OpenSSL: How to create a certificate with an empty subject DN?

This worked for me:

test-no-cn.cnf file

[req] 
default_bits       = 4096
encrypt_key        = no
default_md         = sha256
distinguished_name = req_distinguished_name
req_extensions = v3_req

[ req_distinguished_name ]

[ v3_req ]
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
subjectAltName=critical,email:[email protected],URI:http://example.com/,IP:192.168.7.1,dirName:dir_sect

[dir_sect]
C=DK
O=My Example Organization
OU=My Example Unit
CN=My Example Name

Generate the CSR

openssl req -new -newkey rsa:4096 -nodes -config test-no-cn.cnf -subj "/" -outform pem -out test-no-cn.csr -keyout test-no-cn.key

Sign the CSR

openssl x509 -req -days 365 -in test-no-cn.csr -signkey test-no-cn.key -out test-no-cn.crt -outform der -extensions v3_req -extfile test-no-cn.cnf

View the resulting certificate

openssl x509 -inform der -in test-no-cn.crt -noout -text

I also ran into this "no objects specified" error. It was displaying a prompt like this for various fields:

US []:

And I was just pressing enter because I had already set these values in the .cnf file. It turns out I needed to type all the values again, and then it worked.

The problem is with prompt = no in the original config. That makes openssl req assume you intend to specify subject entries in the config file and hits a preliminary check in req.c.

There's a workaround: Remove prompt = no, and instead add -subj / to your openssl req command line. Here's an example script that produces both a CSR and a self-signed certificate:

cat > openssl.cnf <<EOF
[ req ]
distinguished_name = req_distinguished_name
req_extensions = v3_req

[ req_distinguished_name ]

[ v3_req ]
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
subjectAltName=critical,email:[email protected]
EOF
openssl req -newkey rsa:2048 -config openssl.cnf -nodes -new -subj "/" \
  -out req.csr
openssl req -newkey rsa:2048 -config openssl.cnf -nodes -new -subj "/" \
  -x509 -out cert.crt