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Fix handling of packed MAC #78

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merged 1 commit into from
Mar 3, 2024
Merged

Fix handling of packed MAC #78

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11 changes: 9 additions & 2 deletions src/main/java/nz/co/breakpoint/jmeter/iso8583/ISO8583Crypto.java
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Original file line number Diff line number Diff line change
Expand Up @@ -103,13 +103,20 @@ protected void calculateMAC(ISO8583Sampler sampler) {
int macField = (fixedMacField != null && !fixedMacField.isEmpty()) ? Integer.parseInt(fixedMacField) :
((msg.getMaxField() - 1)/MAC_FIELD_NO + 1)*MAC_FIELD_NO; // round up to the next multiple of 64

int macLength = ((ISOBasePackager)msg.getPackager()).getFieldPackager(macField).getLength();
ISOFieldPackager fp = ((ISOBasePackager)msg.getPackager()).getFieldPackager(macField);
if (!(fp instanceof ISOBinaryFieldPackager)) {
log.error("MAC cannot be packed into non-binary field "+fp.getClass());
return;
}
int macLength = fp.getLength();
int packedLength = fp.getMaxPackedLength();

final String dummyMac = String.format("%0" + 2*macLength + "d", 0);
msg.set(macField, dummyMac);
try {
byte[] packedMsg = msg.pack();
// cut off MAC bytes and don't include them in calculation:
String mac = securityModule.generateMAC(Arrays.copyOf(packedMsg, packedMsg.length-macLength),
String mac = securityModule.generateMAC(Arrays.copyOf(packedMsg, packedMsg.length-packedLength),
macKey, macAlgorithm);
sampler.addField(String.valueOf(macField), ISOUtil.padright(mac, 2*macLength, 'f'));
} catch (ISOException e) {
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