[security] builtin:fetchurl: Enable TLS verification

This is better for privacy and to avoid leaking netrc credentials in a
MITM attack, but also the assumption that we check the hash no longer
holds in some cases (in particular for impure derivations).

Partially reverts https://github.com/NixOS/nix/commit/5db358d4d78aea7204a8f22c5bf2a309267ee038.

(cherry picked from commit c04bc17a5a0fdcb725a11ef6541f94730112e7b6)
(cherry picked from commit f2f47fa725fc87bfb536de171a2ea81f2789c9fb)
(cherry picked from commit 7b39cd631e0d3c3d238015c6f450c59bbc9cbc5b)

Upstream-PR: https://github.com/NixOS/nix/pull/11585

Change-Id: Ia973420f6098113da05a594d48394ce1fe41fbb9

2 files changed, 80 insertions, 0 deletions

diff --git a/tests/nixos/default.nix b/tests/nixos/default.nix
index 20e66f6c1..2d6eaed16 100644
--- a/tests/nixos/default.nix
+++ b/tests/nixos/default.nix
@@ -157,4 +157,6 @@ in
   coredumps = runNixOSTestFor "x86_64-linux" ./coredumps;
 
   io_uring = runNixOSTestFor "x86_64-linux" ./io_uring;
+
+  fetchurl = runNixOSTestFor "x86_64-linux" ./fetchurl.nix;
 }
diff --git a/tests/nixos/fetchurl.nix b/tests/nixos/fetchurl.nix
new file mode 100644
index 000000000..63c639c31
--- /dev/null
+++ b/tests/nixos/fetchurl.nix
@@ -0,0 +1,78 @@
+# Test whether builtin:fetchurl properly performs TLS certificate
+# checks on HTTPS servers.
+
+{ lib, config, pkgs, ... }:
+
+let
+
+  makeTlsCert = name: pkgs.runCommand name {
+    nativeBuildInputs = with pkgs; [ openssl ];
+  } ''
+    mkdir -p $out
+    openssl req -x509 \
+      -subj '/CN=${name}/' -days 49710 \
+      -addext 'subjectAltName = DNS:${name}' \
+      -keyout "$out/key.pem" -newkey ed25519 \
+      -out "$out/cert.pem" -noenc
+  '';
+
+  goodCert = makeTlsCert "good";
+  badCert = makeTlsCert "bad";
+
+in
+
+{
+  name = "fetchurl";
+
+  nodes = {
+    machine = { lib, pkgs, ... }: {
+      services.nginx = {
+        enable = true;
+
+        virtualHosts."good" = {
+          addSSL = true;
+          sslCertificate = "${goodCert}/cert.pem";
+          sslCertificateKey = "${goodCert}/key.pem";
+          root = pkgs.runCommand "nginx-root" {} ''
+            mkdir "$out"
+            echo 'hello world' > "$out/index.html"
+          '';
+        };
+
+        virtualHosts."bad" = {
+          addSSL = true;
+          sslCertificate = "${badCert}/cert.pem";
+          sslCertificateKey = "${badCert}/key.pem";
+          root = pkgs.runCommand "nginx-root" {} ''
+            mkdir "$out"
+            echo 'foobar' > "$out/index.html"
+          '';
+        };
+      };
+
+      security.pki.certificateFiles = [ "${goodCert}/cert.pem" ];
+
+      networking.hosts."127.0.0.1" = [ "good" "bad" ];
+
+      virtualisation.writableStore = true;
+
+      nix.settings.experimental-features = "nix-command";
+    };
+  };
+
+  testScript = { nodes, ... }: ''
+    machine.wait_for_unit("nginx")
+    machine.wait_for_open_port(443)
+
+    out = machine.succeed("curl https://good/index.html")
+    assert out == "hello world\n"
+
+    # Fetching from a server with a trusted cert should work.
+    machine.succeed("nix build --no-substitute --expr 'import <nix/fetchurl.nix> { url = \"https://good/index.html\"; hash = \"sha256-qUiQTy8PR5uPgZdpSzAYSw0u0cHNKh7A+4XSmaGSpEc=\"; }'")
+
+    # Fetching from a server with an untrusted cert should fail.
+    err = machine.fail("nix build --no-substitute --expr 'import <nix/fetchurl.nix> { url = \"https://bad/index.html\"; hash = \"sha256-rsBwZF/lPuOzdjBZN2E08FjMM3JHyXit0Xi2zN+wAZ8=\"; }' 2>&1")
+    print(err)
+    assert "SSL certificate problem: self-signed certificate" in err or "SSL peer certificate or SSH remote key was not OK" in err
+  '';
+}