Add emv_extract.lua via upload

Script that extracts EMV track 2 information

Signed-off-by: Trigat <trigat@protonmail.com>

client/luascripts/emv_extract.lua

@@ -0,0 +1,80 @@
+copyright = "Trigat"
+author = "Trigat"
+desc = "This script scans an EMV (credit or debit) card and extracts Track 2 information."
+
+local home = os.getenv("HOME")
+local json_file = home .. "/emv_output.json"
+
+core.console(string.format("emv scan -at %s", json_file))
+
+os.execute("sleep 1")
+
+-- Read JSON content
+local f = io.open(json_file, "r")
+if not f then
+    print("[!!] Could not open JSON output")
+    return
+end
+
+local content = f:read("*a")
+f:close()
+
+local track2 = nil
+local found = false
+
+-- Iterate over all "value" fields in JSON
+for value_field in content:gmatch('"value"%s*:%s*"(.-)"') do
+    -- Look for 57 13 anywhere in the string
+    track2 = value_field:match('57%s*13%s*([0-9A-Fa-f%s]+)')
+    if track2 then
+        -- Remove spaces to get clean hex
+        track2 = track2:gsub("%s+", "")
+        print("[++] Track 2 data found: 57 13 " .. track2 .. "\n")
+        found = true
+        break -- remove break if you want all occurrences
+    end
+end
+
+if not found then
+    print("[!!] Track 2 data not found in JSON")
+    return
+end
+
+-- Remove 57 + Length prefix (first 4 hex digits = 57 13)
+track2 = track2:gsub("^57%x%x", "")
+
+-- Convert hex string into individual nibbles (1 hex digit each)
+local nibbles = {}
+for hex_digit in track2:gmatch("%x") do
+    table.insert(nibbles, hex_digit)
+end
+
+-- Find 'D' separator
+local sep_index
+for i, nib in ipairs(nibbles) do
+    if nib == "D" then
+        sep_index = i
+        break
+    end
+end
+
+if not sep_index then
+    print("[!!] Could not find 'D' separator in Track 2")
+    return
+end
+
+-- Extract Primary Account Number (all nibbles before D)
+local pan = table.concat(nibbles, "", 1, sep_index-1)
+
+-- Expiry is next 4 nibbles after D
+local yy = nibbles[sep_index + 1] .. nibbles[sep_index + 2]
+local mm = nibbles[sep_index + 3] .. nibbles[sep_index + 4]
+
+-- Service code: next 3 nibbles
+local service = table.concat(nibbles, "", sep_index + 5, sep_index + 7) or "N/A"
+
+print("[++] PAN: " .. pan)
+print("[++] Expiry (MM/YY): " .. mm .. "/" .. yy)
+print("[++] Service code: " .. service)
+
+os.execute('rm -f ' .. json_file)