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// Package ec2metadata provides the client for making API calls to the
// EC2 Metadata service.
//
// This package's client can be disabled completely by setting the environment
// variable "AWS_EC2_METADATA_DISABLED=true". This environment variable set to
// true instructs the SDK to disable the EC2 Metadata client. The client cannot
// be used while the environemnt variable is set to true, (case insensitive).
package ec2metadata
import (
"bytes"
"errors"
"io"
"net/http"
"os"
"strings"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/client"
"github.com/aws/aws-sdk-go/aws/client/metadata"
"github.com/aws/aws-sdk-go/aws/corehandlers"
"github.com/aws/aws-sdk-go/aws/request"
)
// ServiceName is the name of the service.
const ServiceName = "ec2metadata"
const disableServiceEnvVar = "AWS_EC2_METADATA_DISABLED"
// A EC2Metadata is an EC2 Metadata service Client.
type EC2Metadata struct {
*client.Client
}
// New creates a new instance of the EC2Metadata client with a session.
// This client is safe to use across multiple goroutines.
//
//
// Example:
// // Create a EC2Metadata client from just a session.
// svc := ec2metadata.New(mySession)
//
// // Create a EC2Metadata client with additional configuration
// svc := ec2metadata.New(mySession, aws.NewConfig().WithLogLevel(aws.LogDebugHTTPBody))
func New(p client.ConfigProvider, cfgs ...*aws.Config) *EC2Metadata {
c := p.ClientConfig(ServiceName, cfgs...)
return NewClient(*c.Config, c.Handlers, c.Endpoint, c.SigningRegion)
}
// NewClient returns a new EC2Metadata client. Should be used to create
// a client when not using a session. Generally using just New with a session
// is preferred.
//
// If an unmodified HTTP client is provided from the stdlib default, or no client
// the EC2RoleProvider's EC2Metadata HTTP client's timeout will be shortened.
// To disable this set Config.EC2MetadataDisableTimeoutOverride to false. Enabled by default.
func NewClient(cfg aws.Config, handlers request.Handlers, endpoint, signingRegion string, opts ...func(*client.Client)) *EC2Metadata {
if !aws.BoolValue(cfg.EC2MetadataDisableTimeoutOverride) && httpClientZero(cfg.HTTPClient) {
// If the http client is unmodified and this feature is not disabled
// set custom timeouts for EC2Metadata requests.
cfg.HTTPClient = &http.Client{
// use a shorter timeout than default because the metadata
// service is local if it is running, and to fail faster
// if not running on an ec2 instance.
Timeout: 5 * time.Second,
}
}
svc := &EC2Metadata{
Client: client.New(
cfg,
metadata.ClientInfo{
ServiceName: ServiceName,
Endpoint: endpoint,
APIVersion: "latest",
},
handlers,
),
}
svc.Handlers.Unmarshal.PushBack(unmarshalHandler)
svc.Handlers.UnmarshalError.PushBack(unmarshalError)
svc.Handlers.Validate.Clear()
svc.Handlers.Validate.PushBack(validateEndpointHandler)
// Disable the EC2 Metadata service if the environment variable is set.
// This shortcirctes the service's functionality to always fail to send
// requests.
if strings.ToLower(os.Getenv(disableServiceEnvVar)) == "true" {
svc.Handlers.Send.SwapNamed(request.NamedHandler{
Name: corehandlers.SendHandler.Name,
Fn: func(r *request.Request) {
r.Error = awserr.New(
request.CanceledErrorCode,
"EC2 IMDS access disabled via "+disableServiceEnvVar+" env var",
nil)
},
})
}
// Add additional options to the service config
for _, option := range opts {
option(svc.Client)
}
return svc
}
func httpClientZero(c *http.Client) bool {
return c == nil || (c.Transport == nil && c.CheckRedirect == nil && c.Jar == nil && c.Timeout == 0)
}
type metadataOutput struct {
Content string
}
func unmarshalHandler(r *request.Request) {
defer r.HTTPResponse.Body.Close()
b := &bytes.Buffer{}
if _, err := io.Copy(b, r.HTTPResponse.Body); err != nil {
r.Error = awserr.New("SerializationError", "unable to unmarshal EC2 metadata respose", err)
return
}
if data, ok := r.Data.(*metadataOutput); ok {
data.Content = b.String()
}
}
func unmarshalError(r *request.Request) {
defer r.HTTPResponse.Body.Close()
b := &bytes.Buffer{}
if _, err := io.Copy(b, r.HTTPResponse.Body); err != nil {
r.Error = awserr.New("SerializationError", "unable to unmarshal EC2 metadata error respose", err)
return
}
// Response body format is not consistent between metadata endpoints.
// Grab the error message as a string and include that as the source error
r.Error = awserr.New("EC2MetadataError", "failed to make EC2Metadata request", errors.New(b.String()))
}
func validateEndpointHandler(r *request.Request) {
if r.ClientInfo.Endpoint == "" {
r.Error = aws.ErrMissingEndpoint
}
}
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