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[LZ4] Fix incorrect truncation checks in block decoding

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This commit is contained in:
Timofey Solomko
2021-10-15 20:39:28 +03:00
parent cac1d635b9
commit f6c23987c4
1 changed files with 8 additions and 7 deletions
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Sources/LZ4/LZ4.swift
+8 -7
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@@ -81,7 +81,7 @@ public enum LZ4: DecompressionAlgorithm {
private static func process(legacyFrame data: Data) throws -> (Data, Data.Index) {
let reader = LittleEndianByteReader(data: data)
var out = Data()
// The end of a frame is determined is either by end-of-file or by encountering a valid frame magic number.
// The end of a frame is determined by either end-of-file or by encountering a valid frame magic number.
while !reader.isFinished {
// TODO: test truncated
guard reader.bytesLeft >= 4
@@ -109,7 +109,8 @@ public enum LZ4: DecompressionAlgorithm {
}
private static func process(frame data: Data, _ dictionary: Data?, _ extDictId: UInt32?) throws -> (Data, Data.Index) {
// Valid LZ4 frame must contain frame descriptor (at least 3 bytes) and EndMark (4 bytes), assuming no data blocks.
// Valid LZ4 frame must contain a frame descriptor (at least 3 bytes) and the EndMark (4 bytes), assuming no
// data blocks.
guard data.count >= 7
else { throw DataError.truncated }
let reader = LittleEndianByteReader(data: data)
@@ -248,14 +249,14 @@ public enum LZ4: DecompressionAlgorithm {
let reader = LittleEndianByteReader(data: data)
var out = dict ?? Data()
// These two variables used in checking end of block restrictions.
// These two variables are used in verifying the end of block restrictions.
var sequenceCount = 0
var lastMatchStartIndex = -1
while true {
sequenceCount += 1
// TODO: test truncated
guard data.endIndex - reader.offset > 1
guard data.endIndex - reader.offset >= 1
else { throw DataError.truncated }
let token = reader.byte()
@@ -263,7 +264,7 @@ public enum LZ4: DecompressionAlgorithm {
if literalCount == 15 {
while true {
// TODO: test truncated
guard data.endIndex - reader.offset > 1
guard data.endIndex - reader.offset >= 1
else { throw DataError.truncated }
let byte = reader.byte()
// There is no size limit on the literal count, so we need to check that it remains within Int range
@@ -293,7 +294,7 @@ public enum LZ4: DecompressionAlgorithm {
}
// TODO: test truncated
guard data.endIndex - reader.offset > 2
guard data.endIndex - reader.offset >= 2
else { throw DataError.truncated }
let offset = reader.uint16().toInt()
// The value of 0 is not valid.
@@ -304,7 +305,7 @@ public enum LZ4: DecompressionAlgorithm {
if matchLength == 19 {
while true {
// TODO: test truncated
guard data.endIndex - reader.offset > 1
guard data.endIndex - reader.offset >= 1
else { throw DataError.truncated }
let byte = reader.byte()
// Again, there is no size limit on the match length, so we need to check that it remains within Int