certificates/authority/provisioner/oidc.go

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package provisioner
import (
"context"
"crypto/x509"
"encoding/json"
"net/http"
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"strings"
"time"
"github.com/pkg/errors"
"github.com/smallstep/cli/jose"
)
// openIDConfiguration contains the necessary properties in the
// `/.well-known/openid-configuration` document.
type openIDConfiguration struct {
Issuer string `json:"issuer"`
JWKSetURI string `json:"jwks_uri"`
}
// Validate validates the values in a well-known OpenID configuration endpoint.
func (c openIDConfiguration) Validate() error {
switch {
case c.Issuer == "":
return errors.New("issuer cannot be empty")
case c.JWKSetURI == "":
return errors.New("jwks_uri cannot be empty")
default:
return nil
}
}
// openIDPayload represents the fields on the id_token JWT payload.
type openIDPayload struct {
jose.Claims
AtHash string `json:"at_hash"`
AuthorizedParty string `json:"azp"`
Email string `json:"email"`
EmailVerified bool `json:"email_verified"`
Hd string `json:"hd"`
Nonce string `json:"nonce"`
Groups []string `json:"groups"`
}
// OIDC represents an OAuth 2.0 OpenID Connect provider.
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//
// ClientSecret is mandatory, but it can be an empty string.
type OIDC struct {
Type string `json:"type"`
Name string `json:"name"`
ClientID string `json:"clientID"`
ClientSecret string `json:"clientSecret"`
ConfigurationEndpoint string `json:"configurationEndpoint"`
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Admins []string `json:"admins,omitempty"`
Domains []string `json:"domains,omitempty"`
Groups []string `json:"groups,omitempty"`
Claims *Claims `json:"claims,omitempty"`
configuration openIDConfiguration
keyStore *keyStore
claimer *Claimer
}
// IsAdmin returns true if the given email is in the Admins whitelist, false
// otherwise.
func (o *OIDC) IsAdmin(email string) bool {
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email = sanitizeEmail(email)
for _, e := range o.Admins {
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if email == sanitizeEmail(e) {
return true
}
}
return false
}
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func sanitizeEmail(email string) string {
if i := strings.LastIndex(email, "@"); i >= 0 {
email = email[:i] + strings.ToLower(email[i:])
}
return email
}
// GetID returns the provisioner unique identifier, the OIDC provisioner the
// uses the clientID for this.
func (o *OIDC) GetID() string {
return o.ClientID
}
// GetTokenID returns the provisioner unique identifier, the OIDC provisioner the
// uses the clientID for this.
func (o *OIDC) GetTokenID(ott string) (string, error) {
// Validate payload
token, err := jose.ParseSigned(ott)
if err != nil {
return "", errors.Wrap(err, "error parsing token")
}
// Get claims w/out verification. We need to look up the provisioner
// key in order to verify the claims and we need the issuer from the claims
// before we can look up the provisioner.
var claims openIDPayload
if err = token.UnsafeClaimsWithoutVerification(&claims); err != nil {
return "", errors.Wrap(err, "error verifying claims")
}
return claims.Nonce, nil
}
// GetName returns the name of the provisioner.
func (o *OIDC) GetName() string {
return o.Name
}
// GetType returns the type of provisioner.
func (o *OIDC) GetType() Type {
return TypeOIDC
}
// GetEncryptedKey is not available in an OIDC provisioner.
func (o *OIDC) GetEncryptedKey() (kid string, key string, ok bool) {
return "", "", false
}
// Init validates and initializes the OIDC provider.
func (o *OIDC) Init(config Config) (err error) {
switch {
case o.Type == "":
return errors.New("type cannot be empty")
case o.Name == "":
return errors.New("name cannot be empty")
case o.ClientID == "":
return errors.New("clientID cannot be empty")
case o.ConfigurationEndpoint == "":
return errors.New("configurationEndpoint cannot be empty")
}
// Update claims with global ones
if o.claimer, err = NewClaimer(o.Claims, config.Claims); err != nil {
return err
}
// Decode and validate openid-configuration endpoint
if err := getAndDecode(o.ConfigurationEndpoint, &o.configuration); err != nil {
return err
}
if err := o.configuration.Validate(); err != nil {
return errors.Wrapf(err, "error parsing %s", o.ConfigurationEndpoint)
}
// Get JWK key set
o.keyStore, err = newKeyStore(o.configuration.JWKSetURI)
if err != nil {
return err
}
return nil
}
// ValidatePayload validates the given token payload.
func (o *OIDC) ValidatePayload(p openIDPayload) error {
// According to "rfc7519 JSON Web Token" acceptable skew should be no more
// than a few minutes.
if err := p.ValidateWithLeeway(jose.Expected{
Issuer: o.configuration.Issuer,
Audience: jose.Audience{o.ClientID},
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Time: time.Now().UTC(),
}, time.Minute); err != nil {
return errors.Wrap(err, "failed to validate payload")
}
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// Validate azp if present
if p.AuthorizedParty != "" && p.AuthorizedParty != o.ClientID {
return errors.New("failed to validate payload: invalid azp")
}
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// Enforce an email claim
if p.Email == "" {
return errors.New("failed to validate payload: email not found")
}
// Validate domains (case-insensitive)
if !o.IsAdmin(p.Email) && len(o.Domains) > 0 {
email := sanitizeEmail(p.Email)
var found bool
for _, d := range o.Domains {
if strings.HasSuffix(email, "@"+strings.ToLower(d)) {
found = true
break
}
}
if !found {
return errors.New("failed to validate payload: email is not allowed")
}
}
// Filter by oidc group claim
if len(o.Groups) > 0 {
var found bool
for _, group := range o.Groups {
for _, g := range p.Groups {
if g == group {
found = true
break
}
}
}
if !found {
return errors.New("validation failed: invalid group")
}
}
return nil
}
// authorizeToken applies the most common provisioner authorization claims,
// leaving the rest to context specific methods.
func (o *OIDC) authorizeToken(token string) (*openIDPayload, error) {
jwt, err := jose.ParseSigned(token)
if err != nil {
return nil, errors.Wrapf(err, "error parsing token")
}
// Parse claims to get the kid
var claims openIDPayload
if err := jwt.UnsafeClaimsWithoutVerification(&claims); err != nil {
return nil, errors.Wrap(err, "error parsing claims")
}
found := false
kid := jwt.Headers[0].KeyID
keys := o.keyStore.Get(kid)
for _, key := range keys {
if err := jwt.Claims(key, &claims); err == nil {
found = true
break
}
}
if !found {
return nil, errors.New("cannot validate token")
}
if err := o.ValidatePayload(claims); err != nil {
return nil, err
}
return &claims, nil
}
// AuthorizeRevoke returns an error if the provisioner does not have rights to
// revoke the certificate with serial number in the `sub` property.
// Only tokens generated by an admin have the right to revoke a certificate.
func (o *OIDC) AuthorizeRevoke(token string) error {
claims, err := o.authorizeToken(token)
if err != nil {
return err
}
// Only admins can revoke certificates.
if o.IsAdmin(claims.Email) {
return nil
}
return errors.New("cannot revoke with non-admin token")
}
// AuthorizeSign validates the given token.
func (o *OIDC) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) {
claims, err := o.authorizeToken(token)
if err != nil {
return nil, err
}
// Check for the sign ssh method, default to sign X.509
if m := MethodFromContext(ctx); m == SignSSHMethod {
return o.authorizeSSHSign(claims)
}
// Admins should be able to authorize any SAN
if o.IsAdmin(claims.Email) {
return []SignOption{
profileDefaultDuration(o.claimer.DefaultTLSCertDuration()),
newProvisionerExtensionOption(TypeOIDC, o.Name, o.ClientID),
newValidityValidator(o.claimer.MinTLSCertDuration(), o.claimer.MaxTLSCertDuration()),
}, nil
}
return []SignOption{
emailOnlyIdentity(claims.Email),
profileDefaultDuration(o.claimer.DefaultTLSCertDuration()),
newProvisionerExtensionOption(TypeOIDC, o.Name, o.ClientID),
newValidityValidator(o.claimer.MinTLSCertDuration(), o.claimer.MaxTLSCertDuration()),
}, nil
}
// AuthorizeRenewal returns an error if the renewal is disabled.
func (o *OIDC) AuthorizeRenewal(cert *x509.Certificate) error {
if o.claimer.IsDisableRenewal() {
return errors.Errorf("renew is disabled for provisioner %s", o.GetID())
}
return nil
}
// authorizeSSHSign returns the list of SignOption for a SignSSH request.
func (o *OIDC) authorizeSSHSign(claims *openIDPayload) ([]SignOption, error) {
signOptions := []SignOption{
// set the key id to the token subject
sshCertificateKeyIDModifier(claims.Email),
}
name := SanitizeSSHUserPrincipal(claims.Email)
if !sshUserRegex.MatchString(name) {
return nil, errors.Errorf("invalid principal '%s' from email address '%s'", name, claims.Email)
}
// Admin users will default to user + name but they can be changed by the
// user options. Non-admins are only able to sign user certificates.
defaults := SSHOptions{
CertType: SSHUserCert,
Principals: []string{name},
}
if !o.IsAdmin(claims.Email) {
signOptions = append(signOptions, sshCertificateOptionsValidator(defaults))
}
// Default to a user with name as principal if not set
signOptions = append(signOptions, sshCertificateDefaultsModifier(defaults))
return append(signOptions,
// set the default extensions
&sshDefaultExtensionModifier{},
// checks the validity bounds, and set the validity if has not been set
&sshCertificateValidityModifier{o.claimer},
// require all the fields in the SSH certificate
&sshCertificateDefaultValidator{},
), nil
}
func getAndDecode(uri string, v interface{}) error {
resp, err := http.Get(uri)
if err != nil {
return errors.Wrapf(err, "failed to connect to %s", uri)
}
defer resp.Body.Close()
if err := json.NewDecoder(resp.Body).Decode(v); err != nil {
return errors.Wrapf(err, "error reading %s", uri)
}
return nil
}