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performance improvements in ReDoSUtil

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This commit is contained in:
Erik Krogh Kristensen
2021-08-12 18:26:39 +02:00
parent 49e47641e4
commit 3f7f5d2418
2 changed files with 32 additions and 24 deletions
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28
javascript/ql/src/semmle/javascript/security/performance/ReDoSUtil.qll
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@@ -155,15 +155,22 @@ private class RegexpCharacterConstant extends RegExpConstant {
RegexpCharacterConstant() { this.isCharacter() }
}
/**
* A regexp term that is relevant for this ReDoS analysis.
*/
class RelevantRegExpTerm extends RegExpTerm {
RelevantRegExpTerm() { getRoot(this).isRelevant() }
}
/**
* Holds if `term` is the chosen canonical representative for all terms with string representation `str`.
*
* Using canonical representatives gives a huge performance boost when working with tuples containing multiple `InputSymbol`s.
* The number of `InputSymbol`s is decreased by 3 orders of magnitude or more in some larger benchmarks.
*/
private predicate isCanonicalTerm(RegExpTerm term, string str) {
private predicate isCanonicalTerm(RelevantRegExpTerm term, string str) {
term =
rank[1](RegExpTerm t, Location loc, File file |
min(RelevantRegExpTerm t, Location loc, File file |
loc = t.getLocation() and
file = t.getFile() and
str = t.getRawValue()
@@ -178,15 +185,15 @@ private predicate isCanonicalTerm(RegExpTerm term, string str) {
private newtype TInputSymbol =
/** An input symbol corresponding to character `c`. */
Char(string c) {
c = any(RegexpCharacterConstant cc | getRoot(cc).isRelevant()).getValue().charAt(_)
c = any(RegexpCharacterConstant cc | cc instanceof RelevantRegExpTerm).getValue().charAt(_)
} or
/**
* An input symbol representing all characters matched by
* a (non-universal) character class that has string representation `charClassString`.
*/
CharClass(string charClassString) {
exists(RegExpTerm term | term.getRawValue() = charClassString | getRoot(term).isRelevant()) and
exists(RegExpTerm recc | isCanonicalTerm(recc, charClassString) |
exists(RelevantRegExpTerm term | term.getRawValue() = charClassString) and
exists(RelevantRegExpTerm recc | isCanonicalTerm(recc, charClassString) |
recc instanceof RegExpCharacterClass and
not recc.(RegExpCharacterClass).isUniversalClass()
or
@@ -626,13 +633,10 @@ RegExpRoot getRoot(RegExpTerm term) {
}
private newtype TState =
Match(RegExpTerm t, int i) {
getRoot(t).isRelevant() and
(
i = 0
or
exists(t.(RegexpCharacterConstant).getValue().charAt(i))
)
Match(RelevantRegExpTerm t, int i) {
i = 0
or
exists(t.(RegexpCharacterConstant).getValue().charAt(i))
} or
Accept(RegExpRoot l) { l.isRelevant() } or
AcceptAnySuffix(RegExpRoot l) { l.isRelevant() }