From: Alex Vandiver <alex@chmrr.net>
Date: Wed, 7 Apr 2021 20:11:15 +0000 (-0700)
Subject: is_valid_ip: Do not raise exceptions on too-long input.
X-Git-Tag: v6.2.0b1~44^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F3010%2Fhead;p=thirdparty%2Ftornado.git

is_valid_ip: Do not raise exceptions on too-long input.

is_valid_ip calls `socket.getaddrinfo` with `socket.AI_NUMERICHOST` on
the potential "ip"; even though IP addresses are not hostnames and do
not use the `idna` encoding, `socket.getaddrinfo` will raise
UnicodeError if the potential "ip" is longer than 63 characters long,
the RFC-mandated max hostname length.

Catch these UnicodeErrors and return false for too-long IPs, rather
than raising an exception.
---

diff --git a/tornado/netutil.py b/tornado/netutil.py
index f8a303805..15eea9704 100644
--- a/tornado/netutil.py
+++ b/tornado/netutil.py
@@ -301,6 +301,12 @@ def is_valid_ip(ip: str) -> bool:
         if e.args[0] == socket.EAI_NONAME:
             return False
         raise
+    except UnicodeError:
+        # `socket.getaddrinfo` will raise a UnicodeError from the
+        # `idna` decoder if the input is longer than 63 characters,
+        # even for socket.AI_NUMERICHOST.  See
+        # https://bugs.python.org/issue32958 for discussion
+        return False
     return True
 
 
diff --git a/tornado/test/netutil_test.py b/tornado/test/netutil_test.py
index f36b7c271..3911be6a2 100644
--- a/tornado/test/netutil_test.py
+++ b/tornado/test/netutil_test.py
@@ -204,6 +204,7 @@ class IsValidIPTest(unittest.TestCase):
         self.assertTrue(not is_valid_ip(" "))
         self.assertTrue(not is_valid_ip("\n"))
         self.assertTrue(not is_valid_ip("\x00"))
+        self.assertTrue(not is_valid_ip("a" * 100))
 
 
 class TestPortAllocation(unittest.TestCase):