smallstep-certificates/authority/provisioner/provisioner.go

package provisioner

import (
	"context"
	"crypto/x509"
	"encoding/json"
	"net/url"
	"regexp"
	"strings"

	"github.com/pkg/errors"
	"github.com/smallstep/certificates/db"
	"github.com/smallstep/certificates/errs"
	"golang.org/x/crypto/ssh"
)

// Interface is the interface that all provisioner types must implement.
type Interface interface {
	GetID() string
	GetTokenID(token string) (string, error)
	GetName() string
	GetType() Type
	GetEncryptedKey() (kid string, key string, ok bool)
	Init(config Config) error
	AuthorizeSign(ctx context.Context, token string) ([]SignOption, error)
	AuthorizeRevoke(ctx context.Context, token string) error
	AuthorizeRenew(ctx context.Context, cert *x509.Certificate) error
	AuthorizeSSHSign(ctx context.Context, token string) ([]SignOption, error)
	AuthorizeSSHRevoke(ctx context.Context, token string) error
	AuthorizeSSHRenew(ctx context.Context, token string) (*ssh.Certificate, error)
	AuthorizeSSHRekey(ctx context.Context, token string) (*ssh.Certificate, []SignOption, error)
}

// Audiences stores all supported audiences by request type.
type Audiences struct {
	Sign      []string
	Revoke    []string
	SSHSign   []string
	SSHRevoke []string
	SSHRenew  []string
	SSHRekey  []string
}

// All returns all supported audiences across all request types in one list.
func (a Audiences) All() (auds []string) {
	auds = a.Sign
	auds = append(auds, a.Revoke...)
	auds = append(auds, a.SSHSign...)
	auds = append(auds, a.SSHRevoke...)
	auds = append(auds, a.SSHRenew...)
	auds = append(auds, a.SSHRekey...)
	return
}

// WithFragment returns a copy of audiences where the url audiences contains the
// given fragment.
func (a Audiences) WithFragment(fragment string) Audiences {
	ret := Audiences{
		Sign:      make([]string, len(a.Sign)),
		Revoke:    make([]string, len(a.Revoke)),
		SSHSign:   make([]string, len(a.SSHSign)),
		SSHRevoke: make([]string, len(a.SSHRevoke)),
		SSHRenew:  make([]string, len(a.SSHRenew)),
		SSHRekey:  make([]string, len(a.SSHRekey)),
	}
	for i, s := range a.Sign {
		if u, err := url.Parse(s); err == nil {
			ret.Sign[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.Sign[i] = s
		}
	}
	for i, s := range a.Revoke {
		if u, err := url.Parse(s); err == nil {
			ret.Revoke[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.Revoke[i] = s
		}
	}
	for i, s := range a.SSHSign {
		if u, err := url.Parse(s); err == nil {
			ret.SSHSign[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.SSHSign[i] = s
		}
	}
	for i, s := range a.SSHRevoke {
		if u, err := url.Parse(s); err == nil {
			ret.SSHRevoke[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.SSHRevoke[i] = s
		}
	}
	for i, s := range a.SSHRenew {
		if u, err := url.Parse(s); err == nil {
			ret.SSHRenew[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.SSHRenew[i] = s
		}
	}
	for i, s := range a.SSHRekey {
		if u, err := url.Parse(s); err == nil {
			ret.SSHRekey[i] = u.ResolveReference(&url.URL{Fragment: fragment}).String()
		} else {
			ret.SSHRekey[i] = s
		}
	}
	return ret
}

// generateSignAudience generates a sign audience with the format
// https://<host>/1.0/sign#provisionerID
func generateSignAudience(caURL string, provisionerID string) (string, error) {
	u, err := url.Parse(caURL)
	if err != nil {
		return "", errors.Wrapf(err, "error parsing %s", caURL)
	}
	return u.ResolveReference(&url.URL{Path: "/1.0/sign", Fragment: provisionerID}).String(), nil
}

// Type indicates the provisioner Type.
type Type int

const (
	noopType Type = 0
	// TypeJWK is used to indicate the JWK provisioners.
	TypeJWK Type = 1
	// TypeOIDC is used to indicate the OIDC provisioners.
	TypeOIDC Type = 2
	// TypeGCP is used to indicate the GCP provisioners.
	TypeGCP Type = 3
	// TypeAWS is used to indicate the AWS provisioners.
	TypeAWS Type = 4
	// TypeAzure is used to indicate the Azure provisioners.
	TypeAzure Type = 5
	// TypeACME is used to indicate the ACME provisioners.
	TypeACME Type = 6
	// TypeX5C is used to indicate the X5C provisioners.
	TypeX5C Type = 7
	// TypeK8sSA is used to indicate the X5C provisioners.
	TypeK8sSA Type = 8
	// TypeSSHPOP is used to indicate the SSHPOP provisioners.
	TypeSSHPOP Type = 9
)

// String returns the string representation of the type.
func (t Type) String() string {
	switch t {
	case TypeJWK:
		return "JWK"
	case TypeOIDC:
		return "OIDC"
	case TypeGCP:
		return "GCP"
	case TypeAWS:
		return "AWS"
	case TypeAzure:
		return "Azure"
	case TypeACME:
		return "ACME"
	case TypeX5C:
		return "X5C"
	case TypeK8sSA:
		return "K8sSA"
	case TypeSSHPOP:
		return "SSHPOP"
	default:
		return ""
	}
}

// SSHKeys represents the SSH User and Host public keys.
type SSHKeys struct {
	UserKeys []ssh.PublicKey
	HostKeys []ssh.PublicKey
}

// Config defines the default parameters used in the initialization of
// provisioners.
type Config struct {
	// Claims are the default claims.
	Claims Claims
	// Audiences are the audiences used in the default provisioner, (JWK).
	Audiences Audiences
	// DB is the interface to the authority DB client.
	DB db.AuthDB
	// SSHKeys are the root SSH public keys
	SSHKeys *SSHKeys
	// GetIdentityFunc is a function that returns an identity that will be
	// used by the provisioner to populate certificate attributes.
	GetIdentityFunc GetIdentityFunc
}

type provisioner struct {
	Type string `json:"type"`
}

// List represents a list of provisioners.
type List []Interface

// UnmarshalJSON implements json.Unmarshaler and allows to unmarshal a list of a
// interfaces into the right type.
func (l *List) UnmarshalJSON(data []byte) error {
	ps := []json.RawMessage{}
	if err := json.Unmarshal(data, &ps); err != nil {
		return errors.Wrap(err, "error unmarshaling provisioner list")
	}

	*l = List{}
	for _, data := range ps {
		var typ provisioner
		if err := json.Unmarshal(data, &typ); err != nil {
			return errors.Errorf("error unmarshaling provisioner")
		}
		var p Interface
		switch strings.ToLower(typ.Type) {
		case "jwk":
			p = &JWK{}
		case "oidc":
			p = &OIDC{}
		case "gcp":
			p = &GCP{}
		case "aws":
			p = &AWS{}
		case "azure":
			p = &Azure{}
		case "acme":
			p = &ACME{}
		case "x5c":
			p = &X5C{}
		case "k8ssa":
			p = &K8sSA{}
		case "sshpop":
			p = &SSHPOP{}
		default:
			// Skip unsupported provisioners. A client using this method may be
			// compiled with a version of smallstep/certificates that does not
			// support a specific provisioner type. If we don't skip unknown
			// provisioners, a client encountering an unknown provisioner will
			// break. Rather than break the client, we skip the provisioner.
			// TODO: accept a pluggable logger (depending on client) that can
			// warn the user that an unknown provisioner was found and suggest
			// that the user update their client's dependency on
			// step/certificates and recompile.
			continue
		}
		if err := json.Unmarshal(data, p); err != nil {
			return errors.Wrap(err, "error unmarshaling provisioner")
		}
		*l = append(*l, p)
	}

	return nil
}

var sshUserRegex = regexp.MustCompile("^[a-z][-a-z0-9_]*$")

// SanitizeSSHUserPrincipal grabs an email or a string with the format
// local@domain and returns a sanitized version of the local, valid to be used
// as a user name. If the email starts with a letter between a and z, the
// resulting string will match the regular expression `^[a-z][-a-z0-9_]*$`.
func SanitizeSSHUserPrincipal(email string) string {
	if i := strings.LastIndex(email, "@"); i >= 0 {
		email = email[:i]
	}
	return strings.Map(func(r rune) rune {
		switch {
		case r >= 'a' && r <= 'z':
			return r
		case r >= '0' && r <= '9':
			return r
		case r == '-':
			return '-'
		case r == '.': // drop dots
			return -1
		default:
			return '_'
		}
	}, strings.ToLower(email))
}

type base struct{}

// AuthorizeSign returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for signing x509 Certificates.
func (b *base) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) {
	return nil, errs.Unauthorized("provisioner.AuthorizeSign not implemented")
}

// AuthorizeRevoke returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for revoking x509 Certificates.
func (b *base) AuthorizeRevoke(ctx context.Context, token string) error {
	return errs.Unauthorized("provisioner.AuthorizeRevoke not implemented")
}

// AuthorizeRenew returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for renewing x509 Certificates.
func (b *base) AuthorizeRenew(ctx context.Context, cert *x509.Certificate) error {
	return errs.Unauthorized("provisioner.AuthorizeRenew not implemented")
}

// AuthorizeSSHSign returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for signing SSH Certificates.
func (b *base) AuthorizeSSHSign(ctx context.Context, token string) ([]SignOption, error) {
	return nil, errs.Unauthorized("provisioner.AuthorizeSSHSign not implemented")
}

// AuthorizeRevoke returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for revoking SSH Certificates.
func (b *base) AuthorizeSSHRevoke(ctx context.Context, token string) error {
	return errs.Unauthorized("provisioner.AuthorizeSSHRevoke not implemented")
}

// AuthorizeSSHRenew returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for renewing SSH Certificates.
func (b *base) AuthorizeSSHRenew(ctx context.Context, token string) (*ssh.Certificate, error) {
	return nil, errs.Unauthorized("provisioner.AuthorizeSSHRenew not implemented")
}

// AuthorizeSSHRekey returns an unimplemented error. Provisioners should overwrite
// this method if they will support authorizing tokens for rekeying SSH Certificates.
func (b *base) AuthorizeSSHRekey(ctx context.Context, token string) (*ssh.Certificate, []SignOption, error) {
	return nil, nil, errs.Unauthorized("provisioner.AuthorizeSSHRekey not implemented")
}

// Identity is the type representing an externally supplied identity that is used
// by provisioners to populate certificate fields.
type Identity struct {
	Usernames   []string `json:"usernames"`
	Permissions `json:"permissions"`
}

// Permissions defines extra extensions and critical options to grant to an SSH certificate.
type Permissions struct {
	Extensions      map[string]string `json:"extensions"`
	CriticalOptions map[string]string `json:"criticalOptions"`
}

// GetIdentityFunc is a function that returns an identity.
type GetIdentityFunc func(ctx context.Context, p Interface, email string) (*Identity, error)

// DefaultIdentityFunc return a default identity depending on the provisioner
// type. For OIDC email is always present and the usernames might
// contain empty strings.
func DefaultIdentityFunc(ctx context.Context, p Interface, email string) (*Identity, error) {
	switch k := p.(type) {
	case *OIDC:
		// OIDC principals would be:
		// ~~1. Preferred usernames.~~ Note: Under discussion, currently disabled
		// 2. Sanitized local.
		// 3. Raw local (if different).
		// 4. Email address.
		name := SanitizeSSHUserPrincipal(email)
		if !sshUserRegex.MatchString(name) {
			return nil, errors.Errorf("invalid principal '%s' from email '%s'", name, email)
		}
		usernames := []string{name}
		if i := strings.LastIndex(email, "@"); i >= 0 {
			usernames = append(usernames, email[:i])
		}
		usernames = append(usernames, email)
		return &Identity{
			Usernames: SanitizeStringSlices(usernames),
		}, nil
	default:
		return nil, errors.Errorf("provisioner type '%T' not supported by identity function", k)
	}
}

// SanitizeStringSlices removes duplicated an empty strings.
func SanitizeStringSlices(original []string) []string {
	output := []string{}
	seen := make(map[string]struct{})
	for _, entry := range original {
		if entry == "" {
			continue
		}
		if _, value := seen[entry]; !value {
			seen[entry] = struct{}{}
			output = append(output, entry)
		}
	}
	return output
}

// MockProvisioner for testing
type MockProvisioner struct {
	Mret1, Mret2, Mret3 interface{}
	Merr                error
	MgetID              func() string
	MgetTokenID         func(string) (string, error)
	MgetName            func() string
	MgetType            func() Type
	MgetEncryptedKey    func() (string, string, bool)
	Minit               func(Config) error
	MauthorizeSign      func(ctx context.Context, ott string) ([]SignOption, error)
	MauthorizeRenew     func(ctx context.Context, cert *x509.Certificate) error
	MauthorizeRevoke    func(ctx context.Context, ott string) error
	MauthorizeSSHSign   func(ctx context.Context, ott string) ([]SignOption, error)
	MauthorizeSSHRenew  func(ctx context.Context, ott string) (*ssh.Certificate, error)
	MauthorizeSSHRekey  func(ctx context.Context, ott string) (*ssh.Certificate, []SignOption, error)
	MauthorizeSSHRevoke func(ctx context.Context, ott string) error
}

// GetID mock
func (m *MockProvisioner) GetID() string {
	if m.MgetID != nil {
		return m.MgetID()
	}
	return m.Mret1.(string)
}

// GetTokenID mock
func (m *MockProvisioner) GetTokenID(token string) (string, error) {
	if m.MgetTokenID != nil {
		return m.MgetTokenID(token)
	}
	if m.Mret1 == nil {
		return "", m.Merr
	}
	return m.Mret1.(string), m.Merr
}

// GetName mock
func (m *MockProvisioner) GetName() string {
	if m.MgetName != nil {
		return m.MgetName()
	}
	return m.Mret1.(string)
}

// GetType mock
func (m *MockProvisioner) GetType() Type {
	if m.MgetType != nil {
		return m.MgetType()
	}
	return m.Mret1.(Type)
}

// GetEncryptedKey mock
func (m *MockProvisioner) GetEncryptedKey() (string, string, bool) {
	if m.MgetEncryptedKey != nil {
		return m.MgetEncryptedKey()
	}
	return m.Mret1.(string), m.Mret2.(string), m.Mret3.(bool)
}

// Init mock
func (m *MockProvisioner) Init(c Config) error {
	if m.Minit != nil {
		return m.Minit(c)
	}
	return m.Merr
}

// AuthorizeSign mock
func (m *MockProvisioner) AuthorizeSign(ctx context.Context, ott string) ([]SignOption, error) {
	if m.MauthorizeSign != nil {
		return m.MauthorizeSign(ctx, ott)
	}
	return m.Mret1.([]SignOption), m.Merr
}

// AuthorizeRevoke mock
func (m *MockProvisioner) AuthorizeRevoke(ctx context.Context, ott string) error {
	if m.MauthorizeRevoke != nil {
		return m.MauthorizeRevoke(ctx, ott)
	}
	return m.Merr
}

// AuthorizeRenew mock
func (m *MockProvisioner) AuthorizeRenew(ctx context.Context, c *x509.Certificate) error {
	if m.MauthorizeRenew != nil {
		return m.MauthorizeRenew(ctx, c)
	}
	return m.Merr
}

// AuthorizeSSHSign mock
func (m *MockProvisioner) AuthorizeSSHSign(ctx context.Context, ott string) ([]SignOption, error) {
	if m.MauthorizeSign != nil {
		return m.MauthorizeSign(ctx, ott)
	}
	return m.Mret1.([]SignOption), m.Merr
}

// AuthorizeSSHRenew mock
func (m *MockProvisioner) AuthorizeSSHRenew(ctx context.Context, ott string) (*ssh.Certificate, error) {
	if m.MauthorizeRenew != nil {
		return m.MauthorizeSSHRenew(ctx, ott)
	}
	return m.Mret1.(*ssh.Certificate), m.Merr
}

// AuthorizeSSHRekey mock
func (m *MockProvisioner) AuthorizeSSHRekey(ctx context.Context, ott string) (*ssh.Certificate, []SignOption, error) {
	if m.MauthorizeSSHRekey != nil {
		return m.MauthorizeSSHRekey(ctx, ott)
	}
	return m.Mret1.(*ssh.Certificate), m.Mret2.([]SignOption), m.Merr
}

// AuthorizeSSHRevoke mock
func (m *MockProvisioner) AuthorizeSSHRevoke(ctx context.Context, ott string) error {
	if m.MauthorizeSSHRevoke != nil {
		return m.MauthorizeSSHRevoke(ctx, ott)
	}
	return m.Merr
}