camo-proxy

Standalone and Cloudflare-worker microservice for proxying cryptographically signed URLs. This helps protect users' privacy with untrusted embeds. Camo Proxy

This server accepts requests in the form of GET /camo/:base64_url/:base64_signature and proxies the request to the given URL. The signature is generated using an HMAC-SHA1 hash of the URL and a secret key. Both the URL and signature are base64 encoded with the URL_SAFE_NO_PAD base64 encoding scheme.

The server is designed to be used as a privacy and security layer for image requests, as it removes cookies and other sensitive information from the request and response headers.

Example path generation:

use base64::engine::{general_purpose::URL_SAFE_NO_PAD, Engine};

use hmac::{digest::Key, Mac};
pub type Hmac = hmac::SimpleHmac<sha1::Sha1>;

let key = "59d273a2641327d005b255bb7dc89a9f";
let url = "https://raw.githubusercontent.com/Lantern-chat/server/master/Cargo.toml";

let mut decoded_key = Key::<Hmac>::default();
// keys are allowed to be shorter than the entire raw key. Will be padded internally.
hex::decode_to_slice(key, &mut decoded_key[..key.len() / 2]).unwrap();

let signature = URL_SAFE_NO_PAD.encode(Hmac::new(&decoded_key).chain_update(url).finalize().into_bytes());
let path = format!("/camo/{}/{}", URL_SAFE_NO_PAD.encode(url), signature);
assert_eq!(path, "/camo/aHR0cHM6Ly9yYXcuZ2l0aHVidXNlcmNvbnRlbnQuY29tL0xhbnRlcm4tY2hhdC9zZXJ2ZXIvbWFzdGVyL0NhcmdvLnRvbWw/JvEspwk6jNaE6SpGG2r861A6reM");

Run your camo proxy instance somewhere and request https://camo.mysite.com/camo/aHR0cHM6Ly9yYXcuZ2l0aHVidXNlcmNvbnRlbnQuY29tL0xhbnRlcm4tY2hhdC9zZXJ2ZXIvbWFzdGVyL0NhcmdvLnRvbWw/JvEspwk6jNaE6SpGG2r861A6reM

Shared Configuration (CF Worker and Standalone)

CAMO_SIGNING_KEY

128-bit signing key encoded as a hexidecimal string.

Standalone Configuration

CAMO_BIND_ADDRESS

Sets the bind address for this microservice.

Example .env:

CAMO_SIGNING_KEY = "59d273a2641327d005b255bb7dc89a9f" # Example key
CAMO_BIND_ADDRESS = "127.0.0.1:8765"