(detection and prevention of weak keys for CAcert-issued certificates)
This commit is contained in:
Wytze van der Raay
parent
bd0a4c0023
commit
8571e6f0a9
2 changed files with 498 additions and 16 deletions
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@ -299,6 +299,15 @@
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$_SESSION['_config']['rootcert'] = 1;
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$emails .= "SPKAC = $spkac";
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if (($weakKey = checkWeakKeySPKAC($emails)) !== "")
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{
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$id = 4;
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$query = "insert into emailcerts set
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`CN`='$defaultemail',
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`keytype`='NS',
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@ -330,6 +339,16 @@
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} else if($_REQUEST['keytype'] == "MS" || $_REQUEST['keytype'] == "VI") {
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if($csr == "")
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$csr = "-----BEGIN CERTIFICATE REQUEST-----\n".clean_csr($_REQUEST['CSR'])."\n-----END CERTIFICATE REQUEST-----\n";
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if (($weakKey = checkWeakKeyCSR($csr)) !== "")
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{
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$id = 4;
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$tmpfname = tempnam("/tmp", "id4CSR");
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$fp = fopen($tmpfname, "w");
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fputs($fp, $csr);
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@ -613,17 +632,23 @@
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if($process != "" && $oldid == 10)
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{
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$CSR = clean_csr($_REQUEST['CSR']);
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$_SESSION['_config']['tmpfname'] = tempnam("/tmp", "id10CSR");
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$fp = fopen($_SESSION['_config']['tmpfname'], "w");
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if(strpos($CSR,"---BEGIN")===FALSE)
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{
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// In case the CSR is missing the ---BEGIN lines, add them automatically:
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fputs($fp,"-----BEGIN CERTIFICATE REQUEST-----\n".$CSR."\n-----END CERTIFICATE REQUEST-----\n");
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$CSR = "-----BEGIN CERTIFICATE REQUEST-----\n".$CSR."\n-----END CERTIFICATE REQUEST-----\n";
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}
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else
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if (($weakKey = checkWeakKeyCSR($CSR)) !== "")
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{
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fputs($fp, $CSR);
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$_SESSION['_config']['tmpfname'] = tempnam("/tmp", "id10CSR");
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$fp = fopen($_SESSION['_config']['tmpfname'], "w");
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fputs($fp, $CSR);
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fclose($fp);
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$CSR = $_SESSION['_config']['tmpfname'];
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$_SESSION['_config']['subject'] = trim(`/usr/bin/openssl req -text -noout -in "$CSR"|tr -d "\\0"|grep "Subject:"`);
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@ -658,6 +683,23 @@
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if($process != "" && $oldid == 11)
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{
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if(!file_exists($_SESSION['_config']['tmpfname']))
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{
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showheader(_("My CAcert.org Account!"));
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printf(_("Your certificate request has failed to be processed correctly, see %sthe WIKI page%s for reasons and solutions."), "<a href='http://wiki.cacert.org/wiki/FAQ/CertificateRenewal'>", "</a>");
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showfooter();
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exit;
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}
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if (($weakKey = checkWeakKeyCSR(file_get_contents(
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$_SESSION['_config']['tmpfname']))) !== "")
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{
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$id = 11;
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if($_SESSION['_config']['0.CN'] == "" && $_SESSION['_config']['0.subjectAltName'] == "")
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{
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@ -731,13 +773,6 @@
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mysql_query("insert into `domlink` set `certid`='$CSRid', `domid`='$dom'");
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$CSRname=generatecertpath("csr","server",$CSRid);
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if(!file_exists($_SESSION['_config']['tmpfname']))
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{
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showheader(_("My CAcert.org Account!"));
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printf(_("Your certificate request has failed to be processed correctly, see %sthe WIKI page%s for reasons and solutions."), "<a href='http://wiki.cacert.org/wiki/FAQ/CertificateRenewal'>", "</a>");
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showfooter();
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exit;
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}
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rename($_SESSION['_config']['tmpfname'], $CSRname);
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chmod($CSRname,0644);
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mysql_query("update `domaincerts` set `CSR_name`='$CSRname' where `id`='$CSRid'");
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@ -780,8 +815,17 @@
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printf(_("Invalid ID '%s' presented, can't do anything with it.")."<br/>\n", $id);
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continue;
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}
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mysql_query("update `domaincerts` set `renewed`='1' where `id`='$id'");
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$row = mysql_fetch_assoc($res);
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if (($weakKey = checkWeakKeyX509(file_get_contents(
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$row['crt_name']))) !== "")
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{
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echo $weakKey, "<br/>\n";
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continue;
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}
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mysql_query("update `domaincerts` set `renewed`='1' where `id`='$id'");
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$query = "insert into `domaincerts` set
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`domid`='".$row['domid']."',
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`CN`='".mysql_real_escape_string($row['CN'])."',
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@ -946,8 +990,17 @@
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printf(_("Invalid ID '%s' presented, can't do anything with it.")."<br>\n", $id);
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continue;
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}
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mysql_query("update `emailcerts` set `renewed`='1' where `id`='$id'");
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$row = mysql_fetch_assoc($res);
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if (($weakKey = checkWeakKeyX509(file_get_contents(
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$row['crt_name']))) !== "")
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{
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echo $weakKey, "<br/>\n";
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continue;
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}
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mysql_query("update `emailcerts` set `renewed`='1' where `id`='$id'");
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$query = "insert into emailcerts set
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`memid`='".$row['memid']."',
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`CN`='".mysql_real_escape_string($row['CN'])."',
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@ -1378,6 +1431,15 @@
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$_SESSION['_config']['rootcert'] = 1;
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$emails .= "SPKAC = $spkac";
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if (($weakKey = checkWeakKeySPKAC($emails)) !== "")
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{
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$id = 17;
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$query = "insert into `orgemailcerts` set
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`CN`='$defaultemail',
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`keytype`='NS',
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@ -1408,6 +1470,16 @@
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mysql_query("update `orgemailcerts` set `csr_name`='$CSRname' where `id`='$emailid'");
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} else if($_REQUEST['keytype'] == "MS" || $_REQUEST['keytype']=="VI") {
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$csr = "-----BEGIN CERTIFICATE REQUEST-----\n".clean_csr($_REQUEST['CSR'])."-----END CERTIFICATE REQUEST-----\n";
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if (($weakKey = checkWeakKeyCSR($csr)) !== "")
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{
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$id = 17;
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$tmpfname = tempnam("/tmp", "id17CSR");
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$fp = fopen($tmpfname, "w");
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fputs($fp, $csr);
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@ -1514,8 +1586,17 @@
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printf(_("Invalid ID '%s' presented, can't do anything with it.")."<br>\n", $id);
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continue;
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}
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mysql_query("update `orgemailcerts` set `renewed`='1' where `id`='$id'");
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$row = mysql_fetch_assoc($res);
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if (($weakKey = checkWeakKeyX509(file_get_contents(
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$row['crt_name']))) !== "")
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{
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echo $weakKey, "<br/>\n";
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continue;
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}
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mysql_query("update `orgemailcerts` set `renewed`='1' where `id`='$id'");
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if($row['revoke'] > 0)
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{
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printf(_("It would seem '%s' has already been revoked. I'll skip this for now.")."<br>\n", $row['CN']);
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@ -1625,6 +1706,16 @@
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if($process != "" && $oldid == 20)
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{
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$CSR = clean_csr($_REQUEST['CSR']);
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if (($weakKey = checkWeakKeyCSR($CSR)) !== "")
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{
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$id = 20;
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$_SESSION['_config']['tmpfname'] = tempnam("/tmp", "id20CSR");
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$fp = fopen($_SESSION['_config']['tmpfname'], "w");
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fputs($fp, $CSR);
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@ -1674,6 +1765,23 @@
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if($process != "" && $oldid == 21)
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{
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$id = 21;
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if(!file_exists($_SESSION['_config']['tmpfname']))
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{
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showheader(_("My CAcert.org Account!"));
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printf(_("Your certificate request has failed to be processed correctly, see %sthe WIKI page%s for reasons and solutions."), "<a href='http://wiki.cacert.org/wiki/FAQ/CertificateRenewal'>", "</a>");
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showfooter();
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exit;
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}
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if (($weakKey = checkWeakKeyCSR(file_get_contents(
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$_SESSION['_config']['tmpfname']))) !== "")
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{
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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if($_SESSION['_config']['0.CN'] == "" && $_SESSION['_config']['0.subjectAltName'] == "")
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{
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@ -1799,8 +1907,17 @@
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printf(_("Invalid ID '%s' presented, can't do anything with it.")."<br>\n", $id);
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continue;
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}
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mysql_query("update `orgdomaincerts` set `renewed`='1' where `id`='$id'");
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$row = mysql_fetch_assoc($res);
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if (($weakKey = checkWeakKeyX509(file_get_contents(
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$row['crt_name']))) !== "")
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{
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echo $weakKey, "<br/>\n";
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continue;
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}
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mysql_query("update `orgdomaincerts` set `renewed`='1' where `id`='$id'");
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if($row['revoke'] > 0)
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{
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printf(_("It would seem '%s' has already been revoked. I'll skip this for now.")."<br>\n", $row['CN']);
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@ -2497,6 +2614,14 @@
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showfooter();
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exit;
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}
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if (($weakKey = checkWeakKeyCSR($CSR)) !== "")
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{
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showheader(_("My CAcert.org Account!"));
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echo $weakKey;
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showfooter();
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exit;
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}
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$query = "insert into `domaincerts` set
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`CN`='".$_SESSION['_config']['0.CN']."',
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@ -284,4 +284,361 @@ function hideall() {
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</body>
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</html><?
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}
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/**
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* Produces a log entry with the error message with log level E_USER_WARN
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* and a random ID an returns a message that can be displayed to the user
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* including the generated ID
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*
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* @param $errormessage string
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* The error message that should be logged
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* @return string containing the generated ID that can be displayed to the
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* user
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*/
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function failWithId($errormessage) {
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$errorId = rand();
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trigger_error("$errormessage. ID: $errorId", E_USER_WARNING);
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return sprintf(_("Something went wrong when processing your request. ".
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"Please contact %s for help and provide them with the ".
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"following ID: %d"),
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"<a href='mailto:support@cacert.org?subject=System%20Error%20-%20".
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"ID%3A%20$errorId'>support@cacert.org</a>",
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$errorId);
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}
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/**
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* Checks whether the given CSR contains a vulnerable key
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*
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* @param $csr string
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* The CSR to be checked
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* @param $encoding string [optional]
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* The encoding the CSR is in (for the "-inform" parameter of OpenSSL,
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* currently only "PEM" (default) or "DER" allowed)
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* @return string containing the reason if the key is considered weak,
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* empty string otherwise
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*/
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function checkWeakKeyCSR($csr, $encoding = "PEM")
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{
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// non-PEM-encodings may be binary so don't use echo
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$descriptorspec = array(
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0 => array("pipe", "r"), // STDIN for child
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1 => array("pipe", "w"), // STDOUT for child
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);
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$encoding = escapeshellarg($encoding);
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$proc = proc_open("openssl req -inform $encoding -text -noout",
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$descriptorspec, $pipes);
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if (is_resource($proc))
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{
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fwrite($pipes[0], $csr);
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fclose($pipes[0]);
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$csrText = "";
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while (!feof($pipes[1]))
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{
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$csrText .= fread($pipes[1], 8192);
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}
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fclose($pipes[1]);
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if (($status = proc_close($proc)) !== 0 || $csrText === "")
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{
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return _("I didn't receive a valid Certificate Request, hit ".
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"the back button and try again.");
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}
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} else {
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return failWithId("checkWeakKeyCSR(): Failed to start OpenSSL");
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}
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return checkWeakKeyText($csrText);
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}
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/**
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* Checks whether the given X509 certificate contains a vulnerable key
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*
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* @param $cert string
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* The X509 certificate to be checked
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* @param $encoding string [optional]
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* The encoding the certificate is in (for the "-inform" parameter of
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* OpenSSL, currently only "PEM" (default), "DER" or "NET" allowed)
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* @return string containing the reason if the key is considered weak,
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* empty string otherwise
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*/
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function checkWeakKeyX509($cert, $encoding = "PEM")
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{
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// non-PEM-encodings may be binary so don't use echo
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$descriptorspec = array(
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0 => array("pipe", "r"), // STDIN for child
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1 => array("pipe", "w"), // STDOUT for child
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);
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$encoding = escapeshellarg($encoding);
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$proc = proc_open("openssl x509 -inform $encoding -text -noout",
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$descriptorspec, $pipes);
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if (is_resource($proc))
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{
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fwrite($pipes[0], $cert);
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fclose($pipes[0]);
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$certText = "";
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while (!feof($pipes[1]))
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{
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$certText .= fread($pipes[1], 8192);
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}
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fclose($pipes[1]);
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if (($status = proc_close($proc)) !== 0 || $certText === "")
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{
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return _("I didn't receive a valid Certificate Request, hit ".
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"the back button and try again.");
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}
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} else {
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return failWithId("checkWeakKeyCSR(): Failed to start OpenSSL");
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}
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return checkWeakKeyText($certText);
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}
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/**
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* Checks whether the given SPKAC contains a vulnerable key
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*
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* @param $spkac string
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* The SPKAC to be checked
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* @param $spkacname string [optional]
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* The name of the variable that contains the SPKAC. The default is
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* "SPKAC"
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* @return string containing the reason if the key is considered weak,
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* empty string otherwise
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*/
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function checkWeakKeySPKAC($spkac, $spkacname = "SPKAC")
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{
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/* Check for the debian OpenSSL vulnerability */
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$spkac = escapeshellarg($spkac);
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$spkacname = escapeshellarg($spkacname);
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$spkacText = `echo $spkac | openssl spkac -spkac $spkacname`;
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if ($spkacText === null) {
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return _("I didn't receive a valid Certificate Request, hit the ".
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"back button and try again.");
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}
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return checkWeakKeyText($spkacText);
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}
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/**
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* Checks whether the given text representation of a CSR or a SPKAC contains
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* a weak key
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*
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* @param $text string
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* The text representation of a key as output by the
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* "openssl <foo> -text -noout" commands
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* @return string containing the reason if the key is considered weak,
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* empty string otherwise
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*/
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function checkWeakKeyText($text)
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{
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/* Which public key algorithm? */
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if (!preg_match('/^\s*Public Key Algorithm: ([^\s]+)$/m', $text,
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$algorithm))
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{
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return failWithId("checkWeakKeyText(): Couldn't extract the ".
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"public key algorithm used");
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} else {
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$algorithm = $algorithm[1];
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}
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if ($algorithm === "rsaEncryption")
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{
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if (!preg_match('/^\s*RSA Public Key: \((\d+) bit\)$/m', $text,
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$keysize))
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{
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return failWithId("checkWeakKeyText(): Couldn't parse the RSA ".
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"key size");
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} else {
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$keysize = intval($keysize[1]);
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}
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if ($keysize < 1024)
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{
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return sprintf(_("The keys that you use are very small ".
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"and therefore insecure. Please generate stronger ".
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"keys. More information about this issue can be ".
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"found in %sthe wiki%s"),
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"<a href='//wiki.cacert.org/WeakKeys#SmallKey'>",
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"</a>");
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} elseif ($keysize < 2048) {
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// not critical but log so we have some statistics about
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||||
// affected users
|
||||
trigger_error("checkWeakKeyText(): Certificate for small ".
|
||||
"key (< 2048 bit) requested", E_USER_NOTICE);
|
||||
}
|
||||
|
||||
|
||||
$debianVuln = checkDebianVulnerability($text, $keysize);
|
||||
if ($debianVuln === true)
|
||||
{
|
||||
return sprintf(_("The keys you use have very likely been ".
|
||||
"generated with a vulnerable version of OpenSSL which ".
|
||||
"was distributed by debian. Please generate new keys. ".
|
||||
"More information about this issue can be found in ".
|
||||
"%sthe wiki%s"),
|
||||
"<a href='//wiki.cacert.org/WeakKeys#DebianVulnerability'>",
|
||||
"</a>");
|
||||
} elseif ($debianVuln === false) {
|
||||
// not vulnerable => do nothing
|
||||
} else {
|
||||
return failWithId("checkWeakKeyText(): Something went wrong in".
|
||||
"checkDebianVulnerability()");
|
||||
}
|
||||
|
||||
if (!preg_match('/^\s*Exponent: (\d+) \(0x[0-9a-fA-F]+\)$/m', $text,
|
||||
$exponent))
|
||||
{
|
||||
return failWithId("checkWeakKeyText(): Couldn't parse the RSA ".
|
||||
"exponent");
|
||||
} else {
|
||||
$exponent = $exponent[1]; // exponent might be very big =>
|
||||
//handle as string using bc*()
|
||||
|
||||
if (bccomp($exponent, "3") === 0)
|
||||
{
|
||||
return sprintf(_("The keys you use might be insecure. ".
|
||||
"Although there is currently no known attack for ".
|
||||
"reasonable encryption schemes, we're being ".
|
||||
"cautious and don't allow certificates for such ".
|
||||
"keys. Please generate stronger keys. More ".
|
||||
"information about this issue can be found in ".
|
||||
"%sthe wiki%s"),
|
||||
"<a href='//wiki.cacert.org/WeakKeys#SmallExponent'>",
|
||||
"</a>");
|
||||
} elseif (!(bccomp($exponent, "65537") >= 0 &&
|
||||
(bccomp($exponent, "100000") === -1 ||
|
||||
// speed things up if way smaller than 2^256
|
||||
bccomp($exponent, bcpow("2", "256")) === -1) )) {
|
||||
// 65537 <= exponent < 2^256 recommended by NIST
|
||||
// not critical but log so we have some statistics about
|
||||
// affected users
|
||||
trigger_error("checkWeakKeyText(): Certificate for ".
|
||||
"unsuitable exponent '$exponent' requested",
|
||||
E_USER_NOTICE);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* No weakness found */
|
||||
return "";
|
||||
}
|
||||
|
||||
/**
|
||||
* Reimplement the functionality of the openssl-vulnkey tool
|
||||
*
|
||||
* @param $text string
|
||||
* The text representation of a key as output by the
|
||||
* "openssl <foo> -text -noout" commands
|
||||
* @param $keysize int [optional]
|
||||
* If the key size is already known it can be provided so it doesn't
|
||||
* have to be parsed again. This also skips the check whether the key
|
||||
* is an RSA key => use wisely
|
||||
* @return TRUE if key is vulnerable, FALSE otherwise, NULL in case of error
|
||||
*/
|
||||
function checkDebianVulnerability($text, $keysize = 0)
|
||||
{
|
||||
$keysize = intval($keysize);
|
||||
|
||||
if ($keysize === 0)
|
||||
{
|
||||
/* Which public key algorithm? */
|
||||
if (!preg_match('/^\s*Public Key Algorithm: ([^\s]+)$/m', $text,
|
||||
$algorithm))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't extract ".
|
||||
"the public key algorithm used", E_USER_WARNING);
|
||||
return null;
|
||||
} else {
|
||||
$algorithm = $algorithm[1];
|
||||
}
|
||||
|
||||
if ($algorithm !== "rsaEncryption") return false;
|
||||
|
||||
/* Extract public key size */
|
||||
if (!preg_match('/^\s*RSA Public Key: \((\d+) bit\)$/m', $text,
|
||||
$keysize))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't parse the ".
|
||||
"RSA key size", E_USER_WARNING);
|
||||
return null;
|
||||
} else {
|
||||
$keysize = intval($keysize[1]);
|
||||
}
|
||||
}
|
||||
|
||||
// $keysize has been made sure to contain an int
|
||||
$blacklist = "/usr/share/openssl-blacklist/blacklist.RSA-$keysize";
|
||||
if (!(is_file($blacklist) && is_readable($blacklist)))
|
||||
{
|
||||
if (in_array($keysize, array(512, 1024, 2048, 4096)))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Blacklist for ".
|
||||
"$keysize bit keys not accessible. Expected at ".
|
||||
"$blacklist", E_USER_ERROR);
|
||||
return null;
|
||||
}
|
||||
|
||||
trigger_error("checkDebianVulnerability(): $blacklist is not ".
|
||||
"readable. Unsupported key size?", E_USER_WARNING);
|
||||
return false;
|
||||
}
|
||||
|
||||
|
||||
/* Extract RSA modulus */
|
||||
if (!preg_match('/^\s*Modulus \(\d+ bit\):\n'.
|
||||
'((?:\s*[0-9a-f][0-9a-f]:(?:\n)?)+[0-9a-f][0-9a-f])$/m',
|
||||
$text, $modulus))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't extract the ".
|
||||
"RSA modulus", E_USER_WARNING);
|
||||
return null;
|
||||
} else {
|
||||
$modulus = $modulus[1];
|
||||
// strip whitespace and colon leftovers
|
||||
$modulus = str_replace(array(" ", "\t", "\n", ":"), "", $modulus);
|
||||
|
||||
// when using "openssl xxx -text" first byte was 00 in all my test
|
||||
// cases but 00 not present in the "openssl xxx -modulus" output
|
||||
if ($modulus[0] === "0" && $modulus[1] === "0")
|
||||
{
|
||||
$modulus = substr($modulus, 2);
|
||||
} else {
|
||||
trigger_error("checkDebianVulnerability(): First byte is not ".
|
||||
"zero", E_USER_NOTICE);
|
||||
}
|
||||
|
||||
$modulus = strtoupper($modulus);
|
||||
}
|
||||
|
||||
|
||||
/* calculate checksum and look it up in the blacklist */
|
||||
$checksum = substr(sha1("Modulus=$modulus\n"), 20);
|
||||
|
||||
// $checksum and $blacklist should be safe, but just to make sure
|
||||
$checksum = escapeshellarg($checksum);
|
||||
$blacklist = escapeshellarg($blacklist);
|
||||
exec("grep $checksum $blacklist", $dummy, $debianVuln);
|
||||
if ($debianVuln === 0) // grep returned something => it is on the list
|
||||
{
|
||||
return true;
|
||||
} elseif ($debianVuln === 1) { // grep returned nothing
|
||||
return false;
|
||||
} else {
|
||||
trigger_error("checkDebianVulnerability(): Something went wrong ".
|
||||
"when looking up the key with checksum $checksum in the ".
|
||||
"blacklist $blacklist", E_USER_ERROR);
|
||||
return null;
|
||||
}
|
||||
|
||||
// Should not get here
|
||||
return null;
|
||||
}
|
||||
?>
|
||||
|
|
|
|||
Loading…
Reference in a new issue