diff options
Diffstat (limited to 'includes/lib')
| -rw-r--r-- | includes/lib/check_weak_key.php | 323 | ||||
| -rw-r--r-- | includes/lib/general.php | 84 |
2 files changed, 406 insertions, 1 deletions
diff --git a/includes/lib/check_weak_key.php b/includes/lib/check_weak_key.php new file mode 100644 index 0000000..ca13ba2 --- /dev/null +++ b/includes/lib/check_weak_key.php @@ -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 $blacklist", E_USER_ERROR); + return null; + } + + // Should not get here + return null; +} diff --git a/includes/lib/general.php b/includes/lib/general.php index 25d2561..d91b24e 100644 --- a/includes/lib/general.php +++ b/includes/lib/general.php @@ -47,4 +47,86 @@ function get_user_id_from_cert($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; + } +} + |