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@KEINOS(KEINOS)inQiitadonユーザー会

【Golang】OpenPGP 鍵に Notation 情報を埋め込む【RFC9580, packet v6】

Last updated at Posted at 2025-06-28

Go 言語（以下 golang）で、RFC9580（packet v6）に準拠した OpenPGP 鍵を生成しつつ、鍵に Notation 情報も埋め込みたい。

TL; DR （とりあえずソースコード）

まずは RFC9580 準拠の OpenPGP 鍵を生成するコードです。

ポイントは、単純に鍵を生成する方法と違い、プロファイル（profile.Custom）の SetKeyAlgorithm フィールド内の関数変数をオーバーライドしている箇所です。

また、この例ではセキュリティ・レベルを "High" に設定しています。そのため内部の楕円曲線方式が Ed25519（Standard）から Ed448（High）に強化されています。

  • go version go1.24.4 darwin/amd64
package main

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/ProtonMail/go-crypto/openpgp/packet"
	"github.com/ProtonMail/gopenpgp/v3/constants"
	"github.com/ProtonMail/gopenpgp/v3/crypto"
	"github.com/ProtonMail/gopenpgp/v3/profile"
)

func main() {
	yourName := "myName"
	yourEmail := "my@example.com"
    yourDomain := "example.com"
	yourWeb := "https://blog.example.com/"

	// Create a new profile based on RFC9580.
	// * Ref: https://www.ietf.org/rfc/rfc9580.pdf
	profRFC9580 := profile.RFC9580()

	// Override the SetKeyAlgorithm function variable to set custom notations.
	tmpSetKeyAlgorithm := profRFC9580.SetKeyAlgorithm

	profRFC9580.SetKeyAlgorithm = func(cfg *packet.Config, securityLevel int8) {
		tmpSetKeyAlgorithm(cfg, securityLevel)

		// Set Notations for the key.
		cfg.SignatureNotations = []*packet.Notation{
			{
				Name:            "ariadne.id",
				Value:           []byte("dns:" + yourDomain),
				IsHumanReadable: true,
			},
			{
				Name:            "ariadne.id",
				Value:           []byte(yourWeb),
				IsHumanReadable: true,
			},
		}
	}

	// Create a PGP handler with the RFC9580 profile.
	pgpHandler := crypto.PGPWithProfile(profRFC9580)

	// Create a new PGP key generator with the desired user ID.
	pgpGenerator := pgpHandler.KeyGeneration().AddUserId(yourName, yourEmail).New()

	// Generate the key with high security level. (choices: constants.StandardSecurity)
	privKey, err := pgpGenerator.GenerateKeyWithSecurity(constants.HighSecurity)
	if err != nil {
		panic(err)
	}

	// Get the ASCII armored private key
	fmt.Println("Private Key (ASCII Armored):")
	privKeyAsc, err := privKey.Armor()
	if err != nil {
		panic(err)
	}

	fmt.Println(privKeyAsc)

	// Get the ASCII armored public key
	fmt.Println("Public Key (ASCII Armored):")
	pubKeyAsc, err := privKey.GetArmoredPublicKey()
	if err != nil {
		panic(err)
	}

	fmt.Println(pubKeyAsc)

	// Save the public key to a file
	pathFileKey := filepath.Join("..", "testdata", "pubKey_RFC9580_w_notations.asc")
	if err := os.WriteFile(pathFileKey, []byte(pubKeyAsc), 0644); err != nil {
		panic(err)
	}
}
  • オンラインで動作をみる @ GoPlayground
    • モジュールが重いので、たまにタイムアウトします。一呼吸おいて数回リトライしてください

鍵に埋め込まれた Notation を golang で読み込むには以下の記事をご覧ください。

TS; DR （検証してみる）

ここで、上記で生成された公開鍵を golang 以外の実装で読み込めるか検証したいと思ったのですが、重大な事実が発覚。

なんと、天下の GnuPG は RFC9580 に反対しており、この（RFC9580, OpenGPG v6）鍵は GnuPG では使えません。

そこで、RFC9580 の Rust による実装である Sequoia PGP（sq コマンド）で読み込めるか検証してみたいと思います。

まずは、鍵がちゃんと生成されているかの lint テストです。

$ sq cert lint --cert-file testdata/pubKey_RFC9580_w_notations.asc
Examined 1 certificate.
  0 certificates are invalid and were not linted. (GOOD)
  1 certificate was linted.
  0 of the 1 certificates (0%) have at least one issue. (GOOD)
0 of the linted certificates were revoked.
  0 of the 0 certificates has revocation certificates that are weaker than the certificate and should be recreated. (GOOD)
0 of the linted certificates were expired.
1 of the non-revoked linted certificate has at least one
non-revoked User ID:
  0 have at least one User ID protected by SHA-1. (GOOD)
  0 have all User IDs protected by SHA-1. (GOOD)
1 of the non-revoked linted certificates has at least one
non-revoked, live subkey:
  0 have at least one non-revoked, live subkey with a binding signature that uses SHA-1. (GOOD)
0 of the non-revoked linted certificates have at least one
non-revoked, live, signing-capable subkey:
  0 certificates have at least one non-revoked, live, signing-capable subkey with a strong binding signature, but a backsig that uses SHA-1. (GOOD)

すべてが (GOOD) なので、鍵としては機能している（読み込める）ようです。

次に、鍵の情報を取得してみたいと思います。

以下の２行（Notation）が、署名パケット（Signature Packet）に各々埋め込まれれていることを確認してください。

  • Notation: ariadne.id: dns:example.com
  • Notation: ariadne.id: https://blog.example.com/
$ sq packet dump testdata/pubKey_RFC9580_w_notations.asc
Public-Key Packet, new CTB, 67 bytes
    Version: 6
    Creation time: 2025-06-28 00:42:36 UTC
    Pk algo: Ed448
    Pk size: 456 bits
    Fingerprint: 2E381AB387334AA0A381957499A4AA7B728D074FFE4592DB28E36B56A8D8D1AB
    KeyID: 2E381AB387334AA0
  
Signature Packet, new CTB, 312 bytes
    Version: 6
    Type: DirectKey
    Pk algo: Ed448
    Hash algo: SHA512
    Hashed area:
      Signature creation time: 2025-06-28 00:42:36 UTC (critical)
      Symmetric algo preferences: AES256, AES128
      Notation: ariadne.id: dns:example.com
      Notation: ariadne.id: https://blog.example.com/
      Hash preferences: SHA512, SHA256
      Compression preferences: Uncompressed, Zlib
      Key flags: CS (critical)
      Features: SEIPDv1, SEIPDv2
      Issuer Fingerprint: 2E381AB387334AA0A381957499A4AA7B728D074FFE4592DB28E36B56A8D8D1AB (critical)
      AEAD preferences: AES256+OCB, AES128+OCB
    Digest prefix: A71C
    Salt: 55DDEEDDBD719A981BD69F58E1D5847354C2DF4C97552AEB5BF8AABBBD455B12
    Level: 0 (signature over data)
  
User ID Packet, new CTB, 23 bytes
    Value: myName <my@example.com>
  
Signature Packet, new CTB, 291 bytes
    Version: 6
    Type: PositiveCertification
    Pk algo: Ed448
    Hash algo: SHA512
    Hashed area:
      Signature creation time: 2025-06-28 00:42:36 UTC (critical)
      Notation: ariadne.id: dns:example.com
      Notation: ariadne.id: https://blog.example.com/
      Primary User ID: true
      Issuer Fingerprint: 2E381AB387334AA0A381957499A4AA7B728D074FFE4592DB28E36B56A8D8D1AB (critical)
    Digest prefix: 37DE
    Salt: FB98200CD8C2F0CF5B277E379906DEE0DC16C99E22D11A3C0439B24FC8C724C6
    Level: 0 (signature over data)
  
Public-Subkey Packet, new CTB, 66 bytes
    Version: 6
    Creation time: 2025-06-28 00:42:36 UTC
    Pk algo: X448
    Pk size: 448 bits
    Fingerprint: 55DB4AB4E72CD0F1D1EB0FF40010E47A77CD57F3ECF8F38C2644ADED8B3222E8
    KeyID: 55DB4AB4E72CD0F1
  
Signature Packet, new CTB, 291 bytes
    Version: 6
    Type: SubkeyBinding
    Pk algo: Ed448
    Hash algo: SHA512
    Hashed area:
      Signature creation time: 2025-06-28 00:42:36 UTC (critical)
      Notation: ariadne.id: dns:example.com
      Notation: ariadne.id: https://blog.example.com/
      Key flags: EtEr (critical)
      Issuer Fingerprint: 2E381AB387334AA0A381957499A4AA7B728D074FFE4592DB28E36B56A8D8D1AB (critical)
    Digest prefix: B400
    Salt: B6DEBB6E85516FA7AD60D10DC9B40CC518076693287C6A3B134D04F2892E3AED
    Level: 0 (signature over data)
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