feat: added PKCS#7 envelope implementation

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/golang-jwt/jwt/v4 v4.5.2
 	github.com/notaryproject/tspclient-go v1.0.0
 	github.com/veraison/go-cose v1.3.0
+	go.mozilla.org/pkcs7 v0.9.0
 	golang.org/x/crypto v0.37.0
 )
 

go.sum

@@ -8,5 +8,7 @@ github.com/veraison/go-cose v1.3.0 h1:2/H5w8kdSpQJyVtIhx8gmwPJ2uSz1PkyWFx0idbd7r
 github.com/veraison/go-cose v1.3.0/go.mod h1:df09OV91aHoQWLmy1KsDdYiagtXgyAwAl8vFeFn1gMc=
 github.com/x448/float16 v0.8.4 h1:qLwI1I70+NjRFUR3zs1JPUCgaCXSh3SW62uAKT1mSBM=
 github.com/x448/float16 v0.8.4/go.mod h1:14CWIYCyZA/cWjXOioeEpHeN/83MdbZDRQHoFcYsOfg=
+go.mozilla.org/pkcs7 v0.9.0 h1:yM4/HS9dYv7ri2biPtxt8ikvB37a980dg69/pKmS+eI=
+go.mozilla.org/pkcs7 v0.9.0/go.mod h1:SNgMg+EgDFwmvSmLRTNKC5fegJjB7v23qTQ0XLGUNHk=
 golang.org/x/crypto v0.37.0 h1:kJNSjF/Xp7kU0iB2Z+9viTPMW4EqqsrywMXLJOOsXSE=
 golang.org/x/crypto v0.37.0/go.mod h1:vg+k43peMZ0pUMhYmVAWysMK35e6ioLh3wB8ZCAfbVc=

signature/pkcs7/conformance_test.go

@@ -0,0 +1,84 @@
+// Copyright The Notary Project Authors.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pkcs7
+
+import (
+	"crypto"
+	"crypto/rsa"
+	"crypto/sha256"
+	"testing"
+
+	gopkcs7 "go.mozilla.org/pkcs7"
+
+	"github.com/notaryproject/notation-core-go/signature"
+)
+
+// TestConformance asserts that Sign() produces a PKCS#7 SignedData that meets
+// the kernel dm-verity profile: RSASSA-PKCS#1 v1.5 over SHA-256, no signed
+// attributes, detached content, single signer.
+func TestConformance(t *testing.T) {
+	signer := newRSATestSigner()
+	encoded, err := NewEnvelope().Sign(&signature.SignRequest{
+		Payload: signature.Payload{ContentType: MediaTypeEnvelope, Content: []byte(testPayload)},
+		Signer:  signer,
+	})
+	if err != nil {
+		t.Fatalf("Sign() error: %v", err)
+	}
+
+	p7, err := gopkcs7.Parse(encoded)
+	if err != nil {
+		t.Fatalf("Parse() error: %v", err)
+	}
+
+	if got, want := len(p7.Signers), 1; got != want {
+		t.Fatalf("Signers = %d, want %d", got, want)
+	}
+
+	// Cert chain must be leaf + root. dm-verity has no intermediates.
+	if got, want := len(p7.Certificates), 2; got != want {
+		t.Fatalf("Certificates = %d, want %d (leaf + root)", got, want)
+	}
+	if !p7.Certificates[0].Equal(signer.certs[0]) {
+		t.Errorf("Certificates[0] is not the leaf certificate")
+	}
+	if !p7.Certificates[1].Equal(signer.certs[1]) {
+		t.Errorf("Certificates[1] is not the root certificate")
+	}
+
+	si := p7.Signers[0]
+	if !si.DigestAlgorithm.Algorithm.Equal(gopkcs7.OIDDigestAlgorithmSHA256) {
+		t.Errorf("DigestAlgorithm = %v, want SHA-256", si.DigestAlgorithm.Algorithm)
+	}
+	if !si.DigestEncryptionAlgorithm.Algorithm.Equal(gopkcs7.OIDEncryptionAlgorithmRSA) {
+		t.Errorf("DigestEncryptionAlgorithm = %v, want rsaEncryption", si.DigestEncryptionAlgorithm.Algorithm)
+	}
+	if len(si.AuthenticatedAttributes) != 0 {
+		t.Errorf("AuthenticatedAttributes len = %d, want 0", len(si.AuthenticatedAttributes))
+	}
+	if len(p7.Content) != 0 {
+		t.Errorf("Content len = %d, want 0 (must be detached)", len(p7.Content))
+	}
+
+	// Independently verify the bytes are RSASSA-PKCS#1 v1.5 over SHA-256
+	// of the payload.
+	digest := sha256.Sum256([]byte(testPayload))
+	pub, ok := signer.certs[0].PublicKey.(*rsa.PublicKey)
+	if !ok {
+		t.Fatalf("leaf public key is %T, want *rsa.PublicKey", signer.certs[0].PublicKey)
+	}
+	if err := rsa.VerifyPKCS1v15(pub, crypto.SHA256, digest[:], si.EncryptedDigest); err != nil {
+		t.Fatalf("rsa.VerifyPKCS1v15 over SHA-256(payload) failed: %v", err)
+	}
+}

signature/pkcs7/envelope.go

@@ -0,0 +1,262 @@
+// Copyright The Notary Project Authors.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package pkcs7 provides a PKCS#7/CMS signature envelope for dm-verity
+// signing.
+package pkcs7
+
+import (
+	"crypto"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/notaryproject/notation-core-go/signature"
+	gopkcs7 "go.mozilla.org/pkcs7"
+)
+
+// ErrDetachedNotVerifiable is returned by Envelope.Verify. The dm-verity
+// PKCS#7 envelope is detached and Envelope.Verify takes no payload, so it
+// cannot perform cryptographic verification. Verify the dm-verity root
+// hash out-of-band.
+var ErrDetachedNotVerifiable = errors.New("PKCS#7 dm-verity envelope is detached; verify against the dm-verity root hash out-of-band")
+
+// MediaTypeEnvelope is the PKCS#7 signature envelope media type.
+const MediaTypeEnvelope = "application/pkcs7-signature"
+
+func init() {
+	if err := signature.RegisterEnvelopeType(MediaTypeEnvelope, NewEnvelope, ParseEnvelope); err != nil {
+		panic(err)
+	}
+}
+
+// envelope holds a parsed PKCS#7 signature. raw is canonical; certs and
+// sigBytes are caches derived from raw.
+type envelope struct {
+	raw      []byte
+	certs    []*x509.Certificate
+	sigBytes []byte
+}
+
+// NewEnvelope creates a new PKCS#7 envelope.
+//
+// The dm-verity profile requires a SignerInfo with no signed attributes,
+// so this envelope is not wrapped with base.Envelope (which injects a
+// signing-time signed attribute).
+func NewEnvelope() signature.Envelope {
+	return &envelope{}
+}
+
+// ParseEnvelope parses PKCS#7 DER bytes into an envelope.
+func ParseEnvelope(envelopeBytes []byte) (env signature.Envelope, err error) {
+	// Convert any panic from the underlying parser to a typed error.
+	defer func() {
+		if r := recover(); r != nil {
+			env = nil
+			err = &signature.InvalidSignatureError{Msg: fmt.Sprintf("malformed PKCS#7 envelope: %v", r)}
+		}
+	}()
+	p7, err := gopkcs7.Parse(envelopeBytes)
+	if err != nil {
+		return nil, &signature.InvalidSignatureError{Msg: err.Error()}
+	}
+
+	var sigBytes []byte
+	if len(p7.Signers) > 0 {
+		sigBytes = p7.Signers[0].EncryptedDigest
+	}
+
+	return &envelope{
+		raw:      envelopeBytes,
+		certs:    p7.Certificates,
+		sigBytes: sigBytes,
+	}, nil
+}
+
+// Sign implements signature.Envelope for the dm-verity profile: RSA-2048 +
+// SHA-256 + RSASSA-PKCS#1 v1.5, detached, no signed attributes. The actual
+// signing is done by req.Signer; gopkcs7 only wraps the resulting bytes in
+// CMS SignedData. Sign verifies the signer's output against certs[0]
+// before wrapping.
+func (e *envelope) Sign(req *signature.SignRequest) ([]byte, error) {
+	if err := validateSignRequest(req); err != nil {
+		return nil, err
+	}
+
+	sig, certs, err := req.Signer.Sign(req.Payload.Content)
+	if err != nil {
+		return nil, &signature.InvalidSignatureError{Msg: fmt.Sprintf("signing failed: %v", err)}
+	}
+	if err := verifySignerOutput(req.Payload.Content, sig, certs); err != nil {
+		return nil, err
+	}
+
+	sd, err := gopkcs7.NewSignedData(req.Payload.Content)
+	if err != nil {
+		return nil, &signature.InvalidSignatureError{Msg: err.Error()}
+	}
+
+	// dm-verity profile: SHA-256 digest, RSASSA-PKCS#1 v1.5 signature,
+	// no signed attributes, detached content.
+	sd.SetDigestAlgorithm(gopkcs7.OIDDigestAlgorithmSHA256)
+	sd.SetEncryptionAlgorithm(gopkcs7.OIDEncryptionAlgorithmRSA)
+	adapter := &signerAdapter{sig: sig, certs: certs}
+	if err := sd.SignWithoutAttr(certs[0], adapter, gopkcs7.SignerInfoConfig{}); err != nil {
+		return nil, &signature.InvalidSignatureError{Msg: err.Error()}
+	}
+	for i := 1; i < len(certs); i++ {
+		sd.AddCertificate(certs[i])
+	}
+	sd.Detach()
+
+	encoded, err := sd.Finish()
+	if err != nil {
+		return nil, &signature.InvalidSignatureError{Msg: err.Error()}
+	}
+
+	// Re-parse to populate caches.
+	p7, err := gopkcs7.Parse(encoded)
+	if err != nil {
+		return nil, &signature.InvalidSignatureError{
+			Msg: fmt.Sprintf("self-parse failed after Sign: %v", err),
+		}
+	}
+	e.raw = encoded
+	e.certs = certs
+	if len(p7.Signers) > 0 {
+		e.sigBytes = p7.Signers[0].EncryptedDigest
+	}
+	return encoded, nil
+}
+
+// validateSignRequest enforces the dm-verity profile: no signed-attribute
+// fields, RSA-2048 key only.
+func validateSignRequest(req *signature.SignRequest) error {
+	if !req.SigningTime.IsZero() {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope does not support SigningTime"}
+	}
+	if !req.Expiry.IsZero() {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope does not support Expiry"}
+	}
+	if req.SigningScheme != "" {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope does not support SigningScheme"}
+	}
+	if req.SigningAgent != "" {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope does not support SigningAgent"}
+	}
+	if len(req.ExtendedSignedAttributes) > 0 {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope does not support ExtendedSignedAttributes"}
+	}
+
+	if req.Signer == nil {
+		return &signature.InvalidSignRequestError{Msg: "dm-verity PKCS#7 envelope requires a non-nil Signer"}
+	}
+	keySpec, err := req.Signer.KeySpec()
+	if err != nil {
+		return &signature.InvalidSignRequestError{Msg: err.Error()}
+	}
+
+	// dm-verity profile: RSA-2048 + SHA-256 + RSASSA-PKCS#1 v1.5 only.
+	if keySpec.Type != signature.KeyTypeRSA {
+		return &signature.UnsupportedSigningKeyError{
+			Msg: fmt.Sprintf("dm-verity PKCS#7 envelope requires an RSA key; got %v", keySpec.Type),
+		}
+	}
+	if keySpec.Size != 2048 {
+		return &signature.UnsupportedSigningKeyError{
+			Msg: fmt.Sprintf("dm-verity PKCS#7 envelope requires RSA-2048; got RSA-%d", keySpec.Size),
+		}
+	}
+	return nil
+}
+
+// verifySignerOutput checks that sig is RSASSA-PKCS#1 v1.5 over SHA-256 of
+// payload under certs[0]'s public key.
+func verifySignerOutput(payload, sig []byte, certs []*x509.Certificate) error {
+	if len(certs) == 0 {
+		return &signature.InvalidSignatureError{Msg: "no certificates returned from signer"}
+	}
+	pub, ok := certs[0].PublicKey.(*rsa.PublicKey)
+	if !ok {
+		return &signature.UnsupportedSigningKeyError{
+			Msg: fmt.Sprintf("leaf certificate public key is %T, want *rsa.PublicKey", certs[0].PublicKey),
+		}
+	}
+	digest := sha256.Sum256(payload)
+	if err := rsa.VerifyPKCS1v15(pub, crypto.SHA256, digest[:], sig); err != nil {
+		return &signature.InvalidSignatureError{
+			Msg: fmt.Sprintf("signer did not produce RSASSA-PKCS#1 v1.5 over SHA-256: %v", err),
+		}
+	}
+	return nil
+}
+
+// signerAdapter wraps a pre-computed signature so it can be passed to a
+// gopkcs7.SignedData (which expects a crypto.Signer). It is single-use:
+// Sign must be called at most once.
+type signerAdapter struct {
+	sig   []byte              // pre-computed signature from actual signer
+	certs []*x509.Certificate // certificate chain
+	used  bool                // set on first Sign call
+}
+
+// Public returns the leaf certificate's public key.
+func (a *signerAdapter) Public() crypto.PublicKey {
+	if len(a.certs) == 0 {
+		panic("pkcs7: signerAdapter constructed with empty cert chain")
+	}
+	return a.certs[0].PublicKey
+}
+
+// Sign returns the pre-computed signature. The digest and opts arguments
+// are ignored. Panics if called more than once.
+func (a *signerAdapter) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
+	if a.used {
+		panic("pkcs7: signerAdapter.Sign called more than once")
+	}
+	a.used = true
+	return a.sig, nil
+}
+
+// Verify always returns ErrDetachedNotVerifiable for a populated envelope.
+func (e *envelope) Verify() (*signature.EnvelopeContent, error) {
+	if e.raw == nil {
+		return nil, &signature.SignatureEnvelopeNotFoundError{}
+	}
+	return nil, ErrDetachedNotVerifiable
+}
+
+// Content implements signature.Envelope.
+//
+// SignerInfo.SignatureAlgorithm is the zero value: signature.Algorithm has
+// no constant for RSASSA-PKCS#1 v1.5. Read the certificate chain or the
+// CMS digestEncryptionAlgorithm OID instead.
+func (e *envelope) Content() (*signature.EnvelopeContent, error) {
+	if e.raw == nil {
+		return nil, &signature.SignatureEnvelopeNotFoundError{}
+	}
+	return &signature.EnvelopeContent{
+		SignerInfo: signature.SignerInfo{
+			CertificateChain: e.certs,
+			Signature:        e.sigBytes,
+		},
+		Payload: signature.Payload{
+			ContentType: MediaTypeEnvelope,
+		},
+	}, nil
+}
+
+var _ signature.Envelope = (*envelope)(nil)