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feat(ISV-6377): let cosign use HashedRekord for TLOG verification of attestations #4490

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feat(ISV-6377): let cosign use HashedRekord for TLOG verification of attestations #4490

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78 changes: 70 additions & 8 deletions pkg/cosign/tlog.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import (
"crypto/x509"
"encoding/base64"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"hash"
Expand All @@ -31,15 +32,16 @@ import (
"strings"

"github.com/go-openapi/strfmt"
"github.com/go-openapi/swag"
"github.com/go-openapi/swag/conv"
"github.com/secure-systems-lab/go-securesystemslib/dsse"
"github.com/sigstore/cosign/v3/internal/ui"
"github.com/sigstore/cosign/v3/pkg/cosign/bundle"
"github.com/sigstore/cosign/v3/pkg/cosign/env"
"github.com/sigstore/rekor/pkg/generated/client"
"github.com/sigstore/rekor/pkg/generated/client/entries"
"github.com/sigstore/rekor/pkg/generated/models"
"github.com/sigstore/rekor/pkg/types"
"github.com/sigstore/rekor/pkg/types/dsse"
rekordsse "github.com/sigstore/rekor/pkg/types/dsse"
dsse_v001 "github.com/sigstore/rekor/pkg/types/dsse/v0.0.1"
hashedrekord_v001 "github.com/sigstore/rekor/pkg/types/hashedrekord/v0.0.1"
"github.com/sigstore/rekor/pkg/types/intoto"
Expand Down Expand Up @@ -124,7 +126,7 @@ func dsseEntry(ctx context.Context, signature, pubKey []byte) (models.ProposedEn

pubKeyBytes = append(pubKeyBytes, pubKey)

return types.NewProposedEntry(ctx, dsse.KIND, dsse_v001.APIVERSION, types.ArtifactProperties{
return types.NewProposedEntry(ctx, rekordsse.KIND, dsse_v001.APIVERSION, types.ArtifactProperties{
ArtifactBytes: signature,
PublicKeyBytes: pubKeyBytes,
})
Expand Down Expand Up @@ -211,7 +213,7 @@ func TLogUpload(ctx context.Context, rekorClient *client.Rekor, signature []byte
func TLogUploadWithCustomHash(ctx context.Context, rekorClient *client.Rekor, signature []byte, checksum NamedHash, pemBytes []byte) (*models.LogEntryAnon, error) {
re := rekorEntry(checksum, signature, pemBytes)
returnVal := models.Hashedrekord{
APIVersion: swag.String(re.APIVersion()),
APIVersion: conv.Pointer(re.APIVersion()),
Spec: re.HashedRekordObj,
}
return doUpload(ctx, rekorClient, &returnVal)
Expand Down Expand Up @@ -286,8 +288,8 @@ func rekorEntry(checksum NamedHash, signature, pubKey []byte) hashedrekord_v001.
HashedRekordObj: models.HashedrekordV001Schema{
Data: &models.HashedrekordV001SchemaData{
Hash: &models.HashedrekordV001SchemaDataHash{
Algorithm: swag.String(rekorEntryHashAlgorithm(checksum)),
Value: swag.String(hex.EncodeToString(checksum.Sum(nil))),
Algorithm: conv.Pointer(rekorEntryHashAlgorithm(checksum)),
Value: conv.Pointer(hex.EncodeToString(checksum.Sum(nil))),
},
},
Signature: &models.HashedrekordV001SchemaSignature{
Expand Down Expand Up @@ -430,6 +432,8 @@ func proposedEntries(b64Sig string, payload, pubKey []byte) ([]models.ProposedEn
// The fact that there's no signature (or empty rather), implies
// that this is an Attestation that we're verifying.
if len(signature) == 0 {
// For attestations, check DSSE, in-toto, and HashedRekord entries
// This allows verification of attestations uploaded as HashedRekord entries
intotoEntry, err := intotoEntry(context.Background(), payload, pubKey)
if err != nil {
return nil, err
Expand All @@ -438,22 +442,80 @@ func proposedEntries(b64Sig string, payload, pubKey []byte) ([]models.ProposedEn
if err != nil {
return nil, err
}
proposedEntry = []models.ProposedEntry{dsseEntry, intotoEntry}

hashedRekordEntry, err := createHashedRekordEntryForAttestation(payload, pubKey)
if err != nil {
// If we can't create HashedRekord entry (e.g., not a valid DSSE envelope),
// continue with just DSSE and in-toto entries
proposedEntry = []models.ProposedEntry{dsseEntry, intotoEntry}
} else {
// Include all three entry types
proposedEntry = []models.ProposedEntry{dsseEntry, intotoEntry, hashedRekordEntry}
}
} else {
sha256CheckSum := NewCryptoNamedHash(crypto.SHA256)
if _, err := sha256CheckSum.Write(payload); err != nil {
return nil, err
}
re := rekorEntry(sha256CheckSum, signature, pubKey)
entry := &models.Hashedrekord{
APIVersion: swag.String(re.APIVersion()),
APIVersion: conv.Pointer(re.APIVersion()),
Spec: re.HashedRekordObj,
}
proposedEntry = []models.ProposedEntry{entry}
}
return proposedEntry, nil
}

// createHashedRekordEntryForAttestation creates a HashedRekord entry for DSSE attestations
// This allows verification of attestations that were uploaded as HashedRekord entries
//
// This function:
// - Parses the DSSE envelope from the payload
// - Extracts the signature bytes from the DSSE envelope
// - Creates a PAE-encoded payload (as per DSSE specification)
// - Creates a HashedRekord entry with the signature and PAE-encoded payload hash
func createHashedRekordEntryForAttestation(payload, pubKey []byte) (models.ProposedEntry, error) {
// Parse the payload as a DSSE envelope using the existing struct
var dsseEnvelope dsse.Envelope

if err := json.Unmarshal(payload, &dsseEnvelope); err != nil {
return nil, fmt.Errorf("payload is not a valid DSSE envelope: %w", err)
}

if len(dsseEnvelope.Signatures) == 0 {
return nil, fmt.Errorf("DSSE envelope has no signatures")
}

// Extract the signature bytes
signatureBytes, err := base64.StdEncoding.DecodeString(dsseEnvelope.Signatures[0].Sig)
if err != nil {
return nil, fmt.Errorf("invalid base64 signature in DSSE envelope: %w", err)
}

// Extract the payload and create PAE-encoded payload
payloadBytes, err := base64.StdEncoding.DecodeString(dsseEnvelope.Payload)
if err != nil {
return nil, fmt.Errorf("invalid base64 payload in DSSE envelope: %w", err)
}

// Create PAE-encoded payload using the existing DSSE library function
payloadType := "application/vnd.in-toto+json"
paePayload := dsse.PAE(payloadType, payloadBytes)

// Create HashedRekord entry
sha256CheckSum := NewCryptoNamedHash(crypto.SHA256)
sha256CheckSum.Write([]byte(paePayload))

re := rekorEntry(sha256CheckSum, signatureBytes, pubKey)
entry := &models.Hashedrekord{
APIVersion: conv.Pointer(re.APIVersion()),
Spec: re.HashedRekordObj,
}

return entry, nil
}

func FindTlogEntry(ctx context.Context, rekorClient *client.Rekor,
b64Sig string, payload, pubKey []byte) ([]models.LogEntryAnon, error) {
searchParams := entries.NewSearchLogQueryParamsWithContext(ctx)
Expand Down
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