cloudfoundry · Samze · Aug 27, 2026
diff --git a/jobs/cc_deployment_updater/templates/post-start.sh.erb b/jobs/cc_deployment_updater/templates/post-start.sh.erb
@@ -2,13 +2,15 @@
 
 set -ex
 
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
+
 function fix_bundler_home_permissions {
   BUNDLER_DIR1=/tmp/bundler
   BUNDLER_DIR2=/var/vcap/data/cc_deployment_updater/tmp/bundler
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
   chown vcap:vcap -R $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
 }
 
 fix_bundler_home_permissions
diff --git a/jobs/cc_deployment_updater/templates/pre-start.sh.erb b/jobs/cc_deployment_updater/templates/pre-start.sh.erb
@@ -3,6 +3,7 @@
 set -ex
 
 source /var/vcap/packages/capi_utils/output_utils.sh
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
 write_output_with_datetime
 
 SCRIPT_DIR="$(dirname "${BASH_SOURCE[0]}")"
@@ -19,8 +20,8 @@ function setup_directories {
   chown -R vcap:vcap "$LOG_DIR"
 
   BUNDLER_DIR=/var/vcap/data/cc_deployment_updater/tmp/bundler
-  chpst -u vcap:vcap bash -c "mkdir -p $BUNDLER_DIR"
-  chpst -u vcap:vcap bash -c "chmod -R go-w $BUNDLER_DIR"
+  run_as_vcap bash -c "mkdir -p $BUNDLER_DIR"
+  run_as_vcap bash -c "chmod -R go-w $BUNDLER_DIR"
 }
 
 function main {

diff --git a/jobs/cloud_controller_clock/templates/post-start.sh.erb b/jobs/cloud_controller_clock/templates/post-start.sh.erb
@@ -2,13 +2,15 @@
 
 set -ex
 
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
+
 function fix_bundler_home_permissions {
   BUNDLER_DIR1=/tmp/bundler
   BUNDLER_DIR2=/var/vcap/data/cloud_controller_clock/tmp/bundler
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
   chown vcap:vcap -R $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
 }
 
 fix_bundler_home_permissions
diff --git a/jobs/cloud_controller_clock/templates/pre-start.sh.erb b/jobs/cloud_controller_clock/templates/pre-start.sh.erb
@@ -2,12 +2,14 @@
 
 set -ex
 
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
+
 mkdir -p "/var/vcap/data/cloud_controller_clock/tmp"
 chown vcap:vcap "/var/vcap/data/cloud_controller_clock/tmp"
 
 BUNDLER_DIR=/var/vcap/data/cloud_controller_clock/tmp/bundler
-chpst -u vcap:vcap mkdir -p $BUNDLER_DIR
-chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR
+run_as_vcap mkdir -p $BUNDLER_DIR
+run_as_vcap chmod -R go-w $BUNDLER_DIR
 
 SCRIPT_DIR="$(dirname "${BASH_SOURCE[0]}")"
 source "${SCRIPT_DIR}/ruby_version.sh"

diff --git a/jobs/cloud_controller_ng/templates/perform_blobstore_benchmarks.erb b/jobs/cloud_controller_ng/templates/perform_blobstore_benchmarks.erb
@@ -2,6 +2,7 @@
 set -e
 
 source /var/vcap/jobs/cloud_controller_ng/bin/ruby_version.sh
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
 
 CC_JOB_DIR="/var/vcap/jobs/cloud_controller_ng"
 CC_PACKAGE_DIR="/var/vcap/packages/cloud_controller_ng"
@@ -12,7 +13,7 @@ export BUNDLE_GEMFILE="${CC_PACKAGE_DIR}/cloud_controller_ng/Gemfile"
 function perform_blobstore_benchmarks {
   echo "Performing blobstore benchmarks"
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap bundle exec rake benchmarks:perform_blobstore_benchmark
+    run_as_vcap bundle exec rake benchmarks:perform_blobstore_benchmark
   popd > /dev/null
 }
 

diff --git a/jobs/cloud_controller_ng/templates/post-start.sh.erb b/jobs/cloud_controller_ng/templates/post-start.sh.erb
@@ -33,22 +33,23 @@ export BUNDLE_GEMFILE="${CC_PACKAGE_DIR}/cloud_controller_ng/Gemfile"
 source "${CC_JOB_DIR}/bin/ruby_version.sh"
 source /var/vcap/packages/capi_utils/output_utils.sh
 source /var/vcap/packages/capi_utils/monit_utils.sh
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
 
 write_output_with_datetime
 
 function fix_bundler_home_permissions {
   BUNDLER_DIR1=/tmp/bundler
   BUNDLER_DIR2=/var/vcap/data/cloud_controller_ng/tmp/bundler
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
   chown vcap:vcap -R $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
 }
 
 function install_buildpacks {
   <% if spec.bootstrap %>
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap bundle exec rake buildpacks:install
+    run_as_vcap bundle exec rake buildpacks:install
 
     if [[ $? -ne 0 ]]; then
       echo "Buildpacks installation failed"

diff --git a/jobs/cloud_controller_ng/templates/pre-start.sh.erb b/jobs/cloud_controller_ng/templates/pre-start.sh.erb
@@ -4,6 +4,7 @@ set -ex
 export LANG="en_US.UTF-8"
 
 source /var/vcap/packages/capi_utils/output_utils.sh
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
 write_output_with_datetime
 
 CC_JOB_DIR="/var/vcap/jobs/cloud_controller_ng"
@@ -14,8 +15,8 @@ export CLOUD_CONTROLLER_NG_CONFIG="${CONFIG_DIR}/cloud_controller_ng.yml"
   # DB migrations, seeding and encryption-key validation run here in pre-start
   # (outside bpm) and open a ccdb connection. Disable MySQL TLS peer
   # verification when no ccdb.ca_cert is set. See the config/bpm.yml template
-  # for the rationale. chpst preserves this exported env for the migrate/seed/
-  # validate scripts.
+  # for the rationale. run_as_vcap preserves this exported env for the
+  # migrate/seed/validate scripts.
   ca_cert_configured = false
   if_p("ccdb.ca_cert") { |ca_cert| ca_cert_configured = !ca_cert.to_s.strip.empty? }
   if p("ccdb.db_scheme") == "mysql" && !ca_cert_configured
@@ -74,8 +75,8 @@ function setup_api_directories {
 
   BUNDLER_DIR1=/tmp/bundler
   BUNDLER_DIR2=/var/vcap/data/cloud_controller_ng/tmp/bundler
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
 
   # Configure the core file location
   <% if p("cc.core_file_pattern") %>
@@ -97,19 +98,19 @@ function setup_directories {
 
 function perform_migration {
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap "${SCRIPT_DIR}/migrate_db"
+    run_as_vcap "${SCRIPT_DIR}/migrate_db"
   popd > /dev/null
 }
 
 function seed_db {
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap "${SCRIPT_DIR}/seed_db"
+    run_as_vcap "${SCRIPT_DIR}/seed_db"
   popd > /dev/null
 }
 
 function validate_encryption_keys {
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap "${SCRIPT_DIR}/validate_encryption_keys"
+    run_as_vcap "${SCRIPT_DIR}/validate_encryption_keys"
   popd > /dev/null
 }
 
@@ -130,7 +131,7 @@ function start_bosh_dns_or_consul {
 
 function stack_check() {
   pushd "${CC_PACKAGE_DIR}/cloud_controller_ng" > /dev/null
-    chpst -u vcap:vcap "${SCRIPT_DIR}/stack_check"
+    run_as_vcap "${SCRIPT_DIR}/stack_check"
   popd > /dev/null
 }
 
@@ -140,7 +141,7 @@ function start_consul_agent {
     # If consul is already running, start exits 1
     set +e
     /var/vcap/jobs/consul_agent/bin/pre-start
-    chpst -u vcap:vcap /var/vcap/jobs/consul_agent/bin/agent_ctl start &> /dev/null
+    run_as_vcap /var/vcap/jobs/consul_agent/bin/agent_ctl start &> /dev/null
     set -e
   fi
 }

diff --git a/jobs/cloud_controller_worker/templates/post-start.sh.erb b/jobs/cloud_controller_worker/templates/post-start.sh.erb
@@ -2,13 +2,15 @@
 
 set -ex
 
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
+
 function fix_bundler_home_permissions {
   BUNDLER_DIR1=/tmp/bundler
   BUNDLER_DIR2="<%= p("cc.directories.tmpdir") %>/bundler"
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap mkdir -p $BUNDLER_DIR1 $BUNDLER_DIR2
   chown vcap:vcap -R $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
-  chpst -u vcap:vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R go-w $BUNDLER_DIR1 $BUNDLER_DIR2
+  run_as_vcap chmod -R +t $BUNDLER_DIR1 $BUNDLER_DIR2
 }
 
 fix_bundler_home_permissions

diff --git a/jobs/cloud_controller_worker/templates/pre-start.sh.erb b/jobs/cloud_controller_worker/templates/pre-start.sh.erb
@@ -3,6 +3,7 @@
 set -ex
 
 source /var/vcap/packages/capi_utils/output_utils.sh
+source /var/vcap/packages/capi_utils/privdrop_utils.sh
 write_output_with_datetime
 
 
@@ -21,8 +22,8 @@ function setup_directories {
   chown vcap:vcap "<%= p("cc.directories.tmpdir") %>"
 
   BUNDLER_DIR="<%= p("cc.directories.tmpdir") %>/bundler"
-  chpst -u vcap:vcap mkdir -p $BUNDLER_DIR
-  chpst -u vcap:vcap chmod -R go-w $BUNDLER_DIR
+  run_as_vcap mkdir -p $BUNDLER_DIR
+  run_as_vcap chmod -R go-w $BUNDLER_DIR
 }
 
 function main {

diff --git a/packages/capi_utils/spec b/packages/capi_utils/spec
@@ -6,3 +6,4 @@ files:
 - capi_utils/pid_utils.sh
 - capi_utils/output_utils.sh
 - capi_utils/monit_utils.sh
+- capi_utils/privdrop_utils.sh
diff --git a/src/capi_utils/privdrop_utils.sh b/src/capi_utils/privdrop_utils.sh
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+# run_as_vcap
+#
+# Exec-style replacement for `chpst -u vcap:vcap "$@"`.
+function run_as_vcap() {
+  setpriv --reuid=vcap --regid=vcap --clear-groups --no-new-privs -- "$@"
+}
diff --git a/src/capi_utils/privdrop_utils_test.bats b/src/capi_utils/privdrop_utils_test.bats
@@ -0,0 +1,30 @@
+#!/usr/bin/env bats
+
+setup() {
+  source ./privdrop_utils.sh
+}
+
+@test "run_as_vcap runs the given command as the vcap user" {
+  run run_as_vcap id -un
+  [ "$status" -eq 0 ]
+  [ "$output" = "vcap" ]
+}
+
+@test "run_as_vcap runs the given command as the vcap group" {
+  run run_as_vcap id -gn
+  [ "$status" -eq 0 ]
+  [ "$output" = "vcap" ]
+}
+
+@test "run_as_vcap preserves multiple arguments without re-quoting" {
+  run run_as_vcap echo one two three
+  [ "$status" -eq 0 ]
+  [ "$output" = "one two three" ]
+}
+
+@test "run_as_vcap preserves exported environment variables" {
+  export PRIVDROP_TEST_VAR="some_value"
+  run run_as_vcap sh -c 'echo "$PRIVDROP_TEST_VAR"'
+  [ "$status" -eq 0 ]
+  [ "$output" = "some_value" ]
+}