pix_brcode_parser/
validation.rs

1//! CRC16 validation and other validation utilities for PIX BR Code
2
3use crc::{Crc, Algorithm};
4use crate::error::{BRCodeError, Result};
5
6/// CRC16 calculator for EMV QRCPS compliance (CRC-16/CCITT-FALSE)
7/// Using the standard CRC-16 polynomial 0x1021 with initial value 0xFFFF
8pub const CRC16: Crc<u16> = Crc::<u16>::new(&Algorithm {
9    width: 16,
10    poly: 0x1021,
11    init: 0xffff,
12    refin: false,
13    refout: false,
14    xorout: 0x0000,
15    check: 0x29b1,
16    residue: 0x0000,
17});
18
19/// Calculate CRC16 using a simple implementation that matches PIX standards
20fn calculate_crc16_simple(data: &[u8]) -> u16 {
21    let mut crc: u16 = 0xFFFF;
22    
23    for &byte in data {
24        crc ^= (byte as u16) << 8;
25        for _ in 0..8 {
26            if crc & 0x8000 != 0 {
27                crc = (crc << 1) ^ 0x1021;
28            } else {
29                crc <<= 1;
30            }
31        }
32    }
33    
34    crc
35}
36
37/// Validate CRC16 checksum of a BR Code string
38/// 
39/// The CRC16 is calculated over the entire payload excluding the CRC field (tag 63)
40pub fn validate_crc16(brcode: &str) -> Result<bool> {
41    if brcode.len() < 4 {
42        return Err(BRCodeError::invalid_format("BR Code too short for CRC validation"));
43    }
44    
45    // Find the CRC field (tag 63)
46    let crc_pos = brcode.rfind("63");
47    let crc_pos = match crc_pos {
48        Some(pos) => pos,
49        None => return Err(BRCodeError::missing_field("CRC16 field (tag 63)")),
50    };
51    
52    // Extract the payload without CRC and the CRC value
53    let payload = &brcode[..crc_pos + 2]; // Include "63" + length
54    let crc_length_str = &brcode[crc_pos + 2..crc_pos + 4];
55    let crc_length: usize = crc_length_str.parse()
56        .map_err(|_| BRCodeError::invalid_format("Invalid CRC length field"))?;
57    
58    if crc_length != 4 {
59        return Err(BRCodeError::InvalidFieldLength {
60            tag: "63".to_string(),
61            expected: 4,
62            actual: crc_length,
63        });
64    }
65    
66    let expected_crc = &brcode[crc_pos + 4..crc_pos + 8];
67    let payload_with_length = format!("{}04", payload);
68    
69    // Calculate CRC16 over the payload
70    let calculated_crc = calculate_crc16_simple(payload_with_length.as_bytes());
71    let calculated_crc_hex = format!("{:04X}", calculated_crc);
72    
73    Ok(calculated_crc_hex == expected_crc.to_uppercase())
74}
75
76/// Calculate CRC16 checksum for a BR Code payload
77pub fn calculate_crc16(payload: &str) -> String {
78    let payload_with_crc_field = format!("{}6304", payload);
79    let checksum = calculate_crc16_simple(payload_with_crc_field.as_bytes());
80    format!("{:04X}", checksum)
81}
82
83/// Validate PIX key format
84pub fn validate_pix_key(key: &str) -> Result<()> {
85    if key.is_empty() {
86        return Err(BRCodeError::InvalidPixKey("PIX key cannot be empty".to_string()));
87    }
88    
89    // Basic validation - more specific validation could be added for each key type
90    if key.len() > 77 { // EMV maximum length
91        return Err(BRCodeError::InvalidPixKey("PIX key too long".to_string()));
92    }
93    
94    // Check for invalid characters (basic ASCII validation)
95    if !key.chars().all(|c| c.is_ascii() && !c.is_ascii_control()) {
96        return Err(BRCodeError::InvalidPixKey("PIX key contains invalid characters".to_string()));
97    }
98    
99    Ok(())
100}
101
102/// Validate merchant name format
103pub fn validate_merchant_name(name: &str) -> Result<()> {
104    if name.is_empty() {
105        return Err(BRCodeError::missing_field("Merchant name"));
106    }
107    
108    if name.len() > 25 {
109        return Err(BRCodeError::field_too_long("59", 25, name.len()));
110    }
111    
112    Ok(())
113}
114
115/// Validate merchant city format
116pub fn validate_merchant_city(city: &str) -> Result<()> {
117    if city.is_empty() {
118        return Err(BRCodeError::missing_field("Merchant city"));
119    }
120    
121    if city.len() > 15 {
122        return Err(BRCodeError::field_too_long("60", 15, city.len()));
123    }
124    
125    Ok(())
126}
127
128/// Validate transaction amount format
129pub fn validate_transaction_amount(amount: &str) -> Result<()> {
130    if amount.is_empty() {
131        return Ok(()); // Amount is optional
132    }
133    
134    // Check if it's a valid decimal number
135    amount.parse::<f64>()
136        .map_err(|_| BRCodeError::ParseNumericError(format!("Invalid amount: {}", amount)))?;
137    
138    Ok(())
139}
140
141/// Validate GUI field (should be "br.gov.bcb.pix")
142pub fn validate_gui(gui: &str) -> Result<()> {
143    if gui != "br.gov.bcb.pix" {
144        return Err(BRCodeError::InvalidGui(gui.to_string()));
145    }
146    Ok(())
147}
148
149/// Validate currency code (should be "986" for BRL)
150pub fn validate_currency(currency: &str) -> Result<()> {
151    if currency != "986" {
152        return Err(BRCodeError::InvalidCurrency(currency.to_string()));
153    }
154    Ok(())
155}
156
157/// Validate country code (should be "BR")
158pub fn validate_country_code(country: &str) -> Result<()> {
159    if country != "BR" {
160        return Err(BRCodeError::InvalidCountryCode(country.to_string()));
161    }
162    Ok(())
163}
164
165/// Validate payload format indicator (should be "01")
166pub fn validate_payload_format(format: &str) -> Result<()> {
167    if format != "01" {
168        return Err(BRCodeError::InvalidPayloadFormat(format.to_string()));
169    }
170    Ok(())
171}
172
173#[cfg(test)]
174mod tests {
175    use super::*;
176
177    #[test]
178    fn test_crc16_calculation() {
179        let payload = "00020126580014br.gov.bcb.pix0136123e4567-e12b-12d1-a456-426614174000520400005303986540510.005802BR5913FULANO DE TAL6008BRASILIA62070503***";
180        let expected_crc = "36D9";  // Corrected expected CRC value
181        let calculated_crc = calculate_crc16(payload);
182        assert_eq!(calculated_crc, expected_crc);
183    }
184
185    #[test]
186    fn test_crc16_validation_valid() {
187        let brcode = "00020126580014br.gov.bcb.pix0136123e4567-e12b-12d1-a456-426614174000520400005303986540510.005802BR5913FULANO DE TAL6008BRASILIA62070503***630436D9";
188        assert!(validate_crc16(brcode).unwrap());
189    }
190
191    #[test]
192    fn test_crc16_validation_invalid() {
193        let brcode = "00020126580014br.gov.bcb.pix0136123e4567-e12b-12d1-a456-426614174000520400005303986540510.005802BR5913FULANO DE TAL6008BRASILIA62070503***6304WXYZ";
194        assert!(!validate_crc16(brcode).unwrap());
195    }
196
197    #[test]
198    fn test_validate_pix_key() {
199        assert!(validate_pix_key("123e4567-e89b-12d3-a456-426614174000").is_ok());
200        assert!(validate_pix_key("user@example.com").is_ok());
201        assert!(validate_pix_key("").is_err());
202    }
203
204    #[test]
205    fn test_validate_merchant_name() {
206        assert!(validate_merchant_name("FULANO DE TAL").is_ok());
207        assert!(validate_merchant_name("").is_err());
208        assert!(validate_merchant_name("A".repeat(30).as_str()).is_err());
209    }
210
211    #[test]
212    fn test_validate_gui() {
213        assert!(validate_gui("br.gov.bcb.pix").is_ok());
214        assert!(validate_gui("invalid.gui").is_err());
215    }
216}
pix_brcode_parser/validation.rs

pix_brcode_parser/
validation.rs
