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acme: update existing methods for RFC 8555
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This adds RFC support to the existing methods which,
in conjunction with the new order based methods
implemented in golang.org/cl/192779, completes a Client
capable of obtaining certificates from RFC compliant CAs.

Updates golang/go#21081

Change-Id: I3aabc50928d3e4e49ee202eb6695135d5ad86821
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/194379
Reviewed-by: Filippo Valsorda <[email protected]>
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@x1ddos
x1ddos authored and Alex Vaghin committed Oct 1, 2019
1 parent 8834368 commit 4663e18
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Showing 6 changed files with 404 additions and 113 deletions.
166 changes: 100 additions & 66 deletions acme/acme.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
// Package acme provides an implementation of the
// Automatic Certificate Management Environment (ACME) spec.
// The intial implementation was based on ACME draft-02 and
// is now being extended to comply with RFC8555.
// is now being extended to comply with RFC 8555.
// See https://tools.ietf.org/html/draft-ietf-acme-acme-02
// and https://tools.ietf.org/html/rfc8555 for details.
//
Expand Down Expand Up @@ -60,7 +60,10 @@ var idPeACMEIdentifierV1 = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 30, 1}

const (
maxChainLen = 5 // max depth and breadth of a certificate chain
maxCertSize = 1 << 20 // max size of a certificate, in bytes
maxCertSize = 1 << 20 // max size of a certificate, in DER bytes
// Used for decoding certs from application/pem-certificate-chain response,
// the default when in RFC mode.
maxCertChainSize = maxCertSize * maxChainLen

// Max number of collected nonces kept in memory.
// Expect usual peak of 1 or 2.
Expand Down Expand Up @@ -139,8 +142,7 @@ type Client struct {
func (c *Client) accountKID(ctx context.Context) keyID {
c.cacheMu.Lock()
defer c.cacheMu.Unlock()
if c.dir.OrderURL == "" {
// Assume legacy CA.
if !c.dir.rfcCompliant() {
return noKeyID
}
if c.kid != noKeyID {
Expand Down Expand Up @@ -233,6 +235,9 @@ func (c *Client) directoryURL() string {
}

// CreateCert requests a new certificate using the Certificate Signing Request csr encoded in DER format.
// It is incompatible with RFC 8555. Callers should use CreateOrderCert when interfacing
// with an RFC-compliant CA.
//
// The exp argument indicates the desired certificate validity duration. CA may issue a certificate
// with a different duration.
// If the bundle argument is true, the returned value will also contain the CA (issuer) certificate chain.
Expand Down Expand Up @@ -284,12 +289,22 @@ func (c *Client) CreateCert(ctx context.Context, csr []byte, exp time.Duration,
// It retries the request until the certificate is successfully retrieved,
// context is cancelled by the caller or an error response is received.
//
// The returned value will also contain the CA (issuer) certificate if the bundle argument is true.
// If the bundle argument is true, the returned value also contains the CA (issuer)
// certificate chain.
//
// FetchCert returns an error if the CA's response or chain was unreasonably large.
// Callers are encouraged to parse the returned value to ensure the certificate is valid
// and has expected features.
func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]byte, error) {
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}
if dir.rfcCompliant() {
return c.fetchCertRFC(ctx, url, bundle)
}

// Legacy non-authenticated GET request.
res, err := c.get(ctx, url, wantStatus(http.StatusOK))
if err != nil {
return nil, err
Expand All @@ -304,10 +319,15 @@ func (c *Client) FetchCert(ctx context.Context, url string, bundle bool) ([][]by
// For instance, the key pair of the certificate may be authorized.
// If the key is nil, c.Key is used instead.
func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte, reason CRLReasonCode) error {
if _, err := c.Discover(ctx); err != nil {
dir, err := c.Discover(ctx)
if err != nil {
return err
}
if dir.rfcCompliant() {
return c.revokeCertRFC(ctx, key, cert, reason)
}

// Legacy CA.
body := &struct {
Resource string `json:"resource"`
Cert string `json:"certificate"`
Expand All @@ -317,7 +337,7 @@ func (c *Client) RevokeCert(ctx context.Context, key crypto.Signer, cert []byte,
Cert: base64.RawURLEncoding.EncodeToString(cert),
Reason: int(reason),
}
res, err := c.post(ctx, key, c.dir.RevokeURL, body, wantStatus(http.StatusOK))
res, err := c.post(ctx, key, dir.RevokeURL, body, wantStatus(http.StatusOK))
if err != nil {
return err
}
Expand All @@ -337,7 +357,7 @@ func AcceptTOS(tosURL string) bool { return true }
// Register calls prompt with a TOS URL provided by the CA. Prompt should report
// whether the caller agrees to the terms. To always accept the terms, the caller can use AcceptTOS.
//
// When interfacing with RFC compliant CA, non-RFC8555 compliant fields of acct are ignored
// When interfacing with an RFC-compliant CA, non-RFC 8555 fields of acct are ignored
// and prompt is called if Directory's Terms field is non-zero.
// Also see Error's Instance field for when a CA requires already registered accounts to agree
// to an updated Terms of Service.
Expand All @@ -346,9 +366,7 @@ func (c *Client) Register(ctx context.Context, acct *Account, prompt func(tosURL
if err != nil {
return nil, err
}

// RFC8555 compliant account registration.
if dir.OrderURL != "" {
if dir.rfcCompliant() {
return c.registerRFC(ctx, acct, prompt)
}

Expand All @@ -370,16 +388,14 @@ func (c *Client) Register(ctx context.Context, acct *Account, prompt func(tosURL

// GetReg retrieves an existing account associated with c.Key.
//
// The url argument is an Account URI used with pre-RFC8555 CAs.
// It is ignored when interfacing with an RFC compliant CA.
// The url argument is an Account URI used with pre-RFC 8555 CAs.
// It is ignored when interfacing with an RFC-compliant CA.
func (c *Client) GetReg(ctx context.Context, url string) (*Account, error) {
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}

// Assume RFC8555 compliant CA.
if dir.OrderURL != "" {
if dir.rfcCompliant() {
return c.getRegRFC(ctx)
}

Expand All @@ -395,16 +411,14 @@ func (c *Client) GetReg(ctx context.Context, url string) (*Account, error) {
// UpdateReg updates an existing registration.
// It returns an updated account copy. The provided account is not modified.
//
// When interfacing with RFC compliant CAs, a.URI is ignored and the account URL
// When interfacing with RFC-compliant CAs, a.URI is ignored and the account URL
// associated with c.Key is used instead.
func (c *Client) UpdateReg(ctx context.Context, acct *Account) (*Account, error) {
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}

// Assume RFC8555 compliant CA.
if dir.OrderURL != "" {
if dir.rfcCompliant() {
return c.updateRegRFC(ctx, acct)
}

Expand All @@ -418,13 +432,21 @@ func (c *Client) UpdateReg(ctx context.Context, acct *Account) (*Account, error)
return a, nil
}

// Authorize performs the initial step in an authorization flow.
// Authorize performs the initial step in the pre-authorization flow,
// as opposed to order-based flow.
// The caller will then need to choose from and perform a set of returned
// challenges using c.Accept in order to successfully complete authorization.
//
// Once complete, the caller can use AuthorizeOrder which the CA
// should provision with the already satisfied authorization.
// For pre-RFC CAs, the caller can proceed directly to requesting a certificate
// using CreateCert method.
//
// If an authorization has been previously granted, the CA may return
// a valid authorization (Authorization.Status is StatusValid). If so, the caller
// need not fulfill any challenge and can proceed to requesting a certificate.
// a valid authorization which has its Status field set to StatusValid.
//
// More about pre-authorization can be found at
// https://tools.ietf.org/html/rfc8555#section-7.4.1.
func (c *Client) Authorize(ctx context.Context, domain string) (*Authorization, error) {
return c.authorize(ctx, "dns", domain)
}
Expand Down Expand Up @@ -476,7 +498,17 @@ func (c *Client) authorize(ctx context.Context, typ, val string) (*Authorization
// If a caller needs to poll an authorization until its status is final,
// see the WaitAuthorization method.
func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorization, error) {
res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}

var res *http.Response
if dir.rfcCompliant() {
res, err = c.postAsGet(ctx, url, wantStatus(http.StatusOK))
} else {
res, err = c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
}
if err != nil {
return nil, err
}
Expand All @@ -493,8 +525,8 @@ func (c *Client) GetAuthorization(ctx context.Context, url string) (*Authorizati
// The url argument is an Authorization.URI value.
//
// If successful, the caller will be required to obtain a new authorization
// using the Authorize method before being able to request a new certificate
// for the domain associated with the authorization.
// using the Authorize or AuthorizeOrder methods before being able to request
// a new certificate for the domain associated with the authorization.
//
// It does not revoke existing certificates.
func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
Expand Down Expand Up @@ -528,8 +560,18 @@ func (c *Client) RevokeAuthorization(ctx context.Context, url string) error {
// In all other cases WaitAuthorization returns an error.
// If the Status is StatusInvalid, the returned error is of type *AuthorizationError.
func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorization, error) {
// Required for c.accountKID() when in RFC mode.
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}
getfn := c.postAsGet
if !dir.rfcCompliant() {
getfn = c.get
}

for {
res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
if err != nil {
return nil, err
}
Expand Down Expand Up @@ -572,10 +614,21 @@ func (c *Client) WaitAuthorization(ctx context.Context, url string) (*Authorizat
//
// A client typically polls a challenge status using this method.
func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, error) {
res, err := c.get(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
// Required for c.accountKID() when in RFC mode.
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}

getfn := c.postAsGet
if !dir.rfcCompliant() {
getfn = c.get
}
res, err := getfn(ctx, url, wantStatus(http.StatusOK, http.StatusAccepted))
if err != nil {
return nil, err
}

defer res.Body.Close()
v := wireChallenge{URI: url}
if err := json.NewDecoder(res.Body).Decode(&v); err != nil {
Expand All @@ -590,23 +643,26 @@ func (c *Client) GetChallenge(ctx context.Context, url string) (*Challenge, erro
// The server will then perform the validation asynchronously.
func (c *Client) Accept(ctx context.Context, chal *Challenge) (*Challenge, error) {
// Required for c.accountKID() when in RFC mode.
if _, err := c.Discover(ctx); err != nil {
return nil, err
}

auth, err := keyAuth(c.Key.Public(), chal.Token)
dir, err := c.Discover(ctx)
if err != nil {
return nil, err
}

req := struct {
Resource string `json:"resource"`
Type string `json:"type"`
Auth string `json:"keyAuthorization"`
}{
Resource: "challenge",
Type: chal.Type,
Auth: auth,
var req interface{} = json.RawMessage("{}") // RFC-compliant CA
if !dir.rfcCompliant() {
auth, err := keyAuth(c.Key.Public(), chal.Token)
if err != nil {
return nil, err
}
req = struct {
Resource string `json:"resource"`
Type string `json:"type"`
Auth string `json:"keyAuthorization"`
}{
Resource: "challenge",
Type: chal.Type,
Auth: auth,
}
}
res, err := c.post(ctx, nil, chal.URI, req, wantStatus(
http.StatusOK, // according to the spec
Expand Down Expand Up @@ -658,21 +714,8 @@ func (c *Client) HTTP01ChallengePath(token string) string {
}

// TLSSNI01ChallengeCert creates a certificate for TLS-SNI-01 challenge response.
// Servers can present the certificate to validate the challenge and prove control
// over a domain name.
//
// The implementation is incomplete in that the returned value is a single certificate,
// computed only for Z0 of the key authorization. ACME CAs are expected to update
// their implementations to use the newer version, TLS-SNI-02.
// For more details on TLS-SNI-01 see https://tools.ietf.org/html/draft-ietf-acme-acme-01#section-7.3.
//
// The token argument is a Challenge.Token value.
// If a WithKey option is provided, its private part signs the returned cert,
// and the public part is used to specify the signee.
// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
//
// The returned certificate is valid for the next 24 hours and must be presented only when
// the server name of the TLS ClientHello matches exactly the returned name value.
// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec.
func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
ka, err := keyAuth(c.Key.Public(), token)
if err != nil {
Expand All @@ -689,17 +732,8 @@ func (c *Client) TLSSNI01ChallengeCert(token string, opt ...CertOption) (cert tl
}

// TLSSNI02ChallengeCert creates a certificate for TLS-SNI-02 challenge response.
// Servers can present the certificate to validate the challenge and prove control
// over a domain name. For more details on TLS-SNI-02 see
// https://tools.ietf.org/html/draft-ietf-acme-acme-03#section-7.3.
//
// The token argument is a Challenge.Token value.
// If a WithKey option is provided, its private part signs the returned cert,
// and the public part is used to specify the signee.
// If no WithKey option is provided, a new ECDSA key is generated using P-256 curve.
//
// The returned certificate is valid for the next 24 hours and must be presented only when
// the server name in the TLS ClientHello matches exactly the returned name value.
// Deprecated: This challenge type is unused in both draft-02 and RFC versions of ACME spec.
func (c *Client) TLSSNI02ChallengeCert(token string, opt ...CertOption) (cert tls.Certificate, name string, err error) {
b := sha256.Sum256([]byte(token))
h := hex.EncodeToString(b[:])
Expand Down Expand Up @@ -766,7 +800,7 @@ func (c *Client) TLSALPN01ChallengeCert(token, domain string, opt ...CertOption)
return tlsChallengeCert([]string{domain}, newOpt)
}

// doReg sends all types of registration requests.
// doReg sends all types of registration requests the old way (pre-RFC world).
// The type of request is identified by typ argument, which is a "resource"
// in the ACME spec terms.
//
Expand Down
12 changes: 7 additions & 5 deletions acme/acme_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -484,7 +484,7 @@ func TestGetAuthorization(t *testing.T) {
}))
defer ts.Close()

cl := Client{Key: testKeyEC}
cl := Client{Key: testKeyEC, DirectoryURL: ts.URL}
auth, err := cl.GetAuthorization(context.Background(), ts.URL)
if err != nil {
t.Fatal(err)
Expand Down Expand Up @@ -614,7 +614,7 @@ func runWaitAuthorization(ctx context.Context, t *testing.T, h http.HandlerFunc)
}
ch := make(chan res, 1)
go func() {
var client Client
var client = Client{DirectoryURL: ts.URL}
a, err := client.WaitAuthorization(ctx, ts.URL)
ch <- res{a, err}
}()
Expand Down Expand Up @@ -684,7 +684,7 @@ func TestPollChallenge(t *testing.T) {
}))
defer ts.Close()

cl := Client{Key: testKeyEC}
cl := Client{Key: testKeyEC, DirectoryURL: ts.URL}
chall, err := cl.GetChallenge(context.Background(), ts.URL)
if err != nil {
t.Fatal(err)
Expand Down Expand Up @@ -865,7 +865,8 @@ func TestFetchCert(t *testing.T) {
w.Write([]byte{count})
}))
defer ts.Close()
res, err := (&Client{}).FetchCert(context.Background(), ts.URL, true)
cl := &Client{dir: &Directory{}} // skip discovery
res, err := cl.FetchCert(context.Background(), ts.URL, true)
if err != nil {
t.Fatalf("FetchCert: %v", err)
}
Expand All @@ -887,7 +888,8 @@ func TestFetchCertRetry(t *testing.T) {
w.Write([]byte{1})
}))
defer ts.Close()
res, err := (&Client{}).FetchCert(context.Background(), ts.URL, false)
cl := &Client{dir: &Directory{}} // skip discovery
res, err := cl.FetchCert(context.Background(), ts.URL, false)
if err != nil {
t.Fatalf("FetchCert: %v", err)
}
Expand Down
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