GM.FileStorage.AzureBlob 6.0.0

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GM.FileStorage

A provider-agnostic file/blob storage abstraction for .NET. Depend on one interface — IFileStorageService — with streaming upload/download (no loading large files into memory), metadata + SHA-256 checksum validation, presigned URLs, and a pluggable key/path strategy (e.g. tenant/user-scoped folders). The backend is chosen by configuration, so switching disk → S3 → Azure Blob is a config change, not a code change. Targets .NET 10.

Packages

Core has no provider dependencies; each backend is its own package (like GM.Messaging / its transports). They version and release in lockstep:

dotnet add package GM.FileStorage
dotnet add package GM.FileStorage.Local

The interface

public interface IFileStorageService
{
    Task<FileMetadata>       UploadAsync(FileUploadRequest request, CancellationToken ct = default);
    Task<FileDownloadResult> DownloadAsync(string key, CancellationToken ct = default);
    Task<bool>               ExistsAsync(string key, CancellationToken ct = default);
    Task                     DeleteAsync(string key, CancellationToken ct = default);
    Task<Uri>                GetPresignedUrlAsync(string key, PresignedUrlRequest request, CancellationToken ct = default);
}

No provider types leak into the surface — just streams, keys and the GM types, all in GM.FileStorage.Abstractions (the key strategy is in GM.FileStorage.Keys):

• FileUploadRequest — Stream Content, FileName, ContentType, optional Key, Visibility (Private/Public), custom Metadata, and an optional ExpectedChecksum.
• FileMetadata — Key, FileName, ContentType, Size, Checksum, Visibility, LastModifiedUtc, Metadata.
• FileDownloadResult — a disposable Stream Content + FileMetadata (streamed, not buffered).
• PresignedUrlRequest — Expiry + Operation (Read/Write).
• IFileKeyStrategy — decides the storage key when a request doesn't set one.

Quick start

using GM.FileStorage;

// Reads FileStorage, and registers every GM.FileStorage package you reference whose settings are there.
builder.Services.AddGMFileStorage(builder.Configuration);

// appsettings.json
"FileStorage": {
  "Provider": "Local",                 // swap to "S3" / "AzureBlob" once those packages are added
  "Local": { "RootPath": "App_Data/files" }  // presigned links: see "Presigned links on local disk"
}

Then inject IFileStorageService — the same code works on any backend:

using GM.FileStorage.Abstractions;

public class KycDocuments(IFileStorageService storage)
{
    public async Task<string> StoreAsync(Stream file, string fileName, string tenantId, string userId)
    {
        var meta = await storage.UploadAsync(new FileUploadRequest(file, fileName, "application/pdf")
        {
            Visibility = FileVisibility.Private,
            Metadata = new Dictionary<string, string> { ["tenantId"] = tenantId, ["userId"] = userId },
            // ExpectedChecksum = "<sha256>",  // reject if the bytes don't match end to end
        });
        return meta.Key;   // e.g. tenants/acme/users/u1/9f1c…a3.pdf with a tenant/user key strategy
    }

    public async Task<Uri> LinkAsync(string key) =>
        await storage.GetPresignedUrlAsync(key, new PresignedUrlRequest { Expiry = TimeSpan.FromMinutes(10) });
}

Config-driven provider selection

AddGMFileStorage resolves IFileStorageService to the backend named by FileStorage:Provider. Each provider package registers itself as a keyed service under its name ("Local", "S3", "AzureBlob"). Reference the providers you might use and pick between them purely in config — no code change to swap.

One call registers what's configured. AddGMFileStorage(configuration) registers each GM.FileStorage package the app references, when its settings are present:

A package you don't reference is skipped. Their own AddGM… methods still work, for code-configured options or another section; calling one as well as AddGMFileStorage does no harm, since each registers once. The overload that configures FileStorageOptions in code registers no packages: add them yourself.

Key layout: a template, or your own strategy

Without configuration, keys are date-partitioned and collision-free (2026/08/02/{guid}.pdf). To lay them out differently, set a key template. No code is needed:

"FileStorage": {
  "KeyTemplate": "{category}/{shard}/{id}{ext}"   // → documents/9f/9f1c…a3.pdf, images/4e/4e07…png
}

• Categories come from the verified type. The key strategy gets the content type after the upload rules have run (FileKeyContext.ContentType). With VerifyContentType on, a renamed executable can't land in images/, and an application/octet-stream upload is placed by its detected type.
• Upload values are cleaned. Metadata values and extensions are reduced to letters, digits, -, _ and ., with no .. and no leading dot, so they can't add folders, climb out of the storage root or break a URL.
• The template is checked at startup. An unknown token, a missing {id}, unbalanced braces, or an absolute or .. path fails at startup, not at the first upload. FileKeyTemplate.Parse(...) and FileCategories.Of(...) are public if you want them in your own code.

For anything a template can't express, implement IFileKeyStrategy:

using GM.FileStorage.Keys;

public sealed class TenantKeyStrategy : IFileKeyStrategy
{
    public string GenerateKey(FileKeyContext ctx) =>
        $"tenants/{ctx.Metadata["tenantId"]}/{FileCategories.Of(ctx.ContentType)}/{Guid.NewGuid():N}{Path.GetExtension(ctx.FileName)}";
}

builder.Services.AddSingleton<IFileKeyStrategy, TenantKeyStrategy>();

Streaming & integrity

Uploads and downloads stream through an 80 KiB buffer, so a large KYC scan or image is never fully in memory. Every upload's SHA-256 is computed in the same pass; set FileUploadRequest.ExpectedChecksum and a mismatch is rejected with ChecksumMismatchException and nothing is stored.

Upload rules: size, allowed types, real content

Set them once in FileStorage and they apply to every provider. All three are off by default.

"FileStorage": {
  "MaxFileSize": 10485760,                                   // bytes (10 MB); larger → FileTooLargeException
  "AllowedContentTypes": [ "application/pdf", "image/*" ],   // anything else → FileContentTypeNotAllowedException
  "VerifyContentType": true                                  // check the bytes, not just the claimed type
}

• VerifyContentType reads the upload's first bytes and checks them against the declared type with FileTypeDetector. It knows PDF, the common image, audio and video formats (including HEIC and MOV), ZIP-based Office documents, legacy Office, archives and executables.
  • Mismatch: an .exe declared as image/png throws FileContentTypeMismatchException.
  • Generic type: an upload declared as application/octet-stream takes the detected type.
  • No signature: text formats (plain text, CSV, JSON, SVG) can't be verified and pass as declared.
• Nothing is kept from a rejected upload.
  • The type check runs before the provider reads anything.
  • An oversize stream fails as the provider reads it: S3 and Azure spool before sending, and the Local provider deletes its partial file.
  • Request bodies that can't seek are handled: the sniffed header is replayed.
• Detection on its own: FileTypeDetector.Detect(bytes) and FileTypeDetector.Matches(type, bytes) are public.

Presigned links on local disk

S3 and Azure serve their own signed links. Local disk has no server, so your app serves Local:PublicBaseUrl and checks each request:

"Local": { "PublicBaseUrl": "https://localhost:5001/files", "SigningKey": "<32+ characters, a secret>" }

// GET {PublicBaseUrl}/{key}?expires=…&op=read&sig=…
app.MapGet("/files/{**key}", async (string key, HttpRequest request,
    LocalPresignedUrlValidator links, IFileStorageService storage) =>
{
    var q = request.Query;
    if (!links.IsValid(key, q["expires"], q["op"], q["sig"]))
        return Results.StatusCode(StatusCodes.Status403Forbidden);
    var file = await storage.DownloadAsync(key);
    return Results.Stream(file.Content, file.Metadata.ContentType);
});

• Signed with HMAC-SHA256 over the operation, key and expiry: a link can't be pointed at another file, extended, or used for another operation.
• Without SigningKey links are unsigned dev conveniences and IsValid accepts none.
• Keys keep their folders and case in the link's path, one escaped segment per folder.

Keeping files in your database (GM.FileStorage.Domain + GM.FileStorage.Persistence)

Object storage only answers "give me the file at this key". It can't list "every file for tenant acme", and provider metadata (x-amz-meta-*, blob metadata, the local .gmmeta sidecar) isn't searchable. To do that, keep each file's properties in your own database. The two packages give you the domain model and its EF Core mapping, laid out like GM.Identity; your app subclasses them, as GM.Identity.Samples does.

GM.FileStorage.Domain/
  FileStorage/                                   # bounded context
    StoredFileAggregate/
      Entities/GMStoredFile.cs                   # GMStoredFile<TStoredFile>
      Entities/GMStoredFile.Metadata.cs          # GMStoredFile<TStoredFile, TStoredFileMetadata>: plus metadata rows
      Events/GMStoredFile{Uploaded,Downloaded,Deleted,Restored,Activated,Deactivated,Hidden,Unhidden}DomainEvent.cs
    StoredFileMetadataAggregate/
      Entities/GMStoredFileMetadata.cs           # one name/value pair per row
    StorageCleanupAggregate/
      Entities/GMStorageCleanup.cs               # a storage object queued for deletion
GM.FileStorage.Persistence/
  Configuration/GMStoredFileConfiguration.cs     # generic; override Schema / Table / Configure
  Configuration/GMStoredFileMetadataConfiguration.cs
  Configuration/GMStorageCleanupConfiguration.cs
  GMFileStorageTableNames.cs                     # gm_file_storage.gm_stored_files / gm_stored_file_metadata / gm_storage_cleanups

• GMStoredFile (SoftDeletableEntity<Guid> from GM.EntityFramework) is identified by its Id, a GUID, and holds the tenant, storage key, file name, content type, size, checksum, IsPublic and upload time.
  • TenantId (required, up to 64 characters) is the tenant the file belongs to; scope every query to it.
  • SoftRemove() stamps DeletedAtUtc and RestoreAll() clears it, so retention can find files deleted long enough ago.
  • RecordDownload() raises GMStoredFileDownloadedDomainEvent: with the domain-event log, a download history.
  • RecordVerification(when, problem) keeps the last integrity check of the stored bytes (VerifiedAtUtc, IntegrityProblem, null when they matched).
  • A file's content never changes after it's created: new content is a new file.
  • StorageKey is where the bytes live (unique, up to 512 characters), e.g. a path from the key template, documents/6f/6f1e….pdf.
  • A constructor takes the id too. Choose it first and build the key on it (new FileKeyContext(...) { Id = id }), and the stored object is named after the file: one identifier, with the bytes under a readable folder path.
  • It raises a domain event for each change. On a GenericDbContext, they're written to the domain-event log in the same save.
• Metadata is optional. GMStoredFile<TStoredFile> is the file alone: add your own columns (an owner, …) on your subclass and map it with GMStoredFileConfiguration<TStoredFile>, and there's one table. GMStoredFile<TStoredFile, TStoredFileMetadata> adds free-form labels: GMStoredFileMetadata holds one pair per row (documentType = passport), unique per file and name and indexed on (name, value), so finding files by a label is an index lookup through Metadata. Use it when the labels vary from file to file; for a fixed set, columns are simpler and faster.
• GMStorageCleanup queues a storage object for deletion once DueAtUtc passes. Queue one for an upload's new key before storing its bytes (due after PendingUploadGracePeriod) and remove it in the transaction that records the file: an upload that fails after storing its bytes never leaves them behind for good. A cleanup job Claims due entries (a backoff of 1, 2, 4 … minutes, at most an hour; DueAtUtc is a concurrency token), deletes the bytes unless a stored file still points at them, and removes the entry.
• Constructors are protected. Your app's aggregates subclass the bases and expose the factories.

In your app's Domain (without metadata; with it, derive from GMStoredFile<StoredFile, StoredFileMetadata>):

public class StoredFile : GMStoredFile<StoredFile>, IAggregateRoot
{
    private StoredFile() { } // EF Core materialization

    private StoredFile(Guid id, string storageKey, string fileName, string contentType, long size, string? checksum, bool isPublic, DateTime uploadedAtUtc, string tenantId)
        : base(id, storageKey, fileName, contentType, size, checksum, isPublic, uploadedAtUtc, tenantId) { }

    public static StoredFile Create(Guid id, string storageKey, string fileName, string contentType, long size, string? checksum, bool isPublic, DateTime uploadedAtUtc, string tenantId) =>
        new(id, storageKey, fileName, contentType, size, checksum, isPublic, uploadedAtUtc, tenantId);
}
// With metadata: StoredFileMetadata : GMStoredFileMetadata<StoredFile, StoredFileMetadata>, IAggregateRoot — the same way.

public class StorageCleanup : GMStorageCleanup, IStorageCleanupFactory<StorageCleanup>, IAggregateRoot
{
    private StorageCleanup() { } // EF Core materialization

    private StorageCleanup(string storageKey, DateTime dueAtUtc) : base(storageKey, dueAtUtc) { }

    public static StorageCleanup Create(string storageKey, DateTime dueAtUtc) => new(storageKey, dueAtUtc);
}

In your app's Persistence:

public class StoredFileConfiguration : GMStoredFileConfiguration<StoredFile>
{
    protected override string Schema => "file_storage";   // optional: map without the gm_ prefix
}
// With metadata: GMStoredFileConfiguration<StoredFile, StoredFileMetadata>, plus
// StoredFileMetadataConfiguration : GMStoredFileMetadataConfiguration<StoredFile, StoredFileMetadata>.

public class StorageCleanupConfiguration : GMStorageCleanupConfiguration<StorageCleanup>;

Then write an upload command: pick the file's id, build its key with IFileKeyStrategy.GenerateKey (Id = id), and call IFileStorageService.UploadAsync with that key. It records StoredFile.Create(id, key, ...) plus one StoredFileMetadata.Create(...) per pair through your repositories and unit of work. A delete command deletes the bytes and calls SoftRemove(). A list query filters StoredFile with a specification on Metadata. GM.FileStorage.Samples does exactly this.

From 5.x: the packages are organised into folders, and namespaces follow them. Code keeps compiling once the usings are updated:

Registration (AddGMFileStorage, FileStorageOptions, AddGMFileStorageDecorator), IMalwareScanner, the encryption options and every other type keep their namespace.

From 4.x: TenantUsageAsync and TenantUsage are gone from GM.FileStorage.Catalog. For a tenant's storage use, sum and count its files yourself: files.OwnedBy(tenantId).SumAsync(f => (long?)f.Size) / .CountAsync().

From 3.x:

• Ranged downloads are gone: DownloadAsync(key, FileByteRange), FileByteRange, FileDownloadResult.Range and ContentLength (use Metadata.Size), and FileRangeNotSatisfiableException. A download is always the whole file.
• GMStoredFile gains TenantId, DeletedAtUtc, VerifiedAtUtc and IntegrityProblem, and its constructors take a required tenantId last. If your subclass declared any of them, delete those properties and pass the tenant to base(...). GMStoredFileConfiguration maps them (with indexes on TenantId, DeletedAtUtc and VerifiedAtUtc), so add a migration.
• To keep your own cleanup queue, derive it from GMStorageCleanup.

From 2.x: GMStoredFile.Key is gone; a file is its Id, its bytes at StorageKey. Constructors drop the key argument, and the uploaded and deleted events no longer carry it. Add a migration: it drops the key column and its unique index, and adds a unique index on storage_key if you didn't have one. Code that looked files up by Key looks them up by Id (or by StorageKey, which is what Key held when the two were the same).

Keeping storage in step with the records (GM.FileStorage.Catalog)

Storage and your database can't share a transaction. The catalog package holds the steps that keep them in step, so every failure leaves at worst bytes nothing points at, queued (GMStorageCleanup) for a later run to delete. It works over your aggregates and GM.EntityFramework repositories; you write the commands and schedule the runs.

// GM.FileStorage.Persistence: over your DbContext, sharing each request's context with your handlers.
services.AddGMFileStorageCatalog<ApplicationDbContext, StoredFile, StorageCleanup>();

// Or over your own unit of work and repositories (GM.FileStorage.Catalog alone):
services.AddGMFileStorageCatalog<StoredFile, StorageCleanup>(sp =>
{
    var unitOfWork = sp.GetRequiredService<IUnitOfWork>();
    return (unitOfWork, unitOfWork.StoredFileRepository, unitOfWork.StorageCleanupRepository);
});

• StoredFileCatalog<TStoredFile, TStorageCleanup> (scoped, on your unit of work):
  • TryCompleteCleanupAsync(entry) claims a queued entry, deletes its bytes and removes it; a failure leaves it queued, backing off. Call it when a request leaves bytes behind (a refused or failed upload).
  • PurgeAsync(ids) removes files for good: rows gone and keys queued in one transaction, then the bytes deleted.
• StoredFileCatalogRuns<TStoredFile, TStorageCleanup>: the batches a scheduled job runs, each item in its own scope, returning what was done and what failed (to retry):
  • CleanUpDueAsync(batchSize) deletes the bytes of due entries, dropping any whose key a file still uses.
  • PurgeDeletedAsync(deletedBefore, batchSize) purges files soft-deleted before a cutoff (retention).
  • VerifyAsync(batchSize) checks the least recently checked files with StoredFileVerifier.
• StoredFileVerifier reads a file back through IFileStorageService (so decrypted, when encryption is on) and checks it exists, has the recorded size and SHA-256, and, with IMalwareScanner registered, rescans it. It records the result (VerifiedAtUtc, IntegrityProblem) and fills in a missing checksum.
• OwnedBy(tenantId) on IQueryable<TStoredFile>: a tenant's files, deleted ones included.

Your cleanup aggregate implements IStorageCleanupFactory<T> (its Create), so the catalog can queue entries.

Scheduling the runs (GM.FileStorage.Catalog.Scheduling). One call adds the three jobs on GM.Scheduling, each guarded by its distributed lock so only one instance runs it at a time:

services.AddGMFileStorage(configuration);   // also binds the jobs' settings from FileStorage:Catalog
services.AddGMScheduling(b => b.AddFileStorageCatalogJobs<StoredFile, StorageCleanup>());

"FileStorage": {
  "Catalog": {                                   // each part optional: the defaults below apply without it
    "Cleanup":   { "BatchSize": 100 },
    "Retention": { "DeletedFileDays": 30, "BatchSize": 100 },   // 0 days keeps deleted files
    "Integrity": { "BatchSize": 20 }
  }
}

Encryption at rest (GM.FileStorage.Encryption)

Every file is encrypted before it reaches the provider, so local disk, S3 and Azure only ever hold ciphertext. Your code doesn't change:

• UploadAsync and DownloadAsync take and return plaintext.
• Sizes and checksums are the plaintext's.

builder.Services.AddGMFileStorage(builder.Configuration);   // with FileStorage:Encryption present, registers encryption too

// From secrets (GM.Secrets: appsecrets.json, SECRETS_PROVIDER, environment), never a committed file.
"FileStorage": {
  "Encryption": {
    "ActiveKeyId": "2026-11",
    "Keys": {
      "2026-11": "<base64 of 32 random bytes>",   // wraps new uploads
      "2025-06": "<retired key>"                  // still needed to read files it wrapped
    }
  }
}

Generate a key with openssl rand -base64 32, or Convert.ToBase64String(RandomNumberGenerator.GetBytes(32)).

How a file is protected (envelope encryption)

• A key per file. Each upload gets a random 256-bit key, and its content is encrypted with AES-256-GCM in 64 KiB chunks. Only one chunk is ever held in memory.
• The master key wraps the file key. The file key is stored, encrypted by the master key (AES-256-GCM), in a small header at the start of the object, together with the master key's id. The object is therefore self-contained and needs no database.
• Tampering is detected. Every chunk is authenticated, and its nonce includes the chunk's index and a last-chunk flag (the STREAM construction). An altered, reordered or truncated file throws FileDecryptionException instead of returning garbage.
• Storage learns nothing about the file. The provider is told every file is encrypted, of type application/octet-stream, with no metadata of yours. The real name, content type, checksum and metadata are sealed under the file's key (AES-256-GCM, bound to the header) and kept as one opaque value (gmenc_sealed); downloads restore them. A key you leave to the key strategy is still built from the real details, so templates keep their layout: use one without {category}, {ext} or {meta:…}, such as {shard}/{id}, if the path mustn't hint at the file either. Keep your metadata small: S3 allows 2 KB of object metadata in all.

Operating it

• Rotating the master key: add a new key, make it ActiveKeyId, and keep the old one in Keys. New uploads use the new key and old files keep decrypting. Remove an old key only once no file uses it.
• Switching encryption on for existing data: files stored before then (with no encryption marker) are served as stored. New uploads are encrypted.
• Switching it off explicitly: set FileStorage:Encryption:Enabled to false. For example, keep false in a committed appsettings.json and set true together with the keys in secrets. It's on by default, so registering encryption without keys fails as soon as storage is first used, instead of silently storing plaintext.
• Presigned URLs throw NotSupportedException: a read link would hand out ciphertext, and a write link would bypass encryption. Stream files through your API instead.
• Upload rules (MaxFileSize, VerifyContentType, …) see the plaintext, because encryption sits closest to the provider.
• Other key stores: to keep master keys in a KMS or HSM, implement IFileEncryptionKeyProvider (GM.FileStorage.Encryption.Keys).
• Keyed providers resolved directly bypass encryption, like the upload rules. Always go through IFileStorageService.

Malware scanning (GM.FileStorage.MalwareScanner)

Scan every upload with ClamAV (free, open source) as it streams into storage, switched on by configuration. Off by default: until you set Enabled, nothing is scanned and ClamAV isn't needed.

builder.Services.AddGMFileStorage(builder.Configuration);                 // with FileStorage:MalwareScanner present
builder.Services.AddHealthChecks().AddGMFileStorageMalwareScannerCheck(); // readiness: ClamAV answers

"FileStorage": {
  "MalwareScanner": {
    "Enabled": true,
    "ClamAV": { "Host": "localhost", "Port": 3310 }   // also ConnectTimeout, ScanTimeout
  }
}

Run ClamAV next to your app, for example docker run -d -p 3310:3310 clamav/clamav:1.4: it downloads its signatures on first start and keeps them current.

How uploads are scanned

• While they stream. The bytes the provider reads are sent to ClamAV at the same time, so a file is never buffered whole and scanning costs no extra pass.
• Before encryption. Decorators wrap in registration order, and AddGMFileStorage registers the scanner after encryption (register them in that order if you call their AddGM… yourself), so the scanner sees the plaintext. A scanner on the bucket itself (Defender for Storage, GuardDuty) would only see ciphertext.
• Infected: refused, nothing kept. The stored bytes are deleted and FileMalwareDetectedException (with Threat) is thrown. Answer it as 400.
• No verdict: refused (fail closed). ClamAV down, timed out, or the file over its StreamMaxLength (25 MB by default; raise it in clamd.conf for larger uploads): the bytes are deleted and MalwareScanFailedException is thrown. Answer it as 503, and put the health check on readiness.
• Presigned write URLs are refused while scanning is on: they'd bypass it.

IMalwareScanner scans anything else, such as a file already stored: await scanner.ScanAsync(stream), or BeginScanAsync() and write the bytes as they arrive. Switched off, it answers NotScanned.

To test your integration, use the EICAR test file, harmless and reported by every scanner. Keep it out of your repository and off your disk, or a local antivirus will quarantine it: build it in memory, as MalwareScannerLiveTests does.

Do you need GM.DistributedLock here? (flagged, not assumed)

Core deliberately does not depend on GM.DistributedLock. For the common operations it isn't needed: object stores are last-write-wins per key, and unique keys (the default strategy) mean concurrent uploads don't collide.

A lock is worth it for one specific case: serializing writes to the same logical key — e.g. "only one upload for kyc/{userId}/passport may be in flight," or a read-modify-write on a file. That's an application-level concern, so rather than bake it into every consumer, wrap the upload:

await using var handle = await locks.AcquireAsync($"file:{key}", TimeSpan.FromSeconds(30),
    wait: TimeSpan.FromSeconds(5), retryInterval: TimeSpan.FromMilliseconds(100));
await storage.UploadAsync(request with { Key = key });

If this pattern turns out to be pervasive, a thin optional GM.FileStorage.DistributedLock decorator (IFileStorageService → lock-per-key → inner service) could add it without touching core or any provider. Recommendation: keep it out of core; add the decorator only if the need is real.

S3 and Azure providers

Both map the same IFileStorageService onto their SDK and register a keyed backend, so an app moves from Local → S3 → AzureBlob by configuration alone — no code change.

S3 / MinIO (GM.FileStorage.S3)

builder.Services.AddGMFileStorage(builder.Configuration);   // registers S3 from FileStorage:S3

"FileStorage": {
  "Provider": "S3",
  "S3": {
    "BucketName": "kyc-docs",
    "Region": "eu-central-1",
    // MinIO / S3-compatible instead of AWS:
    "ServiceUrl": "http://localhost:9000", "ForcePathStyle": true,
    "AccessKey": "…", "SecretKey": "…"      // omit to use the default AWS credential chain
  }
}

PutObject/GetObject streaming, GetPreSignedURL for presigned read/write, object metadata (x-amz-meta-gm-* for filename/checksum/visibility), and CannedACL for Public/Private.

• Presigned links use the endpoint's scheme, so a plain-HTTP ServiceUrl (MinIO in dev) gets http:// links.

• Checksums are validated on downloads. The client AddGMS3FileStorage builds sets ResponseChecksumValidation = WHEN_REQUIRED, and downloads ask for validation; other responses aren't checked against whatever checksum an S3-compatible service happens to send.

• If you construct S3FileStorageService with your own IAmazonS3, give it the same setting:

  new AmazonS3Client(credentials, new AmazonS3Config
  {
      ServiceURL = "…",
      ResponseChecksumValidation = ResponseChecksumValidation.WHEN_REQUIRED,
  });
  

Azure Blob (GM.FileStorage.AzureBlob)

builder.Services.AddGMFileStorage(builder.Configuration);   // registers Azure Blob from FileStorage:AzureBlob

"FileStorage": {
  "Provider": "AzureBlob",
  "AzureBlob": { "ConnectionString": "…", "ContainerName": "kyc" }
}

Block-blob streaming, SAS URLs via GenerateSasUri, and blob metadata. Note: Azure public access is container-scoped, so per-blob Visibility is advisory — use the SAS URL for time-limited access.

Repository layout

GM.FileStorage/            # options, AddGMFileStorage and the package discovery
  Abstractions/            # IFileStorageService, requests/results, exceptions
  Keys/                    # key strategy and key templates
  Validation/              # upload rules: size, allowed types, content check
  Content/                 # streaming, checksums and other content plumbing
GM.FileStorage.Local/      # disk provider (streaming + SHA-256 + sidecar metadata)
GM.FileStorage.S3/         # AWS S3 / MinIO provider
GM.FileStorage.AzureBlob/  # Azure Blob Storage provider
GM.FileStorage.Encryption/ # encryption at rest: per-file AES-256-GCM keys wrapped by master keys
  Format/                  # the encrypted file format and the decrypting stream
  Keys/                    # master-key providers
GM.FileStorage.MalwareScanner/ # malware scanning of uploads with ClamAV (opt-in)
  ClamAv/                  # the ClamAV client
  Storage/                 # the scanning storage decorator
  HealthChecks/            # the readiness check
GM.FileStorage.Domain/      # stored-file domain: FileStorage bounded context, GMStoredFile + GMStoredFileMetadata
GM.FileStorage.Persistence/ # EF Core configurations + table names for the stored-file domain
GM.FileStorage.Catalog/     # cleanup, purge, retention and integrity runs over the stored-file records
GM.FileStorage.Catalog.Scheduling/ # those runs as GM.Scheduling jobs
tests/GM.FileStorage.Tests/  # xUnit tests, by package: Core, Providers, Encryption, MalwareScanner, Domain, Persistence, Catalog

Building & testing

dotnet build -c Release
dotnet test  -c Release

Releasing

Versioning is automated from Conventional Commits — see CONTRIBUTING.md. All packages share one version (Directory.Build.props) and publish together to nuget.org on each release.

License

MIT — see LICENSE.