/* This file is distributed under the following terms:

 * Copyright 2005-2014 Colin Percival.  All rights reserved.
 * Copyright 2014 Sean Kelly.  All rights reserved.

 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef _SHA256_H_
#define _SHA256_H_

#include <stddef.h>
#include <stdint.h>
#include <SHA256.h>

/* Pointer to memory-zeroing function. */
extern void (* volatile insecure_memzero_ptr)(volatile void *, size_t);

/**
 * insecure_memzero(buf, len):
 * Attempt to zero ${len} bytes at ${buf} in spite of optimizing compilers'
 * best (standards-compliant) attempts to remove the buffer-zeroing.  In
 * particular, to avoid performing the zeroing, a compiler would need to
 * use optimistic devirtualization; recognize that non-volatile objects do not
 * need to be treated as volatile, even if they are accessed via volatile
 * qualified pointers; and perform link-time optimization; in addition to the
 * dead-code elimination which often causes buffer-zeroing to be elided.
 *
 * Note however that zeroing a buffer does not guarantee that the data held
 * in the buffer is not stored elsewhere; in particular, there may be copies
 * held in CPU registers or in anonymous allocations on the stack, even if
 * every named variable is successfully sanitized.  Solving the "wipe data
 * from the system" problem will require a C language extension which does not
 * yet exist.
 *
 * For more information, see:
 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
 * http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-is-insufficient.html
 */
static inline void
insecure_memzero(volatile void * buf, size_t len)
{

        (insecure_memzero_ptr)(buf, len);
}

/* Context structure for SHA256 operations. */
typedef struct {
        uint32_t state[8];
        uint64_t count;
        uint8_t buf[64];
} SHA256_CTX;

/* Context structure for HMAC-SHA256 operations. */
typedef struct {
        SHA256 ictx;
        SHA256 octx;
} HMAC_SHA256_CTX;

/**
 * HMAC_SHA256_Init(ctx, K, Klen):
 * Initialize the HMAC-SHA256 context ${ctx} with ${Klen} bytes of key from
 * ${K}.
 */
void HMAC_SHA256_Init(HMAC_SHA256_CTX *, const void *, size_t);

/**
 * HMAC_SHA256_Update(ctx, in, len):
 * Input ${len} bytes from ${in} into the HMAC-SHA256 context ${ctx}.
 */
void HMAC_SHA256_Update(HMAC_SHA256_CTX *, const void *, size_t);

/**
 * HMAC_SHA256_Final(digest, ctx):
 * Output the HMAC-SHA256 of the data input to the context ${ctx} into the
 * buffer ${digest}.
 */
void HMAC_SHA256_Final(uint8_t[32], HMAC_SHA256_CTX *);

/**
 * PBKDF2_SHA256(passwd, passwdlen, salt, saltlen, c, buf, dkLen):
 * Compute PBKDF2(passwd, salt, c, dkLen) using HMAC-SHA256 as the PRF, and
 * write the output to buf.  The value dkLen must be at most 32 * (2^32 - 1).
 */
void PBKDF2_SHA256(const uint8_t *, size_t, const uint8_t *, size_t,
    uint64_t, uint8_t *, size_t);

#endif /* !_SHA256_H_ */