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
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
|
#include "frida-gumjs.h"
#include "config.h"
#include "instrument.h"
#include "persistent.h"
#include "util.h"
#if defined(__i386__)
typedef struct {
GumCpuContext ctx;
uint32_t eflags;
} persistent_ctx_t;
static persistent_ctx_t saved_regs = {0};
static gpointer persistent_loop = NULL;
gboolean persistent_is_supported(void) {
return true;
}
static void instrument_persitent_save_regs(GumX86Writer *cw,
persistent_ctx_t *regs) {
GumAddress regs_address = GUM_ADDRESS(regs);
/* Should be pushing FPU here, but meh */
gum_x86_writer_put_pushfx(cw);
gum_x86_writer_put_push_reg(cw, GUM_X86_EAX);
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EAX, regs_address);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, ebx), GUM_X86_EBX);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, ecx), GUM_X86_ECX);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, edx), GUM_X86_EDX);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, edi), GUM_X86_EDI);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, esi), GUM_X86_ESI);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, ebp), GUM_X86_EBP);
/* Store RIP */
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EBX,
GUM_ADDRESS(persistent_start));
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, eip), GUM_X86_EBX);
/* Store adjusted RSP */
gum_x86_writer_put_mov_reg_reg(cw, GUM_X86_EBX, GUM_X86_ESP);
/* RED_ZONE + Saved flags, RAX */
gum_x86_writer_put_add_reg_imm(cw, GUM_X86_EBX, (0x4 * 2));
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, esp), GUM_X86_EBX);
/* Save the flags */
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_ESP, 0x4);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(persistent_ctx_t, eflags), GUM_X86_EBX);
/* Save the RAX */
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_ESP, 0x0);
gum_x86_writer_put_mov_reg_offset_ptr_reg(
cw, GUM_X86_EAX, offsetof(GumCpuContext, eax), GUM_X86_EBX);
/* Pop the saved values */
gum_x86_writer_put_lea_reg_reg_offset(cw, GUM_X86_ESP, GUM_X86_ESP, 0x8);
}
static void instrument_persitent_restore_regs(GumX86Writer *cw,
persistent_ctx_t *regs) {
GumAddress regs_address = GUM_ADDRESS(regs);
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EAX, regs_address);
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_ECX, GUM_X86_EAX,
offsetof(GumCpuContext, ecx));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EDX, GUM_X86_EAX,
offsetof(GumCpuContext, edx));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EDI, GUM_X86_EAX,
offsetof(GumCpuContext, edi));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_ESI, GUM_X86_EAX,
offsetof(GumCpuContext, esi));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBP, GUM_X86_EAX,
offsetof(GumCpuContext, ebp));
/* Don't restore RIP */
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_ESP, GUM_X86_EAX,
offsetof(GumCpuContext, esp));
/* Restore RBX, RAX & Flags */
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_EAX,
offsetof(GumCpuContext, ebx));
gum_x86_writer_put_push_reg(cw, GUM_X86_EBX);
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_EAX,
offsetof(GumCpuContext, eax));
gum_x86_writer_put_push_reg(cw, GUM_X86_EBX);
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_EAX,
offsetof(persistent_ctx_t, eflags));
gum_x86_writer_put_push_reg(cw, GUM_X86_EBX);
gum_x86_writer_put_popfx(cw);
gum_x86_writer_put_pop_reg(cw, GUM_X86_EAX);
gum_x86_writer_put_pop_reg(cw, GUM_X86_EBX);
}
static void instrument_afl_persistent_loop_func(void) {
if (__afl_persistent_loop(persistent_count) == 0) { _exit(0); };
if (instrument_previous_pc_addr == NULL) {
FATAL("instrument_previous_pc_addr uninitialized");
}
*instrument_previous_pc_addr = instrument_hash_zero;
}
static void instrument_afl_persistent_loop(GumX86Writer *cw) {
gum_x86_writer_put_call_address_with_arguments(
cw, GUM_CALL_CAPI, GUM_ADDRESS(instrument_afl_persistent_loop_func), 0);
}
static void persistent_prologue_hook(GumX86Writer *cw, persistent_ctx_t *regs) {
if (persistent_hook == NULL) return;
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_ECX,
GUM_ADDRESS(&__afl_fuzz_len));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_ECX, GUM_X86_ECX, 0);
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_ECX, GUM_X86_ECX, 0);
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EDX,
GUM_ADDRESS(&__afl_fuzz_ptr));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EDX, GUM_X86_EDX, 0);
/* Base address is 64-bits (hence two zero arguments) */
gum_x86_writer_put_call_address_with_arguments(
cw, GUM_CALL_CAPI, GUM_ADDRESS(persistent_hook), 3, GUM_ARG_ADDRESS,
GUM_ADDRESS(®s->ctx), GUM_ARG_REGISTER, GUM_X86_EDX, GUM_ARG_REGISTER,
GUM_X86_ECX);
}
static void instrument_persitent_save_ret(GumX86Writer *cw) {
/* Stack usage by this function */
gssize offset = (3 * 4);
gum_x86_writer_put_pushfx(cw);
gum_x86_writer_put_push_reg(cw, GUM_X86_EAX);
gum_x86_writer_put_push_reg(cw, GUM_X86_EBX);
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EAX,
GUM_ADDRESS(&persistent_ret));
gum_x86_writer_put_mov_reg_reg_offset_ptr(cw, GUM_X86_EBX, GUM_X86_ESP,
offset);
gum_x86_writer_put_mov_reg_ptr_reg(cw, GUM_X86_EAX, GUM_X86_EBX);
gum_x86_writer_put_pop_reg(cw, GUM_X86_EBX);
gum_x86_writer_put_pop_reg(cw, GUM_X86_EAX);
gum_x86_writer_put_popfx(cw);
}
void persistent_prologue_arch(GumStalkerOutput *output) {
/*
* SAVE RET (Used to write the epilogue if persistent_ret is not set)
* SAVE REGS
* loop: (Save address of where the eiplogue should jump back to)
* CALL instrument_afl_persistent_loop
* CALL hook (optionally)
* RESTORE REGS
* INSTRUMENTED PERSISTENT FUNC
*/
GumX86Writer *cw = output->writer.x86;
FVERBOSE("Persistent loop reached");
/*
* If we haven't set persistent_ret, then assume that we are dealing with a
* function and we should loop when that function returns.
*/
if (persistent_ret == 0) { instrument_persitent_save_ret(cw); }
/* Save the current context */
instrument_persitent_save_regs(cw, &saved_regs);
/* Store a pointer to where we should return for our next iteration */
persistent_loop = gum_x86_writer_cur(cw);
/* call __afl_persistent_loop and _exit if zero. Also reset our previous_pc */
instrument_afl_persistent_loop(cw);
/* Optionally call the persistent hook */
persistent_prologue_hook(cw, &saved_regs);
/* Restore our CPU context before we continue execution */
instrument_persitent_restore_regs(cw, &saved_regs);
if (persistent_debug) { gum_x86_writer_put_breakpoint(cw); }
/* The original instrumented code is emitted here. */
}
void persistent_epilogue_arch(GumStalkerOutput *output) {
GumX86Writer *cw = output->writer.x86;
if (persistent_debug) { gum_x86_writer_put_breakpoint(cw); }
/* The stack should be aligned when we re-enter our loop */
gum_x86_writer_put_and_reg_u32(cw, GUM_X86_ESP, 0xfffffff0);
gum_x86_writer_put_sub_reg_imm(cw, GUM_X86_ESP, 0x4);
gum_x86_writer_put_mov_reg_address(cw, GUM_X86_EAX,
GUM_ADDRESS(&persistent_loop));
gum_x86_writer_put_jmp_reg_ptr(cw, GUM_X86_EAX);
}
#endif
|
