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base64-decode-region inserts carriage-returns

From: Eric Hanchrow
Subject: base64-decode-region inserts carriage-returns
Date: 08 Jun 2002 13:42:42 -0700

In GNU Emacs 21.2.1 (i386-debian-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2002-05-18 on offby1, modified by Debian
configured using `configure  i386-debian-linux-gnu --prefix=/usr 
--sharedstatedir=/var/lib --libexecdir=/usr/lib --localstatedir=/var/lib 
--infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes --with-x=yes 
--with-x-toolkit=athena --without-gif'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: nil

Using Bash, create a binary file containing eight bytes in two lines:

        bash$ echo -n $'\001\002\003\n\001\002\003\n' > /tmp/bin

Double-check that the file contains what we think it does:

        bash$ od -c /tmp/bin

        you'll see 0000000 001 002 003  \n 001 002 003  \n

Start Emacs with -q --no-site-file.

Visit that file in Emacs:

        M-x find-file-literally RET /tmp/bin RET

Base64-encode it:

        C-x h M-x base64-encode-region RET

Put a carriage-return-linefeed pair at the end of the single line:

        M-> C-q C-m RET

Save the encoded version:

        C-x C-w bin.b64 RET

Revisit the file, thus setting the buffer to use the MS-DOS line
ending convention:

        C-x C-v RET

Base64-decode the file:

        C-x h M-x base64-decode-region

Save the decoded version to a different file for comparison with the

        C-x C-w bin.again RET

Now examine the newly-saved version with od back at the shell:

        od -c /tmp/bin.again 

        you'll now see 0000000 001 002 003  \r  \n 001 002 003  \r  \n

Thus the binary file has had some carriage-returns inserted into it,
which is a Bad Thing, since those carriage-returns were not present in
the encoded data.

RFC 2045 says both

        All line breaks or other characters not found in Table 1 must
        be ignored by decoding software.


        Any characters outside of the base64 alphabet are to be
        ignored in base64-encoded data.

If this is indeed a bug (as opposed to my misunderstanding how
base64-decode-region is supposed to work) then a possible fix would be
to have base64-decode-region, after it's done its work, do
(set-buffer-file-coding-system 'raw-text-unix) or something similar.

PGP Fingerprint: 3E7B A3F3 96CA 8958 ACC5  C8BD 6337 0041 C01C 5276

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