Parsing and printing X.509 attributes from PEM

Question

I'm looking for a simple example for parsing an X.509 PEM in go and dumping the values to stdout. Can anybody provide an example ?

Answer 1

You want to use encoding.pem to decode the pem file, which will give you the DER blocks you can decode with the crypto/x509 package.

For example:

certPEMBlock, err := ioutil.ReadFile(certFile)
if err != nil {
    log.Fatal(err)
}

var blocks [][]byte
for {
    var certDERBlock *pem.Block
    certDERBlock, certPEMBlock = pem.Decode(certPEMBlock)
    if certDERBlock == nil {
        break
    }

    if certDERBlock.Type == "CERTIFICATE" {
        blocks = append(blocks, certDERBlock.Bytes)
    }
}

for _, block := range blocks {
    cert, err := x509.ParseCertificate(block)
    if err != nil {
        log.Println(err)
        continue
    }

    fmt.Println("Certificate:")
    fmt.Printf("\tSubject: %+v\n", cert.Subject)
    fmt.Printf("\tDNS Names: %+v\n", cert.DNSNames)
    fmt.Printf("\tEmailAddresses: %+v\n", cert.EmailAddresses)
    fmt.Printf("\tIPAddresses: %+v\n", cert.IPAddresses)
}