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Merge pull request #1231 from AudricV/yt_fix-n-param-decode-function-…
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…extraction

[YouTube] Fix extraction of n param deobfuscation function name
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TobiGr authored Oct 5, 2024
2 parents 743a400 + 69ff271 commit 5431069
Showing 1 changed file with 41 additions and 18 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -22,57 +22,80 @@ final class YoutubeThrottlingParameterUtils {

private static final String SINGLE_CHAR_VARIABLE_REGEX = "[a-zA-Z0-9$_]";

private static final String FUNCTION_NAME_REGEX = SINGLE_CHAR_VARIABLE_REGEX + "+";
private static final String MULTIPLE_CHARS_REGEX = SINGLE_CHAR_VARIABLE_REGEX + "+";

private static final String ARRAY_ACCESS_REGEX = "\\[(\\d+)]";

// CHECKSTYLE:OFF
private static final Pattern[] DEOBFUSCATION_FUNCTION_NAME_REGEXES = {

/*
* The first regex matches the following text, where we want rDa and the array index
* The first regex matches the following text, where we want Wma and the array index
* accessed:
*
* a.D&&(b="nn"[+a.D],WL(a),c=a.j[b]||null)&&(c=SDa[0](c),a.set(b,c),SDa.length||Wma("")
*/
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "=\"nn\"\\[\\+" + MULTIPLE_CHARS_REGEX
+ "\\." + MULTIPLE_CHARS_REGEX + "]," + MULTIPLE_CHARS_REGEX + "\\("
+ MULTIPLE_CHARS_REGEX + "\\)," + MULTIPLE_CHARS_REGEX + "="
+ MULTIPLE_CHARS_REGEX + "\\." + MULTIPLE_CHARS_REGEX + "\\["
+ MULTIPLE_CHARS_REGEX + "]\\|\\|null\\).+\\|\\|(" + MULTIPLE_CHARS_REGEX
+ ")\\(\"\"\\)"),

/*
* The second regex matches the following text, where we want SDa and the array index
* accessed:
*
* a.D&&(b="nn"[+a.D],WL(a),c=a.j[b]||null)&&(c=SDa[0](c),a.set(b,c),SDa.length||Wma("")
*/
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "=\"nn\"\\[\\+" + MULTIPLE_CHARS_REGEX
+ "\\." + MULTIPLE_CHARS_REGEX + "]," + MULTIPLE_CHARS_REGEX + "\\("
+ MULTIPLE_CHARS_REGEX + "\\)," + MULTIPLE_CHARS_REGEX + "="
+ MULTIPLE_CHARS_REGEX + "\\." + MULTIPLE_CHARS_REGEX + "\\["
+ MULTIPLE_CHARS_REGEX + "]\\|\\|null\\)&&\\(" + MULTIPLE_CHARS_REGEX + "=("
+ MULTIPLE_CHARS_REGEX + ")" + ARRAY_ACCESS_REGEX),

/*
* The third regex matches the following text, where we want rma:
*
* a.D&&(b="nn"[+a.D],c=a.get(b))&&(c=rDa[0](c),a.set(b,c),rDa.length||rma("")
*/
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "+=\"nn\"\\[\\+"
+ SINGLE_CHAR_VARIABLE_REGEX + "+\\." + SINGLE_CHAR_VARIABLE_REGEX + "+],"
+ SINGLE_CHAR_VARIABLE_REGEX + "+=" + SINGLE_CHAR_VARIABLE_REGEX
+ "+\\.get\\(" + SINGLE_CHAR_VARIABLE_REGEX + "+\\)\\)&&\\("
+ SINGLE_CHAR_VARIABLE_REGEX + "+=(" + SINGLE_CHAR_VARIABLE_REGEX
+ "+)\\[(\\d+)]"),
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "=\"nn\"\\[\\+" + MULTIPLE_CHARS_REGEX
+ "\\." + MULTIPLE_CHARS_REGEX + "]," + MULTIPLE_CHARS_REGEX + "="
+ MULTIPLE_CHARS_REGEX + "\\.get\\(" + MULTIPLE_CHARS_REGEX + "\\)\\).+\\|\\|("
+ MULTIPLE_CHARS_REGEX + ")\\(\"\"\\)"),

/*
* The second regex matches the following text, where we want rma:
* The fourth regex matches the following text, where we want rDa and the array index
* accessed:
*
* a.D&&(b="nn"[+a.D],c=a.get(b))&&(c=rDa[0](c),a.set(b,c),rDa.length||rma("")
*/
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "+=\"nn\"\\[\\+"
+ SINGLE_CHAR_VARIABLE_REGEX + "+\\." + SINGLE_CHAR_VARIABLE_REGEX + "+],"
+ SINGLE_CHAR_VARIABLE_REGEX + "+=" + SINGLE_CHAR_VARIABLE_REGEX + "+\\.get\\("
+ SINGLE_CHAR_VARIABLE_REGEX + "+\\)\\).+\\|\\|(" + SINGLE_CHAR_VARIABLE_REGEX
+ "+)\\(\"\"\\)"),
Pattern.compile(SINGLE_CHAR_VARIABLE_REGEX + "=\"nn\"\\[\\+" + MULTIPLE_CHARS_REGEX
+ "\\." + MULTIPLE_CHARS_REGEX + "]," + MULTIPLE_CHARS_REGEX + "="
+ MULTIPLE_CHARS_REGEX + "\\.get\\(" + MULTIPLE_CHARS_REGEX + "\\)\\)&&\\("
+ MULTIPLE_CHARS_REGEX + "=(" + MULTIPLE_CHARS_REGEX + ")\\[(\\d+)]"),

/*
* The third regex matches the following text, where we want BDa and the array index
* The fifth regex matches the following text, where we want BDa and the array index
* accessed:
*
* (b=String.fromCharCode(110),c=a.get(b))&&(c=BDa[0](c)
*/
Pattern.compile("\\(" + SINGLE_CHAR_VARIABLE_REGEX + "=String\\.fromCharCode\\(110\\),"
+ SINGLE_CHAR_VARIABLE_REGEX + "=" + SINGLE_CHAR_VARIABLE_REGEX + "\\.get\\("
+ SINGLE_CHAR_VARIABLE_REGEX + "\\)\\)" + "&&\\(" + SINGLE_CHAR_VARIABLE_REGEX
+ "=(" + FUNCTION_NAME_REGEX + ")" + "(?:" + ARRAY_ACCESS_REGEX + ")?\\("
+ "=(" + MULTIPLE_CHARS_REGEX + ")" + "(?:" + ARRAY_ACCESS_REGEX + ")?\\("
+ SINGLE_CHAR_VARIABLE_REGEX + "\\)"),

/*
* The fourth regex matches the following text, where we want Yva and the array index
* The sixth regex matches the following text, where we want Yva and the array index
* accessed:
*
* .get("n"))&&(b=Yva[0](b)
*/
Pattern.compile("\\.get\\(\"n\"\\)\\)&&\\(" + SINGLE_CHAR_VARIABLE_REGEX
+ "=(" + FUNCTION_NAME_REGEX + ")(?:" + ARRAY_ACCESS_REGEX + ")?\\("
+ "=(" + MULTIPLE_CHARS_REGEX + ")(?:" + ARRAY_ACCESS_REGEX + ")?\\("
+ SINGLE_CHAR_VARIABLE_REGEX + "\\)")
};
// CHECKSTYLE:ON
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