lib/netutil: validate TLS cert and key files immediately (#6621)

Validate files specified via `-tlsKeyFile` and `-tlsCertFile` cmd-line flags on the process start-up. Previously, validation happened on the first connection accepted by HTTP server.

https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6608

---------

Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit e5d279bb71)

docs/CHANGELOG.md

@@ -36,6 +36,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * FEATURE: [vmauth](./vmauth.md): add `keep_original_host` option, which can be used for proxying the original `Host` header from client request to the backend. By default the backend host is used as `Host` header when proxying requests to the configured backends. See [these docs](./vmauth.md#host-http-header).
 * FEATURE: [vmauth](./vmauth.md) now returns HTTP 502 status code when all upstream backends are not available. Previously, it returned HTTP 503 status code. This change aligns vmauth behavior with other well-known reverse-proxies behavior.
 
+* BUGFIX: all VictoriaMetrics components: validate files specified via `-tlsKeyFile` and `-tlsCertFile` cmd-line flags on the process start-up. Previously, validation happened on the first connection accepted by HTTP server. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6608) for the details. Thanks to @yincongcyincong for the [pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6621).
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth/): properly proxy requests to backend urls ending with `/` if the original request path equals to `/`. Previously the trailing `/` at the backend path was incorrectly removed. For example, if the request to `http://vmauth/` is configured to be proxied to `url_prefix=http://backend/foo/`, then it was proxied to `http://backend/foo`, while it should go to `http://backend/foo/`.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth/): fix `cannot read data after closing the reader` error when proxying HTTP requests without body (aka `GET` requests). The issue has been introduced in [v1.102.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.102.0) in [this commit](https://github.com/VictoriaMetrics/VictoriaMetrics/commit/7ee57974935a662896f2de40fdf613156630617d).
 

lib/netutil/tls.go

@@ -12,6 +12,11 @@ import (
 
 // GetServerTLSConfig returns TLS config for the server.
 func GetServerTLSConfig(tlsCertFile, tlsKeyFile, tlsMinVersion string, tlsCipherSuites []string) (*tls.Config, error) {
+	_, err := tls.LoadX509KeyPair(tlsCertFile, tlsKeyFile)
+	if err != nil {
+		return nil, fmt.Errorf("cannot load TLS certificate and key files: %w", err)
+	}
+
 	minVersion, err := ParseTLSVersion(tlsMinVersion)
 	if err != nil {
 		return nil, fmt.Errorf("cannnot use TLS min version from tlsMinVersion=%q. Supported TLS versions (TLS10, TLS11, TLS12, TLS13): %w", tlsMinVersion, err)

lib/netutil/tls_test.go

@@ -2,6 +2,9 @@ package netutil
 
 import (
 	"crypto/tls"
+	"errors"
+	"fmt"
+	"os"
 	"reflect"
 	"testing"
 )
@@ -106,3 +109,85 @@ func TestParseTLSVersionFailure(t *testing.T) {
 	// incorrect tls version in tlsName
 	f("TLS14")
 }
+
+func TestGetServerTLSConfig(t *testing.T) {
+	f := func(tlsCertFile, tlsKeyFile string, expectErr bool) {
+		t.Helper()
+		_, err := GetServerTLSConfig(tlsCertFile, tlsKeyFile, "", []string{})
+		if !errors.Is(err, nil) != expectErr { // same as: if errors.Is(err, nil) == expectErr {
+			t.Fatalf("expect err: %v, get error: %v", expectErr, err)
+		}
+	}
+
+	mustCreateFile("test.crt", testCRT)
+	mustCreateFile("test.key", testPK)
+	defer func() {
+		_ = os.Remove("test.crt")
+		_ = os.Remove("test.key")
+	}()
+
+	// check cert file not exist
+	f("/a", "./test.key", true)
+	// check key file not exist
+	f("./test.crt", "/b", true)
+	// cert file and key file all exist
+	f("./test.crt", "./test.key", false)
+}
+
+const (
+	testCRT = `-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+	testPK = `-----BEGIN PRIVATE KEY-----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+-----END PRIVATE KEY-----`
+)
+
+func mustCreateFile(path, contents string) {
+	if err := os.WriteFile(path, []byte(contents), 0600); err != nil {
+		panic(fmt.Errorf("cannot create file %q with %d bytes contents: %w", path, len(contents), err))
+	}
+}