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321 lines
9.6 KiB
Go
Vendored
321 lines
9.6 KiB
Go
Vendored
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package acme
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import (
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"bytes"
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"context"
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"crypto"
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"crypto/rand"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"math/big"
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"net/http"
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"strconv"
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"strings"
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"time"
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)
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// retryTimer encapsulates common logic for retrying unsuccessful requests.
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// It is not safe for concurrent use.
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type retryTimer struct {
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// backoffFn provides backoff delay sequence for retries.
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// See Client.RetryBackoff doc comment.
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backoffFn func(n int, r *http.Request, res *http.Response) time.Duration
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// n is the current retry attempt.
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n int
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}
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func (t *retryTimer) inc() {
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t.n++
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}
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// backoff pauses the current goroutine as described in Client.RetryBackoff.
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func (t *retryTimer) backoff(ctx context.Context, r *http.Request, res *http.Response) error {
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d := t.backoffFn(t.n, r, res)
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if d <= 0 {
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return fmt.Errorf("acme: no more retries for %s; tried %d time(s)", r.URL, t.n)
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}
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wakeup := time.NewTimer(d)
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defer wakeup.Stop()
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select {
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case <-ctx.Done():
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return ctx.Err()
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case <-wakeup.C:
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return nil
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}
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}
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func (c *Client) retryTimer() *retryTimer {
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f := c.RetryBackoff
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if f == nil {
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f = defaultBackoff
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}
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return &retryTimer{backoffFn: f}
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}
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// defaultBackoff provides default Client.RetryBackoff implementation
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// using a truncated exponential backoff algorithm,
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// as described in Client.RetryBackoff.
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//
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// The n argument is always bounded between 1 and 30.
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// The returned value is always greater than 0.
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func defaultBackoff(n int, r *http.Request, res *http.Response) time.Duration {
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const max = 10 * time.Second
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var jitter time.Duration
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if x, err := rand.Int(rand.Reader, big.NewInt(1000)); err == nil {
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// Set the minimum to 1ms to avoid a case where
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// an invalid Retry-After value is parsed into 0 below,
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// resulting in the 0 returned value which would unintentionally
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// stop the retries.
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jitter = (1 + time.Duration(x.Int64())) * time.Millisecond
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}
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if v, ok := res.Header["Retry-After"]; ok {
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return retryAfter(v[0]) + jitter
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}
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if n < 1 {
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n = 1
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}
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if n > 30 {
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n = 30
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}
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d := time.Duration(1<<uint(n-1))*time.Second + jitter
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if d > max {
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return max
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}
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return d
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}
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// retryAfter parses a Retry-After HTTP header value,
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// trying to convert v into an int (seconds) or use http.ParseTime otherwise.
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// It returns zero value if v cannot be parsed.
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func retryAfter(v string) time.Duration {
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if i, err := strconv.Atoi(v); err == nil {
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return time.Duration(i) * time.Second
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}
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t, err := http.ParseTime(v)
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if err != nil {
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return 0
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}
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return t.Sub(timeNow())
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}
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// resOkay is a function that reports whether the provided response is okay.
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// It is expected to keep the response body unread.
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type resOkay func(*http.Response) bool
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// wantStatus returns a function which reports whether the code
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// matches the status code of a response.
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func wantStatus(codes ...int) resOkay {
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return func(res *http.Response) bool {
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for _, code := range codes {
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if code == res.StatusCode {
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return true
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}
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}
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return false
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}
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}
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// get issues an unsigned GET request to the specified URL.
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// It returns a non-error value only when ok reports true.
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//
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// get retries unsuccessful attempts according to c.RetryBackoff
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// until the context is done or a non-retriable error is received.
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func (c *Client) get(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
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retry := c.retryTimer()
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for {
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req, err := http.NewRequest("GET", url, nil)
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if err != nil {
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return nil, err
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}
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res, err := c.doNoRetry(ctx, req)
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switch {
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case err != nil:
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return nil, err
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case ok(res):
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return res, nil
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case isRetriable(res.StatusCode):
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retry.inc()
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resErr := responseError(res)
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res.Body.Close()
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// Ignore the error value from retry.backoff
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// and return the one from last retry, as received from the CA.
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if retry.backoff(ctx, req, res) != nil {
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return nil, resErr
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}
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default:
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defer res.Body.Close()
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return nil, responseError(res)
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}
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}
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}
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// postAsGet is POST-as-GET, a replacement for GET in RFC8555
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// as described in https://tools.ietf.org/html/rfc8555#section-6.3.
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// It makes a POST request in KID form with zero JWS payload.
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// See nopayload doc comments in jws.go.
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func (c *Client) postAsGet(ctx context.Context, url string, ok resOkay) (*http.Response, error) {
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return c.post(ctx, nil, url, noPayload, ok)
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}
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// post issues a signed POST request in JWS format using the provided key
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// to the specified URL. If key is nil, c.Key is used instead.
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// It returns a non-error value only when ok reports true.
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//
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// post retries unsuccessful attempts according to c.RetryBackoff
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// until the context is done or a non-retriable error is received.
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// It uses postNoRetry to make individual requests.
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func (c *Client) post(ctx context.Context, key crypto.Signer, url string, body interface{}, ok resOkay) (*http.Response, error) {
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retry := c.retryTimer()
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for {
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res, req, err := c.postNoRetry(ctx, key, url, body)
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if err != nil {
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return nil, err
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}
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if ok(res) {
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return res, nil
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}
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resErr := responseError(res)
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res.Body.Close()
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switch {
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// Check for bad nonce before isRetriable because it may have been returned
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// with an unretriable response code such as 400 Bad Request.
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case isBadNonce(resErr):
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// Consider any previously stored nonce values to be invalid.
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c.clearNonces()
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case !isRetriable(res.StatusCode):
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return nil, resErr
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}
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retry.inc()
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// Ignore the error value from retry.backoff
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// and return the one from last retry, as received from the CA.
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if err := retry.backoff(ctx, req, res); err != nil {
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return nil, resErr
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}
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}
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}
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// postNoRetry signs the body with the given key and POSTs it to the provided url.
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// It is used by c.post to retry unsuccessful attempts.
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// The body argument must be JSON-serializable.
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//
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// If key argument is nil, c.Key is used to sign the request.
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// If key argument is nil and c.accountKID returns a non-zero keyID,
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// the request is sent in KID form. Otherwise, JWK form is used.
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//
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// In practice, when interfacing with RFC-compliant CAs most requests are sent in KID form
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// and JWK is used only when KID is unavailable: new account endpoint and certificate
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// revocation requests authenticated by a cert key.
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// See jwsEncodeJSON for other details.
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func (c *Client) postNoRetry(ctx context.Context, key crypto.Signer, url string, body interface{}) (*http.Response, *http.Request, error) {
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kid := noKeyID
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if key == nil {
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key = c.Key
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kid = c.accountKID(ctx)
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}
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nonce, err := c.popNonce(ctx, url)
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if err != nil {
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return nil, nil, err
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}
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b, err := jwsEncodeJSON(body, key, kid, nonce, url)
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if err != nil {
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return nil, nil, err
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}
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req, err := http.NewRequest("POST", url, bytes.NewReader(b))
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if err != nil {
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return nil, nil, err
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}
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req.Header.Set("Content-Type", "application/jose+json")
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res, err := c.doNoRetry(ctx, req)
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if err != nil {
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return nil, nil, err
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}
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c.addNonce(res.Header)
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return res, req, nil
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}
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// doNoRetry issues a request req, replacing its context (if any) with ctx.
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func (c *Client) doNoRetry(ctx context.Context, req *http.Request) (*http.Response, error) {
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req.Header.Set("User-Agent", c.userAgent())
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res, err := c.httpClient().Do(req.WithContext(ctx))
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if err != nil {
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select {
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case <-ctx.Done():
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// Prefer the unadorned context error.
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// (The acme package had tests assuming this, previously from ctxhttp's
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// behavior, predating net/http supporting contexts natively)
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// TODO(bradfitz): reconsider this in the future. But for now this
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// requires no test updates.
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return nil, ctx.Err()
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default:
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return nil, err
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}
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}
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return res, nil
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}
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func (c *Client) httpClient() *http.Client {
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if c.HTTPClient != nil {
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return c.HTTPClient
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}
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return http.DefaultClient
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}
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// packageVersion is the version of the module that contains this package, for
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// sending as part of the User-Agent header. It's set in version_go112.go.
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var packageVersion string
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// userAgent returns the User-Agent header value. It includes the package name,
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// the module version (if available), and the c.UserAgent value (if set).
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func (c *Client) userAgent() string {
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ua := "golang.org/x/crypto/acme"
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if packageVersion != "" {
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ua += "@" + packageVersion
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}
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if c.UserAgent != "" {
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ua = c.UserAgent + " " + ua
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}
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return ua
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}
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// isBadNonce reports whether err is an ACME "badnonce" error.
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func isBadNonce(err error) bool {
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// According to the spec badNonce is urn:ietf:params:acme:error:badNonce.
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// However, ACME servers in the wild return their versions of the error.
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// See https://tools.ietf.org/html/draft-ietf-acme-acme-02#section-5.4
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// and https://github.com/letsencrypt/boulder/blob/0e07eacb/docs/acme-divergences.md#section-66.
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ae, ok := err.(*Error)
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return ok && strings.HasSuffix(strings.ToLower(ae.ProblemType), ":badnonce")
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}
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// isRetriable reports whether a request can be retried
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// based on the response status code.
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//
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// Note that a "bad nonce" error is returned with a non-retriable 400 Bad Request code.
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// Callers should parse the response and check with isBadNonce.
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func isRetriable(code int) bool {
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return code <= 399 || code >= 500 || code == http.StatusTooManyRequests
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}
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// responseError creates an error of Error type from resp.
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func responseError(resp *http.Response) error {
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// don't care if ReadAll returns an error:
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// json.Unmarshal will fail in that case anyway
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b, _ := ioutil.ReadAll(resp.Body)
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e := &wireError{Status: resp.StatusCode}
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if err := json.Unmarshal(b, e); err != nil {
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// this is not a regular error response:
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// populate detail with anything we received,
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// e.Status will already contain HTTP response code value
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e.Detail = string(b)
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if e.Detail == "" {
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e.Detail = resp.Status
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}
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}
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return e.error(resp.Header)
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}
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