NGINX permission denied accessing htpasswd file in docker container - docker

Question

I have docker containers with NGINX and Docker Registry based on the tutorial at https://docs.docker.com/registry/recipes/nginx/
version: "3.5"
services:
nginx-auth:
hostname: reverse-proxy
image: nginx:alpine
restart: always
ports:
- 5044:443
links:
- registry:registry
volumes:
- ./auth:/etc/nginx/conf.d
- ./auth/nginx.conf:/etc/nginx/nginx.conf:ro
networks:
- registry-services
registry:
restart: always
image: registry:2
environment:
REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY: /var/lib/registry
volumes:
- ./data:/var/lib/registry
networks:
- registry-services
networks:
registry-services:
external: true
When I attempt to log in using the credentials in my htpasswd file, I get an error 500
$ sudo docker login -u=testuser -p=testpassword my-docker-registry.com:5044
WARNING! Using --password via the CLI is insecure. Use --password-stdin.
Error response from daemon: login attempt to https://my-docker-registry.com:5044/v2/ failed with status: 500 Internal Server Error
The NGINX container reports permission denied when trying to access the htpaswd file.
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: /etc/nginx/conf.d/default.conf is not a file or does not exist
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
10.148.100.212 - - [03/Aug/2022:21:31:20 +0000] "GET /v2/ HTTP/1.1" 401 179 "-" "docker/19.03.6 go/go1.12.17 git-commit/369ce74a3c kernel/5.4.0-64-generic os/linux arch/amd64 UpstreamClient(Docker-Client/19.03.6 \x5C(linux\x5C))"
2022/08/03 21:31:20 [crit] 21#21: *2 open() "/etc/nginx/conf.d/nginx.htpasswd" failed (13: Permission denied), client: 10.148.100.212, server: my-docker-registry.com, request: "GET /v2/ HTTP/1.1", host: "my-docker-registry.com:5044"
10.148.100.212 - testuser [03/Aug/2022:21:31:20 +0000] "GET /v2/ HTTP/1.1" 500 177 "-" "docker/19.03.6 go/go1.12.17 git-commit/369ce74a3c kernel/5.4.0-64-generic os/linux arch/amd64 UpstreamClient(Docker-Client/19.03.6 \x5C(linux\x5C))"
But I can open a sh shell to the NGINX container and verify the file is there and accessible from within the container
* Executing task: docker exec -it 40412ee4cda03507e180e7dfadbbe9a060dcc90172088968a299167291a34407 sh
/ # ls -la /etc/nginx/conf.d/nginx.htpasswd
-rw-rw---- 1 675254 8000 70 Aug 3 20:57 /etc/nginx/conf.d/nginx.htpasswd
/ # cat /etc/nginx/conf.d/nginx.htpasswd
testuser:$2y$05$648qqQTyWDvUgk1G3D.o6.CG1bCYI7uu5/jqmQaWGGmEX1js4CuE6
/ #
What do I need to do to allow NGINX to read the htpasswd file?