如何在Go中从x509证书公钥中获取字符串？

Question

If I have an *x509.Certificate object, how can I extract the public key base64 string representation out of it?

Answer 1

NOTE: Jump to #3 if you already have the x509.Certificate object.

---

You would need to do the following:

1. Decode the PEM with pem.Decode().

block, _ := pem.Decode([]byte(certPEM))

1. Parse the certificate with x509.ParseCertificate().

cert, _ := x509.ParseCertificate(block.Bytes)

1. Marshal the Public key with x509.MarshalPKIXPublicKey().

publicKeyDer, _ := x509.MarshalPKIXPublicKey(cert.PublicKey)

1. Encode it in a PEM encoded structure with pem.EncodeToMemory().

publicKeyBlock := pem.Block{
    Type:  "PUBLIC KEY",
    Bytes: publicKeyDer,
}
publicKeyPem := string(pem.EncodeToMemory(&publicKeyBlock))

Run it on Go Playground

---

You can confirm the result if you copy the certificate in the example to a file cert.pem with the command:

openssl x509 -inform pem -in cert.pem -pubkey -noout

You should get the same result!