fix: Handle duplicate content-IDs gracefully with warnings - Resolves #1874 (#1876)

Co-authored-by: smtp4dev-automation <[email protected]>

Author: rnwood

Rnwood.Smtp4dev/ApiModel/Message.cs

@@ -1,12 +1,13 @@
-using MimeKit;
+using Microsoft.AspNetCore.Mvc;
+using MimeKit;
+using Rnwood.Smtp4dev.Migrations;
 using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Security.Cryptography;
 using System.Text;
-using Microsoft.AspNetCore.Mvc;
 using System.Text.Json.Serialization;
-using Rnwood.Smtp4dev.Migrations;
 
 namespace Rnwood.Smtp4dev.ApiModel
 {
@@ -88,6 +89,18 @@ public Message(DbModel.Message dbMessage)
                 Parts.Add(HandleMimeEntity(MimeMessage.Body));
                 HasHtmlBody = MimeMessage.HtmlBody != null;
                 HasPlainTextBody = MimeMessage.TextBody != null;
+
+                var duplicateCids = Parts.Flatten(p => p.ChildParts)
+                    .Where(p => !string.IsNullOrEmpty(p.ContentId))
+                    .GroupBy(p => p.ContentId)
+                    .Where(g => g.Count() > 1)
+                    .Select(g => g.Key)
+                    .ToList();
+
+                if (duplicateCids.Any())
+                {
+                    Warnings.Add(new MessageWarning { Details = $"Non unique MIME Content-Id headers found: {string.Join(", ", duplicateCids.Select(cid => string.Concat("'", cid, "'")))}" });
+                }
             }
         }
 

Rnwood.Smtp4dev/ApiModel/MessageSummary.cs

@@ -1,5 +1,7 @@
 using Rnwood.Smtp4dev.Migrations;
+using Rnwood.Smtp4dev.Server;
 using System;
+using System.Text.Json;
 using System.Text.Json.Serialization;
 
 namespace Rnwood.Smtp4dev.ApiModel
@@ -31,7 +33,13 @@ public MessageSummary(DbModel.Projections.MessageSummaryProjection messagesSumma
             IsUnread = messagesSummaryProjection.IsUnread;
             IsRelayed = messagesSummaryProjection.IsRelayed;
             DeliveredTo = messagesSummaryProjection.DeliveredTo;
-            HasWarnings = messagesSummaryProjection.HasBareLineFeed;
+
+            MimeMetadata mimeMetadata = !string.IsNullOrEmpty(messagesSummaryProjection.MimeMetadata) ?
+                JsonSerializer.Deserialize<MimeMetadata>(messagesSummaryProjection.MimeMetadata)
+                : null;
+
+            HasWarnings = messagesSummaryProjection.HasBareLineFeed
+            || (mimeMetadata?.HasDuplicatedContentIds.GetValueOrDefault() ?? false);
         }
 
         public bool IsRelayed { get; set; }

Rnwood.Smtp4dev/ClientApp/src/components/messageviewhtml.vue

@@ -1,6 +1,6 @@
 <template>
 
-    <div class="hfillpanel" v-loading="!html">
+    <div class="hfillpanel" v-loading="loading">
 
         <div class="toolbar">
             <el-select style="flex: 1 0 200px;" v-model="selectedViewportSizeName" filterable @change="viewportRotate=false">

Rnwood.Smtp4dev/Controllers/MessagesController.cs

@@ -418,7 +418,7 @@ public async Task<ActionResult<string>> GetMessageHtml(Guid id)
                 {
                     string cid = imageElement.Attributes["src"].Value.Replace("cid:", "", StringComparison.OrdinalIgnoreCase);
 
-                    var part = message.Parts.Flatten(p => p.ChildParts).SingleOrDefault(p => p.ContentId == cid);
+                    var part = message.Parts.Flatten(p => p.ChildParts).FirstOrDefault(p => p.ContentId == cid);
 
                     imageElement.Attributes["src"].Value = $"api/Messages/{id.ToString()}/part/{part?.Id ?? "notfound"}/content";
                 }

Rnwood.Smtp4dev/Server/MimeMetadata.cs

@@ -43,5 +43,8 @@ public class MimeMetadata
         /// </summary>
         [JsonPropertyName("partCount")]
         public int PartCount { get; set; }
+
+        [JsonPropertyName("hasDuplicatedContentIds")]
+        public bool? HasDuplicatedContentIds { get; set; }
     }
 }

Rnwood.Smtp4dev/Server/MimeProcessingService.cs

@@ -56,7 +56,7 @@ public MimeMetadata ExtractMimeMetadata(MimeMessage mime)
                 }
 
                 // Extract attachment filenames and body content info
-                ExtractPartMetadata(mime.Body, metadata);
+                ExtractPartMetadata(mime.Body, metadata, new HashSet<string>());
 
                 // Set content type
                 metadata.ContentType = mime.Body?.ContentType?.MimeType ?? "";
@@ -69,12 +69,20 @@ public MimeMetadata ExtractMimeMetadata(MimeMessage mime)
             return metadata;
         }
 
-        public void ExtractPartMetadata(MimeEntity entity, MimeMetadata metadata)
+        public void ExtractPartMetadata(MimeEntity entity, MimeMetadata metadata, HashSet<string> seenContentIds)
         {
             if (entity == null) return;
 
             metadata.PartCount++;
 
+            if (!string.IsNullOrEmpty(entity.ContentId) && seenContentIds.Contains(entity.ContentId))
+            {
+                metadata.HasDuplicatedContentIds = true;
+            } else
+            {
+                seenContentIds.Add(entity.ContentId);
+            }
+
             // Check for attachments
             if (entity.IsAttachment)
             {
@@ -101,7 +109,7 @@ public void ExtractPartMetadata(MimeEntity entity, MimeMetadata metadata)
             {
                 foreach (var part in multipart)
                 {
-                    ExtractPartMetadata(part, metadata);
+                    ExtractPartMetadata(part, metadata, seenContentIds);
                 }
             }
         }