fix: corpus image generation

Add OptSignWithoutPGPSignatureSalt, which disables randomization of
signature generation, and use that in the corpus to generate images
deterministically.

Update corpus images and related golden files to reflect the signatures
generated by the new version of go-crypto.

internal/app/siftool/testdata/TestApp_Info/DataSignature.golden

@@ -3,6 +3,6 @@
   Group ID:   NONE
   Linked ID:  1 (G)
   Offset:     303104
-  Size:       1054
+  Size:       1048
   Hash Type:  SHA-256
   Entity:     12045C8C0B1004D058DE4BEDA20C27EE7FF7BA84

internal/app/siftool/testdata/TestApp_List/OneGroupSignedPGP.golden

@@ -3,4 +3,4 @@ ID   |GROUP   |LINK    |SIF POSITION (start-end)  |TYPE
 ------------------------------------------------------------------------------
 1    |1       |NONE    |32768-32772               |FS (Raw/System/386)
 2    |1       |NONE    |36864-40960               |FS (Squashfs/*System/386)
-3    |NONE    |1   (G) |40960-42014               |Signature (SHA-256)
+3    |NONE    |1   (G) |40960-42008               |Signature (SHA-256)

internal/app/siftool/testdata/TestApp_List/TwoGroupsSignedPGP.golden

@@ -4,5 +4,5 @@ ID   |GROUP   |LINK    |SIF POSITION (start-end)  |TYPE
 1    |1       |NONE    |32768-32772               |FS (Raw/System/386)
 2    |1       |NONE    |36864-40960               |FS (Squashfs/*System/386)
 3    |2       |NONE    |40960-303104              |FS (Ext3/System/amd64)
-4    |NONE    |1   (G) |303104-304158             |Signature (SHA-256)
-5    |NONE    |2   (G) |304158-305013             |Signature (SHA-256)
+4    |NONE    |1   (G) |303104-304152             |Signature (SHA-256)
+5    |NONE    |2   (G) |304152-305001             |Signature (SHA-256)

pkg/integrity/clearsign.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2020-2023, Sylabs Inc. All rights reserved.
+// Copyright (c) 2020-2024, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the LICENSE.md file
 // distributed with the sources of this project regarding your rights to use or distribute this
 // software.
@@ -11,7 +11,6 @@ import (
 	"crypto"
 	"errors"
 	"io"
-	"time"
 
 	"github.com/ProtonMail/go-crypto/openpgp"
 	"github.com/ProtonMail/go-crypto/openpgp/clearsign"
@@ -25,14 +24,12 @@ type clearsignEncoder struct {
 	config *packet.Config
 }
 
-// newClearsignEncoder returns an encoder that signs messages in clear-sign format using entity e.
-// If timeFunc is not nil, it is used to generate signature timestamps.
-func newClearsignEncoder(e *openpgp.Entity, timeFunc func() time.Time) *clearsignEncoder {
+// newClearsignEncoder returns an encoder that signs messages in clear-sign format using entity e,
+// according to config.
+func newClearsignEncoder(e *openpgp.Entity, config *packet.Config) *clearsignEncoder {
 	return &clearsignEncoder{
-		e: e,
-		config: &packet.Config{
-			Time: timeFunc,
-		},
+		e:      e,
+		config: config,
 	}
 }
 

pkg/integrity/clearsign_test.go

@@ -39,12 +39,12 @@ func Test_clearsignEncoder_signMessage(t *testing.T) {
 	}{
 		{
 			name:    "EncryptedKey",
-			en:      newClearsignEncoder(encrypted, fixedTime),
+			en:      newClearsignEncoder(encrypted, &packet.Config{Time: fixedTime}),
 			wantErr: true,
 		},
 		{
 			name:     "OK",
-			en:       newClearsignEncoder(e, fixedTime),
+			en:       newClearsignEncoder(e, &packet.Config{Time: fixedTime}),
 			de:       newClearsignDecoder(openpgp.EntityList{e}),
 			wantHash: crypto.SHA256,
 		},

pkg/integrity/sign.go

@@ -17,6 +17,7 @@ import (
 	"time"
 
 	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
 	"github.com/sigstore/sigstore/pkg/signature"
 	"github.com/sylabs/sif/v2/pkg/sif"
 )
@@ -179,13 +180,14 @@ func (gs *groupSigner) sign(ctx context.Context) (sif.DescriptorInput, error) {
 }
 
 type signOpts struct {
-	ss            []signature.Signer
-	e             *openpgp.Entity
-	groupIDs      []uint32
-	objectIDs     [][]uint32
-	timeFunc      func() time.Time
-	deterministic bool
-	ctx           context.Context //nolint:containedctx
+	ss                      []signature.Signer
+	e                       *openpgp.Entity
+	groupIDs                []uint32
+	objectIDs               [][]uint32
+	timeFunc                func() time.Time
+	deterministic           bool
+	ctx                     context.Context //nolint:containedctx
+	withoutPGPSignatureSalt bool
 }
 
 // SignerOpt are used to configure so.
@@ -257,6 +259,16 @@ func OptSignWithContext(ctx context.Context) SignerOpt {
 	}
 }
 
+// OptSignWithoutPGPSignatureSalt disables the addition of a salt notation for v4 and v5 PGP keys.
+// While this increases determinism, it should be used with caution as the salt notation increases
+// protection for certain kinds of attacks.
+func OptSignWithoutPGPSignatureSalt() SignerOpt {
+	return func(so *signOpts) error {
+		so.withoutPGPSignatureSalt = true
+		return nil
+	}
+}
+
 // withGroupedObjects splits the objects represented by ids into object groups, and calls fn once
 // per object group.
 func withGroupedObjects(f *sif.FileImage, ids []uint32, fn func(uint32, []uint32) error) error {
@@ -339,11 +351,10 @@ func NewSigner(f *sif.FileImage, opts ...SignerOpt) (*Signer, error) {
 	case so.ss != nil:
 		en = newDSSEEncoder(so.ss)
 	case so.e != nil:
-		timeFunc := time.Now
-		if so.timeFunc != nil {
-			timeFunc = so.timeFunc
-		}
-		en = newClearsignEncoder(so.e, timeFunc)
+		en = newClearsignEncoder(so.e, &packet.Config{
+			Time:                                  so.timeFunc,
+			NonDeterministicSignaturesViaNotation: packet.BoolPointer(!so.withoutPGPSignatureSalt),
+		})
 		commonOpts = append(commonOpts, optSignGroupFingerprint(so.e.PrimaryKey.Fingerprint))
 	default:
 		return nil, fmt.Errorf("integrity: %w", ErrNoKeyMaterial)

pkg/integrity/sign_test.go

@@ -16,6 +16,7 @@ import (
 	"testing"
 
 	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
 	"github.com/sylabs/sif/v2/pkg/sif"
 )
 
@@ -195,7 +196,7 @@ func TestNewGroupSigner(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			en := newClearsignEncoder(getTestEntity(t), fixedTime)
+			en := newClearsignEncoder(getTestEntity(t), &packet.Config{Time: fixedTime})
 
 			s, err := newGroupSigner(en, tt.fi, tt.groupID, tt.opts...)
 			if got, want := err, tt.wantErr; !errors.Is(got, want) {
@@ -254,12 +255,12 @@ func TestGroupSigner_Sign(t *testing.T) {
 	}
 
 	e := getTestEntity(t)
-	clearsign := newClearsignEncoder(e, fixedTime)
+	clearsign := newClearsignEncoder(e, &packet.Config{Time: fixedTime})
 
 	encrypted := getTestEntity(t)
 	encrypted.PrivateKey.Encrypted = true
 
-	clearsignEncrypted := newClearsignEncoder(encrypted, fixedTime)
+	clearsignEncrypted := newClearsignEncoder(encrypted, &packet.Config{Time: fixedTime})
 
 	tests := []struct {
 		name    string

pkg/siftool/testdata/Test_command_getInfo/Three/out.golden

@@ -3,6 +3,6 @@
   Group ID:   NONE
   Linked ID:  1 (G)
   Offset:     40960
-  Size:       1054
+  Size:       1048
   Hash Type:  SHA-256
   Entity:     12045C8C0B1004D058DE4BEDA20C27EE7FF7BA84

pkg/siftool/testdata/Test_command_getList/OneGroupSignedPGP/out.golden

@@ -3,4 +3,4 @@ ID   |GROUP   |LINK    |SIF POSITION (start-end)  |TYPE
 ------------------------------------------------------------------------------
 1    |1       |NONE    |32768-32772               |FS (Raw/System/386)
 2    |1       |NONE    |36864-40960               |FS (Squashfs/*System/386)
-3    |NONE    |1   (G) |40960-42014               |Signature (SHA-256)
+3    |NONE    |1   (G) |40960-42008               |Signature (SHA-256)

pkg/siftool/testdata/Test_command_getList/TwoGroupsSignedPGP/out.golden

@@ -4,5 +4,5 @@ ID   |GROUP   |LINK    |SIF POSITION (start-end)  |TYPE
 1    |1       |NONE    |32768-32772               |FS (Raw/System/386)
 2    |1       |NONE    |36864-40960               |FS (Squashfs/*System/386)
 3    |2       |NONE    |40960-303104              |FS (Ext3/System/amd64)
-4    |NONE    |1   (G) |303104-304158             |Signature (SHA-256)
-5    |NONE    |2   (G) |304158-305013             |Signature (SHA-256)
+4    |NONE    |1   (G) |303104-304152             |Signature (SHA-256)
+5    |NONE    |2   (G) |304152-305001             |Signature (SHA-256)

test/images/gen_sifs.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2020-2023, Sylabs Inc. All rights reserved.
+// Copyright (c) 2020-2024, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the LICENSE.md file
 // distributed with the sources of this project regarding your rights to use or distribute this
 // software.
@@ -294,6 +294,7 @@ func generateImages() error {
 			opts = append(opts,
 				integrity.OptSignWithTime(func() time.Time { return time.Date(2020, 6, 30, 0, 1, 56, 0, time.UTC) }),
 				integrity.OptSignDeterministic(),
+				integrity.OptSignWithoutPGPSignatureSalt(),
 			)
 
 			s, err := integrity.NewSigner(f, opts...)