feat: Command that generates a private key with well known params.

internal/clis/hmpki/generate_key.go

@@ -0,0 +1,56 @@
+package hmpki
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/pem"
+	"os"
+
+	"git.handmadecities.com/HMC/shhh/pkg/pki"
+	"github.com/spf13/cobra"
+)
+
+func init() {
+	generateCmd.AddCommand(generateKeyCmd)
+}
+
+var generateKeyCmd = &cobra.Command{
+	Use:   "key",
+	Short: "Generate a private key and save it to a file",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+		if err != nil {
+			return err
+		}
+
+		der, err := x509.MarshalPKCS8PrivateKey(priv)
+		if err != nil {
+			return err
+		}
+
+		pemBytes := pem.EncodeToMemory(&pem.Block{
+			Type:  "PRIVATE KEY",
+			Bytes: der,
+		})
+
+		kf, err := os.OpenFile(
+			Output,
+			// Write only, and fail if it alreay exists.
+			os.O_WRONLY|os.O_CREATE|os.O_EXCL,
+			pki.PrivateKeyFilePerms,
+		)
+		if err != nil {
+			return err
+		}
+		if _, err = kf.Write(pemBytes); err != nil {
+			return err
+		}
+		if err = kf.Close(); err != nil {
+			return err
+		}
+
+		return nil
+	},
+}