proposal: crypto/x509: provide function to convert from x509.OID to asn1.ObjectIdentifier

Proposal Details

The new OID type in the x509 package contains a function to convert from asn1.ObjectIdentifier to the new OID type. It would be helpful to have a reverse function as well as part of this package. It could look like the following:

func ASN1OIDFromOID(oid x509.OID) asn1.ObjectIdentifier {
	parts := strings.Split(oid.String(), ".")
	result := make(asn1.ObjectIdentifier, len(parts))
	for i, part := range parts {
		component, err := strconv.Atoi(part)
		if err != nil {
			panic(err)
		}
		result[i] = component
	}
	return result
}

Related Issues

encoding/asn1: add utility function for parsing object-identifier strings #15523 (closed)
crypto/x509: introduce new robust OID type & use it for certificate policies #60665 (closed)
crypto/x509: make OID have text, binary marshal methods #66249 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

It would have to return either a bool or an error, since OID supports elements > 31bits, whereas asn1.ObjectIdentifier does not not. I think bool would be enough here, since there is only a single error condition.

Not necessarily opposed, but where do you need the asn1.ObjectIdentifier? Because ideally we'd instead add support for x509.OID there.

Not necessarily opposed, but where do you need the asn1.ObjectIdentifier? Because ideally we'd instead add support for x509.OID there.

encoding/asn1 fails when marshalling a x509.oid. Please see the following repros:

package main

import (
	"crypto/x509"
	"encoding/asn1"
	"fmt"
	"testing"
)

// Showcase that encoding/asn1 cannot marshal crypto/x509.OID directly.
func TestX509OIDASN1MarshalError(t *testing.T) {
	oid, _ := x509.OIDFromInts([]uint64{1, 2, 840, 113533, 7, 66, 13})

	encoded, err := asn1.Marshal(oid)
	if err == nil {
		fmt.Printf("Encoded ASN.1 data: %x\n", encoded)
		t.Fatal("expected asn1.Marshal to fail when given x509.OID, but it succeeded")
	}

	fmt.Printf("Error when marshaling x509.OID with encoding/asn1:\n  %v\n", err)
}

// Showcase that encoding/asn1 can marshal asn1.ObjectIdentifier directly.
func TestASN1ObjectIdentifierMarshalSuccess(t *testing.T) {
	oid := asn1.ObjectIdentifier{1, 2, 840, 113533, 7, 66, 13}

	encoded, err := asn1.Marshal(oid)
	if err != nil {
		t.Fatalf("asn1.Marshal failed: %v", err)
	}

	fmt.Printf("Successfully marshaled asn1.ObjectIdentifier with encoding/asn1\n")
	fmt.Printf("Encoded ASN.1 data: %x\n", encoded)
}

This is especially annoying since OIDs and ASN.1 are closely related with each other.

@FiloSottile

@FiloSottile do you think we could strive to enhance the https://pkg.go.dev/encoding/asn1#Marshal function to support also x509.OIDs?

No, since this would cause a circular dep. We could move OID to asn1 and make x509.OID an alias though.

I mean, we could cheat, like asserting against

interface {
    EqualASN1OID(other asn1.ObjectIdentifier) bool
    MarshalBinary() ([]byte, error)
}

and go from there.

It definitely is surprising that encoding/asn1 can't encode crypto/x509.OID.

we could cheat

I think we could also cheat by moving OID to an internal package and making crypto.X509 an alias to it.

Yeah but that makes the methods move to the internal package's godoc page.

how would we proceed with this topic?

Navigation Menu

Repository navigation

proposal: crypto/x509: provide function to convert from x509.OID to asn1.ObjectIdentifier #81363

Proposal Details

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

proposal: crypto/x509: provide function to convert from x509.OID to asn1.ObjectIdentifier #81363

Description

Proposal Details

Activity

gabyhelp commented on Sep 4, 2026

mateusz834 commented on Sep 5, 2026

FiloSottile commented on Sep 5, 2026

RufusJWB commented on Sep 5, 2026

RufusJWB commented on Sep 10, 2026

mateusz834 commented on Sep 10, 2026

FiloSottile commented on Sep 10, 2026

mateusz834 commented on Sep 10, 2026

FiloSottile commented on Sep 10, 2026

RufusJWB commented on Sep 24, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions