release: merge release 2.91.1 back to mainline

This merge commit returns to the previous state prior to the release but leaves the tag in the branch history.
Release created with releng/create_release.xsh

Change-Id: I29e738732bdd3cc8c9d1e3a5a3e5aa83dfec2a6f

doc/manual/src/release-notes/rl-2.91.md

@@ -1,4 +1,16 @@
 # Lix 2.91 "Dragon's Breath" (2024-08-12)
+# Lix 2.91.1 (2024-10-18)
+
+## Fixes
+- `<nix/fetchurl.nix>` now uses TLS verification [#11585](https://github.com/NixOS/nix/pull/11585)
+
+  Previously `<nix/fetchurl.nix>` did not do TLS verification. This was because the Nix sandbox in the past did not have access to TLS certificates, and Nix checks the hash of the fetched file anyway. However, this can expose authentication data from `netrc` and URLs to man-in-the-middle attackers. In addition, Nix now in some cases (such as when using impure derivations) does *not* check the hash. Therefore we have now enabled TLS verification. This means that downloads by `<nix/fetchurl.nix>` will now fail if you're fetching from a HTTPS server that does not have a valid certificate.
+
+  `<nix/fetchurl.nix>` is also known as the builtin derivation builder `builtin:fetchurl`. It's not to be confused with the evaluation-time function `builtins.fetchurl`, which was not affected by this issue.
+
+  Many thanks to [Eelco Dolstra](https://github.com/edolstra) for this.
+
+
 
 
 # Lix 2.91.0 (2024-08-12)

meson.build

@@ -417,7 +417,7 @@ check_funcs = [
   'strsignal',
   'sysconf',
 ]
-if target_machine.kernel() in ['linux', 'freebsd']
+if is_linux or is_freebsd
   # musl does not have close_range as of 2024-08-10
   # patch: https://www.openwall.com/lists/musl/2024/08/01/9
   check_funcs += [ 'close_range' ]

package.nix

@@ -30,6 +30,8 @@
   lix-clang-tidy ? null,
   llvmPackages,
   lsof,
+  # FIXME: remove default after dropping NixOS 24.05
+  lowdown-unsandboxed ? lowdown,
   lowdown,
   mdbook,
   mdbook-linkcheck,
@@ -221,7 +223,7 @@ stdenv.mkDerivation (finalAttrs: {
       cmake
     ]
     ++ [
-      (lib.getBin lowdown)
+      (lib.getBin lowdown-unsandboxed)
       mdbook
       mdbook-linkcheck
     ]

src/libstore/build/local-derivation-goal.cc

@@ -1364,14 +1364,21 @@ void LocalDerivationGoal::runChild()
 
         bool setUser = true;
 
-        /* Make the contents of netrc available to builtin:fetchurl
+        /* Make the contents of netrc and the CA certificate bundle
-           (which may run under a different uid and/or in a sandbox). */
+           available to builtin:fetchurl (which may run under a
+           different uid and/or in a sandbox). */
         std::string netrcData;
+        std::string caFileData;
+        if (drv->isBuiltin() && drv->builder == "builtin:fetchurl" && !derivationType->isSandboxed()) {
             try {
-            if (drv->isBuiltin() && drv->builder == "builtin:fetchurl" && !derivationType->isSandboxed())
                 netrcData = readFile(settings.netrcFile);
             } catch (SysError &) { }
 
+            try {
+                caFileData = readFile(settings.caFile);
+            } catch (SysError &) { }
+        }
+
 #if __linux__
         if (useChroot) {
 
@@ -1805,7 +1812,7 @@ void LocalDerivationGoal::runChild()
                     e.second = rewriteStrings(e.second, inputRewrites);
 
                 if (drv->builder == "builtin:fetchurl")
-                    builtinFetchurl(drv2, netrcData);
+                    builtinFetchurl(drv2, netrcData, caFileData);
                 else if (drv->builder == "builtin:buildenv")
                     builtinBuildenv(drv2);
                 else if (drv->builder == "builtin:unpack-channel")

src/libstore/builtins.hh

@@ -6,7 +6,7 @@
 namespace nix {
 
 // TODO: make pluggable.
-void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData);
+void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData, const std::string & caFileData);
 void builtinUnpackChannel(const BasicDerivation & drv);
 
 }

src/libstore/builtins/fetchurl.cc

@@ -6,7 +6,7 @@
 
 namespace nix {
 
-void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
+void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData, const std::string & caFileData)
 {
     /* Make the host's netrc data available. Too bad curl requires
        this to be stored in a file. It would be nice if we could just
@@ -16,6 +16,9 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
         writeFile(settings.netrcFile, netrcData, 0600);
     }
 
+    settings.caFile = "ca-certificates.crt";
+    writeFile(settings.caFile, caFileData, 0600);
+
     auto getAttr = [&](const std::string & name) {
         auto i = drv.env.find(name);
         if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
@@ -32,10 +35,7 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
 
     auto fetch = [&](const std::string & url) {
 
-        /* No need to do TLS verification, because we check the hash of
-           the result anyway. */
         FileTransferRequest request(url);
-        request.verifyTLS = false;
 
         auto raw = fileTransfer->download(std::move(request));
         auto decompressor = makeDecompressionSource(

src/libutil/file-descriptor.cc

@@ -228,7 +228,7 @@ void closeExtraFDs()
     auto closeRange = [](unsigned int first, unsigned int last, int flags) -> int {
       // musl does not have close_range as of 2024-08-10
       // patch: https://www.openwall.com/lists/musl/2024/08/01/9
-#ifdef HAVE_CLOSE_RANGE
+#if HAVE_CLOSE_RANGE
         return close_range(first, last, flags);
 #else
         return syscall(SYS_close_range, first, last, flags);

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;
 }

tests/nixos/fetchurl.nix

@@ -0,0 +1,84 @@
+# 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"
+
+    out = machine.succeed("cat ${badCert}/cert.pem > /tmp/cafile.pem; curl --cacert /tmp/cafile.pem https://bad/index.html")
+    assert out == "foobar\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
+
+    # Fetching from a server with a trusted cert should work via environment variable override.
+    machine.succeed("NIX_SSL_CERT_FILE=/tmp/cafile.pem nix build --no-substitute --expr 'import <nix/fetchurl.nix> { url = \"https://bad/index.html\"; hash = \"sha256-rsBwZF/lPuOzdjBZN2E08FjMM3JHyXit0Xi2zN+wAZ8=\"; }'")
+  '';
+}

version.json

@@ -1,5 +1,5 @@
 {
-    "version": "2.91.0",
+    "version": "2.91.1",
     "official_release": false,
     "release_name": "Dragon's Breath"
 }