Proper way to decode asn1.RawValue in Golang-CodePudding

I am implementing certificate parsing in Golang and I need to obtain parent certificate link.

If I do openssl x509 -in certificate.pem -text -noout then I am able to see the following certificate extension:

            Authority Information Access:
                OCSP - URI:http://teszt.e-szigno.hu/testca3ocsp
                CA Issuers - URI:http://teszt.e-szigno.hu/TCA3.crt

In my go project I have following code:

content := `-----BEGIN CERTIFICATE-----
MIIJxDCCCKygAwIBAgINfEbzVUOoCNMWumANCjANBgkqhkiG9w0BAQsFADBqMQsw
CQYDVQQGEwJIVTERMA8GA1UEBwwIQnVkYXBlc3QxFjAUBgNVBAoMDU1pY3Jvc2Vj
IEx0ZC4xFDASBgNVBAsMC2UtU3ppZ25vIENBMRowGAYDVQQDDBFlLVN6aWdubyBU
ZXN0IENBMzAeFw0yMzAxMjQxMjQxNTBaFw0yNDAxMjQxMjQxNTBaMIHQMRMwEQYL
KwYBBAGCNzwCAQMTAkVFMRgwFgYLKwYBBAGCNzwCAQEMB1RhbGxpbm4xHTAbBgNV
BA8MFFByaXZhdGUgT3JnYW5pemF0aW9uMREwDwYDVQQFEwgxMjI2ODQ3NTELMAkG
A1UEBhMCRUUxEDAOBgNVBAcMB1RhbGxpbm4xFzAVBgNVBAoMDk1ha3Nla2Vza3Vz
IEFTMRswGQYDVQRhDBJQU0RFRS1GU0EtMTIyNjg0NzUxGDAWBgNVBAMMD21ha2Vj
b21tZXJjZS5sdDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAJFyj3sS
xev2yHbGXNmqw8e ZqFvrb1 UHlsm7c65HSjwAVjheHNV1cufilRf5X1PuBDmXtC
XpwD7FmOc7h  BAEdapv/XcWkMqUgbkfwhaZPkjbXIQBH7jbe4D 3pxn ZDlq/1b
Wi6dJhGHN Ydgw6x qGBOVzaFlprFdOYQXDw8yMc/iQMBahzzQApe2EwW1XRgyaT
DNE5t2T7uWC05qDYgi1HI50WGoezx7A7CDSjwG kFvczleY 4H73aPiGH1f0q EC
POZsoot12CWspBwZB9G03S5IoIipJPoQmIvnKGgeGbbY16P3VQ/78w9XjPy0dwid
x2CfPlPLTa8eJF0CAwEAAaOCBgAwggX8MA4GA1UdDwEB/wQEAwIFoDCBiQYKKwYB
BAHWeQIEAgR7BHkAdwB1AKoeeAQ/gGSCK VMtcHKwuMu5FDmczAqSLwmlwubLAgd
AAABhePMiCsAAAQDAEYwRAIgMbv IXdcxOgT9VPPUIuuHajA08AiGnQMKnSsYHPl
4egCICQN64jfx fitpnfxb6u531tA3VkjmMmLOkvN5b2vj4wMB0GA1UdJQQWMBQG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IGhhc3puw6FsYXTDoXZhbCBrYXBjc29sYXRvc2FuIGZlbG1lcsO8bMWRIGvDoXJv
a8OpcnQgYSBTem9sZ8OhbHRhdMOzIHNlbW1pbHllbiBmZWxlbMWRc3PDqWdldCBu
ZW0gdsOhbGxhbCEwHQYDVR0OBBYEFFpdJ86Z7qiDATzBzLvlL 6RLl12MB8GA1Ud
IwQYMBaAFNzmAijvNzCPiT6grSBV8 826PDNMBoGA1UdEQQTMBGCD21ha2Vjb21t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 yct80vartjnIaDk5rk6HQRJRjcuDI9 Hj
ep9nzwkN BUVwc2EV M7i35pCK dvNMTcgXTo2qGVznoSVjFuzshoC4mFIfxNczo
2NE2uTfU2wyWzQPYNcwFMZ7AoUXylGofEfS13mdH5dET  nWoAOD8ABZZqAeYsk9
R1fCxRThpldxjiJdDUZpzcVw obyjRhKIm6zAHd6R0E6KB9I feevF8IwgnTSozE
Zflb6EvyjuizsyqGteLrjim4ALu1 pA/2zhLZm55PWj1kM8PiWYqIGla0dKOzF4 
OTNNT6RR7bU=
-----END CERTIFICATE-----`
certDERBlock, _ := pem.Decode([]byte(content))
x509Cert, err := x509.ParseCertificate(certDERBlock.Bytes)
for _, extension := range x509Cert.Extensions {
    if extension.Id.Equal(asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 1}) {
        var collExts []asn1.RawValue
        asn1.Unmarshal(extension.Value, &collExts)
        for _, collExt := range collExts {
            fmt.Println(string(collExt.Bytes))
        }
    }
}

And it gives the following output:

 0�#http://teszt.e-szigno.hu/testca3ocsp
 0�0http://teszt.e-szigno.hu/TCA3.crt

Even though I am already able to parse such output and get the parent certificate link, I would like to understand how to get a human-readable text there. I've looked through the asn1 package and did not find any function to decode either asn1.RawValue object or asn1.RawValue.Bytes.

CodePudding user response：

You don't need to look at the x509Cert.Extensions for the AIA info, you can look it up directly from the x509.Certificate:

// RFC 5280, 4.2.2.1 (Authority Information Access)
OCSPServer            []string
IssuingCertificateURL []string

So just simply:

certDERBlock, _ := pem.Decode([]byte(certBody))
x509Cert, err = x509.ParseCertificate(certDERBlock.Bytes)

fmt.Printf("OCSPServer:            %v\n", x509Cert.OCSPServer)
fmt.Printf("IssuingCertificateURL: %v\n", x509Cert.IssuingCertificateURL)

https://go.dev/play/p/rUJOzYC_NmW

OCSPServer:            [http://teszt.e-szigno.hu/testca3ocsp]
IssuingCertificateURL: [http://teszt.e-szigno.hu/TCA3.crt]