Disregard whitespace between leading boundary hyphens and marker

The way I read the RFC is that whitespace is not allowed before the
boundary marker, only afterwards, so the checks for leading WS are
removed, and the missing check for trailing WS is added.

See RFC 2046 §5.1.1: """The boundary delimiter line is then defined
as a line consisting entirely of two hyphen characters ("-", decimal
value 45) followed by the boundary parameter value from the
Content-Type header field, optional linear whitespace, and a
terminating CRLF."""

src/vmime/body.cpp

@@ -78,30 +78,12 @@ size_t body::findNextBoundaryPosition(
 			continue;
 		}
 
-		// Skip transport padding bytes (SPACE or HTAB), if any
-		size_t advance = 0;
-
-		while (pos != 0) {
-
-			parser->seek(pos - advance - 1);
-
-			const byte_t c = parser->peekByte();
-
-			if (c == ' ' || c == '\t') {
-				++advance;
-			} else {
-				break;
-			}
-		}
-
 		// Ensure the bytes before boundary are "[LF]--": boundary should be
 		// at the beginning of a line, and should start with "--"
-		if (pos - advance < 3) {
+		if (pos < 3) {
 			continue;
 		}
-
-		parser->seek(pos - advance - 3);
-
+		parser->seek(pos - 3);
 		if (!parser->matchBytes("\n--", 3)) {
 			continue;
 		}
@@ -111,21 +93,20 @@ size_t body::findNextBoundaryPosition(
 		const byte_t next = parser->peekByte();
 
 		// Boundary should be followed by a new line or a dash
-		if (next != '\r' && next != '\n' && next != '-') {
+		if (!isspace(next) && next != '-') {
 			continue;
 		}
 
 		// Get rid of the "[CR]" just before "[LF]--", if any
-		if (pos - advance >= 4) {
-
-			parser->seek(pos - advance - 4);
-
+		size_t backwards = 0;
+		if (pos >= 4) {
+			parser->seek(pos - 4);
 			if (parser->peekByte() == '\r') {
-				advance++;
+				++backwards;
 			}
 		}
 
-		*boundaryStart = pos - advance - 3;
+		*boundaryStart = pos - backwards - 3;
 		*boundaryEnd = pos + boundary.length();
 
 		return pos;

tests/parser/bodyPartTest.cpp

@@ -213,9 +213,9 @@ VMIME_TEST_SUITE_BEGIN(bodyPartTest)
 		vmime::string str =
 			"Content-Type: multipart/mixed; boundary=\"MY-BOUNDARY\""
 			"\r\n\r\n"
-			"--  \t MY-BOUNDARY\r\nHEADER1\r\n\r\nBODY1\r\n"
+			"--MY-BOUNDARY  \t \r\nHEADER1\r\n\r\nBODY1\r\n"
 			"--MY-BOUNDARY\r\n"
-			"-- MY-BOUNDARY--\r\n";
+			"--MY-BOUNDARY-- \r\n";
 
 		vmime::bodyPart p;
 		p.parse(str);
@@ -291,7 +291,7 @@ VMIME_TEST_SUITE_BEGIN(bodyPartTest)
 		vmime::string str =
 			"Content-Type: multipart/mixed"
 			"\r\n\r\n"
-			"--  \t UNKNOWN-BOUNDARY\r\nHEADER1\r\n\r\nBODY1\r\n"
+			"--UNKNOWN-BOUNDARY  \t \r\nHEADER1\r\n\r\nBODY1\r\n"
 			"--UNKNOWN-BOUNDARY\r\nHEADER2\r\n\r\nBODY2\r\n"
 			"--UNKNOWN-BOUNDARY--";