You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
390 lines
13 KiB
PHP
390 lines
13 KiB
PHP
<?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*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 < 2048)
|
|
{
|
|
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>");
|
|
}
|
|
|
|
$debianVuln = checkDebianVulnerability($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, "65537") < 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 "";
|
|
} // End RSA
|
|
|
|
/*
|
|
//Fails to work due to outdated OpenSSL 0.9.8o
|
|
//For this to work OpenSSL 1.0.1f or newer is required
|
|
//which is currently unavailable on the systems
|
|
//If DSA2048 or longer is used the CSR hangs pending on the signer.
|
|
if ($algorithm === "dsaEncryption")
|
|
{
|
|
if (!preg_match('/^\s*Public Key Algorithm:\s+dsaEncryption\s+pub:\s+([0-9a-fA-F:\s]+)\s+P:\s+([0-9a-fA-F:\s]+)\s+Q:\s+([0-9a-fA-F:\s]+)\s+G:\s+([0-9a-fA-F:\s]+)\s+$/sm', $text, $keydetail))
|
|
{
|
|
return failWithId("checkWeakKeyText(): Couldn't parse the DSA ".
|
|
"key size.\nData:\n$text");
|
|
}
|
|
|
|
$key_pub = strtr(preg_replace("/[^0-9a-fA-F]/", "", $keydetail[1]), "ABCDEF", "abcdef");
|
|
$key_P = strtr(preg_replace("/[^0-9a-fA-F]/", "", $keydetail[2]), "ABCDEF", "abcdef");
|
|
$key_Q = strtr(preg_replace("/[^0-9a-fA-F]/", "", $keydetail[3]), "ABCDEF", "abcdef");
|
|
$key_G = strtr(preg_replace("/[^0-9a-fA-F]/", "", $keydetail[4]), "ABCDEF", "abcdef");
|
|
|
|
//Verify the numbers provided by the client
|
|
$num_pub = @gmp_init($key_pub, 16);
|
|
$num_P = @gmp_init($key_P, 16);
|
|
$num_Q = @gmp_init($key_Q, 16);
|
|
$num_G = @gmp_init($key_G, 16);
|
|
|
|
$bit_P = ltrim(gmp_strval($num_P, 2), "0");
|
|
$keysize = strlen($bit_P);
|
|
|
|
if ($keysize < 2048) {
|
|
return sprintf(_("The keys that you use are very small ".
|
|
"and therefore insecure. Please generate stronger ".
|
|
"keys. More information about this issue can be ".
|
|
"found in %sthe wiki%s"),
|
|
"<a href='//wiki.cacert.org/WeakKeys#SmallKey'>",
|
|
"</a>");
|
|
}
|
|
|
|
//Following checks based on description of key generation in Wikipedia
|
|
//These checks do not ensure a strong key, but at least check for enough sanity in the key material
|
|
// cf. https://en.wikipedia.org/wiki/Digital_Signature_Algorithm#Key_generation
|
|
|
|
//Check that P is prime
|
|
if(!gmp_testprime($num_P)) {
|
|
return failWithId("checkWeakKeyText(): The supplied DSA ".
|
|
"key does seem to have a non-prime public modulus.\nData:\n$text");
|
|
}
|
|
|
|
//Check that Q is prime
|
|
if(!gmp_testprime($num_Q)) {
|
|
return failWithId("checkWeakKeyText(): The supplied DSA ".
|
|
"key does seem to have a non-prime Q-value.\nData:\n$text");
|
|
}
|
|
|
|
//Check if P-1 is diviseable by Q
|
|
if(0 !== gmp_cmp("1", gmp_mod($num_P, $num_Q))) {
|
|
return failWithId("checkWeakKeyText(): The supplied DSA ".
|
|
"key does seem to have P mod Q === 1 (i.e. P-1 is not diviseable by Q).\nData:\n$text");
|
|
}
|
|
|
|
//Check the numbers are all less than the public modulus P
|
|
if(0 <= gmp_cmp($num_Q, $num_P) || 0 <= gmp_cmp($num_G, $num_P) || 0 <= gmp_cmp($num_pub, $num_P)) {
|
|
return failWithId("checkWeakKeyText(): The supplied DSA ".
|
|
"key does seem to be normalized to have Q < P, G < P and pub < P.\nData:\n$text");
|
|
}
|
|
|
|
// No weakness found
|
|
return "";
|
|
} // End DSA
|
|
*/
|
|
|
|
|
|
return _("The keys you supplied use an unrecognized algorithm. ".
|
|
"For security reasons these keys can not be signed by CAcert.");
|
|
}
|
|
|
|
/**
|
|
* 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*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(): $blacklist is not ".
|
|
"readable. Unsupported key size?", E_USER_WARNING);
|
|
return false;
|
|
}
|
|
|
|
|
|
/* Extract RSA modulus */
|
|
if (!preg_match('/^\s*Modulus:\n'.
|
|
'((?:\s*[0-9a-f][0-9a-f]:(?:\n)?)+[0-9a-f][0-9a-f])$/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;
|
|
}
|