Module keybackup 

Vault recovery backup & restore (KOV-34, spec §10.2).

A mode-aware, encrypted disaster-recovery backup of what a vault needs to unlock, sealed into a standard, ASCII-armored age blob under a recovery passphrase (age-scrypt). The plaintext never lands in a file or a log (I7/I12) — only the encrypted blob is emitted; and because the blob is a normal age file it stays recoverable with any age implementation (age -d) even if kovra is unavailable.

The blob is self-describing (BackupKind): import restores it to the right backend regardless of the machine’s current mode, and respects the vault’s mode — it never silently migrates one mode to another:

• keyring vaults store the 32-byte master key → backup carries the key, restored into the OS keyring.
• passphrase vaults derive the key (Argon2(passphrase, salt)), so an arbitrary key cannot be stored; the recoverable material kovra holds is the kdf.salt → backup carries the salt, restored to kdf.salt. The passphrase stays with the user and is never exported.

Round-tripping a backup in the same mode is idempotent (the same key/salt is restored).

This module is pure: it knows nothing about the keyring backend or the filesystem. The CLI wires export/import around it.

Enums

BackupKind

What a backup blob carries, so import restores it to the right backend (KOV-34). Serialized inside the encrypted payload, never in the clear.

Functions

export_backup

Encrypt data (a master key or a kdf salt, per kind) into an ASCII-armored age blob under passphrase (age-scrypt). The transient plaintext is wiped at the end of the call; only the encrypted blob is returned (I7/I12).

import_backup

Decrypt an export_backup blob with passphrase, returning what it carries (the caller restores it to the right backend). A wrong passphrase, a tampered blob, or an unknown format fails cleanly — never a panic, never the bytes.