mrhid6
577b060b8a
services/crypto.go keeps its function names and its KEY_ENCRYPTION_KEY lookup and delegates the cipher, so vantagectl's verify probe can decrypt with the same implementation rather than a second copy.
68 lines
1.9 KiB
Go
68 lines
1.9 KiB
Go
// Package cryptobox is the AES-256-GCM primitive used for everything Vantage
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// encrypts at rest: SSH private keys, key passphrases, vault secrets, OIDC
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// client secrets and console credentials.
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//
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// It takes a raw key and reads no environment. Key sourcing belongs to the
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// caller, because the two callers source it differently: the server reads
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// KEY_ENCRYPTION_KEY at the point of use, while vantagectl is handed one.
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package cryptobox
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/hex"
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"fmt"
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"io"
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)
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// KeySize is the only key length accepted. AES-256 by construction.
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const KeySize = 32
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func gcmFor(key []byte) (cipher.AEAD, error) {
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if len(key) != KeySize {
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return nil, fmt.Errorf("key must be %d bytes, got %d", KeySize, len(key))
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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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return cipher.NewGCM(block)
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}
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// Seal encrypts plaintext and returns nonce||ciphertext, hex encoded.
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func Seal(key []byte, plaintext string) (string, error) {
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gcm, err := gcmFor(key)
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if err != nil {
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return "", err
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}
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nonce := make([]byte, gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return "", err
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}
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return hex.EncodeToString(gcm.Seal(nonce, nonce, []byte(plaintext), nil)), nil
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}
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// Open reverses Seal. Every failure mode returns an error that does not
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// distinguish a wrong key from corrupt data, because the caller cannot act on
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// the difference and an oracle is worth avoiding for free.
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func Open(key []byte, ciphertextHex string) (string, error) {
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gcm, err := gcmFor(key)
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if err != nil {
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return "", err
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}
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data, err := hex.DecodeString(ciphertextHex)
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if err != nil {
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return "", fmt.Errorf("invalid ciphertext encoding")
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}
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n := gcm.NonceSize()
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if len(data) < n {
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return "", fmt.Errorf("ciphertext too short")
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}
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plaintext, err := gcm.Open(nil, data[:n], data[n:], nil)
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if err != nil {
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return "", fmt.Errorf("decryption failed")
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}
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return string(plaintext), nil
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}
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