🌐 HTTP(S) proxies
- /examples/http_connect_proxy.rs: Spawns a minimal http proxy which accepts http/1.1 and h2 connections alike, and proxies them to the target host.
- /examples/https_connect_proxy.rs: Spawns a minimal https connect proxy which accepts http/1.1 and h2 connections alike, and proxies them to the target host through a TLS tunnel.
Description
You'll notice that the above graph is the exact same one used in the Reverse Proxies chapter. In an abstract topology sense this is expected, however there are typically differences:
- The client, proxy and server are typically in 3 different intranets, with communication going typically over the intranet;
- The use cases of a reverse proxy are very wide, while those of the http proxy are pretty specific.
The most common use case of an http(s) proxy is to conceal the MAC (~L3) and IP address (~L4) of the client, and have the request originate instead from the http(s) proxy.
HTTP Proxy relaying HTTPS requests
------------------------------------
┌────────┐ ┌──────────────┐ ┌────────────────────┐
│ Client │──────▶│ HTTP Proxy │──────▶│ Target Server (TLS)│
└────────┘ └──────────────┘ └────────────────────┘
│ │ │
│ 1. TCP connect to proxy (e.g., :3128) │
│────────────────▶│ │
│ │ │
│ 2. Send HTTP CONNECT request │
│ e.g., │
│ CONNECT example.com:443 HTTP/1.1 │
│ Host: example.com:443 │
│────────────────▶│ │
│ │ │
│ 3. Proxy establishes TCP to server │
│ │───────────────────────▶│
│ │ │
│ 4. Proxy replies with 200 OK │
│◀────────────────│ │
│ │ │
│ 5. TLS handshake begins (client ↔ server)│
│◀────────────────────────────────────────▶│
│ │ │
│ 6. Encrypted HTTP(S) traffic relayed │
│◀────────────────────────────────────────▶│
Flow of a regular "HTTP CONNECT" proxy.
In case the client request is encrypted (TLS) it will typically make a plaintext (http/1.1) request with the "CONNECT" method to the proxy, whom on the behalve of the client will establish an encrypted tunnel to the target (server), from there it will:
- either just copy the data between the two connections as they are;
- or it might act as a MITM proxy and actually read and possibly even modify the incoming (http) request prior to sending it to the target client. In this case it might even act as a distortion proxy.
In case we are dealing with TLS-encrypted traffic it does mean that the client most likely will have to accept/approve the authority of the proxy's TLS certification, given it will not match the expected target (server) TLS certificate. Depending on the client's network policies this might be handled automatically due to the use of a non-public root certificate.
HTTP Proxy relaying HTTP requests
-----------------------------------
┌────────┐ ┌────────────────┐ ┌────────────────────┐
│ Client │──────▶│ HTTP Proxy │──────▶│ Target HTTP Server │
└────────┘ └────────────────┘ └────────────────────┘
│ │ │
│ 1. TCP connect to proxy (:3128) │
│─────────────────▶│ │
│ │ │
│ 2. Send full HTTP request via proxy │
│ e.g., │
│ GET http://example.com HTTP/1.1 │
│ Host: example.com │
│─────────────────▶│ │
│ │ │
│ 3. Proxy parses and forwards request │
│ │──────────────────────▶ │
│ │ │
│ 4. Target server replies with HTTP │
│ │◀────────────────────── │
│ │ │
│ 5. Proxy may log, modify, or inject │
│ │ │
│ 6. Proxy sends HTTP response to client │
│◀─────────────────│ │
│ │ │
│ 7. Subsequent requests/responses relayed │
│◀─────────────────▶│◀─────────────────────▶│
Plain text (http) requests are typically immediately made with the Host/Authorization headers being equal to the desired target server. Which once again looks a lot more like logic that a reverse proxy would also do among one of its many tasks. As such HTTP traffic can always be logged, modified or injected by any intermediate party, including your HTTP proxy.
See the official RFCs for more information regarding HTTP semantics and protocol specifications.
HTTP Proxy MITM'ing HTTPS requests
------------------------------------
┌────────┐ ┌────────────────────┐ ┌────────────────────┐
│ Client │──────▶│ HTTP Proxy (MITM) │──────▶│ Target Server (TLS)│
└────────┘ └────────────────────┘ └────────────────────┘
│ │ │
│ 1. TCP connect │ │
│ to proxy (:3128)│ │
│───────────────────▶│ │
│ │ │
│ 2. Send CONNECT │ │
│ example.com:443 │ │
│───────────────────▶│ │
│ │ │
│ │ 3. Proxy replies │
│ ◀───────────────── │ with 200 OK │
│ │ │
│ │ 4. TLS handshake │
│◀─────────────────▶ │ with proxy │
│ │ (fake cert) │
│ │ │
│ 5. Proxy connects │ │
│ to target:443 │─────────────────────────▶│
│ 6. Proxy performs │ │
│ TLS to server │─────────────────────────▶│
│ │ │
│ │
│ 7. Encrypted HTTPS │
│ relayed via MITM │
│ │
│◀──────────────────▶│◀────────────────────────▶│
Flow a MITM proxy handling HTTPS traffic
step (4) to (6) can be done before step (3). However rrama by default does these
proxy ↔ serversteps lazilly only when the first actual http(s) request is received.