Fix netlib.utils.is_valid_host

- Don't crash when passed an empty string. This translated into an actual core
crash, discovered while fuzzing with afl.
- Taking a slice of length one out of bytes returns an integer, so the check
for trailing period in this function never worked on Python3.
- Add unit tests.

1 files changed, 9 insertions, 0 deletions

diff --git a/test/netlib/http/http1/test_read.py b/test/netlib/http/http1/test_read.py
index c8a40ecb..44eff2ee 100644
--- a/test/netlib/http/http1/test_read.py
+++ b/test/netlib/http/http1/test_read.py
@@ -13,6 +13,7 @@ from netlib.http.http1.read import (
     _read_headers, _read_chunked, get_header_tokens
 )
 from netlib.tutils import treq, tresp, raises
+from netlib import exceptions
 
 
 def test_get_header_tokens():
@@ -42,6 +43,14 @@ def test_read_request(input):
     assert rfile.read() == b"skip"
 
 
+@pytest.mark.parametrize("input", [
+    b"CONNECT :0 0",
+])
+def test_read_request_error(input):
+    rfile = BytesIO(input)
+    raises(exceptions.HttpException, read_request, rfile)
+
+
 def test_read_request_head():
     rfile = BytesIO(
         b"GET / HTTP/1.1\r\n"