repo_description: The Official Golang driver for MongoDB
repo_topics: database driver go golang golang-library mongodb
code: // Copyright (C) MongoDB, Inc. 2023-present.
  //
  // Licensed under the Apache License, Version 2.0 (the "License"); you may
  // not use this file except in compliance with the License. You may obtain
  // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
  
  package credproviders
  
  import (
  	"context"
  	"encoding/json"
  	"errors"
  	"fmt"
  	"io/ioutil"
  	"net/http"
  	"time"
  
  	"go.mongodb.org/mongo-driver/v2/internal/aws/credentials"
  )
  
  const (
  	// ec2ProviderName provides a name of EC2 provider
  	ec2ProviderName = "EC2Provider"
  
  	awsEC2URI       = "http://169.254.169.254/"
  	awsEC2RolePath  = "latest/meta-data/iam/security-credentials/"
  	awsEC2TokenPath = "latest/api/token"
  
  	defaultHTTPTimeout = 10 * time.Second
  )
  
  // An EC2Provider retrieves credentials from EC2 metadata.
  type EC2Provider struct {
  	httpClient *http.Client
  	expiration time.Time
  
  	// expiryWindow will allow the credentials to trigger refreshing prior to the credentials actually expiring.
  	// This is beneficial so expiring credentials do not cause request to fail unexpectedly due to exceptions.
  	//
  	// So a ExpiryWindow of 10s would cause calls to IsExpired() to return true
  	// 10 seconds before the credentials are actually expired.
  	expiryWindow time.Duration
  }
  
  // NewEC2Provider returns a pointer to an EC2 credential provider.
  func NewEC2Provider(httpClient *http.Client, expiryWindow time.Duration) *EC2Provider {
  	return &EC2Provider{
  		httpClient:   httpClient,
  		expiryWindow: expiryWindow,
  	}
  }
  
  func (e *EC2Provider) getToken(ctx context.Context) (string, error) {
  	req, err := http.NewRequest(http.MethodPut, awsEC2URI+awsEC2TokenPath, nil)
  	if err != nil {
  		return "", err
  	}
  	const defaultEC2TTLSeconds = "30"
  	req.Header.Set("X-aws-ec2-metadata-token-ttl-seconds", defaultEC2TTLSeconds)
  
  	ctx, cancel := context.WithTimeout(ctx, defaultHTTPTimeout)
  	defer cancel()
  	resp, err := e.httpClient.Do(req.WithContext(ctx))
  	if err != nil {
  		return "", err
  	}
  	defer resp.Body.Close()
  	if resp.StatusCode != http.StatusOK {
  		return "", fmt.Errorf("%s %s failed: %s", req.Method, req.URL.String(), resp.Status)
  	}
  
  	token, err := ioutil.ReadAll(resp.Body)
  	if err != nil {
  		return "", err
  	}
  	if len(token) == 0 {
  		return "", errors.New("unable to retrieve token from EC2 metadata")
  	}
  	return string(token), nil
  }
  
  func (e *EC2Provider) getRoleName(ctx context.Context, token string) (string, error) {
  	req, err := http.NewRequest(http.MethodGet, awsEC2URI+awsEC2RolePath, nil)
  	if err != nil {
  		return "", err
  	}
  	req.Header.Set("X-aws-ec2-metadata-token", token)
  
  	ctx, cancel := context.WithTimeout(ctx, defaultHTTPTimeout)
  	defer cancel()
  	resp, err := e.httpClient.Do(req.WithContext(ctx))
  	if err != nil {
  		return "", err
  	}
  	defer resp.Body.Close()
  	if resp.StatusCode != http.StatusOK {
  		return "", fmt.Errorf("%s %s failed: %s", req.Method, req.URL.String(), resp.Status)
  	}
  
  	role, err := ioutil.ReadAll(resp.Body)
  	if err != nil {
  		return "", err
  	}
  	if len(role) == 0 {
  		return "", errors.New("unable to retrieve role_name from EC2 metadata")
  	}
  	return string(role), nil
  }
  
  func (e *EC2Provider) getCredentials(ctx context.Context, token string, role string) (credentials.Value, time.Time, error) {
  	v := credentials.Value{ProviderName: ec2ProviderName}
  
  	pathWithRole := awsEC2URI + awsEC2RolePath + role
  	req, err := http.NewRequest(http.MethodGet, pathWithRole, nil)
  	if err != nil {
  		return v, time.Time{}, err
  	}
  	req.Header.Set("X-aws-ec2-metadata-token", token)
  	ctx, cancel := context.WithTimeout(ctx, defaultHTTPTimeout)
  	defer cancel()
  	resp, err := e.httpClient.Do(req.WithContext(ctx))
  	if err != nil {
  		return v, time.Time{}, err
  	}
  	defer resp.Body.Close()
  	if resp.StatusCode != http.StatusOK {
  		return v, time.Time{}, fmt.Errorf("%s %s failed: %s", req.Method, req.URL.String(), resp.Status)
  	}
  
  	var ec2Resp struct {
  		AccessKeyID     string    `json:"AccessKeyId"`
  		SecretAccessKey string    `json:"SecretAccessKey"`
  		Token           string    `json:"Token"`
  		Expiration      time.Time `json:"Expiration"`
  	}
  
  	err = json.NewDecoder(resp.Body).Decode(&ec2Resp)
  	if err != nil {
  		return v, time.Time{}, err
  	}
  
  	v.AccessKeyID = ec2Resp.AccessKeyID
  	v.SecretAccessKey = ec2Resp.SecretAccessKey
  	v.SessionToken = ec2Resp.Token
  
  	return v, ec2Resp.Expiration, nil
  }
  
  // RetrieveWithContext retrieves the keys from the AWS service.
  func (e *EC2Provider) RetrieveWithContext(ctx context.Context) (credentials.Value, error) {
  	v := credentials.Value{ProviderName: ec2ProviderName}
  
  	token, err := e.getToken(ctx)
  	if err != nil {
  		return v, err
  	}
  
  	role, err := e.getRoleName(ctx, token)
  	if err != nil {
  		return v, err
  	}
  
  	v, exp, err := e.getCredentials(ctx, token, role)
  	if err != nil {
  		return v, err
  	}
  	if !v.HasKeys() {
  		return v, errors.New("failed to retrieve EC2 keys")
  	}
  	e.expiration = exp.Add(-e.expiryWindow)
  
  	return v, nil
  }
  
  // Retrieve retrieves the keys from the AWS service.
  func (e *EC2Provider) Retrieve() (credentials.Value, error) {
  	return e.RetrieveWithContext(context.Background())
  }
  
  // IsExpired returns true if the credentials are expired.
  func (e *EC2Provider) IsExpired() bool {
  	return e.expiration.Before(time.Now())
  }
  