From ae18b325ffe5d77dc8ebde75ee765ae3dc1d50ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Eiras?= <joao.eiras@gmail.com>
Date: Tue, 8 Aug 2023 22:31:36 +0200
Subject: [PATCH] gh-107779: in datetime.fromisoformat, check the separator
 between date and time

---
 Lib/_pydatetime.py         | 7 ++++++-
 Lib/test/datetimetester.py | 3 +++
 Modules/_datetimemodule.c  | 6 ++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index f4fc2c58e5e2937..2aea449479797d8 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -1862,13 +1862,18 @@ def fromisoformat(cls, date_string):
         try:
             separator_location = _find_isoformat_datetime_separator(date_string)
             dstr = date_string[0:separator_location]
-            tstr = date_string[(separator_location+1):]
+            sep = date_string[separator_location:separator_location+1]
+            tstr = date_string[separator_location+1:]
 
             date_components = _parse_isoformat_date(dstr)
         except ValueError:
             raise ValueError(
                 f'Invalid isoformat string: {date_string!r}') from None
 
+        if sep and (_is_ascii_digit(sep) or not tstr):
+            # Date and time most likely split at the wrong place, indicates wrong format.
+            raise ValueError(f'Invalid isoformat string: {date_string!r}')
+
         if tstr:
             try:
                 time_components = _parse_isoformat_time(tstr)
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 55e061950ff2806..833d5c7d63487f1 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -1909,6 +1909,7 @@ def test_fromisoformat_fails(self):
             '2019-W53-1',       # No week 53 in 2019
             '2020-W54-1',       # No week 54
             '2009\ud80002\ud80028',     # Separators are surrogate codepoints
+            '2009-01-01 ',      # Trailing separator without time component
         ]
 
         for bad_str in bad_strs:
@@ -3295,6 +3296,8 @@ def test_fromisoformat_fails_datetime(self):
             '2009-04-19T12:30:45.123456-05:00a',    # Extra text
             '2009-04-19T12:30:45.123-05:00a',       # Extra text
             '2009-04-19T12:30:45-05:00a',           # Extra text
+            '2009-04-1912:30:45',           # Missing date-time separator 1
+            '20090419123054',               # Missing date-time separator 2
         ]
 
         for bad_str in bad_strs:
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 9002a1de7fb5b76..eb41200705fb733 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -5451,6 +5451,12 @@ datetime_fromisoformat(PyObject *cls, PyObject *dtstr)
     if (!rv && len > separator_location) {
         // In UTF-8, the length of multi-byte characters is encoded in the MSB
         p += separator_location;
+
+        if (is_digit(p[0])) {
+            // Date and time most likely split at the wrong place, indicates wrong format.
+            goto invalid_string_error;
+        }
+
         if ((p[0] & 0x80) == 0) {
             p += 1;
         }