PKCS12_parse: unsupported - when running a ruby application as a service on the server - ruby

Question

In my ruby application, I am creating Apple wallet passes.
The application actually works well, but when I try to start it as a service (/etc/systemd/system), it is failing.
I can see that almost everything is working, but it fails when I want to parse the p12 certificate.
My function to sign the manifest file
def sign_manifest(serial_number)
temporary_path = "./passes/#{CUSTOMER}_#{serial_number}"
certificate_path = "./certs/Zertifikate.p12"
wwdr_path = "./certs/WWDR.pem"
manifest_path = "./passes/#{CUSTOMER}_#{serial_number}/manifest.json"
puts "Signing the manifest"
# Import the certificates
p12_certificate = OpenSSL::PKCS12::new(File.read(certificate_path), "")
wwdr_certificate = OpenSSL::X509::Certificate.new(File.read(wwdr_path))
# Sign the data
flag = OpenSSL::PKCS7::BINARY|OpenSSL::PKCS7::DETACHED
signed = OpenSSL::PKCS7::sign(p12_certificate.certificate, p12_certificate.key, File.read(manifest_path), [wwdr_certificate], flag)
# Create an output path for the signed data
signature_url = temporary_path + "/signature"
# Write out the data
File.open(signature_url, "w") do |f|
f.syswrite signed.to_der
end
end
Manually start with the command line
When I start the application manually with the command
ruby passGenerator.rb -p 20001 -o 0.0.0.0
on my server, it is working well, no issues.
Start as a service
The service itself looks like:
# wallet.service
[Unit]
Description = Apple Wallet Pass Generator
After = network.target
[Service]
WorkingDirectory = /var/www/html/passGenerator
ExecStart = ruby /var/www/html/passGenerator/passGenerator.rb -p 20001 -o 0.0.0.0
[Install]
WantedBy = multi-user.target
and start it with:
systemctl start wallet
I can start the service, and the server is running, but as soon as I want to create a new pass and come to this function, it crashes with the error:
PKCS12_parse: unsupported in the line of
p12_certificate = OpenSSL::PKCS12::new(File.read(certificate_path), "“)
(In the code snippet line 9)
I first thought about the relative paths, but everything else works with the relative paths.
Can anybody explain why that is happening?