Datasource: Add custom headers on alerting queries (#19508)

* Add custom headers on alerting queries

Reference issue #15381

Signed-off-by: Martin Schneppenheim <martin.schneppenheim@rewe-digital.com>

* Fix datasource transport tests

* Migrate decrypting header test to models pkg

* Check correct header

* Add HTTP transport test

Fixes #15381

pkg/models/datasource_cache.go

@@ -4,6 +4,7 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
+	"fmt"
 	"net"
 	"net/http"
 	"sync"
@@ -17,10 +18,25 @@ type proxyTransportCache struct {
 	sync.Mutex
 }
 
+// dataSourceTransport implements http.RoundTripper (https://golang.org/pkg/net/http/#RoundTripper)
+type dataSourceTransport struct {
+	headers   map[string]string
+	transport *http.Transport
+}
+
+// RoundTrip executes a single HTTP transaction, returning a Response for the provided Request.
+func (d *dataSourceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	for key, value := range d.headers {
+		req.Header.Set(key, value)
+	}
+
+	return d.transport.RoundTrip(req)
+}
+
 type cachedTransport struct {
 	updated time.Time
 
-	*http.Transport
+	*dataSourceTransport
 }
 
 var ptc = proxyTransportCache{
@@ -40,12 +56,12 @@ func (ds *DataSource) GetHttpClient() (*http.Client, error) {
 	}, nil
 }
 
-func (ds *DataSource) GetHttpTransport() (*http.Transport, error) {
+func (ds *DataSource) GetHttpTransport() (*dataSourceTransport, error) {
 	ptc.Lock()
 	defer ptc.Unlock()
 
 	if t, present := ptc.cache[ds.Id]; present && ds.Updated.Equal(t.updated) {
-		return t.Transport, nil
+		return t.dataSourceTransport, nil
 	}
 
 	tlsConfig, err := ds.GetTLSConfig()
@@ -55,6 +71,8 @@ func (ds *DataSource) GetHttpTransport() (*http.Transport, error) {
 
 	tlsConfig.Renegotiation = tls.RenegotiateFreelyAsClient
 
+	// Create transport which adds all
+	customHeaders := ds.getCustomHeaders()
 	transport := &http.Transport{
 		TLSClientConfig: tlsConfig,
 		Proxy:           http.ProxyFromEnvironment,
@@ -68,12 +86,17 @@ func (ds *DataSource) GetHttpTransport() (*http.Transport, error) {
 		IdleConnTimeout:       90 * time.Second,
 	}
 
-	ptc.cache[ds.Id] = cachedTransport{
-		Transport: transport,
-		updated:   ds.Updated,
+	dsTransport := &dataSourceTransport{
+		headers:   customHeaders,
+		transport: transport,
 	}
 
-	return transport, nil
+	ptc.cache[ds.Id] = cachedTransport{
+		dataSourceTransport: dsTransport,
+		updated:             ds.Updated,
+	}
+
+	return dsTransport, nil
 }
 
 func (ds *DataSource) GetTLSConfig() (*tls.Config, error) {
@@ -110,3 +133,32 @@ func (ds *DataSource) GetTLSConfig() (*tls.Config, error) {
 
 	return tlsConfig, nil
 }
+
+// getCustomHeaders returns a map with all the to be set headers
+// The map key represents the HeaderName and the value represents this header's value
+func (ds *DataSource) getCustomHeaders() map[string]string {
+	headers := make(map[string]string)
+	if ds.JsonData == nil {
+		return headers
+	}
+
+	decrypted := ds.SecureJsonData.Decrypt()
+	index := 1
+	for {
+		headerNameSuffix := fmt.Sprintf("httpHeaderName%d", index)
+		headerValueSuffix := fmt.Sprintf("httpHeaderValue%d", index)
+
+		key := ds.JsonData.Get(headerNameSuffix).MustString()
+		if key == "" {
+			// No (more) header values are available
+			break
+		}
+
+		if val, ok := decrypted[headerValueSuffix]; ok {
+			headers[key] = val
+		}
+		index++
+	}
+
+	return headers
+}