<?php
namespace Zotlabs\Web;
/**
* Implements HTTP Signatures per draft-cavage-http-signatures-07
*/
class HTTPSig {
// See RFC5843
static function generate_digest($body,$set = true) {
$digest = base64_encode(hash('sha256',$body,true));
if($set) {
header('Digest: SHA-256=' . $digest);
}
return $digest;
}
// See draft-cavage-http-signatures-07
static function verify($data,$key = '') {
$body = $data;
$headers = null;
$spoofable = false;
$result = [
'signer' => '',
'header_signed' => false,
'header_valid' => false,
'content_signed' => false,
'content_valid' => false
];
// decide if $data arrived via controller submission or curl
if(is_array($data) && $data['header']) {
if(! $data['success'])
return $result;
$h = new \Zotlabs\Web\HTTPHeaders($data['header']);
$headers = $h->fetcharr();
$body = $data['body'];
}
else {
$headers = [];
$headers['(request-target)'] =
$_SERVER['REQUEST_METHOD'] . ' ' .
$_SERVER['REQUEST_URI'];
foreach($_SERVER as $k => $v) {
if(strpos($k,'HTTP_') === 0) {
$field = str_replace('_','-',strtolower(substr($k,5)));
$headers[$field] = $v;
}
}
}
$sig_block = null;
if(array_key_exists('signature',$headers)) {
$sig_block = self::parse_sigheader($headers['signature']);
}
elseif(array_key_exists('authorization',$headers)) {
$sig_block = self::parse_sigheader($headers['authorization']);
}
if(! $sig_block)
return $result;
$result['header_signed'] = true;
$signed_headers = $sig_block['headers'];
if(! $signed_headers)
$signed_headers = [ 'date' ];
$signed_data = '';
foreach($signed_headers as $h) {
if(array_key_exists($h,$headers)) {
$signed_data .= $h . ': ' . $headers[$h] . "\n";
}
if(strpos($h,'.')) {
$spoofable = true;
}
}
$signed_data = rtrim($signed_data,"\n");
$algorithm = null;
if($sig_block['algorithm'] === 'rsa-sha256') {
$algorithm = 'sha256';
}
if($sig_block['algorithm'] === 'rsa-sha512') {
$algorithm = 'sha512';
}
if(! $key) {
$result['signer'] = $sig_block['keyId'];
$key = self::get_activitypub_key($sig_block['keyId']);
}
if(! $key)
return null;
$x = rsa_verify($signed_data,$sig_block['signature'],$key,$algorithm);
if($x === false)
return $result;
if(! $spoofable)
$result['header_valid'] = true;
if(in_array('digest',$signed_headers)) {
$result['content_signed'] = true;
$digest = explode('=', $headers['digest']);
if($digest[0] === 'SHA-256')
$hashalg = 'sha256';
if($digest[0] === 'SHA-512')
$hashalg = 'sha512';
// The explode operation will have stripped the '=' padding, so compare against unpadded base64
if(rtrim(base64_encode(hash($hashalg,$body,true)),'=') === $digest[1]) {
$result['content_valid'] = true;
}
}
return $result;
}
function get_activitypub_key($id) {
if(strpos($id,'acct:') === 0) {
$x = q("select xchan_pubkey from xchan left join hubloc on xchan_hash = hubloc_hash where hubloc_addr = '%s' limit 1",
dbesc(str_replace('acct:','',$id))
);
}
else {
$x = q("select xchan_pubkey from xchan where xchan_hash = '%s' and xchan_network = 'activitypub' ",
dbesc($id)
);
}
if($x && $x[0]['xchan_pubkey']) {
return ($x[0]['xchan_pubkey']);
}
$r = as_fetch($id);
if($r) {
$j = json_decode($r,true);
if($j['id'] !== $id)
return false;
if(array_key_exists('publicKey',$j) && array_key_exists('publicKeyPem',$j['publicKey'])) {
return($j['publicKey']['publicKeyPem']);
}
}
return false;
}
static function create_sig($request,$head,$prvkey,$keyid = 'Key',$send_headers = false,$auth = false,$alg = 'sha256') {
$return_headers = [];
if($alg === 'sha256') {
$algorithm = 'rsa-sha256';
}
if($alg === 'sha512') {
$algorithm = 'rsa-sha512';
}
$x = self::sign($request,$head,$prvkey,$alg);
if($auth) {
$sighead = 'Authorization: Signature keyId="' . $keyid . '",algorithm="' . $algorithm
. '",headers="' . $x['headers'] . '",signature="' . $x['signature'] . '"';
}
else {
$sighead = 'Signature: keyId="' . $keyid . '",algorithm="' . $algorithm
. '",headers="' . $x['headers'] . '",signature="' . $x['signature'] . '"';
}
if($head) {
foreach($head as $k => $v) {
if($send_headers) {
header($k . ': ' . $v);
}
else {
$return_headers[] = $k . ': ' . $v;
}
}
}
if($send_headers) {
header($sighead);
}
else {
$return_headers[] = $sighead;
}
return $return_headers;
}
static function sign($request,$head,$prvkey,$alg = 'sha256') {
$ret = [];
$headers = '';
$fields = '';
if($request) {
$headers = '(request-target)' . ': ' . trim($request) . "\n";
$fields = '(request-target)';
}
if(head) {
foreach($head as $k => $v) {
$headers .= strtolower($k) . ': ' . trim($v) . "\n";
if($fields)
$fields .= ' ';
$fields .= strtolower($k);
}
// strip the trailing linefeed
$headers = rtrim($headers,"\n");
}
$sig = base64_encode(rsa_sign($headers,$prvkey,$alg));
$ret['headers'] = $fields;
$ret['signature'] = $sig;
return $ret;
}
static function parse_sigheader($header) {
$ret = [];
$matches = [];
if(preg_match('/keyId="(.*?)"/ism',$header,$matches))
$ret['keyId'] = $matches[1];
if(preg_match('/algorithm="(.*?)"/ism',$header,$matches))
$ret['algorithm'] = $matches[1];
if(preg_match('/headers="(.*?)"/ism',$header,$matches))
$ret['headers'] = explode(' ', $matches[1]);
if(preg_match('/signature="(.*?)"/ism',$header,$matches))
$ret['signature'] = base64_decode(preg_replace('/\s+/','',$matches[1]));
if(($ret['signature']) && ($ret['algorithm']) && (! $ret['headers']))
$ret['headers'] = [ 'date' ];
return $ret;
}
}