Letmein

What is it?

Letmein is an encrypted notes service, similar to cryptobin.co. No encryption keys are stored in the database, and the encryption is performed in the browser. Notes last up to 12 hours by default, but this is configurable (see below) with the option to have multiple expiry times. A background service (using Quartz.NET) cleans up expired notes on a configurable schedule.

Tech stack

• .NET 10
• React using Vite and Tailwind
• Sjcl Javascript library for encryption.
• Postgres (using Marten)
• Cloud storage (S3, Azure, Google) (using CloudFileStore)

Quick start

Letmein now supports 3 ways to store your pastes: local storage, cloud file store and database. It listens on port 8080 by default.

Step 1. Configure a storage provider

Local storage

Pastes can be stored inside the storage directory inside the container, the full path is /app/storage. If you want to persist the pastes, simply map this as a volume.

You don't need to customise any environmental variables for this, it will launch using FileSystem by default, as the storage provider.

S3

Add the following to your environmental variables

REPOSITORY_TYPE=S3
S3__AccessKey=key
S3__BucketName=bucket
S3__Region=for example, eu-west-1
S3__SecretKey=secret

Google Cloud Storage

Add the following to your environmental variables

REPOSITORY_TYPE=GoogleCloud
GoogleCloud__BucketName=name of your bucket
GoogleCloud__type=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__project_id=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__private_key_id=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__private_key=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__client_email=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__client_id=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__auth_uri=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__token_uri=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__auth_provider_x509_cert_url=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>
GoogleCloud__client_x509_cert_url=<COPY FROM YOUR SERVICE ACCOUNT JSON FILE>

Azure Blobs

Add the following to your environmental variables

REPOSITORY_TYPE=AzureBlobs
Azure__ContainerName=container name
Azure__ConnectionString=get this from the Azure portal

Postgres

If you don't want to buy Postgres hosting (such as AWS RDS), you can run Postgres as a Docker container. The example below assumes the Postgres container is inside the same Docker network as your Letmein Docker container.

Start a Postgres container (it needs 9.5 or higher):

docker run -d --name postgres -p 5432:5432 -e POSTGRES_USER=letmein -e POSTGRES_PASSWORD=letmein123 postgres

Create a Docker network so containers can communicate:

docker network create letmein

Step 2. Run the Letmein Docker container

Run the Letmein Docker container (below assumes you're using Postgres):

docker run -d -p 8080:8080 --network letmein -e POSTGRES_CONNECTIONSTRING="host=postgres;database=letmein;password=letmein123;username=letmein" ghcr.io/yetanotherchris/letmein:latest

Now go to http://localhost:8080 and store some text.

Customisations

The letmein image is fairly customisable. The various customisations can be done via environmental variables passed to the Docker container, which are uppercase by convention (except the cloud storage environmental variables above):

• REPOSITORY_TYPE - Where pastes are stored. Possible values: "FileSystem", "Postgres", "S3", "GoogleCloud", "AzureBlobs". Default is FileSystem.
• POSTGRES_CONNECTIONSTRING - The connection string to the Postgres database.
• EXPIRY_TIMES - A comma-separated list of minutes that pastes expire after. For example "90, 600" would be 1 hour 30 minutes, and 10 hours. The default is 720 minutes (12 hours)
• CLEANUP_SCHEDULE - Controls how often expired pastes are cleaned up. Accepts a TimeSpan (e.g. "00:30:00" for 30 minutes) or a cron expression (e.g. "*/5 * * * *" for every 5 minutes). The default is 30 minutes.
• ID_TYPE - Short url ID type. Possible values:
  • default (bips39-two-words)
  • bips39-two-words
  • bips39-two-words-and-number
  • pronounceable
  • short-pronounceable
  • random-with-pronounceable
  • short-mixedcase
  • shortcode.

As letmein doesn't check if a note id already exists, it's worth knowing the clash rate is about 1 in 4 million for bips39-two-words. It's 1 in 40 billion for bips39-two-words-and-number. See the UniqueIdGenerator.cs class for notes on clash rates.