279 lines
8.9 KiB
Go
279 lines
8.9 KiB
Go
package acme
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import (
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"context"
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"crypto"
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"crypto/sha256"
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"crypto/subtle"
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"crypto/tls"
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"encoding/asn1"
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"encoding/base64"
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"encoding/hex"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"net"
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"net/http"
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"net/url"
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"strings"
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"time"
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"go.step.sm/crypto/jose"
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)
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// Challenge represents an ACME response Challenge type.
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type Challenge struct {
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ID string `json:"-"`
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AccountID string `json:"-"`
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AuthorizationID string `json:"-"`
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Value string `json:"-"`
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Type string `json:"type"`
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Status Status `json:"status"`
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Token string `json:"token"`
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ValidatedAt string `json:"validated,omitempty"`
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URL string `json:"url"`
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Error *Error `json:"error,omitempty"`
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}
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// ToLog enables response logging.
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func (ch *Challenge) ToLog() (interface{}, error) {
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b, err := json.Marshal(ch)
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if err != nil {
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return nil, WrapErrorISE(err, "error marshaling challenge for logging")
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}
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return string(b), nil
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}
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// Validate attempts to validate the challenge. Stores changes to the Challenge
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// type using the DB interface.
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// satisfactorily validated, the 'status' and 'validated' attributes are
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// updated.
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func (ch *Challenge) Validate(ctx context.Context, db DB, jwk *jose.JSONWebKey, vo *ValidateChallengeOptions) error {
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// If already valid or invalid then return without performing validation.
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if ch.Status != StatusPending {
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return nil
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}
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switch ch.Type {
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case "http-01":
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return http01Validate(ctx, ch, db, jwk, vo)
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case "dns-01":
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return dns01Validate(ctx, ch, db, jwk, vo)
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case "tls-alpn-01":
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return tlsalpn01Validate(ctx, ch, db, jwk, vo)
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default:
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return NewErrorISE("unexpected challenge type '%s'", ch.Type)
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}
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}
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func http01Validate(ctx context.Context, ch *Challenge, db DB, jwk *jose.JSONWebKey, vo *ValidateChallengeOptions) error {
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url := &url.URL{Scheme: "http", Host: ch.Value, Path: fmt.Sprintf("/.well-known/acme-challenge/%s", ch.Token)}
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resp, err := vo.HTTPGet(url.String())
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if err != nil {
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return storeError(ctx, db, ch, false, WrapError(ErrorConnectionType, err,
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"error doing http GET for url %s", url))
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}
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defer resp.Body.Close()
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if resp.StatusCode >= 400 {
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return storeError(ctx, db, ch, false, NewError(ErrorConnectionType,
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"error doing http GET for url %s with status code %d", url, resp.StatusCode))
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}
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body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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return WrapErrorISE(err, "error reading "+
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"response body for url %s", url)
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}
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keyAuth := strings.TrimSpace(string(body))
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expected, err := KeyAuthorization(ch.Token, jwk)
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if err != nil {
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return err
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}
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if keyAuth != expected {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"keyAuthorization does not match; expected %s, but got %s", expected, keyAuth))
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}
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// Update and store the challenge.
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ch.Status = StatusValid
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ch.Error = nil
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ch.ValidatedAt = clock.Now().Format(time.RFC3339)
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if err = db.UpdateChallenge(ctx, ch); err != nil {
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return WrapErrorISE(err, "error updating challenge")
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}
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return nil
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}
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func tlsalpn01Validate(ctx context.Context, ch *Challenge, db DB, jwk *jose.JSONWebKey, vo *ValidateChallengeOptions) error {
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config := &tls.Config{
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NextProtos: []string{"acme-tls/1"},
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// https://tools.ietf.org/html/rfc8737#section-4
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// ACME servers that implement "acme-tls/1" MUST only negotiate TLS 1.2
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// [RFC5246] or higher when connecting to clients for validation.
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MinVersion: tls.VersionTLS12,
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ServerName: ch.Value,
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InsecureSkipVerify: true, // we expect a self-signed challenge certificate
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}
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hostPort := net.JoinHostPort(ch.Value, "443")
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conn, err := vo.TLSDial("tcp", hostPort, config)
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if err != nil {
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return storeError(ctx, db, ch, false, WrapError(ErrorConnectionType, err,
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"error doing TLS dial for %s", hostPort))
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}
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defer conn.Close()
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cs := conn.ConnectionState()
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certs := cs.PeerCertificates
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if len(certs) == 0 {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"%s challenge for %s resulted in no certificates", ch.Type, ch.Value))
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}
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if cs.NegotiatedProtocol != "acme-tls/1" {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"cannot negotiate ALPN acme-tls/1 protocol for tls-alpn-01 challenge"))
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}
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leafCert := certs[0]
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if len(leafCert.DNSNames) != 1 || !strings.EqualFold(leafCert.DNSNames[0], ch.Value) {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: leaf certificate must contain a single DNS name, %v", ch.Value))
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}
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idPeAcmeIdentifier := asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 31}
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idPeAcmeIdentifierV1Obsolete := asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 1, 30, 1}
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foundIDPeAcmeIdentifierV1Obsolete := false
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keyAuth, err := KeyAuthorization(ch.Token, jwk)
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if err != nil {
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return err
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}
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hashedKeyAuth := sha256.Sum256([]byte(keyAuth))
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for _, ext := range leafCert.Extensions {
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if idPeAcmeIdentifier.Equal(ext.Id) {
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if !ext.Critical {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: acmeValidationV1 extension not critical"))
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}
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var extValue []byte
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rest, err := asn1.Unmarshal(ext.Value, &extValue)
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if err != nil || len(rest) > 0 || len(hashedKeyAuth) != len(extValue) {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: malformed acmeValidationV1 extension value"))
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}
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if subtle.ConstantTimeCompare(hashedKeyAuth[:], extValue) != 1 {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: "+
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"expected acmeValidationV1 extension value %s for this challenge but got %s",
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hex.EncodeToString(hashedKeyAuth[:]), hex.EncodeToString(extValue)))
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}
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ch.Status = StatusValid
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ch.Error = nil
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ch.ValidatedAt = clock.Now().Format(time.RFC3339)
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if err = db.UpdateChallenge(ctx, ch); err != nil {
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return WrapErrorISE(err, "tlsalpn01ValidateChallenge - error updating challenge")
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}
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return nil
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}
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if idPeAcmeIdentifierV1Obsolete.Equal(ext.Id) {
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foundIDPeAcmeIdentifierV1Obsolete = true
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}
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}
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if foundIDPeAcmeIdentifierV1Obsolete {
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: obsolete id-pe-acmeIdentifier in acmeValidationV1 extension"))
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}
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return storeError(ctx, db, ch, true, NewError(ErrorRejectedIdentifierType,
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"incorrect certificate for tls-alpn-01 challenge: missing acmeValidationV1 extension"))
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}
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func dns01Validate(ctx context.Context, ch *Challenge, db DB, jwk *jose.JSONWebKey, vo *ValidateChallengeOptions) error {
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// Normalize domain for wildcard DNS names
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// This is done to avoid making TXT lookups for domains like
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// _acme-challenge.*.example.com
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// Instead perform txt lookup for _acme-challenge.example.com
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domain := strings.TrimPrefix(ch.Value, "*.")
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txtRecords, err := vo.LookupTxt("_acme-challenge." + domain)
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if err != nil {
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return storeError(ctx, db, ch, false, WrapError(ErrorDNSType, err,
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"error looking up TXT records for domain %s", domain))
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}
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expectedKeyAuth, err := KeyAuthorization(ch.Token, jwk)
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if err != nil {
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return err
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}
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h := sha256.Sum256([]byte(expectedKeyAuth))
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expected := base64.RawURLEncoding.EncodeToString(h[:])
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var found bool
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for _, r := range txtRecords {
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if r == expected {
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found = true
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break
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}
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}
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if !found {
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return storeError(ctx, db, ch, false, NewError(ErrorRejectedIdentifierType,
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"keyAuthorization does not match; expected %s, but got %s", expectedKeyAuth, txtRecords))
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}
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// Update and store the challenge.
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ch.Status = StatusValid
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ch.Error = nil
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ch.ValidatedAt = clock.Now().Format(time.RFC3339)
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if err = db.UpdateChallenge(ctx, ch); err != nil {
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return WrapErrorISE(err, "error updating challenge")
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}
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return nil
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}
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// KeyAuthorization creates the ACME key authorization value from a token
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// and a jwk.
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func KeyAuthorization(token string, jwk *jose.JSONWebKey) (string, error) {
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thumbprint, err := jwk.Thumbprint(crypto.SHA256)
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if err != nil {
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return "", WrapErrorISE(err, "error generating JWK thumbprint")
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}
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encPrint := base64.RawURLEncoding.EncodeToString(thumbprint)
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return fmt.Sprintf("%s.%s", token, encPrint), nil
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}
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// storeError the given error to an ACME error and saves using the DB interface.
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func storeError(ctx context.Context, db DB, ch *Challenge, markInvalid bool, err *Error) error {
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ch.Error = err
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if markInvalid {
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ch.Status = StatusInvalid
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}
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if err := db.UpdateChallenge(ctx, ch); err != nil {
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return WrapErrorISE(err, "failure saving error to acme challenge")
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}
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return nil
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}
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type httpGetter func(string) (*http.Response, error)
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type lookupTxt func(string) ([]string, error)
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type tlsDialer func(network, addr string, config *tls.Config) (*tls.Conn, error)
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// ValidateChallengeOptions are ACME challenge validator functions.
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type ValidateChallengeOptions struct {
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HTTPGet httpGetter
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LookupTxt lookupTxt
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TLSDial tlsDialer
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}
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