Function simplicity_elements_mallocTapEnv

src/simplicity/elements/env.c:583–647

Allocate and initialize a 'elementsTapEnv' from a 'rawElementsTapEnv', copying or hashing the data as needed. * Returns NULL if malloc fails (or if malloc cannot be called because we require an allocation larger than SIZE_MAX). * * Precondition: *rawEnv is well-formed (i.e. rawEnv->pathLen <= 128.) */

 * Precondition: *rawEnv is well-formed (i.e. rawEnv->pathLen <= 128.)
 */
extern elementsTapEnv* simplicity_elements_mallocTapEnv(const rawElementsTapEnv* rawEnv) {
  if (!rawEnv) return NULL;
  if (128 < rawEnv->pathLen) return NULL;

  size_t allocationSize = sizeof(elementsTapEnv);

  const size_t numMidstate = rawEnv->pathLen;
  const size_t pad1 = PADDING(sha256_midstate, allocationSize);

  if (numMidstate) {
    if (SIZE_MAX - allocationSize < pad1) return NULL;
    allocationSize += pad1;

    if (SIZE_MAX / sizeof(sha256_midstate) < numMidstate) return NULL;
    if (SIZE_MAX - allocationSize < numMidstate * sizeof(sha256_midstate)) return NULL;
    allocationSize += numMidstate * sizeof(sha256_midstate);
  }

  char *allocation = simplicity_malloc(allocationSize);
  if (!allocation) return NULL;

  /* Casting through void* to avoid warning about pointer alignment.
   * Our padding is done carefully to ensure alignment.
   */
  elementsTapEnv* const env = (elementsTapEnv*)(void*)allocation;
  sha256_midstate* path = NULL;
  sha256_midstate internalKey;

  sha256_toMidstate(internalKey.s,  &rawEnv->controlBlock[1]);

  if (numMidstate)  {
    allocation += sizeof(elementsTapEnv) + pad1;

    if (rawEnv->pathLen) {
      path = (sha256_midstate*)(void*)allocation;
    }
  }

  *env = (elementsTapEnv){ .leafVersion = rawEnv->controlBlock[0] & 0xfe
                         , .internalKey = internalKey
                         , .path = path
                         , .pathLen = rawEnv->pathLen
                         };
  sha256_toMidstate(env->scriptCMR.s, rawEnv->scriptCMR);

  {
    sha256_context ctx = sha256_init(env->tappathHash.s);
    for (int i = 0; i < env->pathLen; ++i) {
      sha256_toMidstate(path[i].s,  &rawEnv->controlBlock[33+32*i]);
      sha256_hash(&ctx, &path[i]);
    }
    sha256_finalize(&ctx);
  }

  env->tapLeafHash = simplicity_make_tapleaf(env->leafVersion, &env->scriptCMR);

  {
    sha256_context ctx = sha256_init(env->tapEnvHash.s);