feat: anonymous beacons, video metadata stripping, remove beacon author exposure

- GetNearbyBeacons no longer returns author info (anonymous placeholder)
- Beacons excluded from profile posts (GetPostsByAuthor)
- Vouch/report notifications removed for beacon privacy
- MediaHandler strips all metadata (EXIF/GPS/device) via ffmpeg before R2 upload
- Flutter beacon UI shows 'Anonymous Beacon' instead of author info

go-backend/internal/handlers/media_handler.go

@@ -4,8 +4,9 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"mime/multipart"
 	"net/http"
+	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 	"time"
@@ -13,6 +14,7 @@ import (
 	"github.com/aws/aws-sdk-go-v2/service/s3"
 	"github.com/gin-gonic/gin"
 	"github.com/google/uuid"
+	"github.com/rs/zerolog/log"
 )
 
 // MediaHandler uploads media to Cloudflare R2. If s3Client is provided, it uses
@@ -70,6 +72,8 @@ func (h *MediaHandler) Upload(c *gin.Context) {
 		}
 	}
 
+	contentType := fileHeader.Header.Get("Content-Type")
+
 	userID := c.GetString("user_id")
 	if userID == "" {
 		userID = "anon"
@@ -88,11 +92,32 @@ func (h *MediaHandler) Upload(c *gin.Context) {
 		}
 	}
 
+	// Read the uploaded file into memory
+	src, err := fileHeader.Open()
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to read uploaded file"})
+		return
+	}
+	rawBytes, err := io.ReadAll(src)
+	src.Close()
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to read uploaded file"})
+		return
+	}
+
+	// Strip metadata (EXIF/GPS from images, all metadata from videos)
+	cleanBytes, stripErr := stripMetadata(rawBytes, mediaType, ext)
+	if stripErr != nil {
+		log.Warn().Err(stripErr).Str("type", mediaType).Msg("metadata strip failed, uploading original")
+		cleanBytes = rawBytes
+	}
+
 	var publicURL string
+	reader := bytes.NewReader(cleanBytes)
 	if h.useS3 {
-		publicURL, err = h.putObjectS3(c, fileHeader, targetBucket, objectKey, targetDomain)
+		publicURL, err = h.putObjectS3(c, reader, int64(len(cleanBytes)), contentType, targetBucket, objectKey, targetDomain)
 	} else {
-		publicURL, err = h.putObjectR2API(c, fileHeader, targetBucket, objectKey, targetDomain)
+		publicURL, err = h.putObjectR2API(c, cleanBytes, contentType, targetBucket, objectKey, targetDomain)
 	}
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("Failed to upload media: %v", err)})
@@ -105,25 +130,71 @@ func (h *MediaHandler) Upload(c *gin.Context) {
 		"signedUrl": publicURL,
 		"fileName":  objectKey,
 		"file_name": objectKey,
-		"fileSize":  fileHeader.Size,
-		"file_size": fileHeader.Size,
+		"fileSize":  len(cleanBytes),
+		"file_size": len(cleanBytes),
 		"type":      mediaType,
 	})
 }
 
-func (h *MediaHandler) putObjectS3(c *gin.Context, fileHeader *multipart.FileHeader, bucket string, key string, publicDomain string) (string, error) {
-	src, err := fileHeader.Open()
-	if err != nil {
-		return "", err
+// stripMetadata uses ffmpeg to remove all metadata (EXIF, GPS, camera info)
+// from uploaded media before it goes to R2. Returns the cleaned bytes.
+func stripMetadata(raw []byte, mediaType string, ext string) ([]byte, error) {
+	if _, err := exec.LookPath("ffmpeg"); err != nil {
+		return nil, fmt.Errorf("ffmpeg not found: %w", err)
 	}
-	defer src.Close()
 
+	tmpDir, err := os.MkdirTemp("", "sojorn-media-*")
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(tmpDir)
+
+	inPath := filepath.Join(tmpDir, "input"+ext)
+	outPath := filepath.Join(tmpDir, "output"+ext)
+
+	if err := os.WriteFile(inPath, raw, 0644); err != nil {
+		return nil, err
+	}
+
+	// Run ffmpeg: strip all metadata
+	var args []string
+	if mediaType == "video" {
+		// Copy streams without re-encoding, just drop metadata
+		args = []string{"-i", inPath, "-map_metadata", "-1", "-c", "copy", "-y", outPath}
+	} else {
+		// For images: re-encode to strip EXIF (ffmpeg decodes + encodes, drops metadata)
+		args = []string{"-i", inPath, "-map_metadata", "-1", "-y", outPath}
+	}
+
+	cmd := exec.Command("ffmpeg", args...)
+	var stderr bytes.Buffer
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		log.Warn().Str("stderr", stderr.String()).Msg("ffmpeg metadata strip stderr")
+		return nil, fmt.Errorf("ffmpeg failed: %w", err)
+	}
+
+	cleanBytes, err := os.ReadFile(outPath)
+	if err != nil {
+		return nil, err
+	}
+
+	log.Info().
+		Str("type", mediaType).
+		Int("original_size", len(raw)).
+		Int("stripped_size", len(cleanBytes)).
+		Msg("metadata stripped from upload")
+
+	return cleanBytes, nil
+}
+
+func (h *MediaHandler) putObjectS3(c *gin.Context, body io.ReadSeeker, contentLength int64, contentType string, bucket string, key string, publicDomain string) (string, error) {
 	ctx := c.Request.Context()
-	_, err = h.s3Client.PutObject(ctx, &s3.PutObjectInput{
+	_, err := h.s3Client.PutObject(ctx, &s3.PutObjectInput{
 		Bucket:      &bucket,
 		Key:         &key,
-		Body:        src,
-		ContentType: &[]string{fileHeader.Header.Get("Content-Type")}[0],
+		Body:        body,
+		ContentType: &contentType,
 	})
 	if err != nil {
 		return "", err
@@ -137,22 +208,11 @@ func (h *MediaHandler) putObjectS3(c *gin.Context, fileHeader *multipart.FileHea
 	return key, nil
 }
 
-func (h *MediaHandler) putObjectR2API(c *gin.Context, fileHeader *multipart.FileHeader, bucket string, key string, publicDomain string) (string, error) {
+func (h *MediaHandler) putObjectR2API(c *gin.Context, fileBytes []byte, contentType string, bucket string, key string, publicDomain string) (string, error) {
 	if h.accountID == "" || h.apiToken == "" {
 		return "", fmt.Errorf("R2 API credentials missing")
 	}
 
-	src, err := fileHeader.Open()
-	if err != nil {
-		return "", err
-	}
-	defer src.Close()
-
-	fileBytes, err := io.ReadAll(src)
-	if err != nil {
-		return "", err
-	}
-
 	endpoint := fmt.Sprintf("https://api.cloudflare.com/client/v4/accounts/%s/r2/buckets/%s/objects/%s",
 		h.accountID, bucket, key)
 
@@ -162,7 +222,7 @@ func (h *MediaHandler) putObjectR2API(c *gin.Context, fileHeader *multipart.File
 	}
 
 	req.Header.Set("Authorization", "Bearer "+h.apiToken)
-	req.Header.Set("Content-Type", fileHeader.Header.Get("Content-Type"))
+	req.Header.Set("Content-Type", contentType)
 
 	client := &http.Client{Timeout: 60 * time.Second}
 	resp, err := client.Do(req)

go-backend/internal/handlers/post_handler.go

@@ -791,27 +791,7 @@ func (h *PostHandler) VouchBeacon(c *gin.Context) {
 		return
 	}
 
-	// Get beacon details for notification
-	beacon, err := h.postRepo.GetPostByID(c.Request.Context(), beaconID, userIDStr.(string))
-	if err == nil && beacon.AuthorID.String() != userIDStr.(string) {
-		// Get actor details
-		actor, err := h.userRepo.GetProfileByID(c.Request.Context(), userIDStr.(string))
-		if err == nil && h.notificationService != nil {
-			metadata := map[string]interface{}{
-				"actor_name": actor.DisplayName,
-				"beacon_id":  beaconID,
-			}
-			h.notificationService.CreateNotification(
-				c.Request.Context(),
-				beacon.AuthorID.String(),
-				userIDStr.(string),
-				"beacon_vouch",
-				&beaconID,
-				nil,
-				metadata,
-			)
-		}
-	}
+	// Beacons are anonymous — no notifications sent to preserve privacy
 
 	c.JSON(http.StatusOK, gin.H{"message": "Beacon vouched successfully"})
 }
@@ -830,27 +810,7 @@ func (h *PostHandler) ReportBeacon(c *gin.Context) {
 		return
 	}
 
-	// Get beacon details for notification
-	beacon, err := h.postRepo.GetPostByID(c.Request.Context(), beaconID, userIDStr.(string))
-	if err == nil && beacon.AuthorID.String() != userIDStr.(string) {
-		// Get actor details
-		actor, err := h.userRepo.GetProfileByID(c.Request.Context(), userIDStr.(string))
-		if err == nil && h.notificationService != nil {
-			metadata := map[string]interface{}{
-				"actor_name": actor.DisplayName,
-				"beacon_id":  beaconID,
-			}
-			h.notificationService.CreateNotification(
-				c.Request.Context(),
-				beacon.AuthorID.String(),
-				userIDStr.(string),
-				"beacon_report",
-				&beaconID,
-				nil,
-				metadata,
-			)
-		}
-	}
+	// Beacons are anonymous — no notifications sent to preserve privacy
 
 	c.JSON(http.StatusOK, gin.H{"message": "Beacon reported successfully"})
 }

go-backend/internal/repository/post_repository.go

@@ -239,6 +239,7 @@ func (r *PostRepository) GetPostsByAuthor(ctx context.Context, authorID string,
 		JOIN public.profiles pr ON p.author_id = pr.id
 		LEFT JOIN public.post_metrics m ON p.id = m.post_id
 		WHERE p.author_id = $1::uuid AND p.deleted_at IS NULL AND p.status = 'active'
+		  AND p.is_beacon = FALSE
 		  AND (
 		      p.author_id = CASE WHEN $4 != '' THEN $4::uuid ELSE NULL END -- Viewer is author
 		      OR pr.is_private = FALSE -- Public profile
@@ -482,14 +483,14 @@ func (r *PostRepository) CreateComment(ctx context.Context, comment *models.Comm
 }
 
 func (r *PostRepository) GetNearbyBeacons(ctx context.Context, lat float64, long float64, radius int) ([]models.Post, error) {
+	// Beacons are anonymous: we never expose author info to the API.
+	// author_id is stored internally for abuse tracking only.
 	query := `
 		SELECT 
-			p.id, p.author_id, p.category_id, p.body, COALESCE(p.image_url, ''), p.tags, p.created_at,
+			p.id, p.category_id, p.body, COALESCE(p.image_url, ''), p.tags, p.created_at,
 			p.beacon_type, p.confidence_score, p.is_active_beacon,
-			ST_Y(p.location::geometry) as lat, ST_X(p.location::geometry) as long,
-			pr.handle as author_handle, pr.display_name as author_display_name, COALESCE(pr.avatar_url, '') as author_avatar_url
+			ST_Y(p.location::geometry) as lat, ST_X(p.location::geometry) as long
 		FROM public.posts p
-		JOIN public.profiles pr ON p.author_id = pr.id
 		WHERE p.is_beacon = true 
 		  AND ST_DWithin(p.location, ST_SetSRID(ST_Point($2, $1), 4326)::geography, $3)
 		  AND p.status = 'active'
@@ -505,18 +506,20 @@ func (r *PostRepository) GetNearbyBeacons(ctx context.Context, lat float64, long
 	for rows.Next() {
 		var p models.Post
 		err := rows.Scan(
-			&p.ID, &p.AuthorID, &p.CategoryID, &p.Body, &p.ImageURL, &p.Tags, &p.CreatedAt,
+			&p.ID, &p.CategoryID, &p.Body, &p.ImageURL, &p.Tags, &p.CreatedAt,
 			&p.BeaconType, &p.Confidence, &p.IsActiveBeacon, &p.Lat, &p.Long,
-			&p.AuthorHandle, &p.AuthorDisplayName, &p.AuthorAvatarURL,
 		)
 		if err != nil {
 			return nil, err
 		}
+		// Return anonymous author placeholder — no real user info
+		p.AuthorHandle = "Anonymous"
+		p.AuthorDisplayName = "Anonymous"
+		p.AuthorAvatarURL = ""
 		p.Author = &models.AuthorProfile{
-			ID:          p.AuthorID,
-			Handle:      p.AuthorHandle,
-			DisplayName: p.AuthorDisplayName,
-			AvatarURL:   p.AuthorAvatarURL,
+			Handle:      "Anonymous",
+			DisplayName: "Anonymous",
+			AvatarURL:   "",
 		}
 		beacons = append(beacons, p)
 	}

sojorn_app/lib/screens/beacon/beacon_bottom_sheet.dart

@@ -86,28 +86,20 @@ class _BeaconBottomSheetState extends ConsumerState<BeaconBottomSheet> {
             style: theme.textTheme.bodyLarge,
           ),
           const SizedBox(height: 16),
-          // Author info
+          // Anonymous beacon info
           Row(
             children: [
               CircleAvatar(
                 radius: 16,
-                backgroundColor: accentColor,
-                backgroundImage: (post.author?.avatarUrl != null && post.author!.avatarUrl!.isNotEmpty)
-                    ? NetworkImage(post.author!.avatarUrl!)
-                    : null,
-                child: (post.author?.avatarUrl == null || post.author!.avatarUrl!.isEmpty)
-                    ? Text(
-                        ((post.author?.displayName ?? post.author?.handle ?? '?')[0]).toUpperCase(),
-                        style: const TextStyle(color: Colors.white),
-                      )
-                    : null,
+                backgroundColor: accentColor.withValues(alpha: 0.2),
+                child: Icon(Icons.shield, size: 18, color: accentColor),
               ),
               const SizedBox(width: 12),
               Column(
                 crossAxisAlignment: CrossAxisAlignment.start,
                 children: [
                   Text(
-                    post.author?.displayName ?? '@${post.author?.handle ?? 'unknown'}',
+                    'Anonymous Beacon',
                     style: theme.textTheme.titleSmall?.copyWith(
                       fontWeight: FontWeight.bold,
                     ),

sojorn_app/lib/screens/beacon/beacon_detail_screen.dart

@@ -352,25 +352,14 @@ class _BeaconDetailScreenState extends ConsumerState<BeaconDetailScreen>
   }
 
   Widget _buildAuthorInfo() {
-    final author = _post.author;
-    if (author == null) return const SizedBox.shrink();
-
     return Padding(
       padding: const EdgeInsets.all(20),
       child: Row(
         children: [
           CircleAvatar(
             radius: 20,
-            backgroundColor: AppTheme.egyptianBlue,
-            backgroundImage: (author.avatarUrl != null && author.avatarUrl!.isNotEmpty)
-                ? NetworkImage(author.avatarUrl!)
-                : null,
-            child: (author.avatarUrl == null || author.avatarUrl!.isEmpty)
-                ? Text(
-                    ((author.displayName ?? author.handle ?? '?')[0]).toUpperCase(),
-                    style: const TextStyle(color: Colors.white),
-                  )
-                : null,
+            backgroundColor: AppTheme.egyptianBlue.withValues(alpha: 0.2),
+            child: const Icon(Icons.shield, size: 22, color: AppTheme.egyptianBlue),
           ),
           const SizedBox(width: 12),
           Expanded(
@@ -378,16 +367,15 @@ class _BeaconDetailScreenState extends ConsumerState<BeaconDetailScreen>
               crossAxisAlignment: CrossAxisAlignment.start,
               children: [
                 Text(
-                  author.displayName ?? '@${author.handle ?? 'unknown'}',
+                  'Anonymous Beacon',
                   style: AppTheme.headlineSmall,
                 ),
-                if (author.handle != null && author.handle!.isNotEmpty)
-                  Text(
-                    '@${author.handle}',
-                    style: AppTheme.bodyMedium?.copyWith(
-                      color: AppTheme.textDisabled,
-                    ),
+                Text(
+                  'Beacons are posted anonymously for community safety',
+                  style: AppTheme.bodyMedium?.copyWith(
+                    color: AppTheme.textDisabled,
                   ),
+                ),
               ],
             ),
           ),