To control the height of your columns, you can use the max-height property. For instance, you can apply it to c1 and c2 like this:
.c1{
max-height:100%;
background-color:lightblue;
}
.c2{
max-height:100px;
overflow:hidden;
background-color:blue;
}
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<div class="container">
<div class="row">
<div class="col-sm-6 c1">
Viverra accumsan in nisl nisi. Bibendum est ultricies integer quis auctor elit sed vulputate. Mi sit amet mauris commodo quis imperdiet massa tincidunt. Consectetur purus ut faucibus pulvinar. Vulputate enim nulla aliquet porttitor lacus luctus. Porta nibh venenatis cras sed felis eget velit. Id cursus metus aliquam eleifend. Quis risus sed vulputate odio ut enim blandit volutpat maecenas. Vivamus at augue eget arcu dictum varius duis at. Interdum posuere lorem ipsum dolor sit amet consectetur adipiscing elit. Sed egestas egestas fringilla phasellus faucibus scelerisque eleifend.
</div>
<div class="col-sm-6 c2">
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Eget est lorem ipsum dolor sit amet consectetur adipiscing.
</div>
</div>
</div>
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<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>