From 690d0ed1bb3c9d3b22e3b50aebbcd4bb3b3764d0 Mon Sep 17 00:00:00 2001
From: Jake Howard <git@theorangeone.net>
Date: Wed, 29 Dec 2021 16:17:38 +0000
Subject: [PATCH] Add our own HTTP date formatter

---
 Cargo.lock  |  1 -
 Cargo.toml  |  1 -
 src/util.rs | 19 +++++++++++++++----
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 1a048db5..8af4f0ea 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3295,7 +3295,6 @@ dependencies = [
  "governor",
  "handlebars",
  "html5ever",
- "httpdate",
  "idna 0.2.3",
  "job_scheduler",
  "jsonwebtoken",
diff --git a/Cargo.toml b/Cargo.toml
index 82c96386..f6ff7f68 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -80,7 +80,6 @@ uuid = { version = "0.8.2", features = ["v4"] }
 chrono = { version = "0.4.19", features = ["serde"] }
 chrono-tz = "0.6.1"
 time = "0.2.27"
-httpdate = "1.0"
 
 # Job scheduler
 job_scheduler = "1.2.1"
diff --git a/src/util.rs b/src/util.rs
index 1d70e097..0b287ccf 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -11,9 +11,8 @@ use rocket::{
     Data, Request, Response, Rocket,
 };
 
-use httpdate::HttpDate;
 use std::thread::sleep;
-use std::time::{Duration, SystemTime};
+use std::time::Duration;
 
 use crate::CONFIG;
 
@@ -143,12 +142,13 @@ impl<'r, R: Responder<'r>> Responder<'r> for Cached<R> {
             format!("public, max-age={}", self.ttl)
         };
 
-        let time_now = SystemTime::now();
+        let time_now = chrono::Local::now();
 
         match self.response.respond_to(req) {
             Ok(mut res) => {
                 res.set_raw_header("Cache-Control", cache_control_header);
-                res.set_raw_header("Expires", HttpDate::from(time_now + Duration::from_secs(self.ttl)).to_string());
+                let expiry_time = time_now + chrono::Duration::seconds(self.ttl.try_into().unwrap());
+                res.set_raw_header("Expires", format_datetime_http(&expiry_time));
                 Ok(res)
             }
             e @ Err(_) => e,
@@ -436,6 +436,17 @@ pub fn format_naive_datetime_local(dt: &NaiveDateTime, fmt: &str) -> String {
     format_datetime_local(&Local.from_utc_datetime(dt), fmt)
 }
 
+/// Formats a `DateTime<Local>` as required for HTTP
+///
+/// https://httpwg.org/specs/rfc7231.html#http.date
+pub fn format_datetime_http(dt: &DateTime<Local>) -> String {
+    let expiry_time: chrono::DateTime<chrono::Utc> = chrono::DateTime::from_utc(dt.naive_utc(), chrono::Utc);
+
+    // HACK: HTTP expects the date to always be GMT (UTC) rather than giving an
+    // offset (which would always be 0 in UTC anyway)
+    return expiry_time.to_rfc2822().replace("+0000", "GMT");
+}
+
 //
 // Deployment environment methods
 //