[PM-25427] Allow reading mail templates from disk (#6123)

* Allow reading mail templates from self host disk

* Update src/Core/Services/Implementations/HandlebarsMailService.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/Core/Services/Implementations/HandlebarsMailService.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* tweak logic

* some error handling reading templates from disk

* fix: broken test

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Andreas Coroiu <andreas.coroiu@gmail.com>

src/Core/Services/Implementations/HandlebarsMailService.cs

@@ -26,6 +26,7 @@ using Bit.Core.Vault.Models.Data;
 using Core.Auth.Enums;
 using HandlebarsDotNet;
 using Microsoft.Extensions.Caching.Distributed;
+using Microsoft.Extensions.Logging;
 
 namespace Bit.Core.Services;
 
@@ -39,6 +40,7 @@ public class HandlebarsMailService : IMailService
     private readonly IMailDeliveryService _mailDeliveryService;
     private readonly IMailEnqueuingService _mailEnqueuingService;
     private readonly IDistributedCache _distributedCache;
+    private readonly ILogger<HandlebarsMailService> _logger;
     private readonly Dictionary<string, HandlebarsTemplate<object, object>> _templateCache = new();
 
     private bool _registeredHelpersAndPartials = false;
@@ -47,12 +49,14 @@ public class HandlebarsMailService : IMailService
         GlobalSettings globalSettings,
         IMailDeliveryService mailDeliveryService,
         IMailEnqueuingService mailEnqueuingService,
-        IDistributedCache distributedCache)
+        IDistributedCache distributedCache,
+        ILogger<HandlebarsMailService> logger)
     {
         _globalSettings = globalSettings;
         _mailDeliveryService = mailDeliveryService;
         _mailEnqueuingService = mailEnqueuingService;
         _distributedCache = distributedCache;
+        _logger = logger;
     }
 
     public async Task SendVerifyEmailEmailAsync(string email, Guid userId, string token)
@@ -708,6 +712,12 @@ public class HandlebarsMailService : IMailService
 
     private async Task<string?> ReadSourceAsync(string templateName)
     {
+        var diskSource = await ReadSourceFromDiskAsync(templateName);
+        if (!string.IsNullOrWhiteSpace(diskSource))
+        {
+            return diskSource;
+        }
+
         var assembly = typeof(HandlebarsMailService).GetTypeInfo().Assembly;
         var fullTemplateName = $"{Namespace}.{templateName}.hbs";
         if (!assembly.GetManifestResourceNames().Any(f => f == fullTemplateName))
@@ -721,6 +731,42 @@ public class HandlebarsMailService : IMailService
         }
     }
 
+    private async Task<string?> ReadSourceFromDiskAsync(string templateName)
+    {
+        if (!_globalSettings.SelfHosted)
+        {
+            return null;
+        }
+        try
+        {
+            var templateFileSuffix = ".html";
+            if (templateName.EndsWith(".txt"))
+            {
+                templateFileSuffix = ".txt";
+            }
+            else if (!templateName.EndsWith(".html"))
+            {
+                // unexpected suffix
+                return null;
+            }
+            var suffixPosition = templateName.LastIndexOf(templateFileSuffix);
+            var templateNameNoSuffix = templateName.Substring(0, suffixPosition);
+            var templatePathNoSuffix = templateNameNoSuffix.Replace(".", "/");
+            var diskPath = $"{_globalSettings.MailTemplateDirectory}/{templatePathNoSuffix}{templateFileSuffix}.hbs";
+            var directory = Path.GetDirectoryName(diskPath);
+            if (Directory.Exists(directory) && File.Exists(diskPath))
+            {
+                var fileContents = await File.ReadAllTextAsync(diskPath);
+                return fileContents;
+            }
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to read mail template from disk.");
+        }
+        return null;
+    }
+
     private async Task RegisterHelpersAndPartialsAsync()
     {
         if (_registeredHelpersAndPartials)

src/Core/Settings/GlobalSettings.cs

@@ -8,6 +8,7 @@ namespace Bit.Core.Settings;
 
 public class GlobalSettings : IGlobalSettings
 {
+    private string _mailTemplateDirectory;
     private string _logDirectory;
     private string _licenseDirectory;
 
@@ -37,6 +38,11 @@ public class GlobalSettings : IGlobalSettings
         get => BuildDirectory(_licenseDirectory, "/core/licenses");
         set => _licenseDirectory = value;
     }
+    public virtual string MailTemplateDirectory
+    {
+        get => BuildDirectory(_mailTemplateDirectory, "/mail-templates");
+        set => _mailTemplateDirectory = value;
+    }
     public string LicenseCertificatePassword { get; set; }
     public virtual string PushRelayBaseUri { get; set; }
     public virtual string InternalIdentityKey { get; set; }

test/Core.Test/Services/HandlebarsMailServiceTests.cs

@@ -23,6 +23,7 @@ public class HandlebarsMailServiceTests
     private readonly IMailDeliveryService _mailDeliveryService;
     private readonly IMailEnqueuingService _mailEnqueuingService;
     private readonly IDistributedCache _distributedCache;
+    private readonly ILogger<HandlebarsMailService> _logger;
 
     public HandlebarsMailServiceTests()
     {
@@ -30,12 +31,14 @@ public class HandlebarsMailServiceTests
         _mailDeliveryService = Substitute.For<IMailDeliveryService>();
         _mailEnqueuingService = Substitute.For<IMailEnqueuingService>();
         _distributedCache = Substitute.For<IDistributedCache>();
+        _logger = Substitute.For<ILogger<HandlebarsMailService>>();
 
         _sut = new HandlebarsMailService(
             _globalSettings,
             _mailDeliveryService,
             _mailEnqueuingService,
-            _distributedCache
+            _distributedCache,
+            _logger
         );
     }
 
@@ -217,8 +220,9 @@ public class HandlebarsMailServiceTests
 
         var mailDeliveryService = new MailKitSmtpMailDeliveryService(globalSettings, Substitute.For<ILogger<MailKitSmtpMailDeliveryService>>());
         var distributedCache = Substitute.For<IDistributedCache>();
+        var logger = Substitute.For<ILogger<HandlebarsMailService>>();
 
-        var handlebarsService = new HandlebarsMailService(globalSettings, mailDeliveryService, new BlockingMailEnqueuingService(), distributedCache);
+        var handlebarsService = new HandlebarsMailService(globalSettings, mailDeliveryService, new BlockingMailEnqueuingService(), distributedCache, logger);
 
         var sendMethods = typeof(IMailService).GetMethods(BindingFlags.Public | BindingFlags.Instance)
             .Where(m => m.Name.StartsWith("Send") && m.Name != "SendEnqueuedMailMessageAsync");