#!/usr/bin/env bash
set -uo pipefail

# CASAN Plan-16 SEC-02 (H-02) — no local key auto-generation in enforced mode.
#
# The tamper-evidence of the audit chain rests on the head signature. If the
# signer auto-generates a private key next to the data (as dev convenience does),
# then any actor who can write the log can also mint a key and re-sign a forged
# head. In enforced mode the signer must NOT auto-generate — the key is provisioned
# out-of-band (KMS/HSM). This proves:
#   * permissive mode still auto-generates a local key (dev convenience),
#   * enforced mode does NOT create a key when none is provisioned, and the
#     resulting unsigned head then FAILS strict verification (fail-closed).
#
# Deterministic; hermetic (temp key dir + backup/restore of audit + gov dirs).

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "$SCRIPT_DIR/../scripts/bash/casan-paths.sh"
PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
BASH_DIR="$CASAN_HARNESS_ROOT/scripts/bash"
WORK="$(mktemp -d)"

BK="$WORK/bak"; mkdir -p "$BK"
cp -a "$CASAN_STATE_ROOT/logs/audit" "$BK/audit" 2>/dev/null || true
cp -a "$CASAN_GOVERNANCE_ROOT" "$BK/cg" 2>/dev/null || true
restore() {
  rm -rf "$CASAN_STATE_ROOT/logs/audit"; cp -a "$BK/audit" "$CASAN_STATE_ROOT/logs/audit" 2>/dev/null || true
  rm -rf "$CASAN_GOVERNANCE_ROOT"; cp -a "$BK/cg" "$CASAN_GOVERNANCE_ROOT" 2>/dev/null || true
}
trap 'restore; rm -rf "$WORK"' EXIT

PASS=0; FAIL=0
pass() { echo "PASS: $1"; PASS=$((PASS + 1)); }
fail() { echo "FAIL: $1"; FAIL=$((FAIL + 1)); }
rc_of() { set +e; "$@" >/dev/null 2>&1; echo $?; set -e 2>/dev/null || true; }

echo "===== Plan-16 SEC-02: no local key auto-gen in enforced mode ====="
echo "benign input" > "$WORK/in.txt"

# 1) Permissive mode: a fresh key dir auto-generates a local key (dev convenience).
KD1="$WORK/keys-permissive"
env CASAN_AUDIT_KEY_DIR="$KD1" bash "$BASH_DIR/governance-check.sh" "$WORK/in.txt" "$WORK/out1.txt" agent_step >/dev/null 2>&1
[[ -f "$KD1/audit-private.pem" ]] \
  && pass "permissive mode auto-generates a local signing key" \
  || fail "permissive mode did not auto-generate a key (dev convenience broken)"

# 2) Enforced mode: a fresh key dir must NOT auto-generate a key.
KD2="$WORK/keys-enforced"
env CASAN_VERIFY_STRICT=1 CASAN_AUDIT_KEY_DIR="$KD2" bash "$BASH_DIR/governance-check.sh" "$WORK/in.txt" "$WORK/out2.txt" agent_step >/dev/null 2>&1
[[ ! -f "$KD2/audit-private.pem" ]] \
  && pass "enforced mode does NOT auto-generate a local key (H-02 closed)" \
  || fail "enforced mode auto-generated a local key (attacker could re-sign forgery)"

# 3) The unsigned head produced in enforced mode fails strict verification.
[[ "$(rc_of env CASAN_VERIFY_STRICT=1 bash "$BASH_DIR/verify-audit-chain.sh")" -ne 0 ]] \
  && pass "unsigned head from enforced run FAILS strict verify (fail-closed)" \
  || fail "unsigned head passed strict verify"

echo ""
echo "===== SEC-02 SUMMARY: PASS=$PASS FAIL=$FAIL ====="
[[ "$FAIL" -eq 0 ]] || exit 1