constellation/internal/crypto/crypto.go

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// Package crypto provides functions to for cryptography and random numbers.
package crypto
import (
"crypto/rand"
"crypto/sha256"
"io"
"math/big"
"golang.org/x/crypto/hkdf"
)
const (
StateDiskKeyLength = 32
// DerivedKeyLengthDefault is the default length in bytes for KMS derived keys.
DerivedKeyLengthDefault = 32
// MasterSecretLengthDefault is the default length in bytes for CLI generated master secrets.
MasterSecretLengthDefault = 32
// MasterSecretLengthMin is the minimal length in bytes for user provided master secrets.
MasterSecretLengthMin = 16
// RNGLengthDefault is the number of bytes used for generating nonces.
RNGLengthDefault = 32
// HKDFInfoPrefix is the prefix used for the info parameter in HKDF.
HKDFInfoPrefix = "key-"
)
// DeriveKey derives a key from a secret.
func DeriveKey(secret, salt, info []byte, length uint) ([]byte, error) {
hkdf := hkdf.New(sha256.New, secret, salt, info)
key := make([]byte, length)
if _, err := io.ReadFull(hkdf, key); err != nil {
return nil, err
}
return key, nil
}
// GenerateCertificateSerialNumber generates a random serial number for an X.509 certificate.
func GenerateCertificateSerialNumber() (*big.Int, error) {
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
return rand.Int(rand.Reader, serialNumberLimit)
}
// GenerateRandomBytes reads length bytes from getrandom(2) if available, /dev/urandom otherwise.
func GenerateRandomBytes(length int) ([]byte, error) {
nonce := make([]byte, length)
if _, err := rand.Read(nonce); err != nil {
return nil, err
}
return nonce, nil
}