mirror of
https://github.com/edgelesssys/constellation.git
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90 lines
2.8 KiB
Go
90 lines
2.8 KiB
Go
/*
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Copyright (c) Edgeless Systems GmbH
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SPDX-License-Identifier: AGPL-3.0-only
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*/
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/*
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This package deals with the low level attestation and verification logic of Constellation nodes.
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General tpm attestation code that is not subjective to a single platform should go into the vtpm package.
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Since attestation capabilities can differ between platforms, the attestation code should go into a subpackage for that respective platform.
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We commonly implement the following two interfaces for a platform:
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// Issuer issues an attestation document.
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type Issuer interface {
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oid.Getter
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Issue(userData []byte, nonce []byte) (quote []byte, err error)
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}
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// Validator is able to validate an attestation document.
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type Validator interface {
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oid.Getter
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Validate(attDoc []byte, nonce []byte) ([]byte, error)
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}
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Attestation code for new platforms needs to implement these two interfaces.
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*/
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package attestation
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import (
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"bytes"
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"crypto/sha256"
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"github.com/edgelesssys/constellation/v2/internal/crypto"
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)
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const (
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// clusterIDContext is the value to use for info when deriving the cluster ID.
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clusterIDContext = "clusterID"
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// MeasurementSecretContext is the value to use for info
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// when deriving the measurement secret from the master secret.
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MeasurementSecretContext = "measurementSecret"
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)
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// Logger is a logger used to print warnings and infos during attestation validation.
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type Logger interface {
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Info(msg string, args ...any)
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Warn(msg string, args ...any)
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}
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// NOPLogger is a no-op implementation of [Logger].
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type NOPLogger struct{}
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// Info is a no-op.
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func (NOPLogger) Info(string, ...interface{}) {}
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// Warn is a no-op.
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func (NOPLogger) Warn(string, ...interface{}) {}
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// DeriveClusterID derives the cluster ID from a salt and secret value.
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func DeriveClusterID(secret, salt []byte) ([]byte, error) {
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return crypto.DeriveKey(secret, salt, []byte(crypto.DEKPrefix+clusterIDContext), crypto.DerivedKeyLengthDefault)
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}
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// MakeExtraData binds userData to a random nonce used in attestation.
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func MakeExtraData(userData []byte, nonce []byte) []byte {
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data := append([]byte{}, userData...)
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data = append(data, nonce...)
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digest := sha256.Sum256(data)
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return digest[:]
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}
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// CompareExtraData compares the extra data of a quote with the expected extra data.
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// Returns true if the data from the quote matches the expected data.
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// If the slices are not of equal length, the shorter slice is padded with zeros.
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func CompareExtraData(quoteData, expectedData []byte) bool {
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if len(quoteData) != len(expectedData) {
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// If the lengths are not equal, pad the shorter slice with zeros.
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diff := len(quoteData) - len(expectedData)
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if diff < 0 {
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diff = -diff
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quoteData = append(quoteData, bytes.Repeat([]byte{0x00}, diff)...)
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} else {
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expectedData = append(expectedData, bytes.Repeat([]byte{0x00}, diff)...)
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}
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}
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return bytes.Equal(quoteData, expectedData)
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}
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