From 94d164dd7f20c785a543d1fb1d5bd359fb38bd25 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 4 May 2017 20:06:40 +0200
Subject: [PATCH] Add a setup hook for detecting $TMPDIR references in RPATHs
 and wrapper scripts

---
 .../build-support/setup-hooks/audit-tmpdir.sh | 41 +++++++++++++++++++
 pkgs/stdenv/generic/default.nix               |  1 +
 pkgs/stdenv/generic/setup.sh                  | 12 ++++++
 3 files changed, 54 insertions(+)
 create mode 100644 pkgs/build-support/setup-hooks/audit-tmpdir.sh

diff --git a/pkgs/build-support/setup-hooks/audit-tmpdir.sh b/pkgs/build-support/setup-hooks/audit-tmpdir.sh
new file mode 100644
index 000000000000..ffaa61f2d809
--- /dev/null
+++ b/pkgs/build-support/setup-hooks/audit-tmpdir.sh
@@ -0,0 +1,41 @@
+# Check whether RPATHs or wrapper scripts contain references to
+# $TMPDIR. This is a serious security bug because it allows any user
+# to inject files into search paths of other users' processes.
+#
+# It might be better to have Nix scan build output for any occurrence
+# of $TMPDIR (which would also be good for reproducibility), but at
+# the moment that would produce too many spurious errors (e.g. debug
+# info or assertion messages that refer to $TMPDIR).
+
+fixupOutputHooks+=('if [ -z "$noAuditTmpdir" -a -e "$prefix" ]; then auditTmpdir "$prefix"; fi')
+
+auditTmpdir() {
+    local dir="$1"
+    [ -e "$dir" ] || return 0
+
+    header "checking for references to $TMPDIR in $dir..."
+
+    local i
+    while IFS= read -r -d $'\0' i; do
+        if [[ "$i" =~ .build-id ]]; then continue; fi
+
+        if isELF "$i"; then
+            if patchelf --print-rpath "$i" | grep -q -F "$TMPDIR"; then
+                echo "RPATH of binary $i contains a forbidden reference to $TMPDIR"
+                exit 1
+            fi
+        fi
+
+        if  isScript "$i"; then
+            if [ -e "$(dirname $i)/.$(basename $i)-wrapped" ]; then
+                if grep -q -F "$TMPDIR" "$i"; then
+                    echo "wrapper script $i contains a forbidden reference to $TMPDIR"
+                    exit 1
+                fi
+            fi
+        fi
+
+    done < <(find "$dir" -type f -print0)
+
+    stopNest
+}
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index a063a1ed2dc9..43b35082161d 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -94,6 +94,7 @@ let
       ../../build-support/setup-hooks/compress-man-pages.sh
       ../../build-support/setup-hooks/strip.sh
       ../../build-support/setup-hooks/patch-shebangs.sh
+      ../../build-support/setup-hooks/audit-tmpdir.sh
       ../../build-support/setup-hooks/multiple-outputs.sh
       ../../build-support/setup-hooks/move-sbin.sh
       ../../build-support/setup-hooks/move-lib64.sh
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index de33ab565982..eb63b18e5f3d 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -199,6 +199,18 @@ isELF() {
     if [[ "$magic" =~ ELF ]]; then return 0; else return 1; fi
 }
 
+# Return success if the specified file is a script (i.e. starts with
+# "#!").
+isScript() {
+    local fn="$1"
+    local magic
+    if ! [ -x /bin/sh ]; then return 0; fi
+    exec {fd}< "$fn"
+    read -n 2 -u $fd magic
+    exec {fd}<&-
+    if [[ "$magic" =~ \#! ]]; then return 0; else return 1; fi
+}
+
 
 ######################################################################
 # Initialisation.