From a2a8c71d7774858db67f51b9c475c5b1d4e43e8f Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Thu, 1 Nov 2018 07:31:23 +0100
Subject: Make HTTP/2 compressor more resilient to bad data.

---
 netwerk/protocol/http/Http2Compression.cpp | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

(limited to 'netwerk/protocol')

diff --git a/netwerk/protocol/http/Http2Compression.cpp b/netwerk/protocol/http/Http2Compression.cpp
index 64fd05a17..9206f8b4c 100644
--- a/netwerk/protocol/http/Http2Compression.cpp
+++ b/netwerk/protocol/http/Http2Compression.cpp
@@ -402,7 +402,7 @@ Http2Decompressor::DecodeHeaderBlock(const uint8_t *data, uint32_t datalen,
 
   nsresult rv = NS_OK;
   nsresult softfail_rv = NS_OK;
-  while (NS_SUCCEEDED(rv) && (mOffset < datalen)) {
+  while (NS_SUCCEEDED(rv) && (mOffset < mDataLen)) {
     bool modifiesTable = true;
     if (mData[mOffset] & 0x80) {
       rv = DoIndexed();
@@ -684,6 +684,11 @@ nsresult
 Http2Decompressor::DecodeFinalHuffmanCharacter(const HuffmanIncomingTable *table,
                                                uint8_t &c, uint8_t &bitsLeft)
 {
+  MOZ_ASSERT(mOffset <= mDataLen);
+  if (mOffset > mDataLen) {
+    NS_WARNING("DecodeFinalHuffmanCharacter trying to read beyond end of buffer");
+    return NS_ERROR_FAILURE;
+  }
   uint8_t mask = (1 << bitsLeft) - 1;
   uint8_t idx = mData[mOffset - 1] & mask;
   idx <<= (8 - bitsLeft);
@@ -721,6 +726,7 @@ Http2Decompressor::DecodeFinalHuffmanCharacter(const HuffmanIncomingTable *table
 uint8_t
 Http2Decompressor::ExtractByte(uint8_t bitsLeft, uint32_t &bytesConsumed)
 {
+  MOZ_DIAGNOSTIC_ASSERT(mOffset < mDataLen);
   uint8_t rv;
 
   if (bitsLeft) {
@@ -750,8 +756,8 @@ Http2Decompressor::DecodeHuffmanCharacter(const HuffmanIncomingTable *table,
   uint8_t idx = ExtractByte(bitsLeft, bytesConsumed);
 
   if (table->IndexHasANextTable(idx)) {
-    if (bytesConsumed >= mDataLen) {
-      if (!bitsLeft || (bytesConsumed > mDataLen)) {
+    if (mOffset >= mDataLen) {
+      if (!bitsLeft || (mOffset > mDataLen)) {
         // TODO - does this get me into trouble in the new world?
         // No info left in input to try to consume, we're done
         LOG(("DecodeHuffmanCharacter all out of bits to consume, can't chain"));
@@ -892,6 +898,13 @@ Http2Decompressor::DoLiteralInternal(nsACString &name, nsACString &value,
     return rv;
   }
 
+  // sanity check
+  if (mOffset >= mDataLen) {
+    NS_WARNING("Http2 Decompressor ran out of data");
+    // This is session-fatal
+    return NS_ERROR_FAILURE;
+  }
+
   bool isHuffmanEncoded;
 
   if (!index) {
@@ -919,6 +932,13 @@ Http2Decompressor::DoLiteralInternal(nsACString &name, nsACString &value,
     return rv;
   }
 
+  // sanity check
+  if (mOffset >= mDataLen) {
+    NS_WARNING("Http2 Decompressor ran out of data");
+    // This is session-fatal
+    return NS_ERROR_FAILURE;
+  }
+  
   // now the value
   uint32_t valueLen;
   isHuffmanEncoded = mData[mOffset] & (1 << 7);
-- 
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