From 6da4956b31023ae967451e1d94ff51a746a9194f Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Thu, 9 Sep 2021 14:55:08 +0200
Subject: [PATCH] Merge pull request from GHSA-9vjp-v76f-g363

Motivation:

e Snappy frame decoder function doesn't restrict the size of the compressed data (and the uncompressed data) which may lead to excessive memory usage. Beside this it also may buffer reserved skippable chunks until the whole chunk was received which may lead to excessive memory usage as well.

Modifications:

- Add various validations for the max allowed size of a chunk
- Skip bytes on the fly when an skippable chunk is handled

Result:

No more risk of OOME. Thanks to Ori Hollander of JFrog Security for reporting the issue.
---
 .../handler/codec/compression/Snappy.java     | 30 +++++++++---
 .../codec/compression/SnappyFrameDecoder.java | 46 ++++++++++++++++---
 2 files changed, 62 insertions(+), 14 deletions(-)

diff --git a/codec/src/main/java/io/netty/handler/codec/compression/Snappy.java b/codec/src/main/java/io/netty/handler/codec/compression/Snappy.java
index 0a2d1c09b3..c851e4d8d6 100644
--- a/codec/src/main/java/io/netty/handler/codec/compression/Snappy.java
+++ b/codec/src/main/java/io/netty/handler/codec/compression/Snappy.java
@@ -38,12 +38,11 @@ public final class Snappy {
     private static final int COPY_2_BYTE_OFFSET = 2;
     private static final int COPY_4_BYTE_OFFSET = 3;
 
-    private State state = State.READY;
+    private State state = State.READING_PREAMBLE;
     private byte tag;
     private int written;
 
     private enum State {
-        READY,
         READING_PREAMBLE,
         READING_TAG,
         READING_LITERAL,
@@ -51,7 +50,7 @@ public final class Snappy {
     }
 
     public void reset() {
-        state = State.READY;
+        state = State.READING_PREAMBLE;
         tag = 0;
         written = 0;
     }
@@ -270,9 +269,6 @@ public final class Snappy {
     public void decode(ByteBuf in, ByteBuf out) {
         while (in.isReadable()) {
             switch (state) {
-            case READY:
-                state = State.READING_PREAMBLE;
-                // fall through
             case READING_PREAMBLE:
                 int uncompressedLength = readPreamble(in);
                 if (uncompressedLength == PREAMBLE_NOT_FULL) {
@@ -281,7 +277,6 @@ public final class Snappy {
                 }
                 if (uncompressedLength == 0) {
                     // Should never happen, but it does mean we have nothing further to do
-                    state = State.READY;
                     return;
                 }
                 out.ensureWritable(uncompressedLength);
@@ -378,6 +373,27 @@ public final class Snappy {
         return 0;
     }
 
+    /**
+     * Get the length varint (a series of bytes, where the lower 7 bits
+     * are data and the upper bit is a flag to indicate more bytes to be
+     * read).
+     *
+     * @param in The input buffer to get the preamble from
+     * @return The calculated length based on the input buffer, or 0 if
+     *   no preamble is able to be calculated
+     */
+    int getPreamble(ByteBuf in) {
+        if (state == State.READING_PREAMBLE) {
+            int readerIndex = in.readerIndex();
+            try {
+                return readPreamble(in);
+            } finally {
+                in.readerIndex(readerIndex);
+            }
+        }
+        return 0;
+    }
+
     /**
      * Reads a literal from the input buffer directly to the output buffer.
      * A "literal" is an uncompressed segment of data stored directly in the
diff --git a/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java b/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java
index 74a1289594..51997596eb 100644
--- a/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java
+++ b/codec/src/main/java/io/netty/handler/codec/compression/SnappyFrameDecoder.java
@@ -45,13 +45,19 @@ public class SnappyFrameDecoder extends ByteToMessageDecoder {
     }
 
     private static final int SNAPPY_IDENTIFIER_LEN = 6;
+    // See https://github.com/google/snappy/blob/1.1.9/framing_format.txt#L95
     private static final int MAX_UNCOMPRESSED_DATA_SIZE = 65536 + 4;
+    // See https://github.com/google/snappy/blob/1.1.9/framing_format.txt#L82
+    private static final int MAX_DECOMPRESSED_DATA_SIZE = 65536;
+    // See https://github.com/google/snappy/blob/1.1.9/framing_format.txt#L82
+    private static final int MAX_COMPRESSED_CHUNK_SIZE = 16777216 - 1;
 
     private final Snappy snappy = new Snappy();
     private final boolean validateChecksums;
 
     private boolean started;
     private boolean corrupted;
+    private int numBytesToSkip;
 
     /**
      * Creates a new snappy-framed decoder with validation of checksums
@@ -82,6 +88,16 @@ public class SnappyFrameDecoder extends ByteToMessageDecoder {
             return;
         }
 
+        if (numBytesToSkip != 0) {
+            // The last chunkType we detected was RESERVED_SKIPPABLE and we still have some bytes to skip.
+            int skipBytes = Math.min(numBytesToSkip, in.readableBytes());
+            in.skipBytes(skipBytes);
+            numBytesToSkip -= skipBytes;
+
+            // Let's return and try again.
+            return;
+        }
+
         try {
             int idx = in.readerIndex();
             final int inSize = in.readableBytes();
@@ -123,12 +139,15 @@ public class SnappyFrameDecoder extends ByteToMessageDecoder {
                         throw new DecompressionException("Received RESERVED_SKIPPABLE tag before STREAM_IDENTIFIER");
                     }
 
-                    if (inSize < 4 + chunkLength) {
-                        // TODO: Don't keep skippable bytes
-                        return;
-                    }
+                    in.skipBytes(4);
 
-                    in.skipBytes(4 + chunkLength);
+                    int skipBytes = Math.min(chunkLength, in.readableBytes());
+                    in.skipBytes(skipBytes);
+                    if (skipBytes != chunkLength) {
+                        // We could skip all bytes, let's store the remaining so we can do so once we receive more
+                        // data.
+                        numBytesToSkip = chunkLength - skipBytes;
+                    }
                     break;
                 case RESERVED_UNSKIPPABLE:
                     // The spec mandates that reserved unskippable chunks must immediately
@@ -141,7 +160,8 @@ public class SnappyFrameDecoder extends ByteToMessageDecoder {
                         throw new DecompressionException("Received UNCOMPRESSED_DATA tag before STREAM_IDENTIFIER");
                     }
                     if (chunkLength > MAX_UNCOMPRESSED_DATA_SIZE) {
-                        throw new DecompressionException("Received UNCOMPRESSED_DATA larger than 65540 bytes");
+                        throw new DecompressionException("Received UNCOMPRESSED_DATA larger than " +
+                                MAX_UNCOMPRESSED_DATA_SIZE + " bytes");
                     }
 
                     if (inSize < 4 + chunkLength) {
@@ -162,13 +182,25 @@ public class SnappyFrameDecoder extends ByteToMessageDecoder {
                         throw new DecompressionException("Received COMPRESSED_DATA tag before STREAM_IDENTIFIER");
                     }
 
+                    if (chunkLength > MAX_COMPRESSED_CHUNK_SIZE) {
+                        throw new DecompressionException("Received COMPRESSED_DATA that contains" +
+                                " chunk that exceeds " + MAX_COMPRESSED_CHUNK_SIZE + " bytes");
+                    }
+
                     if (inSize < 4 + chunkLength) {
                         return;
                     }
 
                     in.skipBytes(4);
                     int checksum = in.readIntLE();
-                    ByteBuf uncompressed = ctx.alloc().buffer();
+
+                    int uncompressedSize = snappy.getPreamble(in);
+                    if (uncompressedSize > MAX_DECOMPRESSED_DATA_SIZE) {
+                        throw new DecompressionException("Received COMPRESSED_DATA that contains" +
+                                " uncompressed data that exceeds " + MAX_DECOMPRESSED_DATA_SIZE + " bytes");
+                    }
+
+                    ByteBuf uncompressed = ctx.alloc().buffer(uncompressedSize, MAX_DECOMPRESSED_DATA_SIZE);
                     try {
                         if (validateChecksums) {
                             int oldWriterIndex = in.writerIndex();
-- 
2.35.3

