feat(upload): auto-detect file content-type if not sent #5361

martinconic · 2026-04-15T11:54:08Z

Is this necessary?

Before my changes the dirUploadHandler was accepting contentTypeString (although it is present request).
So I changed that here and did trim and set the new value in main handler.

I think that I agree with @martinconic that this is not really clear why this is needed. If you're already reading, cleaning, parsing and checking the content type header - it does not make any more sense to update the value in the Header type.

martinconic · 2026-04-15T11:55:37Z

Maybe a test for empty content type if there is none? Also if no content type and no body?

martinconic · 2026-04-15T11:59:15Z

The comment is not relevant anymore, right? the header is not validated by the caller. Maybe something like this:

// Parse error is ignored; unsupported media types are caught by the default case below.

, or do we want to validate here?

-Original file line number
+Diff line change
@@ Expand Up / @@ -342,7 +342,7 @@ paths: @@
         post:
           summary: "Upload a file or collection of files"
           description:
-            "Upload single files or collections of files. To upload a collection, send a multipart request with files in the form data with appropriate headers. Tar files can be uploaded with the `swarm-collection` header to extract and upload the directory structure. Without the `swarm-collection` header, requests are treated as single file uploads. Multipart requests are always treated as collections; use the `swarm-index-document` header to specify a single file to serve."
+            "Upload single files or collections of files. For a single file, `Content-Type` is optional: when present it is stored as metadata as-is; when absent the server infers a type from the start of the body. To upload a collection, send a multipart request with files in the form data with appropriate headers. Tar files can be uploaded with the `swarm-collection` header to extract and upload the directory structure. Without the `swarm-collection` header, requests are treated as single file uploads. Multipart requests are always treated as collections; use the `swarm-index-document` header to specify a single file to serve."
           tags:
             - BZZ
           parameters:
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -1176,7 +1176,7 @@ components: @@
           name: Content-Type
           schema:
             type: string
-          description: The specified content-type is preserved for download of the asset
+          description: "Single file: trimmed Content-Type is stored as-is or, if omitted or empty, inferred from the first bytes without validating against the body; tar (`swarm-collection`) and multipart collection uploads still need a full-body Content-Type (e.g. `application/x-tar` or `multipart/form-data` with boundary) so the request can be parsed."
         SwarmIndexDocumentParameter:
           in: header
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -16,7 +16,6 @@ import ( @@
     	"io"
     	"math"
     	"math/big"
-    	"mime"
     	"net/http"
     	"reflect"
     	"strconv"
@@ Expand Down Expand Up / @@ -302,10 +301,6 @@ func New( @@
     	s.chainBackend = chainBackend
     	s.metricsRegistry = newDebugMetrics()
     	s.preMapHooks = map[string]func(v string) (string, error){
-    		"mimeMediaType": func(v string) (string, error) {
-    			typ, _, err := mime.ParseMediaType(v)
-    			return typ, err
-    		},
     		"decBase64url": func(v string) (string, error) {
     			buf, err := base64.URLEncoding.DecodeString(v)
     			return string(buf), err
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -5,10 +5,13 @@ @@
     package api
     import (
+    	"bytes"
     	"context"
     	"encoding/hex"
     	"errors"
     	"fmt"
+    	"io"
+    	"mime"
     	"net/http"
     	"path"
     	"path/filepath"
@@ Expand Down Expand Up / @@ -51,6 +54,8 @@ const ( @@
     	largeFileBufferSize = 16 * 32 * 1024
     	largeBufferFilesizeThreshold = 10 * 1000000 // ten megs
+    	contentTypeSniffLen = 512
     )
     func lookaheadBufferSize(size int64) int {
@@ Expand All @@
     	defer span.Finish()
     	headers := struct {
-    		ContentType    string           `map:"Content-Type,mimeMediaType" validate:"required"`
+    		ContentType    string           `map:"Content-Type"`
     		BatchID        []byte           `map:"Swarm-Postage-Batch-Id" validate:"required"`
     		SwarmTag       uint64           `map:"Swarm-Tag"`
     		Pin            bool             `map:"Swarm-Pin"`
@@ Expand Down Expand Up @@
     		logger:         logger,
     	}
-    	if headers.IsDir || headers.ContentType == multiPartFormData {
-    		s.dirUploadHandler(ctx, logger, span, ow, r, putter, r.Header.Get(ContentTypeHeader), headers.Encrypt, tag, headers.RLevel, headers.Act, headers.HistoryAddress)
+    	contentTypeHdr := strings.TrimSpace(headers.ContentType)
+    	r.Header.Set(ContentTypeHeader, contentTypeHdr)
+    	mt, _, errParseCT := mime.ParseMediaType(contentTypeHdr)
+    	isMultipart := errParseCT == nil && mt == multiPartFormData
+    	isDirUpload := headers.IsDir || isMultipart
+    	if !isDirUpload {
+    		s.fileUploadHandler(ctx, logger, span, ow, r, putter, headers.Encrypt, tag, headers.RLevel, headers.Act, headers.HistoryAddress)
+    		return
+    	}
+    	if contentTypeHdr == "" {
+    		logger.Error(nil, "content-type required for directory upload")
+    		jsonhttp.BadRequest(w, errInvalidContentType)
     		return
     	}
-    	s.fileUploadHandler(ctx, logger, span, ow, r, putter, headers.Encrypt, tag, headers.RLevel, headers.Act, headers.HistoryAddress)
+    	s.dirUploadHandler(ctx, logger, span, ow, r, putter, headers.Encrypt, tag, headers.RLevel, headers.Act, headers.HistoryAddress)
     }
     // bzzUploadResponse is returned when an HTTP request to upload a file is successful
@@ Expand Down Expand Up / @@ -174,8 +192,24 @@ func (s *Service) fileUploadHandler( @@
     	p := requestPipelineFn(putter, encrypt, rLevel)
+    	var body io.Reader = r.Body
+    	if r.Header.Get(ContentTypeHeader) == "" {
+    		sniffBuf := make([]byte, contentTypeSniffLen)
+    		n, err := io.ReadFull(r.Body, sniffBuf)
+    		sniffBuf = sniffBuf[:n]
+    		if err != nil && !errors.Is(err, io.EOF) && !errors.Is(err, io.ErrUnexpectedEOF) {
+    			logger.Debug("body read failed", "file_name", queries.FileName, "error", err)
+    			logger.Error(nil, "body read failed", "file_name", queries.FileName)
+    			jsonhttp.BadRequest(w, "failed to read request body")
+    			return
+    		}
+    		r.Header.Set(ContentTypeHeader, http.DetectContentType(sniffBuf))
+    		body = io.MultiReader(bytes.NewReader(sniffBuf), r.Body)
+    	}
     	// first store the file and get its reference
-    	fr, err := p(ctx, r.Body)
+    	fr, err := p(ctx, body)
     	if err != nil {
     		logger.Debug("file store failed", "file_name", queries.FileName, "error", err)
     		logger.Error(nil, "file store failed", "file_name", queries.FileName)
@@ Expand Down Expand Up / @@ -240,7 +274,7 @@ func (s *Service) fileUploadHandler( @@
     	}
     	fileMtdt := map[string]string{
-    		manifest.EntryMetadataContentTypeKey: r.Header.Get(ContentTypeHeader), // Content-Type has already been validated.
+    		manifest.EntryMetadataContentTypeKey: r.Header.Get(ContentTypeHeader),
     		manifest.EntryMetadataFilenameKey:    queries.FileName,
     	}
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -465,6 +465,44 @@ func TestBzzFiles(t *testing.T) { @@
     		)
     	})
+    	t.Run("omit-content-type-uses-sniff", func(t *testing.T) {
+    		fileName := "plain.txt"
+    		var resp api.BzzUploadResponse
+    		jsonhttptest.Request(t, client, http.MethodPost, fileUploadResource+"?name="+fileName, http.StatusCreated,
+    			jsonhttptest.WithRequestHeader(api.SwarmDeferredUploadHeader, "true"),
+    			jsonhttptest.WithRequestHeader(api.SwarmPostageBatchIdHeader, batchOkStr),
+    			jsonhttptest.WithRequestBody(bytes.NewReader(simpleData)),
+    			jsonhttptest.WithUnmarshalJSONResponse(&resp),
+    		)
+    		rootHash := resp.Reference.String()
+    		jsonhttptest.Request(t, client, http.MethodGet, fileDownloadResource(rootHash), http.StatusOK,
+    			jsonhttptest.WithExpectedResponse(simpleData),
+    			jsonhttptest.WithExpectedContentLength(len(simpleData)),
+    			jsonhttptest.WithExpectedResponseHeader(api.ContentTypeHeader, "text/plain; charset=utf-8"),
+    			jsonhttptest.WithExpectedResponseHeader(api.ContentDispositionHeader, fmt.Sprintf(`inline; filename="%s"`, fileName)),
+    		)
+    	})
+    	t.Run("image-content-type-preserved", func(t *testing.T) {
+    		ct := "image/png"
+    		fileName := "test.txt"
+    		var resp api.BzzUploadResponse
+    		jsonhttptest.Request(t, client, http.MethodPost, fileUploadResource+"?name="+fileName, http.StatusCreated,
+    			jsonhttptest.WithRequestHeader(api.SwarmDeferredUploadHeader, "true"),
+    			jsonhttptest.WithRequestHeader(api.SwarmPostageBatchIdHeader, batchOkStr),
+    			jsonhttptest.WithRequestHeader(api.ContentTypeHeader, ct),
+    			jsonhttptest.WithRequestBody(bytes.NewReader(simpleData)),
+    			jsonhttptest.WithUnmarshalJSONResponse(&resp),
+    		)
+    		rootHash := resp.Reference.String()
+    		jsonhttptest.Request(t, client, http.MethodGet, fileDownloadResource(rootHash), http.StatusOK,
+    			jsonhttptest.WithExpectedResponse(simpleData),
+    			jsonhttptest.WithExpectedContentLength(len(simpleData)),
+    			jsonhttptest.WithExpectedResponseHeader(api.ContentTypeHeader, ct),
+    			jsonhttptest.WithExpectedResponseHeader(api.ContentDispositionHeader, fmt.Sprintf(`inline; filename="%s"`, fileName)),
+    		)
+    	})
     	t.Run("upload-then-download-and-check-data", func(t *testing.T) {
     		fileName := "sample.html"
     		rootHash := "36e6c1bbdfee6ac21485d5f970479fd1df458d36df9ef4e8179708ed46da557f"
@@ Expand Down @@

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feat(upload): auto-detect file content-type if not sent #5361

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martinconic Apr 15, 2026

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akrem-chabchoub Apr 16, 2026

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acud Apr 16, 2026

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martinconic Apr 15, 2026

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martinconic Apr 15, 2026

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-Original file line number
+Diff line change
@@ Expand Up / @@ -44,7 +44,6 @@ func (s *Service) dirUploadHandler( @@
     	w http.ResponseWriter,
     	r *http.Request,
     	putter storer.PutterSession,
-    	contentTypeString string,
     	encrypt bool,
     	tag uint64,
     	rLevel redundancy.Level,
@@ Expand All / @@ -58,7 +57,7 @@ func (s *Service) dirUploadHandler( @@
     	}
     	// The error is ignored because the header was already validated by the caller.
-    	mediaType, params, _ := mime.ParseMediaType(contentTypeString)
+    	mediaType, params, _ := mime.ParseMediaType(r.Header.Get(ContentTypeHeader))
     	var dReader dirReader
     	switch mediaType {
@@ Expand Down @@

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martinconic Apr 15, 2026

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martinconic Apr 15, 2026

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