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regex-syntax: fix nest limit checker
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This commit fixes an embarrassing bug where the depth in the nest limit
checker was never decremented during postorder traversal, which means
long but shallow regexes would incorrectly trip the nest limit. We fix
that in this commit and add two regression tests.

Fixes #454
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@BurntSushi
BurntSushi committed Mar 10, 2018
1 parent 649762d commit a89220d
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8 changes: 8 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,3 +1,11 @@
TBD
===
Bug gixes:

* [BUG #454](https://github.com/rust-lang/regex/pull/454):
Fix a bug in the nest limit checker being too aggressive.


0.2.7 (2018-03-07)
==================
This release includes a ground-up rewrite of the regex-syntax crate, which has
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45 changes: 44 additions & 1 deletion regex-syntax/src/ast/parse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2106,7 +2106,7 @@ impl<'p, 's, P: Borrow<Parser>> NestLimiter<'p, 's, P> {
fn decrement_depth(&mut self) {
// Assuming the correctness of the visitor, this should never drop
// below 0.
self.depth.checked_sub(1).unwrap();
self.depth = self.depth.checked_sub(1).unwrap();
}
}

Expand Down Expand Up @@ -5254,4 +5254,47 @@ bar
],
})));
}

// This tests a bug fix where the nest limit checker wasn't decrementing
// its depth during post-traversal, which causes long regexes to trip
// the default limit too aggressively.
#[test]
fn regression_454_nest_too_big() {
let pattern = r#"
2(?:
[45]\d{3}|
7(?:
1[0-267]|
2[0-289]|
3[0-29]|
4[01]|
5[1-3]|
6[013]|
7[0178]|
91
)|
8(?:
0[125]|
[139][1-6]|
2[0157-9]|
41|
6[1-35]|
7[1-5]|
8[1-8]|
90
)|
9(?:
0[0-2]|
1[0-4]|
2[568]|
3[3-6]|
5[5-7]|
6[0167]|
7[15]|
8[0146-9]
)
)\d{4}
"#;
assert!(parser_nest_limit(pattern, 50).parse().is_ok());
}
}
296 changes: 296 additions & 0 deletions tests/crazy.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -103,3 +103,299 @@ fn dfa_handles_pathological_case() {
};
assert!(re.is_match(text!(&*text)));
}

#[test]
fn nest_limit_makes_it_parse() {
use regex::RegexBuilder;

RegexBuilder::new(
r#"
2(?:
[45]\d{3}|
7(?:
1[0-267]|
2[0-289]|
3[0-29]|
4[01]|
5[1-3]|
6[013]|
7[0178]|
91
)|
8(?:
0[125]|
[139][1-6]|
2[0157-9]|
41|
6[1-35]|
7[1-5]|
8[1-8]|
90
)|
9(?:
0[0-2]|
1[0-4]|
2[568]|
3[3-6]|
5[5-7]|
6[0167]|
7[15]|
8[0146-9]
)
)\d{4}|
3(?:
12?[5-7]\d{2}|
0(?:
2(?:
[025-79]\d|
[348]\d{1,2}
)|
3(?:
[2-4]\d|
[56]\d?
)
)|
2(?:
1\d{2}|
2(?:
[12]\d|
[35]\d{1,2}|
4\d?
)
)|
3(?:
1\d{2}|
2(?:
[2356]\d|
4\d{1,2}
)
)|
4(?:
1\d{2}|
2(?:
2\d{1,2}|
[47]|
5\d{2}
)
)|
5(?:
1\d{2}|
29
)|
[67]1\d{2}|
8(?:
1\d{2}|
2(?:
2\d{2}|
3|
4\d
)
)
)\d{3}|
4(?:
0(?:
2(?:
[09]\d|
7
)|
33\d{2}
)|
1\d{3}|
2(?:
1\d{2}|
2(?:
[25]\d?|
[348]\d|
[67]\d{1,2}
)
)|
3(?:
1\d{2}(?:
\d{2}
)?|
2(?:
[045]\d|
[236-9]\d{1,2}
)|
32\d{2}
)|
4(?:
[18]\d{2}|
2(?:
[2-46]\d{2}|
3
)|
5[25]\d{2}
)|
5(?:
1\d{2}|
2(?:
3\d|
5
)
)|
6(?:
[18]\d{2}|
2(?:
3(?:
\d{2}
)?|
[46]\d{1,2}|
5\d{2}|
7\d
)|
5(?:
3\d?|
4\d|
[57]\d{1,2}|
6\d{2}|
8
)
)|
71\d{2}|
8(?:
[18]\d{2}|
23\d{2}|
54\d{2}
)|
9(?:
[18]\d{2}|
2[2-5]\d{2}|
53\d{1,2}
)
)\d{3}|
5(?:
02[03489]\d{2}|
1\d{2}|
2(?:
1\d{2}|
2(?:
2(?:
\d{2}
)?|
[457]\d{2}
)
)|
3(?:
1\d{2}|
2(?:
[37](?:
\d{2}
)?|
[569]\d{2}
)
)|
4(?:
1\d{2}|
2[46]\d{2}
)|
5(?:
1\d{2}|
26\d{1,2}
)|
6(?:
[18]\d{2}|
2|
53\d{2}
)|
7(?:
1|
24
)\d{2}|
8(?:
1|
26
)\d{2}|
91\d{2}
)\d{3}|
6(?:
0(?:
1\d{2}|
2(?:
3\d{2}|
4\d{1,2}
)
)|
2(?:
2[2-5]\d{2}|
5(?:
[3-5]\d{2}|
7
)|
8\d{2}
)|
3(?:
1|
2[3478]
)\d{2}|
4(?:
1|
2[34]
)\d{2}|
5(?:
1|
2[47]
)\d{2}|
6(?:
[18]\d{2}|
6(?:
2(?:
2\d|
[34]\d{2}
)|
5(?:
[24]\d{2}|
3\d|
5\d{1,2}
)
)
)|
72[2-5]\d{2}|
8(?:
1\d{2}|
2[2-5]\d{2}
)|
9(?:
1\d{2}|
2[2-6]\d{2}
)
)\d{3}|
7(?:
(?:
02|
[3-589]1|
6[12]|
72[24]
)\d{2}|
21\d{3}|
32
)\d{3}|
8(?:
(?:
4[12]|
[5-7]2|
1\d?
)|
(?:
0|
3[12]|
[5-7]1|
217
)\d
)\d{4}|
9(?:
[35]1|
(?:
[024]2|
81
)\d|
(?:
1|
[24]1
)\d{2}
)\d{3}
"#
)
.build()
.unwrap();
}

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