rpkg_rs/encryption/
xtea.rs

1use crate::encryption::xtea::XteaError::InvalidInput;
2use byteorder::{LittleEndian, WriteBytesExt};
3use extended_tea::XTEA;
4use std::io::Cursor;
5use thiserror::Error;
6
7/// Errors that can occur during XTEA encryption or decryption.
8#[derive(Debug, Error)]
9pub enum XteaError {
10    #[error("Text encoding error: {0}")]
11    TextEncodingError(std::string::FromUtf8Error),
12
13    #[error("An error occurred while trying to decrypt the file: {:?}", _0)]
14    CipherError(std::io::Error),
15
16    #[error("Unexpected input: {:?}", _0)]
17    InvalidInput(String),
18
19    #[error("Xtea encoding error: {0}")]
20    XteaEncodingError(std::io::Error),
21}
22
23/// Implementation of XTEA encryption and decryption methods.
24pub struct Xtea;
25
26impl Xtea {
27    /// Default XTEA key, used in thumbs.dat and packagedefinition.txt
28    pub const DEFAULT_KEY: [u32; 4] = [0x30f95282, 0x1f48c419, 0x295f8548, 0x2a78366d];
29
30    /// LOCR/TEXTLIST XTEA key, used for localization
31    pub const LOCR_KEY: [u32; 4] = [0x53527737, 0x7506499E, 0xBD39AEE3, 0xA59E7268];
32
33    /// Default header for encrypted files.
34    const DEFAULT_ENCRYPTED_HEADER: [u8; 0x10] = [
35        0x22, 0x3d, 0x6f, 0x9a, 0xb3, 0xf8, 0xfe, 0xb6, 0x61, 0xd9, 0xcc, 0x1c, 0x62, 0xde, 0x83,
36        0x41,
37    ];
38
39    /// Checks if a given buffer represents an encrypted text file.
40    /// This function will check for the presence of a default header in the text file.
41    pub fn is_encrypted_text_file(input_buffer: &[u8]) -> bool {
42        input_buffer.starts_with(&Self::DEFAULT_ENCRYPTED_HEADER)
43    }
44
45    /// Decrypts a text file given its buffer, uses the default xtea key.
46    pub fn decrypt_text_file(input_buffer: &[u8]) -> Result<String, XteaError> {
47        let payload_start = Self::DEFAULT_ENCRYPTED_HEADER.len() + 4;
48
49        if input_buffer.len() < payload_start {
50            return Err(InvalidInput("Input too short".to_string()));
51        }
52
53        if !input_buffer.starts_with(&Self::DEFAULT_ENCRYPTED_HEADER) {
54            return Err(InvalidInput("Header mismatch".to_string()));
55        }
56        let checksum = &input_buffer[payload_start - 4..payload_start];
57        let input = &input_buffer[payload_start..];
58
59        if input.len() % 8 != 0 {
60            return Err(InvalidInput(
61                "Input must be of a length divisible by 8".to_string(),
62            ));
63        }
64
65        let xtea = XTEA::new(&Self::DEFAULT_KEY);
66        let mut out_buffer = vec![0u8; input.len()];
67
68        let mut input_reader = Cursor::new(input);
69        let mut ouput_writer = Cursor::new(&mut out_buffer);
70
71        xtea.decipher_stream::<LittleEndian, _, _>(&mut input_reader, &mut ouput_writer)
72            .map_err(XteaError::CipherError)?;
73
74        let output = String::from_utf8(ouput_writer.get_mut().to_owned())
75            .map_err(XteaError::TextEncodingError)?;
76
77        let result_checksum =
78            crc32fast::hash(output.trim_end_matches('\0').as_bytes()).to_le_bytes();
79        match result_checksum == checksum {
80            true => Ok(output),
81            false => Err(InvalidInput("CRC checksum mismatched!".to_string())),
82        }
83    }
84
85    /// Decrypts a string given its buffer and key.
86    pub fn decrypt_string(input_buffer: &[u8], key: &[u32; 4]) -> Result<String, XteaError> {
87        let input = &input_buffer;
88
89        if input.len() % 8 != 0 {
90            return Err(InvalidInput(
91                "Input must be of a length divisible by 8".to_string(),
92            ));
93        }
94
95        let xtea = XTEA::new(key);
96        let mut out_buffer = vec![0u8; input.len()];
97
98        let mut input_reader = Cursor::new(input);
99        let mut ouput_writer = Cursor::new(&mut out_buffer);
100
101        xtea.decipher_stream::<LittleEndian, _, _>(&mut input_reader, &mut ouput_writer)
102            .map_err(XteaError::CipherError)?;
103
104        String::from_utf8(ouput_writer.get_mut().to_owned()).map_err(XteaError::TextEncodingError)
105    }
106
107    pub fn encrypt_text_file(input_string: String) -> Result<Vec<u8>, XteaError> {
108        //get the input buffer and trim any trailing zeros
109        let mut input_buffer = input_string.trim_end_matches('\0').as_bytes().to_vec();
110        let checksum = crc32fast::hash(&input_buffer);
111
112        let padding = 8 - (input_buffer.len() % 8);
113        if padding < 8 {
114            input_buffer.extend(vec![0u8; padding]);
115        }
116        let mut out_buffer = vec![0u8; input_buffer.len()];
117        let xtea = XTEA::new(&Self::DEFAULT_KEY);
118
119        let mut input_reader = Cursor::new(&input_buffer);
120        let mut output_writer = Cursor::new(&mut out_buffer);
121
122        xtea.encipher_stream::<LittleEndian, _, _>(&mut input_reader, &mut output_writer)
123            .map_err(XteaError::CipherError)?;
124
125        let mut final_buffer = Vec::new();
126        final_buffer.extend_from_slice(&Self::DEFAULT_ENCRYPTED_HEADER);
127
128        final_buffer
129            .write_u32::<LittleEndian>(checksum)
130            .map_err(XteaError::XteaEncodingError)?;
131
132        final_buffer.extend_from_slice(&out_buffer);
133
134        Ok(final_buffer)
135    }
136
137    pub fn encrypt_string(input_string: String, key: &[u32; 4]) -> Result<Vec<u8>, XteaError> {
138        let mut input_buffer = input_string.into_bytes();
139
140        // Pad the input buffer to make its length a multiple of 8 bytes
141        let padding = 8 - (input_buffer.len() % 8);
142        if padding < 8 {
143            input_buffer.extend(vec![0u8; padding]);
144        }
145
146        let mut out_buffer = vec![0u8; input_buffer.len()];
147        let xtea = XTEA::new(key);
148
149        let mut input_reader = Cursor::new(&input_buffer);
150        let mut output_writer = Cursor::new(&mut out_buffer);
151
152        xtea.encipher_stream::<LittleEndian, _, _>(&mut input_reader, &mut output_writer)
153            .map_err(XteaError::CipherError)?;
154
155        Ok(out_buffer)
156    }
157}
rpkg_rs/encryption/xtea.rs

rpkg_rs/encryption/
xtea.rs
