smallstep-certificates/authority/authorize.go

package authority

import (
	"crypto/x509"
	"net/http"
	"strings"
	"time"

	"github.com/pkg/errors"
	"github.com/smallstep/certificates/authority/provisioner"
	"github.com/smallstep/cli/jose"
)

type idUsed struct {
	UsedAt  int64  `json:"ua,omitempty"`
	Subject string `json:"sub,omitempty"`
}

// Claims extends jose.Claims with step attributes.
type Claims struct {
	jose.Claims
	SANs  []string `json:"sans,omitempty"`
	Email string   `json:"email,omitempty"`
	Nonce string   `json:"nonce,omitempty"`
}

// authorizeToken parses the token and returns the provisioner used to generate
// the token. This method enforces the One-Time use policy (tokens can only be
// used once).
func (a *Authority) authorizeToken(ott string) (provisioner.Interface, error) {
	var errContext = map[string]interface{}{"ott": ott}

	// Validate payload
	token, err := jose.ParseSigned(ott)
	if err != nil {
		return nil, &apiError{errors.Wrapf(err, "authorizeToken: error parsing token"),
			http.StatusUnauthorized, errContext}
	}

	// 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 Claims
	if err = token.UnsafeClaimsWithoutVerification(&claims); err != nil {
		return nil, &apiError{errors.Wrap(err, "authorizeToken"), http.StatusUnauthorized, errContext}
	}

	// TODO: use new persistence layer abstraction.
	// Do not accept tokens issued before the start of the ca.
	// This check is meant as a stopgap solution to the current lack of a persistence layer.
	if a.config.AuthorityConfig != nil && !a.config.AuthorityConfig.DisableIssuedAtCheck {
		if claims.IssuedAt != nil && claims.IssuedAt.Time().Before(a.startTime) {
			return nil, &apiError{errors.New("authorizeToken: token issued before the bootstrap of certificate authority"),
				http.StatusUnauthorized, errContext}
		}
	}

	// This method will also validate the audiences for JWK provisioners.
	p, ok := a.provisioners.LoadByToken(token, &claims.Claims)
	if !ok {
		return nil, &apiError{
			errors.Errorf("authorizeToken: provisioner not found or invalid audience (%s)", strings.Join(claims.Audience, ", ")),
			http.StatusUnauthorized, errContext}
	}

	// Store the token to protect against reuse.
	var reuseKey string
	switch p.GetType() {
	case provisioner.TypeJWK:
		reuseKey = claims.ID
	case provisioner.TypeOIDC:
		reuseKey = claims.Nonce
	}
	if reuseKey != "" {
		if _, ok := a.ottMap.LoadOrStore(reuseKey, &idUsed{
			UsedAt:  time.Now().Unix(),
			Subject: claims.Subject,
		}); ok {
			return nil, &apiError{errors.Errorf("authorizeToken: token already used"), http.StatusUnauthorized, errContext}
		}
	}

	return p, nil
}

// Authorize is a passthrough to AuthorizeSign.
// NOTE: Authorize will be deprecated in a future release. Please use the
// context specific Authorize[Sign|Revoke|etc.] going forwards.
func (a *Authority) Authorize(ott string) ([]provisioner.SignOption, error) {
	return a.AuthorizeSign(ott)
}

// AuthorizeSign authorizes a signature request by validating and authenticating
// a OTT that must be sent w/ the request.
func (a *Authority) AuthorizeSign(ott string) ([]provisioner.SignOption, error) {
	var errContext = context{"ott": ott}

	p, err := a.authorizeToken(ott)
	if err != nil {
		return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
	}

	// Call the provisioner AuthorizeSign method to apply provisioner specific
	// auth claims and get the signing options.
	opts, err := p.AuthorizeSign(ott)
	if err != nil {
		return nil, &apiError{errors.Wrap(err, "authorizeSign"), http.StatusUnauthorized, errContext}
	}

	return opts, nil
}

// authorizeRevoke authorizes a revocation request by validating and authenticating
// the RevokeOptions POSTed with the request.
// Returns a tuple of the provisioner ID and error, if one occurred.
func (a *Authority) authorizeRevoke(opts *RevokeOptions) (p provisioner.Interface, err error) {
	if opts.MTLS {
		if opts.Crt.SerialNumber.String() != opts.Serial {
			return nil, errors.New("authorizeRevoke: serial number in certificate different than body")
		}
		// Load the Certificate provisioner if one exists.
		p, err = a.LoadProvisionerByCertificate(opts.Crt)
		if err != nil {
			return nil, errors.Wrap(err, "authorizeRevoke")
		}
	} else {
		// Gets the token provisioner and validates common token fields.
		p, err = a.authorizeToken(opts.OTT)
		if err != nil {
			return nil, errors.Wrap(err, "authorizeRevoke")
		}

		// Call the provisioner AuthorizeRevoke to apply provisioner specific auth claims.
		err = p.AuthorizeRevoke(opts.OTT)
		if err != nil {
			return nil, errors.Wrap(err, "authorizeRevoke")
		}
	}
	return
}

// authorizeRenewal tries to locate the step provisioner extension, and checks
// if for the configured provisioner, the renewal is enabled or not. If the
// extra extension cannot be found, authorize the renewal by default.
//
// TODO(mariano): should we authorize by default?
func (a *Authority) authorizeRenewal(crt *x509.Certificate) error {
	errContext := map[string]interface{}{"serialNumber": crt.SerialNumber.String()}

	// Check the passive revocation table.
	isRevoked, err := a.db.IsRevoked(crt.SerialNumber.String())
	if err != nil {
		return &apiError{
			err:     errors.Wrap(err, "renew"),
			code:    http.StatusInternalServerError,
			context: errContext,
		}
	}
	if isRevoked {
		return &apiError{
			err:     errors.New("renew: certificate has been revoked"),
			code:    http.StatusUnauthorized,
			context: errContext,
		}
	}

	p, ok := a.provisioners.LoadByCertificate(crt)
	if !ok {
		return &apiError{
			err:     errors.New("renew: provisioner not found"),
			code:    http.StatusUnauthorized,
			context: errContext,
		}
	}
	if err := p.AuthorizeRenewal(crt); err != nil {
		return &apiError{
			err:     errors.Wrap(err, "renew"),
			code:    http.StatusUnauthorized,
			context: errContext,
		}
	}
	return nil
}