Commit 0b6956b4 authored by Richard Levitte's avatar Richard Levitte
Browse files

Correct serious bug in AES-CBC decryption when the message length isn't 

a multiple of AES_BLOCK_SIZE.
Optimize decryption of all complete blocks in AES-CBC by removing an
unnecessary memcpy().

The error was notified by James Fernandes <jf210032@exchange.DAYTONOH.NCR.com>.
The unnecessary memcpy() was found as an effect of investigating that error.
parent 0bb6187e

crypto/aes/aes_cbc.c

+4 −5
Original line number Diff line number Diff line
@@ -91,21 +91,20 @@ void AES_cbc_encrypt(const unsigned char *in, unsigned char *out, 
		}			

	} else {

		while (len >= AES_BLOCK_SIZE) {

			memcpy(tmp, in, AES_BLOCK_SIZE);

			AES_decrypt(in, out, key);

			for(n=0; n < AES_BLOCK_SIZE; ++n)

				out[n] ^= ivec[n];

			memcpy(ivec, tmp, AES_BLOCK_SIZE);

			memcpy(ivec, in, AES_BLOCK_SIZE);

			len -= AES_BLOCK_SIZE;

			in += AES_BLOCK_SIZE;

			out += AES_BLOCK_SIZE;

		}

		if (len) {

			memcpy(tmp, in, AES_BLOCK_SIZE);

			AES_decrypt(tmp, tmp, key);

			AES_decrypt(in, tmp, key);

			for(n=0; n < len; ++n)

				out[n] ^= ivec[n];

			memcpy(ivec, tmp, AES_BLOCK_SIZE);

				out[n] = tmp[n] ^ ivec[n];

			memcpy(ivec, in, AES_BLOCK_SIZE);

		}			

	}

}