CASAN/packages/casan-harness/scripts/bash/evidence-pack.sh

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

# CASAN Plan-09 — Evidence Pack (MVP).
#
# Packages a tamper-evident proof of a CASAN run: per-harness JSON reports, a
# red-team / benign-FP result, an artifact manifest (sha256 of every file), a
# human decision log, and an RSA signature over the manifest head. Verification
# fails if any packed file changes.
#
# CLI mapping (future `casan` binary):
#   casan pack        <run-id>   ->  evidence-pack.sh pack        <run-id>
#   casan verify-pack <run-id>   ->  evidence-pack.sh verify-pack <run-id>
#
# A "Certified run" is only asserted when the required gates PASS and none was
# silently skipped (see run-summary.json.certification_reasons).
#
# Usage:
#   evidence-pack.sh pack <run-id> [--out <dir>]
#   evidence-pack.sh verify-pack <run-id> [--dir <dir>]
# Exit: 0 ok, 1 verify failed, 64 usage.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
source "$SCRIPT_DIR/casan-paths.sh"
PROJECT_ROOT="$CASAN_APP_ROOT"
# shellcheck source=casan-log.sh
source "$SCRIPT_DIR/casan-log.sh"

CMD="${1:-}"; RUN_ID="${2:-}"
shift 2 2>/dev/null || true
PACKS_ROOT="$PROJECT_ROOT/docs/output/casan/evidence-packs"
PACK_DIR=""
while [[ "$#" -gt 0 ]]; do
  case "$1" in
    --out|--dir) PACK_DIR="${2:-}"; shift 2 ;;
    *) shift ;;
  esac
done
[[ -z "$CMD" || -z "$RUN_ID" ]] && { echo "Usage: evidence-pack.sh {pack|verify-pack} <run-id> [--out/--dir <dir>]" >&2; exit 64; }
[[ -z "$PACK_DIR" ]] && PACK_DIR="$PACKS_ROOT/$RUN_ID"

AUDIT_PRIV="${CASAN_AUDIT_PRIV:-$CASAN_GOVERNANCE_ROOT/audit-private.pem}"
AUDIT_PUB="${CASAN_AUDIT_PUB:-$CASAN_GOVERNANCE_ROOT/audit-public.pem}"

run_status() { # <command...> -> prints "<first-stdout-line>|<rc>"
  local out rc
  out="$("$@" 2>/dev/null | head -1)"; rc="${PIPESTATUS[0]}"
  printf '%s|%s' "${out:-none}" "$rc"
}

case "$CMD" in
  pack)
    mkdir -p "$PACK_DIR"
    casan_log info evidence-pack "packing run=$RUN_ID dir=$PACK_DIR"

    AUDIT_ST="$(run_status bash "$SCRIPT_DIR/verify-audit-chain.sh")"
    TOOL_ST="$(run_status bash "$SCRIPT_DIR/verify-tool-audit.sh")"
    TEL_ST="$(run_status bash "$SCRIPT_DIR/telemetry-integrity.sh" verify)"
    COST_RC=0; bash "$SCRIPT_DIR/cost-spike-detect.sh" >/dev/null 2>&1 || COST_RC=$?

    # Reuse an existing benign-FP report if present (fast); else leave unset so
    # the certification records the gate as skipped rather than fabricating it.
    FP_JSON="$PROJECT_ROOT/docs/output/casan/benign-fp-report.json"
    [[ -f "$FP_JSON" ]] || FP_JSON=""

    CERT_LINE="$(CASAN_EP_AUDIT="$AUDIT_ST" CASAN_EP_TOOLAUDIT="$TOOL_ST" \
      CASAN_EP_TELEMETRY="$TEL_ST" CASAN_EP_COST_RC="$COST_RC" CASAN_EP_FP_JSON="$FP_JSON" \
      python "$SCRIPT_DIR/evidence-pack-build.py" "$PROJECT_ROOT" "$RUN_ID" "$PACK_DIR")"

    # Safety: the human decision log must not leak secrets/PII (fail closed).
    if ! bash "$SCRIPT_DIR/data-exfil-guard.sh" "$PACK_DIR/decision-log.md" artifact >/dev/null 2>&1; then
      casan_log error evidence-pack "decision-log failed data-exfil guard — pack aborted"
      echo "EVIDENCE_PACK_ABORTED reason=decision_log_would_leak" >&2
      exit 1
    fi

    # Sign the manifest head (off-repo key in production; unsigned in keyless dev).
    HEAD_FILE="$PACK_DIR/manifest-head.txt"
    SIG_FILE="$PACK_DIR/evidence-pack.sig"
    if [[ -f "$AUDIT_PRIV" ]] && command -v openssl >/dev/null 2>&1; then
      openssl dgst -sha256 -sign "$AUDIT_PRIV" -out "$SIG_FILE" "$HEAD_FILE"
      ANCHOR="signed"
    else
      rm -f "$SIG_FILE"; ANCHOR="unsigned"
    fi

    CERTIFIED="${CERT_LINE#CERTIFIED|}"; CERTIFIED="${CERTIFIED%%|*}"
    echo "EVIDENCE_PACK_CREATED run=$RUN_ID dir=$PACK_DIR certified=$CERTIFIED anchor=$ANCHOR"
    [[ "$CERTIFIED" == "true" ]] && echo "CASAN_CERTIFIED_RUN run=$RUN_ID" || echo "CASAN_UNCERTIFIED_RUN run=$RUN_ID reason=${CERT_LINE##*|}"
    ;;

  verify-pack)
    [[ -d "$PACK_DIR" ]] || { echo "EVIDENCE_PACK_NOT_FOUND dir=$PACK_DIR" >&2; exit 1; }
    python "$SCRIPT_DIR/evidence-pack-verify.py" "$PACK_DIR"; VRC=$?
    [[ "$VRC" -ne 0 ]] && exit 1
    # Signature check over the manifest head (catches a manifest rewrite).
    HEAD_FILE="$PACK_DIR/manifest-head.txt"
    SIG_FILE="$PACK_DIR/evidence-pack.sig"
    if [[ -f "$SIG_FILE" && -f "$AUDIT_PUB" ]] && command -v openssl >/dev/null 2>&1; then
      if openssl dgst -sha256 -verify "$AUDIT_PUB" -signature "$SIG_FILE" "$HEAD_FILE" >/dev/null 2>&1; then
        echo "EVIDENCE_PACK_VALID anchor=signed dir=$PACK_DIR"
      else
        echo "EVIDENCE_PACK_SIGNATURE_INVALID dir=$PACK_DIR" >&2
        exit 1
      fi
    else
      # SEC-01 (H-01): enforced mode treats a missing/unverifiable pack signature
      # as FAIL, otherwise deleting evidence-pack.sig after editing packed files
      # would still verify as a "valid unsigned" pack.
      if [[ "${CASAN_PROFILE:-}" == "prod" || "${CASAN_VERIFY_STRICT:-}" == "1" ]]; then
        MISSING=""
        [[ -f "$SIG_FILE" ]] || MISSING="$MISSING pack-sig"
        [[ -f "$AUDIT_PUB" ]] || MISSING="$MISSING pubkey"
        command -v openssl >/dev/null 2>&1 || MISSING="$MISSING openssl"
        echo "EVIDENCE_PACK_UNSIGNED_STRICT_FAIL dir=$PACK_DIR missing=${MISSING# }" >&2
        exit 1
      fi
      echo "EVIDENCE_PACK_VALID anchor=unsigned dir=$PACK_DIR"
    fi
    ;;

  *)
    echo "Usage: evidence-pack.sh {pack|verify-pack} <run-id> [--out/--dir <dir>]" >&2
    exit 64 ;;
esac