VeillaxandClaude Sonnet 5.5
9f2fe4a416
Pages are sealed with AES-256-GCM. Each person's key is derived (HKDF) from a master key in the settings file plus their Authentik issuer and subject. Plain files from earlier versions are read and re-saved encrypted. Mako refuses to open a notebook it cannot decrypt rather than overwrite it. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
79 lines
2.5 KiB
Go
79 lines
2.5 KiB
Go
// Package vault encrypts pages at rest. Every person gets a key of their own, made from the server's
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// master key and who they are in Authentik, so one person's files cannot be opened (or swapped in)
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// with another's key. Who they are is not secret; the master key is what keeps the files private.
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package vault
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/hkdf"
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"crypto/rand"
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"crypto/sha256"
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"errors"
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"fmt"
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)
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// ErrWrongKey means a file is encrypted but this key cannot open it: the master key was changed or
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// lost, or the file was altered.
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var ErrWrongKey = errors.New("these notes were saved with a different encryption key")
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// magic starts every encrypted file, so a plain markdown file can still be told apart and read.
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var magic = []byte("MAKO1\n")
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// MinKey is the shortest master key accepted, in characters.
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const MinKey = 32
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// Cipher seals and opens the files of one person.
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type Cipher struct{ aead cipher.AEAD }
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// New makes the cipher for one person from the master key, the Authentik issuer and their subject.
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func New(master, issuer, sub string) (*Cipher, error) {
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if len(master) < MinKey {
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return nil, fmt.Errorf("the encryption key must be at least %d characters", MinKey)
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}
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if sub == "" {
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return nil, errors.New("no user to make an encryption key for")
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}
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key, err := hkdf.Key(sha256.New, []byte(master), nil, "mako notes v1|"+issuer+"|"+sub, 32)
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if err != nil {
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return nil, err
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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aead, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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return &Cipher{aead}, nil
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}
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// IsSealed says whether data is an encrypted file.
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func IsSealed(data []byte) bool { return bytes.HasPrefix(data, magic) }
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// Seal encrypts a file. The name (the page id) is signed into it, so a file copied over another
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// page's name no longer opens.
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func (c *Cipher) Seal(plain []byte, name string) []byte {
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nonce := make([]byte, c.aead.NonceSize())
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rand.Read(nonce)
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out := make([]byte, 0, len(magic)+len(nonce)+len(plain)+c.aead.Overhead())
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out = append(out, magic...)
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out = append(out, nonce...)
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return c.aead.Seal(out, nonce, plain, []byte(name))
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}
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// Open decrypts a file made by Seal.
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func (c *Cipher) Open(data []byte, name string) ([]byte, error) {
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n := len(magic) + c.aead.NonceSize()
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if !IsSealed(data) || len(data) < n+c.aead.Overhead() {
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return nil, ErrWrongKey
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}
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plain, err := c.aead.Open(nil, data[len(magic):n], data[n:], []byte(name))
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if err != nil {
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return nil, ErrWrongKey
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}
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return plain, nil
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}
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