Here is how you test if your GnuTLS library is vulnerable to the NUL-in-CN/SAN issue (i.e., [GNUTLS-SA-2009-4] [CVE-2009-2730]).
Download and build: http://git.savannah.gnu.org/cgit/gnutls.git/plain/tests/nul-in-x509-names.c For example: j...@mocca:~$ wget -q http://git.savannah.gnu.org/cgit/gnutls.git/plain/tests/nul-in-x509-names.c j...@mocca:~$ gcc -o nul-in-x509-names nul-in-x509-names.c -lgnutls j...@mocca:~$ ./nul-in-x509-names gnutls_x509_crt_check_hostname OK (NUL-IN-CN) gnutls_x509_crt_check_hostname OK (NUL-IN-SAN) j...@mocca:~$ If your library have not yet been patched, the output will look like: gnutls_x509_crt_check_hostname BROKEN (NUL-IN-CN) gnutls_x509_crt_check_hostname BROKEN (NUL-IN-SAN) If you have a locally installed GnuTLS version and wants to check your system library version, on GNU/Linux system you can use the LD_PRELOAD variable to point at the exact library version to test. For example on my Debian system: j...@mocca:~$ LD_PRELOAD=/usr/lib/libgnutls.so ./nul-in-x509-names gnutls_x509_crt_check_hostname BROKEN (NUL-IN-CN) gnutls_x509_crt_check_hostname BROKEN (NUL-IN-SAN) j...@mocca:~$ To verify that displaying of certificates works correctly, you can use two sample certificates provided by Tomas Hoger <[email protected]>. To test whether NUL in CN is handled properly, here is how you do it: j...@mocca:~$ cat>nul-cn.pem -----BEGIN CERTIFICATE----- MIIDjTCCAnWgAwIBAgIBATANBgkqhkiG9w0BAQUFADB0MQswCQYDVQQGEwJHQjES MBAGA1UECBMJQmVya3NoaXJlMRAwDgYDVQQHEwdOZXdidXJ5MRcwFQYDVQQKEw5N eSBDb21wYW55IEx0ZDELMAkGA1UECxMCQ0ExGTAXBgNVBAMTEE5VTEwtZnJpZW5k bHkgQ0EwHhcNMDkwODA0MDczMzQzWhcNMTkwODAyMDczMzQzWjAjMSEwHwYDVQQD Exh3d3cuYmFuay5jb20ALmJhZGd1eS5jb20wggEiMA0GCSqGSIb3DQEBAQUAA4IB DwAwggEKAoIBAQDNJnCWqaZdPpztDwgVWnwXJWhorxO5rUH6ElTihHJ9WNHiQELB We0FPaoQU3AAiDp3oMBWnqx9ISpxRFEIvBcH2qijdtxRvBuK9gIaVb9GtERrJ16+ 5ReLVrLGgjYRg6i/9y8NF/bNR7VvK6ZBto0zX+rqi7Ea4pk4/1lbCqFxE8o3P7mw HpGayJM1DErgnfTSYcdOW0EKfDFUmdv1Zc6A08ICN2T9VBJ76qyFWVwX4S720Kjy 0C6UWS/Cpl/aB957LhQH7eQnJDedCS6x+VpIuYAkQ+bLx24139VpNP/m1p7odmZu X1kBPJY77HILPB6VD85oE5wi3Ru1RChQSgV/AgMBAAGjezB5MAkGA1UdEwQCMAAw LAYJYIZIAYb4QgENBB8WHU9wZW5TU0wgR2VuZXJhdGVkIENlcnRpZmljYXRlMB0G A1UdDgQWBBQzFSS+2mY6BovZJzQ6r2JA5JVmXTAfBgNVHSMEGDAWgBQKaTlfnTAE GAguAg7m6p2yJvbiajANBgkqhkiG9w0BAQUFAAOCAQEAMmUjH8jZU4SC0ArrFFEk A7xsGypa/hvw6GkMKxmGz38ydtgr0s+LxNG2W5xgo5kuknIGzt6L0qLSiXwTqQtO vhIJ5dYoOqynJlaUfxPuZH3elGB1wbxVl9SqE44C2LCwcFOuGFPOqrIshT7j8+Em 8/pc7vh7C8Y5tQQzXq64Xg5mzKjAag3sYMHF2TnqvRuPHH0WOLHoyDcBqkuZ3+QP EL5h7prPzScFRgBg2Gp0CDI8i5ABagczDGyQ2+r7ahcadrtzFCfhpH7V3TCxXfIO qtSy1Uz2T5EqB/Q3wc9IGcX+fpKWqN9QajGSo7EU/kHMSWKYTerFugUtScMicu9B CQ== -----END CERTIFICATE----- j...@mocca:~$ certtool -i < nul-cn.pem ... Subject: CN=#13187777772e62616e6b2e636f6d002e6261646775792e636f6d ... Notice how the Subject line is LDAP escaped when it contains a NUL value. Buggy versions would display the cert like this: Subject: CN=www.bank.com To test whether NUL in CN is handled properly, here is how you do it: j...@mocca:~$ cat>nul-san.pem -----BEGIN CERTIFICATE----- MIIDrTCCApWgAwIBAgIBADANBgkqhkiG9w0BAQUFADB0MQswCQYDVQQGEwJHQjES MBAGA1UECBMJQmVya3NoaXJlMRAwDgYDVQQHEwdOZXdidXJ5MRcwFQYDVQQKEw5N eSBDb21wYW55IEx0ZDELMAkGA1UECxMCQ0ExGTAXBgNVBAMTEE5VTEwtZnJpZW5k bHkgQ0EwHhcNMDkwODA0MDY1MzA1WhcNMTkwODAyMDY1MzA1WjAZMRcwFQYDVQQD Ew53d3cuYmFkZ3V5LmNvbTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEB AM0mcJappl0+nO0PCBVafBclaGivE7mtQfoSVOKEcn1Y0eJAQsFZ7QU9qhBTcACI OnegwFaerH0hKnFEUQi8FwfaqKN23FG8G4r2AhpVv0a0RGsnXr7lF4tWssaCNhGD qL/3Lw0X9s1HtW8rpkG2jTNf6uqLsRrimTj/WVsKoXETyjc/ubAekZrIkzUMSuCd 9NJhx05bQQp8MVSZ2/VlzoDTwgI3ZP1UEnvqrIVZXBfhLvbQqPLQLpRZL8KmX9oH 3nsuFAft5CckN50JLrH5Wki5gCRD5svHbjXf1Wk0/+bWnuh2Zm5fWQE8ljvscgs8 HpUPzmgTnCLdG7VEKFBKBX8CAwEAAaOBpDCBoTAJBgNVHRMEAjAAMCwGCWCGSAGG +EIBDQQfFh1PcGVuU1NMIEdlbmVyYXRlZCBDZXJ0aWZpY2F0ZTAdBgNVHQ4EFgQU MxUkvtpmOgaL2Sc0Oq9iQOSVZl0wHwYDVR0jBBgwFoAUCmk5X50wBBgILgIO5uqd sib24mowJgYDVR0RBB8wHYIbd3d3LmJhbmsuY29tAHd3dy5iYWRndXkuY29tMA0G CSqGSIb3DQEBBQUAA4IBAQAnbn2zqYZSV2qgxjBsHpQJp2+t/hGfvjKNAXuLlGbX fLaxkPzk9bYyvGxxI7EYiNZHvNoHx15GcTrmQG7Bfx1WlnBl2FGp3J6lBgCY5x4Q vIK6AOVOog8+7Irdb8bJweztbXwxPmaHR6GLFTwhfuwheD0hcHK6cMNk+B1P2dAn PD5+olmuvprTAESncjrjP8ibxY+xlP4AD264FIjxA1CRUa/wHve4WqRXNS3xrciu 3SlhFH3q0TSAXBv960PcIW3GRPk7VHbEkVuspI5y59gk/6dawO8nw9fk+X9VjQ0w 7KLZbch29L6UPRIySpFP28PndgdaEpcYtxUAmFkhiT41 -----END CERTIFICATE----- j...@mocca:~$ certtool -i < nul-san.pem ... Subject Alternative Name (not critical): warning: SAN contains an embedded NUL, replacing with '!' DNSname: www.bank.com!www.badguy.com ... Notice the warning and the full output. Buggy versions would display the cert like this: Subject Alternative Name (not critical): DNSname: www.bank.com I hope this helps you test your system! /Simon
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