# Enforce private-file authorization for Gin

## Summary

Private file access for a Gin app on Ample. Verified on Gin: a role-to-document access model with negative tests (401, 403) and an authorized private-bucket round-trip (private=ok). Build and start: `CGO_ENABLED=0 go build -o app ./...` then `./app` on the `ubuntu-24.04` template (go.sum committed for a reproducible build).

## Infrastructure requirements

- Compute: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
- Postgres: verified (Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.)
- S3-compatible object storage: verified (Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary. Other S3 operations are not verified.)

## Prerequisites

- A Gin project (CGO_ENABLED=0 go build -o app ./... then ./app on the ubuntu-24.04 template (go.sum committed for a reproducible build))
- A PostgreSQL driver reading DATABASE_URL at runtime
- A bucket from `ample bucket create` with credentials passed as encrypted S3_* environment variables
- An Ample account token with servers:write, databases:read, buckets:read

## Exact tested configuration

- template: `ubuntu-24.04`
- runtime: `go`
- size: `s-1vcpu-1gb`
- build: `CGO_ENABLED=0 go build -o app ./...`
- start: `./app`

## Steps

1. **Build and start.** `CGO_ENABLED=0 go build -o app ./...` then `./app` on the ubuntu-24.04 template (go.sum committed for a reproducible build); the server must bind 0.0.0.0 on PORT.
2. **Create the bucket and pass its credentials.** Create it once with `ample bucket create`, then pass endpoint, region, bucket and keys with --env; use path-style addressing.

```
   ample deploy . --name <app-name> --public --env S3_ENDPOINT=... --env S3_REGION=... --env S3_BUCKET=... --env S3_ACCESS_KEY_ID=... --env S3_SECRET_ACCESS_KEY=...
   ```
3. **Authorize before touching storage.** Return 401 for unauthenticated requests and 403 for the wrong role; keep the bucket unpublished and stream objects through the app.
4. **Verify.** Fetch the live URL and /p/private-document-library on the example; on failure read the build and runtime logs.

```
   ample logs <deployment_id> --kind build
   ```

## Tested examples

- **Gin pattern fixture** (tests/deploy-canaries/gin-patterns): Verified private file access on Gin.

## Success checks

- app responds on its public URL (`/` on the live URL, expect ample canary gin patterns)
- private-document-library check from the example (`/p/private-document-library` on the live URL, expect see the pattern fixture checks)

## Limitations

- Verified on the ubuntu-24.04 template at s-1vcpu-1gb; other sizes and Gin major versions are not verified.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.
- PutObject and GetObject with path-style addressing are verified; other S3 operations are not verified.

## Cost estimate

Estimated 10.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).
- app server x1 `s-1vcpu-1gb`: 5.00 USD
- managed PostgreSQL database x1 `s-1vcpu-1gb`: 5.00 USD

Always-on monthly price of the tested sizes; apps auto-pause when idle. Buckets are allocation-priced per quota and not included.

## Verification evidence

- canary_run on 2026-09-21T01:15:54Z at revision `50dbac567d2c5cc8e55e6c748a646be0025d9cfb-dirty (CLI 0.1.21)`: Gin pattern fixture deployed on Ample (CGO_ENABLED=0 go build -o app ./... then ./app on the ubuntu-24.04 template (go.sum committed for a reproducible build)); for this guide: a role-to-document access model with negative tests (401, 403) and an authorized private-bucket round-trip (private=ok). (expires 2027-03-20T01:15:54Z)

Last verified: 2026-09-21T01:15:54Z

## Execution binding

MCP tool `ample_deploy` (registry `mcp:ample_deploy`), schema hash `876465fce906da0c` observed 2026-09-21T03:19:59.461917+00:00 at revision `49962bcade4f`, binding state `current`, required scopes: servers:write, databases:read, buckets:read.