ctm_smail, ctm_dequeue, ctm_rmail -- send and receive ctm(1) deltas via
mail
ctm_smail [-l log] [-m maxmsgsize] [-c maxctmsize] [-q queue-dir]
ctm-delta mail-alias
ctm_dequeue [-l log] [-n numchunks] queue-dir
ctm_rmail [-Dfuv] [-l log] [-p piecedir] [-d deltadir] [-b basedir]
[file ...]
In conjunction with the ctm(1) command, ctm_smail, ctm_dequeue and
ctm_rmail are used to distribute changes to a source tree via email. The
ctm_smail utility is given a compressed ctm delta, and a mailing list to
send it to. It splits the delta into manageable pieces, encodes them as
mail messages and sends them to the mailing list (optionally queued to
spread the mail load). Each recipient uses ctm_rmail (either manually or
automatically) to decode and reassemble the delta, and optionally call
ctm to apply it to the source tree. At the moment, several source trees
are distributed, and by several sites. These include the FreeBSD-current
source and CVS trees, distributed by freefall.FreeBSD.org.
Command line arguments for ctm_smail:
-l log Instead of appearing on stderr, error diagnostics and informational
messages (other than command line errors) are time stamped
and written to the file log.
-m maxmsgsize
Limit the maximum size mail message that ctm_smail is allowed to
send. It is approximate since mail headers and other niceties
are not counted in this limit. If not specified, it will default
to 64000 bytes, leaving room for 1535 bytes of headers before the
rumoured 64k mail limit.
-c maxctmsize
Limit the maximum size delta that will be sent. Deltas bigger
that this limit will cause an apology mail message to be sent to
the mailing list. This is to prevent massive changes overwhelming
users' mail boxes. Note that this is the size before encoding.
Encoding causes a 4/3 size increase before mail headers are
added. If not specified, there is no limit.
-q queue-dir
Instead of mailing the delta pieces now, store them in the given
directory to be mailed later using ctm_dequeue. This feature
allows the mailing of large deltas to be spread out over hours or
even days to limit the impact on recipients with limited network
bandwidth or small mail spool areas.
ctm-delta is the delta to be sent, and mail-alias is the mailing list to
send the delta to. The mail messages are sent using sendmail(8).
Command line arguments for ctm_dequeue:
-l log Instead of appearing on stderr, error diagnostics and informational
messages (other than command line errors) are time stamped
and written to the file log.
-n numchunks
Limit the number of mail messages that ctm_dequeue will send per
run. By default, ctm_dequeue will send one mail message per run.
queuedir is the directory containing the mail messages stored by
ctm_smail. Up to numchunks mail messages will be sent in each run. The
recipient mailing list is already encoded in the queued files.
It is safe to run ctm_dequeue while ctm_smail is adding entries to the
queue, or even to run ctm_smail multiple times concurrently, but a separate
queue directory should be used for each tree being distributed.
This is because entries are served in alphabetical order, and one tree
will be unfairly serviced before any others, based on the delta names,
not delta creation times.
Command line arguments for ctm_rmail:
-l log Instead of appearing on stderr, error diagnostics and informational
messages (other than command line errors) are time stamped
and written to the file log.
-p piecedir
Collect pieces of deltas in this directory. Each piece corresponds
to a single mail message. Pieces are removed when complete
deltas are built. If this flag is not given, no input
files will be read, but completed deltas may still be applied
with ctm if the -b flag is given.
-d deltadir
Collect completed deltas in this directory. Deltas are built
from one or more pieces when all pieces are present.
-b basedir
Apply any completed deltas to this source tree. If this flag is
not given, deltas will be stored, but not applied. The user may
then apply the deltas manually, or by using ctm_rmail without the
-p flag. Deltas will not be applied if they do not match the
.ctm_status file in basedir (or if .ctm_status does not exist).
-D Delete deltas after successful application by ctm. It is probably
a good idea to avoid this flag (and keep all the deltas) as
ctm has the ability to recover small groups of files from a full
set of deltas.
-f Fork and execute in the background while applying deltas with
ctm. This is useful when automatically invoking ctm_rmail from
sendmail because ctm can take a very long time to complete, causing
other people's mail to be delayed, and can in theory cause
spurious mail retransmission due to the remote sendmail timing
out, or even termination of ctm_rmail by mail filters such as
MH's slocal. Don't worry about zillions of background ctm processes
loading your machine, since locking is used to prevent
more than one ctm invocation at a time.
-u Pass the -u flag to the ctm command when applying the complete
deltas, causing it to set the modification time of created and
modified files to the CTM delta creation time.
-v Pass the -v flag to the ctm command when applying the complete
deltas, causing a more informative output. All ctm output
appears in the ctm_rmail log file.
The file arguments (or stdin, if there are none) are scanned for delta
pieces. Multiple delta pieces can be read from a single file, so an
entire maildrop can be scanned and processed with a single command.
It is safe to invoke ctm_rmail multiple times concurrently (with different
input files), as might happen when sendmail is delivering mail asynchronously.
This is because locking is used to keep things orderly.
Following are the important parts of an actual (very small) delta piece:
From: owner-src-cur
To: src-cur
Subject: ctm-mail src-cur.0003.gz 1/4
CTM_MAIL BEGIN src-cur.0003.gz 1 4
H4sIAAAAAAACA3VU72/bNhD9bP0VByQoEiyRSZEUSQP9kKTeYCR2gDTdsGFAwB/HRogtG5K8NCj6
v4+UZSdtUQh6Rz0eee/xaF/dzx8up3/MFlDkBNrGnbttAwyo1pxoRgoiBNX/QJ5d3c9/X8DcPGGo
lggkPiXngE4W1gUjKPJCYyk5MZRbIqmNW/ASglIFcdwIzTUxaAqhnCPcBqloKEkJVNDMF0Azk+Bo
dDzzk0Ods/+A5gXv9YyJHjMCtJwQNeESNma7hOmXDRxn
CTM_MAIL END 61065
The subject of the message always begins with ``ctm-mail'' followed by
the name of the delta, which piece this is, and how many total pieces
there are. The data are bracketed by ``CTM_MAIL BEGIN'' and ``CTM_MAIL
END'' lines, duplicating the information in the subject line, plus a simple
checksum.
If the delta exceeds maxctmsize, then a message like this will be
received instead:
From: owner-src-cur
To: src-cur
Subject: ctm-notice src-cur.0999.gz
src-cur.0999.gz is 792843 bytes. The limit is 300000 bytes.
You can retrieve this delta via ftp.
You are then on your own!
To send delta 32 of src-cur to a group of wonderful code hackers known to
sendmail as src-guys, limiting the mail size to roughly 60000 bytes, you
could use:
ctm_smail -m 60000 /wherever/it/is/src-cur.0032.gz src-guys
To decode every ctm-mail message in your mailbox, assemble them into complete
deltas, then apply any deltas built or lying around, you could use:
ctm_rmail -p ~/pieces -d ~/deltas -b /usr/ctm-src-cur $MAIL
(Note that no messages are deleted by ctm_rmail. Any mail reader could
be used for that purpose.)
To create a mail alias called receiver-dude that will automatically
decode and assemble deltas, but not apply them, you could put the following
lines in your /etc/mail/aliases file (assuming the /ctm/tmp and
/ctm/deltas directories and /ctm/log file are writable by user daemon or
group wheel):
receiver-dude: "|ctm_rmail -p /ctm/tmp -d /ctm/deltas -l /ctm/log"
owner-receiver-dude: [email protected]e
The second line will catch failures and drop them into your regular mailbox,
or wherever else you like.
To apply all the deltas collected, and delete those applied, you could
use:
ctm_rmail -D -d /ctm/deltas -b /ctm/src-cur -l /ctm/apply.log
For maximum flexibility, consider this excerpt from a procmail script:
PATH=$HOME/bin:$PATH
:0 w
* ^Subject: ctm-mail cvs-cur
| ctm_incoming
together with the shell script ~/bin/ctm_incoming:
#! /bin/sh
PATH="$HOME/bin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin"
export PATH
cd $HOME/ctm && ctm_rmail -f -p pieces -d deltas -l log -b /ctm
which will deposit all ctm deltas in ~/ctm/deltas, apply them to the tree
in /ctm, and drop any failures into your regular mail box. Note the PATH
manipulation in ctm_incoming which allows ctm_rmail to execute ctm(1) on
the (non-FreeBSD) machine that this example was taken from.
On its own, CTM is an insecure protocol - there is no authentication performed
that the changes applied to the source code were sent by a trusted
party, and so care should be taken if the CTM deltas are obtained via an
unauthenticated medium such as regular email. It is a relatively simple
matter for an attacker to forge a CTM delta to replace or precede the
legitimate one and insert malicious code into your source tree. If the
legitimate delta is somehow prevented from arriving, this will go unnoticed
until a later delta attempts to touch the same file, at which point
the MD5 checksum will fail.
To remedy this insecurity, CTM delta pieces generated by FreeBSD.org are
cryptographically signed in a format compatible with the GNU Privacy
Guard utility, available in /usr/ports/security/gpg, and the Pretty Good
Privacy v5 utility, /usr/ports/security/pgp5. The relevant public key
can be obtained by fingering [email protected].
CTM deltas which are thus signed cannot be undetectably altered by an
attacker. Therefore it is recommended that you make use of GPG or PGP5
to verify the signatures if you receive your CTM deltas via email.
If deltas are to be applied then ctm(1) and gunzip(1) must be in your
PATH.
QUEUEDIR/*
Pieces of deltas encoded as mail messages waiting to be sent to
the mailing list.
PIECEDIR/*
Pieces of deltas waiting for the rest to arrive.
DELTADIR/*
Completed deltas.
BASEDIR/.ctm_status
File containing the name and number of the next delta to be
applied to this source tree.
The ctm_smail, ctm_dequeue and ctm_rmail utilities return exit status 0
for success, and 1 for various failures. The ctm_rmail utility is
expected to be called from a mail transfer program, and thus signals
failure only when the input mail message should be bounced (preferably
into your regular maildrop, not back to the sender). In short, failure
to apply a completed delta with ctm is not considered an error important
enough to bounce the mail, and ctm_rmail returns an exit status of 0.
In normal operation, ctm_smail will report messages like:
ctm_smail: src-cur.0250.gz 1/2 sent to src-guys
or, if queueing,
ctm_smail: src-cur.0250.gz 1/2 queued for src-guys
The ctm_dequeue utility will report messages like:
ctm_dequeue: src-cur.0250.gz 1/2 sent
The ctm_rmail utility will report messages like:
ctm_rmail: src-cur.0250.gz 1/2 stored
ctm_rmail: src-cur.0250.gz 2/2 stored
ctm_rmail: src-cur.0250.gz complete
If any of the input files do not contain a valid delta piece, ctm_rmail
will report:
ctm_rmail: message contains no delta
and return an exit status of 1. You can use this to redirect wayward
messages back into your real mailbox if your mail filter goes wonky.
These messages go to stderr or to the log file. Messages from ctm(1)
turn up here too. Error messages should be self explanatory.
ctm(1), ctm(5)
Stephen McKay <[email protected]>
FreeBSD 5.2.1 January 24, 1995 FreeBSD 5.2.1 [ Back ] |
