options: Complete the transition to numeric toggles (`#if') For the sake of review, this commit alters only the code; the affiliated comments within the source files also need to be updated, but doing so now would obscure the operational changes that have been made here. * All on/off options have been switched to the numeric `#if' variant; that is the only way to make this `default_options.h.in' thing work in a reasonable manner. * There is now some very minor compile-time checking of the user's choice of options. * NO_FAST_EXPTMOD doesn't seem to be used, so it has been removed. * ENABLE_USER_ALGO_LIST was supposed to be renamed DROPBEAR_USER_ALGO_LIST, and this commit completes that work. * DROPBEAR_FUZZ seems to be a relatively new, as-yet undocumented option, which was added by the following commit: commit 6e0b539e9ca0b5628c6c5a3d118ad6a2e79e8039 Author: Matt Johnston <[email protected]> Date: Tue May 23 22:29:21 2017 +0800 split out checkpubkey_line() separately It has now been added to `sysoptions.h' and defined as `0' by default. * The configuration option `DROPBEAR_PASSWORD_ENV' is no longer listed in `default_options.h.in'; it is no longer meant to be set by the user, and is instead left to be defined in `sysoptions.h' (where it was already being defined) as merely the name of the environment variable in question: DROPBEAR_PASSWORD To enable or disable use of that environment variable, the user must now toggle `DROPBEAR_USE_DROPBEAR_PASSWORD'. * The sFTP support is now toggled by setting `DROPBEAR_SFTPSERVER', and the path of the sFTP server program is set independently through the usual SFTPSERVER_PATH.

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */

/**
    @file eax_decrypt.c
    EAX implementation, decrypt block, by Tom St Denis
*/
#include "tomcrypt.h"

#ifdef LTC_EAX_MODE

/**
   Decrypt data with the EAX protocol
   @param eax     The EAX state
   @param ct      The ciphertext
   @param pt      [out] The plaintext
   @param length  The length (octets) of the ciphertext
   @return CRYPT_OK if successful
*/
int eax_decrypt(eax_state *eax, const unsigned char *ct, unsigned char *pt,
                unsigned long length)
{
   int err;

   LTC_ARGCHK(eax != NULL);
   LTC_ARGCHK(pt  != NULL);
   LTC_ARGCHK(ct  != NULL);

   /* omac ciphertext */
   if ((err = omac_process(&eax->ctomac, ct, length)) != CRYPT_OK) {
      return err;
   }

   /* decrypt  */
   return ctr_decrypt(ct, pt, length, &eax->ctr);
}

#endif

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/* commit time: $Format:%ai$ */