Hi Everyone,
Analysis under UBsan revealed undefined behavior, even when
CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS was in effect. There were two
problems. First, assumeAligned was not always correct. Then, IsAligned<T>
returns a doctored value of 1 when CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
was defined.
The patch below clears the UB. The commented code shown was the original
code path. It was modified for testing. It showed up as a change due to a
local commit.
Any comments or objections?
**********
$ cat misc.h.diff
diff --git a/misc.h b/misc.h
index 20bc6d4..3c49516 100644
--- a/misc.h
+++ b/misc.h
@@ -1248,16 +1248,14 @@ inline void UnalignedPutWordNonTemplate(ByteOrder
order, byte *block, word64 val
template <class T>
inline T GetWord(bool assumeAligned, ByteOrder order, const byte *block)
{
-// #ifndef CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
-// if (!assumeAligned)
-// return UnalignedGetWordNonTemplate(order, block, (T*)NULL);
-// assert(IsAligned<T>(block));
-// #endif
-// return ConditionalByteReverse(order, *reinterpret_cast<const T
*>(block));
-
+ CRYPTOPP_UNUSED(assumeAligned);
+#ifdef CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
+ return ConditionalByteReverse(order, *reinterpret_cast<const T
*>(block));
+#else
T temp;
- memmove(&temp, block, sizeof(temp));
+ memcpy(&temp, block, sizeof(temp));
return ConditionalByteReverse(order, temp);
+#endif
}
template <class T>
@@ -1269,18 +1267,15 @@ inline void GetWord(bool assumeAligned, ByteOrder
order, T &result, const byte *
template <class T>
inline void PutWord(bool assumeAligned, ByteOrder order, byte *block, T
value, const byte *xorBlock = NULL)
{
-// #ifndef CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
-// if (!assumeAligned)
-// return UnalignedPutWordNonTemplate(order, block, value,
xorBlock);
-// assert(IsAligned<T>(block));
-// assert(IsAligned<T>(xorBlock));
-//#endif
-// *reinterpret_cast<T *>(block) = ConditionalByteReverse(order, value)
^ (xorBlock ? *reinterpret_cast<const T *>(xorBlock) : 0);
-
+ CRYPTOPP_UNUSED(assumeAligned);
+#ifdef CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
+ *reinterpret_cast<T *>(block) = ConditionalByteReverse(order, value) ^
(xorBlock ? *reinterpret_cast<const T *>(xorBlock) : 0);
+#else
T t1, t2 = 0;
t1 = ConditionalByteReverse(order, value);
- if(xorBlock) memmove(&t2, xorBlock, sizeof(T));
- memmove(block, &(t1 ^= t2), sizeof(T));
+ if(xorBlock) memcpy(&t2, xorBlock, sizeof(T));
+ memcpy(block, &(t1 ^= t2), sizeof(T));
+#endif
}
template <class T, class B, bool A=false>
--
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