Example #1
0
// DeriveKey is used to derive the encryption key that should
// be used depending on the policy. If derivation is disabled the
// raw key is used and no context is required, otherwise the KDF
// mode is used with the context to derive the proper key.
func (p *Policy) DeriveKey(context []byte, ver int) ([]byte, error) {
	if p.Keys == nil || len(p.Keys) == 0 {
		if p.Key == nil || len(p.Key) == 0 {
			return nil, certutil.InternalError{Err: "unable to access the key; no key versions found"}
		}
		p.migrateKeyToKeysMap()
	}

	if len(p.Keys) == 0 {
		return nil, certutil.InternalError{Err: "unable to access the key; no key versions found"}
	}

	if ver <= 0 || ver > len(p.Keys) {
		return nil, certutil.UserError{Err: "invalid key version"}
	}

	// Fast-path non-derived keys
	if !p.Derived {
		return p.Keys[ver].Key, nil
	}

	// Ensure a context is provided
	if len(context) == 0 {
		return nil, certutil.UserError{Err: "missing 'context' for key deriviation. The key was created using a derived key, which means additional, per-request information must be included in order to encrypt or decrypt information"}
	}

	switch p.KDFMode {
	case kdfMode:
		prf := kdf.HMACSHA256PRF
		prfLen := kdf.HMACSHA256PRFLen
		return kdf.CounterMode(prf, prfLen, p.Keys[ver].Key, context, 256)
	default:
		return nil, certutil.InternalError{Err: "unsupported key derivation mode"}
	}
}
Example #2
0
// DeriveKey is used to derive the encryption key that should be used depending
// on the policy. If derivation is disabled the raw key is used and no context
// is required, otherwise the KDF mode is used with the context to derive the
// proper key.
func (p *policy) DeriveKey(context []byte, ver int) ([]byte, error) {
	if !p.Type.DerivationSupported() {
		return nil, errutil.UserError{Err: fmt.Sprintf("derivation not supported for key type %v", p.Type)}
	}

	if p.Keys == nil || p.LatestVersion == 0 {
		return nil, errutil.InternalError{Err: "unable to access the key; no key versions found"}
	}

	if ver <= 0 || ver > p.LatestVersion {
		return nil, errutil.UserError{Err: "invalid key version"}
	}

	// Fast-path non-derived keys
	if !p.Derived {
		return p.Keys[ver].AESKey, nil
	}

	// Ensure a context is provided
	if len(context) == 0 {
		return nil, errutil.UserError{Err: "missing 'context' for key deriviation. The key was created using a derived key, which means additional, per-request information must be included in order to encrypt or decrypt information"}
	}

	switch p.KDF {
	case kdf_hmac_sha256_counter:
		prf := kdf.HMACSHA256PRF
		prfLen := kdf.HMACSHA256PRFLen
		return kdf.CounterMode(prf, prfLen, p.Keys[ver].AESKey, context, 256)
	case kdf_hkdf_sha256:
		reader := hkdf.New(sha256.New, p.Keys[ver].AESKey, nil, context)
		derBytes := bytes.NewBuffer(nil)
		derBytes.Grow(32)
		limReader := &io.LimitedReader{
			R: reader,
			N: 32,
		}
		n, err := derBytes.ReadFrom(limReader)
		if err != nil {
			return nil, errutil.InternalError{Err: fmt.Sprintf("error reading returned derived bytes: %v", err)}
		}
		if n != 32 {
			return nil, errutil.InternalError{Err: fmt.Sprintf("unable to read enough derived bytes, needed 32, got %d", n)}
		}
		return derBytes.Bytes(), nil
	default:
		return nil, errutil.InternalError{Err: "unsupported key derivation mode"}
	}
}
Example #3
0
// DeriveKey is used to derive the encryption key that should
// be used depending on the policy. If derivation is disabled the
// raw key is used and no context is required, otherwise the KDF
// mode is used with the context to derive the proper key.
func (p *Policy) DeriveKey(context []byte) ([]byte, error) {
	// Fast-path non-derived keys
	if !p.Derived {
		return p.Key, nil
	}

	// Ensure a context is provided
	if len(context) == 0 {
		return nil, fmt.Errorf("missing 'context' for key deriviation. The key was created using a derived key, which means additional, per-request information must be included in order to encrypt or decrypt information.")
	}

	switch p.KDFMode {
	case kdfMode:
		prf := kdf.HMACSHA256PRF
		prfLen := kdf.HMACSHA256PRFLen
		return kdf.CounterMode(prf, prfLen, p.Key, context, 256)
	default:
		return nil, fmt.Errorf("unsupported key derivation mode")
	}
}