mime/quotedprintable: accept LWSP-char after =

SP and HTAB are allowed after a = before the following CRLF.

RFC 2045 section 6.7 describes the ABNF for the quoted-printable encoding:

    qp-line := *(qp-segment transport-padding CRLF)
               qp-part transport-padding
    qp-segment := qp-section *(SPACE / TAB) "="
    transport-padding := *LWSP-char
                          ; Composers MUST NOT generate
                          ; non-zero length transport
                          ; padding, but receivers MUST
                          ; be able to handle padding
                          ; added by message transports.

RFC 822 defines LWSP-char as:

    LWSP-char   =  SPACE / HTAB

Dovecot's imaptest contains such a message in
src/tests/fetch-binary-mime-qp.mbox.

Fixes #70952

Change-Id: Ie05921088d7e4d6c92c4bf79b0f4a13586230753
GitHub-Last-Rev: e6e6eee8ebc2f629644a1d99129fb57cce58058f
GitHub-Pull-Request: golang/go#70951
Reviewed-on: https://go-review.googlesource.com/c/go/+/638276
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Sean Liao <sean@liao.dev>

diff --git a/src/mime/quotedprintable/reader.go b/src/mime/quotedprintable/reader.go
index 4239625402a2f79fcbaafcadae7d7ba2ade1db0c..9e70a1bb3d06d8344d0abb15e017afe7770d5683 100644 (file)
--- a/src/mime/quotedprintable/reader.go
+++ b/src/mime/quotedprintable/reader.go
@@ -66,6 +66,7 @@ var (
        crlf       = []byte("\r\n")
        lf         = []byte("\n")
        softSuffix = []byte("=")
+       lwspChar   = " \t"
 )
 
 // Read reads and decodes quoted-printable data from the underlying reader.
@@ -92,7 +93,7 @@ func (r *Reader) Read(p []byte) (n int, err error) {
                        wholeLine := r.line
                        r.line = bytes.TrimRightFunc(wholeLine, isQPDiscardWhitespace)
                        if bytes.HasSuffix(r.line, softSuffix) {
-                               rightStripped := wholeLine[len(r.line):]
+                               rightStripped := bytes.TrimLeft(wholeLine[len(r.line):], lwspChar)
                                r.line = r.line[:len(r.line)-1]
                                if !bytes.HasPrefix(rightStripped, lf) && !bytes.HasPrefix(rightStripped, crlf) &&
                                        !(len(rightStripped) == 0 && len(r.line) > 0 && r.rerr == io.EOF) {

diff --git a/src/mime/quotedprintable/reader_test.go b/src/mime/quotedprintable/reader_test.go
index 504bd5ef292547aef52dbd2a1c857947fd70c8af..1ff858a69c1799534a108c9f5b4f84a24ad7854c 100644 (file)
--- a/src/mime/quotedprintable/reader_test.go
+++ b/src/mime/quotedprintable/reader_test.go
@@ -66,6 +66,10 @@ func TestReader(t *testing.T) {
                        want: "Now's the time for all folk to come to the aid of their country."},
                {in: "accept UTF-8 right quotation mark: ’",
                        want: "accept UTF-8 right quotation mark: ’"},
+
+               // Transport padding
+               {in: "foo= \r\nbar", want: "foobar"},
+               {in: "foo=\t \r\nbar", want: "foobar"},
        }
        for _, tt := range tests {
                var buf strings.Builder
@@ -199,13 +203,13 @@ func TestExhaustive(t *testing.T) {
        }
        slices.Sort(outcomes)
        got := strings.Join(outcomes, "\n")
-       want := `OK: 28934
-invalid bytes after =: 3949
-quotedprintable: invalid hex byte 0x0d: 2048
+       want := `OK: 30638
+invalid bytes after =: 2243
+quotedprintable: invalid hex byte 0x0d: 2050
 unexpected EOF: 194`
        if testing.Short() {
-               want = `OK: 896
-invalid bytes after =: 100
+               want = `OK: 935
+invalid bytes after =: 61
 quotedprintable: invalid hex byte 0x0d: 26
 unexpected EOF: 3`
        }