emissary/internal/auth/agent/authenticator.go

package agent

import (
	"context"
	"net/http"
	"strings"
	"time"

	"forge.cadoles.com/Cadoles/emissary/internal/auth"
	"forge.cadoles.com/Cadoles/emissary/internal/datastore"
	"github.com/lestrrat-go/jwx/v2/jws"
	"github.com/lestrrat-go/jwx/v2/jwt"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

const DefaultAcceptableSkew = 5 * time.Minute

type Authenticator struct {
	repo           datastore.AgentRepository
	acceptableSkew time.Duration
}

// Authenticate implements auth.Authenticator.
func (a *Authenticator) Authenticate(ctx context.Context, r *http.Request) (auth.User, error) {
	ctx = logger.With(r.Context(), logger.F("remoteAddr", r.RemoteAddr))

	authorization := r.Header.Get("Authorization")
	if authorization == "" {
		return nil, errors.WithStack(auth.ErrUnauthenticated)
	}

	rawToken := strings.TrimPrefix(authorization, "Bearer ")
	if rawToken == "" {
		return nil, errors.WithStack(auth.ErrUnauthenticated)
	}

	token, err := jwt.Parse([]byte(rawToken), jwt.WithVerify(false))
	if err != nil {
		return nil, errors.WithStack(err)
	}

	rawThumbprint, exists := token.Get(keyThumbprint)
	if !exists {
		return nil, errors.Errorf("could not find '%s' claim", keyThumbprint)
	}

	thumbrint, ok := rawThumbprint.(string)
	if !ok {
		return nil, errors.Errorf("unexpected '%s' claim value: '%v'", keyThumbprint, rawThumbprint)
	}

	agents, _, err := a.repo.Query(
		ctx,
		datastore.WithAgentQueryThumbprints(thumbrint),
		datastore.WithAgentQueryLimit(1),
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	if len(agents) != 1 {
		return nil, errors.Errorf("unexpected number of found agents: '%d'", len(agents))
	}

	agent, err := a.repo.Get(
		ctx,
		agents[0].ID,
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	_, err = jwt.Parse(
		[]byte(rawToken),
		jwt.WithKeySet(agent.KeySet.Set, jws.WithRequireKid(false)),
		jwt.WithValidate(true),
		jwt.WithAcceptableSkew(a.acceptableSkew),
	)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	contactedAt := time.Now()

	agent, err = a.repo.Update(ctx, agent.ID, datastore.WithAgentUpdateContactedAt(contactedAt))
	if err != nil {
		return nil, errors.WithStack(err)
	}

	user := &User{
		agent: agent,
	}

	return user, nil
}

func NewAuthenticator(repo datastore.AgentRepository, acceptableSkew time.Duration) *Authenticator {
	return &Authenticator{
		repo:           repo,
		acceptableSkew: acceptableSkew,
	}
}

var _ auth.Authenticator = &Authenticator{}