase(_DeserializeOnGetCacheBase, NoExpirationCacheBase):
+    def __init__(
+        self,
+        filename,
+        *args,
+        **kwargs
+    ):
+        super(HostsCacheBase, self).__init__(
+            *args,
+            filename=filename,
+            deserializer=loads,
+            **kwargs)
+
+
+class HostsCache(HostsCacheBase, Cache):
+    def __init__(self, *args, **kwargs):
+        super(HostsCache, self).__init__(*args, **kwargs)
diff --git a/setup.py b/setup.py
@@ -36,6 +36,7 @@
     install_requires=[
         "dnspython",
         "ProxyTypes",
+        "reconfigure",
     ],
     classifiers=classifiers.splitlines(),
 )
diff --git a/tests/test_hosts.py b/tests/test_hosts.py
@@ -0,0 +1,9 @@
+import unittest
+
+from dns_cache.hosts import loads
+
+
+class TestHostsSerializer(unittest.TestCase):
+    def test_loads(self):
+        data = loads()
+        assert data
diff --git a/tests/test_persistence.py b/tests/test_persistence.py
@@ -15,6 +15,7 @@
 except ImportError:
     apsw = None
 
+from dns_cache.hosts import HostsCache
 from dns_cache.diskcache import DiskCache, DiskLRUCache
 from dns_cache.pickle import PickableCache, PickableCacheBase, PickableLRUCache
 from dns_cache.sqlitedict import SqliteDictCache, SqliteDictLRUCache
@@ -241,6 +242,12 @@ def test_reload(self):
             q2.response = None
             q2.rrset = None
 
+        if isinstance(resolver.cache, HostsCache):
+            q1.expiration = None
+            q2.expiration = None
+
+            q1.response.id = q2.response.id
+
         compare_response(q1, q2)
 
         self.remove_cache()
@@ -252,6 +259,15 @@ class TestLRUPickling(TestPickling):
     kwargs = {"filename": os.path.abspath("dns-lru.pickle")}
 
 
+class TestHosts(TestPickling):
+
+    cache_cls = HostsCache
+    kwargs = {"filename": None}
+    query_name = "localhost."
+    load_on_get = True
+    seed_cache = lambda self, resolver: None
+
+
 class TestStashMemory(TestPickling):
 
     cache_cls = StashCache