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https://github.com/grapheneos/attestationserver

attestation.app remote attestation server. Server code for use with the Auditor app: https://github.com/GrapheneOS/Auditor. It provides two services: submission of attestation data samples and a remote attestation implementation with email alerts to go along with the local implementation based on QR code scanning in the app.
https://github.com/grapheneos/attestationserver

android attestation authenticity cryptography grapheneos hsm integrity monitoring remote-attestation secure-boot secureboot security strongbox verifiedboot

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attestation.app remote attestation server. Server code for use with the Auditor app: https://github.com/GrapheneOS/Auditor. It provides two services: submission of attestation data samples and a remote attestation implementation with email alerts to go along with the local implementation based on QR code scanning in the app.

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README 

        
See the overview of the project at https://attestation.app/about.



## Installation guide



This is a generic guide on setting up the attestation server.



Sync submodules for sqlite4java prebuilt in libs/.



You need to set up nginx using the nginx configuration in the nginx directory in this repository.

You'll need to adjust it based on your domain name. The sample configuration relies on certbot,

[nginx-rotate-session-ticket-keys](https://github.com/GrapheneOS/nginx-rotate-session-ticket-keys),

and [certbot-ocsp-fetcher](https://github.com/tomwassenberg/certbot-ocsp-fetcher). Setting up the web server is out-of-scope for this guide.



The deploy and process scripts on the development machine require the following dependencies to be installed:



    rsync, zopfli, parallel, yajl, brotli, nginx-mod-brotli, python3, python-pip, nodejs, npm, libxml2



`validatornu` must be obtained manually

[here](https://github.com/validator/validator/releases/tag/20.6.30) (vnu.linux.zip). Unzip it in

the same directory in AttestationServer and change the binary path in `process-static` from

`validatornu` to `vnu-runtime-image/bin/vnu` using sed: `sed -i

's+validatornu+vnu-runtime-image/bin/vnu+g' process-static`



Install a headless Java 18 runtime environment. The package name on Debian-based distributions is

`openjdk-18-jre-headless` or `jre-openjdk-headless` on Arch Linux. Install `sqlite3` in order to

set up the email configuration for the database.



As root, on the server:



    useradd -m -s /bin/bash -b /var/lib attestation



    mkdir -p /opt/attestation/deploy_{a,b}

    ln -s /opt/attestation/deploy_a /opt/attestation/deploy



    mkdir -p /srv/attestation.app_{a,b}

    ln -s /srv/attestation.app_a /srv/attestation.app



Set up ssh `authorized_keys` for the attestation user.



Copy `attestation.service` to `/etc/systemd/system/attestation.service`.



On your development machine, you will need to change the `remote` variable in the deploy scripts

to your server. You'll also need to change the

[DOMAIN](https://github.com/GrapheneOS/AttestationServer/blob/df53e39706fdc6247ce497cb0776bf77fe931085/src/main/java/app/attestation/server/AttestationServer.java#L85)

in AttestationServer.java to your server and the [app signing

key](https://github.com/GrapheneOS/AttestationServer/blob/df53e39706fdc6247ce497cb0776bf77fe931085/src/main/java/app/attestation/server/AttestationProtocol.java#L157-L162)

and [app

ID](https://github.com/GrapheneOS/AttestationServer/blob/df53e39706fdc6247ce497cb0776bf77fe931085/src/main/java/app/attestation/server/AttestationProtocol.java#L154-L156).

Then deploy the attestation server and static content:



    npm i

    python -m venv venv

    source venv/bin/activate

    pip install -r requirements.txt

    ./deploy-server

    ./deploy-static



As root on the server, enable and start the attestation server:



    systemctl enable attestation

    systemctl start attestation



The server will be listening on `[::1]:8080` by default which [can be changed](https://github.com/GrapheneOS/AttestationServer/blob/df53e39706fdc6247ce497cb0776bf77fe931085/src/main/java/app/attestation/server/AttestationServer.java#L320).



## Email alert configuration



In order to send email alerts, AttestationServer needs to be configured with valid credentials for

an SMTP server. The configuration is stored in the `Configuration` table in the database and can

be safely modified while the server is running to have it kick in for the next email alert cycle.



Only SMTPS (SMTP over TLS) with a valid certificate is supported for remote email servers.

STARTTLS is deliberately not supported because it's less secure unless encrypted is enforced, in

which case it makes more sense to use SMTPS anyway. The username must also be the full address for

sending emails.



For example, making an initial configuration:



    sqlite3 attestation.db "INSERT INTO Configuration VALUES ('emailUsername', '[email protected]'), ('emailPassword', ''), ('emailHost', 'mail.grapheneos.org'), ('emailPort', '465')"



The `attestation.service` unit only allows the service to communicate over `localhost` by default

so the `IPAddressDeny`/`IPAddressAllow` configuration either needs to be removed or extended to

include your DNS server and mail server IP addresses when using a remote mail server.



### Handling abuse



The `emailBlacklistPatterns` array in

[`src/main/java/app/attestation/server/AttestationServer.java`](https://github.com/GrapheneOS/AttestationServer/blob/df53e39706fdc6247ce497cb0776bf77fe931085/src/main/java/app/attestation/server/AttestationServer.java#L92-L94) can be used to blacklist email

addresses using regular expressions. We plan to move this to a table in the database so that it

can be configured dynamically without modifying the sources, rebuilding and redeploying. For now,

this was added to quickly provide a way to counter abuse.



## API for the Auditor app



### QR code



The scanned QR code contains space-separated values in plain-text: ` 

 `. The `subscribeKey` should be treated as an opaque string rather

than assuming base64 encoding. Additional fields may be added in the future.



### /auditor/challenge



* Request method: POST

* Request headers: n/a

* Request body: n/a

* Response body:



Returns a standard challenge message in the same format as the Auditor app QR code. The challenge

can only be used once and expires in 1 minute.



The server challenge index is always zeroed out and the userId should be used instead.



### /auditor/verify



* Request method: POST

* Request headers:



The `Authorization` header needs to be set to `Auditor  ` for an unpaired

attestation. That will also work for a paired attestation if the subscribeKey matches, but it

should be set to `Auditor ` to allow for subscribeKey rotation.



* Request body:



Standard attestation message in the same format as the Auditor app QR code.



* Response body:



Returns JSON with a `verifyInterval` field.



## Logging



Logs are written via stderr for journald. Log guidelines:



emerg: filesystem or database corruption

alert: service fully not functioning

crit: service partially not functioning

error: service side error for a specific request

warning: login failures, unexpected errors triggered by clients and missing setup for full functionality such as sending alerts

info: security-relevant events such as logins, expected errors triggered by clients and status logging

debug: not used in production