Edit in JSFiddle

<div class="contenedor">
  Contenedor DIV
  <br/><br/>
  <input type="text" name="campo" value="Campo de texto"/>
</div>
.contenedor {
  width: 75%;
  height: 100px;
  border: 1px solid red;
  color: white;
  padding: 20px;
  box-sizing: border-box;
}

input{
  width:100%;
  padding:5px 10px;
}