# Object Storange And Data Encryption

## Object Storage

By default, demarches-simplifiees.fr uses an [OVH Object Storage](https://www.ovhcloud.com/en/public-cloud/object-storage/) backend. The hard-drives are encrypted at rest, but to protect user files even better, demarches-simplifiees.fr can also use an external encryption proxy, that will encrypt and decrypt files on the fly:

* Encryption is done via our [proxy](https://github.com/betagouv/ds_proxy) when the file is uploaded by a client.
* Decryption is done via the same proxy when the file is downloaded to a client

### Object Storage limitation

As an s3 compatible object storage backend, OVH Object Storage suffers the same limitations.

One of them being that when you upload a file bigger than 5Go, it must be chunked into segments (see the [documentation](https://docs.ovh.com/fr/storage/pcs/capabilities-and-limitations/#max_file_size-5368709122-5gb)).

This process to chunks the file in segment, then re-arrange it via a manifest. Unfortunately encryption can't work with this usecase.

So we are using a custom script that wraps two call to our proxy in order to buffer all the chunks, encrypt/decrypt the whole. Here is an example

```
#!/usr/bin/env bash
# wrapper script to encrypt and upload file received from archive

set -o errexit
set -o pipefail
set -o nounset

# params
# 1: filename
# 2: key
if ! [ "$#" -eq 2 ]; then
    echo "usage: $0 <filename> <key>"
    exit 1
fi
local_file_path=$1
remote_basename=$(basename $local_file_path)
key=$2

# encrypt
curl -s -XPUT http://ds_proxy_host:ds_proxy_port/local/encrypt/${remote_basename} --data-binary @${local_file_path}

# get back encrypted file
encrypted_filename="${local_file_path}.enc"
curl -s http://ds_proxy_host:ds_proxy_port/local/encrypt/${remote_basename} -o ${encrypted_filename}

# OVH openstack params
os_tenant_name=os_tenant_name
os_username=os_username
os_password=os_password
os_region_name=GRA

# auth = https://auth.cloud.ovh.net/v3/
# use haproxy proxy and not direct internet URL
os_auth_url="os_auth_url"
os_storage_url="os_storage_url" \
container_name=container_name

expiring_delay="$((60 * 60 * 24 * 4))" # 4 days

# upload
/usr/local/bin/swift \
  --auth-version 3 \
  --os-auth-url "$os_auth_url" \
  --os-storage-url "$os_storage_url" \
  --os-region-name "$os_region_name" \
  --os-tenant-name "$os_tenant_name" \
  --os-username "$os_username" \
  --os-password "$os_password" \
  upload \
  --header "X-Delete-After: ${expiring_delay}" \
  --segment-size "$((3 * 1024 * 1024 * 1024))" \
  --header "Content-Disposition: filename=${remote_basename}" \
  --object-name "${key}" \
  "${container_name}" "${encrypted_filename}"

swift_exit_code=$?

# cleanup
rm ${encrypted_filename}

# return swift return code
exit ${swift_exit_code}
```