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imds.go
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imds.go
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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.
package client
//go:generate ../../bin/mockgen -copyright_file=../../hack/copyright_header.txt -destination=./mocks/mock_imds.go -package=mocks github.com/Azure/aks-tls-bootstrap-client/pkg/client ImdsClient
import (
"context"
"encoding/json"
"fmt"
"io"
"net/http"
"github.com/Azure/aks-tls-bootstrap-client/pkg/datamodel"
"go.uber.org/zap"
"github.com/avast/retry-go/v4"
)
type ImdsClient interface {
GetMSIToken(ctx context.Context, imdsURL, clientID, resource string) (*datamodel.AADTokenResponse, error)
GetInstanceData(ctx context.Context, imdsURL string) (*datamodel.VMSSInstanceData, error)
GetAttestedData(ctx context.Context, imdsURL, nonce string) (*datamodel.VMSSAttestedData, error)
}
func NewImdsClient(logger *zap.Logger) ImdsClient {
return &imdsClientImpl{
logger: logger,
}
}
type imdsClientImpl struct {
logger *zap.Logger
}
func (c *imdsClientImpl) GetMSIToken(ctx context.Context, imdsURL, clientID, resource string) (*datamodel.AADTokenResponse, error) {
// TODO(cameissner): modify so this works on all clouds later
url := fmt.Sprintf("%s/metadata/identity/oauth2/token", imdsURL)
queryParameters := map[string]string{
apiVersionHeaderKey: imdsMSITokenAPIVersion,
resourceHeaderKey: resource,
}
if clientID != "" {
queryParameters[clientIDHeaderKey] = clientID
}
tokenResponse := &datamodel.AADTokenResponse{}
if err := getImdsData(ctx, c.logger, url, queryParameters, tokenResponse); err != nil {
return nil, fmt.Errorf("failed to retrieve MSI token: %w", err)
}
if tokenResponse.Error != "" {
return nil, fmt.Errorf("failed to retrieve MSI token: %s: %s", tokenResponse.Error, tokenResponse.ErrorDescription)
}
c.logger.Debug("retrieved access token", zap.String("accessToken", tokenResponse.AccessToken))
return tokenResponse, nil
}
func (c *imdsClientImpl) GetInstanceData(ctx context.Context, imdsURL string) (*datamodel.VMSSInstanceData, error) {
url := fmt.Sprintf("%s/metadata/instance", imdsURL)
queryParameters := map[string]string{
apiVersionHeaderKey: imdsInstanceDataAPIVersion,
formatHeaderKey: formatJSON,
}
data := &datamodel.VMSSInstanceData{}
if err := getImdsData(ctx, c.logger, url, queryParameters, data); err != nil {
return nil, fmt.Errorf("failed to retrieve IMDS instance data: %w", err)
}
return data, nil
}
func (c *imdsClientImpl) GetAttestedData(ctx context.Context, imdsURL, nonce string) (*datamodel.VMSSAttestedData, error) {
url := fmt.Sprintf("%s/metadata/attested/document", imdsURL)
queryParameters := map[string]string{
apiVersionHeaderKey: imdsAttestedDataAPIVersion,
formatHeaderKey: formatJSON,
nonceHeaderKey: nonce,
}
data := &datamodel.VMSSAttestedData{}
if err := getImdsData(ctx, c.logger, url, queryParameters, data); err != nil {
return nil, fmt.Errorf("failed to retrieve IMDS attested data: %w", err)
}
return data, nil
}
func getImdsData(ctx context.Context, logger *zap.Logger, url string, queryParameters map[string]string, responseObject interface{}) error {
client := http.Client{
Transport: &http.Transport{
Proxy: nil,
},
}
responseBody, err := retry.DoWithData(func() ([]byte, error) {
request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
if err != nil {
return nil, retry.Unrecoverable(err)
}
request.Header.Add(metadataHeaderKey, "True")
query := request.URL.Query()
for key := range queryParameters {
query.Add(key, queryParameters[key])
}
request.URL.RawQuery = query.Encode()
response, err := client.Do(request)
if err != nil {
return nil, err
}
defer response.Body.Close()
responseBody, err := io.ReadAll(response.Body)
if err != nil {
return nil, err
}
return responseBody, nil
},
retry.Context(ctx),
retry.Attempts(imdsRequestMaxRetries),
retry.MaxDelay(imdsRequestMaxDelay),
retry.DelayType(retry.BackOffDelay))
if err != nil {
return fmt.Errorf("unable to retrieve data from IMDS: %w", err)
}
if err := json.Unmarshal(responseBody, responseObject); err != nil {
return fmt.Errorf("failed to unmarshal IMDS data: %w", err)
}
return nil
}