d83db3fb6a
You should not be using DES. You should not have been using DES for the
past 30 years.
The ed DES-CBC scheme lacked several desirable properties of a sealed
document system, even ignoring DES itself. In particular, it did not
provide the "integrity" cryptographic property (detection of tampering), and
it treated ASCII passwords as 64-bit keys (instead of using a KDF like
scrypt or PBKDF2).
Some general approaches ed(1) users might consider to replace the removed
DES mode:
1. Full disk encryption with something like AES-XTS. This is easy to
conceptualize, design, and implement, and it provides confidentiality for
data at rest. Like CBC, it lacks tampering protection. Examples include
GELI, LUKS, FileVault2.
2. Encrypted overlay ("stackable") filesystems (EncFS, PEFS?, CryptoFS,
others).
3. Native encryption at the filesystem layer. Ext4/F2FS, ZFS, APFS, and
NTFS all have some flavor of this.
4. Storing your files unencrypted. It's not like DES was doing you much
good.
If you have DES-CBC scrambled files produced by ed(1) prior to this change,
you may decrypt them with:
openssl des-cbc -d -iv 0 -K <key in hex> -in <inputfile> -out <plaintext>
Reviewed by: allanjude, bapt, emaste
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D17829
93 lines
3.7 KiB
Plaintext
93 lines
3.7 KiB
Plaintext
$FreeBSD$
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This version of ed(1) is not strictly POSIX compliant, as described in
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the POSIX 1003.2 document. The following is a summary of the omissions,
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extensions and possible deviations from POSIX 1003.2.
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OMISSIONS
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---------
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1) For backwards compatibility, the POSIX rule that says a range of
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addresses cannot be used where only a single address is expected has
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been relaxed.
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2) To support the BSD `s' command (see extension [1] below),
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substitution patterns cannot be delimited by numbers or the characters
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`r', `g' and `p'. In contrast, POSIX specifies any character expect
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space or newline can used as a delimiter.
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EXTENSIONS
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----------
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1) BSD commands have been implemented wherever they do not conflict with
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the POSIX standard. The BSD-ism's included are:
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i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution,
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ii) `W' for appending text to an existing file,
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iii) `wq' for exiting after a write,
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iv) `z' for scrolling through the buffer, and
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v) BSD line addressing syntax (i.e., `^' and `%') is recognized.
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2) The POSIX interactive global commands `G' and `V' are extended to
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support multiple commands, including `a', `i' and `c'. The command
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format is the same as for the global commands `g' and `v', i.e., one
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command per line with each line, except for the last, ending in a
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backslash (\).
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3) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is
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that <file> arguments are processed for backslash escapes, i.e., any
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character preceded by a backslash is interpreted literally. If the
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first unescaped character of a <file> argument is a bang (!), then the
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rest of the line is interpreted as a shell command, and no escape
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processing is performed by ed.
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4) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked
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as red. This limits editing of files in the local directory only and
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prohibits shell commands.
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DEVIATIONS
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----------
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1) Though ed is not a stream editor, it can be used to edit binary files.
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To assist in binary editing, when a file containing at least one ASCII
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NUL character is written, a newline is not appended if it did not
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already contain one upon reading. In particular, reading /dev/null
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prior to writing prevents appending a newline to a binary file.
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For example, to create a file with ed containing a single NUL character:
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$ ed file
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a
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^@
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.
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r /dev/null
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wq
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Similarly, to remove a newline from the end of binary `file':
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$ ed file
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r /dev/null
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wq
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2) Since the behavior of `u' (undo) within a `g' (global) command list is
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not specified by POSIX, it follows the behavior of the SunOS ed:
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undo forces a global command list to be executed only once, rather than
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for each line matching a global pattern. In addition, each instance of
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`u' within a global command undoes all previous commands (including
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undo's) in the command list. This seems the best way, since the
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alternatives are either too complicated to implement or too confusing
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to use.
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The global/undo combination is useful for masking errors that
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would otherwise cause a script to fail. For instance, an ed script
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to remove any occurrences of either `censor1' or `censor2' might be
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written as:
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ed - file <<EOF
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1g/.*/u\
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,s/censor1//g\
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,s/censor2//g
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...
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3) The `m' (move) command within a `g' command list also follows the SunOS
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ed implementation: any moved lines are removed from the global command's
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`active' list.
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4) If ed is invoked with a name argument prefixed by a bang (!), then the
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remainder of the argument is interpreted as a shell command. To invoke
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ed on a file whose name starts with bang, prefix the name with a
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backslash.
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