findings X-1: pin every dependency tarball fetch to a SHA256 and enforce it

security-audit-v3 #15. download_file already had a verify branch; no caller
used it and every *_SHA256 in versions.sh was a commented placeholder, so a
tampered mirror tarball flowed straight into configure/make and the shipped
WASM.

- versions.sh: 13 pins (cross-checked against Homebrew/Buildroot/nixpkgs/
  FreeBSD/vcpkg/boost.org/curl PGP; glm .zip is TOFU), boost/curl/libgit2
  versions moved beside their pins.
- all 13 download_file call sites pass "${NAME_SHA256}".
- download_file refuses an empty or malformed pin (PCBJAM_ALLOW_UNPINNED=1
  to bootstrap a new dep); file_sha256 prefers sha256sum, falls back to shasum.
- scripts/deps/check-pins.sh: static 3-arg check + offline file:// enforcement
  test; runs in wasm-build.yml before the deps cache, on cache hits too.

Expect one cold --build-deps run: the deps-cache key hashes versions.sh.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GcsgJZ77bhZatLAVU8R84H

scripts/deps/check-pins.sh

@@ -0,0 +1,82 @@
+#!/bin/bash
+# Oracle for X-1 (security-audit-v3 #15): every dependency tarball fetch is
+# pinned to a SHA256, and download_file actually enforces the pin.
+#
+#  1. static  — every download_file call in scripts/deps/*.sh passes a third
+#               argument that resolves to a 64-hex value from versions.sh.
+#  2. dynamic — download_file against a file:// URL (fully offline): a wrong
+#               pin fails and removes the file, the right pin succeeds, and an
+#               empty pin is refused unless PCBJAM_ALLOW_UNPINNED=1.
+#
+# Runs in seconds with no docker; wired into wasm-build.yml before the deps
+# step and usable locally: scripts/deps/check-pins.sh
+set -u
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../common/versions.sh"
+source "${SCRIPT_DIR}/../common/functions.sh"
+
+fail=0
+ok()   { echo "  ok   $*"; }
+bad()  { echo "  FAIL $*"; fail=1; }
+
+echo "[check-pins] static: download_file call sites"
+while IFS= read -r line; do
+    file="${line%%:*}"; rest="${line#*:}"; lineno="${rest%%:*}"; call="${rest#*:}"
+    # third argument must be a "${NAME_SHA256}" reference
+    if [[ "$call" =~ download_file[[:space:]]+\"[^\"]*\"[[:space:]]+\"[^\"]*\"[[:space:]]+\"\$\{([A-Z0-9_]+_SHA256)\}\" ]]; then
+        var="${BASH_REMATCH[1]}"
+        val="${!var:-}"
+        if printf '%s' "$val" | grep -Eq '^[0-9a-f]{64}$'; then
+            ok "$(basename "$file"):$lineno -> $var"
+        else
+            bad "$(basename "$file"):$lineno -> $var is not a 64-hex pin in versions.sh ('$val')"
+        fi
+    else
+        bad "$(basename "$file"):$lineno has no \"\${NAME_SHA256}\" third argument: $call"
+    fi
+done < <(grep -n '^[[:space:]]*download_file ' "${SCRIPT_DIR}"/build-*.sh)
+
+echo "[check-pins] dynamic: download_file enforces the pin (file:// URL)"
+tmp="$(mktemp -d)"
+trap 'rm -rf "$tmp"' EXIT
+printf 'pcbjam pin oracle\n' > "$tmp/src.txt"
+tar -czf "$tmp/src.tar.gz" -C "$tmp" src.txt
+good="$(file_sha256 "$tmp/src.tar.gz")"
+wrong="$(printf '%064d' 1)"
+url="file://$tmp/src.tar.gz"
+
+if download_file "$url" "$tmp/d1.tar.gz" "$wrong" >/dev/null 2>&1; then
+    bad "wrong pin was accepted"
+elif [ -e "$tmp/d1.tar.gz" ]; then
+    bad "wrong pin: mismatched file left on disk"
+else
+    ok "wrong pin rejected and file removed"
+fi
+
+if download_file "$url" "$tmp/d2.tar.gz" "$good" >/dev/null 2>&1 && [ -f "$tmp/d2.tar.gz" ]; then
+    ok "right pin accepted"
+else
+    bad "right pin rejected"
+fi
+
+if PCBJAM_ALLOW_UNPINNED=0 download_file "$url" "$tmp/d3.tar.gz" >/dev/null 2>&1; then
+    bad "empty pin accepted without PCBJAM_ALLOW_UNPINNED=1"
+else
+    ok "empty pin refused"
+fi
+
+if PCBJAM_ALLOW_UNPINNED=1 download_file "$url" "$tmp/d4.tar.gz" >/dev/null 2>&1; then
+    ok "empty pin allowed with PCBJAM_ALLOW_UNPINNED=1 (bootstrap)"
+else
+    bad "bootstrap escape hatch broken"
+fi
+
+if download_file "$url" "$tmp/d5.tar.gz" "not-a-hash" >/dev/null 2>&1; then
+    bad "malformed pin accepted"
+else
+    ok "malformed pin refused"
+fi
+
+if [ $fail -ne 0 ]; then echo "[check-pins] FAILED"; exit 1; fi
+echo "[check-pins] all good"