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Fix for https://bugs.cacert.org/view.php?id=1255

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"DSA certificate issuing ignores key strength"
This commit is contained in:
Wytze van der Raay 2014-03-10 16:32:07 +00:00
parent 05514a053f
commit 4937cf6038
1 changed files with 83 additions and 12 deletions
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95
includes/lib/check_weak_key.php
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@ -128,15 +128,14 @@ function checkWeakKeyText($text)
if ($algorithm === "rsaEncryption")
{
if (!preg_match('/^\s*RSA Public Key: \((\d+) bit\)$/m', $text,
$keysize))
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 ($keysize < 2048)
{
return sprintf(_("The keys that you use are very small ".
@ -146,8 +145,7 @@ function checkWeakKeyText($text)
"<a href='//wiki.cacert.org/WeakKeys#SmallKey'>",
"</a>");
}
$debianVuln = checkDebianVulnerability($text, $keysize);
if ($debianVuln === true)
{
@ -165,7 +163,7 @@ function checkWeakKeyText($text)
"checkDebianVulnerability().\nKeysize: $keysize\n".
"Data:\n$text");
}
if (!preg_match('/^\s*Exponent: (\d+) \(0x[0-9a-fA-F]+\)$/m', $text,
$exponent))
{
@ -187,9 +185,9 @@ function checkWeakKeyText($text)
"<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($exponent, bcpow("2", "256")) === -1) )) {
(bccomp($exponent, "100000") === -1 ||
// speed things up if way smaller than 2^256
bccomp($exponent, bcpow("2", "256")) === -1) )) {
// 65537 <= exponent < 2^256 recommended by NIST
// not critical but log so we have some statistics about
// affected users
@ -198,10 +196,83 @@ function checkWeakKeyText($text)
E_USER_NOTICE);
}
}
}
/* No weakness found */
return "";
// 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//Fails to work due to outdated OpenSSL 0.9.8o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.");
}
/**