├── .gitignore ├── CMakeLists.txt ├── LICENSE ├── README.md ├── lzp.c ├── lzp.h └── s7unpack.c /.gitignore: -------------------------------------------------------------------------------- 1 | # Prerequisites 2 | *.d 3 | 4 | # Object files 5 | *.o 6 | *.ko 7 | *.obj 8 | *.elf 9 | 10 | # Linker output 11 | *.ilk 12 | *.map 13 | *.exp 14 | 15 | # Precompiled Headers 16 | *.gch 17 | *.pch 18 | 19 | # Libraries 20 | *.lib 21 | *.a 22 | *.la 23 | *.lo 24 | 25 | # Shared objects (inc. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # s7unpack 2 | 3 | Unpacker for Siemens S7 1200 PLC firmware 4 | 5 | This tool was developed during the security analysis of Siemens PLCs I performed in 2015. 6 | 7 | Work has been presented at: 8 | 9 | - SSTIC 2015: [Analyse de sécurité de technologies propriétaires SCADA](https://www.sstic.org/2015/presentation/analyse_de_scurite_de_technologies_propritaires_scada/) 10 | - HITB Amsterdam 2015: [Supervising the Supervisor: Reversing Proprietary SCADA Tech](https://conference.hitb.org/hitbsecconf2015ams/sessions/reversing-proprietary-scada-tech/) 11 | 12 | Compression algorithm has been fully reverse engineered in black box, from a compressed firmware image. 13 | -------------------------------------------------------------------------------- /lzp.c: -------------------------------------------------------------------------------- 1 | // Copyright 2018 Jean-Baptiste Bédrune 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #include "lzp.h" 16 | #include 17 | #include 18 | #include 19 | #include 20 | 21 | #define LZP_ORDER 4 22 | 23 | static unsigned int *hash_table = NULL; 24 | static bool lzp_initialized = false; 25 | 26 | static unsigned int hash_index(unsigned int c) { 27 | unsigned int h; 28 | 29 | c = __builtin_bswap32(c); 30 | h = ((c >> 15u) ^ c) & 0xffffu; 31 | return h; 32 | } 33 | 34 | size_t lzp_unpack(const uint8_t *input_data, size_t input_size, 35 | uint8_t *output_data, size_t output_size) { 36 | unsigned int written, read; 37 | unsigned int mask; 38 | unsigned char b; 39 | int i, j; 40 | int pos; 41 | unsigned int c; 42 | unsigned int h; 43 | uint8_t *p; 44 | 45 | written = 0; 46 | read = 0; 47 | 48 | memset(output_data, 0, output_size); 49 | 50 | p = output_data; 51 | 52 | for (i = 0; i < LZP_ORDER; i++) { 53 | *p++ = input_data[read++]; 54 | written++; 55 | } 56 | 57 | c = *(uint32_t *)(output_data - LZP_ORDER); 58 | h = hash_index(c); 59 | hash_table[h] = written; 60 | 61 | while ((written < output_size) && (read < input_size)) { 62 | mask = input_data[read++]; 63 | for (i = 0; i < 8; i++) { 64 | b = input_data[read++]; 65 | 66 | if (!(mask & 0x80u)) { 67 | // literals. update dictionary 68 | c = *(uint32_t *)(p - LZP_ORDER); 69 | h = hash_index(c); 70 | hash_table[h] = written; 71 | 72 | *p++ = b; 73 | written++; 74 | 75 | if (written == output_size) 76 | goto done; 77 | } else { 78 | // match. read dictionary 79 | c = *(uint32_t *)(p - LZP_ORDER); 80 | h = hash_index(c); 81 | pos = hash_table[h]; 82 | hash_table[h] = written; 83 | 84 | for (j = 0; j < b; j++) { 85 | *p++ = output_data[pos + j]; 86 | written += 1; 87 | 88 | if (written == output_size) { 89 | goto done; 90 | } 91 | } 92 | } 93 | 94 | mask <<= 1; 95 | } 96 | } 97 | done: 98 | return written; 99 | } 100 | 101 | bool lzp_init() { 102 | if (!lzp_initialized) { 103 | hash_table = malloc(sizeof(unsigned int) * 0x10000); 104 | if (hash_table == NULL) { 105 | return false; 106 | } 107 | lzp_initialized = true; 108 | } 109 | 110 | for (int i = 0; i < 0x10000; i++) { 111 | hash_table[i] = ~0u; 112 | ; 113 | } 114 | return true; 115 | } 116 | 117 | void lzp_destroy() { 118 | if (lzp_initialized) { 119 | free(hash_table); 120 | lzp_initialized = false; 121 | } 122 | } 123 | -------------------------------------------------------------------------------- /lzp.h: -------------------------------------------------------------------------------- 1 | // Copyright 2018 Jean-Baptiste Bédrune 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #ifndef S7UNPACK_LZP_H 16 | #define S7UNPACK_LZP_H 17 | 18 | #include 19 | #include 20 | #include 21 | 22 | #define LZP_CHUNK_SIZE 0x10000 23 | 24 | bool lzp_init(); 25 | void lzp_destroy(); 26 | size_t lzp_unpack(const uint8_t *input_data, size_t input_size, 27 | uint8_t *output_data, size_t output_size); 28 | 29 | #endif // S7UNPACK_LZP_H 30 | -------------------------------------------------------------------------------- /s7unpack.c: -------------------------------------------------------------------------------- 1 | // Copyright 2018 Jean-Baptiste Bédrune 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #include "lzp.h" 16 | #include 17 | #include 18 | #include 19 | 20 | #define FW_HEADER_SIZE 0x2c 21 | #define FW_NUM_ENTRIES 4 22 | #define FW_ENTRY_NAME_SIZE 6 23 | 24 | typedef struct { 25 | uint32_t size; 26 | uint32_t crc; 27 | char name[FW_ENTRY_NAME_SIZE]; 28 | } __attribute__((packed)) fw_raw_entry; 29 | 30 | typedef struct { 31 | long offset; 32 | uint32_t size; 33 | uint32_t crc; 34 | char name[FW_ENTRY_NAME_SIZE + 1]; 35 | } fw_entry; 36 | 37 | static bool get_firmware_entry(FILE *f, const char *name, fw_entry *entry) { 38 | long offset = FW_HEADER_SIZE + FW_NUM_ENTRIES * sizeof(fw_raw_entry); 39 | fw_raw_entry raw_entry; 40 | 41 | fseek(f, FW_HEADER_SIZE, SEEK_SET); 42 | for (int i = 0; i < FW_NUM_ENTRIES; i++) { 43 | if (fread(&raw_entry, 1, sizeof(fw_raw_entry), f) != sizeof(fw_raw_entry)) { 44 | return false; 45 | } 46 | 47 | if (memcmp(raw_entry.name, name, sizeof(raw_entry.name)) == 0) { 48 | entry->offset = offset; 49 | entry->size = raw_entry.size; 50 | entry->crc = raw_entry.crc; 51 | memcpy(entry->name, raw_entry.name, sizeof(raw_entry.name)); 52 | entry->name[sizeof(raw_entry.name)] = 0; 53 | 54 | return true; 55 | } 56 | offset += raw_entry.size + sizeof(raw_entry.name); 57 | } 58 | return false; 59 | } 60 | 61 | int main(int argc, char *argv[]) { 62 | FILE *in_file, *out_file; 63 | uint8_t *compressed_chunk = NULL, *output_chunk; 64 | fw_entry entry; 65 | char section_name[6]; 66 | size_t read_bytes, output_size; 67 | 68 | if (argc < 3) { 69 | printf("Usage: %s \n", argv[0]); 70 | return 1; 71 | } 72 | 73 | in_file = fopen(argv[1], "rb"); 74 | if (in_file == NULL) { 75 | printf("Cannot open input file\n"); 76 | return 0; 77 | } 78 | 79 | if (!get_firmware_entry(in_file, "A00000", &entry)) { 80 | printf("Cannot find firmware code.\n"); 81 | return 1; 82 | } 83 | 84 | fseek(in_file, entry.offset, SEEK_SET); 85 | if (fread(section_name, 1, FW_ENTRY_NAME_SIZE, in_file) != 86 | FW_ENTRY_NAME_SIZE || 87 | memcmp(section_name, "A00000", FW_ENTRY_NAME_SIZE) != 0) { 88 | fprintf(stderr, "Invalid section header.\n"); 89 | return 1; 90 | } 91 | 92 | out_file = fopen(argv[2], "wb"); 93 | if (out_file == NULL) { 94 | printf("Cannot open output_chunk file\n"); 95 | return 0; 96 | } 97 | 98 | lzp_init(); 99 | 100 | read_bytes = 0; 101 | output_chunk = (unsigned char *)malloc(LZP_CHUNK_SIZE); 102 | if (output_chunk == NULL) { 103 | fprintf(stderr, "Memory error\n"); 104 | return 1; 105 | } 106 | while (read_bytes < entry.size) { 107 | uint32_t compressed_size; 108 | 109 | if (fread(&compressed_size, sizeof(uint32_t), 1, in_file) != 1) 110 | break; 111 | 112 | compressed_chunk = realloc(compressed_chunk, compressed_size); 113 | if (fread(compressed_chunk, 1, compressed_size, in_file) != 114 | compressed_size) { 115 | break; 116 | } 117 | output_size = lzp_unpack(compressed_chunk + 2, compressed_size - 2, 118 | output_chunk, LZP_CHUNK_SIZE); 119 | 120 | fwrite(output_chunk, 1, output_size, out_file); 121 | 122 | read_bytes += compressed_size + sizeof(uint32_t); 123 | } 124 | 125 | if (read_bytes == entry.size) { 126 | printf("Firmware successfully unpacked\n"); 127 | } else { 128 | printf("Error occurred during decompression\n"); 129 | } 130 | free(compressed_chunk); 131 | lzp_destroy(); 132 | 133 | fclose(in_file); 134 | fclose(out_file); 135 | return 0; 136 | } 137 | --------------------------------------------------------------------------------