feat: TD1 MRZ Overflow Format #1337
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@@ -186,9 +186,12 @@ function validateTD3CheckDigits(lines: string[]): Omit<MRZValidation, 'format' | | |
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| export function checkScannedInfo(passportNumber: string, dateOfBirth: string, dateOfExpiry: string): boolean { | ||
| // TD1 overflow format allows document numbers > 9 characters per ICAO 9303: | ||
| // When document numbers exceed 9 characters, the overflow digits are stored in the optional data | ||
| // field and the full document number is reconstructed during MRZ parsing. | ||
| // if (passportNumber.length > 9) { | ||
| // return false; | ||
| // } | ||
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Contributor
There was a problem hiding this comment. Critical: Incomplete TD1 overflow implementation. Removing the length check without updating the TD1 extraction and validation logic creates an incomplete implementation. The iOS code (per PR objectives) added This could lead to:
Apply these fixes: 1. Update function extractTD1Info(lines: string[]): Omit<MRZInfo, 'validation'> {
const line1 = lines[0];
const line2 = lines[1];
const concatenatedLines = line1 + line2;
+
+ // Handle TD1 overflow format per ICAO 9303
+ // When document number exceeds 9 chars, overflow is in optional data
+ let documentNumber = concatenatedLines.slice(5, 14).replace(/</g, '').trim();
+ const documentNumberCheckDigitPos = concatenatedLines.slice(14, 15);
+
+ // Detect overflow: if position 15 is '<', overflow exists in optional data
+ if (documentNumberCheckDigitPos === '<') {
+ // Extract overflow from optional data (positions 15-29, which is indices 15-29)
+ const optionalData = concatenatedLines.slice(15, 30);
+ // Find the check digit (last non-< character in overflow)
+ let overflowChars = '';
+ for (let i = 0; i < optionalData.length; i++) {
+ if (optionalData[i] !== '<') {
+ overflowChars += optionalData[i];
+ } else {
+ break;
+ }
+ }
+ // Append overflow to document number (excluding last char which is check digit)
+ if (overflowChars.length > 0) {
+ documentNumber += overflowChars.slice(0, -1);
+ }
+ }
return {
documentType: concatenatedLines.slice(0, 2),
issuingCountry: concatenatedLines.slice(2, 5),
- documentNumber: concatenatedLines.slice(5, 14).replace(/</g, '').trim(),
+ documentNumber,
dateOfBirth: concatenatedLines.slice(30, 36),
dateOfExpiry: concatenatedLines.slice(38, 44),
};
}2. Update function validateTD1CheckDigits(lines: string[]): Omit<MRZValidation, 'format' | 'overall'> {
const line1 = lines[0];
const line2 = lines[1];
const concatenatedLines = line1 + line2;
- const documentNumber = concatenatedLines.slice(5, 14);
- const documentNumberCheckDigit = concatenatedLines.slice(14, 15);
+ // Handle TD1 overflow format
+ let documentNumber = concatenatedLines.slice(5, 14);
+ let documentNumberCheckDigit = concatenatedLines.slice(14, 15);
+
+ // Detect overflow: if position 15 is '<', check digit is in optional data
+ if (documentNumberCheckDigit === '<') {
+ const optionalData = concatenatedLines.slice(15, 30);
+ // Find overflow characters and check digit
+ let overflowChars = '';
+ for (let i = 0; i < optionalData.length; i++) {
+ if (optionalData[i] !== '<') {
+ overflowChars += optionalData[i];
+ } else {
+ break;
+ }
+ }
+ if (overflowChars.length > 0) {
+ // Last char is check digit, rest is overflow
+ documentNumberCheckDigit = overflowChars.slice(-1);
+ documentNumber += overflowChars.slice(0, -1);
+ }
+ }
+
const dateOfBirth = concatenatedLines.slice(30, 36);
const dobCheckDigit = concatenatedLines.slice(36, 37);
const dateOfExpiry = concatenatedLines.slice(38, 44);
const expiryCheckDigit = concatenatedLines.slice(44, 45);
return {
passportNumberChecksum: verifyCheckDigit(documentNumber, documentNumberCheckDigit),
dateOfBirthChecksum: verifyCheckDigit(dateOfBirth, dobCheckDigit),
dateOfExpiryChecksum: verifyCheckDigit(dateOfExpiry, expiryCheckDigit),
compositeChecksum: true, // TD1 doesn't have a composite check digit like TD3
};
}
Collaborator
There was a problem hiding this comment. This specific code path is only reached on Android. This PR addresses only the iOS platform.
Contributor
There was a problem hiding this comment. @seshanthS Thank you for the clarification! I understand now—this TypeScript code path is Android-only, and since this PR addresses only iOS, the Android TD1 overflow implementation is appropriately deferred. The change to comment out the length check makes sense as an interim step: it prevents Android from prematurely rejecting document numbers > 9 characters, while the full TD1 overflow extraction and validation logic (similar to what was implemented in the iOS Swift code) would be added when Android support is implemented later—as noted in the PR TODOs. For the iOS flow, the Swift implementation in ✏️ Learnings added
🧠 Learnings used |
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| if (dateOfBirth.length !== 6) { | ||
| return false; | ||
| } | ||
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Strip PII from standard-format logging.
This
printdumps the raw document number and check digit into logs, which violates our “never log PII” rule for MRZ data and creates GDPR/CCPA exposure in release builds. Please remove or properly gate/redact the output.[suggested fix]
As per coding guidelines.
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