VictoriaMetrics/lib/promscrape/discovery/ec2/api.go
Nikolay Khramchikhin 0069353d5e Add improvements to ec2_sd_discovery (#775)
* Add improvements to ec2 discovery

https://github.com/VictoriaMetrics/VictoriaMetrics/issues/771

 role_arn support with aws sts
 instance iam_role support
 refreshing temporary tokens

* Apply suggestions from code review

Co-authored-by: Roman Khavronenko <hagen1778@gmail.com>

* changed implementation, removed tests, clean up code

* moved endpoint builder into getEC2APIResponse

Co-authored-by: Roman Khavronenko <hagen1778@gmail.com>
2020-09-21 16:05:01 +03:00

365 lines
12 KiB
Go

package ec2
import (
"encoding/json"
"encoding/xml"
"fmt"
"io/ioutil"
"net/http"
"net/url"
"os"
"strings"
"sync/atomic"
"time"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/promscrape/discoveryutils"
)
const (
awsAccessKeyEnv = "AWS_ACCESS_KEY_ID"
awsSecretKeyEnv = "AWS_SECRET_ACCESS_KEY"
)
type apiConfig struct {
endpoint string
region string
roleARN string
filters string
port int
// this keys needed,
// when we are using temporary credentials
defaultAccessKey string
defaultSecretKey string
apiCredentials atomic.Value
}
// apiCredentials represents aws api credentials
type apiCredentials struct {
AccessKeyID string `json:"AccessKeyId"`
SecretAccessKey string `json:"SecretAccessKey"`
Token string `json:"Token"`
Expiration time.Time `json:"Expiration"`
}
// stsCredentialsResponse - represents aws sts AssumeRole response
// https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html
type stsCredentialsResponse struct {
AssumeRoleResult struct {
Credentials struct {
AccessKeyID string `xml:"AccessKeyId"`
SecretAccessKey string `xml:"SecretAccessKey"`
SessionToken string `xml:"SessionToken"`
Expiration time.Time `xml:"Expiration"`
}
}
}
var configMap = discoveryutils.NewConfigMap()
func getAPIConfig(sdc *SDConfig) (*apiConfig, error) {
v, err := configMap.Get(sdc, func() (interface{}, error) {
return newAPIConfig(sdc)
})
if err != nil {
return nil, err
}
return v.(*apiConfig), nil
}
func newAPIConfig(sdc *SDConfig) (*apiConfig, error) {
region := sdc.Region
if len(region) == 0 {
r, err := getDefaultRegion()
if err != nil {
return nil, fmt.Errorf("cannot determine default ec2 region; probably, `region` param in `ec2_sd_configs` is missing; the error: %w", err)
}
region = r
}
filters := getFiltersQueryString(sdc.Filters)
port := 80
if sdc.Port != nil {
port = *sdc.Port
}
cfg := &apiConfig{
endpoint: sdc.Endpoint,
region: region,
roleARN: sdc.RoleARN,
filters: filters,
port: port,
}
// explicitly set credentials has priority over env variables
cfg.defaultAccessKey = os.Getenv(awsAccessKeyEnv)
cfg.defaultSecretKey = os.Getenv(awsSecretKeyEnv)
if len(sdc.AccessKey) > 0 {
cfg.defaultAccessKey = sdc.AccessKey
}
if len(sdc.SecretKey) > 0 {
cfg.defaultSecretKey = sdc.SecretKey
}
// fast return if credentials are set and there is no roleARN
if len(cfg.defaultAccessKey) > 0 && len(cfg.defaultSecretKey) > 0 && len(sdc.RoleARN) == 0 {
cfg.apiCredentials.Store(&apiCredentials{
AccessKeyID: cfg.defaultAccessKey,
SecretAccessKey: cfg.defaultSecretKey,
})
return cfg, nil
}
if err := cfg.refreshAPICredentials(); err != nil {
return nil, err
}
return cfg, nil
}
func getFiltersQueryString(filters []Filter) string {
// See how to build filters query string at examples at https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstances.html
var args []string
for i, f := range filters {
args = append(args, fmt.Sprintf("Filter.%d.Name=%s", i+1, url.QueryEscape(f.Name)))
for j, v := range f.Values {
args = append(args, fmt.Sprintf("Filter.%d.Value.%d=%s", i+1, j+1, url.QueryEscape(v)))
}
}
return strings.Join(args, "&")
}
func getDefaultRegion() (string, error) {
data, err := getMetadataByPath("dynamic/instance-identity/document")
if err != nil {
return "", err
}
var id IdentityDocument
if err := json.Unmarshal(data, &id); err != nil {
return "", fmt.Errorf("cannot parse identity document: %w", err)
}
return id.Region, nil
}
// refreshAPICredentials updates expired tokens.
func (cfg *apiConfig) refreshAPICredentials() error {
newAPICredentials := &apiCredentials{
AccessKeyID: cfg.defaultAccessKey,
SecretAccessKey: cfg.defaultSecretKey,
}
// we need instance credentials
// if dont have key and secret
if len(newAPICredentials.AccessKeyID) == 0 && len(newAPICredentials.SecretAccessKey) == 0 {
ac, err := getInstanceRoleCredentials()
if err != nil {
return err
}
newAPICredentials.Token = ac.Token
newAPICredentials.SecretAccessKey = ac.SecretAccessKey
newAPICredentials.AccessKeyID = ac.AccessKeyID
newAPICredentials.Expiration = ac.Expiration
}
// read credentials from sts api, if role_arn is defined
if cfg.roleARN != "" {
ac, err := getRoleARNCredentials(cfg.region, cfg.endpoint, cfg.roleARN, newAPICredentials)
if err != nil {
return fmt.Errorf("cannot get credentials for role_arn: %s: %w", cfg.roleARN, err)
}
if newAPICredentials.Expiration.IsZero() || ac.Expiration.Before(newAPICredentials.Expiration) {
newAPICredentials.Expiration = ac.Expiration
}
newAPICredentials.AccessKeyID = ac.AccessKeyID
newAPICredentials.SecretAccessKey = ac.SecretAccessKey
newAPICredentials.Token = ac.Token
}
if len(newAPICredentials.AccessKeyID) == 0 {
return fmt.Errorf("missing `access_key`, you can set it with %s env var, "+
"directly at `ec2_sd_config` as `access_key` or use instance iam role", awsAccessKeyEnv)
}
if len(newAPICredentials.SecretAccessKey) == 0 {
return fmt.Errorf("missing `secret_key`, you can set it with %s env var,"+
"directly at `ec2_sd_config` as `secret_key` or use instance iam role", awsSecretKeyEnv)
}
cfg.apiCredentials.Store(newAPICredentials)
return nil
}
// credentialsExpired - checks if tokens refresh is needed
func (cfg *apiConfig) credentialsExpired() bool {
ac := cfg.credentials()
return !ac.Expiration.IsZero() && time.Since(ac.Expiration) > -5*time.Second
}
// credentials - returns current api credentials
func (cfg *apiConfig) credentials() *apiCredentials {
return cfg.apiCredentials.Load().(*apiCredentials)
}
// getInstanceRoleCredentials makes request to local ec2 instance metadata service
// and tries to retrieve credentials from assigned iam role.
// https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html
func getInstanceRoleCredentials() (*apiCredentials, error) {
instanceRoleName, err := getMetadataByPath("meta-data/iam/security-credentials/")
if err != nil {
return nil, fmt.Errorf("cannot get instanceRoleName: %w", err)
}
credentials, err := getMetadataByPath("meta-data/iam/security-credentials/" + string(instanceRoleName))
if err != nil {
return nil, fmt.Errorf("cannot get instanceCredentials with role %s, error: %w", instanceRoleName, err)
}
ac := &apiCredentials{}
if err := json.Unmarshal(credentials, ac); err != nil {
return nil, fmt.Errorf("cannot parse instance metadata role response : %w", err)
}
return ac, nil
}
// IdentityDocument is identity document returned from AWS metadata server.
//
// See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-identity-documents.html
type IdentityDocument struct {
Region string
}
// getMetadataByPath returns instance metadata by url path
func getMetadataByPath(apiPath string) ([]byte, error) {
// See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html
// Obtain session token
sessionTokenURL := "http://169.254.169.254/latest/api/token"
req, err := http.NewRequest("PUT", sessionTokenURL, nil)
if err != nil {
return nil, fmt.Errorf("cannot create request for IMDSv2 session token at url %q: %w", sessionTokenURL, err)
}
req.Header.Set("X-aws-ec2-metadata-token-ttl-seconds", "60")
resp, err := discoveryutils.GetHTTPClient().Do(req)
if err != nil {
return nil, fmt.Errorf("cannot obtain IMDSv2 session token from %q; probably, `region` is missing in `ec2_sd_config`; error: %w", sessionTokenURL, err)
}
token, err := readResponseBody(resp, sessionTokenURL)
if err != nil {
return nil, fmt.Errorf("cannot read IMDSv2 session token from %q; probably, `region` is missing in `ec2_sd_config`; error: %w", sessionTokenURL, err)
}
// Use session token in the request.
apiURL := "http://169.254.169.254/latest/" + apiPath
req, err = http.NewRequest("GET", apiURL, nil)
if err != nil {
return nil, fmt.Errorf("cannot create request to %q: %w", apiURL, err)
}
req.Header.Set("X-aws-ec2-metadata-token", string(token))
resp, err = discoveryutils.GetHTTPClient().Do(req)
if err != nil {
return nil, fmt.Errorf("cannot obtain response for %q: %w", apiURL, err)
}
return readResponseBody(resp, apiURL)
}
// getRoleARNCredentials - retrieves credentials from aws sts with role_arn
func getRoleARNCredentials(region, endpoint, roleARN string, credentials *apiCredentials) (*apiCredentials, error) {
data, err := getSTSAPIResponse(region, endpoint, roleARN, credentials)
if err != nil {
return nil, err
}
scr := &stsCredentialsResponse{}
if err := xml.Unmarshal(data, scr); err != nil {
return nil, fmt.Errorf("cannot parse sts api response: %w", err)
}
return &apiCredentials{
AccessKeyID: scr.AssumeRoleResult.Credentials.AccessKeyID,
SecretAccessKey: scr.AssumeRoleResult.Credentials.SecretAccessKey,
Token: scr.AssumeRoleResult.Credentials.SessionToken,
Expiration: scr.AssumeRoleResult.Credentials.Expiration,
}, nil
}
// buildAPIEndpoint - creates endpoint for aws api access
func buildAPIEndpoint(region, cfgEndpoint, service string) string {
// See https://docs.aws.amazon.com/AWSEC2/latest/APIReference/Query-Requests.html
apiEndpoint := fmt.Sprintf("https://%s.%s.amazonaws.com/", service, region)
if len(cfgEndpoint) > 0 {
apiEndpoint = cfgEndpoint
// endpoint may contain only hostname. Convert it to proper url then.
if !strings.Contains(apiEndpoint, "://") {
apiEndpoint = "https://" + apiEndpoint
}
if !strings.HasSuffix(apiEndpoint, "/") {
apiEndpoint += "/"
}
}
return apiEndpoint
}
// getSTSAPIResponse makes request to aws sts api with role_arn
// and returns temporary credentials with expiration time
// https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html
func getSTSAPIResponse(region, endpoint, roleARN string, credentials *apiCredentials) ([]byte, error) {
endpoint = buildAPIEndpoint(region, endpoint, "sts")
// See https://docs.aws.amazon.com/AWSEC2/latest/APIReference/Query-Requests.html
apiURL := fmt.Sprintf("%s?Action=%s", endpoint, "AssumeRole")
apiURL += "&Version=2011-06-15"
apiURL += fmt.Sprintf("&RoleArn=%s", roleARN)
// we have to provide unique session name for cloudtrail audit
apiURL += "&RoleSessionName=vmagent-ec2-discovery"
req, err := newSignedRequest(apiURL, "sts", region, credentials)
if err != nil {
return nil, fmt.Errorf("cannot create signed request: %w", err)
}
resp, err := discoveryutils.GetHTTPClient().Do(req)
if err != nil {
return nil, fmt.Errorf("cannot perform http request to %q: %w", apiURL, err)
}
return readResponseBody(resp, apiURL)
}
// getEC2APIResponse lists ec2 instances with given action
func getEC2APIResponse(cfg *apiConfig, action, nextPageToken string) ([]byte, error) {
endpoint := buildAPIEndpoint(cfg.region, cfg.endpoint, "ec2")
// refresh api credentials if needed
if cfg.credentialsExpired() {
if err := cfg.refreshAPICredentials(); err != nil {
return nil, fmt.Errorf("failed to update expired aws credentials: %w", err)
}
}
apiURL := fmt.Sprintf("%s?Action=%s", endpoint, url.QueryEscape(action))
if len(cfg.filters) > 0 {
apiURL += "&" + cfg.filters
}
if len(nextPageToken) > 0 {
apiURL += fmt.Sprintf("&NextToken=%s", url.QueryEscape(nextPageToken))
}
apiURL += "&Version=2013-10-15"
req, err := newSignedRequest(apiURL, "ec2", cfg.region, cfg.credentials())
if err != nil {
return nil, fmt.Errorf("cannot create signed request: %w", err)
}
resp, err := discoveryutils.GetHTTPClient().Do(req)
if err != nil {
return nil, fmt.Errorf("cannot perform http request to %q: %w", apiURL, err)
}
return readResponseBody(resp, apiURL)
}
func readResponseBody(resp *http.Response, apiURL string) ([]byte, error) {
data, err := ioutil.ReadAll(resp.Body)
_ = resp.Body.Close()
if err != nil {
return nil, fmt.Errorf("cannot read response from %q: %w", apiURL, err)
}
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("unexpected status code for %q; got %d; want %d; response body: %q",
apiURL, resp.StatusCode, http.StatusOK, data)
}
return data, nil
}