Nix libcrypto helpers

flake.nix

@@ -94,6 +94,12 @@
           buildInputs = [ pkgs.cmake openssl_3_0 ];
           packages = common_packages;
           S2N_LIBCRYPTO = "openssl-3.0";
+          OPENSSL_1_0_2_INSTALL_DIR = "${openssl_1_0_2}";
+          OPENSSL_1_1_1_INSTALL_DIR = "${openssl_1_1_1}";
+          OPENSSL_3_0_INSTALL_DIR = "${openssl_3_0}";
+          AWSLC_INSTALL_DIR = "${aws-lc}";
+          GNUTLS_INSTALL_DIR = "${pkgs.gnutls}";
+          LIBRESSL_INSTALL_DIR = "${libressl}";
           # Integ s_client/server tests expect openssl 1.1.1.
           shellHook = ''
             echo Setting up $S2N_LIBCRYPTO environment from flake.nix...

nix/shell.sh

@@ -9,6 +9,21 @@ banner()
     echo "+---------------------------------------------------------+"
 }
 
+function libcrypto_alias {
+    if [[ -f $2 ]]; then
+      alias $1=$2
+      echo "Libcrypto $2 available as $1"
+      else
+      banner "Could not find libcrdypto $2 for alias"
+    fi
+}
+libcrypto_alias openssl102 "${OPENSSL_1_0_2_INSTALL_DIR}/bin/openssl"
+libcrypto_alias openssl111 "${OPENSSL_1_1_1_INSTALL_DIR}/bin/openssl"
+libcrypto_alias openssl30 "${OPENSSL_3_0_INSTALL_DIR}/bin/openssl"
+libcrypto_alias bssl "${AWSLC_INSTALL_DIR}/bin/bssl"
+libcrypto_alias libressl "${LIBRESSL_INSTALL_DIR}/bin/openssl"
+libcrypto_alias gnutls-cli "${GNUTLS_INSTALL_DIR}/bin/gnutls-cli"
+
 
 function clean {
     banner "Cleanup ./build"