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5a0234b3f2
* Convert enforceIDKeyDigest setting to enum * Use MAA fallback in Azure SNP attestation * Only create MAA provider if MAA fallback is enabled --------- Signed-off-by: Daniel Weiße <dw@edgeless.systems> Co-authored-by: Thomas Tendyck <tt@edgeless.systems>
216 lines
7.0 KiB
Go
216 lines
7.0 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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// Package idkeydigest contains policies and type definitions
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// for checking the ID Key Digest value in SEV-SNP attestation.
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package idkeydigest
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import (
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"encoding/hex"
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"encoding/json"
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"errors"
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"fmt"
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"strings"
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"github.com/edgelesssys/constellation/v2/internal/cloud/cloudprovider"
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)
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// Config contains the configuration for ID Key Digest validation.
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type Config struct {
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IDKeyDigests IDKeyDigests `json:"idKeyDigests"`
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EnforcementPolicy EnforceIDKeyDigest `json:"enforcementPolicy"`
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MAAURL string `json:"maaURL,omitempty"`
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}
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//go:generate stringer -type=EnforceIDKeyDigest
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// EnforceIDKeyDigest defines the behavior of the validator when the ID key digest is not found in the expected list.
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type EnforceIDKeyDigest uint32
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// TODO: Decide on final value naming.
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const (
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// Unknown is reserved for invalid configurations.
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Unknown EnforceIDKeyDigest = iota
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// StrictChecking will return an error if the ID key digest is not found in the expected list.
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StrictChecking
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// MAAFallback attempts to verify the attestation using Microsoft Azure Attestation (MAA),
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// if the ID key digest is not found in the expected list.
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MAAFallback
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// WarnOnly logs a warning if the ID key digest is not found in the expected list.
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// No error is returned.
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WarnOnly
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)
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// UnmarshalJSON implements the json.Unmarshaler interface.
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func (e *EnforceIDKeyDigest) UnmarshalJSON(b []byte) error {
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return e.unmarshal(func(val any) error {
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return json.Unmarshal(b, val)
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})
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}
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// MarshalJSON implements the json.Marshaler interface.
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func (e EnforceIDKeyDigest) MarshalJSON() ([]byte, error) {
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return json.Marshal(e.String())
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}
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// UnmarshalYAML implements the yaml.Unmarshaler interface.
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func (e *EnforceIDKeyDigest) UnmarshalYAML(unmarshal func(any) error) error {
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return e.unmarshal(unmarshal)
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}
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// MarshalYAML implements the yaml.Marshaler interface.
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func (e EnforceIDKeyDigest) MarshalYAML() (any, error) {
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return e.String(), nil
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}
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func (e *EnforceIDKeyDigest) unmarshal(unmarshalFunc func(any) error) error {
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// Check for legacy format: EnforceIDKeyDigest might be a boolean.
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// If set to true, the value will be set to StrictChecking.
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// If set to false, the value will be set to WarnOnly.
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var legacyEnforce bool
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legacyErr := unmarshalFunc(&legacyEnforce)
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if legacyErr == nil {
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if legacyEnforce {
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*e = StrictChecking
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} else {
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*e = WarnOnly
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}
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return nil
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}
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var enforce string
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if err := unmarshalFunc(&enforce); err != nil {
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return errors.Join(
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err,
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fmt.Errorf("trying legacy format: %w", legacyErr),
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)
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}
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*e = EnforcePolicyFromString(enforce)
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if *e == Unknown {
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return fmt.Errorf("unknown EnforceIDKeyDigest value: %q", enforce)
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}
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return nil
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}
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// EnforcePolicyFromString returns EnforceIDKeyDigest from string.
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func EnforcePolicyFromString(s string) EnforceIDKeyDigest {
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s = strings.ToLower(s)
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switch s {
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case "strictchecking":
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return StrictChecking
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case "maafallback":
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return MAAFallback
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case "warnonly":
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return WarnOnly
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default:
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return Unknown
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}
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}
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// IDKeyDigests is a list of trusted digest values for the ID key.
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type IDKeyDigests [][]byte
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type encodedIDKeyDigests []string
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// encodedDigestLength is the length of a digest in hex encoding.
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const encodedDigestLength = 2 * 48
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// NewIDKeyDigests creates a new IDKeyDigests from a list of digests.
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func NewIDKeyDigests(digests [][]byte) IDKeyDigests {
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idKeyDigests := make(IDKeyDigests, len(digests))
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copy(idKeyDigests, digests)
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return idKeyDigests
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}
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// DefaultsFor returns the default IDKeyDigests for the given cloud provider.
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func DefaultsFor(csp cloudprovider.Provider) IDKeyDigests {
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switch csp {
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case cloudprovider.Azure:
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return IDKeyDigests{
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{0x57, 0x48, 0x6a, 0x44, 0x7e, 0xc0, 0xf1, 0x95, 0x80, 0x02, 0xa2, 0x2a, 0x06, 0xb7, 0x67, 0x3b, 0x9f, 0xd2, 0x7d, 0x11, 0xe1, 0xc6, 0x52, 0x74, 0x98, 0x05, 0x60, 0x54, 0xc5, 0xfa, 0x92, 0xd2, 0x3c, 0x50, 0xf9, 0xde, 0x44, 0x07, 0x27, 0x60, 0xfe, 0x2b, 0x6f, 0xb8, 0x97, 0x40, 0xb6, 0x96},
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{0x03, 0x56, 0x21, 0x58, 0x82, 0xa8, 0x25, 0x27, 0x9a, 0x85, 0xb3, 0x00, 0xb0, 0xb7, 0x42, 0x93, 0x1d, 0x11, 0x3b, 0xf7, 0xe3, 0x2d, 0xde, 0x2e, 0x50, 0xff, 0xde, 0x7e, 0xc7, 0x43, 0xca, 0x49, 0x1e, 0xcd, 0xd7, 0xf3, 0x36, 0xdc, 0x28, 0xa6, 0xe0, 0xb2, 0xbb, 0x57, 0xaf, 0x7a, 0x44, 0xa3},
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{0x93, 0x4f, 0x68, 0xbd, 0x8b, 0xa0, 0x19, 0x38, 0xee, 0xc2, 0x14, 0x75, 0xc8, 0x72, 0xe3, 0xa9, 0x42, 0xb6, 0x0c, 0x59, 0xfa, 0xfc, 0x6d, 0xf9, 0xe9, 0xa7, 0x6e, 0xe6, 0x6b, 0xc4, 0x7f, 0x2d, 0x09, 0xc6, 0x76, 0xf6, 0x1c, 0x03, 0x15, 0xc5, 0x78, 0xda, 0x26, 0x08, 0x5f, 0xb1, 0x3a, 0x71},
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}
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default:
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return nil
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}
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}
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// MarshalYAML implements the yaml.Marshaler interface.
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func (d IDKeyDigests) MarshalYAML() (any, error) {
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encodedIDKeyDigests := []string{}
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for _, digest := range d {
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encodedIDKeyDigests = append(encodedIDKeyDigests, hex.EncodeToString(digest))
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}
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return encodedIDKeyDigests, nil
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}
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// UnmarshalYAML implements the yaml.Unmarshaler interface.
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func (d *IDKeyDigests) UnmarshalYAML(unmarshal func(any) error) error {
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var encodedDigests encodedIDKeyDigests
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if err := unmarshal(&encodedDigests); err != nil {
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// Unmarshalling failed, IDKeyDigests might be a simple string instead of IDKeyDigests struct.
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var unmarshalledString string
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if legacyErr := unmarshal(&unmarshalledString); legacyErr != nil {
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return errors.Join(
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err,
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fmt.Errorf("trying legacy format: %w", legacyErr),
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)
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}
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encodedDigests = append(encodedDigests, unmarshalledString)
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}
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if err := d.unmarshal(encodedDigests); err != nil {
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return fmt.Errorf("unmarshalling yaml: %w", err)
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}
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return nil
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}
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// MarshalJSON implements the json.Marshaler interface.
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func (d IDKeyDigests) MarshalJSON() ([]byte, error) {
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encodedIDKeyDigests := []string{}
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for _, digest := range d {
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encodedIDKeyDigests = append(encodedIDKeyDigests, hex.EncodeToString(digest))
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}
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return json.Marshal(encodedIDKeyDigests)
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}
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// UnmarshalJSON implements the json.Unmarshaler interface.
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func (d *IDKeyDigests) UnmarshalJSON(b []byte) error {
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var encodedDigests encodedIDKeyDigests
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if err := json.Unmarshal(b, &encodedDigests); err != nil {
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// Unmarshalling failed, IDKeyDigests might be a simple string instead of IDKeyDigests struct.
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var unmarshalledString string
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if legacyErr := json.Unmarshal(b, &unmarshalledString); legacyErr != nil {
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return errors.Join(
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err,
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fmt.Errorf("trying legacy format: %w", legacyErr),
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)
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}
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encodedDigests = []string{unmarshalledString}
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}
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if err := d.unmarshal(encodedDigests); err != nil {
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return fmt.Errorf("unmarshalling json: %w", err)
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}
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return nil
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}
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// unmarshal is a helper function for unmarshalling encodedIDKeyDigests into IDKeyDigests.
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func (d *IDKeyDigests) unmarshal(encodedDigests encodedIDKeyDigests) error {
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for _, encodedDigest := range encodedDigests {
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if len(encodedDigest) != encodedDigestLength {
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return fmt.Errorf("invalid digest length: %d", len(encodedDigest))
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}
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digest, err := hex.DecodeString(encodedDigest)
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if err != nil {
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return fmt.Errorf("decoding digest: %w", err)
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}
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*d = append(*d, digest)
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}
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return nil
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}
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