text: /* $OpenBSD: evp_aead.c,v 1.4 2014/06/12 15:49:29 deraadt Exp $ */
  /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * 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 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.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.]
   */
  
  #include <limits.h>
  #include <string.h>
  
  #include <openssl/evp.h>
  #include <openssl/err.h>
  
  #include "evp_locl.h"
  
  size_t
  EVP_AEAD_key_length(const EVP_AEAD *aead)
  {
  	return aead->key_len;
  }
  
  size_t
  EVP_AEAD_nonce_length(const EVP_AEAD *aead)
  {
  	return aead->nonce_len;
  }
  
  size_t
  EVP_AEAD_max_overhead(const EVP_AEAD *aead)
  {
  	return aead->overhead;
  }
  
  size_t
  EVP_AEAD_max_tag_len(const EVP_AEAD *aead)
  {
  	return aead->max_tag_len;
  }
  
  int
  EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead,
      const unsigned char *key, size_t key_len, size_t tag_len, ENGINE *impl)
  {
  	ctx->aead = aead;
  	if (key_len != aead->key_len) {
  		EVPerr(EVP_F_EVP_AEAD_CTX_INIT, EVP_R_UNSUPPORTED_KEY_SIZE);
  		return 0;
  	}
  	return aead->init(ctx, key, key_len, tag_len);
  }
  
  void
  EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx)
  {
  	if (ctx->aead == NULL)
  		return;
  	ctx->aead->cleanup(ctx);
  	ctx->aead = NULL;
  }
  
  /* check_alias returns 0 if out points within the buffer determined by in
   * and in_len and 1 otherwise.
   *
   * When processing, there's only an issue if out points within in[:in_len]
   * and isn't equal to in. If that's the case then writing the output will
   * stomp input that hasn't been read yet.
   *
   * This function checks for that case. */
  static int
  check_alias(const unsigned char *in, size_t in_len, const unsigned char *out)
  {
  	if (out <= in)
  		return 1;
  	if (in + in_len <= out)
  		return 1;
  	return 0;
  }
  
  int
  EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, unsigned char *out, size_t *out_len,
      size_t max_out_len, const unsigned char *nonce, size_t nonce_len,
      const unsigned char *in, size_t in_len, const unsigned char *ad,
      size_t ad_len)
  {
  	size_t possible_out_len = in_len + ctx->aead->overhead;
  
  	/* Overflow. */
  	if (possible_out_len < in_len) {
  		EVPerr(EVP_F_AEAD_CTX_SEAL, EVP_R_TOO_LARGE);
  		goto error;
  	}
  
  	if (!check_alias(in, in_len, out)) {
  		EVPerr(EVP_F_AEAD_CTX_SEAL, EVP_R_OUTPUT_ALIASES_INPUT);
  		goto error;
  	}
  
  	if (ctx->aead->seal(ctx, out, out_len, max_out_len, nonce, nonce_len,
  	    in, in_len, ad, ad_len)) {
  		return 1;
  	}
  
  error:
  	/* In the event of an error, clear the output buffer so that a caller
  	 * that doesn't check the return value doesn't send raw data. */
  	memset(out, 0, max_out_len);
  	*out_len = 0;
  	return 0;
  }
  
  int
  EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, unsigned char *out, size_t *out_len,
      size_t max_out_len, const unsigned char *nonce, size_t nonce_len,
      const unsigned char *in, size_t in_len, const unsigned char *ad,
      size_t ad_len)
  {
  	if (!check_alias(in, in_len, out)) {
  		EVPerr(EVP_F_AEAD_CTX_OPEN, EVP_R_OUTPUT_ALIASES_INPUT);
  		goto error;
  	}
  
  	if (ctx->aead->open(ctx, out, out_len, max_out_len, nonce, nonce_len,
  	    in, in_len, ad, ad_len)) {
  		return 1;
  	}
  
  error:
  	/* In the event of an error, clear the output buffer so that a caller
  	 * that doesn't check the return value doesn't try and process bad
  	 * data. */
  	memset(out, 0, max_out_len);
  	*out_len = 0;
  	return 0;
  }
  