Add sanity check to prevent data loss in the event the user mistypes their passphrase during encryption

wrappers/sanityCheck.go

@@ -0,0 +1,28 @@
+package wrappers
+
+import (
+	"errors"
+	"os"
+)
+
+// GenSanityCheck creates an encrypted file containing known plaintext
+// to later be used for ensuring the user does not encrypt data with
+// an incorrect passphrase.
+func GenSanityCheck(path string, passphrase []byte) {
+	os.WriteFile(path, Encrypt([]byte("thx4usin'rcw"), passphrase), 0600)
+}
+
+// RunSanityCheck should be run before any encryption operation
+// to ensure the user does not encrypt data with an incorrect passphrase.
+// Failure to perform this check could result in data loss.
+func RunSanityCheck(path string, passphrase []byte) error {
+	encBytes, err := os.ReadFile(path)
+	if err != nil {
+		return errors.New("Failed to read sanity check file (" + path + ")")
+	}
+	decBytes, err := Decrypt(encBytes, passphrase)
+	if string(decBytes) == "thx4usin'rcw" {
+		return nil
+	}
+	return errors.New("Sanity check failed (likely due to inconsistent passphrase)")
+}