app: minor reorg

* add version number
* add more logging
* add command/subcommand

pkg/app/cmd_create.go

@@ -0,0 +1,84 @@
+package app
+
+import (
+	"apc-p15-tool/pkg/pkcs15"
+	"context"
+	"errors"
+	"fmt"
+	"os"
+)
+
+const createDefaultOutFilePath = "apctool.p15"
+
+// cmdCreate is the app's command to create an apc p15 file from key and cert
+// pem files
+func (app *app) cmdCreate(_ context.Context, args []string) error {
+	// extra args == error
+	if len(args) != 0 {
+		app.logger.Errorf("create: failed, extra args (%d) present", len(args))
+		return ErrExtraArgs
+	}
+
+	// key must be specified
+	if app.config.create.keyPemFilePath == nil || *app.config.create.keyPemFilePath == "" {
+		return errors.New("create: failed, key not specified")
+	}
+
+	// cert must be specified
+	if app.config.create.certPemFilePath == nil || *app.config.create.certPemFilePath == "" {
+		return errors.New("create: failed, cert not specified")
+	}
+
+	// validation done
+	app.logger.Infof("create: making apc p15 file from pem files")
+
+	// Read in PEM files
+	keyPem, err := os.ReadFile(*app.config.create.keyPemFilePath)
+	if err != nil {
+		return fmt.Errorf("create: failed to read key file (%s)", err)
+	}
+
+	certPem, err := os.ReadFile(*app.config.create.certPemFilePath)
+	if err != nil {
+		return fmt.Errorf("create: failed to read cert file (%s)", err)
+	}
+
+	// make p15 struct
+	p15, err := pkcs15.ParsePEMToPKCS15(keyPem, certPem)
+	if err != nil {
+		return fmt.Errorf("create: failed to parse pem files (%s)", err)
+	}
+
+	app.logger.Infof("create: successfully loaded pem files")
+
+	// make file bytes
+	p15File, err := p15.ToP15File()
+	if err != nil {
+		return fmt.Errorf("create: failed to make p15 file (%s)", err)
+	}
+
+	// make header for file bytes
+	apcHeader, err := makeFileHeader(p15File)
+	if err != nil {
+		return fmt.Errorf("create: failed to make p15 file header (%s)", err)
+	}
+
+	// combine header with file
+	apcFile := append(apcHeader, p15File...)
+
+	// determine file name (should already be done by flag parsing, but avoid nil just in case)
+	fileName := createDefaultOutFilePath
+	if app.config.create.outFilePath != nil && *app.config.create.outFilePath != "" {
+		fileName = *app.config.create.outFilePath
+	}
+
+	// write file
+	err = os.WriteFile(fileName, apcFile, 0777)
+	if err != nil {
+		return fmt.Errorf("create: failed to write apc p15 file (%s)", err)
+	}
+
+	app.logger.Infof("create: apc p15 file %s written to disk", fileName)
+
+	return nil
+}