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Difference between revisions of "T1 Font Integer Overflow"
(→Sources: Blog post) |
m (Mentioning CVE-2011-0226.) |
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When dealing with op_callothersubr, arg_cnt is defined as an integer. arg_cnt is read from decoder‑>stack, which could be set to 0xfea50000 by charstring "fb ef". And this will bypass stack checking. Then "top ‑= arg_cnt" will make top point to data outside of decoder‑>stack. Actually it points to decoder‑>parse_callback. decoder‑>parse_callback address minus default address of that function to get ASLR offset. That's how it bypasses ASLR. |
When dealing with op_callothersubr, arg_cnt is defined as an integer. arg_cnt is read from decoder‑>stack, which could be set to 0xfea50000 by charstring "fb ef". And this will bypass stack checking. Then "top ‑= arg_cnt" will make top point to data outside of decoder‑>stack. Actually it points to decoder‑>parse_callback. decoder‑>parse_callback address minus default address of that function to get ASLR offset. That's how it bypasses ASLR. |
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| − | This vulnerability was actually addressed by Apple in {{wp|Mac OS X Snow Leopard|Mac OS X v10.6.8}}/[http://support.apple.com/kb/HT4723 Security Update 2011-004], but a fix was never pushed to [[iOS]]. Its CVE identifier is ''CVE-2011-0202''. |
+ | This vulnerability was actually addressed by Apple in {{wp|Mac OS X Snow Leopard|Mac OS X v10.6.8}}/[http://support.apple.com/kb/HT4723 Security Update 2011-004], but a fix was never pushed to [[iOS]]. (Its CVE identifier is ''CVE-2011-0202''.) |
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| + | When Apple released iOS 4.2.9/4.3.4 to patch this vulnerability, it received a different CVE identifier (CVE-2011-0226). |
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==Sources== |
==Sources== |
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* [http://support.apple.com/kb/HT4723 Apple KB] |
* [http://support.apple.com/kb/HT4723 Apple KB] |
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* http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0202 |
* http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0202 |
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| + | * http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0226 |
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* http://intrepidusgroup.com/insight/2011/07/reversing-jailbreakme-com-4/ |
* http://intrepidusgroup.com/insight/2011/07/reversing-jailbreakme-com-4/ |
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Revision as of 22:36, 15 July 2011
The T1 Font Integer Overflow (A.K.A DejaVu as it is very similar to the Malformed CFF Vulnerability[1]) is a vulnerability used in Saffron.
Credit for Exploitation
Description
When dealing with op_callothersubr, arg_cnt is defined as an integer. arg_cnt is read from decoder‑>stack, which could be set to 0xfea50000 by charstring "fb ef". And this will bypass stack checking. Then "top ‑= arg_cnt" will make top point to data outside of decoder‑>stack. Actually it points to decoder‑>parse_callback. decoder‑>parse_callback address minus default address of that function to get ASLR offset. That's how it bypasses ASLR.
This vulnerability was actually addressed by Apple in Template:Wp/Security Update 2011-004, but a fix was never pushed to iOS. (Its CVE identifier is CVE-2011-0202.)
When Apple released iOS 4.2.9/4.3.4 to patch this vulnerability, it received a different CVE identifier (CVE-2011-0226).
