openssh: fix linkOpenSSL=false by linking libxcrypt

Possibly broken during https://github.com/NixOS/nixpkgs/pull/181764

Context: https://sourceware.org/legacy-ml/libc-alpha/2017-08/msg01257.html

nixos/tests/openssh.nix

@@ -1,7 +1,7 @@
 import ./make-test-python.nix ({ pkgs, ... }:
 
 let inherit (import ./ssh-keys.nix pkgs)
-      snakeOilPrivateKey snakeOilPublicKey;
+      snakeOilPrivateKey snakeOilPublicKey snakeOilEd25519PrivateKey snakeOilEd25519PublicKey;
 in {
   name = "openssh";
   meta = with pkgs.lib.maintainers; {
@@ -108,6 +108,31 @@ in {
         };
       };
 
+    server-no-openssl =
+      { ... }:
+      {
+        programs.ssh.package = pkgs.opensshPackages.openssh.override {
+          linkOpenssl = false;
+        };
+        services.openssh = {
+          enable = true;
+          hostKeys = [
+            { type = "ed25519"; path = "/etc/ssh/ssh_host_ed25519_key"; }
+          ];
+          settings = {
+            # Must not specify the OpenSSL provided algorithms.
+            Ciphers = [ "chacha20-poly1305@openssh.com" ];
+            KexAlgorithms = [
+              "curve25519-sha256"
+              "curve25519-sha256@libssh.org"
+            ];
+          };
+        };
+        users.users.root.openssh.authorizedKeys.keys = [
+          snakeOilEd25519PublicKey
+        ];
+      };
+
     server-no-pam =
       { pkgs, ... }:
       {
@@ -139,6 +164,7 @@ in {
     server_allowed_users.wait_for_unit("sshd", timeout=30)
     server_localhost_only.wait_for_unit("sshd", timeout=30)
     server_match_rule.wait_for_unit("sshd", timeout=30)
+    server_no_openssl.wait_for_unit("sshd", timeout=30)
     server_no_pam.wait_for_unit("sshd", timeout=30)
 
     server_lazy.wait_for_unit("sshd.socket", timeout=30)
@@ -230,6 +256,16 @@ in {
             timeout=30
         )
 
+    with subtest("no-openssl"):
+        client.succeed(
+            "cat ${snakeOilEd25519PrivateKey} > privkey.snakeoil"
+        )
+        client.succeed("chmod 600 privkey.snakeoil")
+        client.succeed(
+            "ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -i privkey.snakeoil server-no-openssl true",
+            timeout=30
+        )
+
     with subtest("no-pam"):
         client.succeed(
             "cat ${snakeOilPrivateKey} > privkey.snakeoil"

nixos/tests/ssh-keys.nix

@@ -12,4 +12,16 @@ pkgs:
     "yNTYAAABBBChdA2BmwcG49OrQN33f/sj+OHL5sJhwVl2Qim0vkUJQCry1zFpKTa"
     "9ZcDMiWaEhoAR6FGoaGI04ff7CS+1yybQ= snakeoil"
   ];
+
+  snakeOilEd25519PrivateKey = pkgs.writeText "privkey.snakeoil" ''
+    -----BEGIN OPENSSH PRIVATE KEY-----
+    b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+    QyNTUxOQAAACAYBTIWo1J4PkY4/7AhVyPT8xvAUI67tp+yYFFRdSm7+QAAAJC89yCivPcg
+    ogAAAAtzc2gtZWQyNTUxOQAAACAYBTIWo1J4PkY4/7AhVyPT8xvAUI67tp+yYFFRdSm7+Q
+    AAAEDJmKp3lX6Pz0unTc0QZwrHb8Eyr9fJUopE9d2/+q+eCxgFMhajUng+Rjj/sCFXI9Pz
+    G8BQjru2n7JgUVF1Kbv5AAAACnRvbUBvemRlc2sBAgM=
+    -----END OPENSSH PRIVATE KEY-----
+  '';
+
+  snakeOilEd25519PublicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBgFMhajUng+Rjj/sCFXI9PzG8BQjru2n7JgUVF1Kbv5 snakeoil";
 }

pkgs/tools/networking/openssh/common.nix

@@ -26,6 +26,7 @@
 , withLdns ? true
 , libkrb5
 , libfido2
+, libxcrypt
 , hostname
 , nixosTests
 , withFIDO ? stdenv.hostPlatform.isUnix && !stdenv.hostPlatform.isMusl
@@ -63,7 +64,8 @@ stdenv.mkDerivation {
     # https://github.com/NixOS/nixpkgs/pull/107606
     ++ lib.optional withKerberos pkgs.libkrb5
     ++ extraNativeBuildInputs;
-  buildInputs = [ zlib openssl libedit ]
+  buildInputs = [ zlib libedit ]
+    ++ [ (if linkOpenssl then openssl else libxcrypt) ]
     ++ lib.optional withFIDO libfido2
     ++ lib.optional withKerberos libkrb5
     ++ lib.optional withLdns ldns