openssl

# PEM в DER
openssl x509 -outform der -in certificate.pem -out certificate.der
# PEM в P7B
openssl crl2pkcs7 -nocrl -certfile certificate.cer -out certificate.p7b -certfile CACert.cer
# PEM в PFX
openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

# II. Конвертирование файлов P7B
# P7B в PEM
openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer
# P7B в PFX
openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer openssl pkcs12 -export -in certificate.cer -inkey privateKey.key -out certificate.pfx -certfile CACert.cer

# III. Конвертирование файлов PFX
# PFX в PEM
openssl pkcs12 -in certificate.pfx -out certificate.cer -nodes

# IV. Конвертирование файлов DER
# DER в PEM
openssl x509 -inform der -in certificate.cer -out certificate.pem

# OpenSSL client
openssl s_client -connect example.com:443 -ssl3
echo | openssl s_client -servername NAME -connect HOST:PORT 2>/dev/null | openssl x509 -noout -dates

openssl s_client -showcerts -connect mail.example.com:993

# With specific protocol
openssl s_client -connect zabbix-a.itvx.cf:443 -tls1_1

# View date of cert
openssl x509 -enddate -noout -in file.pem

# View ciphers
openssl ciphers

# Generate key:
openssl genrsa -out server.key 4096

# Generate csr:
openssl req -config ./openssl.cnf -out client/client06/client06.csr -key client/client06/client06.key -new

# Sign csr:
openssl x509 -days 365 -in myCSR.csr -extfile v3.ext -CA myCA.crt -CAkey myCA.key -CAcreateserial -out userCertificate.crt