Add ability to add request headers to proxied requests

.dev-config.yml

@@ -5,7 +5,14 @@ domain:
   builtins:
     foo:
       kind: proxy
-      url: http://ok
+      url: http://127.0.0.1:9000
+      request_http_headers:
+        - name: x-foo
+          value: BAR
+        - name: host
+          value: hi
+        - name: user-agent
+          value: ""
     bar:
       kind: git
       url: a

README.md

@@ -66,13 +66,24 @@ domain:
     #  public: false
 
     # An example built-in domain backed by a reverse-proxy to some other
-    # web-service. Proxies are currently limited in the following ways:
+    # web-service. Requests to the backing service will automatically have
+    # X-Forwarded-For and (if HTTPS) X-Forwarded-Proto headers added to them.
+    #
+    # Proxies are currently limited in the following ways:
     # * url must be to an http endpoint (not https)
     # * dns.resolver_addr is ignored and the system-wide dns is used
     #
     #proxy.example.com:
     #  kind: proxy
     #  url: "http://some.other.service.com"
+    #
+    #  # Extra headers to add to requests being proxied
+    #  request_http_headers:
+    #    - name: Host
+    #      value: "yet.another.service.com"
+    #    - name: X-HEADER-TO-DELETE
+    #      value: ""
+    #
     #  public: false
 
 service:

src/main.rs

@@ -79,7 +79,9 @@ async fn main() {
         }
 
         for (domain, builtin_domain) in &config.domain.builtins {
-            if let domani::origin::Descr::Proxy { ref url } = builtin_domain.settings.origin_descr {
+            if let domani::origin::Descr::Proxy { ref url, .. } =
+                builtin_domain.settings.origin_descr
+            {
                 if let Err(e) = domani::origin::proxy::validate_proxy_url(url) {
                     panic!("invalid config for builtin domain {domain}: {e}");
                 }

src/origin/descr.rs

@@ -2,6 +2,12 @@ use hex::ToHex;
 use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct DescrProxyHttpHeader {
+    pub name: String,
+    pub value: String,
+}
+
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 #[serde(tag = "kind")]
 /// A unique description of an origin, from where a domain might be served.
@@ -10,7 +16,10 @@ pub enum Descr {
     Git { url: String, branch_name: String },
 
     #[serde(rename = "proxy")]
-    Proxy { url: String },
+    Proxy {
+        url: String,
+        request_http_headers: Vec<DescrProxyHttpHeader>,
+    },
 }
 
 impl Descr {
@@ -29,9 +38,17 @@ impl Descr {
                 h_update(url);
                 h_update(branch_name);
             }
-            Descr::Proxy { url } => {
+            Descr::Proxy {
+                url,
+                request_http_headers,
+            } => {
                 h_update("proxy");
                 h_update(url);
+                for h in request_http_headers {
+                    h_update("header");
+                    h_update(&h.name);
+                    h_update(&h.value);
+                }
             }
         }
 

src/origin/proxy.rs

@@ -1,6 +1,6 @@
 use crate::error::unexpected::{self, Mappable};
 use crate::{domain, origin};
-use http::header::HeaderValue;
+use http::header::{HeaderName, HeaderValue};
 use std::{net, str::FromStr};
 
 // proxy is a special case because it is so tied to the underlying protocol that a request is
@@ -30,33 +30,37 @@ pub async fn serve_http_request(
     mut req: hyper::Request<hyper::Body>,
     req_is_https: bool,
 ) -> unexpected::Result<hyper::Response<hyper::Body>> {
-    let proxy_url = if let origin::Descr::Proxy { ref url } = settings.origin_descr {
-        url
+    let (proxy_url, request_http_headers) = if let origin::Descr::Proxy {
+        ref url,
+        ref request_http_headers,
+    } = settings.origin_descr
+    {
+        (url, request_http_headers)
     } else {
         panic!("non-proxy domain settings passed in: {settings:?}")
     };
 
-    let parsed_proxy_url =
-        http::Uri::from_str(proxy_url).or_unexpected_while("parsing proxy url {proxy_url}")?;
+    for header in request_http_headers {
+        let name: HeaderName = header
+            .name
+            .as_str()
+            .try_into()
+            .map_unexpected_while(|| format!("parsing header name {}", &header.name))?;
 
-    // figure out what the host header should be, based on the host[:port] of the proxy_url
-    let host = {
-        let authority = parsed_proxy_url.authority().or_unexpected_while(format!(
-            "getting host from proxy url {proxy_url}, there is no host"
-        ))?;
+        if header.value == "" {
+            req.headers_mut().remove(name);
+            continue;
+        }
 
-        let host_and_port;
-        let mut host = authority.host();
+        let value = HeaderValue::from_str(&header.value).map_unexpected_while(|| {
+            format!(
+                "parsing {} as value for header {}",
+                &header.value, &header.name
+            )
+        })?;
 
-        if let Some(port) = authority.port() {
-            host_and_port = format!("{host}:{port}");
-            host = host_and_port.as_str();
-        };
-
-        HeaderValue::from_str(host).or_unexpected()?
-    };
-
-    req.headers_mut().insert("host", host);
+        req.headers_mut().insert(name, value);
+    }
 
     if req_is_https {
         req.headers_mut()