Pixar Renderman Install Helper Arbitrary File Read Privilege Escalation Vulnerability

Summary

A local privilege escalation vulnerability exists in the install helper tool of the Mac OS X version of Pixar Renderman, version 22.2.0. A user with local access can use this vulnerability to read any root file from the file system. An attacker would need local access to the machine to successfully exploit this flaw.

Tested Versions

Renderman 22.2.0 for Mac OS X

Product URLs

<https://renderman.pixar.com>

CVSSv3 Score

7.1 - CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

CWE

CWE-19: Improper Input Validation

Details

Renderman is a rendering application used in animation and film production. It is widely used for advanced rendering and shading in many large-scale environments. When installing the Mac OS X version of the application, a helper tool is installed and launched as root. This service continues to listen even after completing installation. The vulnerability lies in the lack of verification in the Dispatch function. The caller of this function is not checked, and the function is exposed to any user. The relevant code is shown below.

case 0x101D2:                                                                     [0]
      reply = xpc_dictionary_create_reply(a1[1]);
      filepath = xpc_dictionary_get_string(a1[1], "filepath");                    [1]
      fileoflag = xpc_dictionary_get_int64(a1[1], "fileoflag");
      filemode = xpc_dictionary_get_int64(a1[1], "filemode");
      syslog(5, "openFile request \"%s\" %d %d", filepath, fileoflag, filemode);
      ...
      v9 = open(filepath, fileoflag, filemode);                                   [2]

The first part of the function, [0], gets the message ID and passes it through a switch statement. If the case is the one shown, this code block is entered. At location [1], command options are parsed directly from the XPC message. These variables are then passed into the function open, [2], and a file descriptor is returned to the caller. An attacker could use this vulnerability to read any file from the file system, crossing a privilege boundary.

Timeline

2018-11-28 - Vendor disclosure
2018-12-11 - Vendor patched
2019-01-14 - Public release