Detect truncated frames to avoid infinite loop (#47)

* detect truncated frames

* add check that code > 0

* fix tests for 1.6

src/decompression.jl

@@ -76,7 +76,14 @@ function TranscodingStreams.process(codec::ZstdDecompressor, input::Memory, outp
         error[] = ErrorException("zstd error")
         return Δin, Δout, :error
     else
-        return Δin, Δout, code == 0 ? :end : :ok
+        if code == 0
+            return Δin, Δout, :end
+        elseif input.size == 0 && code > 0
+            error[] = ErrorException("zstd frame truncated. Expected at least $(code) more bytes")
+            return Δin, Δout, :error
+        else
+            return Δin, Δout, :ok
+        end
     end
 end
 

test/runtests.jl

@@ -3,6 +3,8 @@ using Random
 using TranscodingStreams
 using Test
 
+Random.seed!(1234)
+
 @testset "Zstd Codec" begin
     codec = ZstdCompressor()
     @test codec isa ZstdCompressor
@@ -20,6 +22,20 @@ using Test
     @test read(ZstdDecompressorStream(IOBuffer(data))) == b"foo"
     @test read(ZstdDecompressorStream(IOBuffer(vcat(data, data)))) == b"foofoo"
 
+    @testset "Truncated frames" begin
+        # issue #24
+        @test_throws ErrorException transcode(ZstdDecompressor, UInt8[])
+        for trial in 1:1000
+            local uncompressed_data = rand(UInt8, rand(0:100))
+            local compressed_data = transcode(ZstdCompressor, uncompressed_data)
+            local L = length(compressed_data)
+            for n in 0:L-1
+                @test_throws ErrorException transcode(ZstdDecompressor, compressed_data[1:n])
+            end
+            @test transcode(ZstdDecompressor, compressed_data) == uncompressed_data
+        end
+    end
+
     @test ZstdCompressorStream <: TranscodingStreams.TranscodingStream
     @test ZstdDecompressorStream <: TranscodingStreams.TranscodingStream