[release-branch.go1.18] regexp: limit size of parsed regexps
Set a 128 MB limit on the amount of space used by []syntax.Inst
in the compiled form corresponding to a given regexp.
Also set a 128 MB limit on the rune storage in the *syntax.Regexp
tree itself.
Thanks to Adam Korczynski (ADA Logics) and OSS-Fuzz for reporting this issue.
Fixes CVE-2022-41715.
Updates #55949.
Fixes #55950.
Change-Id: Ia656baed81564436368cf950e1c5409752f28e1b
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1592136
TryBot-Result: Security TryBots <security-trybots@go-security-trybots.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/438501
Run-TryBot: Carlos Amedee <carlos@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/src/regexp/syntax/parse.go b/src/regexp/syntax/parse.go
index 0f6587a..df83980 100644
--- a/src/regexp/syntax/parse.go
+++ b/src/regexp/syntax/parse.go
@@ -90,15 +90,49 @@
// until we've allocated at least maxHeight Regexp structures.
const maxHeight = 1000
+// maxSize is the maximum size of a compiled regexp in Insts.
+// It too is somewhat arbitrarily chosen, but the idea is to be large enough
+// to allow significant regexps while at the same time small enough that
+// the compiled form will not take up too much memory.
+// 128 MB is enough for a 3.3 million Inst structures, which roughly
+// corresponds to a 3.3 MB regexp.
+const (
+ maxSize = 128 << 20 / instSize
+ instSize = 5 * 8 // byte, 2 uint32, slice is 5 64-bit words
+)
+
+// maxRunes is the maximum number of runes allowed in a regexp tree
+// counting the runes in all the nodes.
+// Ignoring character classes p.numRunes is always less than the length of the regexp.
+// Character classes can make it much larger: each \pL adds 1292 runes.
+// 128 MB is enough for 32M runes, which is over 26k \pL instances.
+// Note that repetitions do not make copies of the rune slices,
+// so \pL{1000} is only one rune slice, not 1000.
+// We could keep a cache of character classes we've seen,
+// so that all the \pL we see use the same rune list,
+// but that doesn't remove the problem entirely:
+// consider something like [\pL01234][\pL01235][\pL01236]...[\pL^&*()].
+// And because the Rune slice is exposed directly in the Regexp,
+// there is not an opportunity to change the representation to allow
+// partial sharing between different character classes.
+// So the limit is the best we can do.
+const (
+ maxRunes = 128 << 20 / runeSize
+ runeSize = 4 // rune is int32
+)
+
type parser struct {
flags Flags // parse mode flags
stack []*Regexp // stack of parsed expressions
free *Regexp
numCap int // number of capturing groups seen
wholeRegexp string
- tmpClass []rune // temporary char class work space
- numRegexp int // number of regexps allocated
- height map[*Regexp]int // regexp height for height limit check
+ tmpClass []rune // temporary char class work space
+ numRegexp int // number of regexps allocated
+ numRunes int // number of runes in char classes
+ repeats int64 // product of all repetitions seen
+ height map[*Regexp]int // regexp height, for height limit check
+ size map[*Regexp]int64 // regexp compiled size, for size limit check
}
func (p *parser) newRegexp(op Op) *Regexp {
@@ -122,6 +156,104 @@
p.free = re
}
+func (p *parser) checkLimits(re *Regexp) {
+ if p.numRunes > maxRunes {
+ panic(ErrInternalError)
+ }
+ p.checkSize(re)
+ p.checkHeight(re)
+}
+
+func (p *parser) checkSize(re *Regexp) {
+ if p.size == nil {
+ // We haven't started tracking size yet.
+ // Do a relatively cheap check to see if we need to start.
+ // Maintain the product of all the repeats we've seen
+ // and don't track if the total number of regexp nodes
+ // we've seen times the repeat product is in budget.
+ if p.repeats == 0 {
+ p.repeats = 1
+ }
+ if re.Op == OpRepeat {
+ n := re.Max
+ if n == -1 {
+ n = re.Min
+ }
+ if n <= 0 {
+ n = 1
+ }
+ if int64(n) > maxSize/p.repeats {
+ p.repeats = maxSize
+ } else {
+ p.repeats *= int64(n)
+ }
+ }
+ if int64(p.numRegexp) < maxSize/p.repeats {
+ return
+ }
+
+ // We need to start tracking size.
+ // Make the map and belatedly populate it
+ // with info about everything we've constructed so far.
+ p.size = make(map[*Regexp]int64)
+ for _, re := range p.stack {
+ p.checkSize(re)
+ }
+ }
+
+ if p.calcSize(re, true) > maxSize {
+ panic(ErrInternalError)
+ }
+}
+
+func (p *parser) calcSize(re *Regexp, force bool) int64 {
+ if !force {
+ if size, ok := p.size[re]; ok {
+ return size
+ }
+ }
+
+ var size int64
+ switch re.Op {
+ case OpLiteral:
+ size = int64(len(re.Rune))
+ case OpCapture, OpStar:
+ // star can be 1+ or 2+; assume 2 pessimistically
+ size = 2 + p.calcSize(re.Sub[0], false)
+ case OpPlus, OpQuest:
+ size = 1 + p.calcSize(re.Sub[0], false)
+ case OpConcat:
+ for _, sub := range re.Sub {
+ size += p.calcSize(sub, false)
+ }
+ case OpAlternate:
+ for _, sub := range re.Sub {
+ size += p.calcSize(sub, false)
+ }
+ if len(re.Sub) > 1 {
+ size += int64(len(re.Sub)) - 1
+ }
+ case OpRepeat:
+ sub := p.calcSize(re.Sub[0], false)
+ if re.Max == -1 {
+ if re.Min == 0 {
+ size = 2 + sub // x*
+ } else {
+ size = 1 + int64(re.Min)*sub // xxx+
+ }
+ break
+ }
+ // x{2,5} = xx(x(x(x)?)?)?
+ size = int64(re.Max)*sub + int64(re.Max-re.Min)
+ }
+
+ if size < 1 {
+ size = 1
+ }
+ p.size[re] = size
+ return size
+}
+
func (p *parser) checkHeight(re *Regexp) {
if p.numRegexp < maxHeight {
return
@@ -158,6 +290,7 @@
// push pushes the regexp re onto the parse stack and returns the regexp.
func (p *parser) push(re *Regexp) *Regexp {
+ p.numRunes += len(re.Rune)
if re.Op == OpCharClass && len(re.Rune) == 2 && re.Rune[0] == re.Rune[1] {
// Single rune.
if p.maybeConcat(re.Rune[0], p.flags&^FoldCase) {
@@ -189,7 +322,7 @@
}
p.stack = append(p.stack, re)
- p.checkHeight(re)
+ p.checkLimits(re)
return re
}
@@ -299,7 +432,7 @@
re.Sub = re.Sub0[:1]
re.Sub[0] = sub
p.stack[n-1] = re
- p.checkHeight(re)
+ p.checkLimits(re)
if op == OpRepeat && (min >= 2 || max >= 2) && !repeatIsValid(re, 1000) {
return "", &Error{ErrInvalidRepeatSize, before[:len(before)-len(after)]}
@@ -503,6 +636,7 @@
for j := start; j < i; j++ {
sub[j] = p.removeLeadingString(sub[j], len(str))
+ p.checkLimits(sub[j])
}
suffix := p.collapse(sub[start:i], OpAlternate) // recurse
@@ -560,6 +694,7 @@
for j := start; j < i; j++ {
reuse := j != start // prefix came from sub[start]
sub[j] = p.removeLeadingRegexp(sub[j], reuse)
+ p.checkLimits(sub[j])
}
suffix := p.collapse(sub[start:i], OpAlternate) // recurse
diff --git a/src/regexp/syntax/parse_test.go b/src/regexp/syntax/parse_test.go
index 1ef6d8a..67e3c56 100644
--- a/src/regexp/syntax/parse_test.go
+++ b/src/regexp/syntax/parse_test.go
@@ -484,12 +484,15 @@
`(?P<>a)`,
`[a-Z]`,
`(?i)[a-Z]`,
- `a{100000}`,
- `a{100000,}`,
- "((((((((((x{2}){2}){2}){2}){2}){2}){2}){2}){2}){2})",
- strings.Repeat("(", 1000) + strings.Repeat(")", 1000),
- strings.Repeat("(?:", 1000) + strings.Repeat(")*", 1000),
`\Q\E*`,
+ `a{100000}`, // too much repetition
+ `a{100000,}`, // too much repetition
+ "((((((((((x{2}){2}){2}){2}){2}){2}){2}){2}){2}){2})", // too much repetition
+ strings.Repeat("(", 1000) + strings.Repeat(")", 1000), // too deep
+ strings.Repeat("(?:", 1000) + strings.Repeat(")*", 1000), // too deep
+ "(" + strings.Repeat("(xx?)", 1000) + "){1000}", // too long
+ strings.Repeat("(xx?){1000}", 1000), // too long
+ strings.Repeat(`\pL`, 27000), // too many runes
}
var onlyPerl = []string{
