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Updated on 2024-07-19 GMT+08:00
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HTTPS Certificate Requirements

The HTTPS configuration only supports certificates or private keys in PEM format. The certificate/private key upload requirements vary depending on certificate issuing agencies.

Certificates Issued by Root CA

A Certificate issued by Root CA is a complete certificate. You only need to upload the certificate when configuring HTTPS.

Use the text program to open the certificate in the PEM format, then you can view the certificate content, as shown in Figure 1.

A certificate in PEM format

  • The certificate starts with the -----BEGIN CERTIFICATE----- chain and ends with the -----END CERTIFICATE----- chain.
  • Each line of the certificate content contains 64 characters, but the number of characters in the last line can be smaller than 64.
  • No space is allowed in the certificate content.
Figure 1 A certificate in PEM format

Certificates Issued by Intermediate CAs

The certificate file issued by an intermediate agency contains several certificates. You need to combine the certificates into an integral one, and upload it when configuring HTTPS security acceleration. A combined certificate is shown as Figure 2.

Use the text program to open all the certificates in the PEM format. Put the server certificate on the top and then the intermediate certificate. Generally, an instruction will be issued together with the certificate. Be aware of the rules in the instruction. The general rules are as follows:
  • There are no lines between certificates.
  • The formats of certificate chains are as follows:

    -----BEGIN CERTIFICATE-----

    -----END CERTIFICATE-----

    -----BEGIN CERTIFICATE-----

    -----END CERTIFICATE-----

Figure 2 A combined certificate

RSA Private Key

PEM files can contain certificates or private keys. If a PEM file contains only private keys, the file suffix may be replaced by KEY.

Use the text program to open the private key file in the PEM or KEY format, then you can view the private key content, as shown in Figure 3.

Content of an RSA private key:

  • The private key starts with the -----BEGIN RSA PRIVATE KEY----- chain and ends with the -----END RSA PRIVATE KEY----- chain.
  • Each line of the private key content contains 64 characters, but the number of characters in the last line can be smaller than 64.
  • No space is allowed in the private key content.
Figure 3 An RSA private key

If the certificate chain of a private key file contains the following information: -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----, or -----BEGIN ENCRYPTED PRIVATE KEY----- and -----END ENCRYPTED PRIVATE KEY-----, you need to use the OpenSSL tool to run the following command to convert the format.

openssl rsa -in old_key.pem -out new_key.pem

Format Conversion

The HTTPS configuration only supports certificates or private keys in PEM format. It is recommended that OpenSSL be used to convert certificates in other formats into the PEM format. The following examples illustrate some popular converting methods.

In the following examples, the name of certificates before conversion is old_certificate by default, and that of private keys before transformation is old_key by default. The new certificate and private key names are new_certificate and new_key respectively.

  • Converting DER to PEM
    openssl x509 -inform der -in old_certificate.cer -out new_certificate.pem
openssl rsa -inform DER -outform pem -in old_key.der -out new_key.pem
  • Converting P7B to PEM
    openssl pkcs7 -print_certs -in old_certificate.p7b -out new_certificate.cer
  • Converting PFX to PEM
    openssl pkcs12 -in old_certificat.pfx -nokeys -out new_certificate.pem
openssl pkcs12 -in old_certificat.pfx -nocerts -out new_key.pem

To convert a PKCS8 private key to a PKCS1 one, run the following command:

openssl rsa -in old_certificat.pem -out pkcs1.pem