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Use issued certificate in request to Rekor #799

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merged 2 commits into from
Oct 24, 2023
Merged

Use issued certificate in request to Rekor #799

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5f51823
Use issued certificate in request to Rekor
haydentherapper Oct 24, 2023
312a18e
Merge branch 'sigstore:main' into static-key
haydentherapper Oct 24, 2023
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13 changes: 11 additions & 2 deletions cmd/prober/prober.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@ package main
import (
"bytes"
"context"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"encoding/json"
"flag"
"log"
Expand Down Expand Up @@ -194,11 +197,17 @@ func runProbers(ctx context.Context, freq int, runOnce bool) {
}
}
if runWriteProber {
if err := fulcioWriteEndpoint(ctx); err != nil {
priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
Logger.Fatalf("failed to generate key: %v", err)
}

cert, err := fulcioWriteEndpoint(ctx, priv)
if err != nil {
hasErr = true
Logger.Errorf("error running fulcio write prober: %v", err)
}
if err := rekorWriteEndpoint(ctx); err != nil {
if err := rekorWriteEndpoint(ctx, cert, priv); err != nil {
hasErr = true
Logger.Errorf("error running rekor write prober: %v", err)
}
Expand Down
100 changes: 71 additions & 29 deletions cmd/prober/write.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,11 @@ import (
"crypto/ecdsa"
"crypto/rand"
"crypto/sha256"
"crypto/x509"
"encoding/hex"
"encoding/json"
"fmt"
"io"
"net/http"
"time"

Expand Down Expand Up @@ -65,17 +67,17 @@ func setHeaders(req *retryablehttp.Request, token string) {

// fulcioWriteEndpoint tests the only write endpoint for Fulcio
// which is "/api/v2/signingCert", which requests a cert from Fulcio
func fulcioWriteEndpoint(ctx context.Context) error {
func fulcioWriteEndpoint(ctx context.Context, priv *ecdsa.PrivateKey) (*x509.Certificate, error) {
if !all.Enabled(ctx) {
return fmt.Errorf("no auth provider for fulcio is enabled")
return nil, fmt.Errorf("no auth provider for fulcio is enabled")
}
tok, err := providers.Provide(ctx, "sigstore")
if err != nil {
return fmt.Errorf("getting provider: %w", err)
return nil, fmt.Errorf("getting provider: %w", err)
}
b, err := certificateRequest(ctx, tok)
b, err := certificateRequest(ctx, tok, priv)
if err != nil {
return fmt.Errorf("certificate response: %w", err)
return nil, fmt.Errorf("certificate response: %w", err)
}

// Construct the API endpoint for this handler
Expand All @@ -84,7 +86,7 @@ func fulcioWriteEndpoint(ctx context.Context) error {

req, err := retryablehttp.NewRequest(http.MethodPost, hostPath, bytes.NewBuffer(b))
if err != nil {
return fmt.Errorf("new request: %w", err)
return nil, fmt.Errorf("new request: %w", err)
}

setHeaders(req, tok)
Expand All @@ -94,22 +96,50 @@ func fulcioWriteEndpoint(ctx context.Context) error {
latency := time.Since(t).Milliseconds()
if err != nil {
Logger.Errorf("error requesting cert: %v", err)
return err
return nil, err
}
defer resp.Body.Close()

responseBody, err := io.ReadAll(resp.Body)
if err != nil {
Logger.Errorf("error reading response from Fulcio: %v", err)
return nil, err
}
var fulcioResp SigningCertificateResponse
if err := json.Unmarshal(responseBody, &fulcioResp); err != nil {
Logger.Errorf("error parsing response from Fulcio: %v", err)
return nil, err
}
if len(fulcioResp.CertificatesWithSct.CertificateChain.Certificates) != 3 {
Logger.Errorf("unexpected number of certificates, got %d, expected 3",
len(fulcioResp.CertificatesWithSct.CertificateChain.Certificates))
return nil, err
}

cert, err := cryptoutils.UnmarshalCertificatesFromPEM([]byte(fulcioResp.CertificatesWithSct.CertificateChain.Certificates[0]))
if err != nil {
Logger.Errorf("error unmarshalling leaf certificate from Fulcio: %v", err)
return nil, err
}
if len(cert) != 1 {
Logger.Errorf("unexpected number of certificates after unmarshalling got %d, expected 1", len(cert))
return nil, err
}

// Export data to prometheus
exportDataToPrometheus(resp, fulcioURL, endpoint, POST, latency)
return nil
return cert[0], nil
}

// rekorWriteEndpoint tests the write endpoint for rekor, which is
// /api/v1/log/entries and adds an entry to the log
func rekorWriteEndpoint(ctx context.Context) error {
// if a certificate is provided, the Rekor entry will contain that certificate,
// otherwise the provided key is used
func rekorWriteEndpoint(ctx context.Context, cert *x509.Certificate, priv *ecdsa.PrivateKey) error {
endpoint := rekorEndpoint
hostPath := rekorURL + endpoint

body, err := rekorEntryRequest()
body, err := rekorEntryRequest(cert, priv)
if err != nil {
return fmt.Errorf("rekor entry: %w", err)
}
Expand Down Expand Up @@ -152,29 +182,33 @@ func rekorWriteEndpoint(ctx context.Context) error {
return err
}

func rekorEntryRequest() ([]byte, error) {
func rekorEntryRequest(cert *x509.Certificate, priv *ecdsa.PrivateKey) ([]byte, error) {
// sign payload
payload := []byte(time.Now().String())
priv, err := cosign.GeneratePrivateKey()
if err != nil {
return nil, fmt.Errorf("generating keys: %w", err)
}
signer, err := signature.LoadECDSASignerVerifier(priv, crypto.SHA256)
if err != nil {
return nil, fmt.Errorf("loading signer verifier: %w", err)
}
pub, err := signer.PublicKey()
if err != nil {
return nil, fmt.Errorf("public key: %w", err)
}
pubKey, err := cryptoutils.MarshalPublicKeyToPEM(pub)
if err != nil {
return nil, fmt.Errorf("marshal public key: %w", err)
}
sig, err := signer.SignMessage(bytes.NewReader(payload))
if err != nil {
return nil, fmt.Errorf("sign message: %w", err)
}

var verifier []byte
if cert != nil {
certPEM, err := cryptoutils.MarshalCertificateToPEM(cert)
if err != nil {
return nil, fmt.Errorf("error marshalling certificate: %w", err)
}
verifier = certPEM
} else {
pubKeyPEM, err := cryptoutils.MarshalPublicKeyToPEM(priv.Public())
if err != nil {
return nil, fmt.Errorf("error marshalling public key: %w", err)
}
verifier = pubKeyPEM
}

h := sha256.Sum256(payload)
e := &hashedrekord.V001Entry{
HashedRekordObj: models.HashedrekordV001Schema{
Expand All @@ -187,7 +221,7 @@ func rekorEntryRequest() ([]byte, error) {
Signature: &models.HashedrekordV001SchemaSignature{
Content: strfmt.Base64(sig),
PublicKey: &models.HashedrekordV001SchemaSignaturePublicKey{
Content: strfmt.Base64(pubKey),
Content: strfmt.Base64(verifier),
},
},
},
Expand All @@ -199,11 +233,7 @@ func rekorEntryRequest() ([]byte, error) {
return json.Marshal(pe)
}

func certificateRequest(_ context.Context, idToken string) ([]byte, error) {
priv, err := cosign.GeneratePrivateKey()
if err != nil {
return nil, fmt.Errorf("generating cert: %w", err)
}
func certificateRequest(_ context.Context, idToken string, priv *ecdsa.PrivateKey) ([]byte, error) {
pubBytesPEM, err := cryptoutils.MarshalPublicKeyToPEM(priv.Public())
if err != nil {
return nil, err
Expand Down Expand Up @@ -237,6 +267,18 @@ type SigningCertificateRequest struct {
PublicKeyRequest PublicKeyRequest `json:"publicKeyRequest"`
}

type SigningCertificateResponse struct {
CertificatesWithSct SignedCertificateEmbeddedSct `json:"signedCertificateEmbeddedSct"`
}

type SignedCertificateEmbeddedSct struct {
CertificateChain CertificateChain `json:"chain"`
}

type CertificateChain struct {
Certificates []string `json:"certificates"`
}

type PublicKeyRequest struct {
PublicKey PublicKey `json:"publicKey"`
ProofOfPossession []byte `json:"proofOfPossession"`
Expand Down
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