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// Package endpointcreds provides support for retrieving credentials from an
// arbitrary HTTP endpoint.
//
// The credentials endpoint Provider can receive both static and refreshable
// credentials that will expire. Credentials are static when an "Expiration"
// value is not provided in the endpoint's response.
//
// Static credentials will never expire once they have been retrieved. The format
// of the static credentials response:
// {
// "AccessKeyId" : "MUA...",
// "SecretAccessKey" : "/7PC5om....",
// }
//
// Refreshable credentials will expire within the "ExpiryWindow" of the Expiration
// value in the response. The format of the refreshable credentials response:
// {
// "AccessKeyId" : "MUA...",
// "SecretAccessKey" : "/7PC5om....",
// "Token" : "AQoDY....=",
// "Expiration" : "2016-02-25T06:03:31Z"
// }
//
// Errors should be returned in the following format and only returned with 400
// or 500 HTTP status codes.
// {
// "code": "ErrorCode",
// "message": "Helpful error message."
// }
package endpointcreds
import (
"encoding/json"
"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/credentials"
"github.com/aws/aws-sdk-go/aws/request"
)
// ProviderName is the name of the credentials provider.
const ProviderName = `CredentialsEndpointProvider`
// Provider satisfies the credentials.Provider interface, and is a client to
// retrieve credentials from an arbitrary endpoint.
type Provider struct {
staticCreds bool
credentials.Expiry
// Requires a AWS Client to make HTTP requests to the endpoint with.
// the Endpoint the request will be made to is provided by the aws.Config's
// Endpoint value.
Client *client.Client
// ExpiryWindow will allow the credentials to trigger refreshing prior to
// the credentials actually expiring. This is beneficial so race conditions
// with expiring credentials do not cause request to fail unexpectedly
// due to ExpiredTokenException exceptions.
//
// So a ExpiryWindow of 10s would cause calls to IsExpired() to return true
// 10 seconds before the credentials are actually expired.
//
// If ExpiryWindow is 0 or less it will be ignored.
ExpiryWindow time.Duration
}
// NewProviderClient returns a credentials Provider for retrieving AWS credentials
// from arbitrary endpoint.
func NewProviderClient(cfg aws.Config, handlers request.Handlers, endpoint string, options ...func(*Provider)) credentials.Provider {
p := &Provider{
Client: client.New(
cfg,
metadata.ClientInfo{
ServiceName: "CredentialsEndpoint",
Endpoint: endpoint,
},
handlers,
),
}
p.Client.Handlers.Unmarshal.PushBack(unmarshalHandler)
p.Client.Handlers.UnmarshalError.PushBack(unmarshalError)
p.Client.Handlers.Validate.Clear()
p.Client.Handlers.Validate.PushBack(validateEndpointHandler)
for _, option := range options {
option(p)
}
return p
}
// NewCredentialsClient returns a Credentials wrapper for retrieving credentials
// from an arbitrary endpoint concurrently. The client will request the
func NewCredentialsClient(cfg aws.Config, handlers request.Handlers, endpoint string, options ...func(*Provider)) *credentials.Credentials {
return credentials.NewCredentials(NewProviderClient(cfg, handlers, endpoint, options...))
}
// IsExpired returns true if the credentials retrieved are expired, or not yet
// retrieved.
func (p *Provider) IsExpired() bool {
if p.staticCreds {
return false
}
return p.Expiry.IsExpired()
}
// Retrieve will attempt to request the credentials from the endpoint the Provider
// was configured for. And error will be returned if the retrieval fails.
func (p *Provider) Retrieve() (credentials.Value, error) {
resp, err := p.getCredentials()
if err != nil {
return credentials.Value{ProviderName: ProviderName},
awserr.New("CredentialsEndpointError", "failed to load credentials", err)
}
if resp.Expiration != nil {
p.SetExpiration(*resp.Expiration, p.ExpiryWindow)
} else {
p.staticCreds = true
}
return credentials.Value{
AccessKeyID: resp.AccessKeyID,
SecretAccessKey: resp.SecretAccessKey,
SessionToken: resp.Token,
ProviderName: ProviderName,
}, nil
}
type getCredentialsOutput struct {
Expiration *time.Time
AccessKeyID string
SecretAccessKey string
Token string
}
type errorOutput struct {
Code string `json:"code"`
Message string `json:"message"`
}
func (p *Provider) getCredentials() (*getCredentialsOutput, error) {
op := &request.Operation{
Name: "GetCredentials",
HTTPMethod: "GET",
}
out := &getCredentialsOutput{}
req := p.Client.NewRequest(op, nil, out)
req.HTTPRequest.Header.Set("Accept", "application/json")
return out, req.Send()
}
func validateEndpointHandler(r *request.Request) {
if len(r.ClientInfo.Endpoint) == 0 {
r.Error = aws.ErrMissingEndpoint
}
}
func unmarshalHandler(r *request.Request) {
defer r.HTTPResponse.Body.Close()
out := r.Data.(*getCredentialsOutput)
if err := json.NewDecoder(r.HTTPResponse.Body).Decode(&out); err != nil {
r.Error = awserr.New("SerializationError",
"failed to decode endpoint credentials",
err,
)
}
}
func unmarshalError(r *request.Request) {
defer r.HTTPResponse.Body.Close()
var errOut errorOutput
if err := json.NewDecoder(r.HTTPResponse.Body).Decode(&errOut); err != nil {
r.Error = awserr.New("SerializationError",
"failed to decode endpoint credentials",
err,
)
}
// 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(errOut.Code, errOut.Message, nil)
}
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