rest-server/handlers.go

package restserver

import (
	"errors"
	"log"
	"net/http"
	"path"
	"path/filepath"
	"strings"

	"github.com/restic/rest-server/quota"
	"github.com/restic/rest-server/repo"
)

// Server encapsulates the rest-server's settings and repo management logic
type Server struct {
	Path         string
	Listen       string
	Log          string
	CPUProfile   string
	TLSKey       string
	TLSCert      string
	TLS          bool
	NoAuth       bool
	AppendOnly   bool
	PrivateRepos bool
	Prometheus   bool
	Debug        bool
	MaxRepoSize  int64

	htpasswdFile *HtpasswdFile
	quotaManager *quota.Manager
}

// MaxFolderDepth is the maxDepth param passed to splitURLPath.
// A max depth of 2 mean that we accept folders like: '/', '/foo' and '/foo/bar'
// TODO: Move to a Server option
const MaxFolderDepth = 2

// httpDefaultError write a HTTP error with the default description
func httpDefaultError(w http.ResponseWriter, code int) {
	http.Error(w, http.StatusText(code), code)
}

// ServeHTTP makes this server an http.Handler. It handlers the administrative
// part of the request (figuring out the filesystem location, performing
// authentication, etc) and then passes it on to repo.Handler for actual
// REST API processing.
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// First of all, check auth (will always pass if NoAuth is set)
	username, ok := s.checkAuth(r)
	if !ok {
		httpDefaultError(w, http.StatusUnauthorized)
		return
	}

	// Perform the path parsing to determine the repo folder and remainder for the
	// repo handler.
	folderPath, remainder := splitURLPath(r.URL.Path, MaxFolderDepth)
	if !folderPathValid(folderPath) {
		log.Printf("Invalid request path: %s", r.URL.Path)
		httpDefaultError(w, http.StatusNotFound)
		return
	}

	// Check if the current user is allowed to access this path
	if !s.NoAuth && s.PrivateRepos {
		if len(folderPath) == 0 || folderPath[0] != username {
			httpDefaultError(w, http.StatusUnauthorized)
			return
		}
	}

	// Determine filesystem path for this repo
	fsPath, err := join(s.Path, folderPath...)
	if err != nil {
		// We did not expect an error at this stage, because we just checked the path
		log.Printf("Unexpected join error for path %q", r.URL.Path)
		httpDefaultError(w, http.StatusNotFound)
		return
	}

	// Pass the request to the repo.Handler
	opt := repo.Options{
		AppendOnly:   s.AppendOnly,
		Debug:        s.Debug,
		QuotaManager: s.quotaManager, // may be nil
	}
	if s.Prometheus {
		opt.BlobMetricFunc = makeBlobMetricFunc(username, folderPath)
	}
	repoHandler, err := repo.New(fsPath, opt)
	if err != nil {
		log.Printf("repo.New error: %v", err)
		httpDefaultError(w, http.StatusInternalServerError)
		return
	}
	r.URL.Path = remainder // strip folderPath for next handler
	repoHandler.ServeHTTP(w, r)
}

func valid(name string) bool {
	// taken from net/http.Dir
	if strings.Contains(name, "\x00") {
		return false
	}

	if filepath.Separator != '/' && strings.ContainsRune(name, filepath.Separator) {
		return false
	}

	return true
}

func isValidType(name string) bool {
	for _, tpe := range repo.ObjectTypes {
		if name == tpe {
			return true
		}
	}
	for _, tpe := range repo.FileTypes {
		if name == tpe {
			return true
		}
	}
	return false
}

// join takes a number of path names, sanitizes them, and returns them joined
// with base for the current operating system to use (dirs separated by
// filepath.Separator). The returned path is always either equal to base or a
// subdir of base.
func join(base string, names ...string) (string, error) {
	clean := make([]string, 0, len(names)+1)
	clean = append(clean, base)

	// taken from net/http.Dir
	for _, name := range names {
		if !valid(name) {
			return "", errors.New("invalid character in path")
		}

		clean = append(clean, filepath.FromSlash(path.Clean("/"+name)))
	}

	return filepath.Join(clean...), nil
}

// splitURLPath splits the URL path into a folderPath of the subrepo, and
// a remainder that can be passed to repo.Handler.
// Example: /foo/bar/locks/0123... will be split into:
//          ["foo", "bar"] and "/locks/0123..."
func splitURLPath(urlPath string, maxDepth int) (folderPath []string, remainder string) {
	if !strings.HasPrefix(urlPath, "/") {
		// Really should start with "/"
		return nil, urlPath
	}
	p := strings.SplitN(urlPath, "/", maxDepth+2)
	// Skip the empty first one and the remainder in the last one
	for _, name := range p[1 : len(p)-1] {
		if isValidType(name) {
			// We found a part that is a special repo file or dir
			break
		}
		folderPath = append(folderPath, name)
	}
	// If the folder path is empty, the whole path is the remainder (do not strip '/')
	if len(folderPath) == 0 {
		return nil, urlPath
	}
	// Check that the urlPath starts with the reconstructed path, which should
	// always be the case.
	fullFolderPath := "/" + strings.Join(folderPath, "/")
	if !strings.HasPrefix(urlPath, fullFolderPath) {
		return nil, urlPath
	}
	return folderPath, urlPath[len(fullFolderPath):]
}

// folderPathValid checks if a folderPath returned by splitURLPath is valid and
// safe.
func folderPathValid(folderPath []string) bool {
	for _, name := range folderPath {
		if name == "" || name == ".." || name == "." || !valid(name) {
			return false
		}
	}
	return true
}