fix(GODT-2573): Remove Prelude header parsing support

The handling of Preludes in the headers stem from the MBox format.
According to the IMAP spec, the literal submitted to APPEND should be a
valid RFC822 formatted message.

The handling of the prelude was also causing issues where an MBox
formatted entry would slip through and then cause issues later.

rfc822/header.go

@@ -455,6 +455,7 @@ func EraseHeaderValue(literal []byte, key string) ([]byte, error) {
 var (
 	ErrNonASCIIHeaderKey = fmt.Errorf("header key contains invalid characters")
 	ErrKeyNotFound       = fmt.Errorf("invalid header key")
+	ErrParseHeader       = fmt.Errorf("failed to parse header")
 )
 
 func mergeMultiline(line []byte) string {

rfc822/header_parser.go

@@ -35,14 +35,47 @@ func (hp *headerParser) next() (parsedHeaderEntry, error) {
 			if hp.header[hp.offset] == ':' {
 				prevOffset := hp.offset
 				hp.offset++
-				if hp.offset < headerLen && (hp.header[hp.offset] == ' ' || hp.header[hp.offset] == '\r' || hp.header[hp.offset] == '\n') {
+				if hp.offset < headerLen {
 					result.keyEnd = prevOffset
 
-					// Validate the header key.
-					for i := result.keyStart; i < result.keyEnd; i++ {
-						if v := hp.header[i]; v < 33 || v > 126 {
-							return parsedHeaderEntry{}, ErrNonASCIIHeaderKey
+					validateHeaderField := func(h parsedHeaderEntry) error {
+						for i := h.keyStart; i < h.keyEnd; i++ {
+							if v := hp.header[i]; v < 33 || v > 126 {
+								return ErrNonASCIIHeaderKey
+							}
 						}
+
+						return nil
+					}
+
+					switch {
+					case hp.header[hp.offset] == ' ':
+						if err := validateHeaderField(result); err != nil {
+							return parsedHeaderEntry{}, err
+						}
+
+					case hp.header[hp.offset] == '\r':
+						// ensure next char is '\n'
+						hp.offset++
+						if hp.offset < headerLen && hp.header[hp.offset] != '\n' {
+							return parsedHeaderEntry{}, fmt.Errorf("expected \\n after \\r: %w", ErrParseHeader)
+						}
+						fallthrough
+					case hp.header[hp.offset] == '\n':
+						hp.offset++
+
+						if err := validateHeaderField(result); err != nil {
+							return parsedHeaderEntry{}, err
+						}
+
+						// If the next char it's not a space, it's an empty header field.
+						if hp.offset < headerLen && !isWSP(hp.header[hp.offset]) {
+							result.valueStart = result.keyEnd
+							result.valueEnd = result.keyEnd
+							return result, nil
+						}
+					default:
+						return parsedHeaderEntry{}, fmt.Errorf("unexpected char '%v', for header field value: %w", string(hp.header[hp.offset]), ErrParseHeader)
 					}
 
 					break
@@ -66,7 +99,12 @@ func (hp *headerParser) next() (parsedHeaderEntry, error) {
 	}
 
 	// collect value.
-	searchOffset := result.keyEnd + 2
+	searchOffset := hp.offset
+
+	for searchOffset < headerLen && isWSP(hp.header[searchOffset]) {
+		searchOffset++
+	}
+
 	result.valueStart = searchOffset
 
 	for searchOffset < headerLen {

rfc822/header_test.go

@@ -289,14 +289,6 @@ func TestSplitHeaderBodyOnlyHeaderNoNewline(t *testing.T) {
 	assert.Equal(t, []byte(""), body)
 }
 
-func TestParseHeaderWithPrelude(t *testing.T) {
-	const literal = "From [email protected]  Tue Aug  6 13:34:34 2002\r\nTo: [email protected]"
-	header, err := NewHeader([]byte(literal))
-	require.NoError(t, err)
-
-	assert.Equal(t, header.Get("to"), "[email protected]")
-}
-
 func TestSetHeaderValue(t *testing.T) {
 	const literal = "To: [email protected]"
 
@@ -311,21 +303,6 @@ func TestSetHeaderValue(t *testing.T) {
 	assert.Equal(t, literalBytes, []byte(literal))
 }
 
-func TestSetHeaderValueWithPrelude(t *testing.T) {
-	const literal = "From [email protected]  Tue Aug  6 13:34:34 2002\r\nTo: [email protected]"
-
-	// Create a clone so we can test this with mutable memory.
-	literalBytes := xslices.Clone([]byte(literal))
-
-	newHeader, err := SetHeaderValue(literalBytes, "foo", "bar")
-	require.NoError(t, err)
-
-	assert.Equal(t, newHeader, []byte("From [email protected]  Tue Aug  6 13:34:34 2002\r\nFoo: bar\r\nTo: [email protected]"))
-
-	// Ensure the original data wasn't modified.
-	assert.Equal(t, literalBytes, []byte(literal))
-}
-
 func TestHeader_Erase(t *testing.T) {
 	literal := []byte("Subject: this is\r\n\ta multiline field\r\nFrom: duplicate entry\r\nReferences:\r\n\t <[email protected]>\r\n\r\n")
 	literalWithoutSubject := []byte("From: duplicate entry\r\nReferences:\r\n\t <[email protected]>\r\n\r\n")
@@ -390,3 +367,36 @@ Content-type: multipart/mixed; boundary="simple boundary"
 	require.Equal(t, "1.0", header.Get("MIME-Version"))
 	require.Equal(t, `multipart/mixed; boundary="simple boundary"`, header.Get("Content-type"))
 }
+
+func TestHeader_MBoxFormatCausesError(t *testing.T) {
+	const literal = `X-Mozilla-Keys:
+>From 1637354717149124322@xxx Tue Jun 25 22:52:20 +0000 2019
+X-GM-THIRD: 12345
+`
+
+	_, err := NewHeader([]byte(literal))
+	require.Error(t, err)
+}
+
+func TestHeader_EmptyField(t *testing.T) {
+	const literal = "X-Mozilla-Keys:\r\nX-GM-THIRD: 12345\r\n"
+
+	header, err := NewHeader([]byte(literal))
+	require.NoError(t, err)
+	require.Empty(t, header.Get("X-Mozilla-Key"))
+	require.Equal(t, "12345", header.Get("X-GM-THIRD"))
+}
+
+func TestHeader_MissingLFAfterCRIsError(t *testing.T) {
+	const literal = "X-Mozilla-Keys:\rX-GM-THIRD: 12345\r\n"
+
+	_, err := NewHeader([]byte(literal))
+	require.Error(t, err)
+}
+
+func TestHeader_InvalidCharAfterColonIsError(t *testing.T) {
+	const literal = "X-Mozilla-Keys:#X-GM-THIRD: 12345\r\n"
+
+	_, err := NewHeader([]byte(literal))
+	require.Error(t, err)
+}

tests/fetch_body_test.go

@@ -704,8 +704,7 @@ func TestFetchBodyPeekInvalidSectionNumber(t *testing.T) {
 func TestFetchBody_Dovecot_InvalidMessageHeader(t *testing.T) {
 	// This tests fails when requesting when fetch BODY.PEEK[HEADER.FIELDS (In-Reply-To In-Reply-To Cc)].
 	// Instead of only returning In-Reply-To and Cc, it was also returning the References header.
-	const message = `From [email protected]  Mon Apr  7 01:27:38 2003
-Received: with ECARTIS (v1.0.0; list dovecot); Mon, 07 Apr 2003 01:27:38 +0300 (EEST)
+	const message = `Received: with ECARTIS (v1.0.0; list dovecot); Mon, 07 Apr 2003 01:27:38 +0300 (EEST)
 Return-Path: <[email protected]>
 X-Original-To: [email protected]
 Delivered-To: [email protected]

tests/fetch_test.go

@@ -463,8 +463,7 @@ func TestFetchFromDataUids(t *testing.T) {
 }
 
 func TestFetchInReplyTo(t *testing.T) {
-	const message = `From [email protected]  Tue Jul 23 19:39:23 2002
-Received: with ECARTIS (v1.0.0; list dovecot); Tue, 23 Jul 2002 19:39:23 +0300 (EEST)
+	const message = `Received: with ECARTIS (v1.0.0; list dovecot); Tue, 23 Jul 2002 19:39:23 +0300 (EEST)
 Return-Path: <[email protected]>
 Delivered-To: [email protected]
 Date: Tue, 23 Jul 2002 19:39:23 +0300