package provisioner import ( "context" "crypto/x509" "encoding/pem" "net/http" "time" "github.com/pkg/errors" "github.com/smallstep/certificates/errs" "go.step.sm/crypto/jose" "go.step.sm/crypto/sshutil" "go.step.sm/crypto/x509util" ) // x5cPayload extends jwt.Claims with step attributes. type x5cPayload struct { jose.Claims SANs []string `json:"sans,omitempty"` Step *stepPayload `json:"step,omitempty"` chains [][]*x509.Certificate } // X5C is the default provisioner, an entity that can sign tokens necessary for // signature requests. type X5C struct { *base ID string `json:"-"` Type string `json:"type"` Name string `json:"name"` Roots []byte `json:"roots"` Claims *Claims `json:"claims,omitempty"` Options *Options `json:"options,omitempty"` claimer *Claimer audiences Audiences rootPool *x509.CertPool } // GetID returns the provisioner unique identifier. The name and credential id // should uniquely identify any X5C provisioner. func (p *X5C) GetID() string { if p.ID != "" { return p.ID } return p.GetIDForToken() } // GetIDForToken returns an identifier that will be used to load the provisioner // from a token. func (p *X5C) GetIDForToken() string { return "x5c/" + p.Name } // GetTokenID returns the identifier of the token. func (p *X5C) 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 jose.Claims if err = token.UnsafeClaimsWithoutVerification(&claims); err != nil { return "", errors.Wrap(err, "error verifying claims") } return claims.ID, nil } // GetName returns the name of the provisioner. func (p *X5C) GetName() string { return p.Name } // GetType returns the type of provisioner. func (p *X5C) GetType() Type { return TypeX5C } // GetEncryptedKey returns the base provisioner encrypted key if it's defined. func (p *X5C) GetEncryptedKey() (string, string, bool) { return "", "", false } // Init initializes and validates the fields of a X5C type. func (p *X5C) Init(config Config) error { switch { case p.Type == "": return errors.New("provisioner type cannot be empty") case p.Name == "": return errors.New("provisioner name cannot be empty") case len(p.Roots) == 0: return errors.New("provisioner root(s) cannot be empty") } p.rootPool = x509.NewCertPool() var ( block *pem.Block rest = p.Roots ) for rest != nil { block, rest = pem.Decode(rest) if block == nil { break } cert, err := x509.ParseCertificate(block.Bytes) if err != nil { return errors.Wrap(err, "error parsing x509 certificate from PEM block") } p.rootPool.AddCert(cert) } // Verify that at least one root was found. if len(p.rootPool.Subjects()) == 0 { return errors.Errorf("no x509 certificates found in roots attribute for provisioner '%s'", p.GetName()) } // Update claims with global ones var err error if p.claimer, err = NewClaimer(p.Claims, config.Claims); err != nil { return err } p.audiences = config.Audiences.WithFragment(p.GetIDForToken()) return nil } // authorizeToken performs common jwt authorization actions and returns the // claims for case specific downstream parsing. // e.g. a Sign request will auth/validate different fields than a Revoke request. func (p *X5C) authorizeToken(token string, audiences []string) (*x5cPayload, error) { jwt, err := jose.ParseSigned(token) if err != nil { return nil, errs.Wrap(http.StatusUnauthorized, err, "x5c.authorizeToken; error parsing x5c token") } verifiedChains, err := jwt.Headers[0].Certificates(x509.VerifyOptions{ Roots: p.rootPool, KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}, }) if err != nil { return nil, errs.Wrap(http.StatusUnauthorized, err, "x5c.authorizeToken; error verifying x5c certificate chain in token") } leaf := verifiedChains[0][0] if leaf.KeyUsage&x509.KeyUsageDigitalSignature == 0 { return nil, errs.Unauthorized("x5c.authorizeToken; certificate used to sign x5c token cannot be used for digital signature") } // Using the leaf certificates key to validate the claims accomplishes two // things: // 1. Asserts that the private key used to sign the token corresponds // to the public certificate in the `x5c` header of the token. // 2. Asserts that the claims are valid - have not been tampered with. var claims x5cPayload if err = jwt.Claims(leaf.PublicKey, &claims); err != nil { return nil, errs.Wrap(http.StatusUnauthorized, err, "x5c.authorizeToken; error parsing x5c claims") } // According to "rfc7519 JSON Web Token" acceptable skew should be no // more than a few minutes. if err = claims.ValidateWithLeeway(jose.Expected{ Issuer: p.Name, Time: time.Now().UTC(), }, time.Minute); err != nil { return nil, errs.Wrapf(http.StatusUnauthorized, err, "x5c.authorizeToken; invalid x5c claims") } // validate audiences with the defaults if !matchesAudience(claims.Audience, audiences) { return nil, errs.Unauthorized("x5c.authorizeToken; x5c token has invalid audience "+ "claim (aud); expected %s, but got %s", audiences, claims.Audience) } if claims.Subject == "" { return nil, errs.Unauthorized("x5c.authorizeToken; x5c token subject cannot be empty") } // Save the verified chains on the x5c payload object. claims.chains = verifiedChains 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. func (p *X5C) AuthorizeRevoke(ctx context.Context, token string) error { _, err := p.authorizeToken(token, p.audiences.Revoke) return errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeRevoke") } // AuthorizeSign validates the given token. func (p *X5C) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) { claims, err := p.authorizeToken(token, p.audiences.Sign) if err != nil { return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSign") } // NOTE: This is for backwards compatibility with older versions of cli // and certificates. Older versions added the token subject as the only SAN // in a CSR by default. if len(claims.SANs) == 0 { claims.SANs = []string{claims.Subject} } // Certificate templates data := x509util.CreateTemplateData(claims.Subject, claims.SANs) if v, err := unsafeParseSigned(token); err == nil { data.SetToken(v) } templateOptions, err := TemplateOptions(p.Options, data) if err != nil { return nil, errs.Wrap(http.StatusInternalServerError, err, "jwk.AuthorizeSign") } return []SignOption{ templateOptions, // modifiers / withOptions newProvisionerExtensionOption(TypeX5C, p.Name, ""), profileLimitDuration{p.claimer.DefaultTLSCertDuration(), claims.chains[0][0].NotBefore, claims.chains[0][0].NotAfter}, // validators commonNameValidator(claims.Subject), defaultSANsValidator(claims.SANs), defaultPublicKeyValidator{}, newValidityValidator(p.claimer.MinTLSCertDuration(), p.claimer.MaxTLSCertDuration()), }, nil } // AuthorizeRenew returns an error if the renewal is disabled. func (p *X5C) AuthorizeRenew(ctx context.Context, cert *x509.Certificate) error { if p.claimer.IsDisableRenewal() { return errs.Unauthorized("x5c.AuthorizeRenew; renew is disabled for x5c provisioner '%s'", p.GetName()) } return nil } // AuthorizeSSHSign returns the list of SignOption for a SignSSH request. func (p *X5C) AuthorizeSSHSign(ctx context.Context, token string) ([]SignOption, error) { if !p.claimer.IsSSHCAEnabled() { return nil, errs.Unauthorized("x5c.AuthorizeSSHSign; sshCA is disabled for x5c provisioner '%s'", p.GetName()) } claims, err := p.authorizeToken(token, p.audiences.SSHSign) if err != nil { return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSSHSign") } if claims.Step == nil || claims.Step.SSH == nil { return nil, errs.Unauthorized("x5c.AuthorizeSSHSign; x5c token must be an SSH provisioning token") } opts := claims.Step.SSH signOptions := []SignOption{ // validates user's SSHOptions with the ones in the token sshCertOptionsValidator(*opts), // validate users's KeyID is the token subject. sshCertOptionsValidator(SignSSHOptions{KeyID: claims.Subject}), } // Default template attributes. certType := sshutil.UserCert keyID := claims.Subject principals := []string{claims.Subject} // Use options in the token. if opts.CertType != "" { if certType, err = sshutil.CertTypeFromString(opts.CertType); err != nil { return nil, errs.BadRequestErr(err, err.Error()) } } if opts.KeyID != "" { keyID = opts.KeyID } if len(opts.Principals) > 0 { principals = opts.Principals } // Certificate templates. data := sshutil.CreateTemplateData(certType, keyID, principals) if v, err := unsafeParseSigned(token); err == nil { data.SetToken(v) } templateOptions, err := TemplateSSHOptions(p.Options, data) if err != nil { return nil, errs.Wrap(http.StatusInternalServerError, err, "x5c.AuthorizeSSHSign") } signOptions = append(signOptions, templateOptions) // Add modifiers from custom claims t := now() if !opts.ValidAfter.IsZero() { signOptions = append(signOptions, sshCertValidAfterModifier(opts.ValidAfter.RelativeTime(t).Unix())) } if !opts.ValidBefore.IsZero() { signOptions = append(signOptions, sshCertValidBeforeModifier(opts.ValidBefore.RelativeTime(t).Unix())) } return append(signOptions, // Checks the validity bounds, and set the validity if has not been set. &sshLimitDuration{p.claimer, claims.chains[0][0].NotAfter}, // Validate public key. &sshDefaultPublicKeyValidator{}, // Validate the validity period. &sshCertValidityValidator{p.claimer}, // Require all the fields in the SSH certificate &sshCertDefaultValidator{}, ), nil }