commit ba22e8f174309979d90047c5dc64fcb63bc2c32e
author Berker Peksag <berker.peksag@gmail.com> Tue Feb 25 06:19:03 2020 +0300
committer GitHub <noreply@github.com> Tue Feb 25 06:19:03 2020 +0300
tree fe5add86cf54ab65ba7fdc1cc48bc23685884835
parent 8af4712a16e4b7d1b60f1faec13cd7a88da95f6a

bpo-30566: Fix IndexError when using punycode codec (GH-18632)

Trying to decode an invalid string with the punycode codec
shoud raise UnicodeError.

Lib/encodings/punycode.py

diff --git a/Lib/encodings/punycode.py b/Lib/encodings/punycode.py
index 66c5101..1c57264 100644
--- a/Lib/encodings/punycode.py
+++ b/Lib/encodings/punycode.py
@@ -143,7 +143,7 @@
             digit = char - 22 # 0x30-26
         elif errors == "strict":
             raise UnicodeError("Invalid extended code point '%s'"
-                               % extended[extpos])
+                               % extended[extpos-1])
         else:
             return extpos, None
         t = T(j, bias)