mime/multipart: fix bug when body contains prefix of the boundary

Fixes #10616

Change-Id: I4ef25eb0be6ccf474976fdb5087dd2c62c66c510
Reviewed-on: https://go-review.googlesource.com/11811
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/mime/multipart/multipart.go b/src/mime/multipart/multipart.go
index 04a9c33aaf068eb2cbe60690ac33d4995af5b50b..6f65a55de276bd9bc02a32e51de535bfc2a70577 100644 (file)
--- a/src/mime/multipart/multipart.go
+++ b/src/mime/multipart/multipart.go
@@ -165,16 +165,18 @@ func (pr partReader) Read(d []byte) (n int, err error) {
        if peek == nil {
                panic("nil peek buf")
        }
-
        // Search the peek buffer for "\r\n--boundary". If found,
        // consume everything up to the boundary. If not, consume only
        // as much of the peek buffer as cannot hold the boundary
        // string.
        nCopy := 0
        foundBoundary := false
-       if idx := bytes.Index(peek, p.mr.nlDashBoundary); idx != -1 {
+       if idx, isEnd := p.mr.peekBufferSeparatorIndex(peek); idx != -1 {
                nCopy = idx
-               foundBoundary = true
+               foundBoundary = isEnd
+               if !isEnd && nCopy == 0 {
+                       nCopy = 1 // make some progress.
+               }
        } else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
                nCopy = safeCount
        } else if unexpectedEOF {
@@ -338,6 +340,33 @@ func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
        return bytes.HasPrefix(rest, mr.nl)
 }
 
+// peekBufferSeparatorIndex returns the index of mr.nlDashBoundary in
+// peek and whether it is a real boundary (and not a prefix of an
+// unrelated separator). To be the end, the peek buffer must contain a
+// newline after the boundary.
+func (mr *Reader) peekBufferSeparatorIndex(peek []byte) (idx int, isEnd bool) {
+       idx = bytes.Index(peek, mr.nlDashBoundary)
+       if idx == -1 {
+               return
+       }
+       peek = peek[idx+len(mr.nlDashBoundary):]
+       if len(peek) > 1 && peek[0] == '-' && peek[1] == '-' {
+               return idx, true
+       }
+       peek = skipLWSPChar(peek)
+       // Don't have a complete line after the peek.
+       if bytes.IndexByte(peek, '\n') == -1 {
+               return -1, false
+       }
+       if len(peek) > 0 && peek[0] == '\n' {
+               return idx, true
+       }
+       if len(peek) > 1 && peek[0] == '\r' && peek[1] == '\n' {
+               return idx, true
+       }
+       return idx, false
+}
+
 // skipLWSPChar returns b with leading spaces and tabs removed.
 // RFC 822 defines:
 //    LWSP-char = SPACE / HTAB

diff --git a/src/mime/multipart/multipart_test.go b/src/mime/multipart/multipart_test.go
index d662e834059d80afee347aa0214889f7a77f16cd..d730888490794587dc80fd5f8ac55d69dbf301a7 100644 (file)
--- a/src/mime/multipart/multipart_test.go
+++ b/src/mime/multipart/multipart_test.go
@@ -565,6 +565,58 @@ foo: bar
                },
        },
 
+       // Issue 10616; minimal
+       {
+               name: "issue 10616 minimal",
+               sep:  "sep",
+               in: "--sep \r\nFoo: bar\r\n\r\n" +
+                       "a\r\n" +
+                       "--sep_alt\r\n" +
+                       "b\r\n" +
+                       "\r\n--sep--",
+               want: []headerBody{
+                       {textproto.MIMEHeader{"Foo": {"bar"}}, "a\r\n--sep_alt\r\nb\r\n"},
+               },
+       },
+
+       // Issue 10616; full example from bug.
+       {
+               name: "nested separator prefix is outer separator",
+               sep:  "----=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9",
+               in: strings.Replace(`------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9
+Content-Type: multipart/alternative; boundary="----=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt"
+
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+This is a multi-part message in MIME format.
+
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt
+Content-Type: text/html; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+html things
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt--
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9--`, "\n", "\r\n", -1),
+               want: []headerBody{
+                       {textproto.MIMEHeader{"Content-Type": {`multipart/alternative; boundary="----=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt"`}},
+                               strings.Replace(`------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+This is a multi-part message in MIME format.
+
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt
+Content-Type: text/html; charset="utf-8"
+Content-Transfer-Encoding: 8bit
+
+html things
+------=_NextPart_4c2fbafd7ec4c8bf08034fe724b608d9_alt--`, "\n", "\r\n", -1),
+                       },
+               },
+       },
+
        roundTripParseTest(),
 }