Add custom character limit to pastes (#196)

# Background

Recently I've been looking at alternatives to the service 0x0.st for
pasting log files to. Logpaste seems like the perfect replacement, but
it has limits on file size. Adding the ability for administrators to add
custom file sizes would allow admins to make the file size the
equivalent of 0x0's (512 MiB) or even larger. It would also allow them
to set smaller limits as well if resources are limited or if the content
being pasted doesn't warrant large sizes.

# Changes

- The default limit is now `2 * 1024 * 1024`, or 2 MiB instead of `2 *
1000 * 1000`, 2 MB
- Add cli flag `-maxsize int` to allow admins to set an arbitrary limit
on paste file sizes if they would like to
- The argument is passed in by # of MiB (so for a 512MiB limit,
`-maxsize 512`, or for the default 2MiB, `-maxsize 2`)
- Add field `maxCharLimit` to the `defaultServer` struct for storing the
given size
- Add fields to `handlers/paste_test.go` to use the new struct field in
order for tests to pass
- Replace instances of `MaxPasteCharacters` with `s.maxCharLimit`

---------

Co-authored-by: Michael Lynch <[email protected]>

README.md

@@ -107,6 +107,7 @@ docker run \
 | `-footer`         | Footer to display on homepage (may include HTML)   |                                                        |
 | `-showdocs`       | Whether to display usage documentation on homepage | `true`                                                 |
 | `-perminutelimit` | Number of pastes to allow per IP per minute        | `0` (no limit)                                         |
+| `-maxsize`        | Max file size users can upload                     | `2` (2 MiB)                                            |
 
 ### Docker environment variables
 

cmd/logpaste/main.go

@@ -24,15 +24,19 @@ func main() {
 		true, "whether to display usage information on homepage")
 	perMinuteLimit := flag.Int("perminutelimit",
 		0, "number of pastes to allow per IP per minute (set to 0 to disable rate limiting)")
+	maxPasteMiB := flag.Int64("maxsize", 2, "max file size as MiB")
 
 	flag.Parse()
 
+	const charactersPerMiB = 1024 * 1024
+	maxCharLimit := *maxPasteMiB * charactersPerMiB
+
 	h := gorilla.LoggingHandler(os.Stdout, handlers.New(handlers.SiteProperties{
 		Title:      *title,
 		Subtitle:   *subtitle,
 		FooterHTML: *footer,
 		ShowDocs:   *showDocs,
-	}, *perMinuteLimit).Router())
+	}, *perMinuteLimit, maxCharLimit).Router())
 	if os.Getenv("PS_BEHIND_PROXY") != "" {
 		h = gorilla.ProxyIPHeadersHandler(h)
 	}

handlers/paste.go

@@ -16,8 +16,6 @@ import (
 	"github.com/mtlynch/logpaste/store"
 )
 
-const MaxPasteCharacters = 2 * 1000 * 1000
-
 type PastePutResponse struct {
 	Id string `json:"id"`
 }
@@ -54,15 +52,15 @@ func (s defaultServer) pastePut() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Access-Control-Allow-Origin", "*")
 
-		bodyRaw, err := io.ReadAll(http.MaxBytesReader(w, r.Body, MaxPasteCharacters))
+		bodyRaw, err := io.ReadAll(http.MaxBytesReader(w, r.Body, s.maxCharLimit))
 		if err != nil {
 			log.Printf("Error reading body: %v", err)
 			http.Error(w, "can't read request body", http.StatusBadRequest)
 			return
 		}
 
 		body := string(bodyRaw)
-		if !validatePaste(body, w) {
+		if !validatePaste(body, w, s.maxCharLimit) {
 			return
 		}
 
@@ -87,13 +85,12 @@ func (s defaultServer) pastePut() http.HandlerFunc {
 
 func (s defaultServer) pastePost() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		r.Body = http.MaxBytesReader(w, r.Body, MaxPasteCharacters+1024)
-		if err := r.ParseMultipartForm(MaxPasteCharacters); err != nil {
+		r.Body = http.MaxBytesReader(w, r.Body, s.maxCharLimit+1024)
+		if err := r.ParseMultipartForm(s.maxCharLimit); err != nil {
 			log.Printf("failed to parse form: %v", err)
 			http.Error(w, "no valid multipart/form-data found", http.StatusBadRequest)
 			return
 		}
-
 		w.Header().Set("Access-Control-Allow-Origin", "*")
 
 		body, ok := parsePasteFromMultipartForm(r.MultipartForm, w)
@@ -103,7 +100,7 @@ func (s defaultServer) pastePost() http.HandlerFunc {
 			return
 		}
 
-		if !validatePaste(body, w) {
+		if !validatePaste(body, w, s.maxCharLimit) {
 			return
 		}
 
@@ -127,12 +124,12 @@ func generateEntryId() string {
 	return random.String(8)
 }
 
-func validatePaste(p string, w http.ResponseWriter) bool {
+func validatePaste(p string, w http.ResponseWriter, maxCharLimit int64) bool {
 	if len(strings.TrimSpace(p)) == 0 {
 		log.Print("Paste body was empty")
 		http.Error(w, "empty body", http.StatusBadRequest)
 		return false
-	} else if len(p) > MaxPasteCharacters {
+	} else if int64(len(p)) > maxCharLimit {
 		log.Printf("Paste body was too long: %d characters", len(p))
 		http.Error(w, "body too long", http.StatusBadRequest)
 		return false

handlers/paste_test.go

@@ -13,6 +13,8 @@ import (
 	"github.com/mtlynch/logpaste/store"
 )
 
+const MaxPasteCharacters = 2 * 1024 * 1024
+
 type mockStore struct {
 	entries map[string]string
 }
@@ -41,8 +43,9 @@ func TestPasteGet(t *testing.T) {
 	}
 	router := mux.NewRouter()
 	s := defaultServer{
-		store:  &ds,
-		router: router,
+		store:        &ds,
+		router:       router,
+		maxCharLimit: MaxPasteCharacters,
 	}
 	s.routes()
 
@@ -129,8 +132,9 @@ func TestPastePut(t *testing.T) {
 			}
 			router := mux.NewRouter()
 			s := defaultServer{
-				store:  &ds,
-				router: router,
+				store:        &ds,
+				router:       router,
+				maxCharLimit: MaxPasteCharacters,
 			}
 			s.routes()
 
@@ -172,8 +176,9 @@ func TestPastePost(t *testing.T) {
 	}
 	router := mux.NewRouter()
 	s := defaultServer{
-		store:  &ds,
-		router: router,
+		store:        &ds,
+		router:       router,
+		maxCharLimit: MaxPasteCharacters,
 	}
 	s.routes()
 	for _, tt := range []struct {

handlers/server.go

@@ -12,12 +12,13 @@ type Server interface {
 	Router() *mux.Router
 }
 
-func New(sp SiteProperties, perMinuteLimit int) Server {
+func New(sp SiteProperties, perMinuteLimit int, maxCharLimit int64) Server {
 	s := defaultServer{
 		router:        mux.NewRouter(),
 		store:         sqlite.New(),
 		siteProps:     sp,
 		ipRateLimiter: limit.New(perMinuteLimit),
+		maxCharLimit:  maxCharLimit,
 	}
 	s.routes()
 	return s
@@ -35,6 +36,7 @@ type defaultServer struct {
 	store         store.Store
 	siteProps     SiteProperties
 	ipRateLimiter limit.IPRateLimiter
+	maxCharLimit  int64
 }
 
 // Router returns the underlying router interface for the server.