Node collector can not exclude nodes by the same label key

[lukehollinda]

What steps did you take and what happened:
I've deployed the Trivy operator through helm with the following nodeCollector exclusion defined.

nodeCollector:
  excludeNodes: "role=master,role=etcd,role=additional-control-plane-component"

Currently, the nodes within my cluster are differentiated by the value of the role label.
The node collector exclusion code naively populates a map[string]string with label key and values. This causes any label with a repeated key to overwrite the previous value.

trivy-operator/pkg/trivyoperator/config.go

Lines 360 to 376 in 7961baa

	func (c ConfigData) GetNodeCollectorExcludeNodes() (map[string]string, error) {
	nodeCollectorExcludeNodesStr, found := c[KeyNodeCollectorExcludeNodes]
	if !found || strings.TrimSpace(nodeCollectorExcludeNodesStr) == "" {
	return make(map[string]string), nil
	}
	nodeCollectorExcludeNodesMap := make(map[string]string)
	for _, excludeNode := range strings.Split(nodeCollectorExcludeNodesStr, ",") {
	sepByEqual := strings.Split(excludeNode, "=")
	if len(sepByEqual) != 2 {
	return make(map[string]string), fmt.Errorf("failed parsing incorrectly formatted exclude nodes values: %s", nodeCollectorExcludeNodesStr)
	}
	key, value := sepByEqual[0], sepByEqual[1]
	nodeCollectorExcludeNodesMap[key] = value
	}
	return nodeCollectorExcludeNodesMap, nil
	}

This ultimately results in node-collector pods being created with a NodeSelector which attempts to schedule the pod to tainted control plane nodes.

What did you expect to happen:
I'd expect to be able to exclude nodes based on multiple values of the same label. I would prefer to avoid adding a unique label key per node pool.

Anything else you would like to add:

[Miscellaneous information that will assist in solving the issue.]

Environment:

• Trivy-Operator version (use trivy-operator version):
  - Chart version: 0.25.0
  - Trivy version: 0.23.0
• Kubernetes version (use kubectl version):
  - N/A
• OS (macOS 10.15, Windows 10, Ubuntu 19.10 etc):
  - N/A

[simar7]

cc @afdesk