From b24651c3bb6fef59c0e92c24e69151d1a92c4b08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A1=D0=B5=D1=80=D0=B3=D0=B5=D0=B9=20=D0=9F=D1=80=D0=BE?=
 =?UTF-8?q?=D1=85=D0=BE=D1=80=D0=BE=D0=B2?= <seriy.pr@gmail.com>
Date: Mon, 19 Jan 2015 05:06:53 +0300
Subject: Add zlib limited output buffer size functionality

This functionality may be useful for compressed streams with high
compression ratio (in case of gzip it may be up to x1000), when
small amount of compressed data will produce large amount of
uncompressed output. This may lead to DoS attacks, because
server easily goes out of memory.

Example of such high compression ratio stream:
```
dd if=/dev/zero of=sparse.bin bs=1MB count=100 # 100mb of zeroes
gzip sparse.bin  # 95kb sparse.bin.gz
$ erl
> {ok, Compressed} = file:read_file("sparse.bin.gz"),
> 97082 = size(Compressed),
> Uncompressed = zlib:gunzip(Compressed),
> 100000000 = iolist_size(Uncompressed).
```
---
 erts/preloaded/ebin/zlib.beam | Bin 13188 -> 14156 bytes
 erts/preloaded/src/zlib.erl   |  39 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 1 deletion(-)

(limited to 'erts/preloaded')

diff --git a/erts/preloaded/ebin/zlib.beam b/erts/preloaded/ebin/zlib.beam
index 7006764d96..ed6ab5b254 100644
Binary files a/erts/preloaded/ebin/zlib.beam and b/erts/preloaded/ebin/zlib.beam differ
diff --git a/erts/preloaded/src/zlib.erl b/erts/preloaded/src/zlib.erl
index df7b2e6198..5ebc67dcaa 100644
--- a/erts/preloaded/src/zlib.erl
+++ b/erts/preloaded/src/zlib.erl
@@ -24,6 +24,7 @@
 	 deflate/2,deflate/3,deflateEnd/1,
 	 inflateInit/1,inflateInit/2,inflateSetDictionary/2,
 	 inflateSync/1,inflateReset/1,inflate/2,inflateEnd/1,
+	 inflateChunk/1, inflateChunk/2,
 	 setBufSize/2,getBufSize/1,
 	 crc32/1,crc32/2,crc32/3,adler32/2,adler32/3,getQSize/1,
 	 crc32_combine/4,adler32_combine/4,
@@ -100,6 +101,7 @@
 -define(INFLATE_RESET,   12).
 -define(INFLATE_END,     13).
 -define(INFLATE,         14).
+-define(INFLATE_CHUNK,   25).
 
 -define(CRC32_0,         15).
 -define(CRC32_1,         16).
@@ -263,6 +265,39 @@ inflate(Z, Data) ->
 	    erlang:error(badarg) 
     end.
 
+-spec inflateChunk(Z, Data) -> Decompressed | {more, Decompressed} when
+      Z :: zstream(),
+      Data :: iodata(),
+      Decompressed :: iolist().
+inflateChunk(Z, Data) ->
+    try port_command(Z, Data) of
+	true ->
+        inflateChunk(Z)
+    catch
+	error:_Err ->
+	    flush(Z),
+	    erlang:error(badarg)
+    end.
+
+-spec inflateChunk(Z) -> Decompressed | {more, Decompressed} when
+      Z :: zstream(),
+      Decompressed :: iolist().
+inflateChunk(Z) ->
+    Status = call(Z, ?INFLATE_CHUNK, []),
+    Data = receive
+	{Z, {data, Bin}} ->
+	    Bin
+    after 0 ->
+	    []
+    end,
+
+    case Status of
+        Good when (Good == ok) orelse (Good == stream_end) ->
+            Data;
+        inflate_has_more ->
+            {more, Data}
+    end.
+
 -spec inflateEnd(Z) -> 'ok' when
       Z :: zstream().
 inflateEnd(Z) ->
@@ -514,7 +549,9 @@ call(Z, Cmd, Arg) ->
 	[2,A,B,C,D] ->
 	    (A bsl 24)+(B bsl 16)+(C bsl 8)+D;
 	[3,A,B,C,D] ->
-	    erlang:error({need_dictionary,(A bsl 24)+(B bsl 16)+(C bsl 8)+D})
+	    erlang:error({need_dictionary,(A bsl 24)+(B bsl 16)+(C bsl 8)+D});
+	[4, _, _, _, _] ->
+	    inflate_has_more
     catch 
 	error:badarg -> %% Rethrow loses port_control from stacktrace.
 	    erlang:error(badarg)
-- 
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