[ruby-dev:44875] [ruby-trunk - Bug #5635][Open] String#unpack("M") の不正データ時の振る舞い

Issue #5635 has been reported by Masahiro Tomita.

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Bug #5635: String#unpack("M") の不正データ時の振る舞い
http://redmine.ruby-lang.org/issues/5635

Author: Masahiro Tomita
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 1.9.3p0 (2011-11-08 revision 33661) [i686-linux]


String#unpack("M") で "=hoge" みたいな不正なデータがあった場合、現在は
そこで処理を中断してしまっていますが、それ以降のデータをすべて捨ててし
まうのはかわいそうなので、ポインタを一つ進めて処理を継続した方がいいん
じゃないかと思うのですがどうでしょうか。

RFC2045 には次のような記述があります。

    (2)   An "=" followed by a character that is neither a
          hexadecimal digit (including "abcdef") nor the CR
          character of a CRLF pair is illegal.  This case can be
          the result of US-ASCII text having been included in a
          quoted-printable part of a message without itself
          having been subjected to quoted-printable encoding.  A
          reasonable approach by a robust implementation might be
          to include the "=" character and the following
          character in the decoded data without any
          transformation and, if possible, indicate to the user
          that proper decoding was not possible at this point in
          the data.

Index: pack.c
===================================================================
--- pack.c	(リビジョン 33758)
+++ pack.c	(作業コピー)
@@ -2008,20 +2008,23 @@
 
 		while (s < send) {
 		    if (*s == '=') {
-			if (++s == send) break;
-                       if (s+1 < send && *s == '\r' && *(s+1) == '\n')
-                         s++;
-			if (*s != '\n') {
-			    if ((c1 = hex2num(*s)) == -1) break;
-			    if (++s == send) break;
-			    if ((c2 = hex2num(*s)) == -1) break;
-			    *ptr++ = c1 << 4 | c2;
+			if (s+1 < send && *(s+1) == '\n') {
+			    s += 2;
+			    continue;
+			}
+			if (s+2 < send) {
+			    if (*(s+1) == '\r' && *(s+2) == '\n') {
+				s += 3;
+				continue;
+			    }
+			    if ((c1 = hex2num(*(s+1))) > -1 && (c2 = hex2num(*(s+2))) > -1) {
+				*ptr++ = c1 << 4 | c2;
+				s += 3;
+				continue;
+			    }
 			}
 		    }
-		    else {
-			*ptr++ = *s;
-		    }
-		    s++;
+		    *ptr++ = *s++;
 		}
 		rb_str_set_len(buf, ptr - RSTRING_PTR(buf));
 		ENCODING_CODERANGE_SET(buf, rb_ascii8bit_encindex(), ENC_CODERANGE_VALID);
Index: test/ruby/test_pack.rb
===================================================================
--- test/ruby/test_pack.rb	(リビジョン 33758)
+++ test/ruby/test_pack.rb	(作業コピー)
@@ -612,6 +612,17 @@
     assert_equal([0x100000000], "\220\200\200\200\000".unpack("w"), [0x100000000])
   end
 
+  def test_pack_unpack_M
+    assert_equal(["pre123after"], "pre=31=32=33after".unpack("M"))
+    assert_equal(["preafter"], "pre=\nafter".unpack("M"))
+    assert_equal(["preafter"], "pre=\r\nafter".unpack("M"))
+    assert_equal(["pre="], "pre=".unpack("M"))
+    assert_equal(["pre=\r"], "pre=\r".unpack("M"))
+    assert_equal(["pre=hoge"], "pre=hoge".unpack("M"))
+    assert_equal(["pre=1after"], "pre==31after".unpack("M"))
+    assert_equal(["pre==1after"], "pre===31after".unpack("M"))
+  end
+
   def test_modify_under_safe4
     s = "foo"
     assert_raise(SecurityError) do



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