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[main] To refactor BodyPartParser of Multipart in order to avoid StackOverflowError easily (backport #11360) by @yousuketto #11469

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merged 1 commit into from
Oct 13, 2022
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[main] To refactor BodyPartParser of Multipart in order to avoid StackOverflowError easily (backport #11360) by @yousuketto #11469

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63 changes: 38 additions & 25 deletions core/play/src/main/scala/play/core/parsers/Multipart.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -326,8 +326,15 @@ object Multipart {
"'boundary' parameter of multipart Content-Type must not end with a space char"
)

// phantom type for ensuring soundness of our parsing method setup
sealed trait StateResult
sealed trait Done extends StateResult
case object Done extends Done
class ContinueParsing(parse: => StateResult) extends StateResult {
def apply(): StateResult = parse
}
object ContinueParsing {
def apply(parse: => StateResult): ContinueParsing = new ContinueParsing(parse)
}

private[this] val needle: Array[Byte] = {
val array = new Array[Byte](boundary.length + 4)
Expand All @@ -350,9 +357,9 @@ object Multipart {

override def createLogic(attributes: Attributes): GraphStageLogic =
new GraphStageLogic(shape) with InHandler with OutHandler {
private var output = collection.immutable.Queue.empty[RawPart]
private var state: ByteString => StateResult = tryParseInitialBoundary
private var terminated = false
private var output = collection.immutable.Queue.empty[RawPart]
private var state: ByteString => Done = tryParseInitialBoundary
private var terminated = false

override def onPush(): Unit = {
if (!terminated) {
Expand All @@ -378,13 +385,23 @@ object Multipart {

setHandlers(in, out, this)

def tryParseInitialBoundary(input: ByteString): StateResult = {
@tailrec
def handleParsingState(parse: ContinueParsing): Done = {
parse() match {
case Done => Done
case c: ContinueParsing => handleParsingState(c)
}
}

def handleParsingState(exec: => StateResult): Done = handleParsingState(ContinueParsing(exec))

def tryParseInitialBoundary(input: ByteString): Done = {
// we don't use boyerMoore here because we are testing for the boundary *without* a
// preceding CRLF and at a known location (the very beginning of the entity)
try {
if (boundary(input, 0)) {
val ix = boundaryLength
if (crlf(input, ix)) parseHeader(input, ix + 2, 0)
if (crlf(input, ix)) handleParsingState(parseHeader(input, ix + 2, 0))
else if (doubleDash(input, ix)) terminate()
else parsePreamble(input, 0)
} else parsePreamble(input, 0)
Expand All @@ -393,11 +410,11 @@ object Multipart {
}
}

def parsePreamble(input: ByteString, offset: Int): StateResult = {
def parsePreamble(input: ByteString, offset: Int): Done = {
try {
@tailrec def rec(index: Int): StateResult = {
@tailrec def rec(index: Int): Done = {
val needleEnd = boyerMoore.nextIndex(input, index) + needle.length
if (crlf(input, needleEnd)) parseHeader(input, needleEnd + 2, 0)
if (crlf(input, needleEnd)) handleParsingState(parseHeader(input, needleEnd + 2, 0))
else if (doubleDash(input, needleEnd)) terminate()
else rec(needleEnd)
}
Expand Down Expand Up @@ -488,7 +505,8 @@ object Multipart {
} else {
// There was not even enough space in the input to contain the needle. Only after we have enough data
// of at least the size of the needle we can decide if the body is empty or not.
state = more => checkEmptyBody(input ++ more, partStart, memoryBufferSize)(nonEmpty)(empty)
state = more =>
handleParsingState(checkEmptyBody(input ++ more, partStart, memoryBufferSize)(nonEmpty)(empty))
done()
}
}
Expand Down Expand Up @@ -517,7 +535,7 @@ object Multipart {
val needleEnd = currentPartEnd + needle.length
if (crlf(input, needleEnd)) {
emit(input.slice(offset, currentPartEnd))
parseHeader(input, needleEnd + 2, memoryBufferSize)
ContinueParsing(parseHeader(input, needleEnd + 2, memoryBufferSize))
} else if (doubleDash(input, needleEnd)) {
emit(input.slice(offset, currentPartEnd))
terminate()
Expand Down Expand Up @@ -546,7 +564,7 @@ object Multipart {
bufferExceeded("Memory buffer full on part " + partName)
} else if (crlf(input, needleEnd)) {
emit(DataPart(partName, input.slice(partStart, currentPartEnd).utf8String))
parseHeader(input, needleEnd + 2, newMemoryBufferSize)
ContinueParsing(parseHeader(input, needleEnd + 2, newMemoryBufferSize))
} else if (doubleDash(input, needleEnd)) {
emit(DataPart(partName, input.slice(partStart, currentPartEnd).utf8String))
terminate()
Expand All @@ -573,7 +591,7 @@ object Multipart {
val needleEnd = currentPartEnd + needle.length
if (crlf(input, needleEnd)) {
emit(BadPart(headers))
parseHeader(input, needleEnd + 2, memoryBufferSize)
ContinueParsing(parseHeader(input, needleEnd + 2, memoryBufferSize))
} else if (doubleDash(input, needleEnd)) {
emit(BadPart(headers))
terminate()
Expand All @@ -600,36 +618,31 @@ object Multipart {
head
}

def continue(input: ByteString, offset: Int)(next: (ByteString, Int) => StateResult): StateResult = {
def continue(input: ByteString, offset: Int)(next: (ByteString, Int) => StateResult): Done = {
state = math.signum(offset - input.length) match {
case -1 => more => next(input ++ more, offset)
case 0 => next(_, 0)
case -1 => more => handleParsingState(next(input ++ more, offset))
case 0 => more => handleParsingState(next(more, 0))
case 1 => throw new IllegalStateException
}
done()
}

def continue(next: (ByteString, Int) => StateResult): StateResult = {
state = next(_, 0)
done()
}

def bufferExceeded(message: String): StateResult = {
def bufferExceeded(message: String): Done = {
emit(MaxMemoryBufferExceeded(message))
terminate()
}

def fail(message: String): StateResult = {
def fail(message: String): Done = {
emit(ParseError(message))
terminate()
}

def terminate(): StateResult = {
def terminate(): Done = {
terminated = true
done()
}

def done(): StateResult = null // StateResult is a phantom type
def done(): Done = Done

// the length of the needle without the preceding CRLF
def boundaryLength: Int = needle.length - 2
Expand Down