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30 caddr_t data = "\xff\xff\xff\xff";31 int t = 0;3233 t = *(int *)data;3435 printf ("Bit pattern of t: ");36 bitpattern (t);3738 printf ("t = %d (0x%08x)\n", t, t);3940 return 0;41 }Listing 7-1: Example program that demonstrates the type conversion behavior (conversion_bug_example.c)Lines 30, 31, and 33 are nearly identical to lines in the OS Xkernel source code. In this example, I chose the hardcoded value0xffffffff as IOCTL input data (see line 30). After the type conversionin line 33, the bit patterns, as well as the decimal value of t, areprinted to the console. The example program results in the followingoutput when it’s executed:osx$ gcc -o conversion_bug_example conversion_bug_example.cosx$ ./conversion_bug_exampleBit pattern of t: 1111 1111 1111 1111 1111 1111 1111 1111t = -1 (0xffffffff)The output shows that t gets the value –1 if a character stringconsisting of 4 0xff byte values is converted into a signed int. See SectionA.3 for more information on type conversions and the associatedsecurity problems.If t is negative, the check in line 1093 of the kernel code will returnFALSE because the signed int variable nlinesw has a value greater thanzero. If that happens, the user-supplied value of t gets further processing.In line 1098, the value of t is used as an index into an arrayof function pointers. Since I could control the index into that array,I could specify an arbitrary memory location that would be executedby the kernel. This leads to full control of the kernel execution flow.Thank you, Apple, for the terrific bug. ☺Here is the anatomy of the bug, as diagrammed in Figure 7-1:1. The function pointer array linesw[] gets referenced.2. The user-controlled value of t is used as an array index forlinesw[].3. A pointer to the assumed address of the l_open() function getsreferenced based on the user-controllable memory location.118 Chapter 7
4. The assumed address of l_open() gets referenced and called.5. The value at the assumed address of l_open() gets copied into theinstruction pointer (EIP register).0xFFFFFFFFKernel(3)(4)(2)(1)(5)linesw[t].l_openEIP0x00000000Figure 7-1: Description of the vulnerability that I discovered in theXNU kernel of OS XBecause the value of t is supplied by the user (see (2)), it is possibleto control the address of the value that gets copied into EIP.7.2 ExploitationAfter I found the bug, I did the following to gain control over EIP:• Step 1: Trigger the bug to crash the system (denial of service).• Step 2: Prepare a kernel-debugging environment.• Step 3: Connect the debugger to the target system.• Step 4: Get control over EIP.Step 1: Trigger the <strong>Bug</strong> to Crash the System (Denial of Service)Once I had found the bug, it was easy to trigger it and cause a systemcrash. All I had to do was send a malformed TIOCSETD IOCTL requestto the kernel. Listing 7-2 shows the source code of the POC I developedto cause a crash.A <strong>Bug</strong> Older Than 4.4BSD 119
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A Bug Hunter’s Diary. Copyright
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Chapter 3: Escape from the WWW Zone
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B.2 The Windows Debugger (WinDbg) .
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IntroductionWelcome to A Bug Hunter
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1Bug HuntingBug hunting is the proc
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After I’ve found a bug, I want to
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Table 1-1: Debuggers Used in This B
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2Back to the ’90sSunday, October
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16361637 /* clear the SEQ table */1
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If a TiVo file is loaded by VLC, th
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Get the →vulnerableWindows versio
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EIP = 41414141 . . . Mission EIP co
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NoteTo configure Process Explorer t
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See the following excerpt from the
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3. Immunity Debugger is a great Win
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NoteInput/output controls (IOCTLs)
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msgbb_datapdatabb_rptrdb_basedatabu
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8180 /*8181 * Null terminate the st
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26736 /*26737 * SIOC[GS]TUNPARAM ap
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19165 * are also rejected as they i
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01 #include 02 #include 03 #include
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fffffe8000f7e4b0 unix:die+da ()ffff
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zero pagenot mappedzero pageis mapp
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gaining full control over EIP/RIP a
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112 return 1;113 }114115 printf ("O
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solaris$ isainfo -b64I then compile
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ip_output+0x10()ip_wput+0x37()putne
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Notes1. The source code of OpenSola
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4.1 Vulnerability DiscoveryTo find
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167 if (current_track + 1 > fourxm-
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Step 1: Find a Sample 4X Movie File
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Next, I modified the values of trac
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Table 4-2: List of the Assembler In
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63 #elif defined (HAVE_MEMALIGN)64
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linux$ gdb -q ./ffmpeg_g(gdb) run -
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Page 85 and 86: 5Browse and You’re OwnedSunday, A
Page 87 and 88: {SWI.ClassId_q.ClassId clsid = new
Page 89 and 90: 27 except KeyboardInterrupt:28 prin
Page 91 and 92: Figure 5-4: Defining a breakpoint a
Page 93 and 94: Figure 5-7: User-controlled argumen
Page 95 and 96: Next, I tried to retrieve the size
Page 97 and 98: 05 06 arg = String(232, "A") + Stri
Page 99: iDefense VCPnotifiedVulnerability d
Page 102 and 103: 6.1 Vulnerability DiscoveryI used t
Page 104 and 105: Step 3: Check the Device Security S
Page 106 and 107: Below, the elements of the MajorFun
Page 108 and 109: At address .text:00010748, a pointe
Page 110 and 111: [..][..]//// Current stack location
Page 112 and 113: The transfer type is specified usin
Page 114 and 115: If the requested IOCTL code matches
Page 116 and 117: Figure 6-5: Graph view of the vulne
Page 118 and 119: .text:00010DBA push 1 ; _DWORD.text
Page 120 and 121: 99 // .text:00010DEF cmp dword ptr
Page 122 and 123: nt!RtlpBreakWithStatusInstruction:8
Page 124 and 125: After I gained control over EIP, I
Page 127 and 128: 7A Bug Older Than 4.4BSDSaturday, M
Page 129 and 130: Here are some examples:Source code
Page 131: 1094 return (ENXIO);1095 if (t != t
Page 135 and 136: osx$ cat /Library/Logs/panic.logSat
Page 137 and 138: Back on the Linux host, I started t
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Page 141 and 142: 48 define search_memloc49 set $max_
Page 143 and 144: As the debugger output shows, the E
Page 145: ApplenotifiedApple asks formore det
Page 148 and 149: I performed the following steps whe
Page 150 and 151: I then began fuzzing files of the A
Page 152 and 153: Figure 8-1: Playing the unmodifiedA
Page 154 and 155: • Line 40 copies the current proc
Page 156 and 157: As the debugger output shows, media
Page 158 and 159: The manipulated byte (0xff) that ca
Page 160 and 161: (gdb) x/12x 0x1301bfc0x1301bfc: 0x0
Page 162 and 163: ApplenotifiedApple confirmsthe vuln
Page 164 and 165: Every function of a process that is
Page 166 and 167: eip 0x43434343 0x43434343eflags 0x1
Page 168 and 169: The access violation is caused when
Page 170 and 171: is less than 12. If it is, the stri
Page 172 and 173: The program in Listing A-4 calls th
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Page 177 and 178: BDebuggingThis appendix contains in
Page 179 and 180: Information CommandsCommandDescript
Page 181 and 182: Information CommandsCommandrkbu add
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Figure B-3: Configuration settings
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Figure B-6: Attaching the kernel de
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Other CommandsCommandset disassembl
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linux# pwd/home/tk/gdb-292/srclinux
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Notes1. See the Solaris Modular Deb
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The many mitigation techniques coul
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Figure C-1: DEP and ASLR status sho
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08 p[0] = 0x41414141;09 printf (“
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ConclusionIn case of a buffer overf
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zonecfg:wwwzone> set autoboot=truez
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Notes1. See Rob King, “New Leopar
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COMRaider, 72coordinated disclosure
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Rreadelf, 161RELRO, 67-69, 183-186r
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A Bug Hunter’s Diary is set in Ne
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