How to split the nginx config across multiple lines?

Question

Especially when configuring HPKP header (or other long headers in general) it would be useful to split a line in an nginx config over multiple lines.

This is the desired result:

pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg=";
pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec="; 
pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg="; 
pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg="; 
pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo="; 
pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g=";

However for the browser it should only be one line:

pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg="; pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec="; pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg="; pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg="; pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo="; pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g=";

So I've tried some things, but I'm not satisfied with the results...

First try: Just split it

add_header Public-Key-Pins '
pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg=";
pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec=";
pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg=";
pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg=";
pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo=";
pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g=";
'

This works, but with curl I can see that the browsers receives the header with all line breaks...

Second try: Backslash

Actually in the already linked article Scott Helme recommends this:

add_header Public-Key-Pins ' \
pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg="; \
pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec="; \
pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg="; \
pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg="; \
pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo="; \
pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g="; \
'

However in my case this just added the slashes and also returned them to the browser, so this does not work.

So how can I do this?

Bonus

Of course comments for every line would be an awesome addition:

pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg="; # current ECDSA
pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec="; # current RSA (nginx 1.11.0)
pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg="; # backup ECDSA 1
pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg="; # backup ECDSA 2
pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo="; # backup RSA 1
pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g="; # backup RSA 2

Answer 1

You might need to consider variable nesting that will look something like this:

set $PKP '';
set $PKP '${PKP}pin-sha256="X3pGTSOuJeEVw989IJ/cEtXUEmy52zs1TZQrU06KUKg=";'; # current ECDSA
set $PKP '${PKP}pin-sha256="MHJYVThihUrJcxW6wcqyOISTXIsInsdj3xK8QrZbHec=";'; # current RSA (nginx 1.11.0)
set $PKP '${PKP}pin-sha256="isi41AizREkLvvft0IRW4u3XMFR2Yg7bvrF7padyCJg=";';  # Backup ECDSA 1
set $PKP '${PKP}pin-sha256="I/bAACUzdYEFNw2ZKRaypOyYvvOtqBzg21g9a5WVClg=";';  # Backup ECDSA 2
set $PKP '${PKP}pin-sha256="Y4/Gxyck5JLLnC/zWHtSHfNljuMbOJi6dRQuRJTgYdo=";'; # backup RSA 1
set $PKP '${PKP}pin-sha256="/oCVQg3nP3DroGpFdAbaiYzenycUftqrH3LAyaIal2g=";';  # Backup RSA 2

add_header Public-Key-Pins $PKP;

Answer 2

the ; is the separator

so you can put things on multiple lines, just end the last line only with the ;