From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 16 Apr 2016 12:44:30 +0000 (+0300)
Subject: Account for SHA-512 asking for a 128-bit message length
X-Git-Url: http://git.tdb.fi/?p=libs%2Fcrypto.git;a=commitdiff_plain;h=52c9b0b8aacb973b6138ba0eb0e36e0c0cc23f80

Account for SHA-512 asking for a 128-bit message length

The upper 64 bits are filled with zeroes because 128-bit integers are not
available everywhere and it will be a while before lengths overflowing 64
bits are realistically possible.
---

diff --git a/source/sha2.cpp b/source/sha2.cpp
index 2451442..c7f51a5 100644
--- a/source/sha2.cpp
+++ b/source/sha2.cpp
@@ -122,8 +122,9 @@ unsigned SHA2<C>::get_digest(char *digest, unsigned len) const
 	SHA2<Constants> padded = *this;
 
 	char padding[Constants::BLOCK_SIZE] = { static_cast<char>(0x80) };
-	padded.update(padding, Constants::BLOCK_SIZE-(this->unprocessed_bytes+8)%Constants::BLOCK_SIZE);
+	padded.update(padding, Constants::BLOCK_SIZE-(this->unprocessed_bytes+Constants::MIN_PADDING)%Constants::BLOCK_SIZE);
 
+	padded.update(padding+1, Constants::MIN_PADDING-8);
 	UInt64 message_length = (processed_bytes+this->unprocessed_bytes)*8;
 	write_word(message_length, padding);
 	padded.update(padding, 8);
diff --git a/source/sha2.h b/source/sha2.h
index ed5c4fe..060b8d7 100644
--- a/source/sha2.h
+++ b/source/sha2.h
@@ -43,6 +43,7 @@ struct SHA2_256Constants
 		WORD_SIZE = sizeof(WordType),
 		BLOCK_SIZE = 64,   // 512 bits
 		DIGEST_SIZE = 32,  // 256 bits
+		MIN_PADDING = 8,
 		N_ROUNDS = 64
 	};
 
@@ -60,6 +61,7 @@ struct SHA2_512Constants
 		WORD_SIZE = sizeof(WordType),
 		BLOCK_SIZE = 128,  // 1024 bits
 		DIGEST_SIZE = 64,  // 512 bits
+		MIN_PADDING = 16,
 		N_ROUNDS = 80
 	};