osbuild-composer: use less pointers in config

The default values of fields in both ComposerConfig.Koji and
ComposerConfig.Worker are well-suited for how they're used.

The nil-checks in main.go only checked that the sections exist. This is
quite a weak check for validity, because the sections could be empty. If
anything is required for composer to function, we could add proper
validation in the future.

Do the same for the CA fields, which contain file names. Go has lots of
precedent for using empty strings to denote "no value" in the standard
library. Use it for CA files, too, instead of pointers.

cmd/osbuild-composer/config.go

@@ -7,7 +7,7 @@ import (
 )
 
 type ComposerConfigFile struct {
-	Koji *struct {
+	Koji struct {
 		Servers map[string]struct {
 			Kerberos *struct {
 				Principal string `toml:"principal"`
@@ -15,12 +15,12 @@ type ComposerConfigFile struct {
 			} `toml:"kerberos,omitempty"`
 		} `toml:"servers"`
 		AllowedDomains []string `toml:"allowed_domains"`
-		CA             *string  `toml:"ca"`
+		CA             string   `toml:"ca"`
 	} `toml:"koji"`
-	Worker *struct {
+	Worker struct {
 		AllowedDomains []string `toml:"allowed_domains"`
-		CA             *string  `toml:"ca"`
-	} `toml:"worker,omitempty"`
+		CA             string   `toml:"ca"`
+	} `toml:"worker"`
 }
 
 func LoadConfig(name string) (*ComposerConfigFile, error) {

cmd/osbuild-composer/config_test.go

@@ -10,8 +10,12 @@ import (
 func TestEmpty(t *testing.T) {
 	config, err := LoadConfig("testdata/empty-config.toml")
 	require.NoError(t, err)
-	require.Nil(t, config.Koji)
-	require.Nil(t, config.Worker)
+	require.NotNil(t, config)
+	require.Empty(t, config.Koji.Servers)
+	require.Empty(t, config.Koji.AllowedDomains)
+	require.Empty(t, config.Koji.CA)
+	require.Empty(t, config.Worker.AllowedDomains)
+	require.Empty(t, config.Worker.CA)
 }
 
 func TestNonExisting(t *testing.T) {
@@ -20,3 +24,21 @@ func TestNonExisting(t *testing.T) {
 	require.True(t, os.IsNotExist(err))
 	require.Nil(t, config)
 }
+
+func TestConfig(t *testing.T) {
+	config, err := LoadConfig("testdata/test.toml")
+	require.NoError(t, err)
+	require.NotNil(t, config)
+
+	server, ok := config.Koji.Servers["example.com"]
+	require.True(t, ok)
+	require.NotNil(t, server.Kerberos)
+	require.Equal(t, server.Kerberos.Principal, "example@osbuild.org")
+	require.Equal(t, server.Kerberos.KeyTab, "/etc/osbuild-composer/osbuild.keytab")
+
+	require.Equal(t, config.Koji.AllowedDomains, []string{"osbuild.org"})
+	require.Equal(t, config.Koji.CA, "/etc/osbuild-composer/ca-crt.pem")
+
+	require.Equal(t, config.Worker.AllowedDomains, []string{"osbuild.org"})
+	require.Equal(t, config.Worker.CA, "/etc/osbuild-composer/ca-crt.pem")
+}

cmd/osbuild-composer/main.go

@@ -30,9 +30,10 @@ import (
 const configFile = "/etc/osbuild-composer/osbuild-composer.toml"
 
 type connectionConfig struct {
-	// CA used for client certificate validation. If nil, then the CAs
+	// CA used for client certificate validation. If empty, then the CAs
 	// trusted by the host system are used.
-	CACertFile     *string
+	CACertFile string
+
 	ServerKeyFile  string
 	ServerCertFile string
 	AllowedDomains []string
@@ -41,8 +42,8 @@ type connectionConfig struct {
 func createTLSConfig(c *connectionConfig) (*tls.Config, error) {
 	var roots *x509.CertPool
 
-	if c.CACertFile != nil {
-		caCertPEM, err := ioutil.ReadFile(*c.CACertFile)
+	if c.CACertFile != "" {
+		caCertPEM, err := ioutil.ReadFile(c.CACertFile)
 		if err != nil {
 			return nil, err
 		}
@@ -200,9 +201,6 @@ func main() {
 
 	// Optionally run Koji API
 	if kojiListeners, exists := listeners["osbuild-composer-koji.socket"]; exists {
-		if config.Koji == nil {
-			log.Fatal("koji not configured in the config file")
-		}
 		kojiServers := make(map[string]koji.GSSAPICredentials)
 		for server, creds := range config.Koji.Servers {
 			if creds.Kerberos == nil {
@@ -248,10 +246,6 @@ func main() {
 
 		log.Printf("Starting remote listener\n")
 
-		if config.Worker == nil {
-			log.Fatal("remote worker not configured in the config file")
-		}
-
 		tlsConfig, err := createTLSConfig(&connectionConfig{
 			CACertFile:     config.Worker.CA,
 			ServerKeyFile:  "/etc/osbuild-composer/composer-key.pem",

cmd/osbuild-composer/testdata/test.toml

@@ -0,0 +1,11 @@
+[koji]
+allowed_domains = [ "osbuild.org" ]
+ca = "/etc/osbuild-composer/ca-crt.pem"
+
+[koji.servers."example.com".kerberos]
+principal = "example@osbuild.org"
+keytab = "/etc/osbuild-composer/osbuild.keytab"
+
+[worker]
+allowed_domains = [ "osbuild.org" ]
+ca = "/etc/osbuild-composer/ca-crt.pem"