caddytls: clientauth: leaf verifier: make trusted leaf certs source pluggable (#6050)

* Made trusted leaf certificates pluggable into the tls.client_auth.leaf
module

* Added leaf loaders modules: file, folder, pem aand storage

* Cleaned implementation of leaf cert loader modules

* Added tests for leaf certs file and folder loaders

* cmd: fix the output of the `Usage` section (#6138)

* core: OnExit hooks (#6128)

* core: OnExit callbacks

* core: Process-global OnExit callbacks

* ci: bump golangci/golangci-lint-action from 3 to 4 (#6141)

Bumps [golangci/golangci-lint-action](https://github.com/golangci/golangci-lint-action) from 3 to 4.
- [Release notes](https://github.com/golangci/golangci-lint-action/releases)
- [Commits](https://github.com/golangci/golangci-lint-action/compare/v3...v4)

---
updated-dependencies:
- dependency-name: golangci/golangci-lint-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* Added more leaf certificate loaders tests and cleaned up code

* Modified leaf cert loaders json field names and cleaned up storage loader comment

* Update modules/caddytls/leaffileloader.go

* Update LeafStorageLoader certificates field name

* Upgraded  protobuf version

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: Mohammed Al Sahaf <[email protected]>
Co-authored-by: Matt Holt <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

2 files changed, 82 insertions, 0 deletions

diff --git a/caddytest/integration/leafcertloaders_test.go b/caddytest/integration/leafcertloaders_test.go
new file mode 100644
index 000000000..592c3f869
--- /dev/null
+++ b/caddytest/integration/leafcertloaders_test.go
@@ -0,0 +1,67 @@
+package integration
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy/v2/caddytest"
+)
+
+func TestLeafCertLoaders(t *testing.T) {
+	tester := caddytest.NewTester(t)
+	tester.InitServer(`
+	{
+		"admin": {
+			"listen": "localhost:2999"
+		},
+		"apps": {
+			"http": {
+				"servers": {
+					"srv0": {
+						"listen": [
+							":443"
+						],
+						"routes": [
+							{
+								"match": [
+									{
+										"host": [
+											"localhost"
+										]
+									}
+								],
+								"terminal": true
+							}
+						],
+						"tls_connection_policies": [
+							{
+								"client_authentication": {
+									"verifiers": [
+										{
+											"verifier": "leaf",
+											"leaf_certs_loaders": [
+												{
+													"loader": "file",
+													"files": ["../leafcert.pem"]
+												}, 
+												{
+													"loader": "folder", 
+													"folders": ["../"]
+												},
+												{
+													"loader": "storage"
+												},
+												{
+													"loader": "pem"
+												}
+											]
+										}
+									]
+								}
+							}
+						]
+					}
+				}
+			}
+		}
+	}`, "json")
+}
diff --git a/caddytest/leafcert.pem b/caddytest/leafcert.pem
new file mode 100644
index 000000000..03febfd3a
--- /dev/null
+++ b/caddytest/leafcert.pem
@@ -0,0 +1,15 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----