Refactor signature extraction

5 years ago · 648cc0f006
parent 830692dd60
commit 648cc0f006
2 changed files with 20 additions and 36 deletions
--- a/src/invidious.cr
+++ b/src/invidious.cr
@ -207,7 +207,7 @@ spawn do
  end
 end

-decrypt_function = [] of {name: String, value: Int32}
+decrypt_function = [] of {SigProc, Int32}
 spawn do
  update_decrypt_function do |function|
    decrypt_function = function
--- a/src/invidious/helpers/signatures.cr
+++ b/src/invidious/helpers/signatures.cr
@ -1,69 +1,53 @@
+alias SigProc = Proc(Array(String), Int32, Array(String))
+
 def fetch_decrypt_function(id = "CvFH_6DNRCY")
  document = YT_POOL.client &.get("/watch?v=#{id}&gl=US&hl=en&disable_polymer=1").body
-  url = document.match(/src="(?<url>\/yts\/jsbin\/player_ias-.{9}\/en_US\/base.js)"/).not_nil!["url"]
+  url = document.match(/src="(?<url>\/yts\/jsbin\/player_ias-[^\/]+\/en_US\/base.js)"/).not_nil!["url"]
  player = YT_POOL.client &.get(url).body

-  function_name = player.match(/^(?<name>[^=]+)=function\(a\){a=a\.split\(""\)/m).not_nil!["name"]
-  function_body = player.match(/^#{Regex.escape(function_name)}=function\(a\){(?<body>[^}]+)}/m).not_nil!["body"]
+  function_name = player.match(/^(?<name>[^=]+)=function\(\w\){\w=\w\.split\(""\);[^\. ]+\.[^( ]+/m).not_nil!["name"]
+  function_body = player.match(/^#{Regex.escape(function_name)}=function\(\w\){(?<body>[^}]+)}/m).not_nil!["body"]
  function_body = function_body.split(";")[1..-2]

  var_name = function_body[0][0, 2]
  var_body = player.delete("\n").match(/var #{Regex.escape(var_name)}={(?<body>(.*?))};/).not_nil!["body"]

-  operations = {} of String => String
+  operations = {} of String => SigProc
  var_body.split("},").each do |operation|
    op_name = operation.match(/^[^:]+/).not_nil![0]
    op_body = operation.match(/\{[^}]+/).not_nil![0]

    case op_body
    when "{a.reverse()"
-      operations[op_name] = "a"
+      operations[op_name] = ->(a : Array(String), b : Int32) { a.reverse }
    when "{a.splice(0,b)"
-      operations[op_name] = "b"
+      operations[op_name] = ->(a : Array(String), b : Int32) { a.delete_at(0..(b - 1)); a }
    else
-      operations[op_name] = "c"
+      operations[op_name] = ->(a : Array(String), b : Int32) { c = a[0]; a[0] = a[b % a.size]; a[b % a.size] = c; a }
    end
  end

-  decrypt_function = [] of {name: String, value: Int32}
+  decrypt_function = [] of {SigProc, Int32}
  function_body.each do |function|
    function = function.lchop(var_name).delete("[].")

    op_name = function.match(/[^\(]+/).not_nil![0]
-    value = function.match(/\(a,(?<value>[\d]+)\)/).not_nil!["value"].to_i
+    value = function.match(/\(\w,(?<value>[\d]+)\)/).not_nil!["value"].to_i

-    decrypt_function << {name: operations[op_name], value: value}
+    decrypt_function << {operations[op_name], value}
  end

  return decrypt_function
 end

-def decrypt_signature(fmt, code)
-  if !fmt["s"]?
-    return ""
-  end
-
-  a = fmt["s"]
-  a = a.split("")
+def decrypt_signature(fmt, op)
+  return "" if !fmt["s"]? || !fmt["sp"]?

-  code.each do |item|
-    case item[:name]
-    when "a"
-      a.reverse!
-    when "b"
-      a.delete_at(0..(item[:value] - 1))
-    when "c"
-      a = splice(a, item[:value])
+  sp = fmt["sp"]
+  sig = fmt["s"].split("")
+  op.each do |proc, value|
+    sig = proc.call(sig, value)
  end
-  end
-
-  signature = a.join("")
-  return "&#{fmt["sp"]?}=#{signature}"
-end

-def splice(a, b)
-  c = a[0]
-  a[0] = a[b % a.size]
-  a[b % a.size] = c
-  return a
+  return "&#{sp}=#{sig.join("")}"
 end