path/filepath: fix stack exhaustion in Glob

A limit is added to the number of path separators allowed by an input to
Glob, to prevent stack exhaustion issues.

Thanks to Juho Nurminen of Mattermost who reported the issue.

Fixes CVE-2022-30632
Fixes #53416

Change-Id: I1b9fd4faa85411a05dbc91dceae1c0c8eb021f07
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1498176
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/417066
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>

diff --git a/src/path/filepath/match.go b/src/path/filepath/match.go
index 847a78133d3d4c157d776dd619a36e27c1b0ce23..b5cc4b8cf3fc32c09101e3d3008cd1db4ec769f8 100644 (file)
--- a/src/path/filepath/match.go
+++ b/src/path/filepath/match.go
@@ -240,6 +240,16 @@ func getEsc(chunk string) (r rune, nchunk string, err error) {
 // The only possible returned error is ErrBadPattern, when pattern
 // is malformed.
 func Glob(pattern string) (matches []string, err error) {
+       return globWithLimit(pattern, 0)
+}
+
+func globWithLimit(pattern string, depth int) (matches []string, err error) {
+       // This limit is used prevent stack exhaustion issues. See CVE-2022-30632.
+       const pathSeparatorsLimit = 10000
+       if depth == pathSeparatorsLimit {
+               return nil, ErrBadPattern
+       }
+
        // Check pattern is well-formed.
        if _, err := Match(pattern, ""); err != nil {
                return nil, err
@@ -269,7 +279,7 @@ func Glob(pattern string) (matches []string, err error) {
        }
 
        var m []string
-       m, err = Glob(dir)
+       m, err = globWithLimit(dir, depth+1)
        if err != nil {
                return
        }

diff --git a/src/path/filepath/match_test.go b/src/path/filepath/match_test.go
index 375c41a7e9d5d06615ba59451850bc8c552b45a9..d6282596fedbb93aeabc93fdc8029d43266098ae 100644 (file)
--- a/src/path/filepath/match_test.go
+++ b/src/path/filepath/match_test.go
@@ -155,6 +155,16 @@ func TestGlob(t *testing.T) {
        }
 }
 
+func TestCVE202230632(t *testing.T) {
+       // Prior to CVE-2022-30632, this would cause a stack exhaustion given a
+       // large number of separators (more than 4,000,000). There is now a limit
+       // of 10,000.
+       _, err := Glob("/*" + strings.Repeat("/", 10001))
+       if err != ErrBadPattern {
+               t.Fatalf("Glob returned err=%v, want ErrBadPattern", err)
+       }
+}
+
 func TestGlobError(t *testing.T) {
        bad := []string{`[]`, `nonexist/[]`}
        for _, pattern := range bad {