<?php
/*
 * Virtum verifier. Checks, offline, anything Virtum signs for customers and the public:
 *   - the release transparency log      (https://virtum.cloud/transparency/log.json)
 *   - a workspace audit export          (JSON, or CSV with its .sig file)
 *   - an isolation report               (JSON)
 *
 * Needs only PHP 7.2+ with the sodium extension (bundled with PHP). No network, no Virtum code.
 *
 *   php verify.php log   log.json [--key <base64 public key>]
 *   php verify.php json  export.json --key <base64 public key>
 *   php verify.php file  export.csv export.csv.sig --key <base64 public key>   (also for a report PDF and its .sig)
 *
 * Get the public key from https://virtum.cloud/transparency/key (compare it with the one in the signed
 * security.txt and the one you recorded when you first onboarded). Without --key the check still runs but the
 * result is "UNPINNED": a forger can sign with their own key, so a pinned key is what makes a pass meaningful.
 *
 * Exit status: 0 verified and pinned, 1 verification failed, 2 usage error, 3 verified but the key was not pinned.
 */

const GENESIS = '0000000000000000000000000000000000000000000000000000000000000000';

function fail(string $m, int $code = 1): void { fwrite(STDERR, $m."\n"); exit($code); }
function ok(string $m): void { echo $m."\n"; }

function canonical($v): string {
    $sort = function ($x) use (&$sort) {
        if (!is_array($x)) return $x;
        $isList = array_keys($x) === range(0, count($x) - 1);
        if ($isList) return array_map($sort, $x);
        ksort($x, SORT_STRING);
        return array_map($sort, $x);
    };
    return json_encode($sort($v), JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
}

function sigok(string $msg, string $sigB64, string $keyB64): bool {
    $s = base64_decode($sigB64, true); $k = base64_decode($keyB64, true);
    return $s !== false && $k !== false && strlen($s) === SODIUM_CRYPTO_SIGN_BYTES && strlen($k) === SODIUM_CRYPTO_SIGN_PUBLICKEYBYTES
        && sodium_crypto_sign_verify_detached($s, $msg, $k);
}

function entryHash(array $e): string {
    return hash('sha256', implode("\n", ['virtum-transparency-v1', $e['sequence'], $e['kind'], $e['component'], $e['version'],
        $e['image_digest'] ?? '', $e['signature_ref'] ?? '', $e['sbom_ref'] ?? '', $e['released_at'], $e['prev_hash']]));
}

function loadJson(string $path): array {
    $raw = @file_get_contents($path);
    $d = $raw === false ? null : json_decode($raw, true);
    if (!is_array($d)) fail("Cannot read $path as JSON.", 2);
    return $d;
}

function pinned(array $argv): ?string {
    $i = array_search('--key', $argv, true);
    return $i === false ? null : ($argv[$i + 1] ?? null);
}

function finish(array $problems, string $what, bool $isPinned): void {
    if ($problems) { foreach ($problems as $p) fwrite(STDERR, "  - $p\n"); fail("FAILED: $what does not verify.", 1); }
    if (!$isPinned) { ok("VERIFIED but UNPINNED: $what is internally consistent. Re-run with --key <public key from https://virtum.cloud/transparency/key> to make this meaningful."); exit(3); }
    ok("VERIFIED: $what");
    exit(0);
}

if (!function_exists('sodium_crypto_sign_verify_detached')) fail('The sodium extension is required.', 2);
$mode = $argv[1] ?? '';
$file = $argv[2] ?? '';
$pin = pinned($argv);
if ($file === '') fail("Usage: php verify.php log|json|file <file> [<file.sig>] [--key <base64 public key>]", 2);

if ($mode === 'log') {
    $feed = loadJson($file);
    $keys = [];
    foreach ($feed['public_keys'] ?? [] as $k) $keys[$k['key_id']] = $k['public_key'];
    $problems = []; $prev = GENESIS; $exp = 1; $by = [];
    foreach ($feed['entries'] ?? [] as $e) {
        $n = (int) $e['sequence'];
        if ($n !== $exp) { $problems[] = "entry $n: expected sequence $exp (an entry is missing or reordered)"; $exp = $n; }
        if (!hash_equals($prev, $e['prev_hash'])) $problems[] = "entry $n: does not link to the entry before it";
        if (!hash_equals(entryHash($e), $e['entry_hash'])) $problems[] = "entry $n: hash does not match contents (edited)";
        $key = $keys[$e['key_id']] ?? null;
        if ($key === null || !sigok($e['entry_hash'], $e['signature'], $key)) $problems[] = "entry $n: signature does not verify against the key";
        $by[$n] = $e; $prev = $e['entry_hash']; $exp = $n + 1;
    }
    foreach ($by as $n => $e) if ($e['kind'] === 'anchor_checkpoint') {
        $t = $by[(int) $e['version']] ?? null;
        if ($t === null || $e['image_digest'] !== 'sha256:'.$t['entry_hash']) $problems[] = "entry $n: checkpoint does not match the entry it records";
    }
    if ($pin !== null && !in_array($pin, array_column($feed['public_keys'] ?? [], 'public_key'), true)) $problems[] = 'the pinned key is not among the feed\'s keys';
    finish($problems, count($by).' log entries, hash chain and signatures', $pin !== null);
}

if ($mode === 'json') {
    $doc = loadJson($file);
    $sig = $doc['signature'] ?? null;
    unset($doc['signature']);
    $problems = [];
    if (!is_array($sig) || ($sig['algorithm'] ?? '') !== 'ed25519') fail('No ed25519 signature block.', 1);
    if ($pin !== null && !hash_equals($pin, $sig['public_key'])) $problems[] = 'signed with a key other than the pinned one';
    if (!sigok(canonical($doc), $sig['value'], $sig['public_key'])) $problems[] = 'signature does not match the document (edited, or not signed by that key)';
    if (($doc['format'] ?? '') === 'virtum-audit-export-v1') {
        $prev = null;
        foreach ($doc['entries'] ?? [] as $i => $e) {
            if ($prev !== null && $e['sequence'] === $prev['sequence'] + 1 && !hash_equals($prev['entry_hash'], $e['prev_hash'])) $problems[] = "entry {$e['sequence']}: does not link to the entry before it";
            $prev = $e;
        }
        $last = end($doc['entries']) ?: null;
        if ($last && ($doc['chain']['head_sequence'] ?? null) !== $last['sequence']) $problems[] = 'chain head does not match the last entry';
        if (!empty($doc['anchor'])) foreach ($doc['entries'] as $e) if ($e['sequence'] === $doc['anchor']['sequence'] && !hash_equals($e['entry_hash'], $doc['anchor']['head_hash'])) $problems[] = 'anchored hash differs from the exported entry at that sequence';
    }
    finish($problems, ($doc['format'] ?? 'document').' (signature'.(($doc['format'] ?? '') === 'virtum-audit-export-v1' ? ', chain links, anchor' : '').')', $pin !== null);
}

if ($mode === 'csv' || $mode === 'file') {
    $sigFile = $argv[3] ?? '';
    $sig = loadJson($sigFile);
    $bytes = @file_get_contents($file);
    if ($bytes === false) fail("Cannot read $file.", 2);
    $problems = [];
    if (!hash_equals($sig['sha256'] ?? '', hash('sha256', $bytes))) $problems[] = 'the CSV does not match the hash that was signed (edited)';
    if ($pin !== null && !hash_equals($pin, $sig['public_key'])) $problems[] = 'signed with a key other than the pinned one';
    if (!sigok('virtum-file-v1'."\n".($sig['sha256'] ?? '')."\n".($sig['workspace_id'] ?? '')."\n".($sig['generated_at'] ?? ''), $sig['value'] ?? '', $sig['public_key'] ?? '')) $problems[] = 'signature does not verify';
    finish($problems, 'file (hash and signature)', $pin !== null);
}

fail('Mode must be log, json or file.', 2);