Add support for file uploads

assets/templates/html/newFileUploadPasteSuccess.html.tmpl

@@ -0,0 +1,3 @@
+{{define "title"}}
+Success - rushlink
+{{end}}

assets/templates/txt/newFileUploadPasteSuccess.txt.tmpl

@@ -0,0 +1,4 @@
+https://{{.Request.Host}}/{{.Paste.Key}}
+{{if .Request.PostForm.deleteToken -}}
+https://{{.Request.Host}}/{{.Paste.Key}}?deleteToken={{.Paste.DeleteToken | urlquery}}
+{{end -}}

cmd/rushlink/main.go

@@ -9,6 +9,7 @@ import (
 
 var (
 	databasePath  = flag.String("database", "", "location of the database file")
+	fileStorePath = flag.String("file-store", "", "path to the directory where uploaded files will be stored")
 	httpListen    = flag.String("listen", "127.0.0.1:8000", "listen address (host:port)")
 	metricsListen = flag.String("metrics_listen", "127.0.0.1:58614", "listen address for metrics (host:port)")
 )
@@ -16,10 +17,13 @@ var (
 func main() {
 	flag.Parse()
 
-	if err := rushlink.Open(*databasePath); err != nil {
+	if err := rushlink.OpenDB(*databasePath); err != nil {
+		log.Fatalln(err)
+	}
+	defer rushlink.CloseDB()
+	if err := rushlink.OpenFileStore(*fileStorePath); err != nil {
 		log.Fatalln(err)
 	}
-	defer rushlink.Close()
 
 	go rushlink.StartMetricsServer(*metricsListen)
 	rushlink.StartMainServer(*httpListen)

db.go

@@ -15,7 +15,7 @@ var DB *bolt.DB
 //
 // If we alter the database format, we bump this number and write a new
 // database migration in migrateDatabase().
-const CURRENT_MIGRATE_VERSION = 1
+const CURRENT_MIGRATE_VERSION = 2
 
 // Bucket storing everything that is not a bulk value. This includes stuff like
 // the database version, secret site-wide keys.
@@ -24,12 +24,15 @@ const BUCKET_CONF = "conf"
 // The main bucket for paste values and URL redirects
 const BUCKET_PASTES = "pastes"
 
+// The main bucket for file uploads
+const BUCKET_FILE_UPLOAD = "fileUpload"
+
 // This value stores the current migration version. If this value is less than
 // CURRENT_MIGRATE_VERSION, the database has to be migrated.
 const KEY_MIGRATE_VERSION = "migrate_version"
 
 // Open the bolt database
-func Open(path string) error {
+func OpenDB(path string) error {
 	if path == "" {
 		return errors.New("database not set")
 	}
@@ -43,7 +46,7 @@ func Open(path string) error {
 }
 
 // Close the bolt database
-func Close() error {
+func CloseDB() error {
 	if DB == nil {
 		panic("no open database")
 	}
@@ -60,25 +63,35 @@ func migrateDatabase(tx *bolt.Tx) error {
 	// Migrate the database to version 1
 	if dbVersion < 1 {
 		log.Println("migrating database to version 1")
-
 		// Create conf bucket
 		_, err := tx.CreateBucket([]byte(BUCKET_CONF))
 		if err != nil {
 			return err
 		}
-
 		// Create paste bucket
 		_, err = tx.CreateBucket([]byte(BUCKET_PASTES))
 		if err != nil {
 			return err
 		}
-
 		// Update the version number
 		if err := setDBVersion(tx, 1); err != nil {
 			return err
 		}
 	}
 
+	if dbVersion < 2 {
+		log.Println("migrating database to version 2")
+		// Create fileUpload bucket
+		_, err := tx.CreateBucket([]byte(BUCKET_FILE_UPLOAD))
+		if err != nil {
+			return err
+		}
+		// Update the version number
+		if err := setDBVersion(tx, 2); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 

fileupload.go

@@ -0,0 +1,182 @@
+package rushlink
+
+import (
+	"encoding/hex"
+	"hash/crc32"
+	"io"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+
+	"github.com/google/uuid"
+	"github.com/pkg/errors"
+	bolt "go.etcd.io/bbolt"
+)
+
+// Use the Castagnoli checksum because of the acceleration on Intel CPUs
+var checksumTable = crc32.MakeTable(crc32.Castagnoli)
+
+// Where to store the uploaded files
+var fileStoreDir = ""
+
+// Custom HTTP filesystem handler
+type fileUploadFileSystem struct {
+	fs http.FileSystem
+}
+
+// Open opens file
+func (fs fileUploadFileSystem) Open(path string) (http.File, error) {
+	log.Println(path)
+	file, err := fs.fs.Open(path)
+	if err != nil {
+		return nil, errors.Wrap(err, "opening file")
+	}
+	stat, err := file.Stat()
+	if err != nil {
+		return nil, errors.Wrap(err, "file.Stat()")
+	}
+	if stat.IsDir() {
+		return nil, errors.New("directory index not allowed")
+	}
+	return file, nil
+}
+
+type fileUploadState int
+
+type fileUpload struct {
+	State       fileUploadState
+	ID          uuid.UUID
+	FileName    string
+	ContentType string
+	Checksum    uint32
+}
+
+const (
+	dirMode  os.FileMode = 0750
+	fileMode os.FileMode = 0640
+)
+
+const (
+	fileUploadStateUndef   fileUploadState = 0
+	fileUploadStatePresent                 = 1
+	fileUploadStateDeleted                 = 2
+)
+
+func (t fileUploadState) String() string {
+	switch t {
+	case fileUploadStateUndef:
+		return "unknown"
+	case fileUploadStatePresent:
+		return "present"
+	case fileUploadStateDeleted:
+		return "deleted"
+	default:
+		return "invalid"
+	}
+}
+
+func OpenFileStore(path string) error {
+	if path == "" {
+		return errors.New("file store path not set")
+	}
+
+	// Try to create the file store directory if it does not yet exist
+	if err := os.MkdirAll(path, dirMode); err != nil {
+		return errors.Wrap(err, "creating file store directory")
+	}
+
+	fileStoreDir = path[:]
+	return nil
+}
+
+func newFileUpload(tx *bolt.Tx, r io.Reader, fileName string, contentType string) (*fileUpload, error) {
+	id, err := uuid.NewRandom()
+	if err != nil {
+		return nil, errors.Wrap(err, "generating UUID")
+	}
+
+	filePath := fileStorePath(id, fileName)
+	if err := os.Mkdir(path.Dir(filePath), dirMode); err != nil {
+		return nil, errors.Wrap(err, "creating file dir")
+	}
+	file, err := os.OpenFile(filePath, os.O_WRONLY|os.O_CREATE, fileMode)
+	if err != nil {
+		return nil, errors.Wrap(err, "opening file")
+	}
+	defer file.Close()
+
+	hash := crc32.New(checksumTable)
+	tee := io.TeeReader(r, hash)
+	_, err = io.Copy(file, tee)
+	if err != nil {
+		return nil, errors.Wrap(err, "writing to file")
+	}
+
+	fu := &fileUpload{
+		State:       fileUploadStatePresent,
+		ID:          id,
+		FileName:    fileName,
+		ContentType: contentType,
+		Checksum:    hash.Sum32(),
+	}
+	if err := fu.save(tx); err != nil {
+		return nil, err
+	}
+	return fu, nil
+}
+
+func getFileUpload(tx *bolt.Tx, id uuid.UUID) (*fileUpload, error) {
+	bucket := tx.Bucket([]byte(BUCKET_FILE_UPLOAD))
+	if bucket == nil {
+		return nil, errors.Errorf("bucket %v does not exist", BUCKET_FILE_UPLOAD)
+	}
+	storedBytes := bucket.Get(id[:])
+	if storedBytes == nil {
+		return nil, nil
+	}
+	fu := &fileUpload{}
+	err := Unmarshal(storedBytes, fu)
+	return fu, err
+}
+
+func (fu *fileUpload) save(tx *bolt.Tx) error {
+	bucket := tx.Bucket([]byte(BUCKET_FILE_UPLOAD))
+	if bucket == nil {
+		return errors.Errorf("bucket %v does not exist", BUCKET_FILE_UPLOAD)
+	}
+
+	buf, err := Marshal(fu)
+	if err != nil {
+		return errors.Wrap(err, "encoding for database failed")
+	}
+	if err := bucket.Put(fu.ID[:], buf); err != nil {
+		return errors.Wrap(err, "database transaction failed")
+	}
+	return nil
+}
+
+func (fu *fileUpload) delete(tx *bolt.Tx) error {
+	// Replace the old paste with a new empty paste
+	return (&fileUpload{
+		ID:    fu.ID,
+		State: fileUploadStateDeleted,
+	}).save(tx)
+}
+
+func (fu *fileUpload) url() *url.URL {
+	rawurl := "/uploads/" + hex.EncodeToString(fu.ID[:]) + "/" + fu.FileName
+	urlParse, err := url.Parse(rawurl)
+	if err != nil {
+		panic("could not construct /uploads/ url")
+	}
+	return urlParse
+}
+
+func fileStorePath(id uuid.UUID, fileName string) string {
+	if fileStoreDir == "" {
+		panic("fileStoreDir called while the file store path has not been set")
+	}
+	return path.Join(fileStoreDir, hex.EncodeToString(id[:]), fileName)
+}

go.mod

@@ -3,6 +3,7 @@ module gitea.hashru.nl/dsprenkels/rushlink
 go 1.12
 
 require (
+	github.com/google/uuid v1.1.1
 	github.com/gorilla/mux v1.7.3
 	github.com/pkg/errors v0.8.1
 	github.com/prometheus/client_golang v1.1.0

go.sum

@@ -17,6 +17,8 @@ github.com/golang/protobuf v1.3.2 h1:6nsPYzhq5kReh6QImI3k5qWzO4PEbvbIW2cwSfR/6xs
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
+github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
+github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/gorilla/mux v1.7.3 h1:gnP5JzjVOuiZD07fKKToCAOjS0yOpj/qPETTXCCS6hw=
 github.com/gorilla/mux v1.7.3/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=

handlers.go

@@ -4,11 +4,15 @@ import (
 	"crypto/subtle"
 	"encoding/base64"
 	"fmt"
+	"io"
 	"log"
+	"mime/multipart"
 	"net/http"
 	"net/url"
+	"os"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/gorilla/mux"
 	"github.com/pkg/errors"
 	bolt "go.etcd.io/bbolt"
@@ -31,36 +35,48 @@ var ReservedPasteKeys = []string{"xd42", "example"}
 var base64Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
 var base64Encoder = base64.RawURLEncoding.WithPadding(base64.NoPadding)
 
-func (t pasteType) String() string {
-	switch t {
-	case typeUndef:
-		return "unknown"
-	case typePaste:
-		return "paste"
-	case typeRedirect:
-		return "redirect"
-	default:
-		return "invalid"
-	}
-}
-
-func (t pasteState) String() string {
-	switch t {
-	case stateUndef:
-		return "unknown"
-	case statePresent:
-		return "present"
-	case stateDeleted:
-		return "deleted"
-	default:
-		return "invalid"
-	}
-}
-
 func indexGetHandler(w http.ResponseWriter, r *http.Request) {
 	render(w, r, "index", map[string]interface{}{})
 }
 
+func uploadFileGetHandler(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	id := vars["id"]
+
+	var fu *fileUpload
+	var badID bool
+	if err := DB.View(func(tx *bolt.Tx) error {
+		fuID, err := uuid.Parse(id)
+		if err != nil {
+			badID = true
+			return err
+		}
+		fu, err = getFileUpload(tx, fuID)
+		return err
+	}); err != nil {
+		if badID {
+			renderError(w, r, http.StatusNotFound, "malformed file id")
+			return
+		} else {
+			panic(err)
+		}
+	}
+
+	filePath := fileStorePath(fu.ID, fu.FileName)
+	file, err := os.Open(filePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			log.Printf("error: %v should exist according to the database, but it doesn't", filePath)
+			renderError(w, r, http.StatusNotFound, "file not found")
+			return
+		} else {
+			panic(err)
+		}
+	}
+	w.Header().Set("Content-Type", fu.ContentType)
+	io.Copy(w, file)
+}
+
 func viewPasteHandler(w http.ResponseWriter, r *http.Request) {
 	viewPasteHandlerInner(w, r, 0)
 }
@@ -77,14 +93,28 @@ func viewPasteHandlerInner(w http.ResponseWriter, r *http.Request, flags viewPas
 	vars := mux.Vars(r)
 	key := vars["key"]
 	var p *paste
+	var fuID *uuid.UUID
+	var fu *fileUpload
 	if err := DB.View(func(tx *bolt.Tx) error {
 		var err error
 		p, err = getPaste(tx, key)
+		if err != nil {
 			return err
+		}
+		if p != nil && p.Type == pasteTypeFileUpload {
+			var id uuid.UUID
+			copy(id[:], p.Content)
+			fuID = &id
+			fu, err = getFileUpload(tx, id)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
 	}); err != nil {
 		panic(err)
-		return
 	}
+
 	if p == nil {
 		renderError(w, r, http.StatusNotFound, "url key not found in the database")
 		return
@@ -116,47 +146,101 @@ func viewPasteHandlerInner(w http.ResponseWriter, r *http.Request, flags viewPas
 	}
 
 	switch p.State {
-	case statePresent:
+	case pasteStatePresent:
+		var location string
+		switch p.Type {
+		case pasteTypeFileUpload:
+			if fu == nil {
+				panic(fmt.Sprintf("file for id %v does not exist in database\n", fuID))
+			}
+			location = fu.url().String()
+			break
+		case pasteTypeRedirect:
+			location = p.redirectURL().String()
+			break
+		default:
+			panic("paste type unsupported")
+		}
 		if flags&viewNoRedirect == 0 {
-			rawurl := string(p.Content)
+			http.Redirect(w, r, location, http.StatusSeeOther)
-			urlParse, err := url.Parse(rawurl)
-			if err != nil {
-				panic(errors.Wrapf(err, "invalid URL ('%v') in database for key '%v'", rawurl, p.Key))
 		}
-			http.Redirect(w, r, urlParse.String(), http.StatusSeeOther)
+		fmt.Fprint(w, location)
-		}
+	case pasteStateDeleted:
-		w.Write(p.Content)
+		renderError(w, r, http.StatusGone, "paste has been deleted\n")
-	case stateDeleted:
-		renderError(w, r, http.StatusGone, "paste has been deleted")
 	default:
 		panic(errors.Errorf("invalid paste.State (%v) for key '%v'", p.State, p.Key))
 	}
 }
 
 func newPasteHandler(w http.ResponseWriter, r *http.Request) {
-	if err := r.ParseMultipartForm(50 * 1000 * 1000); err != nil {
+	newPasteHandlerMultipart(w, r, func(w http.ResponseWriter, r *http.Request) {
-		panic(err)
+		newPasteHandlerURLEncoded(w, r, func(w http.ResponseWriter, r *http.Request) {
-	}
+			renderError(w, r, http.StatusBadRequest, "no form data in request\n")
+		})
+	})
+}
 
-	// Determine what kind of post this is, currently only `shorten=...`
+// Try to parse the new-paste request as multi-part form.
-	if len(r.PostForm) == 0 {
+//
-		renderError(w, r, http.StatusBadRequest, "empty body in POST request\n")
+// If there is no multi-part form in the request, this handler will call next.
+func newPasteHandlerMultipart(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	reader, err := r.MultipartReader()
+	if err != nil {
+		next(w, r)
 		return
 	}
-	shorten_values, prs := r.PostForm["shorten"]
+
-	if !prs {
+	part, err := reader.NextPart()
+	if err != nil {
+		if err == io.EOF {
+			renderError(w, r, http.StatusBadRequest, "multipart form is empty\n")
+			return
+		}
+		panic(errors.Wrap(err, "multipart.Reader.NextPart"))
+	}
+	if part.FormName() != "file" {
+		msg := fmt.Sprintf("invalid multipart form name: %v", part.FormName())
+		renderError(w, r, http.StatusBadRequest, msg)
+		return
+	}
+
+	newFileUploadPasteHandler(w, r, *part)
+}
+
+func newFileUploadPasteHandler(w http.ResponseWriter, r *http.Request, part multipart.Part) {
+	var fu *fileUpload
+	var paste *paste
+	if err := DB.Update(func(tx *bolt.Tx) error {
+		var err error
+		// Create the fileUpload in the database
+		fu, err = newFileUpload(tx, &part, part.FileName(), part.Header.Get("Content-Type"))
+		if err != nil {
+			panic(errors.Wrap(err, "creating fileUpload"))
+		}
+
+		paste, err = shortenFileUploadID(tx, fu.ID)
+		return err
+	}); err != nil {
+		panic(err)
+	}
+	data := map[string]interface{}{"Paste": paste}
+	render(w, r, "newFileUploadPasteSuccess", data)
+}
+
+func newPasteHandlerURLEncoded(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	if err := r.ParseForm(); err != nil {
+		next(w, r)
+		return
+	}
+	shorten := r.PostFormValue("shorten")
+	if shorten == "" {
 		renderError(w, r, http.StatusBadRequest, "no 'shorten' param given\n")
 		return
 	}
-	if len(shorten_values) != 1 {
+	newRedirectPasteHandler(w, r, shorten)
-		renderError(w, r, http.StatusBadRequest, "only one 'shorten' param is allowed per request\n")
-		return
-	}
-
-	newRedirectPasteHandler(w, r)
 }
 
-func newRedirectPasteHandler(w http.ResponseWriter, r *http.Request) {
+func newRedirectPasteHandler(w http.ResponseWriter, r *http.Request, shorten string) {
 	rawurl := r.PostForm.Get("shorten")
 	userURL, err := url.ParseRequestURI(rawurl)
 	if err != nil {
@@ -165,11 +249,11 @@ func newRedirectPasteHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if userURL.Scheme == "" {
-		renderError(w, r, http.StatusBadRequest, "invalid url (unspecified scheme)")
+		renderError(w, r, http.StatusBadRequest, "invalid url (unspecified scheme)\n")
 		return
 	}
 	if userURL.Host == "" {
-		renderError(w, r, http.StatusBadRequest, "invalid url (unspecified host)")
+		renderError(w, r, http.StatusBadRequest, "invalid url (unspecified host)\n")
 		return
 	}
 
@@ -193,7 +277,7 @@ func deletePasteHandler(w http.ResponseWriter, r *http.Request) {
 
 	deleteToken := getDeleteTokenFromRequest(r)
 	if deleteToken == "" {
-		renderError(w, r, http.StatusBadRequest, "no delete token provided")
+		renderError(w, r, http.StatusBadRequest, "no delete token provided\n")
 		return
 	}
 
@@ -211,15 +295,29 @@ func deletePasteHandler(w http.ResponseWriter, r *http.Request) {
 		return errors.New("invalid delete token")
 	}); err != nil {
 		log.Printf("error: %v\n", err)
-		renderError(w, r, errorCode, fmt.Sprintf("error: %v", err))
+		renderError(w, r, errorCode, fmt.Sprintf("error: %v\n", err))
 		return
 	}
 }
 
+// Add a new fileUpload redirect to the database
+//
+// Returns the new paste key if the fileUpload was successfully added to the
+// database
+func shortenFileUploadID(tx *bolt.Tx, id uuid.UUID) (*paste, error) {
+	return shorten(tx, pasteTypeFileUpload, id[:])
+}
+
 // Add a new URL to the database
 //
-// Returns the new ID if the url was successfully shortened
+// Returns the new paste key if the url was successfully shortened
 func shortenURL(tx *bolt.Tx, userURL *url.URL) (*paste, error) {
+	return shorten(tx, pasteTypeRedirect, []byte(userURL.String()))
+}
+
+// Add a paste (of any kind) to the database with arbitrary content.
+func shorten(tx *bolt.Tx, ty pasteType, content []byte) (*paste, error) {
+	// Generate the paste key
 	pasteKey, err := generatePasteKey(tx)
 	if err != nil {
 		return nil, errors.Wrap(err, "generating paste key")
@@ -233,9 +331,9 @@ func shortenURL(tx *bolt.Tx, userURL *url.URL) (*paste, error) {
 
 	// Store the new key
 	p := paste{
-		Type:        typeRedirect,
+		Type:        ty,
-		State:       statePresent,
+		State:       pasteStatePresent,
-		Content:     []byte(userURL.String()),
+		Content:     content,
 		Key:         pasteKey,
 		DeleteToken: deleteToken,
 		TimeCreated: time.Now().UTC(),

paste.go

@@ -3,6 +3,7 @@ package rushlink
 import (
 	"crypto/rand"
 	"encoding/hex"
+	"net/url"
 	"strings"
 	"time"
 
@@ -23,17 +24,44 @@ type paste struct {
 }
 
 const (
-	typeUndef    pasteType = 0
+	pasteTypeUndef      pasteType = 0
-	typePaste              = 1
+	pasteTypePaste                = 1
-	typeRedirect           = 2
+	pasteTypeRedirect             = 2
+	pasteTypeFileUpload           = 3
 )
 
 const (
-	stateUndef   pasteState = 0
+	pasteStateUndef   pasteState = 0
-	statePresent            = 1
+	pasteStatePresent            = 1
-	stateDeleted            = 2
+	pasteStateDeleted            = 2
 )
 
+func (t pasteType) String() string {
+	switch t {
+	case pasteTypeUndef:
+		return "unknown"
+	case pasteTypePaste:
+		return "paste"
+	case pasteTypeRedirect:
+		return "redirect"
+	default:
+		return "invalid"
+	}
+}
+
+func (t pasteState) String() string {
+	switch t {
+	case pasteStateUndef:
+		return "unknown"
+	case pasteStatePresent:
+		return "present"
+	case pasteStateDeleted:
+		return "deleted"
+	default:
+		return "invalid"
+	}
+}
+
 // Retrieve a paste from the database
 func getPaste(tx *bolt.Tx, key string) (*paste, error) {
 	pastesBucket := tx.Bucket([]byte(BUCKET_PASTES))
@@ -65,15 +93,31 @@ func (p *paste) save(tx *bolt.Tx) error {
 	return nil
 }
 
-func (p paste) delete(tx *bolt.Tx) error {
+func (p *paste) delete(tx *bolt.Tx) error {
 	// Replace the old paste with a new empty paste
 	return (&paste{
 		Key:         p.Key,
-		State:       stateDeleted,
+		State:       pasteStateDeleted,
 		DeleteToken: p.DeleteToken,
 	}).save(tx)
 }
 
+// Get the URL from this paste.
+//
+// This function assumes that the paste is valid.  If the paste struct is
+// corrupted in some way, this function will panic.
+func (p *paste) redirectURL() *url.URL {
+	if p.Type != pasteTypeRedirect {
+		panic("expected p.Type to be pasteTypeRedirect")
+	}
+	rawurl := string(p.Content)
+	urlParse, err := url.Parse(rawurl)
+	if err != nil {
+		panic(errors.Wrapf(err, "invalid URL ('%v') in database for key '%v'", rawurl, p.Key))
+	}
+	return urlParse
+}
+
 // Generate a key until it is not in the database, this occurs in O(log N),
 // where N is the amount of keys stored in the url-shorten database.
 func generatePasteKey(tx *bolt.Tx) (string, error) {

router.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"runtime/debug"
 	"time"
 
 	"github.com/gorilla/mux"
@@ -15,12 +16,14 @@ func recoveryMiddleware(next http.Handler) http.Handler {
 			defer func() {
 				if err := recover(); err != nil {
 					log.Printf("error: panic while recovering from another panic: %v\n", err)
+					debug.PrintStack()
 					fmt.Fprintf(w, "internal server error: %v\n", err)
 				}
 			}()
 
 			if err := recover(); err != nil {
 				log.Printf("error: %v\n", err)
+				debug.PrintStack()
 				renderInternalServerError(w, r, err)
 			}
 		}()
@@ -39,6 +42,7 @@ func StartMainServer(addr string) {
 	router.HandleFunc("/{key:[A-Za-z0-9-_]{4,}}/meta", viewPasteHandlerMeta).Methods("GET")
 	router.HandleFunc("/{key:[A-Za-z0-9-_]{4,}}", deletePasteHandler).Methods("DELETE")
 	router.HandleFunc("/{key:[A-Za-z0-9-_]{4,}}/delete", deletePasteHandler).Methods("POST")
+	router.HandleFunc("/uploads/{id:[A-Za-z0-9-_]+}/{filename:.+}", uploadFileGetHandler).Methods("GET")
 
 	srv := &http.Server{
 		Handler:      router,