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session.go
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session.go
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package session
import (
"crypto/tls"
"crypto/x509"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"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/corehandlers"
"github.com/aws/aws-sdk-go/aws/credentials"
"github.com/aws/aws-sdk-go/aws/credentials/stscreds"
"github.com/aws/aws-sdk-go/aws/defaults"
"github.com/aws/aws-sdk-go/aws/endpoints"
"github.com/aws/aws-sdk-go/aws/request"
)
// A Session provides a central location to create service clients from and
// store configurations and request handlers for those services.
//
// Sessions are safe to create service clients concurrently, but it is not safe
// to mutate the Session concurrently.
//
// The Session satisfies the service client's client.ConfigProvider.
type Session struct {
Config *aws.Config
Handlers request.Handlers
}
// New creates a new instance of the handlers merging in the provided configs
// on top of the SDK's default configurations. Once the Session is created it
// can be mutated to modify the Config or Handlers. The Session is safe to be
// read concurrently, but it should not be written to concurrently.
//
// If the AWS_SDK_LOAD_CONFIG environment is set to a truthy value, the New
// method could now encounter an error when loading the configuration. When
// The environment variable is set, and an error occurs, New will return a
// session that will fail all requests reporting the error that occurred while
// loading the session. Use NewSession to get the error when creating the
// session.
//
// If the AWS_SDK_LOAD_CONFIG environment variable is set to a truthy value
// the shared config file (~/.aws/config) will also be loaded, in addition to
// the shared credentials file (~/.aws/credentials). Values set in both the
// shared config, and shared credentials will be taken from the shared
// credentials file.
//
// Deprecated: Use NewSession functions to create sessions instead. NewSession
// has the same functionality as New except an error can be returned when the
// func is called instead of waiting to receive an error until a request is made.
func New(cfgs ...*aws.Config) *Session {
// load initial config from environment
envCfg := loadEnvConfig()
if envCfg.EnableSharedConfig {
var cfg aws.Config
cfg.MergeIn(cfgs...)
s, err := NewSessionWithOptions(Options{
Config: cfg,
SharedConfigState: SharedConfigEnable,
})
if err != nil {
// Old session.New expected all errors to be discovered when
// a request is made, and would report the errors then. This
// needs to be replicated if an error occurs while creating
// the session.
msg := "failed to create session with AWS_SDK_LOAD_CONFIG enabled. " +
"Use session.NewSession to handle errors occurring during session creation."
// Session creation failed, need to report the error and prevent
// any requests from succeeding.
s = &Session{Config: defaults.Config()}
s.Config.MergeIn(cfgs...)
s.Config.Logger.Log("ERROR:", msg, "Error:", err)
s.Handlers.Validate.PushBack(func(r *request.Request) {
r.Error = err
})
}
return s
}
return deprecatedNewSession(cfgs...)
}
// NewSession returns a new Session created from SDK defaults, config files,
// environment, and user provided config files. Once the Session is created
// it can be mutated to modify the Config or Handlers. The Session is safe to
// be read concurrently, but it should not be written to concurrently.
//
// If the AWS_SDK_LOAD_CONFIG environment variable is set to a truthy value
// the shared config file (~/.aws/config) will also be loaded in addition to
// the shared credentials file (~/.aws/credentials). Values set in both the
// shared config, and shared credentials will be taken from the shared
// credentials file. Enabling the Shared Config will also allow the Session
// to be built with retrieving credentials with AssumeRole set in the config.
//
// See the NewSessionWithOptions func for information on how to override or
// control through code how the Session will be created. Such as specifying the
// config profile, and controlling if shared config is enabled or not.
func NewSession(cfgs ...*aws.Config) (*Session, error) {
opts := Options{}
opts.Config.MergeIn(cfgs...)
return NewSessionWithOptions(opts)
}
// SharedConfigState provides the ability to optionally override the state
// of the session's creation based on the shared config being enabled or
// disabled.
type SharedConfigState int
const (
// SharedConfigStateFromEnv does not override any state of the
// AWS_SDK_LOAD_CONFIG env var. It is the default value of the
// SharedConfigState type.
SharedConfigStateFromEnv SharedConfigState = iota
// SharedConfigDisable overrides the AWS_SDK_LOAD_CONFIG env var value
// and disables the shared config functionality.
SharedConfigDisable
// SharedConfigEnable overrides the AWS_SDK_LOAD_CONFIG env var value
// and enables the shared config functionality.
SharedConfigEnable
)
// Options provides the means to control how a Session is created and what
// configuration values will be loaded.
//
type Options struct {
// Provides config values for the SDK to use when creating service clients
// and making API requests to services. Any value set in with this field
// will override the associated value provided by the SDK defaults,
// environment or config files where relevant.
//
// If not set, configuration values from from SDK defaults, environment,
// config will be used.
Config aws.Config
// Overrides the config profile the Session should be created from. If not
// set the value of the environment variable will be loaded (AWS_PROFILE,
// or AWS_DEFAULT_PROFILE if the Shared Config is enabled).
//
// If not set and environment variables are not set the "default"
// (DefaultSharedConfigProfile) will be used as the profile to load the
// session config from.
Profile string
// Instructs how the Session will be created based on the AWS_SDK_LOAD_CONFIG
// environment variable. By default a Session will be created using the
// value provided by the AWS_SDK_LOAD_CONFIG environment variable.
//
// Setting this value to SharedConfigEnable or SharedConfigDisable
// will allow you to override the AWS_SDK_LOAD_CONFIG environment variable
// and enable or disable the shared config functionality.
SharedConfigState SharedConfigState
// Ordered list of files the session will load configuration from.
// It will override environment variable AWS_SHARED_CREDENTIALS_FILE, AWS_CONFIG_FILE.
SharedConfigFiles []string
// When the SDK's shared config is configured to assume a role with MFA
// this option is required in order to provide the mechanism that will
// retrieve the MFA token. There is no default value for this field. If
// it is not set an error will be returned when creating the session.
//
// This token provider will be called when ever the assumed role's
// credentials need to be refreshed. Within the context of service clients
// all sharing the same session the SDK will ensure calls to the token
// provider are atomic. When sharing a token provider across multiple
// sessions additional synchronization logic is needed to ensure the
// token providers do not introduce race conditions. It is recommend to
// share the session where possible.
//
// stscreds.StdinTokenProvider is a basic implementation that will prompt
// from stdin for the MFA token code.
//
// This field is only used if the shared configuration is enabled, and
// the config enables assume role wit MFA via the mfa_serial field.
AssumeRoleTokenProvider func() (string, error)
// Reader for a custom Credentials Authority (CA) bundle in PEM format that
// the SDK will use instead of the default system's root CA bundle. Use this
// only if you want to replace the CA bundle the SDK uses for TLS requests.
//
// Enabling this option will attempt to merge the Transport into the SDK's HTTP
// client. If the client's Transport is not a http.Transport an error will be
// returned. If the Transport's TLS config is set this option will cause the SDK
// to overwrite the Transport's TLS config's RootCAs value. If the CA
// bundle reader contains multiple certificates all of them will be loaded.
//
// The Session option CustomCABundle is also available when creating sessions
// to also enable this feature. CustomCABundle session option field has priority
// over the AWS_CA_BUNDLE environment variable, and will be used if both are set.
CustomCABundle io.Reader
}
// NewSessionWithOptions returns a new Session created from SDK defaults, config files,
// environment, and user provided config files. This func uses the Options
// values to configure how the Session is created.
//
// If the AWS_SDK_LOAD_CONFIG environment variable is set to a truthy value
// the shared config file (~/.aws/config) will also be loaded in addition to
// the shared credentials file (~/.aws/credentials). Values set in both the
// shared config, and shared credentials will be taken from the shared
// credentials file. Enabling the Shared Config will also allow the Session
// to be built with retrieving credentials with AssumeRole set in the config.
//
// // Equivalent to session.New
// sess := session.Must(session.NewSessionWithOptions(session.Options{}))
//
// // Specify profile to load for the session's config
// sess := session.Must(session.NewSessionWithOptions(session.Options{
// Profile: "profile_name",
// }))
//
// // Specify profile for config and region for requests
// sess := session.Must(session.NewSessionWithOptions(session.Options{
// Config: aws.Config{Region: aws.String("us-east-1")},
// Profile: "profile_name",
// }))
//
// // Force enable Shared Config support
// sess := session.Must(session.NewSessionWithOptions(session.Options{
// SharedConfigState: session.SharedConfigEnable,
// }))
func NewSessionWithOptions(opts Options) (*Session, error) {
var envCfg envConfig
if opts.SharedConfigState == SharedConfigEnable {
envCfg = loadSharedEnvConfig()
} else {
envCfg = loadEnvConfig()
}
if len(opts.Profile) > 0 {
envCfg.Profile = opts.Profile
}
switch opts.SharedConfigState {
case SharedConfigDisable:
envCfg.EnableSharedConfig = false
case SharedConfigEnable:
envCfg.EnableSharedConfig = true
}
// Only use AWS_CA_BUNDLE if session option is not provided.
if len(envCfg.CustomCABundle) != 0 && opts.CustomCABundle == nil {
f, err := os.Open(envCfg.CustomCABundle)
if err != nil {
return nil, awserr.New("LoadCustomCABundleError",
"failed to open custom CA bundle PEM file", err)
}
defer f.Close()
opts.CustomCABundle = f
}
return newSession(opts, envCfg, &opts.Config)
}
// Must is a helper function to ensure the Session is valid and there was no
// error when calling a NewSession function.
//
// This helper is intended to be used in variable initialization to load the
// Session and configuration at startup. Such as:
//
// var sess = session.Must(session.NewSession())
func Must(sess *Session, err error) *Session {
if err != nil {
panic(err)
}
return sess
}
func deprecatedNewSession(cfgs ...*aws.Config) *Session {
cfg := defaults.Config()
handlers := defaults.Handlers()
// Apply the passed in configs so the configuration can be applied to the
// default credential chain
cfg.MergeIn(cfgs...)
if cfg.EndpointResolver == nil {
// An endpoint resolver is required for a session to be able to provide
// endpoints for service client configurations.
cfg.EndpointResolver = endpoints.DefaultResolver()
}
cfg.Credentials = defaults.CredChain(cfg, handlers)
// Reapply any passed in configs to override credentials if set
cfg.MergeIn(cfgs...)
s := &Session{
Config: cfg,
Handlers: handlers,
}
initHandlers(s)
return s
}
func newSession(opts Options, envCfg envConfig, cfgs ...*aws.Config) (*Session, error) {
cfg := defaults.Config()
handlers := defaults.Handlers()
// Get a merged version of the user provided config to determine if
// credentials were.
userCfg := &aws.Config{}
userCfg.MergeIn(cfgs...)
// Ordered config files will be loaded in with later files overwriting
// previous config file values.
var cfgFiles []string
if opts.SharedConfigFiles != nil {
cfgFiles = opts.SharedConfigFiles
} else {
cfgFiles = []string{envCfg.SharedConfigFile, envCfg.SharedCredentialsFile}
if !envCfg.EnableSharedConfig {
// The shared config file (~/.aws/config) is only loaded if instructed
// to load via the envConfig.EnableSharedConfig (AWS_SDK_LOAD_CONFIG).
cfgFiles = cfgFiles[1:]
}
}
// Load additional config from file(s)
sharedCfg, err := loadSharedConfig(envCfg.Profile, cfgFiles)
if err != nil {
return nil, err
}
if err := mergeConfigSrcs(cfg, userCfg, envCfg, sharedCfg, handlers, opts); err != nil {
return nil, err
}
s := &Session{
Config: cfg,
Handlers: handlers,
}
initHandlers(s)
// Setup HTTP client with custom cert bundle if enabled
if opts.CustomCABundle != nil {
if err := loadCustomCABundle(s, opts.CustomCABundle); err != nil {
return nil, err
}
}
return s, nil
}
func loadCustomCABundle(s *Session, bundle io.Reader) error {
var t *http.Transport
switch v := s.Config.HTTPClient.Transport.(type) {
case *http.Transport:
t = v
default:
if s.Config.HTTPClient.Transport != nil {
return awserr.New("LoadCustomCABundleError",
"unable to load custom CA bundle, HTTPClient's transport unsupported type", nil)
}
}
if t == nil {
t = &http.Transport{}
}
p, err := loadCertPool(bundle)
if err != nil {
return err
}
if t.TLSClientConfig == nil {
t.TLSClientConfig = &tls.Config{}
}
t.TLSClientConfig.RootCAs = p
s.Config.HTTPClient.Transport = t
return nil
}
func loadCertPool(r io.Reader) (*x509.CertPool, error) {
b, err := ioutil.ReadAll(r)
if err != nil {
return nil, awserr.New("LoadCustomCABundleError",
"failed to read custom CA bundle PEM file", err)
}
p := x509.NewCertPool()
if !p.AppendCertsFromPEM(b) {
return nil, awserr.New("LoadCustomCABundleError",
"failed to load custom CA bundle PEM file", err)
}
return p, nil
}
func mergeConfigSrcs(cfg, userCfg *aws.Config, envCfg envConfig, sharedCfg sharedConfig, handlers request.Handlers, sessOpts Options) error {
// Merge in user provided configuration
cfg.MergeIn(userCfg)
// Region if not already set by user
if len(aws.StringValue(cfg.Region)) == 0 {
if len(envCfg.Region) > 0 {
cfg.WithRegion(envCfg.Region)
} else if envCfg.EnableSharedConfig && len(sharedCfg.Region) > 0 {
cfg.WithRegion(sharedCfg.Region)
}
}
// Configure credentials if not already set
if cfg.Credentials == credentials.AnonymousCredentials && userCfg.Credentials == nil {
if len(envCfg.Creds.AccessKeyID) > 0 {
cfg.Credentials = credentials.NewStaticCredentialsFromCreds(
envCfg.Creds,
)
} else if envCfg.EnableSharedConfig && len(sharedCfg.AssumeRole.RoleARN) > 0 && sharedCfg.AssumeRoleSource != nil {
cfgCp := *cfg
cfgCp.Credentials = credentials.NewStaticCredentialsFromCreds(
sharedCfg.AssumeRoleSource.Creds,
)
if len(sharedCfg.AssumeRole.MFASerial) > 0 && sessOpts.AssumeRoleTokenProvider == nil {
// AssumeRole Token provider is required if doing Assume Role
// with MFA.
return AssumeRoleTokenProviderNotSetError{}
}
cfg.Credentials = stscreds.NewCredentials(
&Session{
Config: &cfgCp,
Handlers: handlers.Copy(),
},
sharedCfg.AssumeRole.RoleARN,
func(opt *stscreds.AssumeRoleProvider) {
opt.RoleSessionName = sharedCfg.AssumeRole.RoleSessionName
// Assume role with external ID
if len(sharedCfg.AssumeRole.ExternalID) > 0 {
opt.ExternalID = aws.String(sharedCfg.AssumeRole.ExternalID)
}
// Assume role with MFA
if len(sharedCfg.AssumeRole.MFASerial) > 0 {
opt.SerialNumber = aws.String(sharedCfg.AssumeRole.MFASerial)
opt.TokenProvider = sessOpts.AssumeRoleTokenProvider
}
},
)
} else if len(sharedCfg.Creds.AccessKeyID) > 0 {
cfg.Credentials = credentials.NewStaticCredentialsFromCreds(
sharedCfg.Creds,
)
} else {
// Fallback to default credentials provider, include mock errors
// for the credential chain so user can identify why credentials
// failed to be retrieved.
cfg.Credentials = credentials.NewCredentials(&credentials.ChainProvider{
VerboseErrors: aws.BoolValue(cfg.CredentialsChainVerboseErrors),
Providers: []credentials.Provider{
&credProviderError{Err: awserr.New("EnvAccessKeyNotFound", "failed to find credentials in the environment.", nil)},
&credProviderError{Err: awserr.New("SharedCredsLoad", fmt.Sprintf("failed to load profile, %s.", envCfg.Profile), nil)},
defaults.RemoteCredProvider(*cfg, handlers),
},
})
}
}
return nil
}
// AssumeRoleTokenProviderNotSetError is an error returned when creating a session when the
// MFAToken option is not set when shared config is configured load assume a
// role with an MFA token.
type AssumeRoleTokenProviderNotSetError struct{}
// Code is the short id of the error.
func (e AssumeRoleTokenProviderNotSetError) Code() string {
return "AssumeRoleTokenProviderNotSetError"
}
// Message is the description of the error
func (e AssumeRoleTokenProviderNotSetError) Message() string {
return fmt.Sprintf("assume role with MFA enabled, but AssumeRoleTokenProvider session option not set.")
}
// OrigErr is the underlying error that caused the failure.
func (e AssumeRoleTokenProviderNotSetError) OrigErr() error {
return nil
}
// Error satisfies the error interface.
func (e AssumeRoleTokenProviderNotSetError) Error() string {
return awserr.SprintError(e.Code(), e.Message(), "", nil)
}
type credProviderError struct {
Err error
}
var emptyCreds = credentials.Value{}
func (c credProviderError) Retrieve() (credentials.Value, error) {
return credentials.Value{}, c.Err
}
func (c credProviderError) IsExpired() bool {
return true
}
func initHandlers(s *Session) {
// Add the Validate parameter handler if it is not disabled.
s.Handlers.Validate.Remove(corehandlers.ValidateParametersHandler)
if !aws.BoolValue(s.Config.DisableParamValidation) {
s.Handlers.Validate.PushBackNamed(corehandlers.ValidateParametersHandler)
}
}
// Copy creates and returns a copy of the current Session, coping the config
// and handlers. If any additional configs are provided they will be merged
// on top of the Session's copied config.
//
// // Create a copy of the current Session, configured for the us-west-2 region.
// sess.Copy(&aws.Config{Region: aws.String("us-west-2")})
func (s *Session) Copy(cfgs ...*aws.Config) *Session {
newSession := &Session{
Config: s.Config.Copy(cfgs...),
Handlers: s.Handlers.Copy(),
}
initHandlers(newSession)
return newSession
}
// ClientConfig satisfies the client.ConfigProvider interface and is used to
// configure the service client instances. Passing the Session to the service
// client's constructor (New) will use this method to configure the client.
func (s *Session) ClientConfig(serviceName string, cfgs ...*aws.Config) client.Config {
// Backwards compatibility, the error will be eaten if user calls ClientConfig
// directly. All SDK services will use ClientconfigWithError.
cfg, _ := s.clientConfigWithErr(serviceName, cfgs...)
return cfg
}
func (s *Session) clientConfigWithErr(serviceName string, cfgs ...*aws.Config) (client.Config, error) {
s = s.Copy(cfgs...)
var resolved endpoints.ResolvedEndpoint
var err error
region := aws.StringValue(s.Config.Region)
if endpoint := aws.StringValue(s.Config.Endpoint); len(endpoint) != 0 {
resolved.URL = endpoints.AddScheme(endpoint, aws.BoolValue(s.Config.DisableSSL))
resolved.SigningRegion = region
} else {
resolved, err = s.Config.EndpointResolver.EndpointFor(
serviceName, region,
func(opt *endpoints.Options) {
opt.DisableSSL = aws.BoolValue(s.Config.DisableSSL)
opt.UseDualStack = aws.BoolValue(s.Config.UseDualStack)
// Support the condition where the service is modeled but its
// endpoint metadata is not available.
opt.ResolveUnknownService = true
},
)
}
return client.Config{
Config: s.Config,
Handlers: s.Handlers,
Endpoint: resolved.URL,
SigningRegion: resolved.SigningRegion,
SigningNameDerived: resolved.SigningNameDerived,
SigningName: resolved.SigningName,
}, err
}
// ClientConfigNoResolveEndpoint is the same as ClientConfig with the exception
// that the EndpointResolver will not be used to resolve the endpoint. The only
// endpoint set must come from the aws.Config.Endpoint field.
func (s *Session) ClientConfigNoResolveEndpoint(cfgs ...*aws.Config) client.Config {
s = s.Copy(cfgs...)
var resolved endpoints.ResolvedEndpoint
region := aws.StringValue(s.Config.Region)
if ep := aws.StringValue(s.Config.Endpoint); len(ep) > 0 {
resolved.URL = endpoints.AddScheme(ep, aws.BoolValue(s.Config.DisableSSL))
resolved.SigningRegion = region
}
return client.Config{
Config: s.Config,
Handlers: s.Handlers,
Endpoint: resolved.URL,
SigningRegion: resolved.SigningRegion,
SigningNameDerived: resolved.SigningNameDerived,
SigningName: resolved.SigningName,
}
}