x-pack/filebeat/input/{cel,salesforce}: check response for nilness be…

…fore logging (elastic#40144)

It turns out that retryablehttp will pass a nil *http.Response to the
client's ErrorHandler function although this is not documented. In the
cases where we are using this, this will result in a nil deference
panic when the retries exceed their maximum. So, check for nilness to
avoid this.

CHANGELOG.next.asciidoc

@@ -149,6 +149,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Upgrade github.com/hashicorp/go-retryablehttp to mitigate CVE-2024-6104 {pull}40036[40036]
 - Fix for Google Workspace duplicate events issue by adding canonical sorting over fingerprint keys array to maintain key order. {pull}40055[40055] {issue}39859[39859]
 - Fix handling of deeply nested numeric values in HTTP Endpoint CEL programs. {pull}40115[40115]
+- Prevent panic in CEL and salesforce inputs when github.com/hashicorp/go-retryablehttp exceeds maximum retries. {pull}40144[40144]
 
 *Heartbeat*
 

x-pack/filebeat/input/cel/input.go

@@ -913,10 +913,19 @@ func checkRedirect(cfg *ResourceConfig, log *logp.Logger) func(*http.Request, []
 // retryErrorHandler returns a retryablehttp.ErrorHandler that will log retry resignation
 // but return the last retry attempt's response and a nil error so that the CEL code
 // can evaluate the response status itself. Any error passed to the retryablehttp.ErrorHandler
-// is returned unaltered.
+// is returned unaltered. Despite not being documented so, the error handler may be passed
+// a nil resp. retryErrorHandler will handle this case.
 func retryErrorHandler(max int, log *logp.Logger) retryablehttp.ErrorHandler {
 	return func(resp *http.Response, err error, numTries int) (*http.Response, error) {
-		log.Warnw("giving up retries", "method", resp.Request.Method, "url", resp.Request.URL, "retries", max+1)
+		if resp != nil && resp.Request != nil {
+			reqURL := "unavailable"
+			if resp.Request.URL != nil {
+				reqURL = resp.Request.URL.String()
+			}
+			log.Warnw("giving up retries", "method", resp.Request.Method, "url", reqURL, "retries", max+1)
+		} else {
+			log.Warnw("giving up retries: no response available", "retries", max+1)
+		}
 		return resp, err
 	}
 }

x-pack/filebeat/input/salesforce/input.go

@@ -470,10 +470,19 @@ func (l *retryLog) Warn(msg string, kv ...interface{})  { l.log.Warnw(msg, kv...
 // retryErrorHandler returns a retryablehttp.ErrorHandler that will log retry resignation
 // but return the last retry attempt's response and a nil error to allow the retryablehttp.Client
 // evaluate the response status itself. Any error passed to the retryablehttp.ErrorHandler
-// is returned unaltered.
+// is returned unaltered. Despite not being documented so, the error handler may be passed
+// a nil resp. retryErrorHandler will handle this case.
 func retryErrorHandler(max int, log *logp.Logger) retryablehttp.ErrorHandler {
 	return func(resp *http.Response, err error, numTries int) (*http.Response, error) {
-		log.Warnw("giving up retries", "method", resp.Request.Method, "url", resp.Request.URL, "retries", max+1)
+		if resp != nil && resp.Request != nil {
+			reqURL := "unavailable"
+			if resp.Request.URL != nil {
+				reqURL = resp.Request.URL.String()
+			}
+			log.Warnw("giving up retries", "method", resp.Request.Method, "url", reqURL, "retries", max+1)
+		} else {
+			log.Warnw("giving up retries: no response available", "retries", max+1)
+		}
 		return resp, err
 	}
 }