1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
% ----------------------------
\subsubsection{Exploits}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Exploit Types}
\begin{itemize}
\item Application Level Exploits
\begin{itemize}
\item SQL Injection
\item Cross-side scripting
\item Backdoors
\item Protocol Implementation
\item \dots
\end{itemize}
\item Low-Level Exploits
\begin{itemize}
\item Stack
\item Heap
\item Syscall
\item Race conditions
\end{itemize}
\end{itemize}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack: Code Example I}
\begin{beamerboxesrounded}[shadow=true]{Bad copy to stack local buffer}
\begin{tiny}
\begin{verbatim}
#include <string.h>
void foo (char *p) {
char buf[16];
strcpy(buf, p);
}
int main (int argc, char **argv) {
foo(argv[1]);
}
\end{verbatim}
\end{tiny}
\end{beamerboxesrounded}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack: Code Example II}
\begin{beamerboxesrounded}[shadow=true]{Manipulation of return address}
\begin{tiny}
\begin{verbatim}
#include <stdio.h>
#include <string.h>
void function(int a, int b, int c)
{
char buffer1[8];
char buffer2[16];
char *ret;
ret = (char *)(buffer1 + 0x18);
(*ret) += 0x7;
}
void main(void)
{
int x;
x = 0;
function(1,2,3);
x = 1;
printf("%d\n",x);
}
\end{verbatim}
\end{tiny}
\end{beamerboxesrounded}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack: Layout I}
\begin{figure}[h]
\centering
\includegraphics[width=8cm]{images/em_stack_layout1.png}
\end{figure}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack}
\begin{itemize}
\item Overwrite return address
\item change stack-local variables
\item inject malicious code
\begin{itemize}
\item shell code
\item backdoors
\item thread hijacking
\end{itemize}
\end{itemize}
\end{frame}
% ----------------------------
\subsubsection{Mitigation}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Address Space Layout}
\begin{itemize}
\item Fixed layout of segment start addresses
\item Easy to exploit
\item Address Space Layout Randomization
\begin{itemize}
\item basic implementation (Linux v2.6.12)
\item full implementation (Linux v3.19)
\end{itemize}
\item Configuration: /proc/sys/kernel/randomize\_va\_space
\begin{itemize}
\item 0: Disabled
\item 1: randomize stack, data, dynamic libraries
\item 2: randomize stack, data, dynamic libraries, heap
\end{itemize}
\item Process maps: /proc/<pid>/maps
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Process Memory Map}
\begin{beamerboxesrounded}[shadow=true]{/proc/<pid>/maps}
\begin{tiny}
\begin{verbatim}
$ cat /proc/self/maps
00400000-0040c000 r-xp 00000000 fe:00 23360017 /bin/cat
0060b000-0060c000 r--p 0000b000 fe:00 23360017 /bin/cat
0060c000-0060d000 rw-p 0000c000 fe:00 23360017 /bin/cat
0060d000-0062e000 rw-p 00000000 00:00 0 [heap]
7ffff7a31000-7ffff7bd3000 r-xp 00000000 fe:00 2359536 /lib/x86_64-linux-gnu/libc-2.19.so
7ffff7bd3000-7ffff7dd2000 ---p 001a2000 fe:00 2359536 /lib/x86_64-linux-gnu/libc-2.19.so
7ffff7dd2000-7ffff7dd6000 r--p 001a1000 fe:00 2359536 /lib/x86_64-linux-gnu/libc-2.19.so
7ffff7dd6000-7ffff7dd8000 rw-p 001a5000 fe:00 2359536 /lib/x86_64-linux-gnu/libc-2.19.so
7ffff7dd8000-7ffff7ddc000 rw-p 00000000 00:00 0
7ffff7ddc000-7ffff7dfc000 r-xp 00000000 fe:00 2359533 /lib/x86_64-linux-gnu/ld-2.19.so
7ffff7e09000-7ffff7fce000 r--p 00000000 fe:00 3932237 /usr/lib/locale/locale-archive
7ffff7fce000-7ffff7fd1000 rw-p 00000000 00:00 0
7ffff7fd4000-7ffff7ff8000 rw-p 00000000 00:00 0
7ffff7ff8000-7ffff7ffa000 r-xp 00000000 00:00 0 [vdso]
7ffff7ffa000-7ffff7ffc000 r--p 00000000 00:00 0 [vvar]
7ffff7ffc000-7ffff7ffd000 r--p 00020000 fe:00 2359533 /lib/x86_64-linux-gnu/ld-2.19.so
7ffff7ffd000-7ffff7ffe000 rw-p 00021000 fe:00 2359533 /lib/x86_64-linux-gnu/ld-2.19.so
7ffff7ffe000-7ffff7fff000 rw-p 00000000 00:00 0
7ffffffde000-7ffffffff000 rw-p 00000000 00:00 0 [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
\end{verbatim}
\end{tiny}
\end{beamerboxesrounded}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack Protect}
\begin{itemize}
\item Canaries
\begin{itemize}
\item Compiler Support (gcc)
\begin{itemize}
\item -fno-stack-protector
\item -fstack-protector
\item -fstack-protector-all
\item -fstack-protector-strong (since gcc v4.9)
\end{itemize}
\end{itemize}
\begin{itemize}
\item Kernel Configuration
\begin{itemize}
\item CONFIG\_CC\_STACKPROTECTOR\_NONE
\item CONFIG\_CC\_STACKPROTECTOR\_REGULAR \\
(coverage: 2.81 \%, code size: +0.33 \% )
\item CONFIG\_CC\_STACKPROTECTOR\_STRONG \\
(coverage: 20.5 \%, code size: +2.4 \% )
\end{itemize}
\end{itemize}
\item Stack order randomization
\end{itemize}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Stack Canaries: Stack layout}
\begin{figure}[h]
\centering
\includegraphics[width=6cm]{images/em_stack_layout2.png}
\end{figure}
\end{frame}
% ----------------------------
\begin{frame}[fragile]
\frametitle{Hardware-based}
\begin{itemize}
\item NX (no execute flag for pages)
\begin{itemize}
\item No Execute Flag for pages (PTE)
\item Architectures: x86, PPC, S390, ARM (some)
\end{itemize}
\item MPX (Boundary Protection)
\begin{itemize}
\item Architecture: x86
\item high performance impact
\item test only
\end{itemize}
\end{itemize}
\end{frame}
% % ----------------------------
\begin{frame}[fragile]
\frametitle{grsecurity}
\begin{itemize}
\item Security enhancement
\item Kernel patches (PAX)
\item Role-based access control
\item Thread isolation
\item Container isolation
\item BPF JIT enhancements
\item Return Address Protection (GCC)
\end{itemize}
\end{frame}
|
