fix: neutralize execution-capable config on an unauthenticated cache

hooks/pre-push

@@ -43,7 +43,18 @@ done
 unset _v
 
 shared_git() {
-  env "${_shared_git_scrub[@]}" git "$@"
+  # `-c` overrides neutralize execution-capable settings a poisoned checkout
+  # could plant in its own .git/config: core.fsmonitor runs a command during
+  # `git status`, and the *Proxy/*Command hooks run during fetch.
+  env "${_shared_git_scrub[@]}" git \
+    -c core.fsmonitor= \
+    -c core.hooksPath=/dev/null \
+    -c core.sshCommand= \
+    -c core.askPass= \
+    -c credential.helper= \
+    -c protocol.ext.allow=never \
+    -c uploadpack.packObjectsHook= \
+    "$@"
 }
 
 scanner="$shared_dir/scripts/scan-commit-range.sh"

scripts/bootstrap.sh

@@ -71,7 +71,19 @@ policy_git() {
   for v in GIT_CONFIG_GLOBAL GIT_CONFIG_SYSTEM GIT_CONFIG_NOSYSTEM; do
     scrub+=(-u "$v")
   done
-  env "${scrub[@]}" git "$@"
+  # `-c` overrides neutralize execution-capable settings a poisoned cache could
+  # plant in its own .git/config: core.fsmonitor runs a command during `git
+  # status`, and the *Proxy/*Command hooks run during fetch. These must be off
+  # for every command that touches a cache we have not yet authenticated.
+  env "${scrub[@]}" git \
+    -c core.fsmonitor= \
+    -c core.hooksPath=/dev/null \
+    -c core.sshCommand= \
+    -c core.askPass= \
+    -c credential.helper= \
+    -c protocol.ext.allow=never \
+    -c uploadpack.packObjectsHook= \
+    "$@"
 }
 
 cleanup() {

scripts/install-pre-push.sh

@@ -74,7 +74,18 @@ done
 unset _v
 
 shared_git() {
-  env "${_shared_git_scrub[@]}" git "$@"
+  # `-c` overrides neutralize execution-capable settings a poisoned checkout
+  # could plant in its own .git/config: core.fsmonitor runs a command during
+  # `git status`, and the *Proxy/*Command hooks run during fetch.
+  env "${_shared_git_scrub[@]}" git \
+    -c core.fsmonitor= \
+    -c core.hooksPath=/dev/null \
+    -c core.sshCommand= \
+    -c core.askPass= \
+    -c credential.helper= \
+    -c protocol.ext.allow=never \
+    -c uploadpack.packObjectsHook= \
+    "$@"
 }
 
 shared_git -C "$shared_dir" rev-parse --is-inside-work-tree >/dev/null 2>&1 || {

tests/run.sh

@@ -256,6 +256,23 @@ if VANA_POLICY_SHA="$policy_sha" "$bootstrap" bogus-action >/dev/null 2>&1; then
 fi
 
 printf '[remote "origin"]\n\turl = https://github.com/vana-com/.github\n' >"$test_root/spoof.gitconfig"
+# A poisoned cache must not execute code through its own local config while it
+# is being authenticated: core.fsmonitor runs a command during `git status`.
+fsmonitor_home="$test_root/fsmonitor-home"
+mkdir -p "$fsmonitor_home/vana-secret-scan/policy"
+fsmonitor_cache="$fsmonitor_home/vana-secret-scan/policy/$policy_sha"
+git clone -q "$root" "$fsmonitor_cache"
+git -C "$fsmonitor_cache" remote set-url origin https://github.com/vana-com/.github.git
+git -C "$fsmonitor_cache" checkout -q "$policy_sha"
+printf '#!/bin/sh\ntouch %q\nexit 1\n' "$test_root/fsmonitor-fired" >"$test_root/evil-fsmonitor"
+chmod 0755 "$test_root/evil-fsmonitor"
+git -C "$fsmonitor_cache" config core.fsmonitor "$test_root/evil-fsmonitor"
+XDG_DATA_HOME="$fsmonitor_home" VANA_POLICY_SHA="$policy_sha" "$bootstrap" status >/dev/null 2>&1 || true
+if [[ -e "$test_root/fsmonitor-fired" ]]; then
+  printf 'expected bootstrap to neutralize core.fsmonitor on an unauthenticated cache\n' >&2
+  exit 1
+fi
+
 bootstrap_home="$test_root/bootstrap-home"
 mkdir -p "$bootstrap_home/vana-secret-scan/policy"
 bootstrap_cache="$bootstrap_home/vana-secret-scan/policy/$policy_sha"