enhance: support client certificates for mutual TLS (#1273)

Add `runner.client_cert_file` and `runner.client_key_file` for Gitea instances that require mutual TLS. The runner presents the certificate on its RPCs, job summary uploads, and the action, reusable workflow and `builtin:checkout` clones from the instance. The files are read on use, so renewed certificates apply without a restart. Job steps do not get them. An incomplete or mismatched pair fails startup.

Clones now decide the token, client certificate and `runner.insecure` with one host check, which also gives reusable workflow clones the TLS settings they lacked. `runner.insecure` still only covers the registered address.

Fixes: https://gitea.com/gitea/runner/issues/321
Co-authored-by: silverwind <[email protected]>
Co-authored-by: silverwind <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1273
Reviewed-by: silverwind <[email protected]>
Co-authored-by: bircni <[email protected]>

act/runner/job_executor.go

@@ -532,7 +532,7 @@ func tryUploadJobSummary(ctx context.Context, rc *RunContext) {
 		"/jobs/" + strconv.FormatInt(jobID, 10) + "/steps/"
 	actPath := rc.JobContainer.GetActPath()
 	// Reuse a single client across all step uploads so connections can be pooled.
-	client := &http.Client{Timeout: jobSummaryUploadRequestTimeout}
+	client := &http.Client{Timeout: jobSummaryUploadRequestTimeout, Transport: rc.Config.instanceTransportFor(base)}
 	for i := range rc.Run.Job().Steps {
 		summaryPath := path.Join(actPath, "workflow", "step-summary-"+strconv.Itoa(i)+".md")
 		body, ok := readSingleFileFromContainerArchive(ctx, rc.JobContainer, summaryPath, maxJobSummaryBytes)
@@ -544,6 +544,15 @@ func tryUploadJobSummary(ctx context.Context, rc *RunContext) {
 	}
 }
 
+// For Gitea
+// instanceTransportFor returns InstanceTransport only for URLs on the registered address, as steps can rewrite the summary URL through GITHUB_ENV.
+func (c Config) instanceTransportFor(rawURL string) http.RoundTripper {
+	if !strings.HasPrefix(rawURL, c.GitHubInstance+"/") {
+		return nil
+	}
+	return c.InstanceTransport
+}
+
 // extractJobIDFromRuntimeToken returns the JobID claim from an ACTIONS_RUNTIME_TOKEN JWT
 // without verifying its signature. Returns 0 if the token is unparseable or has no JobID.
 func extractJobIDFromRuntimeToken(token string) int64 {