cc-wrapper: add stack clash protection hardening flag

Most Linux distributions are enabling this these days and it does
protect against real world vulnerabilities as demonstrated by
CVE-2018-16864 and CVE-2018-16865.

Fix #53753.

Information on llvm version support gleaned from
6609892a2d
68e07da3e5
092507a730

Information on gcc version support a lot harder to gather,
but both 32bit and 64bit arm do appear to be supported
based on the test suite.

pkgs/build-support/cc-wrapper/add-hardening.sh

@@ -32,7 +32,7 @@ if [[ -n "${hardeningEnableMap[fortify3]-}" ]]; then
 fi
 
 if (( "${NIX_DEBUG:-0}" >= 1 )); then
-  declare -a allHardeningFlags=(fortify fortify3 stackprotector pie pic strictoverflow format trivialautovarinit zerocallusedregs)
+  declare -a allHardeningFlags=(fortify fortify3 stackprotector stackclashprotection pie pic strictoverflow format trivialautovarinit zerocallusedregs)
   declare -A hardeningDisableMap=()
 
   # Determine which flags were effectively disabled so we can report below.
@@ -79,6 +79,10 @@ for flag in "${!hardeningEnableMap[@]}"; do
       if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stackprotector >&2; fi
       hardeningCFlagsBefore+=('-fstack-protector-strong' '--param' 'ssp-buffer-size=4')
       ;;
+    stackclashprotection)
+      if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling stack-clash-protection >&2; fi
+      hardeningCFlagsBefore+=('-fstack-clash-protection')
+      ;;
     pie)
       # NB: we do not use `+=` here, because PIE flags must occur before any PIC flags
       if (( "${NIX_DEBUG:-0}" >= 1 )); then echo HARDENING: enabling CFlags -fPIE >&2; fi

pkgs/development/compilers/gcc/default.nix

@@ -280,7 +280,7 @@ pipe ((callFile ./common/builder.nix {}) ({
 
   libc_dev = stdenv.cc.libc_dev;
 
-  hardeningDisable = [ "format" "pie" ]
+  hardeningDisable = [ "format" "pie" "stackclashprotection" ]
   ++ optionals (is11 && langAda) [ "fortify3" ];
 
   postPatch = optionalString atLeast7 ''
@@ -425,6 +425,9 @@ pipe ((callFile ./common/builder.nix {}) ({
     inherit langC langCC langObjC langObjCpp langAda langFortran langGo langD langJava version;
     isGNU = true;
     hardeningUnsupportedFlags = optional is48 "stackprotector"
+      ++ optional (
+        (targetPlatform.isAarch64 && !atLeast9) || !atLeast8
+      ) "stackclashprotection"
       ++ optional (!atLeast11) "zerocallusedregs"
       ++ optionals (!atLeast12) [ "fortify3" "trivialautovarinit" ]
       ++ optionals (langFortran) [ "fortify" "format" ];

pkgs/development/compilers/llvm/common/clang/default.nix

@@ -134,16 +134,26 @@ let
     passthru = {
       inherit libllvm;
       isClang = true;
-    } // (lib.optionalAttrs (lib.versionAtLeast release_version "15") {
-      hardeningUnsupportedFlags = [
-        "fortify3"
-      ];
       hardeningUnsupportedFlagsByTargetPlatform = targetPlatform:
-        lib.optional (!(targetPlatform.isx86_64 || targetPlatform.isAarch64)) "zerocallusedregs"
+        [ "fortify3" ]
+        ++ lib.optional (
+          (lib.versionOlder release_version "11")
+          || (targetPlatform.isAarch64 && (lib.versionOlder release_version "18.1"))
+          || (targetPlatform.isFreeBSD && (lib.versionOlder release_version "15"))
+          || !(targetPlatform.isLinux || targetPlatform.isFreeBSD)
+          || !(
+            targetPlatform.isx86
+            || targetPlatform.isPower64
+            || targetPlatform.isS390x
+            || targetPlatform.isAarch64
+          )
+        ) "stackclashprotection"
+        ++ lib.optional (
+          (lib.versionOlder release_version "15")
+          || !(targetPlatform.isx86_64 || targetPlatform.isAarch64)
+        ) "zerocallusedregs"
         ++ (finalAttrs.passthru.hardeningUnsupportedFlags or []);
-    }) // (lib.optionalAttrs (lib.versionOlder release_version "15") {
-      hardeningUnsupportedFlags = [ "fortify3" "zerocallusedregs" ];
-    });
+    };
 
     meta = llvm_meta // {
       homepage = "https://clang.llvm.org/";

pkgs/stdenv/darwin/default.nix

@@ -327,7 +327,11 @@ in
               '';
               passthru = {
                 isFromBootstrapFiles = true;
-                hardeningUnsupportedFlags = [ "fortify3" "zerocallusedregs" ];
+                hardeningUnsupportedFlags = [
+                  "fortify3"
+                  "stackclashprotection"
+                  "zerocallusedregs"
+                ];
               };
             };
             clang-unwrapped = selfTools.libclang;

pkgs/stdenv/generic/make-derivation.nix

@@ -119,6 +119,7 @@ let
     "pie"
     "relro"
     "stackprotector"
+    "stackclashprotection"
     "strictoverflow"
     "trivialautovarinit"
     "zerocallusedregs"

pkgs/stdenv/linux/bootstrap-tools/default.nix

@@ -15,5 +15,10 @@ derivation ({
   langC = true;
   langCC = true;
   isGNU = true;
-  hardeningUnsupportedFlags = [ "fortify3" "zerocallusedregs" "trivialautovarinit" ];
+  hardeningUnsupportedFlags = [
+    "fortify3"
+    "stackclashprotection"
+    "trivialautovarinit"
+    "zerocallusedregs"
+  ];
 } // extraAttrs)

pkgs/top-level/stage.nix

@@ -292,6 +292,7 @@ let
           pkgsExtraHardening = super';
           stdenv = super'.withDefaultHardeningFlags (
             super'.stdenv.cc.defaultHardeningFlags ++ [
+              "stackclashprotection"
               "trivialautovarinit"
             ]
           ) super'.stdenv;