fix(web): 429 for a busy queue; a non-UUID id and a malformed or odd-byte title are 4xx or cleaned, never 500 (review F6, F7)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/web/uploads.go

@@ -8,8 +8,10 @@ import (
 	"math"
 	"net/http"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"time"
+	"unicode"
 	"unicode/utf8"
 
 	"github.com/a-h/templ"
@@ -92,13 +94,26 @@ func (a *App) handleUploadPost(w http.ResponseWriter, r *http.Request) {
 			break
 		}
 		if err != nil {
+			var tooBig *http.MaxBytesError
+			if !errors.As(err, &tooBig) {
+				// A malformed multipart body (a header with a control byte, a truncated
+				// part) is the sender's to fix: a 400, not a server error, and the error
+				// text is never logged: it quotes the headers, which carry the file name.
+				a.logger().Info("upload rejected", "reason", "malformed")
+				a.renderUploadsPage(w, r, userID, http.StatusBadRequest, "That upload could not be read. Please try again.")
+				return
+			}
 			a.uploadFailure(w, r, userID, err)
 			return
 		}
 		switch part.FormName() {
 		case "title":
-			b, _ := io.ReadAll(io.LimitReader(part, maxTitleRunes*utf8.UTFMax))
+			b, err := io.ReadAll(io.LimitReader(part, maxTitleRunes*utf8.UTFMax))
-			title = clipRunes(strings.TrimSpace(string(b)), maxTitleRunes)
+			if err != nil {
+				a.renderUploadsPage(w, r, userID, http.StatusBadRequest, "That upload could not be read. Please try again.")
+				return
+			}
+			title = cleanTitle(string(b))
 		case "file":
 			if title == "" {
 				title = titleFromFilename(part.FileName())
@@ -126,8 +141,11 @@ func (a *App) uploadFailure(w http.ResponseWriter, r *http.Request, userID strin
 		// Logged by reason only: the filename and title are private content.
 		a.logger().Info("upload rejected", "reason", string(rej.Reason))
 		status := http.StatusUnprocessableEntity
-		if rej.Reason == uploads.ReasonTooLarge {
+		switch rej.Reason {
+		case uploads.ReasonTooLarge:
 			status = http.StatusRequestEntityTooLarge
+		case uploads.ReasonBusy:
+			status = http.StatusTooManyRequests
 		}
 		a.renderUploadsPage(w, r, userID, status, rej.Message)
 	case errors.As(err, &tooBig):
@@ -168,7 +186,14 @@ func (a *App) loadOwnedUpload(w http.ResponseWriter, r *http.Request) (*domain.U
 	if !ok {
 		return nil, false
 	}
-	u, err := a.Store.GetUpload(r.Context(), userID, r.PathValue("id"))
+	id := r.PathValue("id")
+	if !uuidShape.MatchString(id) {
+		// Not an id at all: the same 404 as an unknown or foreign one, never a database
+		// error that surfaces as a 500 (and no oracle about which ids exist).
+		http.NotFound(w, r)
+		return nil, false
+	}
+	u, err := a.Store.GetUpload(r.Context(), userID, id)
 	if errors.Is(err, store.ErrUploadNotFound) {
 		http.NotFound(w, r)
 		return nil, false
@@ -183,11 +208,29 @@ func (a *App) loadOwnedUpload(w http.ResponseWriter, r *http.Request) (*domain.U
 // titleFromFilename is the default title: the file's name without its extension.
 func titleFromFilename(name string) string {
 	base := filepath.Base(name)
-	t := strings.TrimSuffix(base, filepath.Ext(base))
+	t := cleanTitle(strings.TrimSuffix(base, filepath.Ext(base)))
 	if t == "" || t == "." {
 		return "Untitled recording"
 	}
-	return clipRunes(t, maxTitleRunes)
+	return t
+}
+
+// uuidShape is the form of an upload id. Anything else cannot be one, so it is a 404.
+var uuidShape = regexp.MustCompile(`^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$`)
+
+// cleanTitle makes a title safe to store and show: invalid UTF-8 dropped, control
+// characters (NUL, newlines, escapes) turned into spaces, runs of space collapsed, trimmed
+// and clipped. A title is cosmetic; bad bytes in it must never fail an upload, and Postgres
+// refuses NUL in text.
+func cleanTitle(s string) string {
+	s = strings.ToValidUTF8(s, "")
+	s = strings.Map(func(r rune) rune {
+		if unicode.IsControl(r) {
+			return ' '
+		}
+		return r
+	}, s)
+	return clipRunes(strings.Join(strings.Fields(s), " "), maxTitleRunes)
 }
 
 func clipRunes(s string, n int) string {
@@ -203,6 +246,8 @@ func uploadFailureMessage(k domain.UploadErrorKind) string {
 	switch k {
 	case domain.UploadErrInterrupted:
 		return "The server restarted before this recording was transcribed. Please upload it again."
+	case domain.UploadErrBusy:
+		return "Too many recordings were waiting to be transcribed when this one was uploaded. Please upload it again in a few minutes."
 	case domain.UploadErrTooLong:
 		return "This recording is longer than the limit once its audio is read (the file's header said otherwise). Please upload a shorter recording."
 	case domain.UploadErrIncomplete: