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defaults.go
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defaults.go
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// Package defaults is a collection of helpers to retrieve the SDK's default
// configuration and handlers.
//
// Generally this package shouldn't be used directly, but session.Session
// instead. This package is useful when you need to reset the defaults
// of a session or service client to the SDK defaults before setting
// additional parameters.
package defaults
import (
"fmt"
"io/ioutil"
"net"
"net/http"
"net/url"
"os"
"time"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/awserr"
"github.com/aws/aws-sdk-go/aws/corehandlers"
"github.com/aws/aws-sdk-go/aws/credentials"
"github.com/aws/aws-sdk-go/aws/credentials/ec2rolecreds"
"github.com/aws/aws-sdk-go/aws/credentials/endpointcreds"
"github.com/aws/aws-sdk-go/aws/ec2metadata"
"github.com/aws/aws-sdk-go/aws/endpoints"
"github.com/aws/aws-sdk-go/aws/request"
"github.com/aws/aws-sdk-go/internal/shareddefaults"
)
// A Defaults provides a collection of default values for SDK clients.
type Defaults struct {
Config *aws.Config
Handlers request.Handlers
}
// Get returns the SDK's default values with Config and handlers pre-configured.
func Get() Defaults {
cfg := Config()
handlers := Handlers()
cfg.Credentials = CredChain(cfg, handlers)
return Defaults{
Config: cfg,
Handlers: handlers,
}
}
// Config returns the default configuration without credentials.
// To retrieve a config with credentials also included use
// `defaults.Get().Config` instead.
//
// Generally you shouldn't need to use this method directly, but
// is available if you need to reset the configuration of an
// existing service client or session.
func Config() *aws.Config {
return aws.NewConfig().
WithCredentials(credentials.AnonymousCredentials).
WithRegion(os.Getenv("AWS_REGION")).
WithHTTPClient(http.DefaultClient).
WithMaxRetries(aws.UseServiceDefaultRetries).
WithLogger(aws.NewDefaultLogger()).
WithLogLevel(aws.LogOff).
WithEndpointResolver(endpoints.DefaultResolver())
}
// Handlers returns the default request handlers.
//
// Generally you shouldn't need to use this method directly, but
// is available if you need to reset the request handlers of an
// existing service client or session.
func Handlers() request.Handlers {
var handlers request.Handlers
handlers.Validate.PushBackNamed(corehandlers.ValidateEndpointHandler)
handlers.Validate.AfterEachFn = request.HandlerListStopOnError
handlers.Build.PushBackNamed(corehandlers.SDKVersionUserAgentHandler)
handlers.Build.PushBackNamed(corehandlers.AddAwsInternal)
handlers.Build.PushBackNamed(corehandlers.AddHostExecEnvUserAgentHander)
handlers.Build.AfterEachFn = request.HandlerListStopOnError
handlers.Sign.PushBackNamed(corehandlers.BuildContentLengthHandler)
handlers.Send.PushBackNamed(corehandlers.ValidateReqSigHandler)
handlers.Send.PushBackNamed(corehandlers.SendHandler)
handlers.AfterRetry.PushBackNamed(corehandlers.AfterRetryHandler)
handlers.ValidateResponse.PushBackNamed(corehandlers.ValidateResponseHandler)
return handlers
}
// CredChain returns the default credential chain.
//
// Generally you shouldn't need to use this method directly, but
// is available if you need to reset the credentials of an
// existing service client or session's Config.
func CredChain(cfg *aws.Config, handlers request.Handlers) *credentials.Credentials {
return credentials.NewCredentials(&credentials.ChainProvider{
VerboseErrors: aws.BoolValue(cfg.CredentialsChainVerboseErrors),
Providers: CredProviders(cfg, handlers),
})
}
// CredProviders returns the slice of providers used in
// the default credential chain.
//
// For applications that need to use some other provider (for example use
// different environment variables for legacy reasons) but still fall back
// on the default chain of providers. This allows that default chaint to be
// automatically updated
func CredProviders(cfg *aws.Config, handlers request.Handlers) []credentials.Provider {
return []credentials.Provider{
&credentials.EnvProvider{},
&credentials.SharedCredentialsProvider{Filename: "", Profile: ""},
RemoteCredProvider(*cfg, handlers),
}
}
const (
httpProviderAuthorizationEnvVar = "AWS_CONTAINER_AUTHORIZATION_TOKEN"
httpProviderAuthFileEnvVar = "AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE"
httpProviderEnvVar = "AWS_CONTAINER_CREDENTIALS_FULL_URI"
)
// direct representation of the IPv4 address for the ECS container
// "169.254.170.2"
var ecsContainerIPv4 net.IP = []byte{
169, 254, 170, 2,
}
// direct representation of the IPv4 address for the EKS container
// "169.254.170.23"
var eksContainerIPv4 net.IP = []byte{
169, 254, 170, 23,
}
// direct representation of the IPv6 address for the EKS container
// "fd00:ec2::23"
var eksContainerIPv6 net.IP = []byte{
0xFD, 0, 0xE, 0xC2,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0x23,
}
// RemoteCredProvider returns a credentials provider for the default remote
// endpoints such as EC2 or ECS Roles.
func RemoteCredProvider(cfg aws.Config, handlers request.Handlers) credentials.Provider {
if u := os.Getenv(httpProviderEnvVar); len(u) > 0 {
return localHTTPCredProvider(cfg, handlers, u)
}
if uri := os.Getenv(shareddefaults.ECSCredsProviderEnvVar); len(uri) > 0 {
u := fmt.Sprintf("%s%s", shareddefaults.ECSContainerCredentialsURI, uri)
return httpCredProvider(cfg, handlers, u)
}
return ec2RoleProvider(cfg, handlers)
}
var lookupHostFn = net.LookupHost
// isAllowedHost allows host to be loopback or known ECS/EKS container IPs
//
// host can either be an IP address OR an unresolved hostname - resolution will
// be automatically performed in the latter case
func isAllowedHost(host string) (bool, error) {
if ip := net.ParseIP(host); ip != nil {
return isIPAllowed(ip), nil
}
addrs, err := lookupHostFn(host)
if err != nil {
return false, err
}
for _, addr := range addrs {
if ip := net.ParseIP(addr); ip == nil || !isIPAllowed(ip) {
return false, nil
}
}
return true, nil
}
func isIPAllowed(ip net.IP) bool {
return ip.IsLoopback() ||
ip.Equal(ecsContainerIPv4) ||
ip.Equal(eksContainerIPv4) ||
ip.Equal(eksContainerIPv6)
}
func localHTTPCredProvider(cfg aws.Config, handlers request.Handlers, u string) credentials.Provider {
var errMsg string
parsed, err := url.Parse(u)
if err != nil {
errMsg = fmt.Sprintf("invalid URL, %v", err)
} else {
host := aws.URLHostname(parsed)
if len(host) == 0 {
errMsg = "unable to parse host from local HTTP cred provider URL"
} else if parsed.Scheme == "http" {
if isAllowedHost, allowHostErr := isAllowedHost(host); allowHostErr != nil {
errMsg = fmt.Sprintf("failed to resolve host %q, %v", host, allowHostErr)
} else if !isAllowedHost {
errMsg = fmt.Sprintf("invalid endpoint host, %q, only loopback/ecs/eks hosts are allowed.", host)
}
}
}
if len(errMsg) > 0 {
if cfg.Logger != nil {
cfg.Logger.Log("Ignoring, HTTP credential provider", errMsg, err)
}
return credentials.ErrorProvider{
Err: awserr.New("CredentialsEndpointError", errMsg, err),
ProviderName: endpointcreds.ProviderName,
}
}
return httpCredProvider(cfg, handlers, u)
}
func httpCredProvider(cfg aws.Config, handlers request.Handlers, u string) credentials.Provider {
return endpointcreds.NewProviderClient(cfg, handlers, u,
func(p *endpointcreds.Provider) {
p.ExpiryWindow = 5 * time.Minute
p.AuthorizationToken = os.Getenv(httpProviderAuthorizationEnvVar)
if authFilePath := os.Getenv(httpProviderAuthFileEnvVar); authFilePath != "" {
p.AuthorizationTokenProvider = endpointcreds.TokenProviderFunc(func() (string, error) {
if contents, err := ioutil.ReadFile(authFilePath); err != nil {
return "", fmt.Errorf("failed to read authorization token from %v: %v", authFilePath, err)
} else {
return string(contents), nil
}
})
}
},
)
}
func ec2RoleProvider(cfg aws.Config, handlers request.Handlers) credentials.Provider {
resolver := cfg.EndpointResolver
if resolver == nil {
resolver = endpoints.DefaultResolver()
}
e, _ := resolver.EndpointFor(endpoints.Ec2metadataServiceID, "")
return &ec2rolecreds.EC2RoleProvider{
Client: ec2metadata.NewClient(cfg, handlers, e.URL, e.SigningRegion),
ExpiryWindow: 5 * time.Minute,
}
}