Testing of RandomNumberGenerator::GenerateWord32 revealed a bug in
GenerateBlock.
GenerateBlock calls GenerateIntoBufferedTransformation.
GenerateIntoBufferedTransformation, in turn, calls, GenerateBlock. Ad
infinitum.
This patch fixes the circularity by calling OS_GenerateRandomBlock using
the OS's default entropy pool for userspace in a non-blocking mode.
Another way to address t is to have GenerateIntoBufferedTransformation
throw an Exception with type set to NOT_IMPLEMENTED. But I think that
course will be less useful.
Any comments or suggestions?
**********
$ cat cryptlib.diff
diff --git a/cryptlib.cpp b/cryptlib.cpp
index a9ed290..ad173e2 100644
--- a/cryptlib.cpp
+++ b/cryptlib.cpp
@@ -277,13 +277,15 @@ void RandomNumberGenerator::DiscardBytes(size_t n)
GenerateIntoBufferedTransformation(TheBitBucket(), DEFAULT_CHANNEL, n);
}
+// Avoid bringing in <osrng.h>, which depends on <cryptlib.h>
+extern void OS_GenerateRandomBlock(bool, byte*, size_t);
void
RandomNumberGenerator::GenerateIntoBufferedTransformation(BufferedTransformation
&target, const std::string &channel, lword length)
{
FixedSizeSecBlock<byte, 256> buffer;
while (length)
{
size_t len = UnsignedMin(buffer.size(), length);
- GenerateBlock(buffer, len);
+ OS_GenerateRandomBlock(false, buffer, len);
target.ChannelPut(channel, buffer, len);
length -= len;
}
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