nix devShell with aws-lc (#4028)

Author: dougch

flake.lock

@@ -2,11 +2,14 @@
   description = "A flake for s2n-tls";
 
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11";
+  # TODO: https://github.com/aws/aws-lc/pull/830
+  inputs.awslc.url = "github:dougch/aws-lc?ref=nix";
 
-  outputs = { self, nix, nixpkgs, flake-utils }:
+  outputs = { self, nix, nixpkgs, awslc, flake-utils }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
+        aws-lc = awslc.packages.${system}.aws-lc;
         # TODO: We have parts of our CI that rely on clang-format-15, but that is only available on github:nixos/nixpkgs/nixos-unstable
         llvmPkgs = pkgs.llvmPackages_14;
         pythonEnv = import ./nix/pyenv.nix { pkgs = pkgs; };
@@ -143,6 +146,21 @@
             '';
           });
 
+        devShells.awslc = devShells.default.overrideAttrs
+          (finalAttrs: previousAttrs: {
+            # Re-include cmake to update the environment with a new libcrypto.
+            buildInputs = [ pkgs.cmake aws-lc ];
+            S2N_LIBCRYPTO = "awslc";
+            # Integ s_client/server tests expect openssl 1.1.1.
+            # GnuTLS-cli and serv utilities needed for some integration tests.
+            shellHook = ''
+              echo Setting up $S2N_LIBCRYPTO environment from flake.nix...
+              export PATH=${openssl_1_1_1}/bin:$PATH
+              export PS1="[nix $S2N_LIBCRYPTO] $PS1"
+              source ${writeScript ./nix/shell.sh}
+            '';
+          });
+
         # Used to backup the devShell to s3 for caching.
         packages.devShell = devShells.default.inputDerivation;
         packages.default = packages.s2n-tls;

flake.nix

@@ -113,7 +113,7 @@ function test_toolchain_counts {
     # This is a starting point for a unit test of the devShell.
     # The choosen S2N_LIBCRYPTO should be 2, and the others should be zero.
     banner "Checking the CMAKE_INCLUDE_PATH for libcrypto counts"
-    echo $CMAKE_INCLUDE_PATH|gawk 'BEGIN{RS=":"; o10=0; o11=0; o3=0;awslc=0}
+    echo $CMAKE_INCLUDE_PATH|gawk 'BEGIN{RS=":"; o10=0; o11=0; o3=0;awslc=0;libre=0}
       /openssl-3.0/{o3++}
       /openssl-1.1/{o11++}
       /openssl-1.0/{o10++}