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Difference between revisions of "Malformed CFF Vulnerability"
m (PDF CFF Font Stack Overflow moved to Malformed CFF Vulnerability: The old name implied that the PDF parser was involved.) |
(added the exploit data) |
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== Credit == |
== Credit == |
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[[User:Comex|comex]] |
[[User:Comex|comex]] |
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| + | |||
| + | == exploit == |
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| + | |||
| + | diff -u -r freetype-2.4.1/src/cff/cffgload.c freetype-2.4.1_patched/src/cff/cffgload.c |
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| + | --- freetype-2.4.1/src/cff/cffgload.c 2010-07-15 09:26:45.000000000 -0700 |
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| + | @@ -204,7 +204,7 @@ |
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| + | 2, /* hsbw */ |
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| + | 0, |
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| + | 0, |
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| + | - 0, |
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| + | + 1, |
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| + | 5, /* seac */ |
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| + | 4, /* sbw */ |
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| + | 2 /* setcurrentpoint */ |
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| + | @@ -2041,6 +2041,9 @@ |
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| + | if ( Rand >= 0x8000L ) |
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| + | Rand++; |
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| + | |||
| + | + if ( args - stack >= CFF_MAX_OPERANDS ) |
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| + | + goto Stack_Overflow; |
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| + | + |
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| + | args[0] = Rand; |
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| + | seed = FT_MulFix( seed, 0x10000L - seed ); |
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| + | if ( seed == 0 ) |
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| + | @@ -2166,6 +2169,9 @@ |
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| + | case cff_op_dup: |
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| + | FT_TRACE4(( " dup\n" )); |
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| + | |||
| + | + if ( args + 1 - stack >= CFF_MAX_OPERANDS ) |
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| + | + goto Stack_Overflow; |
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| + | + |
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| + | args[1] = args[0]; |
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| + | args += 2; |
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| + | break; |
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[[Category:Exploits]] |
[[Category:Exploits]] |
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Revision as of 19:12, 12 October 2010
This vulnerability, along with the IOSurface Kernel Exploit, was used in Star/JailbreakMe 2.0. It is a stack overflow in the handling of CFF opcodes. Contrary to popular belief, it is not a problem with the PDF parser, although the malformed font was placed in a PDF for exploitation.
Credit
exploit
diff -u -r freetype-2.4.1/src/cff/cffgload.c freetype-2.4.1_patched/src/cff/cffgload.c
--- freetype-2.4.1/src/cff/cffgload.c 2010-07-15 09:26:45.000000000 -0700
@@ -204,7 +204,7 @@
2, /* hsbw */
0,
0,
- 0,
+ 1,
5, /* seac */
4, /* sbw */
2 /* setcurrentpoint */
@@ -2041,6 +2041,9 @@
if ( Rand >= 0x8000L )
Rand++;
+ if ( args - stack >= CFF_MAX_OPERANDS )
+ goto Stack_Overflow;
+
args[0] = Rand;
seed = FT_MulFix( seed, 0x10000L - seed );
if ( seed == 0 )
@@ -2166,6 +2169,9 @@
case cff_op_dup:
FT_TRACE4(( " dup\n" ));
+ if ( args + 1 - stack >= CFF_MAX_OPERANDS )
+ goto Stack_Overflow;
+
args[1] = args[0];
args += 2;
break;
