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From d4e4288d839d0d9546a05986771f8738c382060c Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Dan=20=C4=8Cerm=C3=A1k?= <dan.cermak@cgc-instruments.com>
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Date: Sat, 7 Oct 2017 23:08:36 +0200
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Subject: Fix for CVE-2017-14864, CVE-2017-14862 and CVE-2017-14859
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The invalid memory dereference in
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Exiv2::getULong()/Exiv2::StringValueBase::read()/Exiv2::DataValue::read()
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is caused further up the call-stack, by
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v->read(pData, size, byteOrder) in TiffReader::readTiffEntry()
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passing an invalid pData pointer (pData points outside of the Tiff
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file). pData can be set out of bounds in the (size > 4) branch where
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baseOffset() and offset are added to pData_ without checking whether
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the result is still in the file. As offset comes from an untrusted
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source, an attacker can craft an arbitrarily large offset into the
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file.
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This commit adds a check into the problematic branch, whether the
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result of the addition would be out of bounds of the Tiff
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file. Furthermore the whole operation is checked for possible
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overflows.
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diff --git a/src/tiffvisitor.cpp b/src/tiffvisitor.cpp
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index 4ab733d4..ef13542e 100644
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--- a/src/tiffvisitor.cpp
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+++ b/src/tiffvisitor.cpp
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@@ -47,6 +47,7 @@ EXIV2_RCSID("@(#) $Id$")
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#include <iostream>
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#include <iomanip>
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#include <cassert>
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+#include <limits>
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// *****************************************************************************
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namespace {
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@@ -1517,7 +1518,19 @@ namespace Exiv2 {
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size = 0;
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}
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if (size > 4) {
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+ // setting pData to pData_ + baseOffset() + offset can result in pData pointing to invalid memory,
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+ // as offset can be arbitrarily large
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+ if ((static_cast<uintptr_t>(baseOffset()) > std::numeric_limits<uintptr_t>::max() - static_cast<uintptr_t>(offset))
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+ || (static_cast<uintptr_t>(baseOffset() + offset) > std::numeric_limits<uintptr_t>::max() - reinterpret_cast<uintptr_t>(pData_)))
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+ {
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+ throw Error(59);
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+ }
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+ if (pData_ + static_cast<uintptr_t>(baseOffset()) + static_cast<uintptr_t>(offset) > pLast_) {
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+ throw Error(58);
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+ }
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pData = const_cast<byte*>(pData_) + baseOffset() + offset;
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+
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+ // check for size being invalid
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if (size > static_cast<uint32_t>(pLast_ - pData)) {
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#ifndef SUPPRESS_WARNINGS
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EXV_ERROR << "Upper boundary of data for "
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