WIP: Paused over-hardening fix wave (boot checkout verification, double-read package manifest)

boot

@@ -45,6 +45,65 @@ checkout_command() {
   fi
 }
 
+# Git's index hints are performance promises, not trust evidence. In
+# particular, assume-unchanged and skip-worktree can make porcelain status
+# report a clean checkout whose files no longer match HEAD. Compare every
+# tracked blob and Git mode with the verified commit before handing control to
+# any file in the worktree.
+checkout_matches_verified_commit() (
+  local checkout="$1" listing="" entry metadata mode type expected path actual
+  local link_target_with_sentinel link_target
+
+  trap '[[ -z "$listing" ]] || rm -f -- "$listing"' EXIT
+  trap 'exit 130' INT
+  trap 'exit 143' TERM
+  listing="$(mktemp -u -t panama-boot-tree.XXXXXX)" || exit 1
+  umask 077
+  if ! (set -o noclobber; : >"$listing") 2>/dev/null; then
+    listing=""
+    exit 1
+  fi
+
+  checkout_command git -C "$checkout" ls-tree -rz --full-tree \
+    "$PANAMA_BOOT_REVISION" >"$listing" || exit 1
+  while IFS= read -r -d '' entry; do
+    [[ "$entry" == *$'\t'* ]] || exit 1
+    metadata="${entry%%$'\t'*}"
+    path="${entry#*$'\t'}"
+    read -r mode type expected <<<"$metadata"
+    [[ "$type" == blob && -n "$path" && "$path" != /* ]] || exit 1
+
+    case "$mode" in
+      100644) [[ -f "$checkout/$path" && ! -L "$checkout/$path" \
+        && ! -x "$checkout/$path" ]] || exit 1 ;;
+      100755) [[ -f "$checkout/$path" && ! -L "$checkout/$path" \
+        && -x "$checkout/$path" ]] || exit 1 ;;
+      120000)
+        [[ -L "$checkout/$path" ]] || exit 1
+        # hash-object given a pathname follows a symlink. Git's 120000 blob is
+        # the link text itself, including any trailing newlines, so preserve
+        # those bytes with a sentinel and hash stdin instead.
+        link_target_with_sentinel="$(
+          readlink -n -- "$checkout/$path" && printf .
+        )" || exit 1
+        [[ "$link_target_with_sentinel" == *. ]] || exit 1
+        link_target="${link_target_with_sentinel%.}"
+        actual="$(
+          printf '%s' "$link_target" \
+            | checkout_command git -C "$checkout" hash-object --stdin
+        )" || exit 1
+        [[ "$actual" == "$expected" ]] || exit 1
+        continue
+        ;;
+      *) exit 1 ;;
+    esac
+
+    actual="$(checkout_command git -C "$checkout" hash-object --no-filters -- "$path")" \
+      || exit 1
+    [[ "$actual" == "$expected" ]] || exit 1
+  done <"$listing"
+)
+
 prepare_panama_checkout() {
   local checkout="$1" actual_head checkout_status
 
@@ -110,6 +169,30 @@ for arg in "$@"; do
   esac
 done
 
+# Keep the worktree comparison at the last possible boundary. Checkout
+# preparation may invoke several commands and return to the caller; performing
+# the byte/mode/link check here ensures a change in that interval is rejected
+# before any tracked file is executed.
+verified_install_handoff() {
+  local use_tty="$1"
+  if ! checkout_matches_verified_commit "$PANAMA_PATH"; then
+    echo "boot: checkout files do not match PANAMA_BOOT_REVISION" >&2
+    return 1
+  fi
+  if [[ -n "$BOOTSTRAP_USER" ]]; then
+    if (( use_tty )); then
+      exec runuser -u "$BOOTSTRAP_USER" -- env PANAMA_PATH="$PANAMA_PATH" \
+        "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"} </dev/tty
+    fi
+    exec runuser -u "$BOOTSTRAP_USER" -- env PANAMA_PATH="$PANAMA_PATH" \
+      "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"}
+  fi
+  if (( use_tty )); then
+    exec "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"} </dev/tty
+  fi
+  exec "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"}
+}
+
 # The public bootstrap contract runs this branch as an ordinary user with a
 # stubbed root identity. Keep its filesystem adapter unavailable to a real root
 # shell so it cannot redirect a real installation by accident.
@@ -471,7 +554,7 @@ if [[ "$(id -u)" -eq 0 ]]; then
 
   if ! command -v git >/dev/null 2>&1; then
     echo "Installing git, which the clone needs"
-    dnf install -y git
+    dnf install -y --repo=fedora --repo=updates --from-repo=fedora,updates git
   fi
 
   # Create or advance the checkout as the target user. A root-owned .git in a
@@ -481,15 +564,14 @@ if [[ "$(id -u)" -eq 0 ]]; then
   prepare_panama_checkout "$PANAMA_PATH"
 
   echo "Handing off to install as $username"
-  exec runuser -u "$username" -- env PANAMA_PATH="$PANAMA_PATH" \
-    "$PANAMA_PATH/install" --server </dev/tty
+  verified_install_handoff 1
 fi
 
 # git is the one dependency the clone itself needs. Everything else -- gum
 # included -- is bootstrapped by `install`.
 if ! command -v git >/dev/null 2>&1; then
   echo "Installing git, which the clone needs"
-  sudo dnf install -y git
+  sudo dnf install -y --repo=fedora --repo=updates --from-repo=fedora,updates git
 fi
 
 prepare_panama_checkout "$PANAMA_PATH"
@@ -500,7 +582,8 @@ prepare_panama_checkout "$PANAMA_PATH"
 # so itself.
 # The probe actually opens /dev/tty rather than testing -r: a process with no
 # controlling terminal passes -r and then fails the redirect.
+handoff_tty=0
 if [[ ! -t 0 ]] && (exec </dev/tty) 2>/dev/null; then
-  exec "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"} </dev/tty
+  handoff_tty=1
 fi
-exec "$PANAMA_PATH/install" ${INSTALL_ARGS[@]+"${INSTALL_ARGS[@]}"}
+verified_install_handoff "$handoff_tty"