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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package acme
import (
"bytes"
"context"
"crypto"
"crypto/rand"
"encoding/json"
"errors"
"fmt"
"io"
"math/big"
"net/http"
"strconv"
"strings"
"time"
)
// retryTimer encapsulates common logic for retrying unsuccessful requests.
// It is not safe for concurrent use.
type retryTimer struct {
// backoffFn provides backoff delay sequence for retries.
// See Client.RetryBackoff doc comment.
backoffFn func(n int, r *http.Request, res *http.Response) time.Duration
// n is the current retry attempt.
n int
}
func (t *retryTimer) inc() {
t.n++
}
// backoff pauses the current goroutine as described in Client.RetryBackoff.
func (t *retryTimer) backoff(ctx context.Context, r *http.Request, res *http.Response) error {
d := t.backoffFn(t.n, r, res)
if d <= 0 {
return fmt.Errorf("acme: no more retries for %s; tried %d time(s)", r.URL, t.n)
}
wakeup := time.NewTimer(d)
defer wakeup.Stop()
select {
case <-ctx.Done():
return ctx.Err()
case <-wakeup.C:
return nil
}
}
func (c *Client) retryTimer() *retryTimer {
f := c.RetryBackoff
if f == nil {
f = defaultBackoff
}
return &retryTimer{backoffFn: f}
}
// defaultBackoff provides default Client.RetryBackoff implementation
// using a truncated exponential backoff algorithm,
// as described in Client.RetryBackoff.
//
// The n argument is always bounded between 1 and 30.
// The returned value is always greater than 0.
func defaultBackoff(n int, r *http.Request, res *http.Response) time.Duration {
const max = 10 * time.Second
var jitter time.Duration
if x, err := rand.Int(rand.Reader, big.NewInt(1000)); err == nil {
// Set the minimum to 1ms to avoid a case where
// an invalid Retry-After value is parsed into 0 below,
// resulting in the 0 returned value which would unintentionally
// stop the retries.
jitter = (1 + time.Duration(x.Int64())) * time.Millisecond
}
if v, ok := res.Header["Retry-After"]; ok {
return retryAfter(v[0]) + jitter
}
if n < 1 {
n = 1
}
if n > 30 {
n = 30
}
d := time.Duration(1< max {
return max
}
return d
}
// retryAfter parses a Retry-After HTTP header value,
// trying to convert v into an int (seconds) or use http.ParseTime otherwise.
// It returns zero value if v cannot be parsed.
func retryAfter(v string) time.Duration {
if i, err := strconv.Atoi(v); err == nil {
return time.Duration(i) * time.Second
}
t, err := http.ParseTime(v)
if err != nil {
return 0
}
return t.Sub(timeNow())
}
// resOkay is a function that reports whether the provided response is okay.
// It is expected to keep the response body unread.
type resOkay func(*http.Response) bool
// wantStatus returns a function which reports whether the code
// matches the status code of a response.
func wantStatus(codes ...int) resOkay {
return func(res *http.Response) bool {
for _, code := range codes {
if code == res.StatusCode {
return true
}
}
return false
}
}
// get issues an unsigned GET request to the specified URL.
// It returns a non-error value only when ok reports true.
//
// get retries unsuccessful attempts according to c.RetryBackoff
// until the context is done or a non-retriable error is received.
func (c *Client) get(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
retry := c.retryTimer()
for {
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
res, err := c.doNoRetry(ctx, req)
switch {
case err != nil:
return nil, err
case ok(res):
return res, nil
case isRetriable(res.StatusCode):
retry.inc()
resErr := responseError(res)
res.Body.Close()
// Ignore the error value from retry.backoff
// and return the one from last retry, as received from the CA.
if retry.backoff(ctx, req, res) != nil {
return nil, resErr
}
default:
defer res.Body.Close()
return nil, responseError(res)
}
}
}
// postAsGet is POST-as-GET, a replacement for GET in RFC 8555
// as described in https://tools.ietf.org/html/rfc8555#section-6.3.
// It makes a POST request in KID form with zero JWS payload.
// See nopayload doc comments in jws.go.
func (c *Client) postAsGet(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
return c.post(ctx, nil, url, noPayload, ok)
}
// post issues a signed POST request in JWS format using the provided key
// to the specified URL. If key is nil, c.Key is used instead.
// It returns a non-error value only when ok reports true.
//
// post retries unsuccessful attempts according to c.RetryBackoff
// until the context is done or a non-retriable error is received.
// It uses postNoRetry to make individual requests.
func (c *Client) post(ctx context.Context, key crypto.Signer, url string, body interface{}, ok resOkay) (*http.Response, error) {
retry := c.retryTimer()
for {
res, req, err := c.postNoRetry(ctx, key, url, body)
if err != nil {
return nil, err
}
if ok(res) {
return res, nil
}
resErr := responseError(res)
res.Body.Close()
switch {
// Check for bad nonce before isRetriable because it may have been returned
// with an unretriable response code such as 400 Bad Request.
case isBadNonce(resErr):
// Consider any previously stored nonce values to be invalid.
c.clearNonces()
case !isRetriable(res.StatusCode):
return nil, resErr
}
retry.inc()
// Ignore the error value from retry.backoff
// and return the one from last retry, as received from the CA.
if err := retry.backoff(ctx, req, res); err != nil {
return nil, resErr
}
}
}
// postNoRetry signs the body with the given key and POSTs it to the provided url.
// It is used by c.post to retry unsuccessful attempts.
// The body argument must be JSON-serializable.
//
// If key argument is nil, c.Key is used to sign the request.
// If key argument is nil and c.accountKID returns a non-zero keyID,
// the request is sent in KID form. Otherwise, JWK form is used.
//
// In practice, when interfacing with RFC-compliant CAs most requests are sent in KID form
// and JWK is used only when KID is unavailable: new account endpoint and certificate
// revocation requests authenticated by a cert key.
// See jwsEncodeJSON for other details.
func (c *Client) postNoRetry(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, *http.Request, error) {
kid := noKeyID
if key == nil {
if c.Key == nil {
return nil, nil, errors.New("acme: Client.Key must be populated to make POST requests")
}
key = c.Key
kid = c.accountKID(ctx)
}
nonce, err := c.popNonce(ctx, url)
if err != nil {
return nil, nil, err
}
b, err := jwsEncodeJSON(body, key, kid, nonce, url)
if err != nil {
return nil, nil, err
}
req, err := http.NewRequest("POST", url, bytes.NewReader(b))
if err != nil {
return nil, nil, err
}
req.Header.Set("Content-Type", "application/jose+json")
res, err := c.doNoRetry(ctx, req)
if err != nil {
return nil, nil, err
}
c.addNonce(res.Header)
return res, req, nil
}
// doNoRetry issues a request req, replacing its context (if any) with ctx.
func (c *Client) doNoRetry(ctx context.Context, req *http.Request) (*http.Response, error) {
req.Header.Set("User-Agent", c.userAgent())
res, err := c.httpClient().Do(req.WithContext(ctx))
if err != nil {
select {
case <-ctx.Done():
// Prefer the unadorned context error.
// (The acme package had tests assuming this, previously from ctxhttp's
// behavior, predating net/http supporting contexts natively)
// TODO(bradfitz): reconsider this in the future. But for now this
// requires no test updates.
return nil, ctx.Err()
default:
return nil, err
}
}
return res, nil
}
func (c *Client) httpClient() *http.Client {
if c.HTTPClient != nil {
return c.HTTPClient
}
return http.DefaultClient
}
// packageVersion is the version of the module that contains this package, for
// sending as part of the User-Agent header. It's set in version_go112.go.
var packageVersion string
// userAgent returns the User-Agent header value. It includes the package name,
// the module version (if available), and the c.UserAgent value (if set).
func (c *Client) userAgent() string {
ua := "golang.org/x/crypto/acme"
if packageVersion != "" {
ua += "@" + packageVersion
}
if c.UserAgent != "" {
ua = c.UserAgent + " " + ua
}
return ua
}
// isBadNonce reports whether err is an ACME "badnonce" error.
func isBadNonce(err error) bool {
// According to the spec badNonce is urn:ietf:params:acme:error:badNonce.
// However, ACME servers in the wild return their versions of the error.
// See https://tools.ietf.org/html/draft-ietf-acme-acme-02#section-5.4
// and https://github.com/letsencrypt/boulder/blob/0e07eacb/docs/acme-divergences.md#section-66.
ae, ok := err.(*Error)
return ok && strings.HasSuffix(strings.ToLower(ae.ProblemType), ":badnonce")
}
// isRetriable reports whether a request can be retried
// based on the response status code.
//
// Note that a "bad nonce" error is returned with a non-retriable 400 Bad Request code.
// Callers should parse the response and check with isBadNonce.
func isRetriable(code int) bool {
return code <= 399 || code >= 500 || code == http.StatusTooManyRequests
}
// responseError creates an error of Error type from resp.
func responseError(resp *http.Response) error {
// don't care if ReadAll returns an error:
// json.Unmarshal will fail in that case anyway
b, _ := io.ReadAll(resp.Body)
e := &wireError{Status: resp.StatusCode}
if err := json.Unmarshal(b, e); err != nil {
// this is not a regular error response:
// populate detail with anything we received,
// e.Status will already contain HTTP response code value
e.Detail = string(b)
if e.Detail == "" {
e.Detail = resp.Status
}
}
return e.error(resp.Header)
}