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Overview

The createAtlsFetch function creates a fetch-compatible API for making HTTP requests over attested TLS connections. It handles the full HTTP protocol in Rust/WASM, providing a familiar interface for browser applications. This is the recommended high-level API for most browser use cases.

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Function signature

async function createAtlsFetch(options: AtlsFetchOptions): Promise<AtlsFetch>

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Parameters

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options
object
required
Configuration for the attested fetch connection
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proxyUrl
string
required
WebSocket proxy URL for TCP tunneling. Required because browsers cannot make raw TCP connections.Example: "ws://127.0.0.1:9000"
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targetHost
string
required
The TEE server hostname to connect to.Example: "vllm.example.com"
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policy
Policy
required
Attestation verification policy that determines what TEE evidence is accepted.See Policy configuration for details.
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onAttestation
function
default:"undefined"
Optional callback invoked after attestation verification completes.Receives an AttestationSummary object with:
  • trusted (boolean): Verification result
  • teeType (string): TEE type (e.g., “Tdx”)
  • tcbStatus (string): TCB status from Intel
  • advisoryIds (string[]): Security advisories

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Return value

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fetch
function
A fetch-compatible function for making HTTP requests over the attested TLS connection.The returned function has the same signature as the standard fetch API:
(url: string, init?: RequestInit) => Promise<Response>
The Response object includes an additional attestation property with the verification result.

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Proxy configuration

Browser deployments require a WebSocket-to-TCP proxy since browsers cannot make raw TCP connections. The proxy forwards bytes without TLS termination - all encryption and attestation verification happens in the browser.

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Running the proxy

# Set allowlist for security (prevents SSRF attacks)
export ATLS_PROXY_ALLOWLIST="vllm.example.com:443,other.tee.com:443"
export ATLS_PROXY_LISTEN="127.0.0.1:9000"

cargo run -p atlas-proxy

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Security considerations

  • The proxy only forwards bytes and never terminates TLS
  • Attestation verification occurs entirely in the browser
  • An allowlist is required to prevent SSRF attacks
  • The proxy can be deployed alongside your web application

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Examples

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Basic usage

import { init, createAtlsFetch } from "@concrete-security/atlas-wasm";

await init();

const fetch = createAtlsFetch({
  proxyUrl: "ws://127.0.0.1:9000",
  targetHost: "vllm.example.com",
  policy: { type: "dstack_tdx" },
  onAttestation: (att) => console.log("TEE:", att.teeType)
});

const response = await fetch("/v1/chat/completions", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ model: "gpt", messages: [...] })
});

console.log(response.status);
console.log(response.attestation); // { trusted: true, teeType: "Tdx", ... }

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With policy configuration

const fetch = createAtlsFetch({
  proxyUrl: "ws://127.0.0.1:9000",
  targetHost: "vllm.example.com",
  policy: {
    type: "dstack_tdx",
    allowed_tcb_status: ["UpToDate", "SWHardeningNeeded"],
    expected_bootchain: {
      mrtd: "b24d3b24...",
      rtmr0: "24c15e08...",
      rtmr1: "6e1afb74...",
      rtmr2: "89e73ced..."
    }
  }
});

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Streaming responses

const response = await fetch("/v1/chat/completions", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ 
    model: "gpt", 
    messages: [...],
    stream: true 
  })
});

// Response body is a ReadableStream
const reader = response.body.getReader();
while (true) {
  const { done, value } = await reader.read();
  if (done) break;
  console.log(new TextDecoder().decode(value));
}

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