feat(rsa): adds RSA varsig implementation and "common" algorithms

2025-07-07 11:25:58 -04:00
parent f9f39d363f
commit 8b710b7e23
5 changed files with 282 additions and 11 deletions
--- a/common.go
+++ b/common.go
@@ -0,0 +1,25 @@
+package varsig
+
+// RS256 produces a varsig that describes the associated algorithm defined
+// by the [IANA JOSE specification].
+//
+// [IANA JOSE specidication]: https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms
+func RS256(keyLength uint64, payloadEncoding PayloadEncoding, opts ...Option) (*RSAVarsig, error) {
+	return NewRSAVarsig(HashAlgorithmSHA256, keyLength, payloadEncoding, opts...)
+}
+
+// RS384 produces a varsig that describes the associated algorithm defined
+// by the [IANA JOSE specification].
+//
+// [IANA JOSE specidication]: https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms
+func RS384(keyLength uint64, payloadEncoding PayloadEncoding, opts ...Option) (*RSAVarsig, error) {
+	return NewRSAVarsig(HashAlgorithmSHA384, keyLength, payloadEncoding, opts...)
+}
+
+// RS512 produces a varsig that describes the associated algorithm defined
+// by the [IANA JOSE specification].
+//
+// [IANA JOSE specidication]: https://www.iana.org/assignments/jose/jose.xhtml#web-signature-encryption-algorithms
+func RS512(keyLength uint64, payloadEncoding PayloadEncoding, opts ...Option) (*RSAVarsig, error) {
+	return NewRSAVarsig(HashAlgorithmSHA512, keyLength, payloadEncoding, opts...)
+}
--- a/common_test.go
+++ b/common_test.go
@@ -0,0 +1,40 @@
+package varsig_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/selesy/go-varsig"
+)
+
+func TestRS256(t *testing.T) {
+	t.Parallel()
+
+	in := mustVarsig[varsig.RSAVarsig](t)(varsig.RS256(0x100, varsig.PayloadEncodingDAGCBOR))
+	out := roundTrip(t, in, "NAGFJBKAAnE")
+	assertRSAEqual(t, in, out)
+}
+
+func TestRS384(t *testing.T) {
+	t.Parallel()
+
+	in := mustVarsig[varsig.RSAVarsig](t)(varsig.RS384(0x100, varsig.PayloadEncodingDAGCBOR))
+	out := roundTrip(t, in, "NAGFJCCAAnE")
+	assertRSAEqual(t, in, out)
+}
+
+func TestRS512(t *testing.T) {
+	t.Parallel()
+
+	in := mustVarsig[varsig.RSAVarsig](t)(varsig.RS512(0x100, varsig.PayloadEncodingDAGCBOR))
+	out := roundTrip(t, in, "NAGFJBOAAnE")
+	assertRSAEqual(t, in, out)
+}
+
+func assertRSAEqual(t *testing.T, in, out *varsig.RSAVarsig) {
+	t.Helper()
+
+	assert.Equal(t, in.HashAlgorithm(), out.HashAlgorithm())
+	assert.Equal(t, in.KeyLength(), out.KeyLength())
+}
--- a/rsa.go
+++ b/rsa.go
@@ -0,0 +1,94 @@
+package varsig
+
+import (
+	"bytes"
+	"encoding/binary"
+
+	"github.com/multiformats/go-multicodec"
+)
+
+const SignAlgorithmRSA = SignAlgorithm(multicodec.RsaPub)
+
+var _ Varsig = (*RSAVarsig)(nil)
+
+// RSAVarsig is a varsig that encodes the parameters required to describe
+// and RSA signature.
+type RSAVarsig struct {
+	varsig[RSAVarsig]
+	hashAlg HashAlgorithm
+	sigLen  uint64
+}
+
+// NewRSAVarsig creates and validates an RSA varsig with the provided
+// parameters.
+func NewRSAVarsig(hashAlgorithm HashAlgorithm, keyLength uint64, payloadEncoding PayloadEncoding, opts ...Option) (*RSAVarsig, error) {
+	options := newOptions(opts...)
+
+	var (
+		vers = Version1
+		sig  = []byte{}
+	)
+
+	if options.ForceVersion0() {
+		vers = Version0
+		sig = options.Signature()
+	}
+
+	v := &RSAVarsig{
+		varsig: varsig[RSAVarsig]{
+			vers:    vers,
+			signAlg: SignAlgorithmRSA,
+			payEnc:  payloadEncoding,
+			sig:     sig,
+		},
+		hashAlg: hashAlgorithm,
+		sigLen:  keyLength,
+	}
+
+	return v.validateSig(v, v.sigLen)
+}
+
+// Encode returns the encoded byte formation of the RSAVarsig.
+func (v RSAVarsig) Encode() []byte {
+	buf := v.encode()
+	buf = binary.AppendUvarint(buf, uint64(v.hashAlg))
+	buf = binary.AppendUvarint(buf, v.sigLen)
+	buf = binary.AppendUvarint(buf, uint64(v.payEnc))
+	buf = append(buf, v.Signature()...)
+
+	return buf
+}
+
+// HashAlgorithm returns the hash algorithm used to has the payload content.
+func (v *RSAVarsig) HashAlgorithm() HashAlgorithm {
+	return v.hashAlg
+}
+
+// KeyLength returns the length of the RSA key used to sign the payload
+// content.
+func (v *RSAVarsig) KeyLength() uint64 {
+	return v.sigLen
+}
+
+func decodeRSA(r *bytes.Reader, vers Version, signAlg SignAlgorithm) (Varsig, error) {
+	hashAlg, err := DecodeHashAlgorithm(r)
+	if err != nil {
+		return nil, err
+	}
+
+	sigLen, err := binary.ReadUvarint(r)
+	if err != nil {
+		return nil, err
+	}
+
+	vs := &RSAVarsig{
+		varsig: varsig[RSAVarsig]{
+			vers:    vers,
+			signAlg: signAlg,
+		},
+		hashAlg: HashAlgorithm(hashAlg),
+		sigLen:  sigLen,
+	}
+
+	return vs.decodePayEncAndSig(r, vs, sigLen)
+}
--- a/rsa_test.go
+++ b/rsa_test.go
@@ -0,0 +1,96 @@
+package varsig_test
+
+import (
+	"encoding/base64"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/selesy/go-varsig"
+)
+
+func TestRSAVarsig(t *testing.T) {
+	t.Parallel()
+
+	const keyLen = 0x100
+
+	// This test uses the same RSA configuration as below but for varsig
+	// >= v1
+	example, err := base64.RawStdEncoding.DecodeString("NAGFJBKAAnE")
+	require.NoError(t, err)
+
+	t.Run("Decode", func(t *testing.T) {
+		t.Parallel()
+
+		vs, err := varsig.Decode(example)
+		require.NoError(t, err)
+
+		rsaVs, ok := vs.(*varsig.RSAVarsig)
+		require.True(t, ok)
+
+		assert.Equal(t, varsig.Version1, rsaVs.Version())
+		assert.Equal(t, varsig.SignAlgorithmRSA, rsaVs.SignatureAlgorithm())
+		assert.Equal(t, varsig.HashAlgorithmSHA256, rsaVs.HashAlgorithm())
+		assert.Equal(t, varsig.PayloadEncodingDAGCBOR, rsaVs.PayloadEncoding())
+		assert.Equal(t, uint64(keyLen), rsaVs.KeyLength())
+		assert.Len(t, rsaVs.Signature(), 0)
+	})
+
+	t.Run("Encode", func(t *testing.T) {
+		t.Parallel()
+
+		rsaVarsig, err := varsig.NewRSAVarsig(
+			varsig.HashAlgorithmSHA256,
+			keyLen,
+			varsig.PayloadEncodingDAGCBOR,
+		)
+		require.NoError(t, err)
+
+		assert.Equal(t, example, rsaVarsig.Encode())
+		t.Log(base64.RawStdEncoding.EncodeToString(rsaVarsig.Encode()))
+	})
+}
+
+func TestUCANExample(t *testing.T) {
+	t.Parallel()
+
+	const keyLen = 0x100
+
+	// This test is the value shown in the UCAN v1.0.0 example, which is
+	// an RSA varsig < v1 encoded as RS256 with a key length of 0x100
+	// bytes and DAG-CBOR payload encoding.
+	example, err := base64.RawStdEncoding.DecodeString("NIUkEoACcQ")
+	require.NoError(t, err)
+
+	t.Run("Decode", func(t *testing.T) {
+		t.Parallel()
+
+		vs, err := varsig.Decode(example)
+		require.ErrorIs(t, err, varsig.ErrMissingSignature)
+
+		rsaVs, ok := vs.(*varsig.RSAVarsig)
+		require.True(t, ok)
+
+		assert.Equal(t, varsig.Version0, rsaVs.Version())
+		assert.Equal(t, varsig.SignAlgorithmRSA, rsaVs.SignatureAlgorithm())
+		assert.Equal(t, varsig.HashAlgorithmSHA256, rsaVs.HashAlgorithm())
+		assert.Equal(t, varsig.PayloadEncodingDAGCBOR, rsaVs.PayloadEncoding())
+		assert.Equal(t, uint64(keyLen), rsaVs.KeyLength())
+		assert.Len(t, rsaVs.Signature(), 0)
+	})
+
+	t.Run("Encode", func(t *testing.T) {
+		t.Parallel()
+
+		rsaVarsig, err := varsig.NewRSAVarsig(
+			varsig.HashAlgorithmSHA256,
+			keyLen,
+			varsig.PayloadEncodingDAGCBOR,
+			varsig.WithForceVersion0([]byte{}),
+		)
+		require.ErrorIs(t, err, varsig.ErrMissingSignature)
+
+		assert.Equal(t, example, rsaVarsig.Encode())
+	})
+}
--- a/varsig_test.go
+++ b/varsig_test.go
@@ -1,7 +1,9 @@
 package varsig_test

 import (
+	"encoding/base64"
 	"encoding/hex"
+	"errors"
 	"io"
 	"testing"

@@ -157,17 +159,31 @@ func TestDecode(t *testing.T) {
 	})
 }

-// func TestReadUvarint(t *testing.T) {
-// 	t.Parallel()
+func mustVarsig[T varsig.Varsig](t *testing.T) func(*T, error) *T {
+	t.Helper()

-// 	var r io.ByteReader = &bytes.Reader{}
+	return func(v *T, err error) *T {
+		if err != nil && ((*v).Version() != varsig.Version0 || !errors.Is(err, varsig.ErrMissingSignature)) {
+			t.Error(err)
+		}

-// 	u, err := binary.ReadUvarint(r)
-// 	require.ErrorIs(t, err, io.EOF)
-// 	assert.Equal(t, uint64(0), u)
+		return v
+	}
+}

-// 	var buf []byte
-// 	buf = binary.AppendUvarint(buf, 0x100)
-// 	t.Log("0x100 varint:", hex.EncodeToString(buf))
-// 	t.Fail()
-// }
+func roundTrip[T varsig.Varsig](t *testing.T, in T, expEncHex string) T {
+	data := in.Encode()
+	assert.Equal(t, expEncHex, base64.RawStdEncoding.EncodeToString(data))
+
+	out, err := varsig.Decode(in.Encode())
+	if err != nil && (out.Version() != varsig.Version0 || !errors.Is(err, varsig.ErrMissingSignature)) {
+		t.Fail()
+	}
+
+	assert.Equal(t, in.Version(), out.Version())
+	assert.Equal(t, in.SignatureAlgorithm(), out.SignatureAlgorithm())
+	assert.Equal(t, in.PayloadEncoding(), out.PayloadEncoding())
+	assert.Equal(t, in.Signature(), out.Signature())
+
+	return out.(T)
+}