feat: decodeEmail XOR function

src/utils/cf.go

@@ -0,0 +1,56 @@
+package utils
+
+import (
+	"encoding/hex"
+	"net/url"
+	"strings"
+)
+
+// decodeEmail decodes an obfuscated email string.
+func DecodeEmail(encoded string) (string, error) {
+	// remove the prefix if present
+	prefix := "/cdn-cgi/l/email-protection#"
+	encoded = strings.TrimPrefix(encoded, prefix)
+
+	// get the key for XOR operation
+	key, err := hex.DecodeString(encoded[:2])
+	if err != nil {
+		return "", err
+	}
+
+	// decode the rest of the string using the key
+	var decodedChars []byte
+	// start a loop from the third character of the encoded string (index 2), as the first two characters are used as the key for XOR operation.
+	// the loop increments by 2 in each iteration because the encoded string is in hexadecimal format, and each hexadecimal character represents 4 bits.
+	// so, two hexadecimal characters represent one byte (8 bits), which is the size of a character in ASCII.
+	for i := 2; i < len(encoded); i += 2 {
+		// get the current pair of hexadecimal characters from the encoded string.
+		encodedPair := encoded[i : i+2]
+
+		// decode the hexadecimal pair to get the original byte. this is done by converting the hexadecimal pair to a byte using the DecodeString function from the encoding/hex package.
+		// if the hexadecimal pair is not a valid hexadecimal number, DecodeString will return an error.
+		pairBytes, err := hex.DecodeString(encodedPair)
+		if err != nil {
+			// if there is an error in decoding, return the error and an empty string.
+			return "", err
+		}
+
+		// perform an XOR operation on the decoded byte with the key. this is the reverse operation of the original encoding process.
+		// the XOR operation is a bitwise operation that returns 0 if the two bits are the same, and 1 otherwise.
+		// by performing the XOR operation with the same key used in the encoding process, we can retrieve the original byte.
+		decodedChar := pairBytes[0] ^ key[0]
+
+		// append the decoded character to the decodedChars slice. this slice will hold all the decoded characters of the encoded string.
+		decodedChars = append(decodedChars, decodedChar)
+	}
+	// convert the decoded bytes to a string
+	decoded := string(decodedChars)
+
+	// unescape any URL-encoded characters
+	unescaped, err := url.QueryUnescape(decoded)
+	if err != nil {
+		return "", err
+	}
+
+	return unescaped, nil
+}