1// Copyright 2015 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5// Package acme provides an implementation of the 6// Automatic Certificate Management Environment (ACME) spec. 7// The intial implementation was based on ACME draft-02 and 8// is now being extended to comply with RFC 8555. 9// See https://tools.ietf.org/html/draft-ietf-acme-acme-02 10// and https://tools.ietf.org/html/rfc8555 for details. 11// 12// Most common scenarios will want to use autocert subdirectory instead, 13// which provides automatic access to certificates from Let's Encrypt 14// and any other ACME-based CA. 15// 16// This package is a work in progress and makes no API stability promises. 17package acme 18 19import ( 20 "context" 21 "crypto" 22 "crypto/ecdsa" 23 "crypto/elliptic" 24 "crypto/rand" 25 "crypto/sha256" 26 "crypto/tls" 27 "crypto/x509" 28 "crypto/x509/pkix" 29 "encoding/asn1" 30 "encoding/base64" 31 "encoding/hex" 32 "encoding/json" 33 "encoding/pem" 34 "errors" 35 "fmt" 36 "io" 37 "io/ioutil" 38 "math/big" 39 "net/http" 40 "strings" 41 "sync" 42 "time" 43) 44 45const ( 46 // LetsEncryptURL is the Directory endpoint of Let's Encrypt CA. 47 LetsEncryptURL = "https://acme-v02.api.letsencrypt.org/directory" 48 49 // ALPNProto is the ALPN protocol name used by a CA server when validating 50 // tls-alpn-01 challenges. 51 // 52 // Package users must ensure their servers can negotiate the ACME ALPN in 53 // order for tls-alpn-01 challenge verifications to succeed. 54 // See the crypto/tls package's Config.NextProtos field. 55 ALPNProto = "acme-tls/1" 56) 57 58// idPeACMEIdentifier is the OID for the ACME extension for the TLS-ALPN challenge. 59// https://tools.ietf.org/html/draft-ietf-acme-tls-alpn-05#section-5.1 60var idPeACMEIdentifier = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 31} 61 62const ( 63 maxChainLen = 5 // max depth and breadth of a certificate chain 64 maxCertSize = 1 << 20 // max size of a certificate, in DER bytes 65 // Used for decoding certs from application/pem-certificate-chain response, 66 // the default when in RFC mode. 67 maxCertChainSize = maxCertSize * maxChainLen 68 69 // Max number of collected nonces kept in memory. 70 // Expect usual peak of 1 or 2. 71 maxNonces = 100 72) 73 74// Client is an ACME client. 75// The only required field is Key. An example of creating a client with a new key 76// is as follows: 77// 78// key, err := rsa.GenerateKey(rand.Reader, 2048) 79// if err != nil { 80// log.Fatal(err) 81// } 82// client := &Client{Key: key} 83// 84type Client struct { 85 // Key is the account key used to register with a CA and sign requests. 86 // Key.Public() must return a *rsa.PublicKey or *ecdsa.PublicKey. 87 // 88 // The following algorithms are supported: 89 // RS256, ES256, ES384 and ES512. 90 // See RFC7518 for more details about the algorithms. 91 Key crypto.Signer 92 93 // HTTPClient optionally specifies an HTTP client to use 94 // instead of http.DefaultClient. 95 HTTPClient *http.Client 96 97 // DirectoryURL points to the CA directory endpoint. 98 // If empty, LetsEncryptURL is used. 99 // Mutating this value after a successful call of Client's Discover method 100 // will have no effect. 101 DirectoryURL string 102 103 // RetryBackoff computes the duration after which the nth retry of a failed request 104 // should occur. The value of n for the first call on failure is 1. 105 // The values of r and resp are the request and response of the last failed attempt. 106 // If the returned value is negative or zero, no more retries are done and an error 107 // is returned to the caller of the original method. 108 // 109 // Requests which result in a 4xx client error are not retried, 110 // except for 400 Bad Request due to "bad nonce" errors and 429 Too Many Requests. 111 // 112 // If RetryBackoff is nil, a truncated exponential backoff algorithm 113 // with the ceiling of 10 seconds is used, where each subsequent retry n 114 // is done after either ("Retry-After" + jitter) or (2^n seconds + jitter), 115 // preferring the former if "Retry-After" header is found in the resp. 116 // The jitter is a random value up to 1 second. 117 RetryBackoff func(n int, r *http.Request, resp *http.Response) time.Duration 118 119 // UserAgent is prepended to the User-Agent header sent to the ACME server, 120 // which by default is this package's name and version. 121 // 122 // Reusable libraries and tools in particular should set this value to be 123 // identifiable by the server, in case they are causing issues. 124 UserAgent string 125 126 cacheMu sync.Mutex 127 dir *Directory // cached result of Client's Discover method 128 kid keyID // cached Account.URI obtained from registerRFC or getAccountRFC 129 130 noncesMu sync.Mutex 131 nonces map[string]struct{} // nonces collected from previous responses 132} 133 134// accountKID returns a key ID associated with c.Key, the account identity 135// provided by the CA during RFC based registration. 136// It assumes c.Discover has already been called. 137// 138// accountKID requires at most one network roundtrip. 139// It caches only successful result. 140// 141// When in pre-RFC mode or when c.getRegRFC responds with an error, accountKID 142// returns noKeyID. 143func (c *Client) accountKID(ctx context.Context) keyID { 144 c.cacheMu.Lock() 145 defer c.cacheMu.Unlock() 146 if !c.dir.rfcCompliant() { 147 return noKeyID 148 } 149 if c.kid != noKeyID { 150 return c.kid 151 } 152 a, err := c.getRegRFC(ctx) 153 if err != nil { 154 return noKeyID 155 } 156 c.kid = keyID(a.URI) 157 return c.kid 158} 159 160// Discover performs ACME server discovery using c.DirectoryURL. 161// 162// It caches successful result. So, subsequent calls will not result in 163// a network round-trip. This also means mutating c.DirectoryURL after successful call 164// of this method will have no effect. 165func (c *Client) Discover(ctx context.Context) (Directory, error) { 166 c.cacheMu.Lock() 167 defer c.cacheMu.Unlock() 168 if c.dir != nil { 169 return *c.dir, nil 170 } 171 172 res, err := c.get(ctx, c.directoryURL(), wantStatus(http.StatusOK)) 173 if err != nil { 174 return Directory{}, err 175 } 176 defer res.Body.Close() 177 c.addNonce(res.Header) 178 179 var v struct { 180 Reg string `json:"new-reg"` 181 RegRFC string `json:"newAccount"` 182 Authz string `json:"new-authz"` 183 AuthzRFC string `json:"newAuthz"` 184 OrderRFC string `json:"newOrder"` 185 Cert string `json:"new-cert"` 186 Revoke string `json:"revoke-cert"` 187 RevokeRFC string `json:"revokeCert"` 188 NonceRFC string `json:"newNonce"` 189 KeyChangeRFC string `json:"keyChange"` 190 Meta struct { 191 Terms string `json:"terms-of-service"` 192 TermsRFC string `json:"termsOfService"` 193 WebsiteRFC string `json:"website"` 194 CAA []string `json:"caa-identities"` 195 CAARFC []string `json:"caaIdentities"` 196 ExternalAcctRFC bool `json:"externalAccountRequired"` 197 } 198 } 199 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 200 return Directory{}, err 201 } 202 if v.OrderRFC == "" { 203 // Non-RFC compliant ACME CA. 204 c.dir = &Directory{ 205 RegURL: v.Reg, 206 AuthzURL: v.Authz, 207 CertURL: v.Cert, 208 RevokeURL: v.Revoke, 209 Terms: v.Meta.Terms, 210 Website: v.Meta.WebsiteRFC, 211 CAA: v.Meta.CAA, 212 } 213 return *c.dir, nil 214 } 215 // RFC compliant ACME CA. 216 c.dir = &Directory{ 217 RegURL: v.RegRFC, 218 AuthzURL: v.AuthzRFC, 219 OrderURL: v.OrderRFC, 220 RevokeURL: v.RevokeRFC, 221 NonceURL: v.NonceRFC, 222 KeyChangeURL: v.KeyChangeRFC, 223 Terms: v.Meta.TermsRFC, 224 Website: v.Meta.WebsiteRFC, 225 CAA: v.Meta.CAARFC, 226 ExternalAccountRequired: v.Meta.ExternalAcctRFC, 227 } 228 return *c.dir, nil 229} 230 231func (c *Client) directoryURL() string { 232 if c.DirectoryURL != "" { 233 return c.DirectoryURL 234 } 235 return LetsEncryptURL 236} 237 238// CreateCert requests a new certificate using the Certificate Signing Request csr encoded in DER format. 239// It is incompatible with RFC 8555. Callers should use CreateOrderCert when interfacing 240// with an RFC-compliant CA. 241// 242// The exp argument indicates the desired certificate validity duration. CA may issue a certificate 243// with a different duration. 244// If the bundle argument is true, the returned value will also contain the CA (issuer) certificate chain. 245// 246// In the case where CA server does not provide the issued certificate in the response, 247// CreateCert will poll certURL using c.FetchCert, which will result in additional round-trips. 248// In such a scenario, the caller can cancel the polling with ctx. 249// 250// CreateCert returns an error if the CA's response or chain was unreasonably large. 251// Callers are encouraged to parse the returned value to ensure the certificate is valid and has the expected features. 252func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration, bundle bool) (der [][]byte, certURL string, err error) { 253 if _, err := c.Discover(ctx); err != nil { 254 return nil, "", err 255 } 256 257 req := struct { 258 Resource string `json:"resource"` 259 CSR string `json:"csr"` 260 NotBefore string `json:"notBefore,omitempty"` 261 NotAfter string `json:"notAfter,omitempty"` 262 }{ 263 Resource: "new-cert", 264 CSR: base64.RawURLEncoding.EncodeToString(csr), 265 } 266 now := timeNow() 267 req.NotBefore = now.Format(time.RFC3339) 268 if exp > 0 { 269 req.NotAfter = now.Add(exp).Format(time.RFC3339) 270 } 271 272 res, err := c.post(ctx, nil, c.dir.CertURL, req, wantStatus(http.StatusCreated)) 273 if err != nil { 274 return nil, "", err 275 } 276 defer res.Body.Close() 277 278 curl := res.Header.Get("Location") // cert permanent URL 279 if res.ContentLength == 0 { 280 // no cert in the body; poll until we get it 281 cert, err := c.FetchCert(ctx, curl, bundle) 282 return cert, curl, err 283 } 284 // slurp issued cert and CA chain, if requested 285 cert, err := c.responseCert(ctx, res, bundle) 286 return cert, curl, err 287} 288 289// FetchCert retrieves already issued certificate from the given url, in DER format. 290// It retries the request until the certificate is successfully retrieved, 291// context is cancelled by the caller or an error response is received. 292// 293// If the bundle argument is true, the returned value also contains the CA (issuer) 294// certificate chain. 295// 296// FetchCert returns an error if the CA's response or chain was unreasonably large. 297// Callers are encouraged to parse the returned value to ensure the certificate is valid 298// and has expected features. 299func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]byte, error) { 300 dir, err := c.Discover(ctx) 301 if err != nil { 302 return nil, err 303 } 304 if dir.rfcCompliant() { 305 return c.fetchCertRFC(ctx, url, bundle) 306 } 307 308 // Legacy non-authenticated GET request. 309 res, err := c.get(ctx, url, wantStatus(http.StatusOK)) 310 if err != nil { 311 return nil, err 312 } 313 return c.responseCert(ctx, res, bundle) 314} 315 316// RevokeCert revokes a previously issued certificate cert, provided in DER format. 317// 318// The key argument, used to sign the request, must be authorized 319// to revoke the certificate. It's up to the CA to decide which keys are authorized. 320// For instance, the key pair of the certificate may be authorized. 321// If the key is nil, c.Key is used instead. 322func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte, reason CRLReasonCode) error { 323 dir, err := c.Discover(ctx) 324 if err != nil { 325 return err 326 } 327 if dir.rfcCompliant() { 328 return c.revokeCertRFC(ctx, key, cert, reason) 329 } 330 331 // Legacy CA. 332 body := &struct { 333 Resource string `json:"resource"` 334 Cert string `json:"certificate"` 335 Reason int `json:"reason"` 336 }{ 337 Resource: "revoke-cert", 338 Cert: base64.RawURLEncoding.EncodeToString(cert), 339 Reason: int(reason), 340 } 341 res, err := c.post(ctx, key, dir.RevokeURL, body, wantStatus(http.StatusOK)) 342 if err != nil { 343 return err 344 } 345 defer res.Body.Close() 346 return nil 347} 348 349// AcceptTOS always returns true to indicate the acceptance of a CA's Terms of Service 350// during account registration. See Register method of Client for more details. 351func AcceptTOS(tosURL string) bool { return true } 352 353// Register creates a new account with the CA using c.Key. 354// It returns the registered account. The account acct is not modified. 355// 356// The registration may require the caller to agree to the CA's Terms of Service (TOS). 357// If so, and the account has not indicated the acceptance of the terms (see Account for details), 358// Register calls prompt with a TOS URL provided by the CA. Prompt should report 359// whether the caller agrees to the terms. To always accept the terms, the caller can use AcceptTOS. 360// 361// When interfacing with an RFC-compliant CA, non-RFC 8555 fields of acct are ignored 362// and prompt is called if Directory's Terms field is non-zero. 363// Also see Error's Instance field for when a CA requires already registered accounts to agree 364// to an updated Terms of Service. 365func (c *Client) Register(ctx context.Context, acct *Account, prompt func(tosURL string) bool) (*Account, error) { 366 dir, err := c.Discover(ctx) 367 if err != nil { 368 return nil, err 369 } 370 if dir.rfcCompliant() { 371 return c.registerRFC(ctx, acct, prompt) 372 } 373 374 // Legacy ACME draft registration flow. 375 a, err := c.doReg(ctx, dir.RegURL, "new-reg", acct) 376 if err != nil { 377 return nil, err 378 } 379 var accept bool 380 if a.CurrentTerms != "" && a.CurrentTerms != a.AgreedTerms { 381 accept = prompt(a.CurrentTerms) 382 } 383 if accept { 384 a.AgreedTerms = a.CurrentTerms 385 a, err = c.UpdateReg(ctx, a) 386 } 387 return a, err 388} 389 390// GetReg retrieves an existing account associated with c.Key. 391// 392// The url argument is an Account URI used with pre-RFC 8555 CAs. 393// It is ignored when interfacing with an RFC-compliant CA. 394func (c *Client) GetReg(ctx context.Context, url string) (*Account, error) { 395 dir, err := c.Discover(ctx) 396 if err != nil { 397 return nil, err 398 } 399 if dir.rfcCompliant() { 400 return c.getRegRFC(ctx) 401 } 402 403 // Legacy CA. 404 a, err := c.doReg(ctx, url, "reg", nil) 405 if err != nil { 406 return nil, err 407 } 408 a.URI = url 409 return a, nil 410} 411 412// UpdateReg updates an existing registration. 413// It returns an updated account copy. The provided account is not modified. 414// 415// When interfacing with RFC-compliant CAs, a.URI is ignored and the account URL 416// associated with c.Key is used instead. 417func (c *Client) UpdateReg(ctx context.Context, acct *Account) (*Account, error) { 418 dir, err := c.Discover(ctx) 419 if err != nil { 420 return nil, err 421 } 422 if dir.rfcCompliant() { 423 return c.updateRegRFC(ctx, acct) 424 } 425 426 // Legacy CA. 427 uri := acct.URI 428 a, err := c.doReg(ctx, uri, "reg", acct) 429 if err != nil { 430 return nil, err 431 } 432 a.URI = uri 433 return a, nil 434} 435 436// Authorize performs the initial step in the pre-authorization flow, 437// as opposed to order-based flow. 438// The caller will then need to choose from and perform a set of returned 439// challenges using c.Accept in order to successfully complete authorization. 440// 441// Once complete, the caller can use AuthorizeOrder which the CA 442// should provision with the already satisfied authorization. 443// For pre-RFC CAs, the caller can proceed directly to requesting a certificate 444// using CreateCert method. 445// 446// If an authorization has been previously granted, the CA may return 447// a valid authorization which has its Status field set to StatusValid. 448// 449// More about pre-authorization can be found at 450// https://tools.ietf.org/html/rfc8555#section-7.4.1. 451func (c *Client) Authorize(ctx context.Context, domain string) (*Authorization, error) { 452 return c.authorize(ctx, "dns", domain) 453} 454 455// AuthorizeIP is the same as Authorize but requests IP address authorization. 456// Clients which successfully obtain such authorization may request to issue 457// a certificate for IP addresses. 458// 459// See the ACME spec extension for more details about IP address identifiers: 460// https://tools.ietf.org/html/draft-ietf-acme-ip. 461func (c *Client) AuthorizeIP(ctx context.Context, ipaddr string) (*Authorization, error) { 462 return c.authorize(ctx, "ip", ipaddr) 463} 464 465func (c *Client) authorize(ctx context.Context, typ, val string) (*Authorization, error) { 466 if _, err := c.Discover(ctx); err != nil { 467 return nil, err 468 } 469 470 type authzID struct { 471 Type string `json:"type"` 472 Value string `json:"value"` 473 } 474 req := struct { 475 Resource string `json:"resource"` 476 Identifier authzID `json:"identifier"` 477 }{ 478 Resource: "new-authz", 479 Identifier: authzID{Type: typ, Value: val}, 480 } 481 res, err := c.post(ctx, nil, c.dir.AuthzURL, req, wantStatus(http.StatusCreated)) 482 if err != nil { 483 return nil, err 484 } 485 defer res.Body.Close() 486 487 var v wireAuthz 488 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 489 return nil, fmt.Errorf("acme: invalid response: %v", err) 490 } 491 if v.Status != StatusPending && v.Status != StatusValid { 492 return nil, fmt.Errorf("acme: unexpected status: %s", v.Status) 493 } 494 return v.authorization(res.Header.Get("Location")), nil 495} 496 497// GetAuthorization retrieves an authorization identified by the given URL. 498// 499// If a caller needs to poll an authorization until its status is final, 500// see the WaitAuthorization method. 501func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorization, error) { 502 dir, err := c.Discover(ctx) 503 if err != nil { 504 return nil, err 505 } 506 507 var res *http.Response 508 if dir.rfcCompliant() { 509 res, err = c.postAsGet(ctx, url, wantStatus(http.StatusOK)) 510 } else { 511 res, err = c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted)) 512 } 513 if err != nil { 514 return nil, err 515 } 516 defer res.Body.Close() 517 var v wireAuthz 518 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 519 return nil, fmt.Errorf("acme: invalid response: %v", err) 520 } 521 return v.authorization(url), nil 522} 523 524// RevokeAuthorization relinquishes an existing authorization identified 525// by the given URL. 526// The url argument is an Authorization.URI value. 527// 528// If successful, the caller will be required to obtain a new authorization 529// using the Authorize or AuthorizeOrder methods before being able to request 530// a new certificate for the domain associated with the authorization. 531// 532// It does not revoke existing certificates. 533func (c *Client) RevokeAuthorization(ctx context.Context, url string) error { 534 // Required for c.accountKID() when in RFC mode. 535 if _, err := c.Discover(ctx); err != nil { 536 return err 537 } 538 539 req := struct { 540 Resource string `json:"resource"` 541 Status string `json:"status"` 542 Delete bool `json:"delete"` 543 }{ 544 Resource: "authz", 545 Status: "deactivated", 546 Delete: true, 547 } 548 res, err := c.post(ctx, nil, url, req, wantStatus(http.StatusOK)) 549 if err != nil { 550 return err 551 } 552 defer res.Body.Close() 553 return nil 554} 555 556// WaitAuthorization polls an authorization at the given URL 557// until it is in one of the final states, StatusValid or StatusInvalid, 558// the ACME CA responded with a 4xx error code, or the context is done. 559// 560// It returns a non-nil Authorization only if its Status is StatusValid. 561// In all other cases WaitAuthorization returns an error. 562// If the Status is StatusInvalid, the returned error is of type *AuthorizationError. 563func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorization, error) { 564 // Required for c.accountKID() when in RFC mode. 565 dir, err := c.Discover(ctx) 566 if err != nil { 567 return nil, err 568 } 569 getfn := c.postAsGet 570 if !dir.rfcCompliant() { 571 getfn = c.get 572 } 573 574 for { 575 res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted)) 576 if err != nil { 577 return nil, err 578 } 579 580 var raw wireAuthz 581 err = json.NewDecoder(res.Body).Decode(&raw) 582 res.Body.Close() 583 switch { 584 case err != nil: 585 // Skip and retry. 586 case raw.Status == StatusValid: 587 return raw.authorization(url), nil 588 case raw.Status == StatusInvalid: 589 return nil, raw.error(url) 590 } 591 592 // Exponential backoff is implemented in c.get above. 593 // This is just to prevent continuously hitting the CA 594 // while waiting for a final authorization status. 595 d := retryAfter(res.Header.Get("Retry-After")) 596 if d == 0 { 597 // Given that the fastest challenges TLS-SNI and HTTP-01 598 // require a CA to make at least 1 network round trip 599 // and most likely persist a challenge state, 600 // this default delay seems reasonable. 601 d = time.Second 602 } 603 t := time.NewTimer(d) 604 select { 605 case <-ctx.Done(): 606 t.Stop() 607 return nil, ctx.Err() 608 case <-t.C: 609 // Retry. 610 } 611 } 612} 613 614// GetChallenge retrieves the current status of an challenge. 615// 616// A client typically polls a challenge status using this method. 617func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, error) { 618 // Required for c.accountKID() when in RFC mode. 619 dir, err := c.Discover(ctx) 620 if err != nil { 621 return nil, err 622 } 623 624 getfn := c.postAsGet 625 if !dir.rfcCompliant() { 626 getfn = c.get 627 } 628 res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted)) 629 if err != nil { 630 return nil, err 631 } 632 633 defer res.Body.Close() 634 v := wireChallenge{URI: url} 635 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 636 return nil, fmt.Errorf("acme: invalid response: %v", err) 637 } 638 return v.challenge(), nil 639} 640 641// Accept informs the server that the client accepts one of its challenges 642// previously obtained with c.Authorize. 643// 644// The server will then perform the validation asynchronously. 645func (c *Client) Accept(ctx context.Context, chal *Challenge) (*Challenge, error) { 646 // Required for c.accountKID() when in RFC mode. 647 dir, err := c.Discover(ctx) 648 if err != nil { 649 return nil, err 650 } 651 652 var req interface{} = json.RawMessage("{}") // RFC-compliant CA 653 if !dir.rfcCompliant() { 654 auth, err := keyAuth(c.Key.Public(), chal.Token) 655 if err != nil { 656 return nil, err 657 } 658 req = struct { 659 Resource string `json:"resource"` 660 Type string `json:"type"` 661 Auth string `json:"keyAuthorization"` 662 }{ 663 Resource: "challenge", 664 Type: chal.Type, 665 Auth: auth, 666 } 667 } 668 res, err := c.post(ctx, nil, chal.URI, req, wantStatus( 669 http.StatusOK, // according to the spec 670 http.StatusAccepted, // Let's Encrypt: see https://goo.gl/WsJ7VT (acme-divergences.md) 671 )) 672 if err != nil { 673 return nil, err 674 } 675 defer res.Body.Close() 676 677 var v wireChallenge 678 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 679 return nil, fmt.Errorf("acme: invalid response: %v", err) 680 } 681 return v.challenge(), nil 682} 683 684// DNS01ChallengeRecord returns a DNS record value for a dns-01 challenge response. 685// A TXT record containing the returned value must be provisioned under 686// "_acme-challenge" name of the domain being validated. 687// 688// The token argument is a Challenge.Token value. 689func (c *Client) DNS01ChallengeRecord(token string) (string, error) { 690 ka, err := keyAuth(c.Key.Public(), token) 691 if err != nil { 692 return "", err 693 } 694 b := sha256.Sum256([]byte(ka)) 695 return base64.RawURLEncoding.EncodeToString(b[:]), nil 696} 697 698// HTTP01ChallengeResponse returns the response for an http-01 challenge. 699// Servers should respond with the value to HTTP requests at the URL path 700// provided by HTTP01ChallengePath to validate the challenge and prove control 701// over a domain name. 702// 703// The token argument is a Challenge.Token value. 704func (c *Client) HTTP01ChallengeResponse(token string) (string, error) { 705 return keyAuth(c.Key.Public(), token) 706} 707 708// HTTP01ChallengePath returns the URL path at which the response for an http-01 challenge 709// should be provided by the servers. 710// The response value can be obtained with HTTP01ChallengeResponse. 711// 712// The token argument is a Challenge.Token value. 713func (c *Client) HTTP01ChallengePath(token string) string { 714 return "/.well-known/acme-challenge/" + token 715} 716 717// TLSSNI01ChallengeCert creates a certificate for TLS-SNI-01 challenge response. 718// 719// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec. 720func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) { 721 ka, err := keyAuth(c.Key.Public(), token) 722 if err != nil { 723 return tls.Certificate{}, "", err 724 } 725 b := sha256.Sum256([]byte(ka)) 726 h := hex.EncodeToString(b[:]) 727 name = fmt.Sprintf("%s.%s.acme.invalid", h[:32], h[32:]) 728 cert, err = tlsChallengeCert([]string{name}, opt) 729 if err != nil { 730 return tls.Certificate{}, "", err 731 } 732 return cert, name, nil 733} 734 735// TLSSNI02ChallengeCert creates a certificate for TLS-SNI-02 challenge response. 736// 737// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec. 738func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) { 739 b := sha256.Sum256([]byte(token)) 740 h := hex.EncodeToString(b[:]) 741 sanA := fmt.Sprintf("%s.%s.token.acme.invalid", h[:32], h[32:]) 742 743 ka, err := keyAuth(c.Key.Public(), token) 744 if err != nil { 745 return tls.Certificate{}, "", err 746 } 747 b = sha256.Sum256([]byte(ka)) 748 h = hex.EncodeToString(b[:]) 749 sanB := fmt.Sprintf("%s.%s.ka.acme.invalid", h[:32], h[32:]) 750 751 cert, err = tlsChallengeCert([]string{sanA, sanB}, opt) 752 if err != nil { 753 return tls.Certificate{}, "", err 754 } 755 return cert, sanA, nil 756} 757 758// TLSALPN01ChallengeCert creates a certificate for TLS-ALPN-01 challenge response. 759// Servers can present the certificate to validate the challenge and prove control 760// over a domain name. For more details on TLS-ALPN-01 see 761// https://tools.ietf.org/html/draft-shoemaker-acme-tls-alpn-00#section-3 762// 763// The token argument is a Challenge.Token value. 764// If a WithKey option is provided, its private part signs the returned cert, 765// and the public part is used to specify the signee. 766// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve. 767// 768// The returned certificate is valid for the next 24 hours and must be presented only when 769// the server name in the TLS ClientHello matches the domain, and the special acme-tls/1 ALPN protocol 770// has been specified. 771func (c *Client) TLSALPN01ChallengeCert(token, domain string, opt ...CertOption) (cert tls.Certificate, err error) { 772 ka, err := keyAuth(c.Key.Public(), token) 773 if err != nil { 774 return tls.Certificate{}, err 775 } 776 shasum := sha256.Sum256([]byte(ka)) 777 extValue, err := asn1.Marshal(shasum[:]) 778 if err != nil { 779 return tls.Certificate{}, err 780 } 781 acmeExtension := pkix.Extension{ 782 Id: idPeACMEIdentifier, 783 Critical: true, 784 Value: extValue, 785 } 786 787 tmpl := defaultTLSChallengeCertTemplate() 788 789 var newOpt []CertOption 790 for _, o := range opt { 791 switch o := o.(type) { 792 case *certOptTemplate: 793 t := *(*x509.Certificate)(o) // shallow copy is ok 794 tmpl = &t 795 default: 796 newOpt = append(newOpt, o) 797 } 798 } 799 tmpl.ExtraExtensions = append(tmpl.ExtraExtensions, acmeExtension) 800 newOpt = append(newOpt, WithTemplate(tmpl)) 801 return tlsChallengeCert([]string{domain}, newOpt) 802} 803 804// doReg sends all types of registration requests the old way (pre-RFC world). 805// The type of request is identified by typ argument, which is a "resource" 806// in the ACME spec terms. 807// 808// A non-nil acct argument indicates whether the intention is to mutate data 809// of the Account. Only Contact and Agreement of its fields are used 810// in such cases. 811func (c *Client) doReg(ctx context.Context, url string, typ string, acct *Account) (*Account, error) { 812 req := struct { 813 Resource string `json:"resource"` 814 Contact []string `json:"contact,omitempty"` 815 Agreement string `json:"agreement,omitempty"` 816 }{ 817 Resource: typ, 818 } 819 if acct != nil { 820 req.Contact = acct.Contact 821 req.Agreement = acct.AgreedTerms 822 } 823 res, err := c.post(ctx, nil, url, req, wantStatus( 824 http.StatusOK, // updates and deletes 825 http.StatusCreated, // new account creation 826 http.StatusAccepted, // Let's Encrypt divergent implementation 827 )) 828 if err != nil { 829 return nil, err 830 } 831 defer res.Body.Close() 832 833 var v struct { 834 Contact []string 835 Agreement string 836 Authorizations string 837 Certificates string 838 } 839 if err := json.NewDecoder(res.Body).Decode(&v); err != nil { 840 return nil, fmt.Errorf("acme: invalid response: %v", err) 841 } 842 var tos string 843 if v := linkHeader(res.Header, "terms-of-service"); len(v) > 0 { 844 tos = v[0] 845 } 846 var authz string 847 if v := linkHeader(res.Header, "next"); len(v) > 0 { 848 authz = v[0] 849 } 850 return &Account{ 851 URI: res.Header.Get("Location"), 852 Contact: v.Contact, 853 AgreedTerms: v.Agreement, 854 CurrentTerms: tos, 855 Authz: authz, 856 Authorizations: v.Authorizations, 857 Certificates: v.Certificates, 858 }, nil 859} 860 861// popNonce returns a nonce value previously stored with c.addNonce 862// or fetches a fresh one from c.dir.NonceURL. 863// If NonceURL is empty, it first tries c.directoryURL() and, failing that, 864// the provided url. 865func (c *Client) popNonce(ctx context.Context, url string) (string, error) { 866 c.noncesMu.Lock() 867 defer c.noncesMu.Unlock() 868 if len(c.nonces) == 0 { 869 if c.dir != nil && c.dir.NonceURL != "" { 870 return c.fetchNonce(ctx, c.dir.NonceURL) 871 } 872 dirURL := c.directoryURL() 873 v, err := c.fetchNonce(ctx, dirURL) 874 if err != nil && url != dirURL { 875 v, err = c.fetchNonce(ctx, url) 876 } 877 return v, err 878 } 879 var nonce string 880 for nonce = range c.nonces { 881 delete(c.nonces, nonce) 882 break 883 } 884 return nonce, nil 885} 886 887// clearNonces clears any stored nonces 888func (c *Client) clearNonces() { 889 c.noncesMu.Lock() 890 defer c.noncesMu.Unlock() 891 c.nonces = make(map[string]struct{}) 892} 893 894// addNonce stores a nonce value found in h (if any) for future use. 895func (c *Client) addNonce(h http.Header) { 896 v := nonceFromHeader(h) 897 if v == "" { 898 return 899 } 900 c.noncesMu.Lock() 901 defer c.noncesMu.Unlock() 902 if len(c.nonces) >= maxNonces { 903 return 904 } 905 if c.nonces == nil { 906 c.nonces = make(map[string]struct{}) 907 } 908 c.nonces[v] = struct{}{} 909} 910 911func (c *Client) fetchNonce(ctx context.Context, url string) (string, error) { 912 r, err := http.NewRequest("HEAD", url, nil) 913 if err != nil { 914 return "", err 915 } 916 resp, err := c.doNoRetry(ctx, r) 917 if err != nil { 918 return "", err 919 } 920 defer resp.Body.Close() 921 nonce := nonceFromHeader(resp.Header) 922 if nonce == "" { 923 if resp.StatusCode > 299 { 924 return "", responseError(resp) 925 } 926 return "", errors.New("acme: nonce not found") 927 } 928 return nonce, nil 929} 930 931func nonceFromHeader(h http.Header) string { 932 return h.Get("Replay-Nonce") 933} 934 935func (c *Client) responseCert(ctx context.Context, res *http.Response, bundle bool) ([][]byte, error) { 936 b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1)) 937 if err != nil { 938 return nil, fmt.Errorf("acme: response stream: %v", err) 939 } 940 if len(b) > maxCertSize { 941 return nil, errors.New("acme: certificate is too big") 942 } 943 cert := [][]byte{b} 944 if !bundle { 945 return cert, nil 946 } 947 948 // Append CA chain cert(s). 949 // At least one is required according to the spec: 950 // https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-6.3.1 951 up := linkHeader(res.Header, "up") 952 if len(up) == 0 { 953 return nil, errors.New("acme: rel=up link not found") 954 } 955 if len(up) > maxChainLen { 956 return nil, errors.New("acme: rel=up link is too large") 957 } 958 for _, url := range up { 959 cc, err := c.chainCert(ctx, url, 0) 960 if err != nil { 961 return nil, err 962 } 963 cert = append(cert, cc...) 964 } 965 return cert, nil 966} 967 968// chainCert fetches CA certificate chain recursively by following "up" links. 969// Each recursive call increments the depth by 1, resulting in an error 970// if the recursion level reaches maxChainLen. 971// 972// First chainCert call starts with depth of 0. 973func (c *Client) chainCert(ctx context.Context, url string, depth int) ([][]byte, error) { 974 if depth >= maxChainLen { 975 return nil, errors.New("acme: certificate chain is too deep") 976 } 977 978 res, err := c.get(ctx, url, wantStatus(http.StatusOK)) 979 if err != nil { 980 return nil, err 981 } 982 defer res.Body.Close() 983 b, err := ioutil.ReadAll(io.LimitReader(res.Body, maxCertSize+1)) 984 if err != nil { 985 return nil, err 986 } 987 if len(b) > maxCertSize { 988 return nil, errors.New("acme: certificate is too big") 989 } 990 chain := [][]byte{b} 991 992 uplink := linkHeader(res.Header, "up") 993 if len(uplink) > maxChainLen { 994 return nil, errors.New("acme: certificate chain is too large") 995 } 996 for _, up := range uplink { 997 cc, err := c.chainCert(ctx, up, depth+1) 998 if err != nil { 999 return nil, err 1000 } 1001 chain = append(chain, cc...) 1002 } 1003 1004 return chain, nil 1005} 1006 1007// linkHeader returns URI-Reference values of all Link headers 1008// with relation-type rel. 1009// See https://tools.ietf.org/html/rfc5988#section-5 for details. 1010func linkHeader(h http.Header, rel string) []string { 1011 var links []string 1012 for _, v := range h["Link"] { 1013 parts := strings.Split(v, ";") 1014 for _, p := range parts { 1015 p = strings.TrimSpace(p) 1016 if !strings.HasPrefix(p, "rel=") { 1017 continue 1018 } 1019 if v := strings.Trim(p[4:], `"`); v == rel { 1020 links = append(links, strings.Trim(parts[0], "<>")) 1021 } 1022 } 1023 } 1024 return links 1025} 1026 1027// keyAuth generates a key authorization string for a given token. 1028func keyAuth(pub crypto.PublicKey, token string) (string, error) { 1029 th, err := JWKThumbprint(pub) 1030 if err != nil { 1031 return "", err 1032 } 1033 return fmt.Sprintf("%s.%s", token, th), nil 1034} 1035 1036// defaultTLSChallengeCertTemplate is a template used to create challenge certs for TLS challenges. 1037func defaultTLSChallengeCertTemplate() *x509.Certificate { 1038 return &x509.Certificate{ 1039 SerialNumber: big.NewInt(1), 1040 NotBefore: time.Now(), 1041 NotAfter: time.Now().Add(24 * time.Hour), 1042 BasicConstraintsValid: true, 1043 KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature, 1044 ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}, 1045 } 1046} 1047 1048// tlsChallengeCert creates a temporary certificate for TLS-SNI challenges 1049// with the given SANs and auto-generated public/private key pair. 1050// The Subject Common Name is set to the first SAN to aid debugging. 1051// To create a cert with a custom key pair, specify WithKey option. 1052func tlsChallengeCert(san []string, opt []CertOption) (tls.Certificate, error) { 1053 var key crypto.Signer 1054 tmpl := defaultTLSChallengeCertTemplate() 1055 for _, o := range opt { 1056 switch o := o.(type) { 1057 case *certOptKey: 1058 if key != nil { 1059 return tls.Certificate{}, errors.New("acme: duplicate key option") 1060 } 1061 key = o.key 1062 case *certOptTemplate: 1063 t := *(*x509.Certificate)(o) // shallow copy is ok 1064 tmpl = &t 1065 default: 1066 // package's fault, if we let this happen: 1067 panic(fmt.Sprintf("unsupported option type %T", o)) 1068 } 1069 } 1070 if key == nil { 1071 var err error 1072 if key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader); err != nil { 1073 return tls.Certificate{}, err 1074 } 1075 } 1076 tmpl.DNSNames = san 1077 if len(san) > 0 { 1078 tmpl.Subject.CommonName = san[0] 1079 } 1080 1081 der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, key.Public(), key) 1082 if err != nil { 1083 return tls.Certificate{}, err 1084 } 1085 return tls.Certificate{ 1086 Certificate: [][]byte{der}, 1087 PrivateKey: key, 1088 }, nil 1089} 1090 1091// encodePEM returns b encoded as PEM with block of type typ. 1092func encodePEM(typ string, b []byte) []byte { 1093 pb := &pem.Block{Type: typ, Bytes: b} 1094 return pem.EncodeToMemory(pb) 1095} 1096 1097// timeNow is useful for testing for fixed current time. 1098var timeNow = time.Now 1099