configfile: Initialize nil AuthConfigs

Initialize AuthConfigs map if it's nil before returning it.
This fixes fileStore.Store nil dereference panic when adding a new key
to the map.

Signed-off-by: Danial Gharib <danial.mail.gh@gmail.com>
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
(cherry picked from commit ad43df5)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli/config/configfile/file.go

@@ -94,6 +94,9 @@ func (configFile *ConfigFile) ContainsAuth() bool {
 
 // GetAuthConfigs returns the mapping of repo to auth configuration
 func (configFile *ConfigFile) GetAuthConfigs() map[string]types.AuthConfig {
+	if configFile.AuthConfigs == nil {
+		configFile.AuthConfigs = make(map[string]types.AuthConfig)
+	}
 	return configFile.AuthConfigs
 }
 

cli/config/credentials/file_store.go

@@ -52,7 +52,8 @@ func (c *fileStore) GetAll() (map[string]types.AuthConfig, error) {
 
 // Store saves the given credentials in the file store.
 func (c *fileStore) Store(authConfig types.AuthConfig) error {
-	c.file.GetAuthConfigs()[authConfig.ServerAddress] = authConfig
+	authConfigs := c.file.GetAuthConfigs()
+	authConfigs[authConfig.ServerAddress] = authConfig
 	return c.file.Save()
 }