feat(config): add CA certificate config value

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/metrics.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"crypto/tls"
+	"crypto/x509"
 	"errors"
 	"fmt"
 	"os"
@@ -19,6 +20,7 @@ var (
 	ErrNoMetricsTLSCertificate     = errors.New("config.Metrics.TLS: must define certificate file")
 	ErrNoMetricsTLSKey             = errors.New("config.Metrics.TLS: must define key file")
 	ErrInvalidMetricsTLSKeypair    = errors.New("config.Metrics.TLS: keypair is invalid")
+	ErrInvalidMetricsCACertificate = errors.New("config.Metrics.TLS: invalid CA certificate")
 	ErrCantReadFile                = errors.New("config: can't read required file")
 )
 
@@ -70,6 +72,7 @@ func (m *Metrics) Valid() error {
 type MetricsTLS struct {
 	Certificate string `json:"certificate" yaml:"certificate"`
 	Key         string `json:"key" yaml:"key"`
+	CA          string `json:"ca" yaml:"ca"`
 }
 
 func (mt *MetricsTLS) Valid() error {
@@ -95,6 +98,18 @@ func (mt *MetricsTLS) Valid() error {
 		errs = append(errs, fmt.Errorf("%w: %w", ErrInvalidMetricsTLSKeypair, err))
 	}
 
+	if mt.CA != "" {
+		caCert, err := os.ReadFile(mt.CA)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("%w %s: %w", ErrCantReadFile, mt.CA, err))
+		}
+
+		certPool := x509.NewCertPool()
+		if !certPool.AppendCertsFromPEM(caCert) {
+			errs = append(errs, fmt.Errorf("%w %s", ErrInvalidMetricsCACertificate, mt.CA))
+		}
+	}
+
 	if len(errs) != 0 {
 		return errors.Join(ErrInvalidMetricsTLSConfig, errors.Join(errs...))
 	}

lib/config/metrics_test.go

@@ -119,6 +119,44 @@ func TestMetricsValid(t *testing.T) {
 			},
 			err: ErrInvalidMetricsTLSKeypair,
 		},
+		{
+			name: "mTLS with CA",
+			input: &Metrics{
+				Bind:    ":9090",
+				Network: "tcp",
+				TLS: &MetricsTLS{
+					Certificate: "./testdata/tls/selfsigned.crt",
+					Key:         "./testdata/tls/selfsigned.key",
+					CA:          "./testdata/tls/minica.pem",
+				},
+			},
+		},
+		{
+			name: "mTLS with nonexistent CA",
+			input: &Metrics{
+				Bind:    ":9090",
+				Network: "tcp",
+				TLS: &MetricsTLS{
+					Certificate: "./testdata/tls/selfsigned.crt",
+					Key:         "./testdata/tls/selfsigned.key",
+					CA:          "./testdata/tls/nonexistent.crt",
+				},
+			},
+			err: ErrCantReadFile,
+		},
+		{
+			name: "mTLS with invalid CA",
+			input: &Metrics{
+				Bind:    ":9090",
+				Network: "tcp",
+				TLS: &MetricsTLS{
+					Certificate: "./testdata/tls/selfsigned.crt",
+					Key:         "./testdata/tls/selfsigned.key",
+					CA:          "./testdata/tls/invalid.crt",
+				},
+			},
+			err: ErrInvalidMetricsCACertificate,
+		},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			if err := tt.input.Valid(); !errors.Is(err, tt.err) {

lib/config/testdata/tls/1.1.1.1/cert.pem

@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

lib/config/testdata/tls/1.1.1.1/key.pem

@@ -0,0 +1,6 @@
+-----BEGIN PRIVATE KEY-----
+MIG2AgEAMBAGByqGSM49AgEGBSuBBAAiBIGeMIGbAgEBBDBN8QsHxxHGJpStu8K7
+D/FmaBBNo6c514KGFSIfqGFuREF5aOL3gN/W11yk2OIibdWhZANiAAS7LgNiyhmx
+AbkgOC05tSminO/0ApFDrIqV0ePg+f97FgWYgB+4llIB8KceWGX9qpGZ+qEXWvpL
+NCS00OlYbXkHnZm+5fOmzHgzEfKeC4Nm9/Jf8RK+0tuVH1AyrnV6zgI=
+-----END PRIVATE KEY-----

lib/config/testdata/tls/minica-key.pem

@@ -0,0 +1,6 @@
+-----BEGIN PRIVATE KEY-----
+MIG2AgEAMBAGByqGSM49AgEGBSuBBAAiBIGeMIGbAgEBBDDr9QQo7ZaTgUL6d73G
+2BG7+YRTFJHAZa0FogRglfc+jYttL1J4/xTig3RmHoqSgrehZANiAASDhijM9Xe0
+G9Vam6AJMeKC6aWDNSLwrxNVmPxemsY/yJ1urBgnxRd9GFH6YW1ki/B8rS+Xl1UX
+NnhBrukLaXvgAQQq782/5IUYGsvK5jw8+dSscYVMCQJwGfmQuaNeczQ=
+-----END PRIVATE KEY-----

lib/config/testdata/tls/minica.pem

@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----