How to use both width: 100% and height: auto on an image

Question

I would like to automatically adjust the height of my image according to the height of my text.

I tried using height: auto and width: 100% on my image (which seemed to make the most sense to me) but it doesn't work.

What I have

CodePen Example: https://codepen.io/JeremyWeb/pen/wvJPboW

* {
  padding: 0;
  margin: 0;
}
.container {
  display: flex;
  align-items: flex-start;
  
  border: solid 4px red;
  padding: 5px;
}
.text {
  width: 50%;
  
  border: solid 4px black;
  padding: 5px;
}

.img-container {
  width: 50%;
  height: auto;
  max-height: 100%;
  box-sizing: border-box;
  
  border: solid 4px black;
  padding: 5px;
}
.img {
  height: auto;
  width: 100%;
  object-fit: cover;
}

<div class="container">
  <p class="text">Simultaneously we had a problem with prisoner drunkenness that we couldn’t figure out. I mean , the guards searched cells multiple times to no avail, that we couldn’t figure out.</p>
  <div class="img-container">
    <img class="img" src="https://images.unsplash.com/photo-1621166856483-1725976c4e21?ixlib=rb-1.2.1&q=80&fm=jpg&crop=entropy&cs=tinysrgb&w=1080&fit=max"/>
  </div>
</div>

What I want

In HTML/CSS vanilla if possible. Thank you.

Answer 1

Based on Haworth's method, another way would be to use a background image on an empty div and using the min-height property.

.container {
  display: flex;
}
.text {
  width: 50%;
}

.img-container {
  width: 50%;
  min-height: 100%;
  background-image: url("https://images.unsplash.com/photo-1621166856483-1725976c4e21?ixlib=rb-1.2.1&q=80&fm=jpg&crop=entropy&cs=tinysrgb&w=1080&fit=max");
  background-size: cover;
  background-position: center;
}

<div class="container">
  <p class="text">Simultaneously we had a problem with prisoner drunkenness that we couldn’t figure out. I mean , the guards searched cells multiple times to no avail, that we couldn’t figure out.</p>
  <div class="img-container"></div>
</div>