X509 subject attributes are encoded as PRINTABLESTRING instead of UTF8STRING

[Atul Mundlik]

Hi All,

First post on the group,

I am using  go version go1.18.4 darwin/arm64.

I am trying to create X509 certificate with following code.

var COMMON_NAME = asn1.ObjectIdentifier([]int{2, 5, 4, 3})

 serial := new(big.Int).SetUint64(1)

subjectExtraNames = append(subjectExtraNames, pkix.AttributeTypeAndValue{Type: COMMON_NAME, Value: "golang"})

caCertTemplate := &x509.Certificate{

SerialNumber: 1,

IsCA: true,

NotBefore: time.Now(),

Subject: pkix.Name{ExtraNames: pkixAttrTypeValue},

NotAfter: time.Now().AddDate(10, 0, 0),

KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,

BasicConstraintsValid: true,

}

when I inspect the created certificate using asn1parse -in <PathToPemFile>

   31:d=4  hl=2 l=  13 cons: SEQUENCE          
   33:d=5  hl=2 l=   3 prim: OBJECT            :commonName
   38:d=5  hl=2 l=   6 prim: PRINTABLESTRING   :golang

the common name is PRINTABLESTRING and not the UTF8STRING.

As i understand, golang strings are utf8 default then why it is not UTF8STRING ?

However, in above code when i use below to create certificate

subjectExtraNames = append(subjectExtraNames, pkix.AttributeTypeAndValue{Type: COMMON_NAME, Value: "é um"})

and when I inspect certificate then it shows UTF8STRING for é um"

If this is how it is then is there a way to get a string without special characters as UTF8STRING in certificate?