Use FX_SAFE_UINT32 on CPDF_ToUnicodeMap::Load

core/fpdfapi/fpdf_font/fpdf_font.cpp

Index: core/fpdfapi/fpdf_font/fpdf_font.cpp
diff --git a/core/fpdfapi/fpdf_font/fpdf_font.cpp b/core/fpdfapi/fpdf_font/fpdf_font.cpp
index cff5223a008ba749de4f3a1a07ec768c7e2822d3..825cd61b521ac12526ab8e3517028a6b472f62e9 100644
--- a/core/fpdfapi/fpdf_font/fpdf_font.cpp
+++ b/core/fpdfapi/fpdf_font/fpdf_font.cpp
@@ -18,6 +18,7 @@
 #include "core/fpdfapi/fpdf_parser/cpdf_simple_parser.h"
 #include "core/fpdfapi/fpdf_parser/cpdf_stream_acc.h"
 #include "core/fxcrt/fx_ext.h"
+#include "core/fxcrt/fx_safe_types.h"
 #include "core/fxge/fx_freetype.h"
 #include "third_party/base/numerics/safe_conversions.h"
 #include "third_party/base/stl_util.h"
@@ -224,7 +225,10 @@ void CPDF_ToUnicodeMap::Load(CPDF_Stream* pStream) {
         if (len == 1) {
           m_Map[srccode] = destcode.GetAt(0);
         } else {
-          m_Map[srccode] = m_MultiCharBuf.GetLength() * 0x10000 + 0xffff;
+          FX_SAFE_UINT32 uni = m_MultiCharBuf.GetLength();
+          uni *= 0x10000;
+          uni += 0xffff;
+          m_Map[srccode] = uni.ValueOrDie();
           m_MultiCharBuf.AppendChar(destcode.GetLength());

[Tom Sepez, 2016/10/04 17:41:21]

Drive-by: do we prefer skipping/defaulting the value insteadof crashing here?

also uni = uni * 0x10000 + 0xffff; might be cleaner.

[npm, 2016/10/04 19:24:17]

I would say we prefer not crashing whenever possible because crashing is the
worst possible user experience... But not sure, maybe dsinclair@ knows?

[dsinclair, 2016/10/04 19:27:59]

Do we know what a sensible default should be? If there is a sensible value we
can return that might be better.

           m_MultiCharBuf << destcode;
         }
@@ -255,7 +259,10 @@ void CPDF_ToUnicodeMap::Load(CPDF_Stream* pStream) {
             if (len == 1) {
               m_Map[code] = destcode.GetAt(0);
             } else {
-              m_Map[code] = m_MultiCharBuf.GetLength() * 0x10000 + 0xffff;
+              FX_SAFE_UINT32 uni = m_MultiCharBuf.GetLength();
+              uni *= 0x10000;
+              uni += 0xffff;
+              m_Map[code] = uni.ValueOrDie();
               m_MultiCharBuf.AppendChar(destcode.GetLength());
               m_MultiCharBuf << destcode;
             }
@@ -278,7 +285,10 @@ void CPDF_ToUnicodeMap::Load(CPDF_Stream* pStream) {
               } else {
                 retcode = StringDataAdd(destcode);
               }
-              m_Map[code] = m_MultiCharBuf.GetLength() * 0x10000 + 0xffff;
+              FX_SAFE_UINT32 uni = m_MultiCharBuf.GetLength();

[dsinclair, 2016/10/04 17:15:31]

Followup: These 6 lines are basically the same in the 3 chunks, can they be
factored out into a helper?

[npm, 2016/10/04 19:24:17]

Sounds good

+              uni *= 0x10000;
+              uni += 0xffff;
+              m_Map[code] = uni.ValueOrDie();
               m_MultiCharBuf.AppendChar(retcode.GetLength());
               m_MultiCharBuf << retcode;
               destcode = retcode;