golang subject dn from x509 cert

问题

Is there any easy way to get the complete subject DN (or issuer DN) from an x509 certificate in go as a string?

I was not able to find any methods like ".String()" in pkix.Name

回答1:

Solution (thanks to a colleague):

var oid = map[string]string{
    "2.5.4.3":                    "CN",
    "2.5.4.4":                    "SN",
    "2.5.4.5":                    "serialNumber",
    "2.5.4.6":                    "C",
    "2.5.4.7":                    "L",
    "2.5.4.8":                    "ST",
    "2.5.4.9":                    "streetAddress",
    "2.5.4.10":                   "O",
    "2.5.4.11":                   "OU",
    "2.5.4.12":                   "title",
    "2.5.4.17":                   "postalCode",
    "2.5.4.42":                   "GN",
    "2.5.4.43":                   "initials",
    "2.5.4.44":                   "generationQualifier",
    "2.5.4.46":                   "dnQualifier",
    "2.5.4.65":                   "pseudonym",
    "0.9.2342.19200300.100.1.25": "DC",
    "1.2.840.113549.1.9.1":       "emailAddress",
    "0.9.2342.19200300.100.1.1":  "userid",
}

func getDNFromCert(namespace pkix.Name, sep string) (string, error) {
    subject := []string{}
    for _, s := range namespace.ToRDNSequence() {
        for _, i := range s {
            if v, ok := i.Value.(string); ok {
                if name, ok := oid[i.Type.String()]; ok {
                    // <oid name>=<value>
                    subject = append(subject, fmt.Sprintf("%s=%s", name, v))
                } else {
                    // <oid>=<value> if no <oid name> is found
                    subject = append(subject, fmt.Sprintf("%s=%s", i.Type.String(), v))
                }
            } else {
                // <oid>=<value in default format> if value is not string
                subject = append(subject, fmt.Sprintf("%s=%v", i.Type.String, v))
            }
        }
    }
    return sep + strings.Join(subject, sep), nil
}

calling the function:

subj, err := getDNFromCert(x509Cert.Subject, "/")
if err != nil {
   // do error handling
}
fmt.Println(subj)

output (example):

/C=US/O=some organization/OU=unit/CN=common name

this seems to be the only "easy" solution

回答2:

I faced the same task today. You could get subject from certificate this way:

// d is []byte with your certificate
cert, err := x509.ParseCertificate(d)
fmt.Printf("%+v\n", cert.Subject.ToRDNSequence())

// Output: CN=client1,OU=MyClients,O=MongoDB-Cluster,L=Austin,ST=TX,C=US

回答3:

In order to get complete subject DN (or issuer DN) from an x509 certificate, you may use next code:

cert, err := x509.ParseCertificate(certData)
if err != nil {
    return err
}

var subject pkix.RDNSequence
if _, err := asn1.Unmarshal(cert.RawSubject, &subject); err != nil {
    return err
}

fmt.Plrintln(subject.String()

Similarly, if you need to get only some specific object value from the subject (or issuer) you may use next approach. Example below retrieves UID from subject (which is not defined in the stdlib https://github.com/golang/go/issues/25667)

// http://www.alvestrand.no/objectid/0.9.2342.19200300.100.1.1.html
const oidUserID = "0.9.2342.19200300.100.1.1"
var UID string

cert, err := x509.ParseCertificate(certData)
if err != nil {
    return err
}

// manually parsing the Certificate subject to get the
// UID field, which is being ignored by the stdlib
// https://github.com/golang/go/issues/25667
var subject pkix.RDNSequence
if _, err := asn1.Unmarshal(cert.RawSubject, &subject); err != nil {
    return err
}

for _, s := range subject {
    for _, i := range s {
        if i.Type.String() == oidUserID {
            if v, ok := i.Value.(string); ok {
                UID = v
            }
        }
    }
}

fmt.Println(UID)

UPDATE: Simplified way to get the UID, thanks to @FiloSottile:

// http://www.alvestrand.no/objectid/0.9.2342.19200300.100.1.1.html
var oidUserID = []int{0, 9, 2342, 19200300, 100, 1, 1}
var UID string

cert, err := x509.ParseCertificate(certData)
if err != nil {
    return err
}

// reading the UID from list of unprased 
// objects from Subject
for _, n := range cert.Subject.Names {
    if n.Type.Equal(oidUserID) {
        if v, ok := n.Value.(string); ok {
            UID = v
        }
    }
}

fmt.Println(UID)

回答4:

Using directly fmt.Sprintf("%+v", cert.Subject.ToRDNSequence())

does the work in go 1.9. For superior versions of go (>=1.10), it works with ".String()" in pkix.Name

回答5:

For now you can just use:

cert, _ := x509.ParseCertificate(certDERBlock.Bytes)
fmt.Println(cert.Subject.CommonName)

https://golang.org/pkg/crypto/x509/#Certificate
https://golang.org/pkg/crypto/x509/pkix/#Name

回答6:

Here is the function that I use.

var (
    cnNameOid = asn1.ObjectIdentifier{2, 5, 4, 3}
    emailOid  = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 1}
    userIDOid = asn1.ObjectIdentifier{0, 9, 2342, 19200300, 100, 1, 1}
    dcNameOid = asn1.ObjectIdentifier{0, 9, 2342, 19200300, 100, 1, 25}
)

// RDNSToString returns the Relative Distinguish Name as a string.
func RDNSToString(rdns *pkix.RDNSequence) string {
    var buf strings.Builder
    for _, rdn := range *rdns {
        if len(rdn) == 0 {
            continue
        }
        for _, atv := range rdn {
            value, ok := atv.Value.(string)
            if !ok {
                continue
            }
            t := atv.Type
            if len(t) == 4 && t[0] == 2 && t[1] == 5 && t[2] == 4 {
                switch t[3] {
                case 3:
                    buf.WriteString("/CN=") // common name
                    buf.WriteString(value)
                case 4:
                    buf.WriteString("/SN=") // surname
                    buf.WriteString(value)
                case 5:
                    buf.WriteString("/SERIALNUMBER=")
                    buf.WriteString(value)
                case 6:
                    buf.WriteString("/C=") // country
                    buf.WriteString(value)
                case 7:
                    buf.WriteString("/L=") // locality
                    buf.WriteString(value)
                case 8:
                    buf.WriteString("/ST=") // state
                    buf.WriteString(value)
                case 9:
                    buf.WriteString("/STREET=")
                    buf.WriteString(value)
                case 10:
                    buf.WriteString("/O=") // organization
                    buf.WriteString(value)
                case 11:
                    buf.WriteString("/OU=") // organization unit
                    buf.WriteString(value)
                case 12:
                    buf.WriteString("/T=") // title
                    buf.WriteString(value)
                case 17:
                    buf.WriteString("/PC=") // postal code
                    buf.WriteString(value)
                case 42:
                    buf.WriteString("/GN=") // given name
                    buf.WriteString(value)
                case 43:
                    buf.WriteString("/initials=")
                    buf.WriteString(value)
                case 44:
                    buf.WriteString("/generationQualifier=")
                    buf.WriteString(value)
                case 46:
                    buf.WriteString("/dnQualifier=")
                    buf.WriteString(value)
                case 65:
                    buf.WriteString("/pseudonym=")
                    buf.WriteString(value)
                }
            } else if t.Equal(dcNameOid) {
                buf.WriteString("/DC=") // domain component
                buf.WriteString(value)
            } else if t.Equal(emailOid) {
                buf.WriteString("/MAIL=")
                buf.WriteString(value)
            } else if t.Equal(userIDOid) {
                buf.WriteString("/UID=") // user ID
                buf.WriteString(value)
            }
        }
    }
    return buf.String()
}

This is the code to get the RDNSequence. The example gets the Subject name.

...
cert, err := x509.ParseCertificate(certData)
if err != nil {
    ...
}

var rdns pkix.RDNSequence
if _, err := asn1.Unmarshal(cert.RawSubject, &rdns); err != nil {
    ...
}

fmt.Println("Subject:", RDNSToString(&rdns))
...

来源：https://stackoverflow.com/questions/39125873/golang-subject-dn-from-x509-cert

标签

x509