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Fix for https://bugs.cacert.org/view.php?id=978

Browse source 
"Invalid SPKAC requests are not properly validated"
This commit is contained in:
Wytze van der Raay 2012-10-31 10:03:33 +00:00
parent 9bde006b4d
commit 316ef65915
5 changed files with 410 additions and 359 deletions
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1
includes/account.php
View file

@ -17,6 +17,7 @@
*/
require_once("../includes/loggedin.php");
require_once("../includes/lib/l10n.php");
require_once('lib/check_weak_key.php');
loadem("account");

358
includes/account_stuff.php
View file

@ -284,361 +284,3 @@ function hideall() {
</body>
</html><?
}
/**
* Produces a log entry with the error message with log level E_USER_WARN
* and a random ID an returns a message that can be displayed to the user
* including the generated ID
*
* @param $errormessage string
* The error message that should be logged
* @return string containing the generated ID that can be displayed to the
* user
*/
function failWithId($errormessage) {
$errorId = rand();
trigger_error("$errormessage. ID: $errorId", E_USER_WARNING);
return sprintf(_("Something went wrong when processing your request. ".
"Please contact %s for help and provide them with the ".
"following ID: %d"),
"<a href='mailto:support@cacert.org?subject=System%20Error%20-%20".
"ID%3A%20$errorId'>support@cacert.org</a>",
$errorId);
}
/**
* 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")
{
// non-PEM-encodings may be binary so don't use echo
$descriptorspec = array(
0 => array("pipe", "r"), // STDIN for child
1 => array("pipe", "w"), // STDOUT for child
);
$encoding = escapeshellarg($encoding);
$proc = proc_open("openssl req -inform $encoding -text -noout",
$descriptorspec, $pipes);
if (is_resource($proc))
{
fwrite($pipes[0], $csr);
fclose($pipes[0]);
$csrText = "";
while (!feof($pipes[1]))
{
$csrText .= fread($pipes[1], 8192);
}
fclose($pipes[1]);
if (($status = proc_close($proc)) !== 0 || $csrText === "")
{
return _("I didn't receive a valid Certificate Request, hit ".
"the back button and try again.");
}
} else {
return failWithId("checkWeakKeyCSR(): Failed to start OpenSSL");
}
return checkWeakKeyText($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")
{
// non-PEM-encodings may be binary so don't use echo
$descriptorspec = array(
0 => array("pipe", "r"), // STDIN for child
1 => array("pipe", "w"), // STDOUT for child
);
$encoding = escapeshellarg($encoding);
$proc = proc_open("openssl x509 -inform $encoding -text -noout",
$descriptorspec, $pipes);
if (is_resource($proc))
{
fwrite($pipes[0], $cert);
fclose($pipes[0]);
$certText = "";
while (!feof($pipes[1]))
{
$certText .= fread($pipes[1], 8192);
}
fclose($pipes[1]);
if (($status = proc_close($proc)) !== 0 || $certText === "")
{
return _("I didn't receive a valid Certificate Request, hit ".
"the back button and try again.");
}
} else {
return failWithId("checkWeakKeyCSR(): Failed to start OpenSSL");
}
return checkWeakKeyText($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")
{
/* Check for the debian OpenSSL vulnerability */
$spkac = escapeshellarg($spkac);
$spkacname = escapeshellarg($spkacname);
$spkacText = `echo $spkac | openssl spkac -spkac $spkacname`;
if ($spkacText === null) {
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");
} 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");
} 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()");
}
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;
}
?>

323
includes/lib/check_weak_key.php Normal file
View file

@ -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;
}

84
includes/lib/general.php
View file

@ -47,4 +47,86 @@ function get_user_id_from_cert($serial, $issuer_cn)
return -1;
}
?>
/**
* Produces a log entry with the error message with log level E_USER_WARN
* and a random ID an returns a message that can be displayed to the user
* including the generated ID
*
* @param $errormessage string
* The error message that should be logged
* @return string containing the generated ID that can be displayed to the
* user
*/
function failWithId($errormessage) {
$errorId = rand();
trigger_error("$errormessage. ID: $errorId", E_USER_WARNING);
return sprintf(_("Something went wrong when processing your request. ".
"Please contact %s for help and provide them with the ".
"following ID: %d"),
"<a href='mailto:support@cacert.org?subject=System%20Error%20-%20".
"ID%3A%20$errorId'>support@cacert.org</a>",
$errorId);
}
/**
* Runs a command on the shell and return it's exit code and output
*
* @param string $command
* The command to run. Make sure that you escapeshellarg() any non-constant
* parts as this is executed on a shell!
* @param string|bool $input
* The input that is passed to the command via STDIN, if true the real
* STDIN is passed through
* @param string|bool $output
* The output the command wrote to STDOUT (this is passed as reference),
* if true the output will be written to the real STDOUT. Output is ignored
* by default
* @param string|bool $errors
* The output the command wrote to STDERR (this is passed as reference),
* if true (default) the output will be written to the real STDERR
*
* @return int|bool
* The exit code of the command, true if the execution of the command
* failed (true because then
* <code>if (runCommand('echo "foo"')) handle_error();</code> will work)
*/
function runCommand($command, $input = "", &$output = null, &$errors = true) {
$descriptorspec = array();
if ($input !== true) {
$descriptorspec[0] = array("pipe", "r"); // STDIN for child
}
if ($output !== true) {
$descriptorspec[1] = array("pipe", "w"); // STDOUT for child
}
if ($errors !== true) {
$descriptorspec[2] = array("pipe", "w"); // STDERR for child
}
$proc = proc_open($command, $descriptorspec, $pipes);
if (is_resource($proc))
{
if ($input !== true) {
fwrite($pipes[0], $input);
fclose($pipes[0]);
}
if ($output !== true) {
$output = stream_get_contents($pipes[1]);
}
if ($errors !== true) {
$errors = stream_get_contents($pipes[2]);
}
return proc_close($proc);
} else {
return true;
}
}

3
www/api/ccsr.php
View file

@ -15,6 +15,9 @@
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
require_once '../../includes/lib/check_weak_key.php';
$username = mysql_real_escape_string($_REQUEST['username']);
$password = mysql_real_escape_string($_REQUEST['password']);