mirror of
https://github.com/google/go-attestation.git
synced 2025-02-07 03:09:11 +00:00
0efaf4b19f
Event log verification is terrible and easy to mess up. Even if you replay against the PCRs there are still values that can be tampered with or reordered. PCRs also shouldn't be trusted unless they're attested to have come from the correct TPM. Given this, it seems advantageous to add some ability to consume raw event logs, even if it's just for debugging.
745 lines
21 KiB
Go
745 lines
21 KiB
Go
// Copyright 2019 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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package attest
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import (
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"bytes"
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"crypto"
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"crypto/rsa"
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"crypto/sha1"
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"crypto/sha256"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"sort"
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"strings"
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// Ensure hashes are available.
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_ "crypto/sha256"
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"github.com/google/go-tpm/tpm2"
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"github.com/google/go-tpm/tpmutil"
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)
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// ReplayError describes the parsed events that failed to verify against
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// a particular PCR.
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type ReplayError struct {
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Events []Event
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// InvalidPCRs reports the set of PCRs where the event log replay failed.
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InvalidPCRs []int
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}
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func (e ReplayError) affected(pcr int) bool {
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for _, p := range e.InvalidPCRs {
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if p == pcr {
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return true
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}
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}
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return false
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}
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// Error returns a human-friendly description of replay failures.
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func (e ReplayError) Error() string {
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return fmt.Sprintf("event log failed to verify: the following registers failed to replay: %v", e.InvalidPCRs)
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}
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// TPM algorithms. See the TPM 2.0 specification section 6.3.
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//
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// https://trustedcomputinggroup.org/wp-content/uploads/TPM-Rev-2.0-Part-2-Structures-01.38.pdf#page=42
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const (
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algSHA1 uint16 = 0x0004
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algSHA256 uint16 = 0x000B
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)
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// EventType indicates what kind of data an event is reporting.
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//
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// https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClientSpecPlat_TPM_2p0_1p04_pub.pdf#page=103
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type EventType uint32
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var eventTypeStrings = map[uint32]string{
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0x00000000: "EV_PREBOOT_CERT",
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0x00000001: "EV_POST_CODE",
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0x00000002: "EV_UNUSED",
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0x00000003: "EV_NO_ACTION",
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0x00000004: "EV_SEPARATOR",
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0x00000005: "EV_ACTION",
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0x00000006: "EV_EVENT_TAG",
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0x00000007: "EV_S_CRTM_CONTENTS",
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0x00000008: "EV_S_CRTM_VERSION",
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0x00000009: "EV_CPU_MICROCODE",
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0x0000000A: "EV_PLATFORM_CONFIG_FLAGS",
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0x0000000B: "EV_TABLE_OF_DEVICES",
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0x0000000C: "EV_COMPACT_HASH",
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0x0000000D: "EV_IPL",
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0x0000000E: "EV_IPL_PARTITION_DATA",
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0x0000000F: "EV_NONHOST_CODE",
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0x00000010: "EV_NONHOST_CONFIG",
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0x00000011: "EV_NONHOST_INFO",
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0x00000012: "EV_OMIT_BOOT_DEVICE_EVENTS",
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0x80000000: "EV_EFI_EVENT_BASE",
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0x80000001: "EV_EFI_VARIABLE_DRIVER_CONFIG",
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0x80000002: "EV_EFI_VARIABLE_BOOT",
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0x80000003: "EV_EFI_BOOT_SERVICES_APPLICATION",
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0x80000004: "EV_EFI_BOOT_SERVICES_DRIVER",
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0x80000005: "EV_EFI_RUNTIME_SERVICES_DRIVER",
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0x80000006: "EV_EFI_GPT_EVENT",
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0x80000007: "EV_EFI_ACTION",
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0x80000008: "EV_EFI_PLATFORM_FIRMWARE_BLOB",
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0x80000009: "EV_EFI_HANDOFF_TABLES",
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0x80000010: "EV_EFI_HCRTM_EVENT",
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0x800000E0: "EV_EFI_VARIABLE_AUTHORITY",
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}
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// String returns the Spec name of the EventType, for example "EV_ACTION". If
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// unknown, it returns a formatted string of the EventType value.
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func (e EventType) String() string {
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if s, ok := eventTypeStrings[uint32(e)]; ok {
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return s
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}
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// NOTE: 0x00000013-0x0000FFFF are reserverd. Should we include that
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// information in the formatting?
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return fmt.Sprintf("EventType(0x%08x)", uint32(e))
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}
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// Event is a single event from a TCG event log. This reports descrete items such
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// as BIOs measurements or EFI states.
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//
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// There are many pitfalls for using event log events correctly to determine the
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// state of a machine[1]. In general it's must safer to only rely on the raw PCR
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// values and use the event log for debugging.
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//
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// [1] https://github.com/google/go-attestation/blob/master/docs/event-log-disclosure.md
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type Event struct {
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// order of the event in the event log.
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sequence int
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// Index of the PCR that this event was replayed against.
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Index int
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// Untrusted type of the event. This value is not verified by event log replays
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// and can be tampered with. It should NOT be used without additional context,
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// and unrecognized event types should result in errors.
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Type EventType
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// Data of the event. For certain kinds of events, this must match the event
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// digest to be valid.
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Data []byte
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// Digest is the verified digest of the event data. While an event can have
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// multiple for different hash values, this is the one that was matched to the
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// PCR value.
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Digest []byte
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// TODO(ericchiang): Provide examples or links for which event types must
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// match their data to their digest.
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}
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func (e *Event) digestEquals(b []byte) error {
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if len(e.Digest) == 0 {
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return errors.New("no digests present")
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}
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switch len(e.Digest) {
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case crypto.SHA256.Size():
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s := sha256.Sum256(b)
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if bytes.Equal(s[:], e.Digest) {
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return nil
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}
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case crypto.SHA1.Size():
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s := sha1.Sum(b)
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if bytes.Equal(s[:], e.Digest) {
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return nil
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}
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default:
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return fmt.Errorf("cannot compare hash of length %d", len(e.Digest))
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}
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return fmt.Errorf("digest (len %d) does not match", len(e.Digest))
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}
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// EventLog is a parsed measurement log. This contains unverified data representing
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// boot events that must be replayed against PCR values to determine authenticity.
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type EventLog struct {
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// Algs holds the set of algorithms that the event log uses.
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Algs []HashAlg
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rawEvents []rawEvent
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}
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func (e *EventLog) clone() *EventLog {
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out := EventLog{
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Algs: make([]HashAlg, len(e.Algs)),
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rawEvents: make([]rawEvent, len(e.rawEvents)),
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}
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copy(out.Algs, e.Algs)
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copy(out.rawEvents, e.rawEvents)
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return &out
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}
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// Events returns events that have not been replayed against the PCR values and
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// are therefore unverified. The returned events contain the digest that matches
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// the provided hash algorithm, or are empty if that event didn't contain a
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// digest for that hash.
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//
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// This method is insecure and should only be used for debugging.
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func (e *EventLog) Events(hash HashAlg) []Event {
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var events []Event
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for _, re := range e.rawEvents {
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ev := Event{
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Index: re.index,
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Type: re.typ,
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Data: re.data,
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}
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for _, digest := range re.digests {
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if hash.cryptoHash() != digest.hash {
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continue
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}
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ev.Digest = digest.data
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break
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}
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events = append(events, ev)
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}
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return events
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}
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// Verify replays the event log against a TPM's PCR values, returning the
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// events which could be matched to a provided PCR value.
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//
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// PCRs provide no security guarentees unless they're attested to have been
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// generated by a TPM. Verify does not perform these checks.
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//
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// An error is returned if the replayed digest for events with a given PCR
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// index do not match any provided value for that PCR index.
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func (e *EventLog) Verify(pcrs []PCR) ([]Event, error) {
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events, err := e.verify(pcrs)
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// If there were any issues replaying the PCRs, try each of the workarounds
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// in turn.
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// TODO(jsonp): Allow workarounds to be combined.
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if rErr, isReplayErr := err.(ReplayError); isReplayErr {
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for _, wkrd := range eventlogWorkarounds {
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if !rErr.affected(wkrd.affectedPCR) {
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continue
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}
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el := e.clone()
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if err := wkrd.apply(el); err != nil {
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return nil, fmt.Errorf("failed applying workaround %q: %v", wkrd.id, err)
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}
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if events, err := el.verify(pcrs); err == nil {
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return events, nil
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}
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}
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}
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return events, err
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}
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func (e *EventLog) verify(pcrs []PCR) ([]Event, error) {
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events, err := replayEvents(e.rawEvents, pcrs)
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if err != nil {
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if _, isReplayErr := err.(ReplayError); isReplayErr {
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return nil, err
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}
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return nil, fmt.Errorf("pcrs failed to replay: %v", err)
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}
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return events, nil
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}
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type rawAttestationData struct {
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Version [4]byte // This MUST be 1.1.0.0
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Fixed [4]byte // This SHALL always be the string ‘QUOT’
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Digest [20]byte // PCR Composite Hash
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Nonce [20]byte // Nonce Hash
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}
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var (
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fixedQuote = [4]byte{'Q', 'U', 'O', 'T'}
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)
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type rawPCRComposite struct {
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Size uint16 // always 3
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PCRMask [3]byte
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Values tpmutil.U32Bytes
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}
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func (a *AKPublic) validate12Quote(quote Quote, pcrs []PCR, nonce []byte) error {
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pub, ok := a.Public.(*rsa.PublicKey)
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if !ok {
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return fmt.Errorf("unsupported public key type: %T", a.Public)
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}
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qHash := sha1.Sum(quote.Quote)
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if err := rsa.VerifyPKCS1v15(pub, crypto.SHA1, qHash[:], quote.Signature); err != nil {
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return fmt.Errorf("invalid quote signature: %v", err)
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}
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var att rawAttestationData
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if _, err := tpmutil.Unpack(quote.Quote, &att); err != nil {
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return fmt.Errorf("parsing quote: %v", err)
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}
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// TODO(ericchiang): validate Version field.
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if att.Nonce != sha1.Sum(nonce) {
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return fmt.Errorf("invalid nonce")
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}
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if att.Fixed != fixedQuote {
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return fmt.Errorf("quote wasn't a QUOT object: %x", att.Fixed)
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}
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// See 5.4.1 Creating a PCR composite hash
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sort.Slice(pcrs, func(i, j int) bool { return pcrs[i].Index < pcrs[j].Index })
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var (
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pcrMask [3]byte // bitmap indicating which PCRs are active
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values []byte // appended values of all PCRs
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)
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for _, pcr := range pcrs {
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if pcr.Index < 0 || pcr.Index >= 24 {
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return fmt.Errorf("invalid PCR index: %d", pcr.Index)
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}
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pcrMask[pcr.Index/8] |= 1 << uint(pcr.Index%8)
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values = append(values, pcr.Digest...)
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}
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composite, err := tpmutil.Pack(rawPCRComposite{3, pcrMask, values})
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if err != nil {
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return fmt.Errorf("marshaling PCRs: %v", err)
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}
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if att.Digest != sha1.Sum(composite) {
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return fmt.Errorf("PCRs passed didn't match quote: %v", err)
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}
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return nil
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}
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func (a *AKPublic) validate20Quote(quote Quote, pcrs []PCR, nonce []byte) error {
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sig, err := tpm2.DecodeSignature(bytes.NewBuffer(quote.Signature))
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if err != nil {
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return fmt.Errorf("parse quote signature: %v", err)
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}
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sigHash := a.Hash.New()
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sigHash.Write(quote.Quote)
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switch pub := a.Public.(type) {
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case *rsa.PublicKey:
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if sig.RSA == nil {
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return fmt.Errorf("rsa public key provided for ec signature")
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}
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sigBytes := []byte(sig.RSA.Signature)
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if err := rsa.VerifyPKCS1v15(pub, a.Hash, sigHash.Sum(nil), sigBytes); err != nil {
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return fmt.Errorf("invalid quote signature: %v", err)
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}
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default:
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// TODO(ericchiang): support ecdsa
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return fmt.Errorf("unsupported public key type %T", pub)
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}
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att, err := tpm2.DecodeAttestationData(quote.Quote)
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if err != nil {
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return fmt.Errorf("parsing quote signature: %v", err)
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}
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if att.Type != tpm2.TagAttestQuote {
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return fmt.Errorf("attestation isn't a quote, tag of type 0x%x", att.Type)
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}
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if !bytes.Equal([]byte(att.ExtraData), nonce) {
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return fmt.Errorf("nonce didn't match: %v", err)
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}
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pcrByIndex := map[int][]byte{}
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pcrDigestAlg := HashAlg(att.AttestedQuoteInfo.PCRSelection.Hash).cryptoHash()
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for _, pcr := range pcrs {
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if pcr.DigestAlg == pcrDigestAlg {
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pcrByIndex[pcr.Index] = pcr.Digest
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}
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}
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sigHash.Reset()
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for _, index := range att.AttestedQuoteInfo.PCRSelection.PCRs {
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digest, ok := pcrByIndex[index]
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if !ok {
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return fmt.Errorf("quote was over PCR %d which wasn't provided", index)
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}
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sigHash.Write(digest)
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}
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if !bytes.Equal(sigHash.Sum(nil), att.AttestedQuoteInfo.PCRDigest) {
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return fmt.Errorf("quote digest didn't match pcrs provided")
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}
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return nil
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}
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func extend(pcr PCR, replay []byte, e rawEvent, locality byte) (pcrDigest []byte, eventDigest []byte, err error) {
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h := pcr.DigestAlg
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for _, digest := range e.digests {
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if digest.hash != pcr.DigestAlg {
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continue
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}
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if len(digest.data) != len(pcr.Digest) {
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return nil, nil, fmt.Errorf("digest data length (%d) doesn't match PCR digest length (%d)", len(digest.data), len(pcr.Digest))
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}
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hash := h.New()
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if len(replay) != 0 {
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hash.Write(replay)
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} else {
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b := make([]byte, h.Size())
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b[h.Size()-1] = locality
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hash.Write(b)
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}
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hash.Write(digest.data)
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return hash.Sum(nil), digest.data, nil
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}
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return nil, nil, fmt.Errorf("no event digest matches pcr algorithm: %v", pcr.DigestAlg)
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}
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// replayPCR replays the event log for a specific PCR, using pcr and
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// event digests with the algorithm in pcr. An error is returned if the
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// replayed values do not match the final PCR digest, or any event tagged
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// with that PCR does not posess an event digest with the specified algorithm.
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func replayPCR(rawEvents []rawEvent, pcr PCR) ([]Event, bool) {
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var (
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replay []byte
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outEvents []Event
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locality byte
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)
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for _, e := range rawEvents {
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if e.index != pcr.Index {
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continue
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}
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// If TXT is enabled then the first event for PCR0
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// should be a StartupLocality event. The final byte
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// of this event indicates the locality from which
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// TPM2_Startup() was issued. The initial value of
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// PCR0 is equal to the locality.
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if e.typ == eventTypeNoAction {
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if pcr.Index == 0 && len(e.data) == 17 && strings.HasPrefix(string(e.data), "StartupLocality") {
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locality = e.data[len(e.data)-1]
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}
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continue
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}
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replayValue, digest, err := extend(pcr, replay, e, locality)
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if err != nil {
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return nil, false
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}
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replay = replayValue
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outEvents = append(outEvents, Event{sequence: e.sequence, Data: e.data, Digest: digest, Index: pcr.Index, Type: e.typ})
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}
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if len(outEvents) > 0 && !bytes.Equal(replay, pcr.Digest) {
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return nil, false
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}
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return outEvents, true
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}
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type pcrReplayResult struct {
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events []Event
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successful bool
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}
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func replayEvents(rawEvents []rawEvent, pcrs []PCR) ([]Event, error) {
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var (
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invalidReplays []int
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verifiedEvents []Event
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allPCRReplays = map[int][]pcrReplayResult{}
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)
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// Replay the event log for every PCR and digest algorithm combination.
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for _, pcr := range pcrs {
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events, ok := replayPCR(rawEvents, pcr)
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allPCRReplays[pcr.Index] = append(allPCRReplays[pcr.Index], pcrReplayResult{events, ok})
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}
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// Record PCR indices which do not have any successful replay. Record the
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// events for a successful replay.
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pcrLoop:
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for i, replaysForPCR := range allPCRReplays {
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for _, replay := range replaysForPCR {
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if replay.successful {
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// We consider the PCR verified at this stage: The replay of values with
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// one digest algorithm matched a provided value.
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// As such, we save the PCR's events, and proceed to the next PCR.
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verifiedEvents = append(verifiedEvents, replay.events...)
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continue pcrLoop
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}
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}
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invalidReplays = append(invalidReplays, i)
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}
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if len(invalidReplays) > 0 {
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events := make([]Event, 0, len(rawEvents))
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for _, e := range rawEvents {
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events = append(events, Event{e.sequence, e.index, e.typ, e.data, nil})
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}
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return nil, ReplayError{
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Events: events,
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InvalidPCRs: invalidReplays,
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}
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}
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||
|
||
sort.Slice(verifiedEvents, func(i int, j int) bool {
|
||
return verifiedEvents[i].sequence < verifiedEvents[j].sequence
|
||
})
|
||
return verifiedEvents, nil
|
||
}
|
||
|
||
// EV_NO_ACTION is a special event type that indicates information to the parser
|
||
// instead of holding a measurement. For TPM 2.0, this event type is used to signal
|
||
// switching from SHA1 format to a variable length digest.
|
||
//
|
||
// https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClientSpecPlat_TPM_2p0_1p04_pub.pdf#page=110
|
||
const eventTypeNoAction = 0x03
|
||
|
||
// ParseEventLog parses an unverified measurement log.
|
||
func ParseEventLog(measurementLog []byte) (*EventLog, error) {
|
||
var specID *specIDEvent
|
||
r := bytes.NewBuffer(measurementLog)
|
||
parseFn := parseRawEvent
|
||
var el EventLog
|
||
e, err := parseFn(r, specID)
|
||
if err != nil {
|
||
return nil, fmt.Errorf("parse first event: %v", err)
|
||
}
|
||
if e.typ == eventTypeNoAction {
|
||
specID, err = parseSpecIDEvent(e.data)
|
||
if err != nil {
|
||
return nil, fmt.Errorf("failed to parse spec ID event: %v", err)
|
||
}
|
||
for _, alg := range specID.algs {
|
||
switch tpm2.Algorithm(alg.ID) {
|
||
case tpm2.AlgSHA1:
|
||
el.Algs = append(el.Algs, HashSHA1)
|
||
case tpm2.AlgSHA256:
|
||
el.Algs = append(el.Algs, HashSHA256)
|
||
}
|
||
}
|
||
if len(el.Algs) == 0 {
|
||
return nil, fmt.Errorf("measurement log didn't use sha1 or sha256 digests")
|
||
}
|
||
// Switch to parsing crypto agile events. Don't include this in the
|
||
// replayed events since it intentionally doesn't extend the PCRs.
|
||
//
|
||
// Note that this doesn't actually guarentee that events have SHA256
|
||
// digests.
|
||
parseFn = parseRawEvent2
|
||
} else {
|
||
el.Algs = []HashAlg{HashSHA1}
|
||
el.rawEvents = append(el.rawEvents, e)
|
||
}
|
||
sequence := 1
|
||
for r.Len() != 0 {
|
||
e, err := parseFn(r, specID)
|
||
if err != nil {
|
||
return nil, err
|
||
}
|
||
e.sequence = sequence
|
||
sequence++
|
||
el.rawEvents = append(el.rawEvents, e)
|
||
}
|
||
return &el, nil
|
||
}
|
||
|
||
type specIDEvent struct {
|
||
algs []specAlgSize
|
||
}
|
||
|
||
type specAlgSize struct {
|
||
ID uint16
|
||
Size uint16
|
||
}
|
||
|
||
// Expected values for various Spec ID Event fields.
|
||
// https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf#page=19
|
||
var wantSignature = [16]byte{0x53, 0x70,
|
||
0x65, 0x63, 0x20, 0x49,
|
||
0x44, 0x20, 0x45, 0x76,
|
||
0x65, 0x6e, 0x74, 0x30,
|
||
0x33, 0x00} // "Spec ID Event03\0"
|
||
|
||
const (
|
||
wantMajor = 2
|
||
wantMinor = 0
|
||
wantErrata = 0
|
||
)
|
||
|
||
// parseSpecIDEvent parses a TCG_EfiSpecIDEventStruct structure from the reader.
|
||
//
|
||
// https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf#page=18
|
||
func parseSpecIDEvent(b []byte) (*specIDEvent, error) {
|
||
r := bytes.NewReader(b)
|
||
var header struct {
|
||
Signature [16]byte
|
||
PlatformClass uint32
|
||
VersionMinor uint8
|
||
VersionMajor uint8
|
||
Errata uint8
|
||
UintnSize uint8
|
||
NumAlgs uint32
|
||
}
|
||
if err := binary.Read(r, binary.LittleEndian, &header); err != nil {
|
||
return nil, fmt.Errorf("reading event header: %v", err)
|
||
}
|
||
if header.Signature != wantSignature {
|
||
return nil, fmt.Errorf("invalid spec id signature: %x", header.Signature)
|
||
}
|
||
if header.VersionMajor != wantMajor {
|
||
return nil, fmt.Errorf("invalid spec major version, got %02x, wanted %02x",
|
||
header.VersionMajor, wantMajor)
|
||
}
|
||
if header.VersionMinor != wantMinor {
|
||
return nil, fmt.Errorf("invalid spec minor version, got %02x, wanted %02x",
|
||
header.VersionMajor, wantMinor)
|
||
}
|
||
|
||
// TODO(ericchiang): Check errata? Or do we expect that to change in ways
|
||
// we're okay with?
|
||
|
||
specAlg := specAlgSize{}
|
||
e := specIDEvent{}
|
||
for i := 0; i < int(header.NumAlgs); i++ {
|
||
if err := binary.Read(r, binary.LittleEndian, &specAlg); err != nil {
|
||
return nil, fmt.Errorf("reading algorithm: %v", err)
|
||
}
|
||
e.algs = append(e.algs, specAlg)
|
||
}
|
||
|
||
var vendorInfoSize uint8
|
||
if err := binary.Read(r, binary.LittleEndian, &vendorInfoSize); err != nil {
|
||
return nil, fmt.Errorf("reading vender info size: %v", err)
|
||
}
|
||
if r.Len() != int(vendorInfoSize) {
|
||
return nil, fmt.Errorf("reading vendor info, expected %d remaining bytes, got %d", vendorInfoSize, r.Len())
|
||
}
|
||
return &e, nil
|
||
}
|
||
|
||
type digest struct {
|
||
hash crypto.Hash
|
||
data []byte
|
||
}
|
||
|
||
type rawEvent struct {
|
||
sequence int
|
||
index int
|
||
typ EventType
|
||
data []byte
|
||
digests []digest
|
||
}
|
||
|
||
// TPM 1.2 event log format. See "5.1 SHA1 Event Log Entry Format"
|
||
// https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf#page=15
|
||
type rawEventHeader struct {
|
||
PCRIndex uint32
|
||
Type uint32
|
||
Digest [20]byte
|
||
EventSize uint32
|
||
}
|
||
|
||
type eventSizeErr struct {
|
||
eventSize uint32
|
||
logSize int
|
||
}
|
||
|
||
func (e *eventSizeErr) Error() string {
|
||
return fmt.Sprintf("event data size (%d bytes) is greater than remaining measurement log (%d bytes)", e.eventSize, e.logSize)
|
||
}
|
||
|
||
func parseRawEvent(r *bytes.Buffer, specID *specIDEvent) (event rawEvent, err error) {
|
||
var h rawEventHeader
|
||
if err = binary.Read(r, binary.LittleEndian, &h); err != nil {
|
||
return event, err
|
||
}
|
||
if h.EventSize == 0 {
|
||
return event, errors.New("event data size is 0")
|
||
}
|
||
if h.EventSize > uint32(r.Len()) {
|
||
return event, &eventSizeErr{h.EventSize, r.Len()}
|
||
}
|
||
|
||
data := make([]byte, int(h.EventSize))
|
||
if _, err := io.ReadFull(r, data); err != nil {
|
||
return event, err
|
||
}
|
||
|
||
digests := []digest{{hash: crypto.SHA1, data: h.Digest[:]}}
|
||
|
||
return rawEvent{
|
||
typ: EventType(h.Type),
|
||
data: data,
|
||
index: int(h.PCRIndex),
|
||
digests: digests,
|
||
}, nil
|
||
}
|
||
|
||
// TPM 2.0 event log format. See "5.2 Crypto Agile Log Entry Format"
|
||
// https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf#page=15
|
||
type rawEvent2Header struct {
|
||
PCRIndex uint32
|
||
Type uint32
|
||
}
|
||
|
||
func parseRawEvent2(r *bytes.Buffer, specID *specIDEvent) (event rawEvent, err error) {
|
||
var h rawEvent2Header
|
||
|
||
if err = binary.Read(r, binary.LittleEndian, &h); err != nil {
|
||
return event, err
|
||
}
|
||
event.typ = EventType(h.Type)
|
||
event.index = int(h.PCRIndex)
|
||
|
||
// parse the event digests
|
||
var numDigests uint32
|
||
if err := binary.Read(r, binary.LittleEndian, &numDigests); err != nil {
|
||
return event, err
|
||
}
|
||
|
||
for i := 0; i < int(numDigests); i++ {
|
||
var algID uint16
|
||
if err := binary.Read(r, binary.LittleEndian, &algID); err != nil {
|
||
return event, err
|
||
}
|
||
var digest digest
|
||
|
||
for _, alg := range specID.algs {
|
||
if alg.ID != algID {
|
||
continue
|
||
}
|
||
if uint16(r.Len()) < alg.Size {
|
||
return event, fmt.Errorf("reading digest: %v", io.ErrUnexpectedEOF)
|
||
}
|
||
digest.data = make([]byte, alg.Size)
|
||
digest.hash = HashAlg(alg.ID).cryptoHash()
|
||
}
|
||
if len(digest.data) == 0 {
|
||
return event, fmt.Errorf("unknown algorithm ID %x", algID)
|
||
}
|
||
if _, err := io.ReadFull(r, digest.data); err != nil {
|
||
return event, err
|
||
}
|
||
event.digests = append(event.digests, digest)
|
||
}
|
||
|
||
// parse event data
|
||
var eventSize uint32
|
||
if err = binary.Read(r, binary.LittleEndian, &eventSize); err != nil {
|
||
return event, err
|
||
}
|
||
if eventSize == 0 {
|
||
return event, errors.New("event data size is 0")
|
||
}
|
||
if eventSize > uint32(r.Len()) {
|
||
return event, &eventSizeErr{eventSize, r.Len()}
|
||
}
|
||
event.data = make([]byte, int(eventSize))
|
||
if _, err := io.ReadFull(r, event.data); err != nil {
|
||
return event, err
|
||
}
|
||
return event, err
|
||
}
|