initial commit. just the decrypt tool so far
This commit is contained in:
commit
8629a3988a
25
.gitignore
vendored
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25
.gitignore
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*.o
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*.exe
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*.so
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*.dylib
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*.dSYM
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*.a
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/build
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# CMake
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/cmake-build-debug
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/cmake-build-release
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CMakeLists.txt.user
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CMakeCache.txt
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CMakeFiles
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CMakeScripts
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Testing
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Makefile
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cmake_install.cmake
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install_manifest.txt
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compile_commands.json
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CTestTestfile.cmake
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_deps
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# IDE stuff
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/.idea
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CMakeLists.txt
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CMakeLists.txt
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cmake_minimum_required(VERSION 3.16)
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project(psogc_quest_tools C)
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set(CMAKE_C_STANDARD 99)
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include_directories(/usr/local/include)
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find_library(SYLVERANT_LIBRARY sylverant REQUIRED)
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# decrypt_packets
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add_executable(decrypt_packets decrypt_packets/main.c)
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target_link_libraries(decrypt_packets ${SYLVERANT_LIBRARY})
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100
decrypt_packets/README.md
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decrypt_packets/README.md
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# PSO Ep 1 & 2 (Gamecube) Client/Server Packets Decrypter Tool
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This is a tool that will take raw binary PSO client and server packet data dumps generated from a packet capture tool
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(such as Wireshark) and display the decrypted packet data.
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I put this tool together for myself to help further my understanding of PSO's network communication. More specifically,
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to help me troubleshoot why my attempts at setting up Sylverant's open source [login_server](https://github.com/Sylverant/login_server)
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to serve up quests for download was resulting in unusable quest files on Gamecube memory cards. Understanding the
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quest download communication better by analyzing the packets being sent from a working implementation and comparing it
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to what my local login_server instance was sending proved invaluable to me.
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## Network Protocol
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After the initial `0x17` packet sent from the server to the client (which contains the client and server encryption
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keys), all subsequent communication between the server and client is encrypted. When you have the full set of packets,
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beginning with the `0x17` packet, it is pretty trivial to decrypt the entire set of data.
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```text
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'Welcome' packet. id=17, flags=0, size=276
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0000 | 17 00 14 01 44 72 65 61 6D 43 61 73 74 20 50 6F | ....DreamCast Po
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0010 | 72 74 20 4D 61 70 2E 20 43 6F 70 79 72 69 67 68 | rt Map. Copyrigh
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0020 | 74 20 53 45 47 41 20 45 6E 74 65 72 70 72 69 73 | t SEGA Enterpris
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0030 | 65 73 2E 20 31 39 39 39 00 00 00 00 00 00 00 00 | es. 1999........
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0040 | 00 00 00 00 6B 81 4B 4F 01 A2 65 78 54 68 69 73 | ....k.KO..exThis
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0050 | 20 73 65 72 76 65 72 20 69 73 20 69 6E 20 6E 6F | server is in no
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0060 | 20 77 61 79 20 61 66 66 69 6C 69 61 74 65 64 2C | way affiliated,
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0070 | 20 73 70 6F 6E 73 6F 72 65 64 2C 20 6F 72 20 73 | sponsored, or s
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0080 | 75 70 70 6F 72 74 65 64 20 62 79 20 53 45 47 41 | upported by SEGA
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0090 | 20 45 6E 74 65 72 70 72 69 73 65 73 20 6F 72 20 | Enterprises or
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00A0 | 53 4F 4E 49 43 54 45 41 4D 2E 20 54 68 65 20 70 | SONICTEAM. The p
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00B0 | 72 65 63 65 64 69 6E 67 20 6D 65 73 73 61 67 65 | receding message
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00C0 | 20 65 78 69 73 74 73 20 6F 6E 6C 79 20 69 6E 20 | exists only in
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00D0 | 6F 72 64 65 72 20 74 6F 20 72 65 6D 61 69 6E 20 | order to remain
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00E0 | 63 6F 6D 70 61 74 69 62 6C 65 20 77 69 74 68 20 | compatible with
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00F0 | 70 72 6F 67 72 61 6D 73 20 74 68 61 74 20 65 78 | programs that ex
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0100 | 70 65 63 74 20 69 74 2E 00 00 00 00 00 00 00 00 | pect it.........
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0110 | 00 00 00 00 | ....
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server_key = 0x4f4b816b
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client_key = 0x7865a201
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```
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Note, sometimes the `0x17` packet will contain significantly less text than what is shown above. The above output is
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from a Fuzziqer [newserv](https://github.com/fuzziqersoftware/newserv) I was testing with.
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Also of note is that Sylverant's login_server currently seems to always use identical server and client keys (I believe
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this is a bug in libsylverant's usage of its random number generator library). This does not cause problems, but it is
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weird to see when you first notice it.
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Some relevant reading regarding PSO's network protocol:
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* [Network Protocol](http://web.archive.org/web/20171201191557/http://sharnoth.com/psodevwiki/net/protocol)
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* [Network Protocol Messages](http://web.archive.org/web/20171201191532/http://sharnoth.com/psodevwiki/net/messages)
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* ["Detailed" Message Flow](http://web.archive.org/web/20171201191527/http://sharnoth.com/psodevwiki/net/message_flow)
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Currently, [libsylverant](https://github.com/Sylverant/libsylverant) has the cleanest and easiest to use PSO encryption
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API, and that is what is used by this tool.
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**Note that the PSO encryption method (and thus, the `CRYPT_` API provided by libsylverant) is stateful**. That is, you
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cannot just use it to arbitrarily decrypt any single random packet and expect it to result in readable data. To
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correctly decrypt any individual packet from either client or server, you need to work through the full sequence of
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packets (for either client or server) beginning with the very first client or server packet (**after** the `0x17`
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packet) up to the packet(s) you really wanted, decrypting all of it along the way.
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## Usage
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### Capturing Packets from PSO
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This is probably easiest if you already have Dolphin set up to run PSO with a working network configuration. In such
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a configuration, you can capture from your local computer right away.
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I do not have this set up and I cannot be bothered to figure out the janky "Tap" set up that Dolphin requires. Mostly
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because I am lazy. And because I have a router running [OpenWrt](https://openwrt.org/) which allows me to easily set up
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packet mirroring with a special iptables kernel module loaded so that I can capture packets directly from my Gamecube.
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I'm not going to go into details here on setting up either method. If you're knowledgeable enough to be considering
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doing packet capture analysis of any sort in the first place, then you should be able to set up either method yourself.
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### Dumping PSO Server/Client Communication Data Dumps with Wireshark
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It is easy to generate packet data dumps containing _just_ the PSO packet data we are interested in with Wireshark.
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After taking a capture of a PSO server/client session, find the TCP packet sent from the server to the client that
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contains the `0x17` packet. This should be easy enough to find as it will be one of the first TCP packets sent from the
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server to the client and contains the clear-text string `DreamCast Port Map. Copyright SEGA Enterprises. 1999` (for
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non-BB clients anyway, this tool is aimed at GC anyway so that is all I will be covering ...).
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Once you've found this packet, right-click it from the top packet list and select "Follow" then "TCP Stream". This will
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bring up a window that shows the raw data, colour-coded to show data originating from the client and server. Use the
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drop-downs and buttons at the bottom of this window to save "Raw"-format data for the client and server in
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**individual** files.
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### Decrypting
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Assuming you saved the data to two files, `server.bin` (containing server-to-client packets) and `client.bin`
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(containing client-to-server packets), you can run the tool like so:
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```text
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decrypt_packets /path/to/server.bin /path/to/client.bin
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```
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137
decrypt_packets/main.c
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137
decrypt_packets/main.c
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#include <stdio.h>
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#include <stdint.h>
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#include <string.h>
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#include <malloc.h>
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#include <sylverant/encryption.h>
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void* read_file(const char *filename, uint32_t *out_file_size) {
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if (!out_file_size)
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return NULL;
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FILE *fp = fopen(filename, "rb");
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if (!fp)
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return NULL;
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fseek(fp, 0, SEEK_END);
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*out_file_size = ftell(fp);
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fseek(fp, 0, SEEK_SET);
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uint8_t *result = malloc(*out_file_size);
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uint32_t read, next;
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uint8_t buffer[1024];
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next = 0;
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do {
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read = fread(buffer, 1, 1024, fp);
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if (read) {
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memcpy(&result[next], buffer, read);
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next += read;
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}
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} while (read);
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return result;
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}
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int main(int argc, char *argv[]) {
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if (argc != 3) {
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printf("Usage: pso_decrypt server-packet-data.bin client-packet-data.bin\n");
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return 1;
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}
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const char *server_packet_file = argv[1];
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const char *client_packet_file = argv[2];
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uint32_t server_data_size = 0;
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uint32_t client_data_size = 0;
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uint8_t *server_data = read_file(server_packet_file, &server_data_size);
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if (!server_data) {
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printf("Error reading server packet data file: %s\n", server_packet_file);
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return 1;
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}
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uint8_t *client_data = read_file(client_packet_file, &client_data_size);
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if (!client_data) {
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printf("Error reading client packet data file: %s\n", client_packet_file);
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free(server_data);
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return 1;
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}
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uint32_t pos;
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uint8_t pkt_id, pkt_flags;
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uint16_t pkt_size;
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uint32_t server_key, client_key;
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// read client & server crypt keys from the "Welcome" packet the server sends right away. always unencrypted.
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pos = 0;
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pkt_id = server_data[pos];
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pkt_flags = server_data[pos+1];
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pkt_size = *((uint16_t*)&server_data[pos+2]);
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printf("'Welcome' packet. id=%x, flags=%x, size=%d\n", pkt_id, pkt_flags, pkt_size);
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CRYPT_PrintData(&server_data[pos], pkt_size);
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printf("\n");
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// NOTE: sylverant login_server currently always has these identical to each other. fuzziqer does not exhibit this.
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// looks like a bug within libsylverant, or more specifically with it's custom random number generator lib?
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// either way, it does not pose a problem ...
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server_key = *((uint32_t*)&server_data[pos+68]);
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client_key = *((uint32_t*)&server_data[pos+72]);
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printf("server_key = 0x%x\nclient_key = 0x%x\n\n", server_key, client_key);
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pos += pkt_size;
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// set up crypt functionality using those keys, so we can read the rest of the server and client packet data
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// (all of the rest of it will be encrypted)
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CRYPT_SETUP server_cs, client_cs;
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CRYPT_CreateKeys(&server_cs, &server_key, CRYPT_GAMECUBE);
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CRYPT_CreateKeys(&client_cs, &client_key, CRYPT_GAMECUBE);
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// display remainder of server packets first
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printf("**** SERVER -> CLIENT PACKETS ****\n\n");
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while (pos < server_data_size) {
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CRYPT_CryptData(&server_cs, &server_data[pos], 4, 0);
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pkt_id = server_data[pos];
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pkt_flags = server_data[pos+1];
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pkt_size = *((uint16_t*)&server_data[pos+2]);
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CRYPT_CryptData(&server_cs, &server_data[pos+4], pkt_size-4, 0);
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printf("id=%x, flags=%x, size=%d\n", pkt_id, pkt_flags, pkt_size);
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CRYPT_PrintData(&server_data[pos], pkt_size);
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printf("\n");
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pos += pkt_size;
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}
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// now display the client packets
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printf("**** CLIENT -> SERVER PACKETS ****\n\n");
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pos = 0;
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while (pos < client_data_size) {
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CRYPT_CryptData(&client_cs, &client_data[pos], 4, 0);
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pkt_id = client_data[pos];
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pkt_flags = client_data[pos+1];
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pkt_size = *((uint16_t*)&client_data[pos+2]);
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CRYPT_CryptData(&client_cs, &client_data[pos+4], pkt_size-4, 0);
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printf("id=%x, flags=%x, size=%d\n", pkt_id, pkt_flags, pkt_size);
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CRYPT_PrintData(&client_data[pos], pkt_size);
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printf("\n");
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pos += pkt_size;
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}
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return 0;
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}
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