mirror of
https://github.com/smallstep/certificates.git
synced 2024-11-17 15:29:21 +00:00
299 lines
8.3 KiB
Go
299 lines
8.3 KiB
Go
package authority
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import (
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"crypto/rand"
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"encoding/binary"
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"net/http"
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"strings"
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"github.com/pkg/errors"
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"github.com/smallstep/certificates/authority/provisioner"
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"github.com/smallstep/certificates/templates"
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"github.com/smallstep/cli/crypto/randutil"
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"golang.org/x/crypto/ssh"
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)
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const (
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// SSHAddUserPrincipal is the principal that will run the add user command.
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// Defaults to "provisioner" but it can be changed in the configuration.
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SSHAddUserPrincipal = "provisioner"
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// SSHAddUserCommand is the default command to run to add a new user.
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// Defaults to "sudo useradd -m <principal>; nc -q0 localhost 22" but it can be changed in the
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// configuration. The string "<principal>" will be replace by the new
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// principal to add.
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SSHAddUserCommand = "sudo useradd -m <principal>; nc -q0 localhost 22"
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)
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// SSHKeys represents the SSH User and Host public keys.
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type SSHKeys struct {
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UserKey ssh.PublicKey
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HostKey ssh.PublicKey
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}
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// GetSSHKeys returns the SSH User and Host public keys.
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func (a *Authority) GetSSHKeys() (*SSHKeys, error) {
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var keys SSHKeys
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if a.sshCAUserCertSignKey != nil {
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keys.UserKey = a.sshCAUserCertSignKey.PublicKey()
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}
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if a.sshCAHostCertSignKey != nil {
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keys.HostKey = a.sshCAHostCertSignKey.PublicKey()
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}
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if keys.UserKey == nil && keys.HostKey == nil {
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return nil, &apiError{
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err: errors.New("getSSHKeys: ssh is not configured"),
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code: http.StatusNotFound,
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}
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}
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return &keys, nil
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}
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// GetSSHConfig returns rendered templates for clients (user) or servers (host).
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func (a *Authority) GetSSHConfig(typ string, data map[string]string) ([]templates.Output, error) {
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if a.sshCAUserCertSignKey == nil && a.sshCAHostCertSignKey == nil {
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return nil, &apiError{
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err: errors.New("getSSHConfig: ssh is not configured"),
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code: http.StatusNotFound,
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}
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}
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var ts []templates.Template
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switch typ {
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case provisioner.SSHUserCert:
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if a.config.Templates != nil && a.config.Templates.SSH != nil {
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ts = a.config.Templates.SSH.User
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}
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case provisioner.SSHHostCert:
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if a.config.Templates != nil && a.config.Templates.SSH != nil {
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ts = a.config.Templates.SSH.Host
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}
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default:
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return nil, &apiError{
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err: errors.Errorf("getSSHConfig: type %s is not valid", typ),
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code: http.StatusBadRequest,
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}
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}
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// Merge user and default data
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var mergedData map[string]interface{}
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if len(data) == 0 {
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mergedData = a.config.Templates.Data
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} else {
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mergedData = make(map[string]interface{}, len(a.config.Templates.Data)+1)
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mergedData["User"] = data
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for k, v := range a.config.Templates.Data {
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mergedData[k] = v
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}
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}
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// Render templates
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output := []templates.Output{}
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for _, t := range ts {
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o, err := t.Output(mergedData)
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if err != nil {
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return nil, err
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}
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output = append(output, o)
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}
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return output, nil
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}
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// SignSSH creates a signed SSH certificate with the given public key and options.
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func (a *Authority) SignSSH(key ssh.PublicKey, opts provisioner.SSHOptions, signOpts ...provisioner.SignOption) (*ssh.Certificate, error) {
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var mods []provisioner.SSHCertificateModifier
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var validators []provisioner.SSHCertificateValidator
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for _, op := range signOpts {
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switch o := op.(type) {
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// modify the ssh.Certificate
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case provisioner.SSHCertificateModifier:
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mods = append(mods, o)
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// modify the ssh.Certificate given the SSHOptions
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case provisioner.SSHCertificateOptionModifier:
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mods = append(mods, o.Option(opts))
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// validate the ssh.Certificate
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case provisioner.SSHCertificateValidator:
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validators = append(validators, o)
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// validate the given SSHOptions
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case provisioner.SSHCertificateOptionsValidator:
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if err := o.Valid(opts); err != nil {
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return nil, &apiError{err: err, code: http.StatusForbidden}
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}
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default:
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return nil, &apiError{
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err: errors.Errorf("signSSH: invalid extra option type %T", o),
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code: http.StatusInternalServerError,
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}
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}
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}
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nonce, err := randutil.ASCII(32)
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if err != nil {
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return nil, &apiError{err: err, code: http.StatusInternalServerError}
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}
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var serial uint64
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if err := binary.Read(rand.Reader, binary.BigEndian, &serial); err != nil {
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return nil, &apiError{
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err: errors.Wrap(err, "signSSH: error reading random number"),
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code: http.StatusInternalServerError,
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}
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}
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// Build base certificate with the key and some random values
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cert := &ssh.Certificate{
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Nonce: []byte(nonce),
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Key: key,
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Serial: serial,
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}
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// Use opts to modify the certificate
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if err := opts.Modify(cert); err != nil {
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return nil, &apiError{err: err, code: http.StatusForbidden}
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}
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// Use provisioner modifiers
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for _, m := range mods {
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if err := m.Modify(cert); err != nil {
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return nil, &apiError{err: err, code: http.StatusForbidden}
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}
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}
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// Get signer from authority keys
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var signer ssh.Signer
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switch cert.CertType {
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case ssh.UserCert:
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if a.sshCAUserCertSignKey == nil {
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return nil, &apiError{
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err: errors.New("signSSH: user certificate signing is not enabled"),
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code: http.StatusNotImplemented,
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}
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}
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signer = a.sshCAUserCertSignKey
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case ssh.HostCert:
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if a.sshCAHostCertSignKey == nil {
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return nil, &apiError{
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err: errors.New("signSSH: host certificate signing is not enabled"),
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code: http.StatusNotImplemented,
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}
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}
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signer = a.sshCAHostCertSignKey
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default:
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return nil, &apiError{
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err: errors.Errorf("signSSH: unexpected ssh certificate type: %d", cert.CertType),
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code: http.StatusInternalServerError,
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}
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}
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cert.SignatureKey = signer.PublicKey()
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// Get bytes for signing trailing the signature length.
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data := cert.Marshal()
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data = data[:len(data)-4]
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// Sign the certificate
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sig, err := signer.Sign(rand.Reader, data)
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if err != nil {
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return nil, &apiError{
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err: errors.Wrap(err, "signSSH: error signing certificate"),
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code: http.StatusInternalServerError,
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}
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}
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cert.Signature = sig
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// User provisioners validators
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for _, v := range validators {
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if err := v.Valid(cert); err != nil {
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return nil, &apiError{err: err, code: http.StatusForbidden}
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}
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}
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return cert, nil
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}
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// SignSSHAddUser signs a certificate that provisions a new user in a server.
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func (a *Authority) SignSSHAddUser(key ssh.PublicKey, subject *ssh.Certificate) (*ssh.Certificate, error) {
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if a.sshCAUserCertSignKey == nil {
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return nil, &apiError{
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err: errors.New("signSSHAddUser: user certificate signing is not enabled"),
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code: http.StatusNotImplemented,
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}
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}
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if subject.CertType != ssh.UserCert {
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return nil, &apiError{
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err: errors.New("signSSHProxy: certificate is not a user certificate"),
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code: http.StatusForbidden,
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}
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}
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if len(subject.ValidPrincipals) != 1 {
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return nil, &apiError{
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err: errors.New("signSSHProxy: certificate does not have only one principal"),
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code: http.StatusForbidden,
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}
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}
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nonce, err := randutil.ASCII(32)
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if err != nil {
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return nil, &apiError{err: err, code: http.StatusInternalServerError}
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}
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var serial uint64
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if err := binary.Read(rand.Reader, binary.BigEndian, &serial); err != nil {
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return nil, &apiError{
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err: errors.Wrap(err, "signSSHProxy: error reading random number"),
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code: http.StatusInternalServerError,
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}
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}
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signer := a.sshCAUserCertSignKey
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principal := subject.ValidPrincipals[0]
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addUserPrincipal := a.getAddUserPrincipal()
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cert := &ssh.Certificate{
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Nonce: []byte(nonce),
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Key: key,
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Serial: serial,
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CertType: ssh.UserCert,
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KeyId: principal + "-" + addUserPrincipal,
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ValidPrincipals: []string{addUserPrincipal},
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ValidAfter: subject.ValidAfter,
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ValidBefore: subject.ValidBefore,
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Permissions: ssh.Permissions{
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CriticalOptions: map[string]string{
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"force-command": a.getAddUserCommand(principal),
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},
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},
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SignatureKey: signer.PublicKey(),
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}
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// Get bytes for signing trailing the signature length.
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data := cert.Marshal()
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data = data[:len(data)-4]
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// Sign the certificate
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sig, err := signer.Sign(rand.Reader, data)
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if err != nil {
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return nil, err
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}
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cert.Signature = sig
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return cert, nil
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}
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func (a *Authority) getAddUserPrincipal() (cmd string) {
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if a.config.SSH.AddUserPrincipal == "" {
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return SSHAddUserPrincipal
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}
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return a.config.SSH.AddUserPrincipal
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}
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func (a *Authority) getAddUserCommand(principal string) string {
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var cmd string
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if a.config.SSH.AddUserCommand == "" {
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cmd = SSHAddUserCommand
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} else {
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cmd = a.config.SSH.AddUserCommand
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}
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return strings.Replace(cmd, "<principal>", principal, -1)
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}
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