Make Connect function check if signing tools are available

Signed-off-by: Kim Christensen <kimworking@gmail.com>

pkg/signing/plugin_adapter.go

@@ -34,3 +34,7 @@ func (a PluginAdapter) Sign(ctx context.Context, ref string) error {
 func (a PluginAdapter) Verify(ctx context.Context, ref string) error {
 	return a.plugin.Verify(ctx, ref)
 }
+
+func (a PluginAdapter) Connect(ctx context.Context) error {
+	return a.plugin.Connect(ctx)
+}

pkg/signing/plugins/cosign/cosign.go

@@ -2,6 +2,7 @@ package cosign
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -35,13 +36,14 @@ func NewSigner(c *portercontext.Context, cfg PluginConfig) *Cosign {
 	return s
 }
 
-// TODO: we should get the certificate... here?
 func (s *Cosign) Connect(ctx context.Context) error {
 	//lint:ignore SA4006 ignore unused ctx for now
 	ctx, log := tracing.StartSpan(ctx)
 	defer log.EndSpan()
 
-	log.Debug("Running cosign signer")
+	if err := exec.Command("cosign", "version").Run(); err != nil {
+		return errors.New("cosign was not found")
+	}
 
 	return nil
 }

pkg/signing/plugins/notation/notation.go

@@ -2,6 +2,7 @@ package notation
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os/exec"
 
@@ -33,7 +34,9 @@ func (s *Signer) Connect(ctx context.Context) error {
 	ctx, log := tracing.StartSpan(ctx)
 	defer log.EndSpan()
 
-	log.Debug("Running notation signer")
+	if err := exec.Command("notation", "version").Run(); err != nil {
+		return errors.New("notation was not found")
+	}
 
 	return nil
 }

pkg/signing/plugins/proto/signing_protocol.proto

@@ -11,11 +11,16 @@ message VerifyRequest {
   string Ref = 1;
 }
 
+message ConnectRequest {}
+
 message SignResponse {}
 
 message VerifyResponse {}
 
+message ConnectResponse {}
+
 service SigningProtocol {
   rpc Sign(SignRequest) returns (SignResponse);
   rpc Verify(VerifyRequest) returns (VerifyResponse);
+  rpc Connect(ConnectRequest) returns (ConnectResponse);
 }