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Issue #9669: Protect re against infinite loops on zero-width matching in 

non-greedy repeat.  Patch by Matthew Barnett.
This commit is contained in:
Serhiy Storchaka 2013-02-16 21:23:01 +02:00
parent e18e05cce9
commit 6a8e2b4982
3 changed files with 19 additions and 2 deletions
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9
Lib/test/test_re.py
View File

@ -628,6 +628,15 @@ class ReTests(unittest.TestCase):
self.assertEqual(re.match('(x)*y', 50000*'x'+'y').group(1), 'x')
self.assertEqual(re.match('(x)*?y', 50000*'x'+'y').group(1), 'x')
def test_unlimited_zero_width_repeat(self):
# Issue #9669
self.assertIsNone(re.match(r'(?:a?)*y', 'z'))
self.assertIsNone(re.match(r'(?:a?)+y', 'z'))
self.assertIsNone(re.match(r'(?:a?){2,}y', 'z'))
self.assertIsNone(re.match(r'(?:a?)*?y', 'z'))
self.assertIsNone(re.match(r'(?:a?)+?y', 'z'))
self.assertIsNone(re.match(r'(?:a?){2,}?y', 'z'))
def test_scanner(self):
def s_ident(scanner, token): return token
def s_operator(scanner, token): return "op%s" % token

3
Misc/NEWS
View File

@ -205,6 +205,9 @@ Core and Builtins
Library
-------
- Issue #9669: Protect re against infinite loops on zero-width matching in
non-greedy repeat. Patch by Matthew Barnett.
- Issue #13169: The maximal repetition number in a regular expression has been
increased from 65534 to 2147483647 (on 32-bit platform) or 4294967294 (on
64-bit).

9
Modules/_sre.c
View File

@ -1302,13 +1302,18 @@ entrance:
LASTMARK_RESTORE();
if (ctx->count >= ctx->u.rep->pattern[2]
&& ctx->u.rep->pattern[2] != SRE_MAXREPEAT)
if ((ctx->count >= ctx->u.rep->pattern[2]
&& ctx->u.rep->pattern[2] != SRE_MAXREPEAT) ||
state->ptr == ctx->u.rep->last_ptr)
RETURN_FAILURE;
ctx->u.rep->count = ctx->count;
/* zero-width match protection */
DATA_PUSH(&ctx->u.rep->last_ptr);
ctx->u.rep->last_ptr = state->ptr;
DO_JUMP(JUMP_MIN_UNTIL_3,jump_min_until_3,
ctx->u.rep->pattern+3);
DATA_POP(&ctx->u.rep->last_ptr);
if (ret) {
RETURN_ON_ERROR(ret);
RETURN_SUCCESS;