"Invalid SPKAC requests are not properly validated"pull/1/head
parent
9bde006b4d
commit
316ef65915
@ -0,0 +1,323 @@
|
||||
<?php /*
|
||||
LibreSSL - CAcert web application
|
||||
Copyright (C) 2004-2011 CAcert Inc.
|
||||
|
||||
This program is free software; you can redistribute it and/or modify
|
||||
it under the terms of the GNU General Public License as published by
|
||||
the Free Software Foundation; version 2 of the License.
|
||||
|
||||
This program is distributed in the hope that it will be useful,
|
||||
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
GNU General Public License for more details.
|
||||
|
||||
You should have received a copy of the GNU General Public License
|
||||
along with this program; if not, write to the Free Software
|
||||
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
||||
*/
|
||||
|
||||
// failWithId()
|
||||
require_once 'general.php';
|
||||
|
||||
|
||||
/**
|
||||
* Checks whether the given CSR contains a vulnerable key
|
||||
*
|
||||
* @param $csr string
|
||||
* The CSR to be checked
|
||||
* @param $encoding string [optional]
|
||||
* The encoding the CSR is in (for the "-inform" parameter of OpenSSL,
|
||||
* currently only "PEM" (default) or "DER" allowed)
|
||||
* @return string containing the reason if the key is considered weak,
|
||||
* empty string otherwise
|
||||
*/
|
||||
function checkWeakKeyCSR($csr, $encoding = "PEM")
|
||||
{
|
||||
$encoding = escapeshellarg($encoding);
|
||||
$status = runCommand("openssl req -inform $encoding -text -noout",
|
||||
$csr, $csrText);
|
||||
if ($status === true) {
|
||||
return failWithId("checkWeakKeyCSR(): Failed to start OpenSSL");
|
||||
}
|
||||
|
||||
if ($status !== 0 || $csrText === "") {
|
||||
return _("I didn't receive a valid Certificate Request. Hit ".
|
||||
"the back button and try again.");
|
||||
}
|
||||
|
||||
return checkWeakKeyText($csrText);
|
||||
}
|
||||
|
||||
/**
|
||||
* Checks whether the given X509 certificate contains a vulnerable key
|
||||
*
|
||||
* @param $cert string
|
||||
* The X509 certificate to be checked
|
||||
* @param $encoding string [optional]
|
||||
* The encoding the certificate is in (for the "-inform" parameter of
|
||||
* OpenSSL, currently only "PEM" (default), "DER" or "NET" allowed)
|
||||
* @return string containing the reason if the key is considered weak,
|
||||
* empty string otherwise
|
||||
*/
|
||||
function checkWeakKeyX509($cert, $encoding = "PEM")
|
||||
{
|
||||
$encoding = escapeshellarg($encoding);
|
||||
$status = runCommand("openssl x509 -inform $encoding -text -noout",
|
||||
$cert, $certText);
|
||||
if ($status === true) {
|
||||
return failWithId("checkWeakKeyX509(): Failed to start OpenSSL");
|
||||
}
|
||||
|
||||
if ($status !== 0 || $certText === "") {
|
||||
return _("I didn't receive a valid Certificate Request. Hit ".
|
||||
"the back button and try again.");
|
||||
}
|
||||
|
||||
return checkWeakKeyText($certText);
|
||||
}
|
||||
|
||||
/**
|
||||
* Checks whether the given SPKAC contains a vulnerable key
|
||||
*
|
||||
* @param $spkac string
|
||||
* The SPKAC to be checked
|
||||
* @param $spkacname string [optional]
|
||||
* The name of the variable that contains the SPKAC. The default is
|
||||
* "SPKAC"
|
||||
* @return string containing the reason if the key is considered weak,
|
||||
* empty string otherwise
|
||||
*/
|
||||
function checkWeakKeySPKAC($spkac, $spkacname = "SPKAC")
|
||||
{
|
||||
$spkacname = escapeshellarg($spkacname);
|
||||
$status = runCommand("openssl spkac -spkac $spkacname", $spkac, $spkacText);
|
||||
if ($status === true) {
|
||||
return failWithId("checkWeakKeySPKAC(): Failed to start OpenSSL");
|
||||
}
|
||||
|
||||
if ($status !== 0 || $spkacText === "") {
|
||||
return _("I didn't receive a valid Certificate Request. Hit the ".
|
||||
"back button and try again.");
|
||||
}
|
||||
|
||||
return checkWeakKeyText($spkacText);
|
||||
}
|
||||
|
||||
/**
|
||||
* Checks whether the given text representation of a CSR or a SPKAC contains
|
||||
* a weak key
|
||||
*
|
||||
* @param $text string
|
||||
* The text representation of a key as output by the
|
||||
* "openssl <foo> -text -noout" commands
|
||||
* @return string containing the reason if the key is considered weak,
|
||||
* empty string otherwise
|
||||
*/
|
||||
function checkWeakKeyText($text)
|
||||
{
|
||||
/* Which public key algorithm? */
|
||||
if (!preg_match('/^\s*Public Key Algorithm: ([^\s]+)$/m', $text,
|
||||
$algorithm))
|
||||
{
|
||||
return failWithId("checkWeakKeyText(): Couldn't extract the ".
|
||||
"public key algorithm used.\nData:\n$text");
|
||||
} else {
|
||||
$algorithm = $algorithm[1];
|
||||
}
|
||||
|
||||
|
||||
if ($algorithm === "rsaEncryption")
|
||||
{
|
||||
if (!preg_match('/^\s*RSA Public Key: \((\d+) bit\)$/m', $text,
|
||||
$keysize))
|
||||
{
|
||||
return failWithId("checkWeakKeyText(): Couldn't parse the RSA ".
|
||||
"key size.\nData:\n$text");
|
||||
} else {
|
||||
$keysize = intval($keysize[1]);
|
||||
}
|
||||
|
||||
if ($keysize < 1024)
|
||||
{
|
||||
return sprintf(_("The keys that you use are very small ".
|
||||
"and therefore insecure. Please generate stronger ".
|
||||
"keys. More information about this issue can be ".
|
||||
"found in %sthe wiki%s"),
|
||||
"<a href='//wiki.cacert.org/WeakKeys#SmallKey'>",
|
||||
"</a>");
|
||||
} elseif ($keysize < 2048) {
|
||||
// not critical but log so we have some statistics about
|
||||
// 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().\nKeysize: $keysize\n".
|
||||
"Data:\n$text");
|
||||
}
|
||||
|
||||
if (!preg_match('/^\s*Exponent: (\d+) \(0x[0-9a-fA-F]+\)$/m', $text,
|
||||
$exponent))
|
||||
{
|
||||
return failWithId("checkWeakKeyText(): Couldn't parse the RSA ".
|
||||
"exponent.\nData:\n$text");
|
||||
} 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,
|
||||
$algorithm))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't extract ".
|
||||
"the public key algorithm used.\nData:\n$text",
|
||||
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,
|
||||
$keysize))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't parse the ".
|
||||
"RSA key size.\nData:\n$text", 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, $modulus))
|
||||
{
|
||||
trigger_error("checkDebianVulnerability(): Couldn't extract the ".
|
||||
"RSA modulus.\nData:\n$text", 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);
|
||||
$debianVuln = runCommand("grep $checksum $blacklist");
|
||||
if ($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 New Issue