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305//! GitHub Copilot authentication — exchanges a GitHub PAT for a Copilot API token.
//!
//! The Copilot API uses the OpenAI chat completions format, so this module
//! handles token exchange and caching, then delegates to the OpenAI-compatible driver.
use std::sync::Mutex;
use std::time::{Duration, Instant};
use tracing::{debug, warn};
use zeroize::Zeroizing;
/// Copilot token exchange endpoint.
const COPILOT_TOKEN_URL: &str = "https://api.github.com/copilot_internal/v2/token";
/// Token exchange timeout.
const TOKEN_EXCHANGE_TIMEOUT: Duration = Duration::from_secs(10);
/// Refresh buffer — refresh token this many seconds before expiry.
const REFRESH_BUFFER_SECS: u64 = 300; // 5 minutes
/// Default Copilot API base URL.
pub const GITHUB_COPILOT_BASE_URL: &str = "https://api.githubcopilot.com";
/// Cached Copilot API token with expiry and derived base URL.
#[derive(Clone)]
pub struct CachedToken {
/// The Copilot API token (zeroized on drop).
pub token: Zeroizing<String>,
/// When this token expires.
pub expires_at: Instant,
/// Base URL derived from proxy-ep in the token (or default).
pub base_url: String,
}
impl CachedToken {
/// Check if the token is still valid (with refresh buffer).
pub fn is_valid(&self) -> bool {
self.expires_at > Instant::now() + Duration::from_secs(REFRESH_BUFFER_SECS)
}
}
/// Thread-safe token cache for a single Copilot session.
pub struct CopilotTokenCache {
cached: Mutex<Option<CachedToken>>,
}
impl CopilotTokenCache {
pub fn new() -> Self {
Self {
cached: Mutex::new(None),
}
}
/// Get a valid cached token, or None if expired/missing.
pub fn get(&self) -> Option<CachedToken> {
let lock = self.cached.lock().unwrap_or_else(|e| e.into_inner());
lock.as_ref().filter(|t| t.is_valid()).cloned()
}
/// Store a new token in the cache.
pub fn set(&self, token: CachedToken) {
let mut lock = self.cached.lock().unwrap_or_else(|e| e.into_inner());
*lock = Some(token);
}
}
impl Default for CopilotTokenCache {
fn default() -> Self {
Self::new()
}
}
/// Exchange a GitHub PAT for a Copilot API token.
///
/// POST https://api.github.com/copilot_internal/v2/token
/// Authorization: Bearer {github_token}
///
/// Response: {"token": "tid=...;exp=...;sku=...;proxy-ep=...", "expires_at": unix_timestamp}
pub async fn exchange_copilot_token(github_token: &str) -> Result<CachedToken, String> {
let client = reqwest::Client::builder()
.timeout(TOKEN_EXCHANGE_TIMEOUT)
.build()
.map_err(|e| format!("Failed to build HTTP client: {e}"))?;
debug!("Exchanging GitHub token for Copilot API token");
let resp = client
.get(COPILOT_TOKEN_URL)
.header("Authorization", format!("token {github_token}"))
.header("Accept", "application/json")
.header("User-Agent", "OpenFang/1.0")
.send()
.await
.map_err(|e| format!("Copilot token exchange failed: {e}"))?;
if !resp.status().is_success() {
let status = resp.status();
let body = resp.text().await.unwrap_or_default();
return Err(format!("Copilot token exchange returned {status}: {body}"));
}
let body: serde_json::Value = resp
.json()
.await
.map_err(|e| format!("Failed to parse Copilot token response: {e}"))?;
let raw_token = body
.get("token")
.and_then(|v| v.as_str())
.ok_or("Missing 'token' field in Copilot response")?;
let expires_at_unix = body.get("expires_at").and_then(|v| v.as_i64()).unwrap_or(0);
// Calculate Duration from now until expiry
let now_unix = std::time::SystemTime::now()
.duration_since(std::time::UNIX_EPOCH)
.unwrap_or_default()
.as_secs() as i64;
let ttl_secs = (expires_at_unix - now_unix).max(60) as u64;
let (_, proxy_ep) = parse_copilot_token(raw_token);
let base_url = proxy_ep.unwrap_or_else(|| GITHUB_COPILOT_BASE_URL.to_string());
// SECURITY: Validate HTTPS on the base URL
if !base_url.starts_with("https://") {
warn!(url = %base_url, "Copilot proxy-ep is not HTTPS, using default");
return Ok(CachedToken {
token: Zeroizing::new(raw_token.to_string()),
expires_at: Instant::now() + Duration::from_secs(ttl_secs),
base_url: GITHUB_COPILOT_BASE_URL.to_string(),
});
}
Ok(CachedToken {
token: Zeroizing::new(raw_token.to_string()),
expires_at: Instant::now() + Duration::from_secs(ttl_secs),
base_url,
})
}
/// Parse the semicolon-delimited Copilot token to extract proxy endpoint.
///
/// Token format: `tid=...;exp=...;sku=...;proxy-ep=https://...;...`
/// Returns (cleaned_token, Option<proxy_ep_url>).
pub fn parse_copilot_token(raw: &str) -> (String, Option<String>) {
let mut proxy_ep = None;
for segment in raw.split(';') {
let segment = segment.trim();
if let Some(url) = segment.strip_prefix("proxy-ep=") {
proxy_ep = Some(url.to_string());
}
}
(raw.to_string(), proxy_ep)
}
/// Check if GitHub Copilot auth is available (GITHUB_TOKEN env var is set).
pub fn copilot_auth_available() -> bool {
std::env::var("GITHUB_TOKEN").is_ok()
}
/// LLM driver that wraps OpenAI-compatible with Copilot token exchange.
///
/// On each API call, ensures a valid Copilot API token is available
/// (exchanging the GitHub PAT if needed), then delegates to an OpenAI-compatible driver.
pub struct CopilotDriver {
github_token: Zeroizing<String>,
token_cache: CopilotTokenCache,
}
impl CopilotDriver {
pub fn new(github_token: String, _base_url: String) -> Self {
Self {
github_token: Zeroizing::new(github_token),
token_cache: CopilotTokenCache::new(),
}
}
/// Get a valid Copilot API token, exchanging if needed.
async fn ensure_token(&self) -> Result<CachedToken, crate::llm_driver::LlmError> {
// Check cache first
if let Some(cached) = self.token_cache.get() {
return Ok(cached);
}
// Exchange GitHub PAT for Copilot token
debug!("Copilot token expired or missing, exchanging...");
let token = exchange_copilot_token(&self.github_token)
.await
.map_err(|e| crate::llm_driver::LlmError::Api {
status: 401,
message: format!("Copilot token exchange failed: {e}"),
})?;
self.token_cache.set(token.clone());
Ok(token)
}
/// Create a fresh OpenAI driver with the current Copilot token.
fn make_inner_driver(&self, token: &CachedToken) -> super::openai::OpenAIDriver {
// Use proxy-ep from token if available, otherwise fall back to default base URL.
let base_url = if token.base_url.is_empty() {
GITHUB_COPILOT_BASE_URL.to_string()
} else {
token.base_url.clone()
};
super::openai::OpenAIDriver::new(token.token.to_string(), base_url)
}
}
#[async_trait::async_trait]
impl crate::llm_driver::LlmDriver for CopilotDriver {
async fn complete(
&self,
request: crate::llm_driver::CompletionRequest,
) -> Result<crate::llm_driver::CompletionResponse, crate::llm_driver::LlmError> {
let token = self.ensure_token().await?;
let driver = self.make_inner_driver(&token);
driver.complete(request).await
}
async fn stream(
&self,
request: crate::llm_driver::CompletionRequest,
tx: tokio::sync::mpsc::Sender<crate::llm_driver::StreamEvent>,
) -> Result<crate::llm_driver::CompletionResponse, crate::llm_driver::LlmError> {
let token = self.ensure_token().await?;
let driver = self.make_inner_driver(&token);
driver.stream(request, tx).await
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_parse_copilot_token_with_proxy() {
let raw = "tid=abc123;exp=1700000000;sku=copilot_for_individual;proxy-ep=https://copilot-proxy.example.com";
let (token, proxy) = parse_copilot_token(raw);
assert_eq!(token, raw);
assert_eq!(proxy, Some("https://copilot-proxy.example.com".to_string()));
}
#[test]
fn test_parse_copilot_token_without_proxy() {
let raw = "tid=abc123;exp=1700000000;sku=copilot_for_individual";
let (token, proxy) = parse_copilot_token(raw);
assert_eq!(token, raw);
assert!(proxy.is_none());
}
#[test]
fn test_parse_copilot_token_simple() {
let raw = "just-a-token";
let (token, proxy) = parse_copilot_token(raw);
assert_eq!(token, raw);
assert!(proxy.is_none());
}
#[test]
fn test_token_cache_empty() {
let cache = CopilotTokenCache::new();
assert!(cache.get().is_none());
}
#[test]
fn test_token_cache_set_get() {
let cache = CopilotTokenCache::new();
let token = CachedToken {
token: Zeroizing::new("test-token".to_string()),
expires_at: Instant::now() + Duration::from_secs(3600),
base_url: GITHUB_COPILOT_BASE_URL.to_string(),
};
cache.set(token);
let cached = cache.get();
assert!(cached.is_some());
assert_eq!(*cached.unwrap().token, "test-token");
}
#[test]
fn test_token_validity_check() {
// Valid token (expires in 1 hour)
let valid = CachedToken {
token: Zeroizing::new("t".to_string()),
expires_at: Instant::now() + Duration::from_secs(3600),
base_url: GITHUB_COPILOT_BASE_URL.to_string(),
};
assert!(valid.is_valid());
// Token that expires in < 5 min should be considered expired
let almost_expired = CachedToken {
token: Zeroizing::new("t".to_string()),
expires_at: Instant::now() + Duration::from_secs(60),
base_url: GITHUB_COPILOT_BASE_URL.to_string(),
};
assert!(!almost_expired.is_valid());
}
#[test]
fn test_copilot_base_url() {
assert_eq!(GITHUB_COPILOT_BASE_URL, "https://api.githubcopilot.com");
}
}