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author | Damien Neil <dneil@google.com> | 2023-03-16 14:18:04 -0700 |
---|---|---|
committer | Gopher Robot <gobot@golang.org> | 2023-04-04 17:01:56 +0000 |
commit | 3549c613b9d354d9f5410afc54dc9f7e6393c8cf (patch) | |
tree | 3ac48d17e3816b5eeaf97c2f7bb49721c013fe04 /src/mime | |
parent | 66ae75ff86950ae55ca1add47fa95b5576717be0 (diff) | |
download | go-3549c613b9d354d9f5410afc54dc9f7e6393c8cf.tar.gz go-3549c613b9d354d9f5410afc54dc9f7e6393c8cf.zip |
mime/multipart: avoid excessive copy buffer allocations in ReadForm
When copying form data to disk with io.Copy,
allocate only one copy buffer and reuse it rather than
creating two buffers per file (one from io.multiReader.WriteTo,
and a second one from os.File.ReadFrom).
Thanks to Jakob Ackermann (@das7pad) for reporting this issue.
For CVE-2023-24536
For #59153
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1802453
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Change-Id: I732bd2e1e7467918cac8ab9d65d089272ba4656f
Reviewed-on: https://go-review.googlesource.com/c/go/+/482075
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Bypass: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Diffstat (limited to 'src/mime')
-rw-r--r-- | src/mime/multipart/formdata.go | 15 | ||||
-rw-r--r-- | src/mime/multipart/formdata_test.go | 49 |
2 files changed, 61 insertions, 3 deletions
diff --git a/src/mime/multipart/formdata.go b/src/mime/multipart/formdata.go index e62727dbb1..902bb10e57 100644 --- a/src/mime/multipart/formdata.go +++ b/src/mime/multipart/formdata.go @@ -88,6 +88,7 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) { maxMemoryBytes = math.MaxInt64 } } + var copyBuf []byte for { p, err := r.nextPart(false, maxMemoryBytes) if err == io.EOF { @@ -151,14 +152,22 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) { } } numDiskFiles++ - size, err := io.Copy(file, io.MultiReader(&b, p)) + if _, err := file.Write(b.Bytes()); err != nil { + return nil, err + } + if copyBuf == nil { + copyBuf = make([]byte, 32*1024) // same buffer size as io.Copy uses + } + // os.File.ReadFrom will allocate its own copy buffer if we let io.Copy use it. + type writerOnly struct{ io.Writer } + remainingSize, err := io.CopyBuffer(writerOnly{file}, p, copyBuf) if err != nil { return nil, err } fh.tmpfile = file.Name() - fh.Size = size + fh.Size = int64(b.Len()) + remainingSize fh.tmpoff = fileOff - fileOff += size + fileOff += fh.Size if !combineFiles { if err := file.Close(); err != nil { return nil, err diff --git a/src/mime/multipart/formdata_test.go b/src/mime/multipart/formdata_test.go index 9b3f9ec392..e0ceb6f7aa 100644 --- a/src/mime/multipart/formdata_test.go +++ b/src/mime/multipart/formdata_test.go @@ -399,3 +399,52 @@ func testReadFormManyFiles(t *testing.T, distinct bool) { t.Fatalf("temp dir contains %v files; want 0", len(names)) } } + +func BenchmarkReadForm(b *testing.B) { + for _, test := range []struct { + name string + form func(fw *Writer, count int) + }{{ + name: "fields", + form: func(fw *Writer, count int) { + for i := 0; i < count; i++ { + w, _ := fw.CreateFormField(fmt.Sprintf("field%v", i)) + fmt.Fprintf(w, "value %v", i) + } + }, + }, { + name: "files", + form: func(fw *Writer, count int) { + for i := 0; i < count; i++ { + w, _ := fw.CreateFormFile(fmt.Sprintf("field%v", i), fmt.Sprintf("file%v", i)) + fmt.Fprintf(w, "value %v", i) + } + }, + }} { + b.Run(test.name, func(b *testing.B) { + for _, maxMemory := range []int64{ + 0, + 1 << 20, + } { + var buf bytes.Buffer + fw := NewWriter(&buf) + test.form(fw, 10) + if err := fw.Close(); err != nil { + b.Fatal(err) + } + b.Run(fmt.Sprintf("maxMemory=%v", maxMemory), func(b *testing.B) { + b.ReportAllocs() + for i := 0; i < b.N; i++ { + fr := NewReader(bytes.NewReader(buf.Bytes()), fw.Boundary()) + form, err := fr.ReadForm(maxMemory) + if err != nil { + b.Fatal(err) + } + form.RemoveAll() + } + + }) + } + }) + } +} |