From 7917b5f31204528ea72e0629f0b7d52b35b27538 Mon Sep 17 00:00:00 2001 From: Damien Neil Date: Mon, 20 Mar 2023 10:43:19 -0700 Subject: [PATCH] [release-branch.go1.19] mime/multipart: limit parsed mime message sizes The parsed forms of MIME headers and multipart forms can consume substantially more memory than the size of the input data. A malicious input containing a very large number of headers or form parts can cause excessively large memory allocations. Set limits on the size of MIME data: Reader.NextPart and Reader.NextRawPart limit the the number of headers in a part to 10000. Reader.ReadForm limits the total number of headers in all FileHeaders to 10000. Both of these limits may be set with with GODEBUG=multipartmaxheaders=. Reader.ReadForm limits the number of parts in a form to 1000. This limit may be set with GODEBUG=multipartmaxparts=. Thanks for Jakob Ackermann (@das7pad) for reporting this issue. For CVE-2023-24536 For #59153 For #59269 Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1802455 Run-TryBot: Damien Neil Reviewed-by: Roland Shoemaker Reviewed-by: Julie Qiu Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1801087 Reviewed-by: Damien Neil Run-TryBot: Roland Shoemaker Change-Id: If134890d75f0d95c681d67234daf191ba08e6424 Reviewed-on: https://go-review.googlesource.com/c/go/+/481985 Run-TryBot: Michael Knyszek Auto-Submit: Michael Knyszek TryBot-Result: Gopher Robot Reviewed-by: Matthew Dempsky Upstream-Status: Backport [https://github.com/golang/go/commit/7917b5f31204528ea72e0629f0b7d52b35b27538] CVE: CVE-2023-24536 Signed-off-by: Vijay Anusuri --- src/mime/multipart/formdata.go | 19 ++++++++- src/mime/multipart/formdata_test.go | 61 ++++++++++++++++++++++++++++ src/mime/multipart/multipart.go | 31 ++++++++++---- src/mime/multipart/readmimeheader.go | 2 +- src/net/textproto/reader.go | 19 +++++---- 5 files changed, 115 insertions(+), 17 deletions(-) diff --git a/src/mime/multipart/formdata.go b/src/mime/multipart/formdata.go index 216cccb..0b508ae 100644 --- a/src/mime/multipart/formdata.go +++ b/src/mime/multipart/formdata.go @@ -13,6 +13,7 @@ import ( "math" "net/textproto" "os" + "strconv" ) // ErrMessageTooLarge is returned by ReadForm if the message form @@ -42,6 +43,15 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) { numDiskFiles := 0 multipartFiles := godebug.Get("multipartfiles") combineFiles := multipartFiles != "distinct" + maxParts := 1000 + multipartMaxParts := godebug.Get("multipartmaxparts") + if multipartMaxParts != "" { + if v, err := strconv.Atoi(multipartMaxParts); err == nil && v >= 0 { + maxParts = v + } + } + maxHeaders := maxMIMEHeaders() + defer func() { if file != nil { if cerr := file.Close(); err == nil { @@ -87,13 +97,17 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) { } var copyBuf []byte for { - p, err := r.nextPart(false, maxMemoryBytes) + p, err := r.nextPart(false, maxMemoryBytes, maxHeaders) if err == io.EOF { break } if err != nil { return nil, err } + if maxParts <= 0 { + return nil, ErrMessageTooLarge + } + maxParts-- name := p.FormName() if name == "" { @@ -137,6 +151,9 @@ func (r *Reader) readForm(maxMemory int64) (_ *Form, err error) { if maxMemoryBytes < 0 { return nil, ErrMessageTooLarge } + for _, v := range p.Header { + maxHeaders -= int64(len(v)) + } fh := &FileHeader{ Filename: filename, Header: p.Header, diff --git a/src/mime/multipart/formdata_test.go b/src/mime/multipart/formdata_test.go index 8ed26e0..c78eeb7 100644 --- a/src/mime/multipart/formdata_test.go +++ b/src/mime/multipart/formdata_test.go @@ -360,6 +360,67 @@ func testReadFormManyFiles(t *testing.T, distinct bool) { } } +func TestReadFormLimits(t *testing.T) { + for _, test := range []struct { + values int + files int + extraKeysPerFile int + wantErr error + godebug string + }{ + {values: 1000}, + {values: 1001, wantErr: ErrMessageTooLarge}, + {values: 500, files: 500}, + {values: 501, files: 500, wantErr: ErrMessageTooLarge}, + {files: 1000}, + {files: 1001, wantErr: ErrMessageTooLarge}, + {files: 1, extraKeysPerFile: 9998}, // plus Content-Disposition and Content-Type + {files: 1, extraKeysPerFile: 10000, wantErr: ErrMessageTooLarge}, + {godebug: "multipartmaxparts=100", values: 100}, + {godebug: "multipartmaxparts=100", values: 101, wantErr: ErrMessageTooLarge}, + {godebug: "multipartmaxheaders=100", files: 2, extraKeysPerFile: 48}, + {godebug: "multipartmaxheaders=100", files: 2, extraKeysPerFile: 50, wantErr: ErrMessageTooLarge}, + } { + name := fmt.Sprintf("values=%v/files=%v/extraKeysPerFile=%v", test.values, test.files, test.extraKeysPerFile) + if test.godebug != "" { + name += fmt.Sprintf("/godebug=%v", test.godebug) + } + t.Run(name, func(t *testing.T) { + if test.godebug != "" { + t.Setenv("GODEBUG", test.godebug) + } + var buf bytes.Buffer + fw := NewWriter(&buf) + for i := 0; i < test.values; i++ { + w, _ := fw.CreateFormField(fmt.Sprintf("field%v", i)) + fmt.Fprintf(w, "value %v", i) + } + for i := 0; i < test.files; i++ { + h := make(textproto.MIMEHeader) + h.Set("Content-Disposition", + fmt.Sprintf(`form-data; name="file%v"; filename="file%v"`, i, i)) + h.Set("Content-Type", "application/octet-stream") + for j := 0; j < test.extraKeysPerFile; j++ { + h.Set(fmt.Sprintf("k%v", j), "v") + } + w, _ := fw.CreatePart(h) + fmt.Fprintf(w, "value %v", i) + } + if err := fw.Close(); err != nil { + t.Fatal(err) + } + fr := NewReader(bytes.NewReader(buf.Bytes()), fw.Boundary()) + form, err := fr.ReadForm(1 << 10) + if err == nil { + defer form.RemoveAll() + } + if err != test.wantErr { + t.Errorf("ReadForm = %v, want %v", err, test.wantErr) + } + }) + } +} + func BenchmarkReadForm(b *testing.B) { for _, test := range []struct { name string diff --git a/src/mime/multipart/multipart.go b/src/mime/multipart/multipart.go index 958cef8..94464a8 100644 --- a/src/mime/multipart/multipart.go +++ b/src/mime/multipart/multipart.go @@ -16,11 +16,13 @@ import ( "bufio" "bytes" "fmt" + "internal/godebug" "io" "io/ioutil" "mime" "mime/quotedprintable" "net/textproto" + "strconv" "strings" ) @@ -121,12 +123,12 @@ func (r *stickyErrorReader) Read(p []byte) (n int, _ error) { return n, r.err } -func newPart(mr *Reader, rawPart bool, maxMIMEHeaderSize int64) (*Part, error) { +func newPart(mr *Reader, rawPart bool, maxMIMEHeaderSize, maxMIMEHeaders int64) (*Part, error) { bp := &Part{ Header: make(map[string][]string), mr: mr, } - if err := bp.populateHeaders(maxMIMEHeaderSize); err != nil { + if err := bp.populateHeaders(maxMIMEHeaderSize, maxMIMEHeaders); err != nil { return nil, err } bp.r = partReader{bp} @@ -142,9 +144,9 @@ func newPart(mr *Reader, rawPart bool, maxMIMEHeaderSize int64) (*Part, error) { return bp, nil } -func (bp *Part) populateHeaders(maxMIMEHeaderSize int64) error { +func (bp *Part) populateHeaders(maxMIMEHeaderSize, maxMIMEHeaders int64) error { r := textproto.NewReader(bp.mr.bufReader) - header, err := readMIMEHeader(r, maxMIMEHeaderSize) + header, err := readMIMEHeader(r, maxMIMEHeaderSize, maxMIMEHeaders) if err == nil { bp.Header = header } @@ -306,6 +308,19 @@ type Reader struct { // including header keys, values, and map overhead. const maxMIMEHeaderSize = 10 << 20 +func maxMIMEHeaders() int64 { + // multipartMaxHeaders is the maximum number of header entries NextPart will return, + // as well as the maximum combined total of header entries Reader.ReadForm will return + // in FileHeaders. + multipartMaxHeaders := godebug.Get("multipartmaxheaders") + if multipartMaxHeaders != "" { + if v, err := strconv.ParseInt(multipartMaxHeaders, 10, 64); err == nil && v >= 0 { + return v + } + } + return 10000 +} + // NextPart returns the next part in the multipart or an error. // When there are no more parts, the error io.EOF is returned. // @@ -313,7 +328,7 @@ const maxMIMEHeaderSize = 10 << 20 // has a value of "quoted-printable", that header is instead // hidden and the body is transparently decoded during Read calls. func (r *Reader) NextPart() (*Part, error) { - return r.nextPart(false, maxMIMEHeaderSize) + return r.nextPart(false, maxMIMEHeaderSize, maxMIMEHeaders()) } // NextRawPart returns the next part in the multipart or an error. @@ -322,10 +337,10 @@ func (r *Reader) NextPart() (*Part, error) { // Unlike NextPart, it does not have special handling for // "Content-Transfer-Encoding: quoted-printable". func (r *Reader) NextRawPart() (*Part, error) { - return r.nextPart(true, maxMIMEHeaderSize) + return r.nextPart(true, maxMIMEHeaderSize, maxMIMEHeaders()) } -func (r *Reader) nextPart(rawPart bool, maxMIMEHeaderSize int64) (*Part, error) { +func (r *Reader) nextPart(rawPart bool, maxMIMEHeaderSize, maxMIMEHeaders int64) (*Part, error) { if r.currentPart != nil { r.currentPart.Close() } @@ -350,7 +365,7 @@ func (r *Reader) nextPart(rawPart bool, maxMIMEHeaderSize int64) (*Part, error) if r.isBoundaryDelimiterLine(line) { r.partsRead++ - bp, err := newPart(r, rawPart, maxMIMEHeaderSize) + bp, err := newPart(r, rawPart, maxMIMEHeaderSize, maxMIMEHeaders) if err != nil { return nil, err } diff --git a/src/mime/multipart/readmimeheader.go b/src/mime/multipart/readmimeheader.go index 6836928..25aa6e2 100644 --- a/src/mime/multipart/readmimeheader.go +++ b/src/mime/multipart/readmimeheader.go @@ -11,4 +11,4 @@ import ( // readMIMEHeader is defined in package net/textproto. // //go:linkname readMIMEHeader net/textproto.readMIMEHeader -func readMIMEHeader(r *textproto.Reader, lim int64) (textproto.MIMEHeader, error) +func readMIMEHeader(r *textproto.Reader, maxMemory, maxHeaders int64) (textproto.MIMEHeader, error) diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go index 1c79f0a..ad2d777 100644 --- a/src/net/textproto/reader.go +++ b/src/net/textproto/reader.go @@ -484,12 +484,12 @@ func (r *Reader) ReadDotLines() ([]string, error) { // } // func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) { - return readMIMEHeader(r, math.MaxInt64) + return readMIMEHeader(r, math.MaxInt64, math.MaxInt64) } // readMIMEHeader is a version of ReadMIMEHeader which takes a limit on the header size. // It is called by the mime/multipart package. -func readMIMEHeader(r *Reader, lim int64) (MIMEHeader, error) { +func readMIMEHeader(r *Reader, maxMemory, maxHeaders int64) (MIMEHeader, error) { // Avoid lots of small slice allocations later by allocating one // large one ahead of time which we'll cut up into smaller // slices. If this isn't big enough later, we allocate small ones. @@ -507,7 +507,7 @@ func readMIMEHeader(r *Reader, lim int64) (MIMEHeader, error) { // Account for 400 bytes of overhead for the MIMEHeader, plus 200 bytes per entry. // Benchmarking map creation as of go1.20, a one-entry MIMEHeader is 416 bytes and large // MIMEHeaders average about 200 bytes per entry. - lim -= 400 + maxMemory -= 400 const mapEntryOverhead = 200 // The first line cannot start with a leading space. @@ -539,6 +539,11 @@ func readMIMEHeader(r *Reader, lim int64) (MIMEHeader, error) { continue } + maxHeaders-- + if maxHeaders < 0 { + return nil, errors.New("message too large") + } + // backport 5c55ac9bf1e5f779220294c843526536605f42ab // // value is computed as @@ -557,11 +562,11 @@ func readMIMEHeader(r *Reader, lim int64) (MIMEHeader, error) { vv := m[key] if vv == nil { - lim -= int64(len(key)) - lim -= mapEntryOverhead + maxMemory -= int64(len(key)) + maxMemory -= mapEntryOverhead } - lim -= int64(len(value)) - if lim < 0 { + maxMemory -= int64(len(value)) + if maxMemory < 0 { // TODO: This should be a distinguishable error (ErrMessageTooLarge) // to allow mime/multipart to detect it. return m, errors.New("message too large") -- 2.25.1