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package ec2metadata
import (
"net/http"
"sync/atomic"
"time"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/credentials"
"github.com/aws/aws-sdk-go/aws/request"
)
// A tokenProvider struct provides access to EC2Metadata client
// and atomic instance of a token, along with configuredTTL for it.
// tokenProvider also provides an atomic flag to disable the
// fetch token operation.
// The disabled member will use 0 as false, and 1 as true.
type tokenProvider struct {
client *EC2Metadata
token atomic.Value
configuredTTL time.Duration
disabled uint32
}
// A ec2Token struct helps use of token in EC2 Metadata service ops
type ec2Token struct {
token string
credentials.Expiry
}
// newTokenProvider provides a pointer to a tokenProvider instance
func newTokenProvider(c *EC2Metadata, duration time.Duration) *tokenProvider {
return &tokenProvider{client: c, configuredTTL: duration}
}
// fetchTokenHandler fetches token for EC2Metadata service client by default.
func (t *tokenProvider) fetchTokenHandler(r *request.Request) {
// short-circuits to insecure data flow if tokenProvider is disabled.
if v := atomic.LoadUint32(&t.disabled); v == 1 {
return
}
if ec2Token, ok := t.token.Load().(ec2Token); ok && !ec2Token.IsExpired() {
r.HTTPRequest.Header.Set(tokenHeader, ec2Token.token)
return
}
output, err := t.client.getToken(r.Context(), t.configuredTTL)
if err != nil {
// change the disabled flag on token provider to true,
// when error is request timeout error.
if requestFailureError, ok := err.(awserr.RequestFailure); ok {
switch requestFailureError.StatusCode() {
case http.StatusForbidden, http.StatusNotFound, http.StatusMethodNotAllowed:
atomic.StoreUint32(&t.disabled, 1)
case http.StatusBadRequest:
r.Error = requestFailureError
}
// Check if request timed out while waiting for response
if e, ok := requestFailureError.OrigErr().(awserr.Error); ok {
if e.Code() == request.ErrCodeRequestError {
atomic.StoreUint32(&t.disabled, 1)
}
}
}
return
}
newToken := ec2Token{
token: output.Token,
}
newToken.SetExpiration(time.Now().Add(output.TTL), ttlExpirationWindow)
t.token.Store(newToken)
// Inject token header to the request.
if ec2Token, ok := t.token.Load().(ec2Token); ok {
r.HTTPRequest.Header.Set(tokenHeader, ec2Token.token)
}
}
// enableTokenProviderHandler enables the token provider
func (t *tokenProvider) enableTokenProviderHandler(r *request.Request) {
// If the error code status is 401, we enable the token provider
if e, ok := r.Error.(awserr.RequestFailure); ok && e != nil &&
e.StatusCode() == http.StatusUnauthorized {
t.token.Store(ec2Token{})
atomic.StoreUint32(&t.disabled, 0)
}
}
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